Sample records for vertical gradient freeze

  1. Vertical gradient freeze GaAs: Growth and electrical properties

    SciTech Connect

    Galiano, M.L.

    1989-05-01

    We have investigated the influence of silicon contamination prevention methods on the electrical properties of GaAs grown by the Vertical Gradient Freeze (VGF) technique. We report the effectiveness of these methods for GaAs crystals grown from two different starting materials: n-type with resistivities in the range of 10/sup /minus/1/ to 10/sup 3/ ..cap omega..-cm and semi-insulating (SI) with a resistivity of 10/sup 8/ ..cap omega..-cm. We have found that the impurities in the starting materials, specifically boron, carbon and silicon, have an effect on the ability to control silicon contamination with methods that have been reported previously in the literature. We also report the attainment of SI crystals using a PBN crucible, a SI charge and B/sub 2/O/sub 3/ encapsulation. 61 refs., 13 figs., 7 tabs.

  2. Vertical bridgman and gradient freeze growth of III-V compound semiconductors

    SciTech Connect

    Bourret, E.D.

    1990-07-01

    Major improvements in the structural and electrical perfection of single crystals of III-V compound semiconductors have been achieved by using new vertical Bridgman-type and vertical gradient freeze techniques. A general review of experimental set-ups used for growth of large diameter crystals of GaP, InP and GaAs is presented. Crystal properties and characteristic features are discussed to illustrate advantages and disadvantages of the vertical Bridgman-type growth techniques. 22 refs., 5 figs.

  3. Growth of 3? and 4? gallium arsenide crystals by the vertical gradient freeze (VGF) method

    NASA Astrophysics Data System (ADS)

    Birkmann, B.; Rasp, M.; Stenzenberger, J.; Müller, G.

    2000-04-01

    Results of the vertical gradient freeze (VGF) growth of Si-doped (3?) and semi-insulating (4?) GaAs crystals are shown. The VGF process conditions were optimised with the aid of numerical simulations using the so-called inverse modelling. Experimental results and predictions from the computer simulation (software CrysVUN++) are quantitatively compared with respect to the power versus time profiles of the heaters, and qualitatively with respect to the shapes of the solid-liquid interface and the growth rate.

  4. Growth and characterization of low defect GaAs by vertical gradient freeze

    NASA Astrophysics Data System (ADS)

    Abernathy, C. R.; Kinsella, A. P.; Jordan, A. S.; Caruso, R.; Pearton, S. J.; Temkin, H.; Wade, H.

    1987-11-01

    As the diameter of GaAs substrates has increased, so has the difficulty and cost of growing GaAs by the liquid encapsulated Czochralski (LEC) method. One alternative crystal growth method with offers promise is growth by vertical gradient freeze (VGF). This technique avoids the problems associated with diameter control during low gradient LEC growth. In this paper we discuss the growth of 2 inch diameter undoped and In-alloyed GaAs by VGF. Through the use of low gradients, undoped material with a dislocation density of (2-6) x 10 3 cm -2 has been obtained. With the addition of 0.6 at% InAs to the melt, this density is further reduced to 0-1000 cm -2. In contrast to standard LEC, GaAs grown by VGF shows low concentrations of the EL2 deep level and of the C shallow acceptor level. The material is semi-insulating ? ? 10 7 ? cm, and is thus suitable for device applications. From temperature dependent Hall measurements, the semi-insulating (SI) behavior is believed to be caused by Fermi level pinning at a defect with an energy level of ˜ 0.5 eV.

  5. Latest developments in vertical gradient freeze (VGF) technology: GaAs, InP, and GaP

    Microsoft Academic Search

    M Young; X Liu; D Zhang; M Zhu; X. Y Hu

    1999-01-01

    Vertical gradient freeze (VGF) technology grows III-V semiconductor single crystals with a low thermal gradient and in a thermal dynamically stable system. Such materials grown exhibit low dislocation density and low internal stress. VGF technology has reached the stage of commercial production of 6-in. GaAs, 3-in. InP, and 3-in. GaP. In this review, we present the latest developments of these

  6. Crystal Growth and Characterization of CdTe Grown by Vertical Gradient Freeze

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Lehoczky, S. L.; Raghothamachar, B.; Dudley, M.

    2007-01-01

    In this study, crystals of CdTe were grown from melts by the unseeded vertical gradient freeze method. The quality of grown crystal were studied by various characterization techniques including Synchrotron White Beam X-ray Topography (SWBXT), chemical analysis by glow discharge mass spectroscopy (GDMS), low temperature photoluminescence (PL), and Hall measurements. The SWBXT images from various angles show nearly strain-free grains, grains with inhomogeneous strains, as well as twinning nucleated in the shoulder region of the boule. The GDMS chemical analysis shows the contamination of Ga at a level of 3900 ppb, atomic. The low temperature PL measurement exhibits the characteristic emissions of a Ga-doped sample. The Hall measurements show a resistivity of 1 x l0(exp 7) ohm-cm at room temperature to 3 x 10(exp 9) ohm-cm at 78K with the respective hole and electron concentration of 1.7 x 10(exp 9) cm(exp -3) and 3.9 x 10(exp 7) cm(exp -3) at room temperature.

  7. Growth of 2? InP and GaAs crystals by the vertical gradient freeze (VGF) technique and characterization

    NASA Astrophysics Data System (ADS)

    Amon, J.; Zemke, D.; Hoffmann, B.; Müller, G.

    1996-09-01

    InP and GaAs crystals with a diameter of 2? were grown by the vertical gradient freeze (VGF) technique. It is demonstrated by electrical and optical investigations that the VGF technique allows the growth of crystals with a uniform distribution of the dopants in both a macroscopic and a microscopic scale. The etch pit density in the VGF grown crystals is reduced compared to LEC-grown ones. Numerical modelling was used to optimize thermal boundary conditions.

  8. Characterisation of vertical gradient freeze semi-insulating InP for use as a nuclear radiation detector

    Microsoft Academic Search

    H. El-Abbassi; S. Rath; P. J. Sellin

    2001-01-01

    The performance of a nuclear radiation detector fabricated from Vertical Gradient Freeze (VGF) semi-insulating Fe-doped InP was investigated. Pulse height spectra were acquired when the detector was irradiated with alpha particles from 241Am, as a function of temperature and detector bias voltage. The spectroscopic performance of the detector was limited at room temperature due to the presence of a high

  9. Computer-assisted growth of low-EPD GaAs with 3? diameter by the vertical gradient-freeze technique

    Microsoft Academic Search

    J. Amon; P Berwian; G Müller

    1999-01-01

    We have grown 3?, silicon-doped GaAs crystals with low dislocation density by the vertical gradient freeze (VGF) method. The thermal conditions in a newly designed, multi-zone VGF-furnace were optimized by the aid of numerical simulation. A computer controlled temperature-time program of the 9 heaters was acquired which allows to keep the axial temperature gradient in the solid (liquid) GaAs at

  10. Thermal stress theory of dislocation reduction in the vertical gradient freeze (VGF) growth of GaAs and InP

    NASA Astrophysics Data System (ADS)

    Jordan, A. S.; Monberg, E. M.; Clemans, J. E.

    1993-03-01

    We have developed the quasi-steady state heat transfer/thermal stress model for dislocation generation in the vertical gradient freeze growth (VGF) of GaAs and InP. Dislocation density contour maps for 2 to 4 inch diameter boules reveal a dramatic reduction in dislocation density for both compounds grown by VGF compared to the standard LEC process. For example, we have determined that for 3 inch diameter undoped GaAs grown by VGF the defect density at the edge of the wafer is reduced by at least a factor of six compared to undoped or even In-alloyed LEC material. The theoretical calculations are in satisfactory agreement with etch-pit density (EPD) data for both compunds. In particular, at a temperature gradient of -5 K/cm the calculated results track the EPD counts in both the <100> and <110> directions for 3 inch diameter undoped GaAs grown by the VGF technique.

  11. Final Report: Property Improvement in CZT via Modeling and Processing Innovations – Te-particles in vertical gradient freeze CZT: Size and Spatial Distributions and Constitutional Supercooling

    SciTech Connect

    Henager, Charles H.; Alvine, Kyle J.; Bliss, Mary; Riley, Brian J.; Stave, Jean A.

    2014-10-01

    A section of a vertical gradient freeze CZT boule approximately 2100-mm3 with a planar area of 300-mm2 was prepared and examined using transmitted IR microscopy at various magnifications to determine the three-dimensional spatial and size distributions of Te-particles over large longitudinal and radial length scales. The boule section was approximately 50-mm wide by 60-mm in length by 7-mm thick and was doubly polished for TIR work. Te-particles were imaged through the thickness using extended focal imaging to locate the particles in thickness planes spaced 15-µm apart and then in plane of the image using xy-coordinates of the particle center of mass so that a true three dimensional particle map was assembled for a 1-mm by 45-mm longitudinal strip and for a 1-mm by 50-mm radial strip. Te-particle density distributions were determined as a function of longitudinal and radial positions in these strips, and treating the particles as vertices of a network created a 3D image of the particle spatial distribution. Te-particles exhibited a multi-modal log-normal size density distribution that indicated a slight preference for increasing size with longitudinal growth time, while showing a pronounced cellular network structure throughout the boule that can be correlated to dislocation network sizes in CZT. Higher magnification images revealed a typical Rayleigh-instability pearl string morphology with large and small satellite droplets. This study includes solidification experiments in small crucibles of 30:70 mixtures of Cd:Te to reduce the melting point below 1273 K (1000?C). These solidification experiments were performed over a wide range of cooling rates and clearly demonstrated a growth instability with Te-particle capture that is suggested to be responsible for one of the peaks in the size distribution using size discrimination visualization. The results are discussed with regard to a manifold Te-particle genesis history as 1) Te-particle direct capture from melt-solid growth instabilities, 2) Te-particle formation from dislocation core diffusion and the formation and breakup of Te-tubes, and 3) Te-particle formation due to classical nucleation and growth as precipitates.

  12. Measuring the vertical gradient of gravity

    NSDL National Science Digital Library

    Rob Sternberg

    The free-air effect tells us that as elevation above sea level increases, gravitational acceleration g decreases at the rate of about 0.3086 mgal/meter. This effect is routinely corrected for when making gravity surveys. We will use the LaCoste & Romberg gravimeter to measure the free-air effect in a tall building on campus, and compare with the theoretical value. keywords: gravity; vertical gradient; gravimeter

  13. A convex gradient coil design for vertical field open MRI

    Microsoft Academic Search

    S. Y. Lee; M. H. Cho; C. H. Moon; H. W. Park

    2000-01-01

    We introduce a convex gradient coil that can be used for interventional studies using a vertical field open MRI system. By placing gradient coil wires on two coaxial convex surfaces seeing each other, we can improve the accessibility to the patient during the scan, while maintaining the space for imaging. We have defined convex surfaces on hyperboloids at the prolate

  14. European deciduous trees exhibit similar safety margins against damage by spring freeze events along elevational gradients.

    PubMed

    Lenz, Armando; Hoch, Günter; Vitasse, Yann; Körner, Christian

    2013-12-01

    Minimum temperature is assumed to be an important driver of tree species range limits. We investigated during which period of the year trees are most vulnerable to freezing damage and whether the pressure of freezing events increases with increasing elevation. We assessed the course of freezing resistance of buds and leaves from winter to summer at the upper elevational limits of eight deciduous tree species in the Swiss Alps. By reconstructing the spring phenology of these species over the last eight decades using a thermal time model, we linked freezing resistance with long-term minimum temperature data along elevational gradients. Counter-intuitively, the pressure of freeze events does not increase with elevation, but deciduous temperate tree species exhibit a constant safety margin (5-8.5 K) against damage by spring freeze events along elevational gradients, as a result of the later flushing at higher elevation. Absolute minimum temperatures in winter and summer are unlikely to critically injure trees. Our study shows that freezing temperatures in spring are the main selective pressure controlling the timing of flushing, leading to a shorter growing season at higher elevation and potentially driving species distribution limits. Such mechanistic knowledge is important to improve predictions of tree species range limits. PMID:23952607

  15. Airship stresses due to vertical velocity gradients and atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Sheldon, D.

    1975-01-01

    Munk's potential flow method is used to calculate the resultant moment experienced by an ellipsoidal airship. This method is first used to calculate the moment arising from basic maneuvers considered by early designers, and then expended to calculate the moment arising from vertical velocity gradients and atmospheric turbulence. This resultant moment must be neutralized by the transverse force of the fins. The results show that vertical velocity gradients at a height of 6000 feet in thunderstorms produce a resultant moment approximately three to four times greater than the moment produced in still air by realistic values of pitch angle or steady turning. Realistic values of atmospheric turbulence produce a moment which is significantly less than the moment produced by maneuvers in still air.

  16. Crystal Growth of CdTe by Gradient Freeze in Universal Multizone Crystallizator (UMC)

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Lehoczky, S. L.; Li, C.; Knuteson, D.; Raghothamachar, B.; Dudley, M.; Szoke, J.; Barczy, P.

    2004-01-01

    In the case of unsealed melt growth of an array of II-VI compounds, namely, CdTe, CdZnTe and ZnSe, there is a tremendous amount of experimental data describing the correlations between melt conditions and crystal quality. The results imply that the crystallinity quality can be improved if the melt was markedly superheated or long-time held before growth. It is speculated that after high superheating the associated complex dissociate and the spontaneous nucleation is retarded. In this study, crystals of CdTe were grown from melts which have undergone different thermal history by the unseeded gradient freeze method using the Universal Multizone Crystallizator (UMC). The effects of melt conditions on the quality of grown crystal were studied by various characterization techniques, including Synchrotron White Beam X-ray Topography (SWSXT), infrared microscopy, chemical analysis by glow discharge mass spectroscopy (GDMS), electrical conductivity and Hall measurements.

  17. Design of convex-surface gradient coils for a vertical-field open MRI system

    Microsoft Academic Search

    C H Moon; H W Park; M H Cho; S Y Lee

    2000-01-01

    Open MRI systems usually use vertical-field magnets because interventional studies can be performed more conveniently with them. In this paper, we have designed convex-surface gradient coils for a vertical-field open MRI system. To obtain stronger gradient field strength with a smaller coil inductance while maintaining enough space for interventional operations, we have designed gradient coils on convex, rather than planar,

  18. On crucible effects during the growth of cadmium zinc telluride in an electrodynamic gradient freeze furnace

    SciTech Connect

    Gasperino, David; Bliss, Mary; Jones, Kelly A.; Lynn, Kelvin G.; Derby, Jeffrey

    2009-01-04

    The CrysMAS code of the Crystal Growth Laboratory, Fraunhofer IISB, is applied to reveal conditions occurring in electrodynamic gradient freeze furnaces during the growth of cadmium zinc telluride crystals. Of particular interest are heat transfer and growth conditions associated with crucibles of different design, one constructed of graphite and the other of pyrolytic boron nitride (PBN). Under identical furnace set-point schedules, the PBN system exhibits very different heat transfer through the cone region of the crucible, resulting in steeper axial thermal profiles and convex solid-interface shapes (rather than the concave shapes computed for the graphite crucible). Both systems exhibit a concave interface during growth through the cylindrical part of the crucible; however, the axial thermal profile through the contents of the graphite crucible is considerably more offset from the set-point profile of the furnace due to the large axial flows of heat through the crucible walls. These conditions argue for advantage to the PBN system; however, comparatively larger radial gradients in the PBN system could lead to higher dislocation levels.

  19. On crucible effects during the growth of cadmium zinc telluride in an electrodynamic gradient freeze furnace

    NASA Astrophysics Data System (ADS)

    Gasperino, David; Bliss, Mary; Jones, Kelly; Lynn, Kelvin; Derby, Jeffrey J.

    2009-04-01

    The CrysMAS code of the Crystal Growth Laboratory, Fraunhofer IISB, is applied to reveal conditions occurring in electrodynamic gradient freeze furnaces during the growth of cadmium zinc telluride crystals. Of particular interest are heat transfer and growth conditions associated with crucibles of different design, one constructed of graphite and the other of pyrolytic boron nitride (PBN). Under identical furnace set-point schedules, the two systems exhibit very different behaviors. Specifically, the temperature field through the cone region of the PBN crucible displays much steeper axial thermal profiles and promotes convex solid-liquid interface shapes (rather than the concave shapes computed for the graphite crucible). Both systems exhibit a concave interface during growth through the cylindrical part of the crucible. However, the axial thermal profile through the graphite-crucible charge is considerably more offset from the set-point profile of the furnace due to significant axial heat flows through the crucible walls. These factors argue in favor of the PBN crucible; however, comparatively larger radial gradients in the PBN system could lead to higher dislocation levels.

  20. Ecophysiological responses of black walnut (Juglans nigra) to plantation thinning along a vertical canopy gradient

    E-print Network

    Ecophysiological responses of black walnut (Juglans nigra) to plantation thinning along a vertical Lafayette, IN 47907-2061, USA 1. Introduction Black walnut (Juglans nigra L.) is generally associated S T R A C T Ecophysiology of black walnut (Juglans nigra L.) along a vertical canopy gradient

  1. Bulk Crystal Growth of Piezoelectric PMN-PT Crystals Using Gradient Freeze Technique for Improved SHM Sensors

    NASA Technical Reports Server (NTRS)

    Aggarwal, Mohan D.; Kochary, F.; Penn, Benjamin G.; Miller, Jim

    2007-01-01

    There has been a growing interest in recent years in lead based perovskite ferroelectric and relaxor ferroelectric solid solutions because of their excellent dielectric, piezoelectric and electrostrictive properties that make them very attractive for various sensing, actuating and structural health monitoring (SHM) applications. We are interested in the development of highly sensitive and efficient PMN-PT sensors based on large single crystals for the structural health monitoring of composite materials that may be used in future spacecrafts. Highly sensitive sensors are needed for detection of defects in these materials because they often tend to fail by distributed and interacting damage modes and much of the damage occurs beneath the top surface of the laminate and not detectable by visual inspection. Research is being carried out for various combinations of solid solutions for PMN-PT piezoelectric materials and bigger size crystals are being sought for improved sensor applications. Single crystals of this material are of interest for sensor applications because of their high piezoelectric coefficient (d33 greater than 1700 pC/N) and electromechanical coefficients (k33 greater than 0.90). For comparison, the commonly used piezoelectric ceramic lead zirconate titanate (PZT) has a d33 of about 600 pC/N and electromechanical coefficients k33 of about 0.75. At the present time, these piezoelectric relaxor crystals are grown by high temperature flux growth method and the size of these crystals are rather small (3x4x5 mm(exp 3). In the present paper, we have attempted to grow bulk single crystals of PMN-PT in a 2 inch diameter platinum crucible and successfully grown a large size crystal of 67%PMN-33%PT using the vertical gradient freeze technique with no flux. Piezoelectric properties of the grown crystals are investigated. PMN-PT plates show excellent piezoelectric properties. Samples were poled under an applied electric field of 5 kV/cm. Dielectric properties at a frequency of 1 kHz are examined. The grown PMN-PT crystals show typical relaxor dielectric properties. Additionally, the thermal properties of the sample are tested. The results are in good agreement with those found in the literature and some are reported for the first time.

  2. Importance of closely spaced vertical sampling in delineating chemical and microbiological gradients in groundwater studies

    USGS Publications Warehouse

    Smith, R.L.; Harvey, R.W.; LeBlanc, D.R.

    1991-01-01

    Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, U.S.A. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in groundwater studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, USA. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in ground-water studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.

  3. Nonlinear Rock + Overburden Stress = Linear Anisotropy + Vertical Velocity Gradient

    NASA Astrophysics Data System (ADS)

    Korneev, V. A.

    2013-12-01

    The increase in seismic velocity with depth is a common property of rock, one that can be encountered practically everywhere. Overburden pressure increases vertical stress, producing nonlinear elastic responses. Application of nonlinear theory to this problem leads to transverse isotropy, with relatively simple relationships between the nonlinear constants and anisotropy elastic coefficients. These relationships can be used in velocity 'depth trend' removal and in computing offset-dependent corrections for stacking and migration. This also implies that realistic tomography models should account for elastic anisotropy as a basic feature. A proper solution for overburden stress requires a full nonlinear solution for static stress distribution. It is quite likely that anisotropy resulting from overburden pressure is a common, basic property of underground rock. Accounting for anisotropy properties requires more complex computational and imaging tools than just isotropic models, which have generally been in use up to the present. On the other hand, seismic interpretation can arrive at additional imaging rock parameters (TOE constants), which can potentially be extracted from anisotropy measurements. Additionally, the overburden-induced anisotropy is strong enough to produce shear waves by an explosion.

  4. A wet/wet differential pressure sensor for measuring vertical hydraulic gradient.

    PubMed

    Fritz, Brad G; Mackley, Rob D

    2010-01-01

    Vertical hydraulic gradient is commonly measured in rivers, lakes, and streams for studies of groundwater-surface water interaction. While a number of methods with subtle differences have been applied, these methods can generally be separated into two categories; measuring surface water elevation and pressure in the subsurface separately or making direct measurements of the head difference with a manometer. Making separate head measurements allows for the use of electronic pressure sensors, providing large datasets that are particularly useful when the vertical hydraulic gradient fluctuates over time. On the other hand, using a manometer-based method provides an easier and more rapid measurement with a simpler computation to calculate the vertical hydraulic gradient. In this study, we evaluated a wet/wet differential pressure sensor for use in measuring vertical hydraulic gradient. This approach combines the advantage of high-temporal frequency measurements obtained with instrumented piezometers with the simplicity and reduced potential for human-induced error obtained with a manometer board method. Our results showed that the wet/wet differential pressure sensor provided results comparable to more traditional methods, making it an acceptable method for future use. PMID:19664046

  5. Vertical gradient correction for the oceanographic Atlas of the East Asian Seas

    NASA Astrophysics Data System (ADS)

    Chang, You-Soon; Shin, Hong-Ryeol

    2014-08-01

    Regional climatology around the East Asian Seas has been developed by an international collaboration between the National Oceanic Data Center and the Korea Oceanic Data Center. It provides reliable information on temperature and salinity climatological fields with high resolution (0.1° × 0.1° by 137 levels). However, there is a problem around near-bottom areas where topographic change is steep and observations are not available near the bottom. This study resolves this problem using a vertical gradient correction method when the profile is statically unstable. The stability is determined based on the Brunt-Väisälä frequency with individual temperature and salinity profiles. Topographic-following mapping technique employing the potential vorticity constraint term is used to construct a vertical gradient database for the temperature and salinity at every grid point. The results show that the correction is effective for eliminating large erroneous vertical gradients around near-bottom areas. In addition, we show the importance of the optimal length scale to construct a precise vertical gradient database in a particular area such as the northern shelf of Taiwan. We expect that our revised high-resolution climatological mean fields will serve as important data for relevant studies around the East Asian Seas.

  6. DESIGN NOTE: Design of convex-surface gradient coils for a vertical-field open MRI system

    Microsoft Academic Search

    C. H. Moon; H. W. Park; M. H. Cho; S. Y. Lee

    2000-01-01

    Open MRI systems usually use vertical-field magnets because interventional studies can be performed more conveniently with them. In this paper, we have designed convex-surface gradient coils for a vertical-field open MRI system. To obtain stronger gradient field strength with a smaller coil inductance while maintaining enough space for interventional operations, we have designed gradient coils on convex, rather than planar,

  7. Vertical gradients in the zonal wind observed in the equatorial F-region under postsunset conditions

    NASA Astrophysics Data System (ADS)

    Kiene, A.; Larsen, M. F.; Kudeki, E.

    2014-12-01

    In the early evening sector of the F region near the geomagnetic equator, an eastward pressure gradient as the sun sets reorients the neutral flow toward the east, typically occurring within one hour of local sunset. Very few vertically-resolved measurements of this effect exist. We present recent in-situ chemical tracer results from the EVEX campaign, as well as results from the earlier Guara campaign, that show strong vertical shear in the zonal wind during sunset hours in the F region, up to a 150 m/s westward shift over 60 km altitude. Eastward F-region neutral winds near the geomagnetic equator drive vertical Pedersen currents at sunset that, in turn, drive the prereversal enhancement (PRE) of the eastward electric field in the equatorial F-region that is thought to be a primary driver of equatorial spread-F. Studies of the neutral winds relating to the PRE have been primarily focused on the winds observed from ground-based interferometry and from satellite accelerometer data, techniques which generally lack vertical resolution. We show that eastward winds at one altitude are not necessarily accompanied by eastward winds at higher altitudes, i.e., that the forces that drive the neutral wind are not constant with altitude at sunset. At sunset, solar heating varies significantly with altitude, decreasing at lower altitudes first, which would create a thermal pressure gradient with a similar vertical profile to that observed in the neutral winds. We discuss the magnitude of this effect as well as other factors that could contribute to the observed vertical gradients. We then apply these effects to typical ionospheric conditions at the time of the experiments and examine the resulting neutral forcing in relation to the observed wind profiles.

  8. Growth of CsI:Tl crystals in carbon coated silica crucibles by the gradient freeze technique

    NASA Astrophysics Data System (ADS)

    Singh, S. G.; Desai, D. G.; Singh, A. K.; Tyagi, M.; Sen, Shashwati; Sinha, A. K.; Gadkari, S. C.; Gupta, S. K.

    2012-07-01

    Single crystals of CsI having different Tl concentrations have been grown by a gradient freeze technique. Carbon films were deposited on the inside surface of fused silica crucibles to avoid sticking of the grown crystals. The crystals could be extracted easily from the crucibles without involving the inversion process at higher temperatures. Effects of varying growth parameters and after-growth thermal treatment on crystal properties like daylight coloration and radiation hardness were studied. Characterization techniques including high resolution X-ray diffraction, induced absorption, photoluminescence, afterglow and thermally stimulated luminescence were employed to evaluate the grown crystals. Gamma-ray detectors were fabricated using the grown crystals that showed good linearity and nearly 7.5% resolution at 662 keV. This established a very simple and low cost method to grow small to medium size (35 mm in diameter and 25 mm in length) CsI crystals for various applications.

  9. Particle surface area dependence of mineral dust in immersion freezing mode: investigations with freely suspended drops in an acoustic levitator and a vertical wind tunnel

    NASA Astrophysics Data System (ADS)

    Diehl, K.; Debertshäuser, M.; Eppers, O.; Schmithüsen, H.; Mitra, S. K.; Borrmann, S.

    2014-11-01

    The heterogeneous freezing temperatures of supercooled drops were measured using an acoustic levitator. This technique allows one to freely suspend single drops in the air without any wall contact. Heterogeneous nucleation by two types of illite (illite IMt1 and illite NX) and a montmorillonite sample was investigated in the immersion mode. Drops of 1 mm in radius were monitored by a video camera while cooled down to -28 °C to simulate freezing within the tropospheric temperature range. The surface temperature of the drops was contact-free, determined with an infrared thermometer; the onset of freezing was indicated by a sudden increase of the drop surface temperature. For comparison, measurements with one particle type (illite NX) were additionally performed in the Mainz vertical wind tunnel with drops of 340 ?m radius freely suspended. Immersion freezing was observed in a temperature range between -13 and -26 °C as a function of particle type and particle surface area immersed in the drops. Isothermal experiments in the wind tunnel indicated that after the cooling stage freezing still proceeds, at least during the investigated time period of 30 s. The results were evaluated by applying two descriptions of heterogeneous freezing, the stochastic and the singular model. Although the wind tunnel results do not support the time-independence of the freezing process both models are applicable for comparing the results from the two experimental techniques.

  10. Vertical distribution of larval stages of the horn fly, Haematobia irritans irritans (L.), in relation to manure pat temperature gradients 

    E-print Network

    March, Philip Anderson

    1981-01-01

    VERTICAL DISTRISUTION OF LARVAL STAGES OF THE HORN FLY, HAEMATOBIA IRRITANS IRRITANS (L. ), IN RELATION TO MANURE PAT TEMPERATURE GRADIENTS A Thesis by PHILIP ANDERSON MARCH Submitted to the Graduate College of Texas AijM University... in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1981 Major Subject: Entomology VERTICAL DISTRIBUTION OF LARVAL STAGES OF THE HORN FLY, HAEMATOBIA IRRITANS IRRITANS (L. ), IN RELATION TO MANURE PAT TEMPERATURE GRADIENTS...

  11. Vertical distribution of zooplankton in subalpine and alpine lakes: Ultraviolet radiation, fish predation, and the transparency-gradient hypothesis

    Microsoft Academic Search

    Kirsten Kessler; Ryan S. Lockwood; Craig E. Williamson; Jasmine E. Saros

    2008-01-01

    The transparency-gradient hypothesis argues that ultraviolet radiation (UV) is a primary determinant of the vertical distribution of zooplankton in transparent lakes with fewer fish, while fish predation is the primary driver in less transparent lakes where fish are more abundant. We measured vertical profiles of UV, photosynthetically active radiation (PAR, essentially visible light used as a proxy for fish predation),

  12. Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction

    SciTech Connect

    Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)

    2009-10-29

    We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)

  13. Detrimental Effects of Natural Vertical Head Gradients on Chemical and Water Level Measurements in Observation Wells: Identification and Control

    SciTech Connect

    Flach, G.P.

    2002-12-19

    It is well known that vertical head gradients exist in natural aquifer systems, and borehole flowmeter data have shown that such gradients commonly set up spontaneous vertical flows in monitoring wells, often called ambient flows. What has not been fully appreciated until recently is the serious detrimental effects such flows can have on solute concentration and hydraulic head measurements in monitoring wells. This communication explores the possibilities of diminishing ambient flows by increasing the hydraulic resistance to vertical flow within monitoring wells and limiting the penetration of such wells. Analyzed also are the surprising effects that vertical gradients may have on the equilibrium water level in a monitoring well. Results are based on collected data, numerical flow simulations, and hydraulic analysis in the near-well vicinity.

  14. A SPATIALLY RESOLVED VERTICAL TEMPERATURE GRADIENT IN THE HD 163296 DISK

    SciTech Connect

    Rosenfeld, Katherine A.; Andrews, Sean M.; Wilner, David J.; Qi, Chunhua [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hughes, A. Meredith [Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States)

    2013-09-01

    We analyze sensitive, sub-arcsecond resolution ALMA science verification observations of CO emission lines in the protoplanetary disk hosted by the young, isolated Ae star HD 163296. The observed spatial morphology of the {sup 12}CO J = 3-2 emission line is asymmetric across the major axis of the disk; the {sup 12}CO J = 2-1 line features a much less pronounced, but similar, asymmetry. The J = 2-1 emission from {sup 12}CO and its main isotopologues have no resolved spatial asymmetry. We associate this behavior with the direct signature of a vertical temperature gradient and layered molecular structure in the disk. This is demonstrated using both toy models and more sophisticated calculations assuming non-local thermodynamic equilibrium conditions. A model disk structure is developed to reproduce both the distinctive spatial morphology of the {sup 12}CO J = 3-2 line as well as the J = 2-1 emission from the CO isotopologues assuming relative abundances consistent with the interstellar medium. This model disk structure has {tau} = 1 emitting surfaces for the {sup 12}CO emission lines that make an angle of {approx}15 Degree-Sign with respect to the disk midplane. Furthermore, we show that the spatial and spectral sensitivity of these data can distinguish between models that have sub-Keplerian gas velocities due to the vertical extent of the disk and its associated radial pressure gradient (a fractional difference in the bulk gas velocity field of {approx}> 5%)

  15. Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies.

    PubMed

    Färber, Leonie; Sølhaug, Knut Asbjorn; Esseen, Per-Anders; Bilger, Wolfgang; Gauslaa, Yngvar

    2014-06-01

    Pendulous lichens dominate canopies of boreal forests, with dark Bryoria species in the upper canopy vs. light Alectoria and Usnea species in lower canopy. These genera offer important ecosystem services such as winter forage for reindeer and caribou. The mechanism behind this niche separation is poorly understood. We tested the hypothesis that species-specific sunscreening fungal pigments protect underlying symbiotic algae differently against high light, and thus shape the vertical canopy gradient of epiphytes. Three pale species with the reflecting pigment usnic acid (Alectoria sarmentosa, Usnea dasypoga, U. longissima) and three with dark, absorbing melanins (Bryoria capillaris, B. fremontii, B. fuscescens) were compared. We subjected the lichens to desiccation stress with and without light, and assessed their performance with chlorophyll fluorescence. Desiccation alone only affected U. longissima. By contrast, light in combination with desiccation caused photoinhibitory damage in all species. Usnic lichens were significantly more susceptible to light during desiccation than melanic ones. Thus, melanin is a more efficient light-screening pigment than usnic acid. Thereby, the vertical gradient of pendulous lichens in forest canopies is consistent with a shift in type and functioning of sunscreening pigments, from high-light-tolerant Bryoria in the upper to susceptible Alectoria and Usnea in the lower canopy. PMID:25039211

  16. The effect of a vertical temperature gradient in the lithosphere on seismic and tectonic waves

    NASA Astrophysics Data System (ADS)

    Birger, B. I.

    2008-09-01

    A linear analysis of the stability of the lithosphere considered as a viscoelastic layer with an equilibrium vertical gradient of temperature is carried out. The problem is solved with a complete system of linearized equations of a continuous medium represented in the dimensionless form and containing a set of dimensionless parameters that determine thermomechanical properties of the lithosphere. As a result of the stability analysis, decrements are found that give the time dependence of perturbations and correspond to high-frequency seismic waves and low-frequency tectonic waves. The frequency and velocity of seismic waves are determined by the elasticity and inertial properties of the lithosphere, and their attenuation, by viscous properties of the lithosphere. The temperature gradient existing in the lithosphere influences seismic waves very weakly. On the contrary, the pattern of tectonic waves is controlled by the temperature gradient and viscous properties, while the effect of elastic and inertial properties on these waves is negligibly small. The stability of a viscoelastic lithosphere is examined using such rheological models as the Maxwell, standard linear, and Andrade media (the frequency of tectonic waves is zero in the Maxwell medium).

  17. Detrimental effects of natural vertical head gradients on chemical and water level measurements in observation wells: identification and control

    NASA Astrophysics Data System (ADS)

    Elçi, Alper; Flach, Gregory P.; Molz, Fred J.

    2003-09-01

    It is well known that vertical head gradients exist in natural aquifer systems, and borehole flowmeter data have shown that such gradients commonly set up spontaneous vertical flows in monitoring wells, often called ambient flows. What has not been fully appreciated until recently is the serious detrimental effects such flows can have on solute concentration [Ground Water 39 (2001) 853] and hydraulic head measurements in monitoring wells. This communication explores the possibilities of diminishing ambient flows by increasing the hydraulic resistance to vertical flow within monitoring wells and limiting the penetration of such wells. Analyzed also are the surprising effects that vertical gradients may have on the equilibrium water level in a monitoring well. Results are based on collected data, numerical flow simulations, and hydraulic analysis in the near-well vicinity. Raising wellbore hydraulic resistance is of increasing importance and impact in thicker aquifers with higher horizontal hydraulic conductivities ( Kh). A systematic analysis of screen penetration revealed that the reduction of ambient flow also depends on aquifer thickness. On a first order basis, the results for homogeneous aquifers may be used to estimate the behavior of a heterogeneous aquifer by computing a power-law average of the heterogeneous Kh( z). Finally, it is evident from the analysis of vertical gradients on well water levels that in the presence of sufficiently high gradients (? h/? z>0.5) it is physically possible for a well screen to be fully submerged below the water table, and yet have an internal water level below the top of the screen. Contrary to common perceptions, water levels in wells spanning the water table deviate significantly from the elevation of the formation water table when the local vertical gradient exceeds about 0.1.

  18. Numerical simulation of supercritical heat transfer under severe axial density gradient in a narrow vertical tube

    SciTech Connect

    Bae, Y. Y.; Hong, S. D.; Kim, Y. W. [Korea Atomic Energy Research Inst., 1045 Daedeokdaero, Daejeon (Korea, Republic of)

    2012-07-01

    A number of computational works have been performed so far for the simulation of heat transfer in a supercritical fluid. The simulations, however, faced a lot of difficulties when heat transfer deteriorates due either to buoyancy or by acceleration. When the bulk temperature approaches the pseudo-critical temperature the fluid experiences a severe axial density gradient on top of a severe radial one. Earlier numerical calculations showed, without exception, unrealistic over-predictions, as soon as the bulk temperature exceeded the pseudo-critical temperature. The over-predictions might have been resulted from an inapplicability of widely-used turbulence models. One of the major causes for the difficulties may probably be an assumption of a constant turbulent Prandtl number. Recent research, both numerical and experimental, indicates that the turbulent Prandtl number is never a constant when the gradient of physical properties is significant. This paper describes the applicability of a variable turbulent Prandtl number to the numerical simulation of heat transfer in supercritical fluids flowing in narrow vertical tubes. (authors)

  19. Redefining cooling rate in terms of ice front velocity and thermal gradient: first evidence of relevance to freezing injury of lymphocytes.

    PubMed

    Beckmann, J; Körber, C; Rau, G; Hubel, A; Cravalho, E G

    1990-06-01

    A freezing process and the resulting injury or survival of biological cells is commonly characterized in terms of the cooling rate, B. Under certain circumstances, the cooling rate can be expressed as B = G.v, where G denotes the thermal gradient at the ice-liquid interface and v its velocity, respectively. To determine the influence of G and v on the morphology of the ice-liquid interface and on cell survival, a gradient freezing stage was designed. Flat capillaries could be pushed with constant velocity from a warm to a cold heat reservoir. With this setup both parameters, G and v, are independently adjustable and the resulting process of directional solidification can be observed dynamically in a light microscope. Human lymphocytes in phosphate-buffered saline with 10 vol% of dimethyl sulfoxide were used as biological test material. Viability was assessed by a membrane integrity test with fluorescein diacetate and ethidium bromide. All cells were cooled down to a final temperature of -196 degrees C and then rapidly thawed. The results obtained with this technique show that the viability determined after freezing and thawing with a certain cooling rate, B = G.v, may vary considerably depending on the imposed values of the thermal gradient, G, and the ice front velocity, v. In addition, the data seem to suggest that, first, the maximum viability which can be reached is governed by the cooling rate, and, second, this maximum for a given cooling rate could be achieved by establishing small temperature gradients and high interface velocities (about 30 degrees K/cm and 500 microns/sec, respectively, for the range of values of G and v tested). PMID:2379414

  20. AMMONIA AND HYDROGEN SULFIDE FLUX AND DRY DEPOSITION VELOCITY ESTIMATES USING VERTICAL GRADIENT METHOD AT A COMMERCIAL BEEF CATTLE FEEDLOT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonia and hydrogen sulfide flux and dry deposition velocity were estimated using micrometeorological vertical gradient flux method at a commercial cattle feedyard of approximately 50,000 head of beef cattle and average 14.4 m2/head (150 ft2/head) stocking density. During summertime, NH3-N emission...

  1. The mean curvature of the external equipotential surface and the vertical gravity gradient as functions of stokes's constants

    Microsoft Academic Search

    Milan Bursa; Jan Pícha

    1973-01-01

    Summary The mean curvature of the equipotential surface and the vertical gradient of gravity are expressed in terms of a development into a series of spherical harmonics [1, 2, 4], neglecting terms of the order of 10-8. The curvature anomalies have been computed using the satellite data [3]. The symbols used are the same as in [5].

  2. Simulation of vertical concentration gradient of influenza viruses in dust resuspended by walking.

    PubMed

    Khare, P; Marr, L C

    2015-08-01

    Particles are resuspended from the floor by walking and are subject to turbulent transport in the human aerodynamic wake. These processes may generate a vertical concentration gradient of particles. To estimate the magnitude of turbulence generated by walking, we measured the velocity field in the wake from floor to ceiling at 10-cm intervals with a sonic anemometer. The resulting eddy diffusion coefficients varied between 0.06 and 0.20 m(2) /s and were maximal at ~0.75-1 m above the floor, approximately the height of the swinging hand. We applied the eddy diffusion coefficients in an atmospheric transport model to predict concentrations of resuspended influenza virus as a function of the carrier particle size, height in the room, and relative humidity, which affects the resuspension rate coefficient and virus viability. Results indicated that the concentration of resuspended viruses at 1 m above the floor was up to 40% higher than at 2 m, depending on particle size. For exposure to total resuspended viruses, the difference at 1 vs. 2 m was 11-14%. It is possible that shorter people are exposed to higher concentrations of resuspended dust, including pathogens, although experimental evidence is needed to verify this proposition. PMID:25208212

  3. Generation of vertical-horizontal and horizontal-horizontal gravity gradients using stochastically modified integral estimators

    NASA Astrophysics Data System (ADS)

    Eshagh, Mehdi; Romeshkani, Mohsen

    2011-10-01

    The Earth's gravity field modelling is an ill-posed problem having a sensitive solution to the error of data. Satellite gravity gradiometry (SGG) is a space technique to measure the second-order derivatives of geopotential for modelling this field, but the measurements should be validated prior to use. The existing terrestrial gravity anomalies and Earth gravity models can be used for this purpose. In this paper, the second-order vertical-horizontal (VH) and horizontal-horizontal (HH) derivatives of the extended Stokes formula in the local north-oriented frame are modified using biased, unbiased and optimum types of least-squares modification. These modified integral estimators are used to generate the VH and HH gradients at 250 km level for validation purpose of the SGG data. It is shown that, unlike the integral estimator for generating the second-order radial derivative of geopotential, the system of equations from which the modification parameters are obtained is unstable for all types of modification, with large cap size and high degree, and regularization is strongly required for solving the system. Numerical studies in Fennoscandia show that the SGG data can be estimated with an accuracy of 1 mE using an integral estimator modified by a biased type least-squares modification. In this case an integration cap size of 2.5° and a degree of modification of 100 for integrating 30' × 30' gravity anomalies are required.

  4. Freeze drying method

    SciTech Connect

    Coppa, N.V.; Stewart, P.; Renzi, E.

    1999-12-07

    The present invention provides methods and apparatus for freeze drying in which a solution, which can be a radioactive salt dissolved within an acid, is frozen into a solid on vertical plates provided within a freeze drying chamber. The solid is sublimated into vapor and condensed in a cold condenser positioned above the freeze drying chamber and connected thereto by a conduit. The vertical positioning of the cold condenser relative to the freeze dryer helps to help prevent substances such as radioactive materials separated from the solution from contaminating the cold condenser. Additionally, the system can be charged with an inert gas to produce a down rush of gas into the freeze drying chamber to also help prevent such substances from contaminating the cold condenser.

  5. Acclimation of leaf nitrogen to vertical light gradient at anthesis in wheat is a whole-plant process that scales with the size of the canopy.

    PubMed

    Moreau, Delphine; Allard, Vincent; Gaju, Oorbessy; Le Gouis, Jacques; Foulkes, M John; Martre, Pierre

    2012-11-01

    Vertical leaf nitrogen (N) gradient within a canopy is classically considered as a key adaptation to the local light environment that would tend to maximize canopy photosynthesis. We studied the vertical leaf N gradient with respect to the light gradient for wheat (Triticum aestivum) canopies with the aims of quantifying its modulation by crop N status and genetic variability and analyzing its ecophysiological determinants. The vertical distribution of leaf N and light was analyzed at anthesis for 16 cultivars grown in the field in two consecutive seasons under two levels of N. The N extinction coefficient with respect to light (b) varied with N supply and cultivar. Interestingly, a scaling relationship was observed between b and the size of the canopy for all the cultivars in the different environmental conditions. The scaling coefficient of the b-green area index relationship differed among cultivars, suggesting that cultivars could be more or less adapted to low-productivity environments. We conclude that the acclimation of the leaf N gradient to the light gradient is a whole-plant process that depends on canopy size. This study demonstrates that modeling leaf N distribution and canopy expansion based on the assumption that leaf N distribution parallels that of the light is inappropriate. We provide a robust relationship accounting for vertical leaf N gradient with respect to vertical light gradient as a function of canopy size. PMID:22984122

  6. Growth and characterization of 100 mm diameter CdZnTe single crystals by the vertical gradient freezing method

    Microsoft Academic Search

    T. Asahi; O. Oda; Y. Taniguchi; A. Koyama

    1996-01-01

    Recent bulk crystal growth of CdTe and Cd1 ? xZnxTe is reviewed from the viewpoint of large diameter single crystal growth. A VGF method based on a multiple-zone furnace has been developed to grow ?111?-oriented 100 mm diameter single crystals. By this method, ?111?-oriented Cd1 ? xZnxTe single crystals can be reproducibly grown. The grown crystals were characterized by the

  7. Dynamic impact of the vertical shear of gradient wind on the tropical cyclone boundary layer wind field

    NASA Astrophysics Data System (ADS)

    Cai, Ninghao; Xu, Xin; Song, Lili; Bai, Lina; Ming, Jie; Wang, Yuan

    2014-02-01

    This work studies the impact of the vertical shear of gradient wind (VSGW) in the free atmosphere on the tropical cyclone boundary layer (TCBL). A new TCBL model is established, which relies on fiveforce balance including the pressure gradient force, Coriolis force, centrifugal force, turbulent friction, and inertial deviation force. This model is then employed to idealize tropical cyclones (TCs) produced by DeMaria's model, under different VSGW conditions (non-VSGW, positive VSGW, negative VSGW, and VSGW increase/decrease along the radial direction). The results show that the free-atmosphere VSGW is particularly important to the intensity of TC. For negative VSGW, the total horizontal velocity in the TCBL is somewhat suppressed. However, with the maximum radial inflow displaced upward and outward, the radial velocity notably intensifies. Consequently, the convergence is enhanced throughout the TCBL, giving rise to a stronger vertical pumping at the TCBL top. In contrast, for positive VSGW, the radial inflow is significantly suppressed, even with divergent outflow in the middle-upper TCBL. For varying VSGW along the radial direction, the results indicate that the sign and value of VSGW is more important than its radial distribution, and the negative VSGW induces stronger convergence and Ekman pumping in the TCBL, which favors the formation and intensification of TC.

  8. Vertical gradient of nutrients in two dimictic lakes – influence of phototrophic sulfur bacteria on nutrient balance

    Microsoft Academic Search

    Uwe Selig; Thomas Hübener; Reinhard Heerkloss; Hendrik Schubert

    2004-01-01

    Vertical profiles of soluble and particulate nutrients were analyzed at the end of summer stratification in two dimictic lakes located in northeast Germany. In addition, irradiance and plankton biomass were determined. The concentrations of particulate organic carbon and phytoplankton biomass in the epilimnion were higher in Lake Tiefer than in Lake Dudinghausen, even though the apparent trophic status of Lake

  9. The Effect of Recent Venus Transit on Atmospheric Vertical Potential Gradient and ELF-VLF Propagation

    Microsoft Academic Search

    B. K. De; S. K. Adhikari; B. K. Sarkar; S. K. Sarkar; A. Guha; P. K. Mandal; S. K. Mandal; H. P. Sardar; M. Ray

    We take observations from the roof top at a height of 26 meter from ground. The vertical electric field is measured with an ac field-mill which has an aluminum rotor plate of 12 cm. in diameter. The output from the amplifier is recorded through computer sound card at a sample rate of 44,100 per second. The rms value of the

  10. The Gravitational Potential, Gravitational Acceleration, and Vertical Gravity Gradient of a Rising Thermal Mantle Plume: A Numerical Experiment

    NASA Astrophysics Data System (ADS)

    Hinojosa, Juan H.

    2012-10-01

    Thermal convection in the mantles of the terrestrial planets is an important mode of heat transfer from the planet's interior. Gravitational instabilities originating at hot, thermal boundary layers at depth, either at the core-mantle boundary or at an interface between the upper mantle and lower mantle, are responsible for a type of convection that gives rise to thermal mantle plumes. Since the inferred horizontal dimensions of mantle plumes as a whole are small compared with their vertical dimensions, it is difficult to observe mantle plumes directly. To better understand the mantle plume's gravitational expression at the surface, the gravitational potential, gravitational acceleration, and vertical gravity gradient of a rising mantle plume are calculated in a series of numerical experiments. An axially symmetric mantle plume is modeled using a composite of spheres and/or disks of various depths, radii, thicknesses, and density contrasts. The density contrast used in the numerical experiments is due to the temperature difference between an isothermal plume and the local geotherm for plumes at depths greater than the depth of pressure-release melt, and is due to the melt density contrast elsewhere. The resulting gravitational quantities for the spheres are obtained with straight-forward, analytical expressions, but those for the disks are obtained by numerical integration. The results of the numerical experiments will be presented.

  11. A refined model of sedimentary rock cover in the southeastern part of the Congo basin from GOCE gravity and vertical gravity gradient observations

    NASA Astrophysics Data System (ADS)

    Martinec, Zden?k; Fullea, Javier

    2015-03-01

    We aim to interpret the vertical gravity and vertical gravity gradient of the GOCE-GRACE combined gravity model over the southeastern part of the Congo basin to refine the published model of sedimentary rock cover. We use the GOCO03S gravity model and evaluate its spherical harmonic representation at or near the Earth's surface. In this case, the gradiometry signals are enhanced as compared to the original measured GOCE gradients at satellite height and better emphasize the spatial pattern of sedimentary geology. To avoid aliasing, the omission error of the modelled gravity induced by the sedimentary rocks is adjusted to that of the GOCO03S gravity model. The mass-density Green's functions derived for the a priori structure of the sediments show a slightly greater sensitivity to the GOCO03S vertical gravity gradient than to the vertical gravity. Hence, the refinement of the sedimentary model is carried out for the vertical gravity gradient over the basin, such that a few anomalous values of the GOCO03S-derived vertical gravity gradient are adjusted by refining the model. We apply the 5-parameter Helmert's transformation, defined by 2 translations, 1 rotation and 2 scale parameters that are searched for by the steepest descent method. The refined sedimentary model is only slightly changed with respect to the original map, but it significantly improves the fit of the vertical gravity and vertical gravity gradient over the basin. However, there are still spatial features in the gravity and gradiometric data that remain unfitted by the refined model. These may be due to lateral density variation that is not contained in the model, a density contrast at the Moho discontinuity, lithospheric density stratifications or mantle convection. In a second step, the refined sedimentary model is used to find the vertical density stratification of sedimentary rocks. Although the gravity data can be interpreted by a constant sedimentary density, such a model does not correspond to the gravitational compaction of sedimentary rocks. Therefore, the density model is extended by including a linear increase in density with depth. Subsequent L2 and L? norm minimization procedures are applied to find the density parameters by adjusting both the vertical gravity and the vertical gravity gradient. We found that including the vertical gravity gradient in the interpretation of the GOCO03S-derived data reduces the non-uniqueness of the inverse gradiometric problem for density determination. The density structure of the sedimentary formations that provide the optimum predictions of the GOCO03S-derived gravity and vertical gradient of gravity consists of a surface density contrast with respect to surrounding rocks of 0.24-0.28 g/cm3 and its decrease with depth of 0.05-0.25 g/cm3 per 10 km. Moreover, the case where the sedimentary rocks are gravitationally completely compacted in the deepest parts of the basin is supported by L? norm minimization. However, this minimization also allows a remaining density contrast at the deepest parts of the sedimentary basin of about 0.1 g/cm3.

  12. Spatio-temporal distribution of the timing of start and end of growing season along vertical and horizontal gradients in Japan

    NASA Astrophysics Data System (ADS)

    Nagai, Shin; Saitoh, Taku M.; Nasahara, Kenlo Nishida; Suzuki, Rikie

    2015-01-01

    We detected the spatio-temporal variability in the timing of start (SGS) and end of growing season (EGS) in Japan from 2003 to 2012 by analyzing satellite-observed daily green-red vegetation index with a 500-m spatial resolution. We also examined the characteristics of SGS and EGS timing in deciduous broadleaf and needleleaf forests along vertical and horizontal gradients and then evaluated the relationship between their timing and daily mean air temperature. We found that for the timing of SGS and EGS, changes along the vertical gradient in deciduous broadleaf forest tended to be larger than those in deciduous needleleaf forest. For both forest types, changes along the vertical and horizontal gradients in the timing of EGS tended to be smaller than those of SGS. Finally, in both forest types, the sensitivity of the timing of EGS to air temperature was much less than that of SGS. These results suggest that the spatio-temporal variability in the timing of SGS and EGS detected by satellite data, which may be correlated with leaf traits, photosynthetic capacity, and environment conditions, provide useful ground-truthing information along vertical and horizontal gradients.

  13. Spatio-temporal distribution of the timing of start and end of growing season along vertical and horizontal gradients in Japan.

    PubMed

    Nagai, Shin; Saitoh, Taku M; Nasahara, Kenlo Nishida; Suzuki, Rikie

    2015-01-01

    We detected the spatio-temporal variability in the timing of start (SGS) and end of growing season (EGS) in Japan from 2003 to 2012 by analyzing satellite-observed daily green-red vegetation index with a 500-m spatial resolution. We also examined the characteristics of SGS and EGS timing in deciduous broadleaf and needleleaf forests along vertical and horizontal gradients and then evaluated the relationship between their timing and daily mean air temperature. We found that for the timing of SGS and EGS, changes along the vertical gradient in deciduous broadleaf forest tended to be larger than those in deciduous needleleaf forest. For both forest types, changes along the vertical and horizontal gradients in the timing of EGS tended to be smaller than those of SGS. Finally, in both forest types, the sensitivity of the timing of EGS to air temperature was much less than that of SGS. These results suggest that the spatio-temporal variability in the timing of SGS and EGS detected by satellite data, which may be correlated with leaf traits, photosynthetic capacity, and environment conditions, provide useful ground-truthing information along vertical and horizontal gradients. PMID:24781316

  14. An electromagnetic sounding experiment in Germany using the vertical gradient of geomagnetic variations observed in a deep borehole

    NASA Astrophysics Data System (ADS)

    Schmucker, Ulrich; Spitzer, Klaus; Steveling, Erich

    2009-09-01

    We have recorded for 13 d, geomagnetic variations simultaneously on the Earth's surface and in a borehole at 832 m depth straight below, with a sampling rate of 1 Hz. In addition, geoelectric variations were observed at the same site near Bad Königshofen in Frankonia, Germany. The penetrated moderately conductive Triassic sediments lie above highly resistive Permian deposits. A presumably crystalline basement begins at 1500-1900 m depth. The purpose of the experiment is to determine the skin effect of geomagnetic variations and to derive from it the equivalent to the magnetotelluric (MT) surface impedance, using the vertical gradient (VG) method of electromagnetic (EM) sounding. In this way, we were able to reproduce all four elements of the MT impedance tensor, except for an unexplained but consistent downward shift of VG phases against MT phases by roughly 15° for the two off-diagonal elements. Hence, our tensor evaluation goes beyond the common practice, to express the skin effect by a single VG transfer function in response to a layered structure. The otherwise good agreement of VG and MT results implies that at our test site, the MT impedance tensor is largely distortion-free and that, for example, its pronounced anisotropy should be regarded as a genuine characteristic of the EM response for a laterally non-uniform or possibly anisotropic deep structure. The drilling site lies within the range of a widespread induction anomaly. We have observed the resulting variations of the vertical magnetic component at the surface and in the borehole and found them to be identical. The thus established absence of a skin effect for the vertical component allows us to treat the sedimentary layer down to the depth of the borehole instrument as a thin sheet, and the pertinent thin-sheet approximation for EM induction forms the basis of our analysis. We have derived the required estimate of conductance from the skin effect of horizontal components, noting that this estimate has to be real valued and the same for all frequencies. We were unable, however, to verify the resulting value of 76 S with independent geoelectric direct current (DC) measurements in the borehole and at the Earth's surface. A model study shows that the thin-sheet conductance, which is relevant for the skin effect, may be substantially higher than the depth-integrated conductivity from DC data. Robust estimates of transfer functions were derived for 20 frequencies from 5.625 to 0.007 cpm, which corresponds to periods from 10 to 10000 s. Squared skin effect coherencies are above 0.9 for periods longer than 20 s and thereby comparable to MT coherencies.

  15. [FeFe]-Hydrogenase Abundance and Diversity along a Vertical Redox Gradient in Great Salt Lake, USA

    PubMed Central

    Boyd, Eric S.; Hamilton, Trinity L.; Swanson, Kevin D.; Howells, Alta E.; Baxter, Bonnie K.; Meuser, Jonathan E.; Posewitz, Matthew C.; Peters, John W.

    2014-01-01

    The use of [FeFe]-hydrogenase enzymes for the biotechnological production of H2 or other reduced products has been limited by their sensitivity to oxygen (O2). Here, we apply a PCR-directed approach to determine the distribution, abundance, and diversity of hydA gene fragments along co-varying salinity and O2 gradients in a vertical water column of Great Salt Lake (GSL), UT. The distribution of hydA was constrained to water column transects that had high salt and relatively low O2 concentrations. Recovered HydA deduced amino acid sequences were enriched in hydrophilic amino acids relative to HydA from less saline environments. In addition, they harbored interesting variations in the amino acid environment of the complex H-cluster metalloenzyme active site and putative gas transfer channels that may be important for both H2 transfer and O2 susceptibility. A phylogenetic framework was created to infer the accessory cluster composition and quaternary structure of recovered HydA protein sequences based on phylogenetic relationships and the gene contexts of known complete HydA sequences. Numerous recovered HydA are predicted to harbor multiple N- and C-terminal accessory iron-sulfur cluster binding domains and are likely to exist as multisubunit complexes. This study indicates an important role for [FeFe]-hydrogenases in the functioning of the GSL ecosystem and provides new target genes and variants for use in identifying O2 tolerant enzymes for biotechnological applications. PMID:25464382

  16. Long-distance abscisic acid signalling under different vertical soil moisture gradients depends on bulk root water potential and average soil water content in the root zone.

    PubMed

    Puértolas, Jaime; Alcobendas, Rosalía; Alarcón, Juan J; Dodd, Ian C

    2013-08-01

    To determine how root-to-shoot abscisic acid (ABA) signalling is regulated by vertical soil moisture gradients, root ABA concentration ([ABA](root)), the fraction of root water uptake from, and root water potential of different parts of the root zone, along with bulk root water potential, were measured to test various predictive models of root xylem ABA concentration [RX-ABA](sap). Beans (Phaseolus vulgaris?L. cv. Nassau) were grown in soil columns and received different irrigation treatments (top and basal watering, and withholding water for varying lengths of time) to induce different vertical soil moisture gradients. Root water uptake was measured at four positions within the column by continuously recording volumetric soil water content (?v). Average ?v was inversely related to bulk root water potential (?(root)). In turn, ?(root) was correlated with both average [ABA](root) and [RX-ABA](sap). Despite large gradients in ?v, [ABA](root) and root water potential was homogenous within the root zone. Consequently, unlike some split-root studies, root water uptake fraction from layers with different soil moisture did not influence xylem sap (ABA). This suggests two different patterns of ABA signalling, depending on how soil moisture heterogeneity is distributed within the root zone, which might have implications for implementing water-saving irrigation techniques. PMID:23387513

  17. Vertical composition gradient effects on original hydrocarbon in place volumes and liquid recovery for volatile oil and gas condensate reservoirs

    E-print Network

    Jaramillo Arias, Juan Manuel

    2000-01-01

    Around the world, volatile oil and retrograde gas reservoirs are considered as complex thermodynamic systems and even more when they exhibit vertical composition variations. Those systems must be characterized by an equation of state (EOS...

  18. Fine-scale horizontal and vertical micro-distribution patterns of testate amoebae along a narrow fen/bog gradient

    E-print Network

    Paris-Sud XI, Université de

    fen/bog gradient Vincent E.J. Jassey1* , Geneviève Chiapusio1 , Edward A.D. Mitchell2 , Philippe Binet) and a young bog (bog) with9 more marked micro-topography and mosaic of poor-fen and bog vegetation. We) as well as the habitat (fen/bog) and the sampling depth.14 Testate amoeba Shannon H` diversity

  19. Vertical distribution of zooplankton in subalpine and alpine lakes: Ultraviolet radiation, fish predation, and the transparency-gradient hypothesis

    E-print Network

    Williamson, Craig E.

    as a proxy for fish predation), temperature, pH, conductivity, chlorophyll a (Chl a), and zooplankton of the variance in zooplankton vertical distribution than did either PAR or chlorophyll. Calanoids had high. For example, the response of Daphnia to variation in food concentrations in the water column is modified

  20. Ultrathin (1 nm) vertically shadowed platinum-carbon replicas for imaging individual molecules in freeze-etched biological DNA and material science metal and plastic specimens.

    PubMed

    Ruben, G C

    1989-12-01

    Single molecule resolution in beam-sensitive, uncoated, noncrystalline materials has heretofore not been possible except in thin (less than or equal to 150 A) platinum-carbon (Pt-C) replicas, which are resistant to electron beam destruction. Previously, the granularity of metal film replicas limited their resolution to greater than or equal to 20 A. This paper demonstrates that Pt-C film granularity and resolution are a function of the method of replication and other controllable factors. Low-angle 20 degrees rotary, 45 degrees unidirectional, and vertical 9.7 +/- 1 A Pt-C films deposited on mica under the same conditions were compared. Vertical replication had a 5 A granularity, the highest resolution, and evenly coated the whole surface. A 45 degrees replication had a 9.5 A granularity, a slightly poorer resolution, and a discontinuous surface coating. The use of 20 degrees rotary replication proved to be unsuitable for high-resolution imaging, with 20-25 A granularity and resolution two to three times poorer. Vertical and 45 degrees Pt-C replicas can visualize the deep-etched DNA helix and the 13.3 A 3(2) helix of pectin in a gel. The DNA double helix, the complex structures of sol-gel glasses, Immobilon filters (polyvinylidene fluoride), a polymethacrylate plastic, the metal oxide surfaces of 440c stainless steel, and aluminum are illustrated. This high-resolution vertical Pt-C replica technique can image in the context of solutions, gels, or solids, single molecular chains 3-7 A wide, their associations, and their conformation. Included in the present article are first time descriptions for removing replicas from metals and plastics and for making high-magnification photographic prints of normal contrast using a reversal rephotographic process. PMID:2809773

  1. When hot water freezes before cold

    E-print Network

    J. I. Katz

    2006-04-27

    I suggest that the origin of the Mpemba effect (the freezing of hot water before cold) is freezing-point depression by solutes, either gaseous or solid, whose solubility decreases with increasing temperature so that they are removed when water is heated. They are concentrated ahead of the freezing front by zone refining in water that has not been heated, reduce the temperature of the freezing front, and thereby reduce the temperature gradient and heat flux, slowing the progress of the front. I present a simple calculation of this effect, and suggest experiments to test this hypothesis.

  2. Freeze Technology for Nuclear Applications - 13590

    SciTech Connect

    Rostmark, Susanne C.; Knutsson, Sven [Lulea University of Technology (Sweden)] [Lulea University of Technology (Sweden); Lindberg, Maria [Studsvik Nuclear AB, 611 82 Nykoeping (Sweden)] [Studsvik Nuclear AB, 611 82 Nykoeping (Sweden)

    2013-07-01

    Freezing of soil materials is a complicated process of a number of physical processes: - freezing of pore water in a thermal gradient, - cryogenic suction causing water migration and - ice formation expanding pores inducing frost heave. Structural changes due to increase of effective stress during freezing also take place. The over consolidation gives a powerful dewatering/drying effect and the freeze process causes separation of contaminates. Artificial ground freezing (AGF is a well established technique first practiced in south Wales, as early as 1862. AGF is mostly used to stabilize tunnels and excavations. During the last ten years underwater applications of freeze technologies based on the AGF have been explored in Sweden. The technology can, and has been, used in many different steps in a remediation action. Freeze Sampling where undisturbed samples are removed in both soft and hard sediment/sludge, Freeze Dredging; retrieval of sediment with good precision and minimal redistribution, and Freeze Drying; volume reduction of contaminated sludge/sediment. The application of these technologies in a nuclear or radioactive environment provides several advantages. Sampling by freezing gives for example an advantage of an undisturbed sample taken at a specified depth, salvaging objects by freezing or removal of sludges is other applications of this, for the nuclear industry, novel technology. (authors)

  3. Vertical gradients of steady-state mean annual ground temperatures in seasonally frozen soil and permafrost explored by numerical experiments

    NASA Astrophysics Data System (ADS)

    Gruber, Stephan; Dall'Amico, Matteo; Endrizzi, Stefano; Rigon, Riccardo

    2010-05-01

    The mean annual ground temperature in the upper meters of the subsurface often is lower at depth than close to the surface. Especially in temperate and cold climates, this effect is results in a considerable "thermal offset" between mean ground surface temperatures and temperatures at the depth of a few meters. It is largely due to the contrast between the bulk thermal conductivity of the soil during cold and during warm periods. This is caused by variable proportions of ice, water and air in the soil due to water movement and phase change and results in a "thermal diode" effect. This study is based on numerical experimentation with the model GEOtop that simulates the heat and water transfer in saturated and unsaturated soil. We use harmonic Dirichlet boundary conditions with diverse means as well as annual and daily amplitudes to study the effects of surface forcing. These experiments are performed on differing ground types and water saturations and spun over long time scales (decades to centuries) to approach equilibrium conditions. The results allow an insight into the importance of a sophisticated treatment of soil freezing and thawing in permafrost models.

  4. Spatial and vertical gradients in the stable carbon isotope composition of Lower Circumpolar Deep Water over the last 900 thousand years

    NASA Astrophysics Data System (ADS)

    Williams, T.; Hillenbrand, C. D.; Piotrowski, A. M.; Smith, J.; Hodell, D. A.; Frederichs, T.; Allen, C. S.

    2014-12-01

    Changes in stable carbon isotopes (?13C) recorded in benthic foraminiferal calcite reflect that of the dissolved inorganic carbon (DIC) of ambient seawater, and thus are used to reconstruct past changes in water mass mixing. Records of benthic foraminiferal ?13C from the Atlantic Ocean have revealed the development of a sharp vertical ?13C gradient between 2300-2500m water depth during successive glacial periods throughout the Late Quaternary, with extremely negative ?13C values recorded below this depth. It had been hypothesised that this gradient resulted from an increased stratification of water masses within the glacial Atlantic Ocean, and that these extreme ?13C values originated in the Southern Ocean. However the mechanisms behind the formation of this gradient and extreme ?13C depletion have remained unclear. This is in part due to the poor preservation of calcareous microfossils in the corrosive waters below 2500-3000m found in the Southern Ocean, which hampers our understanding of this key region. Here we present a unique new ?13C deep water record measured on benthic foraminifera (Cibicidoides spp.) from a sediment core recovered from 2100m water depth in the Amundsen Sea, south-eastern Pacific sector of the Southern Ocean. The site is bathed in Lower Circumpolar Deep Water (LCDW) today, and combined palaeomagnetic and oxygen isotope stratigraphy show that the sediments continuously span at least the last 890 ka. A comparison of this new ?13C data with other LCDW records from ODP Sites 1089/1090 in the South Atlantic and ODP Site 1123 in the Southwest Pacific demonstrate a clear spatial gradient in circum-Antarctic LCDW during glacial periods. The pool of extremely depleted glacial deep marine ?13C is restricted to the Atlantic Sector of the Southern Ocean, with increasingly positive ?13C values found in the Southwest Pacific and the south-eastern Pacific sector of the Southern Ocean. This implies that the ?13C depletion in the deep glacial Atlantic was sourced in the Atlantic sector of the Southern Ocean, and remained limited to this sector. This finding indicates either increased supply of relatively more positive ?13C deep waters or increased vertical mixing in the Indian and Pacific sectors of the glacial Southern Ocean.

  5. Leaf reflectance variation along a vertical crown gradient of two deciduous tree species in a Belgian industrial habitat.

    PubMed

    Khavaninzadeh, Ali Reza; Veroustraete, Frank; Van Wittenberghe, Shari; Verrelst, Jochem; Samson, Roeland

    2015-09-01

    The reflectometry of leaf asymmetry is a novel approach in the bio-monitoring of tree health in urban or industrial habitats. Leaf asymmetry responds to the degree of environmental pollution and reflects structural changes in a leaf due to environmental pollution. This paper describes the boundary conditions to scale up from leaf to canopy level reflectance, by describing the variability of adaxial and abaxial leaf reflectance, hence leaf asymmetry, along the crown height gradients of two tree species. Our findings open a research pathway towards bio-monitoring based on the airborne remote sensing of tree canopies and their leaf asymmetric properties. PMID:26057363

  6. Reconstructing the Late Pleistocene Southern Ocean biological pump using the vertical gradient of Cd/Ca in planktic and benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Charidemou, Miros; Hall, Ian; Ziegler, Martin

    2015-04-01

    The Southern Ocean is a particularly important region in the global carbon cycle because its wind-driven upwelling regime brings CO2-rich deep waters to the ocean surface. However, outgassing of CO2 to the atmosphere is ultimately determined by the efficiency of the soft-tissue biological pump which transfers carbon back into the deep sea. Biological productivity in the Southern Ocean on glacial-interglacial timescales is thought to be influenced by the availability of iron from terrestrial dust sources (Martin, 1990). However, the exact nature of the relationship between productivity and dust flux is still debated (Ziegler et al., 2013; Martinez-Garcia et al., 2014) and remains unclear for earlier times such as during the Middle Pleistocene Transition (MPT). Changes in the strength of the soft-tissue biological pump can be reconstructed with relative ease by measuring carbon isotopes in planktic and benthic foraminifera and quantifying the vertical gradient between them (Ziegler et al., 2013). Our ultimate aim is to use this technique to reconstruct changes in the biological pump in the Southern Ocean during the MPT, when a sharp rise in dust flux is observed in the sedimentary record (Martinez-Garcia et al., 2011). This will allow us to assess the contribution of changes in the Southern Ocean biological pump to the climatic reorganisation that occurred during the MPT. However, before the ??13C record is constructed for the MPT it is vital to confirm that this method is indeed a reliable proxy for the soft-tissue biological pump. Records of ??13C can be influenced by changes in the whole ocean inventory of ?13C, changes in circulation and changes in the degree of fractionation between the ocean and the atmosphere. The impact of inventory and circulation changes can be minimised by careful selection of study sites and by targeting foraminifera that live within specific water masses. However, deviations of ??13C from the biological signal could certainly arise due to ?13C fractionation between the ocean and the atmosphere. Due to the similarity in the distribution of phosphate and cadmium (Cd) in the ocean and the incorporation of this trace metal into the calcite tests of foraminifera, Cd/Ca ratios can provide an additional proxy for reconstructing the vertical nutrient distribution in the ocean in the same way as ?13C. We present downcore records of Cd/Ca in the deep-dwelling planktic species, Globorotalia truncatulinoides (s) and the benthic species, Cibicidoides wuellerstorfi from sediment core MD02-2588. A new core a core-top calibration of Cd/Ca in G. truncatulinoides, combined with the established calibration for benthic species allows us to estimate seawater Cd within intermediate and deep water masses that bath the study site and to reconstruct the vertical seawater Cd gradient (?Cdsw) over the past 150,000 years. Comparison of ?Cdsw to ??13C from the same samples from core MD02-2588 in the Southern Ocean indicate a very similar downcore variability which supports the use of the ??13C method to reconstruct the biological pump during the MPT.

  7. Vertical structure and horizontal gradients of aerosol extinction coefficients over coastal India inferred from airborne lidar measurements during the Integrated Campaign for Aerosol, Gases and Radiation Budget (ICARB) field campaign

    NASA Astrophysics Data System (ADS)

    Satheesh, S. K.; Krishna Moorthy, K.; Suresh Babu, S.; Vinoj, V.; Nair, Vijayakumar S.; Naseema Beegum, S.; Dutt, C. B. S.; Alappattu, D. P.; Kunhikrishnan, P. K.

    2009-03-01

    Quantitative estimates of the vertical structure and the spatial gradients of aerosol extinction coefficients have been made from airborne lidar measurements across the coastline into offshore oceanic regions along the east and west coasts of India. The vertical structure revealed the presence of strong, elevated aerosol layers in the altitude region of ˜2-4 km, well above the atmospheric boundary layer (ABL). Horizontal gradients also showed a vertical structure, being sharp with the e-1 scaling distance (D0H) as small as ˜150 km in the well-mixed regions mostly under the influence of local source effects. Above the ABL, where local effects are subdued, the gradients were much shallower (˜600-800 km); nevertheless, they were steep compared to the value of ˜1500-2500 km reported for columnar AOD during winter. The gradients of these elevated layers were steeper over the east coast of India than over the west coast. Near-simultaneous radio sonde (Vaisala, Inc., Finland) ascents made over the northern Bay of Bengal showed the presence of convectively unstable regions, first from surface to ˜750-1000 m and the other extending from 1750 to 3000 m separated by a stable region in between. These can act as a conduit for the advection of aerosols and favor the transport of continental aerosols in the higher levels (>2 km) into the oceans without entering the marine boundary layer below. Large spatial gradient in aerosol optical and hence radiative impacts between the coastal landmass and the adjacent oceans within a short distance of <300 km (even at an altitude of 3 km) during summer and the premonsoon is of significance to the regional climate.

  8. Selective decrepitation and analysis of individual fluid inclusions: hydrodynamic implications of super-hydrostatic fossil fluid pressure gradients in epithermal Ag-Au veins

    Microsoft Academic Search

    R. R. Loucks; M. A. II Sommer

    1985-01-01

    Fluid pressure gradients were reconstructed from heating\\/freezing data and analysis of COâ, CHâ and HâS in fluid inclusions (fi's) that trapped the liquid phase of boiling solutions in three meteoric hydrothermal systems. A 30 ..mu..m-diameter, 0.4 MW, Q-switched laser light pulse was fired down the vertical tube of an optical microscope to decrepitate in vacuo selected individual fi's; mol ratios

  9. Versatile wedge-based system for the construction of unidirectional collagen scaffolds by directional freezing: practical and theoretical considerations.

    PubMed

    Pot, Michiel W; Faraj, Kaeuis A; Adawy, Alaa; van Enckevort, Willem J P; van Moerkerk, Herman T B; Vlieg, Elias; Daamen, Willeke F; van Kuppevelt, Toin H

    2015-04-29

    Aligned unidirectional collagen scaffolds may aid regeneration of those tissues where alignment of cells and extracellular matrix is essential, as for instance in cartilage, nerve bundles, and skeletal muscle. Pores can be introduced by ice crystal formation followed by freeze-drying, the pore architecture reflecting the ice crystal morphology. In this study we developed a wedge-based system allowing the production of a wide range of collagen scaffolds with unidirectional pores by directional freezing. Insoluble type I collagen suspensions were frozen using a custom-made wedge system, facilitating the formation of a horizontal as well as a vertical temperature gradient and providing a controlled solidification area for ice dendrites. The system permitted the growth of aligned unidirectional ice crystals over a large distance (>2.5 cm), an insulator prolonging the freezing process and facilitating the construction of crack-free scaffolds. Unidirectional collagen scaffolds with tunable pore sizes and pore morphologies were constructed by varying freezing rates and suspension media. The versatility of the system was indicated by the construction of unidirectional scaffolds from albumin, poly(vinyl alcohol) (a synthetic polymer), and collagen-polymer blends producing hybrid scaffolds. Macroscopic observations, temperature measurements, and scanning electron microscopy indicated that directed horizontal ice dendrite formation, vertical ice crystal nucleation, and evolutionary selection were the basis of the aligned unidirectional ice crystal growth and, hence, the aligned unidirectional pore structure. In conclusion, a simple, highly adjustable freezing system has been developed allowing the construction of large (hybrid) bioscaffolds with tunable unidirectional pore architecture. PMID:25822583

  10. Inner Core Melting and Freezing: Where and How (Invited)

    NASA Astrophysics Data System (ADS)

    Cormier, V. F.

    2010-12-01

    Combined sesimology, geodynamic, and geodynamo modeling can test several hypotheses for the mechanisms of growth of Earth’s inner core exhibited by hemispherical lateral variations in its upper 600 km. Weak backscattered PKiKP in the equatorial eastern hemisphere can be made consistent with either a hypothesis of freezing or melting. In a melting hypothesis, the eastern hemisphere is older with possibly larger crystals or smaller elastic contrasts across grain boundaries providing weaker backscatter to the coda of PKiKP. By viscolasticity, partial melt or high homologous temperatures might then explain the lower Q of transmitted PKIKP in the eastern hemisphere. Alternatively, an eastern hemisphere that grows radially outward might have crystals stretched in the vertical direction. By scattering, this hypothesis can simultaneously explain weak backscattered PKiKP coda and high attenuation of transmitted PKIKP from the loss of backscattered energy at angles perpendicular to the vertically oriented crystals. Pseudospectral synthesis that combines texture and viscoelasticity can help discriminate between these two mechanisms. Geodynamic and geodynamo modeling can assist in this discrimination: (1) by predicting flow patterns in outer core, including their influence on spatial spectrum of the non-dipole field and the stability of a layer of reduced gradient in compressional velocity near the inner core boundary; (2) by predicting the deformation in the uppermost solid inner core, including its effect on elastic and attenuation anisotropy.

  11. Freezing in confined geometries

    NASA Technical Reports Server (NTRS)

    Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.

    1992-01-01

    Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.

  12. Freezing Fish and Shellfish.

    E-print Network

    Nickelson, Ranzell; Reddell, Annette

    1980-01-01

    contents may impart off-odors and off flavors to the flesh. Digestive enzymes and bacteria found in the intestinal fluids also can begin to digest the fish flesh before the product freezes. The dark flesh of fish is usually less stable in frozen... means of preserving the fresh-caught quality of fish and shellfish. Why Freeze? Freezing preserves foods by lowering their tem peratures to a point not conducive to bacterial growth and natural enzyme action. Many spoilage bacteria are destroyed...

  13. The effect of horizontal gradients and spatial measurement resolution on the retrieval of global vertical NO2 distributions from SCIAMACHY measurements in limb only mode

    NASA Astrophysics Data System (ADS)

    Puä·Ä«Te, J.; Kühl, S.; Deutschmann, T.; Dörner, S.; Jöckel, P.; Platt, U.; Wagner, T.

    2010-08-01

    Limb measurements provided by the Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale. Combining measurements of the same air volume from different viewing positions along the orbit, a tomographic approach can be applied and 2-D distribution fields of stratospheric trace gases can be acquired in one inversion. With this approach, it is possible to improve the accounting for the effect of horizontal gradients in the trace gas distribution on the profile retrieval. This was shown in a previous study for the retrieval of NO2 and OClO profiles in the Arctic region near the polar vortex boundary. In this study, the tomographic retrieval is applied on measurements during special limb-only orbits performed on 14 December 2008. For these orbits the distance between consecutive limb scanning sequences was reduced to ~3.3° of the orbital circle (i.e. more than two times with respect to the nominal operational mode). Thus, the same air volumes are scanned successively by more than one scanning sequence also for midlatitudes and the tropics. It is found that the profiles obtained by the tomographic 2-D approach show significant differences to those obtained by the 1-D approach. In particular, for regions close to stratospheric transport barriers (i.e. near to the edge of the polar vortex and subtropical transport barrier) up to 50% larger or smaller NO2 number densities (depending on the sign of the gradient along the line of sight) for altitudes below the peak of the profile (around 20 km) are obtained. The limb-only measurements allow examining the systematic error if the horizontal gradient is not accounted for, and studying the impact of the gradient strength on the profile retrieval on a global scale. The findings for the actual SCIAMACHY observations are verified by sensitivity studies for simulated data for which the NO2 distributions to be retrieved are known in advance. In addition, the impact of the horizontal distance between consecutive limb scanning sequences on the quality of the tomographic 2-D retrieval is investigated and a possibility to take into account the horizontal gradients by an interpolation approach is studied.

  14. The effect of horizontal gradients and spatial measurement resolution on the retrieval of global vertical NO2 distributions from SCIAMACHY measurements in limb only mode

    NASA Astrophysics Data System (ADS)

    Puä·Ä«Te, J.; Kühl, S.; Deutschmann, T.; Dörner, S.; Jöckel, P.; Platt, U.; Wagner, T.

    2010-05-01

    Limb measurements provided by the Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale. Combining measurements of the same air volume from different viewing positions along the orbit, a tomographic approach can be applied and 2-D distribution fields of stratospheric trace gases can be acquired in one inversion. With this approach, it is possible to improve the accounting for the effect of horizontal gradients in the trace gas distribution on the profile retrieval. This was shown in a previous study for the retrieval of NO2 and OClO profiles in the Arctic region near the polar vortex boundary. In this study, the tomographic retrieval is applied on measurements during special limb-only orbits performed on 14 December 2008. For these orbits the distance between consecutive limb scanning sequences was reduced to ~3.3° of the orbital circle (i.e. more than two times with respect to the nominal operational mode). Thus, the same air volumes are scanned successively by more than one scanning sequence also for midlatitudes and the tropics. It is found that the profiles obtained by the tomographic 2-D approach show significant differences to those obtained by the 1-D approach. In particular, for regions close to stratospheric transport barriers (i.e. near to the edge of the polar vortex and subtropical transport barrier) up to 50% larger or smaller NO2 number densities (depending on the sign of the gradient along the line of sight) for altitudes below the peak of the profile (around 20 km) are obtained. The limb-only measurements allow examining the systematic error if the horizontal gradient is not accounted for, and studying the impact of the gradient strength on the profile retrieval on a global scale. The findings for the actual SCIAMACHY observations are verified by sensitivity studies for simulated data for which the NO2 distributions to be retrieved are known in advance. In addition, the impact of the horizontal distance between consecutive limb scanning sequences on the quality of the tomographic 2-D retrieval is investigated and a possibility to take into account the horizontal gradients by an interpolation approach is studied.

  15. Seasonal and Inter-Annual Variability of the Near-Surface Freeze/Thaw Cycle in the Contiguous United States

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Armstrong, R. L.

    2004-05-01

    Better knowledge and understanding of the near-surface freeze/thaw cycle of soils are prerequisite for evaluating the impact of cold season/cold region processes on surface and subsurface hydrology, regional and global climate,carbon exchange between the atmosphere and the land, and the terrestrial ecosystem as a whole. To investigate seasonal and inter-annual variations of the near-surface soil freeze/thaw cycle, a frozen soil algorithm was developed and validated to detect the near-surface soil freeze-thaw cycle over snow-free and snow-covered land areas. The frozen soil algorithm consists of two parts: (i) over snow-free land areas, passive microwave satellite remote sensing algorithm was used to detect the near-surface soil freeze-thaw cycle; (ii) over snow-covered land areas, a one-dimensional numerical heat transfer model with phase change was used to detect soil freeze-thaw status under snow cover. Using the Defense Meteorological Satellite Program's Special Sensor Microwave Imager (SSM/I) data, the passive microwave satellite remote sensing algorithm utilizes a negative spectral gradient between 19 GHz and 37 GHz, vertically polarized brightness temperatures and a cut-off brightness temperature at 37 GHz with vertical polarization (TB(37V)). A cut-off brightness temperature of 258.2K was obtained based on a linear correlation (r=0.92) between the soil temperature at 5 cm depth and the TB(37V). Soil temperatures used in the correlation were measured from 26 stations over the contiguous United States for the period from July 1, 1997 through June 30, 1998. Using soil temperature data measured from the same stations for the period from July 1, 1998 through June 30, 1999, the frozen soil algorithm provides the accuracy of frozen soil detection of about 76 percent and the correct classification of both frozen and unfrozen soils of approximately 83 percent with the percent error of about 17 percent. The frozen soil algorithm was used to investigate the near-surface soil freeze/thaw cycle over the GAPP study area from 1978 through 2003. We will present variations of the timing, duration and number of days, and daily area extent of the near-surface frozen soils over the period of record in the contiguous United States. Further algorithm validation is needed to improve the accuracy of the near-surface soil freeze/thaw cycle detection and to estimate thickness of the seasonally frozen ground.

  16. Bjorken model with Freeze Out

    E-print Network

    V. K. Magas; L. P. Csernai

    2007-11-19

    The freeze out of the expanding systems, created in relativistic heavy ion collisions, is discussed. We combine Bjorken scenario with earlier developed freeze out equations into a unified model. The important feature of the proposed model is that physical freeze out is completely finished in a finite time, which can be varied from 0 (freeze out hypersurface) to infinity. The dependence of the post freeze out distribution function on this freeze out time will be studied. As an example model is completely solved and analyzed for the gas of pions.

  17. Fuel Cell Freeze Startup and Landscape of FC Freeze Patents

    E-print Network

    Patents · Top categories ­ Fuel cell stack (212) ­ Piping (104) ­ Solid electrolyte fuel cell (119Fuel Cell Freeze Startup and Landscape of FC Freeze Patents DOE Workshop on Fuel Cell Operations of PEM fuel cells from sub-freezing temperatures. Approach · Collect data/information through literature

  18. Freezing Poultry for Home Use 

    E-print Network

    Davis, Michael

    2006-08-31

    Purchasing fresh poultry in large packages and freezing it in quantities suitable for individual meals can stretch time and food dollars. Topics include packaging needs, cutting, storing and thawing instructions, and freezing pre-cooked meals....

  19. Freezing and thawing processes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seasonally frozen soil strongly influences runoff and erosion on large areas of land around the world. In many areas, rain or snowmelt on seasonally frozen soil is the single leading cause of severe runoff and erosion events. As soils freeze, ice blocks the soil pores, greatly diminishing the perm...

  20. Animal Anti-Freeze

    NSDL National Science Digital Library

    2012-06-26

    In this outdoor winter activity, learners search for and create hibernation sites that will protect gelatin "animals" from freezing. Learners come to understand that hibernating animals need to take care in selecting a sleeping spot that will provide protection from the winter cold.

  1. Freezing of triangulations

    NASA Astrophysics Data System (ADS)

    Kownacki, J.-P.

    2004-04-01

    Zero temperature dynamics of two dimensional triangulations of a torus with curvature energy is described. Numerical simulations strongly suggest that the model get frozen in metastable states, made of topological defects on flat surfaces, that group into clusters of same topological charge. It is conjectured that freezing is related to high temperature structure of baby universes.

  2. Modeling soil freezing dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seasonally frozen soil strongly influences runoff and erosion on large areas of land around the world. In many areas, rain or snowmelt on seasonally frozen soil is the single leading cause of severe runoff and erosion events. As soils freeze, ice blocks the soil pores, greatly diminishing the permea...

  3. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 2010-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture... Rooms and Compartments § 58.621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures...

  4. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture... Rooms and Compartments § 58.621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures...

  5. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture... Rooms and Compartments § 58.621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures...

  6. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture... Rooms and Compartments § 58.621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures...

  7. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture... Rooms and Compartments § 58.621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures...

  8. Freeze-drying of proteins.

    PubMed

    Liu, Baolin; Zhou, Xinli

    2015-01-01

    Freeze-drying has become one of the most important processes for the preservation of biological products. This chapter provides protocols for freeze-drying of proteins and discusses the importance of formulation, cycle development, and validation. Specific formulations for stabilization of proteins are presented as well as advice on common problems with freeze-drying of proteins. PMID:25428023

  9. Effects of freezing on plant mesophyll cells.

    PubMed

    Krause, G H; Grafflage, S; Rumich-Bayer, S; Somersalo, S

    1988-01-01

    Freezing and thawing of leaves of herbaceous plants leads to damage when the freezing temperature falls below a certain tolerance limit, which depends on the plant species and state of acclimation. Such damage is expressed as an irreversible inhibition of photosynthesis observed after thawing. In frost-damaged leaves the capacity of photosynthetic reactions of the thylakoid membranes is impaired. Particularly, the water-oxidation system, photosystems II and I are inhibited. However, it appears that CO2 assimilation is more readily affected by freezing stress than the activity of the thylakoids. The inhibition of CO2 fixation seen in initial stages of damage seems to be independent of thylakoid inactivation. This can be shown by chlorophyll fluorescence analysis made simultaneously with measurement of CO2 assimilation. Fluorescence emission by leaves is strongly influenced by carbon assimilation activity, namely via the redox state of the photosystem II electron acceptor QA (QA-dependent quenching) and via energization of the thylakoid membranes depending on the transthylakoid proton gradient (energy-dependent quenching). Resolution of these components of fluorescence changes provides insight into alterations of the CO2 fixing capacity of the chloroplasts and properties of the thylakoids. The effects of freezing and thawing were studied in detail with isolated mesophyll protoplasts prepared from both non-hardened and cold-acclimated plants of Valerianella locusta L. Freezing damage was characterized by various parameters such as plasma membrane integrity, photosynthetic CO2 assimilation, chlorophyll fluorescence emission and activities of thylakoids isolated from the protoplasts. All tests indicated a substantially increased frost tolerance of protoplasts obtained from cold-acclimated as compared to non-hardened leaves. CO2 assimilation and related fluorescence changes were the most freezing-sensitive parameters in both types of protoplasts. Inactivation of CO2 assimilation was correlated neither to the disintegration of the plasma membrane nor to inactivation of the thylakoids. Experimental data indicate that freeze-thaw treatment affected the light-regulated enzymes of the carbon reduction cycle, such as fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase and ribulose-1,5-bisphosphate carboxylase. Inhibition of light-activation of these enzymes may be based on altered properties of the chloroplast envelope. PMID:3077862

  10. Thermodynamical effects accompanied freezing of two water layers separated by sea ice sheet

    NASA Astrophysics Data System (ADS)

    Bogorodsky, Petr; Marchenko, Aleksey

    2014-05-01

    The process of melt pond freezing is very important for generation of sea ice cover thermodynamic and mass balance during winterperiod. However, due to significant difficulties of field measurements the available data of model estimations still have no instrumental confirmation. In May 2009 the authors carried out laboratory experiment on freezing of limited water volume in the University Centre in Svalbard ice tank. In the course of experiment fresh water layer of 27.5 cm thickness at freezing point poured on the 24 cm sea ice layer was cooled during 50 hours at the temperature -10º C and then once again during 60 hours at -20º C. For revealing process typical characteristics the data of continuous measurements of temperature and salinity in different phases were compared with data of numerical computations obtained with thermodynamic model which was formulated in the frames of 1-D equation system (infinite extension of water freezing layer) and adapted to laboratory conditions. The known surprise of the experiment became proximity of calculated and measured estimates of process dynamics that confirmed the adequacy of the problem mathematical statement (excluding probably process finale stage). This effect can be explained by formation of cracks on the upper layer of ice at sharp decreases of air temperature, which temporary compensated hydrostatic pressure growth during freezing of closed water volume. Another compensated mechanism can be migration of brine through the lower layer of ice under influence of vertical pressure gradient and also rejection of gas dissolved in water which increased its compressibility. During 110 hours cooling thickness of water layer between ice layers reduced approximately to 2 cm. According to computations this layer is not chilled completely but keeps as thin brine interlayer within ice body whose thickness (about units of mm) is determined by temperature fluctuations of cooled surface. Nevertheless, despite good coincidence of experimental and model estimates the question of existence of liquid phase under actual conditions is still open and can be clarified in a continuous laboratory experiment. This work was supported by Russian Foundation for Basic Research (Project # 14-05-00677).

  11. Freezing and Food Safety

    MedlinePLUS

    ... Administrative Forms Standard Forms Skip Navigation Z7_0Q0619C0JGR010IFST1G5B10H1 Web Content Viewer (JSR 286) Actions ${title} Loading... / Topics / ... Food Safety / Freezing and Food Safety Z7_0Q0619C0JGR010IFST1G5B10H3 Web Content Viewer (JSR 286) Actions ${title} Loading... Z7_ ...

  12. Split-sample comparison of directional and liquid nitrogen vapour freezing method on post-thaw semen quality in white rhinoceroses ( Ceratotherium simum simum and Ceratotherium simum cottoni)

    Microsoft Academic Search

    C. E. Reid; R. Hermes; S. Blottner; F. Goeritz; G. Wibbelt; C. Walzer; B. R. Bryant; T. J. Portas; W. J. Streich; T. B. Hildebrandt

    2009-01-01

    To increase the quality of cryopreserved sperm in white rhinoceros, the liquid nitrogen vapour (LN vapour) freezing and the multi-thermal gradient directional freezing methods were compared. Sixteen white rhinoceros (Ceratotherium simum sp.) were electro-ejaculated. Semen samples were diluted with cryoextender (Tris, lactose, egg-yolk, DMSO) and aliquoted into straws for LN vapour freezing, and glass hollow tubes for directional freezing. The

  13. Freeze Branding Horses 

    E-print Network

    Householder, Doug; Webb, Gary; Wigington, Sam; Bruemmer, Jason

    2001-06-29

    (like a clear straw) from the GF. On colored horses, pigment (black, brown, red, yellow, etc.) is added from the CF below the skin to the clear hairshaft, which gives the hair its color. When the intensely cold iron used in freeze branding is placed... site contains no pigment and appears white. This is the desired result?a uniform, white brand. If the iron is pressed to the skin for a shorter period of time and/or with less pressure than required, some hairs grow in colored and some hairs grow...

  14. Freeze Branding Horses

    E-print Network

    Householder, Doug; Webb, Gary; Wigington, Sam; Bruemmer, Jason

    2001-06-29

    , simpli- f_ied drawing of one hair shaft with its color (pigment) producing follicle (CF) and its growth follicle (GF), both shown below the skin. Doug Householder 1 , Gary Webb 2 , Sam Wigington 3 and Jason Bruemmer 4 Freeze Branding Horses Figure 1. Hair... manager, Horse Center, Department of Animal Science, Texas A&M University. Texas AgriLife Extension Service ? Zerle L. Carpenter, Director ? The Texas A&M University System ? College Station, Texas Under normal circumstances hair grows as a clear shaft...

  15. Vertical Bridgman growth of Al xGa 1- xSb single crystals

    NASA Astrophysics Data System (ADS)

    Huang, W. D.; Naritsuka, S.; Nishinaga, T.

    2000-06-01

    Al xGa 1- xSb crystals were grown by vertical Bridgman method with (1 1 1)B oriented GaSb seeds in a two-zone vertical gradient furnace. The growth was conducted using a two-step growth process, which consists of the growth under a constant temperature period and the growth in a vertical gradient freeze mode. During the period of the constant-temperature profile, the growth was realized by the transport of Al to the solid-liquid interface. Al xGa 1- xSb single crystals with a diameter of 14.5 mm and a length of more than 27 mm were successfully obtained in pyrolitic boron nitride (PBN) crucibles. The longitudinal cross sections were investigated by using a Nomarski differential interference contrast microscope (N-DICM) and it was found that strong striations were induced due to the convection on the ground. The AlSb distribution was measured by spatially resolved photoluminescence (SRPL) and it was found that AlSb composition reached 10.4%.

  16. Radiobrightness decision criteria for freeze/thaw boundaries

    NASA Technical Reports Server (NTRS)

    Zuerndorfer, B.; England, Anthony W.

    1992-01-01

    A freeze indicator (FI), based on a low 37-GHz radiobrightness and a low 10.7, 18, and 37-GHz radiobrightness spectral gradient, has been used to classify frozen surfaces in the northern Great Plains. By modeling the radiometer beampatterns as Gaussian, freeze/thaw boundaries can be located at the (fine) resolution of the 37-GHz channel. The performance of the freeze indicator, and subsequent boundary location estimate, depends on the accuracy of the boundary decision criteria. It is shown that decision criteria based on clustering and unsupervised classification yield good performance. A simple algorithm for registering coarse-resolution FI boundaries to equivalent boundaries in fine-resolution 37-GHz radiobrightness images is also presented.

  17. Droplet Freezing by Surface Nucleation

    Microsoft Academic Search

    Narayan R. Gokhale; James Goold Jr.

    1968-01-01

    Droplet freezing by surface nucleation has been observed during the course of studies of ice nucleation in our laboratories. A constant rate of cooling apparatus and a specially constructed cold chamber were used for this study. Silver iodide particles sprinkled on supercooled, millimeter-size water drops are effective in freezing the drops at 5C. Particles of naturally occurring silicates were found

  18. FREEZING RESISTANCE OF NEW ZEALAND TREES AND SHRUBS

    Microsoft Academic Search

    A. SAKAI; P. WARDLE

    SUMMARY: Forty-two native woody species were selected to represent the range of temperature-related ecological gradients in New Zealand. Twigs collected in July (mid-winter) were sent by air to Sapporo, Japan, where they were artificially hardened and then tested for freezing resistance. Although only one plant of each species was sampled from each site in anyone year, results were consistent from

  19. Thermal freeze-out versus chemical freeze-out reexamined

    E-print Network

    Dariusz Prorok

    2010-03-04

    An alternative, to the commonly used blast-wave, model describing the freeze-out hypersurface is applied to fit the $p_{T}$-spectra of identified hadrons measured at relativistic heavy-ion collisions at $\\sqrt{s_{NN}}=62.4, 130$ and 200 GeV. Decays of resonances are taken into account completely. It has turned out that the fitted freeze-out temperature and baryon number chemical potential depend weakly on the centrality of the collision and their values are close to the chemical freeze-out values determined from fits to particle yield ratios.

  20. 7.NS Comparing Freezing Points

    NSDL National Science Digital Library

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Ocean water freezes at about $-2 \\frac12 ^\\circ C$. Fresh water freezes at $0 ^\\circ C$. Antifreeze, a liquid used in the radiators of cars, freezes at...

  1. Commercial Application of Freeze Crystallization 

    E-print Network

    Gorgol, R. G.

    1992-01-01

    crystallization, low temperature operation, separation of organic and in-organic contaminants, can be put to use. Freeze crystallization can be applied both economically and practically for specific wastewater applications....

  2. Heritage roundtable: the nuclear freeze

    SciTech Connect

    Allen, R.V.; Gray, C.; Kalicki, J.; Pfaltzgraff, R.; Scoville, H.

    1982-01-01

    The transcript of a panel of foreign policy experts, chaired by former National Security Adviser Richard Allen, debates the proposed nuclear freeze. They consider whether a freeze is a step in the right direction, acting to slow the arms race and contribute to world security, or whether it would aggravate strategic problems by perpetuating an umbalanced situation. Disagreement among the participants makes clear that no one favors nuclear war, but there are differing perspectives on how to continue preventing such a war.

  3. Freezing behaviour of microencapsulated water.

    PubMed

    Yamane, H; Ohshima, H; Kondo, T

    1992-01-01

    The freezing behaviour of water in polyurea microcapsules was studied through DSC (differential scanning calorimetry) and ESR (electron spin resonance) measurements under a non-equilibrium condition to show that supercooling of water becomes more noticeable with decreasing droplet size of the liquid. Thermodynamics of small systems was found applicable to analyse the experimental findings, even though the process of water freezing in the microcapsules was not of an equilibrium nature. PMID:1328582

  4. The role of the geothermal gradient in the emplacement and replenishment of ground ice on Mars

    NASA Technical Reports Server (NTRS)

    Clifford, Stephen M.

    1993-01-01

    Knowledge of the mechanisms by which ground ice is emplaced, removed, and potentially replenished, are critical to understanding the climatic and hydrologic behavior of water on Mars, as well as the morphologic evolution of its surface. Because of the strong temperature dependence of the saturated vapor pressure of H2O, the atmospheric emplacement or replenishment of ground ice is prohibited below the depth at which crustal temperatures begin to monotonically increase due to geothermal heating. In contrast, the emplacement and replenishment of ground ice from reservoirs of H2O residing deep within the crust can occur by at least three different thermally-driven processes, involving all three phases of water. In this regard, Clifford has discussed how the presence of a geothermal gradient as small as 15 K/km can give rise to a corresponding vapor pressure gradient sufficient to drive the vertical transport of 1 km of water from a reservoir of ground water at depth to the base of the cryosphere every 10(exp 6) - 10(exp 7) years. This abstract expands on this earlier treatment by considering the influence of thermal gradients on the transport of H2O at temperatures below the freezing point.

  5. Geothermal Gradients

    NSDL National Science Digital Library

    Cameron Davidson

    In this problem set the students use two different equations to calculate a conductive geothermal gradient using a spreadsheet program like Excel. Once they have the geothermal gradient plotted, they are asked to experiment with and comment on the model by changing parameters (e.g. mantle heat flow, thermal conductivity). There is a mix of specific, fill in the blank questions and open-ended questions. This problem set helps develop quantitative problem solving skills using a spreadsheet as a tool, and forces students to think about thermal constraints during igneous and metamorphic processes.

  6. Heat freezes niche evolution.

    PubMed

    Araújo, Miguel B; Ferri-Yáñez, Francisco; Bozinovic, Francisco; Marquet, Pablo A; Valladares, Fernando; Chown, Steven L

    2013-09-01

    Climate change is altering phenology and distributions of many species and further changes are projected. Can species physiologically adapt to climate warming? We analyse thermal tolerances of a large number of terrestrial ectotherm (n = 697), endotherm (n = 227) and plant (n = 1816) species worldwide, and show that tolerance to heat is largely conserved across lineages, while tolerance to cold varies between and within species. This pattern, previously documented for ectotherms, is apparent for this group and for endotherms and plants, challenging the longstanding view that physiological tolerances of species change continuously across climatic gradients. An alternative view is proposed in which the thermal component of climatic niches would overlap across species more than expected. We argue that hard physiological boundaries exist that constrain evolution of tolerances of terrestrial organisms to high temperatures. In contrast, evolution of tolerances to cold should be more frequent. One consequence of conservatism of upper thermal tolerances is that estimated niches for cold-adapted species will tend to underestimate their upper thermal limits, thereby potentially inflating assessments of risk from climate change. In contrast, species whose climatic preferences are close to their upper thermal limits will unlikely evolve physiological tolerances to increased heat, thereby being predictably more affected by warming. PMID:23869696

  7. Barium titanate-polymer composites produced via directional freezing.

    PubMed

    Gorzkowski, Edward P; Pan, Ming-Jen

    2009-08-01

    In this study, we use a freeze casting technique to construct ceramic-polymer composites in which the 2 phases are arranged in an electrically parallel configuration. By doing so, the composites exhibit dielectric constant (K) up to 2 orders of magnitude higher than that of composites with ceramic particles randomly dispersed in a polymer matrix. In this technique, an aqueous ceramic slurry was frozen unidirectionally to form ice platelets and ceramic aggregates that were aligned in the temperature gradient direction. Upon freeze-drying, the ice platelets sublimed and left the lamellar ceramic structure intact. The green ceramic body was fired to retain the microstructure, and then the space between ceramic lamellae was infiltrated with a polymer material. The finished composites exhibit the high dielectric constant (1000) of ferroelectric ceramics while maintaining the unique properties of polymer materials such as graceful failure, low dielectric loss, and high dielectric breakdown. PMID:19686976

  8. Freeze Protection for Gasholders ESGI64 Freeze Protection in Gasholders

    E-print Network

    Purvis, Richard

    and National Grid wishes to inves- tigate whether circulation of the tank water without external heating could of "tank water" at the base which is below ground. At present freeze- protection is achieved by external capacity and National Grid wishes to investi- gate whether circulation of the tank water without external

  9. Freeze Crystallization Processes: Efficiency by Flexibility

    E-print Network

    Heist, J. A.; Barron, T. S.

    1983-01-01

    the entropy of the separation is less. 3) A heat pump is used in the freeze crystallization process to transfer heat from the freezer to the melter, providing advantages similar to the vapor compression evaporator cycle. Freeze crystallization should...

  10. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...590.536 Freezing operations. (a) Freezing rooms shall be kept clean and free from objectionable odors. (b) Requirements...d) The outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e)...

  11. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...590.536 Freezing operations. (a) Freezing rooms shall be kept clean and free from objectionable odors. (b) Requirements...d) The outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e)...

  12. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...590.536 Freezing operations. (a) Freezing rooms shall be kept clean and free from objectionable odors. (b) Requirements...d) The outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e)...

  13. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...590.536 Freezing operations. (a) Freezing rooms shall be kept clean and free from objectionable odors. (b) Requirements...d) The outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e)...

  14. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...590.536 Freezing operations. (a) Freezing rooms shall be kept clean and free from objectionable odors. (b) Requirements...d) The outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e)...

  15. Status of Chemical Freeze-Out

    E-print Network

    J. Cleymans; H. Oeschler; K. Redlich; S. Wheaton

    2006-07-14

    The status of the energy dependence of the chemical freeze-out temperature and chemical potential obtained in heavy ion collisions is presented. Recent proposals for chemical freeze-out conditions are compared.

  16. Bjorken expansion with gradual freeze out

    E-print Network

    V. K. Magas; L. P. Csernai; E. Molnar

    2007-02-27

    The freeze out of the expanding systems, created in relativistic heavy ion collisions, will be discussed. We combine kinetic freeze out equations with Bjorken type system expansion into a unified model. Such a model is a more physical generalization of the earlier simplified non-expanding freeze out models. We shall see that the basic freeze out features, pointed out in the earlier works, are not smeared out by the expansion.

  17. Temperature gradients, not food resource gradients, affect growth rate of migrating Daphnia mendotae in Lake Michigan

    Microsoft Academic Search

    Kevin L. Pangle; Scott D. Peacor

    2010-01-01

    Zooplankton production plays a critical role in the Great Lakes ecosystem, and vertical migration, which is exhibited by many zooplankton species, could affect production. We examined the effects of water temperature and food resource gradients on the growth rate of zooplankton undergoing vertical migration in Lake Michigan. In three laboratory experiments, juvenile Daphnia mendotae, native herbivorous cladocerans, were incubated for

  18. Combined infrared and freeze-drying.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The drying of the combined infrared (IR) and freeze-drying of food materials has been shown to be very rapid compared to regular freeze drying (FD). The resulting tissue structure of products processed with sequential infrared and freeze drying (SIRFD) tends to have higher crispness than those proce...

  19. TISSUE FREEZING METHODS FOR CRYOSTAT SECTIONING

    E-print Network

    Chisholm, Rex L.

    TISSUE FREEZING METHODS FOR CRYOSTAT SECTIONING Basic Tissue Freezing Methods Preparing Tissue-Roll Plate; Speaker: Donna J. Emge, HT-ASCP, MHPL Manager #12;Preparing Tissue For Freezing Tissue morphological distortions and damage due to: · Tissue drying artifact. · Autolysis - The destruction of tissues

  20. Vertical Farm

    NSDL National Science Digital Library

    2004-01-01

    With the continued growth of the human population of the Earth, there is increasing concern with the planet's ability to provide sustenance for all of its inhabitants. This compelling website by Dickson Despommier and his colleagues at Columbia University provides a worthy alternative to other forms of agriculture: the vertical farm. As Dr. Despommier notes on the site, "..they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming." The site offers a great deal of information about these vertical farms, a detailed essay on the importance of such farms, a number of potential designs, and a discussion forum. Finally, there are a number of plans that indicate how this type of farm might be effectively created and sustained.

  1. Preparation of porous scaffolds by using freeze-extraction and freeze-gelation methods

    Microsoft Academic Search

    Ming-Hua Ho; Pei-Yun Kuo; Hsyue-Jen Hsieh; Tzu-Yang Hsien; Lein-Tuan Hou; Juin-Yih Lai; Da-Ming Wang

    2004-01-01

    Freeze-fixation and freeze-gelation methods are presented in this paper which can be used to prepare highly porous scaffolds without using the time and energy consuming freeze-drying process. The porous structure was generated during the freeze of a polymer solution, following which either the solvent was extracted by a non-solvent or the polymer was gelled under the freezing condition; thus, the

  2. Mapping freeze/thaw boundaries with SMMR data

    NASA Technical Reports Server (NTRS)

    Zuerndorfer, B. W.; England, A. W.; Dobson, M. C.; Ulaby, F. T.

    1989-01-01

    Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) data are used to map daily freeze/thaw patterns in the upper Midwest for the Fall of 1984. The combination of a low 37 GHz radiobrightness and a negative 10.7, 18, and 37 GHz spectral gradient, Partial Derivative of Tb with Respect to f, appears to be an effective discriminant for classifying soil as frozen or thawed. The 37 GHz emissivity is less sensitive to soil moisture than are the lower frequency emissivities so that the 37 GHz radiobrightness appears to track soil surface temperature relatively well. The negative gradient for frozen ground is a consequence of volume scatter darkening at shorter microwave wavelengths. This shorter wavelength darkening is not seen in thawed moist soils.

  3. Commercial Application of Freeze Crystallization

    E-print Network

    Gorgol, R. G.

    begun to realize water is a very valuable resource. Even municipalities must husband thcir water. The day is coming very soon when all industrywill produce clean water as a cash product and water use will be carefully managed. Everywhere you look... becn since the world bcgan. The most noticeable frozen substance is, of course, water. Snow, ice cubcs, frozen lakes and streams, even iccbcrgs are all evidences of the freezing process at work. This process is also used to form crystalline...

  4. Freezing Poultry for Home Use

    E-print Network

    Davis, Michael

    2006-08-31

    . ? As you work, keep the cutting surface and utensils clean. ? Work quickly and place the poultry in the freezer as quickly as possible. ? Do not let raw poultry juices contaminate ready-to-eat foods. Answering the following questions will help you decide... airtight packaging when freezing poultry. Airtight packaging prevents dehydration and freezer burn. It also helps prevent fat rancidity, oxidation, spoilage, and the growth of disease-causing bacteria. Shrink packages, like the bags in which frozen...

  5. The vertical profile of radar reflectivity of convective cells: A strong indicator of storm intensity and lightning probability?

    NASA Technical Reports Server (NTRS)

    Zipser, Edward J.; Lutz, Kurt R.

    1994-01-01

    Reflectivity data from Doppler radars are used to construct vertical profiles of radar reflectivity (VPRR) of convective cells in mesoscale convective systems (MCSs) in three different environmental regimes. The National Center for Atmospheric Research CP-3 and CP-4 radars are used to calculate median VPRR for MCSs in the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central in 1985. The National Oceanic and Atmospheric Administration-Tropical Ocean Global Atmosphere radar in Darwin, Australia, is used to calculate VPRR for MCSs observed both in oceanic, monsoon regimes and in continental, break period regimes during the wet seasons of 1987/88 and 1988/89. The midlatitude and tropical continental VPRRs both exhibit maximum reflectivity somewhat above the surface and have a gradual decrease in reflectivity with height above the freezing level. In sharp contrast, the tropical oceanic profile has a maximum reflectivity at the lowest level and a very rapid decrease in reflectivity with height beginning just above the freezing level. The tropical oceanic profile in the Darwin area is almost the same shape as that for two other tropical oceanic regimes, leading to the conclustion that it is characteristic. The absolute values of reflectivity in the 0 to 20 C range are compared with values in the literature thought to represent a threshold for rapid storm electrification leading to lightning, about 40 dBZ at -10 C. The large negative vertical gradient of reflectivity in this temperature range for oceanic storms is hypothesized to be a direct result of the characteristically weaker vertical velocities observed in MCSs over tropical oceans. It is proposed, as a necessary condition for rapid electrification, that a convective cell must have its updraft speed exceed some threshold value. Based upon field program data, a tentative estimate for the magnitude of this threshold is 6-7 m/s for mean speed and 10-12 m/s for peak speed.

  6. Gravity gradient determination with tethered systems

    NASA Technical Reports Server (NTRS)

    Kalaghan, P. M.; Colombo, G.

    1978-01-01

    A detailed investigation of the Earth's gravity field is needed for application to modern solid earth and oceanic investigations. The use of gravity gradiometers presents a technique to measure the intermediate wavelength components of the gravity field. One configuration of a gradiometer involves a tethered pair of masses orbiting the Earth and stabilized by vertical gravity gradient of the earth. A mesurement of the tension in such a system, called the DUMBBELL system is described. It allows the determination of the vertical gradient of the anomalous component of the Earth's gravtiy field. Preliminary analysis of the dynamics, mechanization, expected signal levels and noise environment indicates that the Dumbbell system is feasible.

  7. Accurate pressure gradient calculations in hydrostatic atmospheric models

    NASA Technical Reports Server (NTRS)

    Carroll, John J.; Mendez-Nunez, Luis R.; Tanrikulu, Saffet

    1987-01-01

    A method for the accurate calculation of the horizontal pressure gradient acceleration in hydrostatic atmospheric models is presented which is especially useful in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The present method is shown to be exact if the potential temperature lapse rate is constant between the vertical pressure integration limits. The technique is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. A fixed vertical grid and a dynamic grid defined by the significant levels in the vertical temperature distribution are employed.

  8. A study of slag freezing in metallurgical furnaces

    NASA Astrophysics Data System (ADS)

    Guevara, Fernando

    Many smelting and slag-cleaning furnaces operate with cooling systems designed to freeze a slag layer over the refractory to protect it. The fluid flow and heat transfer conditions associated with the freeze layer and mushy zones are poorly understood. This study was conducted to understand the chill layer formation and heat transfer that is required to design cooling systems in pyrometallurgical operations where a slag layer is required to protect the furnace wall. The freeze layer formation and heat transfer in mushy zones were experimentally study at room temperature in a 2-dimensional square cavity differentially heated, using an aqueous solution of calcium chloride to simulate the slag. Reasonable similarity with conditions encountered with copper and nickel smelting systems was achieved (Pr ? 50 and Ra ? 108, in the laminar-turbulent transition). Measurements of velocities were made with the Particle Image Velocimetry (PIV) technique. The freeze layer development was tracked using a digital camera. Direct Numerical Simulations (DNS) of the mean flow using a finite control volume technique with a fixed domain method were also made of the unsteady fluid flow and heat transfer problem. It was found that the macro solidification process is well described using an improved model for high molecular viscosity in the mushy zone. Solid front growth, isothermal profiles, velocity profiles and heat transfer through the walls showed good agreement between the PIV and DNS results. Experimental and numerical velocity profiles close to the freeze layer show a parabolic behaviour in the vertical velocity profile which is completely different from the calculation of heat transfer using a sharp interface model. The reason for this is attributed to the effects of the mushy zone with a high viscosity and high shear stresses acting on that area. In Part III of this Thesis, effects of slag viscosity temperature relationship were analysed with a two-dimensional mathematical model of an electric smelting furnace. The model was focused on the fluid dynamics of the molten slag and the effects over the formation of magnetite-rich slag layer over the walls. The results of the previous experimental and mathematical work, Part I and II, were used to describe mathematically the freeze layer formation on the furnace walls using a fixed-grid model from a highly viscous liquid. Chemical composition of the slag was taken into account through the effect of the viscous activation energy as well the solidus and liquidus temperatures. The results show that the flow pattern is strongly affected in the areas of high viscosity. The results are discussed in terms of heat flux over the refractories and their effects on cooling system design.

  9. Development and design of sludge freezing beds

    SciTech Connect

    Martel, C.J.

    1987-01-01

    The purpose of this study was to develop design criteria for a new sludge dewatering unit operation called a sludge freezing bed. This bed uses natural freeze-thaw to condition the sludge for dewatering. The total depth of sludge which can be frozen, thawed and dewatered by this process in a year is the main criterion needed for design. The essential features of a freezing bed which would optimize natural freeze-thaw were identified through a literature review and site visits. Several laboratory tests were conducted to assess the dewaterability of freeze-thaw conditioned sludge at various depths. Water treatment plant sludge and both anaerobically and aerobically digested wastewater sludges were used in these tests. Mathematical models for predicting the design depth were developed and validated with data from other sludge freezing operations. Values for the input parameters to the models were obtained from the literature or from laboratory and pilot-scale experiments.

  10. Freeze-Drying Characteristics of Tropical Fruits

    Microsoft Academic Search

    Ana M. Silveira; José T. Freire

    2006-01-01

    The objective of this work was to experimentally determine physical properties such as apparent densities, real densities, and porosity of freeze-dried tropical fruits pulps such as pineapple, Barbados cherry, guava, papaya, and mango, and to carry out nutritional analysis of vitamin C, calcium, and phosphorus in the freeze-dried and in natura pulps. The freeze-dried pulps presented low apparent density and

  11. Fundamental Technical Elements of Freeze-fracture/Freeze-etch in Biological Electron Microscopy

    EPA Science Inventory

    Freeze-fracture/freeze-etch describes a process whereby specimens, typically biological or nanomaterial in nature, are frozen, fractured, and replicated to generate a carbon/platinum "cast" intended for examination by transmission electron microscopy. Specimens are subjected to u...

  12. Freeze Enhanced Halate Halide Reactions

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Weaver, K.; Broderick, A.

    2014-12-01

    Relatively little is known about halate ion species (XO3-; X = I, Br, Cl) in atmospheric condensed phases. It was initial thought that iodate was a terminal stable species upon iodide oxidation. However, it is becoming increasingly recognized that reactions involving iodate can lead to reactive iodine, and this chemistry is accelerated under acidic conditions. The environmental concentrations and chemistry of bromate and chlorate are largely unexplored in environmental ices. We present results from a series of aqueous phase halate ion reactions with halides under acidic conditions, showing that the kinetics are strongly enhanced upon freezing. The products of these reactions are reactive halogens, which have important implications to marine boundary layer chemistry.

  13. Freeze out in narrow and wide layers

    E-print Network

    V. K. Magas; L. P. Csernai; E. Molnar

    2006-01-19

    The freeze out of particles from a layer of finite thickness is discussed in a phenomenological kinetic model. The proposed model, based on the Modified Boltzman Transport Equation, is Lorentz invariant and can be applied equally well for the freeze out layers with space-like and time-like normal vectors. It leads to non-equilibrated post freeze out distributions. The dependence of the resulting distribution on the thickness of the layer is presented and discussed for a space-like freeze out scenario.

  14. Reptile freeze tolerance: metabolism and gene expression.

    PubMed

    Storey, Kenneth B

    2006-02-01

    Terrestrially hibernating reptiles that live in seasonally cold climates need effective strategies of cold hardiness to survive the winter. Use of thermally buffered hibernacula is very important but when exposure to temperatures below 0 degrees C cannot be avoided, either freeze avoidance (supercooling) or freeze tolerance strategies can be employed, sometimes by the same species depending on environmental conditions. Several reptile species display ecologically relevant freeze tolerance, surviving for extended times with 50% or more of their total body water frozen. The use of colligative cryoprotectants by reptiles is poorly developed but metabolic and enzymatic adaptations providing anoxia tolerance and antioxidant defense are important aids to freezing survival. New studies using DNA array screening are examining the role of freeze-responsive gene expression. Three categories of freeze responsive genes have been identified from recent screenings of liver and heart from freeze-exposed (5h post-nucleation at -2.5 degrees C) hatchling painted turtles, Chrysemys picta marginata. These genes encode (a) proteins involved in iron binding, (b) enzymes of antioxidant defense, and (c) serine protease inhibitors. The same genes were up-regulated by anoxia exposure (4 h of N2 gas exposure at 5 degrees C) of the hatchlings which suggests that these defenses for freeze tolerance are aimed at counteracting the injurious effects of the ischemia imposed by plasma freezing. PMID:16321368

  15. Estimation of coastal density gradients

    NASA Astrophysics Data System (ADS)

    Howarth, M. J.; Palmer, M. R.; Polton, J. A.; O'Neill, C. K.

    2012-04-01

    Density gradients in coastal regions with significant freshwater input are large and variable and are a major control of nearshore circulation. However their measurement is difficult, especially where the gradients are largest close to the coast, with significant uncertainties because of a variety of factors - spatial and time scales are small, tidal currents are strong and water depths shallow. Whilst temperature measurements are relatively straightforward, measurements of salinity (the dominant control of spatial variability) can be less reliable in turbid coastal waters. Liverpool Bay has strong tidal mixing and receives fresh water principally from the Dee, Mersey, Ribble and Conwy estuaries, each with different catchment influences. Horizontal and vertical density gradients are variable both in space and time. The water column stratifies intermittently. A Coastal Observatory has been operational since 2002 with regular (quasi monthly) CTD surveys on a 9 km grid, an situ station, an instrumented ferry travelling between Birkenhead and Dublin and a shore-based HF radar system measuring surface currents and waves. These measurements are complementary, each having different space-time characteristics. For coastal gradients the ferry is particularly useful since measurements are made right from the mouth of Mersey. From measurements at the in situ site alone density gradients can only be estimated from the tidal excursion. A suite of coupled physical, wave and ecological models are run in association with these measurements. The models, here on a 1.8 km grid, enable detailed estimation of nearshore density gradients, provided appropriate river run-off data are available. Examples are presented of the density gradients estimated from the different measurements and models, together with accuracies and uncertainties, showing that systematic time series measurements within a few kilometres of the coast are a high priority. (Here gliders are an exciting prospect for detailed regular measurements to fill this gap.) The consequences for and sensitivity of circulation estimates are presented using both numerical and analytic models.

  16. Split-sample comparison of directional and liquid nitrogen vapour freezing method on post-thaw semen quality in white rhinoceroses (Ceratotherium simum simum and Ceratotherium simum cottoni).

    PubMed

    Reid, C E; Hermes, R; Blottner, S; Goeritz, F; Wibbelt, G; Walzer, C; Bryant, B R; Portas, T J; Streich, W J; Hildebrandt, T B

    2009-01-15

    To increase the quality of cryopreserved sperm in white rhinoceros, the liquid nitrogen vapour (LN vapour) freezing and the multi-thermal gradient directional freezing methods were compared. Sixteen white rhinoceros (Ceratotherium simum sp.) were electro-ejaculated. Semen samples were diluted with cryoextender (Tris, lactose, egg-yolk, DMSO) and aliquoted into straws for LN vapour freezing, and glass hollow tubes for directional freezing. The sperm quality was evaluated before and after freezing by assessing the following parameters: motility, morphologic state, acrosomal integrity and plasma membrane function and integrity (i.e. sperm viability) as defined by the hypo-osmotic swelling. Directional freezing improved the sperm viability by 5.6% (p<0.005), progressive motility score by 34.7% and sperm motility index (SMI) by 8.1% (p<0.005) versus LN vapour freezing. When data was categorized into groups of low (<19%), moderate (20-39%) and high (>40%) percentages of morphologically normal, directional freezing (DF) resulted in 31.4% less abnormal acrosomes for the low quality group as well as 18.7% increase in intact acrosomes and 10.9% increase in motility for the high quality group compared to LN vapour freezing (LN) (p<0.01, p<0.03, p<0.01, respectively). LN showed a significant reduction in sperm head volume (5.7%, p<0.05) compared to the prefreeze; whereas, no significant reduction in head volume was demonstrated after DF. Several additives (xanthenuric acid, cytochalasin D, potassium, EDTA) to the basic cryoextender provided no significant improvement in spermatozoal survival after directional freezing. In conclusion, directional freezing proved to facilitate higher gamete survival compared to LN vapour freezing. This is especially effective in ejaculates of low sperm quality and is important in endangered species where high quality semen donors are often not accessible. These results suggest that directional freezing could be valuable particularly for species with limited freezability of spermatozoa. PMID:18775559

  17. TEMPERATURE AND PRESSURE GRADIENTS IN GAS WELLS

    Microsoft Academic Search

    M. R. Teck; Donald Katz; Jack Elenbaas; Michael Whims; Joseph Roberts

    1978-01-01

    A stepwise procedure has been developed for successsive calculation of pressure and temperature gradients in gas wells during production or injection. The method, based on a thermodynamic energy balance in the well bore and the usual equations for the flow of natural gas in vertical pipe, is shown to give reasonably accurate predictions when evaluated on the basis of actual

  18. The effect of density gradients on hydrometers

    Microsoft Academic Search

    Martti Heinonen; Sampo Sillanpää

    2003-01-01

    Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer

  19. Improving Forecasts of Freezing Rain at ECMWF

    NASA Astrophysics Data System (ADS)

    Tsonevsky, Ivan; Forbes, Richard; Hewson, Tim

    2015-04-01

    Freezing rain events, though relatively rare, can be extremely debilitating and dangerous for society, with recovery times of order months or even years. Analysis of forecasts of past events by the operational ECMWF Integrated Forecast System (IFS) showed a strong tendency to incorrectly represent freezing rain as snow. Investigations highlighted that this was primarily because the re-freezing process in IFS, following hydrometeors as they descend, was parametrised with the same time-scale as the melting process. In reality the time-scale for re-freezing should, in general, be much longer. The model physics were changed accordingly, and the results in terms of forecast quality were positive and very striking. Coupled with these physics changes new IFS output was developed for users which shows precipitation type at the surface (rain, snow, wet snow, sleet, freezing rain, ice pellets). The changes to the physics will be described in detail, and their impact will be illustrated by comparing forecast output for past events in new and old model versions, in terms of precipitation type and intensity. Illustrations will include short-range deterministic forecasts from 'HRES' (the high resolution ECMWF model), and longer range probabilistic forecasts of freezing rain occurrence from the ensemble. There will also be reference to issues requiring further work/investigation, such as high level convection in potential freezing rain cases, freezing drizzle generated in supercooled shallow clouds, and IFS retention of the 'warm nose' in which melting occurs.

  20. Modeling frost heave in freezing soils

    Microsoft Academic Search

    Leonid Bronfenbrener; Regina Bronfenbrener

    2010-01-01

    A generalized model for secondary frost heave in freezing fine-grained soils is presented. The cryostatic suction effect, which causes an increase in upward water permeation, ice-lens growth during freezing, and, as a consequence, the increase of soil heave, is considered to be the main mechanism of moisture transfer. Although the model in this paper has a number of approaches in

  1. Freezing: an underutilized food safety technology?

    PubMed

    Archer, Douglas L

    2004-01-15

    Freezing is an ancient technology for preserving foods. Freezing halts the activities of spoilage microorganisms in and on foods and can preserve some microorganisms for long periods of time. Frozen foods have an excellent overall safety record. The few outbreaks of food-borne illness associated with frozen foods indicate that some, but not all human pathogens are killed by commercial freezing processes. Freezing kills microorganisms by physical and chemical effects and possibly through induced genetic changes. Research is needed to better understand the physical and chemical interactions of various food matrices with the microbial cell during freezing and holding at frozen temperatures. The literature suggests that many pathogenic microorganisms may be sublethally injured by freezing, so research should be done to determine how to prevent injured cells from resuscitating and becoming infectious. Studies on the genetics of microbial stress suggest that the induction of resistance to specific stresses may be counteracted by, for example, simple chemicals. Research is needed to better understand how resistance to the lethal effect of freezing is induced in human pathogens and means by which it can be counteracted in specific foods. Through research, it seems possible that freezing may in the future be used to reliably reduce populations of food-borne pathogens as well as to preserve foods. PMID:14698095

  2. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7...DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze treatment requirements. Quick freeze...

  3. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7...DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze treatment requirements. Quick freeze...

  4. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7...DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze treatment requirements. Quick freeze...

  5. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7...DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze treatment requirements. Quick freeze...

  6. Mesoscale monitoring of the soil freeze/thaw boundary from orbital microwave radiometry

    NASA Technical Reports Server (NTRS)

    Dobson, Craig; Ulaby, Fawwaz T.; Zuerndorfer, Brian; England, Anthony W.

    1990-01-01

    A technique was developed for mapping the spatial extent of frozen soils from the spectral characteristics of the 10.7 to 37 GHz radiobrightness. Through computational models for the spectral radiobrightness of diurnally heated freesing soils, a distinctive radiobrightness signature was identified for frozen soils, and the signature was cast as a discriminant for unsupervised classification. In addition to large area images, local area spatial averages of radiobrightness were calculated for each radiobrightness channel at 7 meteorologic sites within the test region. Local area averages at the meteorologic sites were used to define the preliminary boundaries in the Freeze Indicator discriminate. Freeze Indicator images based upon Nimbus 7, Scanning Multichannel Microwave Radiometer (SMMR) data effectively map temporal variations in the freeze/thaw pattern for the northern Great Plains at the time scale of days. Diurnal thermal gradients have a small but measurable effect upon the SMMR spectral gradient. Scale-space filtering can be used to improve the spatial resolution of a freeze/thaw classified image.

  7. Mesoscale monitoring of the soil freeze/thaw boundary from orbital microwave radiometry

    NASA Astrophysics Data System (ADS)

    Dobson, Craig; Ulaby, Fawwaz T.; Zuerndorfer, Brian; England, Anthony W.

    1990-02-01

    A technique was developed for mapping the spatial extent of frozen soils from the spectral characteristics of the 10.7 to 37 GHz radiobrightness. Through computational models for the spectral radiobrightness of diurnally heated freesing soils, a distinctive radiobrightness signature was identified for frozen soils, and the signature was cast as a discriminant for unsupervised classification. In addition to large area images, local area spatial averages of radiobrightness were calculated for each radiobrightness channel at 7 meteorologic sites within the test region. Local area averages at the meteorologic sites were used to define the preliminary boundaries in the Freeze Indicator discriminate. Freeze Indicator images based upon Nimbus 7, Scanning Multichannel Microwave Radiometer (SMMR) data effectively map temporal variations in the freeze/thaw pattern for the northern Great Plains at the time scale of days. Diurnal thermal gradients have a small but measurable effect upon the SMMR spectral gradient. Scale-space filtering can be used to improve the spatial resolution of a freeze/thaw classified image.

  8. Method for controlling the vertical growth of hydraulic fractures

    Microsoft Academic Search

    J. L. Fitch; M. K. Strubhar

    1985-01-01

    A method for controlling the vertical growth of hydraulic fractures in subterranean formations. The fracturing gradients of adjacent formations are determined. The fluid density necessary to inhibit the propagation of a hydraulic fracture from one adjacent formation into the other is determined from the fracturing gradients. A fracturing fluid is prepared having the necessary density for inhibiting such hydraulic fracture

  9. Crosswind Shear Gradient Affect on Wake Vortices

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.; Ahmad, Nashat N.

    2011-01-01

    Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

  10. Fish With Nature's Anti-freeze

    NSDL National Science Digital Library

    Using this material, students will discover that under special experimental conditions, fish have been observed functioning in ice-free cold salt water at a temperature of -6 degrees Centigrade. Research has found that these fish have eight types of anti-freeze molecules which bathe the interior surface of their skin, acting as a barrier to ice propagating in from outside. When the anti-freeze molecules are not present, ice filters through their skin at these temperatures and crystallizes (freezes) their blood and tissues. Students will experiment with lowering the freezing point of a substance, thus causing it to remain liquid at a temperature when it is normally solid. Students will compare their findings with facts about Antarctic ice-fish, which have bodily fluids that remain liquid at temperatures below freezing.

  11. Effective anisotropy gradient in pressure graded [Co/Pd] multilayers

    NASA Astrophysics Data System (ADS)

    Kirby, B. J.; Greene, P. K.; Maranville, B. B.; Davies, J. E.; Liu, Kai

    2015-02-01

    We have used polarized neutron reflectometry to show that controlled variation of growth pressure during deposition of Co/Pd multilayers can be used to achieve a significant vertical gradient in the effective anisotropy. This gradient is strongly dependent on deposition order (low to high pressure or vice versa), and is accompanied by a corresponding gradient in saturation magnetization. These results demonstrate pressure-grading as an attractively simple technique for tailoring the anisotropy profile of magnetic media.

  12. Can Propagation of Gas Bubbles Lead to Detached Solidification? Experiments on Freezing of Water

    NASA Technical Reports Server (NTRS)

    Wang, Yazhen; Regel, Liya; Wilcox, William R.

    2002-01-01

    A vertical Bridgman-Stockbarger apparatus was used to directionally solidify water upward, in the hope that detached solidification would evolve from gas bubbles forming on the wall. A large contact angle of the water on the ampoule wall and a high solubility of the dissolved gas caused gas bubbles or tubes to form only at the ampoule wall, and not in the interior. Gas tubes were often nearly periodically spaced around the ampoule wall, with a spacing that increased with ampoule diameter and decreased with freezing rate. The width of the gas tubes was nearly independent of the ampoule diameter and freezing rate. A high degree of detachment was obtained with a rough, nonwetting coating on the ampoule wall, but full detachment was not achieved. This indicates that detachment does not occur by propagation of a single gas bubble around the periphery of the freezing interface. The convection near the freezing interface influenced gas bubble formation, and was outward for a concave freezing interface and inward for a convex interface.

  13. Atmospheric HT and HTO 3. Vertical Transport of Water in the Stratosphere

    Microsoft Academic Search

    Allen S. Mason; H. Göte Östlund

    1976-01-01

    A series of sampling flights was made to determine the vertical distribution of HT and HTO in the upper troposphere and lower stratosphere up to 18-km altitude. The HT appears to be well mixed, but striking vertical gradients of HTO were found in the region from 10 to 18 km. These gradients, essentially constant to 18 km, were used to

  14. Spray-freezing freeze substitution (SFFS) of cell suspensions for improved preservation of ultrastructure.

    PubMed

    Fields, S D; Strout, G W; Russell, S D

    1997-08-01

    Some unicellular organisms present challenges to chemical fixations that lead to common, yet obvious, artifacts. These can be avoided in entirety by adapting spray-freezing technology to ultrarapidly freeze specimens for freeze substitution. To freeze specimens, concentrated suspensions of cells ranging in diameter from 0.5-30 pm were sprayed with an airbrush at 140-200 kPa (1.05-1.5 torr; 20.3-29.0 psi) into a nylon mesh transfer basket submerged in liquid propane. After freezing, the mesh basket containing the frozen sample was lifted out of the chamber, drained and transferred through several anhydrous acetone rinses at 188 K (-85 degrees C). Freeze substitution was conducted in 1% tannic acid/1% anhydrous glutaraldehyde in acetone at 188 K (-85 degrees C), followed by 1% OsO4/acetone at 277 K (4 degrees C). Freeze substitution was facilitated using a shaking table to provide gentle mixing of the substitution medium on dry ice. High quality freezing was observed in 70% of spray-frozen dinoflagellate cells and in 95% of spray-frozen cyanobacterial cells. These could be infiltrated and observed directly; however, overall ultrastructural appearance and membrane contrast were improved when the freeze-substituted cells were rehydrated and post-fixed in aqueous OSO4, then dehydrated and embedded in either Spurr's or Epon resin. Ultrastructural preservation using this ultrarapid freezing method provided specimens that were consistently superior to those obtainable in even the best comparable chemical fixations. PMID:9264343

  15. Shadowgraph Study of Gradient Driven Fluctuations

    NASA Technical Reports Server (NTRS)

    Cannell, David; Nikolaenko, Gennady; Giglio, Marzio; Vailati, Alberto; Croccolo, Fabrizio; Meyer, William

    2002-01-01

    A fluid or fluid mixture, subjected to a vertical temperature and/or concentration gradient in a gravitational field, exhibits greatly enhanced light scattering at small angles. This effect is caused by coupling between the vertical velocity fluctuations due to thermal energy and the vertically varying refractive index. Physically, small upward or downward moving regions will be displaced into fluid having a refractive index different from that of the moving region, thus giving rise to the enhanced scattering. The scattered intensity is predicted to vary with scattering wave vector q, as q(sup -4), for sufficiently large q, but the divergence is quenched by gravity at small q. In the absence of gravity, the long wavelength fluctuations responsible for the enhanced scattering are predicted to grow until limited by the sample dimensions. It is thus of interest to measure the mean-squared amplitude of such fluctuations in the microgravity environment for comparison with existing theory and ground based measurements. The relevant wave vectors are extremely small, making traditional low-angle light scattering difficult or impossible because of stray elastically scattered light generated by optical surfaces. An alternative technique is offered by the shadowgraph method, which is normally used to visualize fluid flows, but which can also serve as a quantitative tool to measure fluctuations. A somewhat novel shadowgraph apparatus and the necessary data analysis methods will be described. The apparatus uses a spatially coherent, but temporally incoherent, light source consisting of a super-luminescent diode coupled to a single-mode optical fiber in order to achieve extremely high spatial resolution, while avoiding effects caused by interference of light reflected from the various optical surfaces that are present when using laser sources. Results obtained for a critical mixture of aniline and cyclohexane subjected to a vertical temperature gradient will be presented. The sample was confined between two horizontal parallel sapphire plates with a vertical spacing of 1 mm. The temperatures of the sapphire plates were controlled by independent circulating water loops that used Peltier devices to add or remove heat from the room air as required. For a mixture with a temperature gradient, two effects are involved in generating the vertical refractive index gradient, namely thermal expansion and the Soret effect, which generates a concentration gradient in response to the applied temperature gradient. For the aniline/cyclohexane system, the denser component (aniline) migrates toward the colder surface. Consequently, when heating from above, both effects result in the sample density decreasing with altitude and are stabilizing in the sense that no convective motion occurs regardless of the magnitude of the applied temperature gradient. The Soret effect is strong near a binary liquid critical point, and thus the dominant effect is due to the induced concentration gradient. The results clearly show the divergence at low q and the predicted gravitational quenching. Results obtained for different applied temperature gradients at varying temperature differences from the critical temperature, clearly demonstrate the predicted divergence of the thermal diffusion ratio. Thus, the more closely the critical point is approached, the smaller becomes the temperature gradient required to generate the same signal. Two different methods have been used to generate pure concentration gradients. In the first, a sample cell was filled with a single fluid, ethylene glycol, and a denser miscible fluid, water, was added from below thus establishing a sharp interface to begin the experiment. As time went on the two fluids diffused into each other, and large amplitude fluctuations were clearly observed at low q. The effects of gravitational quenching were also evident. In the second method, the aniline/cyclohexane sample was used, and after applying a vertical temperature gradient for several hours, the top and bottom temperatures were set equal and the thermal

  16. Exploring the Nature of Contact Freezing

    NASA Astrophysics Data System (ADS)

    Kiselev, A. A.; Hoffmann, N.; Duft, D.; Leisner, T.

    2012-12-01

    The freezing of supercooled water droplets upon contact with aerosol particles (contact nucleation of ice) is the least understood mechanism of ice formation in atmospheric clouds. Although experimental evidences suggest that some aerosols can be better IN in the contact than in the immersion mode (that is, triggering ice nucleation at higher temperature), no final explanation of this phenomena currently exists. On the other hand, the contact freezing is believed to be responsible for the enhanced rate of secondary ice formation occasionally observed in LIDAR measurements in the cold mixed phase clouds. Recently we have been able to show that the freezing of supercooled droplets electrodynamically levitated in the laminar flow containing mineral dust particles (kaolinite) is a process solely governed by a rate of collisions between the supercooled droplet and the aerosol particles. We have shown that the probability of droplet freezing on a single contact with aerosol particle may differ over an order of magnitude for kaolinite particles having different genesis and morphology. In this presentation we extend the study of contact nucleation of ice and compare the IN efficiency measured for DMA-selected kaolinite, illite and hematite particles. We show that the freezing probability increases towards unity as the temperature decreases and discuss the functional form of this temperature dependence. We explore the size dependence of the contact freezing probability and show that it scales with the surface area of the particles, thus resembling the immersion freezing behavior. However, for all minerals investigated so far, the contact freezing has been shown to dominate over immersion freezing on the short experimental time scales. Finally, based on the combined ESEM and electron microprobe analysis, we discuss the significance of particle morphology and variability of chemical composition on its IN efficiency in contact mode.

  17. Freeze/thaw and soil moisture effects on wind erosion

    NASA Astrophysics Data System (ADS)

    Wang, L.; Shi, Z. H.; Wu, G. L.; Fang, N. F.

    2014-02-01

    Wind erosion is very pronounced in semiarid regions during late winter-early spring and has major impacts on regional desertification and agriculture. In order to identify the effects of freeze/thaw and soil moisture on wind erosion, wind tunnel experiments were conducted to compare wind erosion effects under various soil moisture gradients in frozen and thawed soil. The variation of surface soil moisture after wind erosion and the effective soil particle size distribution was tested to explain the differences. The results showed that surface soil moisture content decreased in thawed soil and increased in frozen soil after wind erosion. The mean weight diameter, which increased with increasing soil moisture, was smaller in thawed soil than in frozen soil. The wind-driven sediment flux of frozen and thawed soil both decreased with increasing moisture, owing to the heavier soil particle weight and stronger interparticle bonding forces. The critical soil moisture content for suppressing wind erosion was around 2.34% for frozen soil and around 2.61% for thawed soil. The wind-driven sediment flux of thawed soil was always larger than that of frozen soil at the same moisture content, but this difference became negligible at moisture contents above 3.38%. We may speculate that wind erosion will be more severe in the future because of the lower soil moisture content and fewer soil freezing days as a result of global warming.

  18. The Effect of Soil Freezing on N Cycling: Comparison of two Headwater Subcatchments With Varying Snowpack, Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Christopher, S. F.; Shibata, H.; Ozawa, M.; Nakagawa, Y.; Mitchell, M.

    2006-12-01

    Climate change models predict the snowpacks of temperate forests will develop later and be shallower resulting in a higher propensity for soil freezing. In the northern most island of Japan, Hokkaido, snowpack depth decreases from west to east. This snowpack depth gradient provided a unique opportunity to test the effects of variable snowpack and soil freezing on N cycling. The Upper Nakagawa catchment (UN) in Shibecha Experimental Forest, eastern Hokkaido had a mean annual NO3- concentration of 2 mg N L-1 and had deciduous trees while the M3 catchment in Uryu Experimental Forest, western Hokkaido had a mean annual NO3- concentration of 0.1 mg N L-1 and contained mixed deciduous and coniferous tree species. We conducted a field study to determine if differences in stream NO3- concentration were controlled by the variability in soil freezing or tree litter quality. Reciprocal soil transplants were made between the Shibecha and Uryu sites using soils from at 0, 5, and 30 cm depths. Soil freezing occurred through out the study period (November-April 2004-05) at 0 and 5 cm depths at Shibecha while little freezing occurred at Uryu. Uryu litter had a higher C: N ratio (25.0 versus 22.4 for Shibecha) , higher lignin: N ratios (15 versus 8.8 ), and higher lignin concentrations (0.28 versus 0.18 g lignin g-1). These differences in litter quality contributed to higher net mineralization and nitrification in Shibecha compared to Uryu that resulted in higher NO3- concentrations in the drainage waters of Shibecha versus Uryu. Sites experiencing severe soil freezing had relatively high net mineralization rates but lower or unchanged net nitrification compared to sites that had little soil freezing. Effects of soil freezing were most pronounced in the Uryu soil buried in Shibecha. Variability in NO3- concentration in Shibecha versus Uryu streams were attributed to difference in tree species composition as well as the magnitude of soil freezing.

  19. Freeze–thaw cycles as drivers of complex ribozyme assembly

    NASA Astrophysics Data System (ADS)

    Mutschler, Hannes; Wochner, Aniela; Holliger, Philipp

    2015-06-01

    The emergence of an RNA catalyst capable of self-replication is considered a key transition in the origin of life. However, how such replicase ribozymes emerged from the pools of short RNA oligomers arising from prebiotic chemistry and non-enzymatic replication is unclear. Here we show that RNA polymerase ribozymes can assemble from simple catalytic networks of RNA oligomers no longer than 30 nucleotides. The entropically disfavoured assembly reaction is driven by iterative freeze–thaw cycles, even in the absence of external activation chemistry. The steep temperature and concentration gradients of such cycles result in an RNA chaperone effect that enhances the otherwise only partially realized catalytic potential of the RNA oligomer pool by an order of magnitude. Our work outlines how cyclic physicochemical processes could have driven an expansion of RNA compositional and phenotypic complexity from simple oligomer pools.

  20. Vertical dynamics Spiral structure

    E-print Network

    Kruit, Piet van der

    Outline Vertical dynamics Spiral structure The Hubble type of the Galaxy STRUCTURE OF GALAXIES 7;Outline Vertical dynamics Spiral structure The Hubble type of the Galaxy Outline Vertical dynamics van der Kruit, Kapteyn Astronomical Institute Structure of galaxy disks #12;Outline Vertical dynamics

  1. Simulation of Slag Freeze Layer Formation: Part I. Experimental Study

    NASA Astrophysics Data System (ADS)

    Guevara, Fernando J.; Irons, Gordon A.

    2011-08-01

    This study was conducted to understand the freeze layer formation and heat transfer that is required to design cooling systems in pyrometallurgical operations in which a frozen slag layer is used to protect the furnace wall. Similar Grashof and Prandtl numbers for operating furnaces were obtained in a 200-mm square cavity differentially heated on the sides containing an aqueous solution of calcium chloride. The solid front was tracked using a digital camera, and the temperature field was measured with thermocouples. The flow velocity field was measured using the two-dimensional particle image velocimetry technique. Experiments were conducted over a range of superheat conditions, and the solidification front was planar ( i.e., neither cellular nor dendritic) because the system slowly approached steady state. The two-phase zone comprised particles circulating slowly with the liquid in the bulk of the cavity; at the vertical walls, velocities were higher.

  2. Surface freezing of n-octane nanodroplets

    NASA Astrophysics Data System (ADS)

    Modak, Viraj; Pathak, Harshad; Thayer, Mitchell; Singer, Sherwin; Wyslouzil, Barbara

    2013-05-01

    Surface freezing, at temperatures up to a few degrees above the equilibrium melting point, has been observed for intermediate chain length (16? i? 50) n-alkanes [B. M. Ocko, X. Z. Wu, E. B. Sirota, S. K. Sinha, O. Gang and M. Deutsch, Phys. Rev. E, 1997, 55, 3164-3182]. Our recent experimental results suggest that surface freezing is also the first step when highly supercooled nanodroplets of n-octane crystallize. Our data yield surface and bulk nucleation rates on the order of ˜1015/cm2.s and ˜1022/cm3.s, respectively. Complementary molecular dynamics simulations also show that the surface of the droplet freezes almost immediately, and freezing of the remainder of the droplet progresses in a layer-by-layer manner.

  3. Freeze-out Conditions from Lattice QCD

    E-print Network

    Swagato Mukherjee

    2012-11-29

    We describe a procedure for determination of freeze-out parameters of heavy-ion collisions through direct comparisons between experimentally measured higher order cumulants of charge fluctuations and first principle (lattice) QCD calculations.

  4. Freezing and Thawing Human Embryonic Stem Cells

    NSDL National Science Digital Library

    Kent, Lia

    Lia Kent, of Stemgent's Research and Development team, has created this video to demonstrate "the proper technique for rapidly thawing hES cells from liquid nitrogen stocks, plating them on mouse embryonic feeder cells, and slowly freezing them for long-term storage." The video is also accompanied by protocols for thawing and freezing hES cells, discussion, materials, references, a forum for comments, and a PDF of the full text.

  5. Geysering inhibitor for vertical cryogenic transfer piping

    NASA Technical Reports Server (NTRS)

    Howard, F. S.

    1973-01-01

    Geysering (i.e., the expulsion of boiling liquid and its vapor from a vertical tube) has been a problem for the missile industry in long vertical cryogenic propellant feed lines connecting the launch vehicle propellant tank with the rocket engines. A proposed novel method of inhibiting geysering and the associated pressure gradients provides a self-starting self-regulating action that is not dependent on other active systems or components. The inhibiting action is attained by incorporating a concentric tube within the main transfer tube to prevent constriction of natural convective flow.

  6. The effect of density gradients on hydrometers

    NASA Astrophysics Data System (ADS)

    Heinonen, Martti; Sillanpää, Sampo

    2003-05-01

    Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system. In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients.

  7. A new portable device for automatic controlled-gradient cryopreservation of blood mononuclear cells.

    PubMed

    Hviid, L; Albeck, G; Hansen, B; Theander, T G; Talbot, A

    1993-01-01

    Protection of the functional integrity of mononuclear cells stored in liquid N2 requires careful control of the freezing procedure. Consequently, optimal quality of cryopreserved cells is usually assured by freezing according to a specified time-temperature gradient generated by computer-controlled freezing devices. While such equipment offers large capacity and secures maximum survival and functional integrity of the lymphocytes upon thawing, it is quite costly and strictly stationary. We have previously developed and tested an alternative, manual device for controlled-gradient lymphocyte freezing, which has proved suitable for field conditions. We report here the development and testing of a similar micro-controller regulated device, allowing unattended and automatic controlled-gradient cell freezing. The equipment exploits the temperature gradient present between the liquid N2 surface and the neck in an ordinary liquid N2 refrigerator. The lymphocyte samples are placed in a small elevator, which is moved through the N2 gas phase by a stepper motor. Time and temperature are measured at regular intervals, and the position of the samples adjusted to ensure that the actual measurements closely match encoded ideal values. Results of assays of the functional integrity and phenotypic composition of human mononuclear cells frozen by the new system were comparable to those obtained when using cells frozen by a commercially available, stationary cell-freezing equipment, or fresh autologous cell samples tested in parallel. Furthermore, there was a good correlation between functional and phenotypic data obtained using frozen and autologous fresh samples of mononuclear cells. The equipment described is low weight and has low N2 consumption, and is thus suitable for the collection and cryopreservation of lymphocytes under field conditions. Furthermore, the technique provides an inexpensive alternative for researchers with a limited requirement for the simultaneous freezing of large quantities of cells. PMID:8423356

  8. Ultrastructural metabolic activity following quick-freezing and freeze-substitution in tetrahydrofuran in the superior cervical ganglion

    Microsoft Academic Search

    Paul J. Yarowsky; Alan F. Boyne

    1989-01-01

    Summary A method of quick-freezing and freeze-substitution has been developed for localizing diffusible substances such as 2-deoxyglucose-6-phosphate (2-DG-6-P) ultrastructurally in neural tissue. Quick-freezing under pressure provides well preserved tissue down to 30–35 µm from the surface. This allows blocks of neural tissue to be quick-frozen and analysed for diffusible substances in areas removed from the freezing face. Freeze-substitution in tetrahydrofuran

  9. The equilibrated state of freezing as a basis for distinguishing lethal stresses of freezing in plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A model for coordination of stresses that limit winterhardiness in plants based on the thermodynamic equilibrated state of freezing and melting provides a rational basis for distinction of freeze-induced energies which can stress and injure living organisms in various ways. The departure from equili...

  10. An Improved Microscope Stage for Direct Observation of Freezing and Freeze Drying

    Microsoft Academic Search

    Steven L. Nail; Lih-Min Her; Christopher P. B. Proffitt; Lisa L. Nail

    1994-01-01

    A microscope stage for observation of freezing and freeze drying is described. The stage uses thermoelectric (Peltier) heaters configured in two stages, with circulating fluid as a heat sink on the high temperature side. Lowest attainable sample temperature is about -47°C. Principal advantages of this system are closed-loop control of stage temperature, rapid response to changes in temperature set point,

  11. Influence of chemical and freezing fixation methods in the freeze-fracture of stratum corneum.

    PubMed

    López, O; López-Iglesias, C; Cócera, M; Walther, P; Parra, J L; De La Maza, A

    2004-06-01

    A comparison between two fixation techniques for freeze-fracture was established. Stratum corneum (SC) samples from pig epidermis were fixed using high-pressure freezing (HPF) and using plunging in propane freezing; the latter after chemical fixation. Then, frozen samples were freeze-fractured, coated with platinum-carbon, and visualized using a high-resolution low-temperature scanning electron microscope and a transmission electron microscope. Our results indicate that the plane of freeze-fracture was different depending on the fixation and freezing methodology used. In the samples frozen by HPF without chemical fixation, the fracture plane laid mainly between the lipid lamellae. However, when chemical fixation and plunging in propane freezing was used, the fracture plane did not show preference to a specific way. Plunging in propane freezing of chemically fixed samples, on the other hand, provides a more homogeneous fracture behaviour. Thus, depending on the methodology used, we can favour a visualization of either lipid or protein domains of the SC. These results could be very useful in future ultrastructural studies in order to facilitate the microscopic visualization and interpretation of the complex images such as those of SC and even of other samples in which different domains coexist. PMID:15099572

  12. Freezing rate and duration determine the physiological response of intertidal fucoids to freezing

    Microsoft Academic Search

    G. A. Pearson; I. R. Davison

    1993-01-01

    Differential thermal analysis (DTA) was used to measure the freezing temperature of nine species of red brown intertidal macroalgae from the coast of Maine, USA in 1991. Using slow and rapid cooling rates approximating those found in the field for Ascophyllum nodosum (L.) Le Jol. we found that, for a given rate, the freezing points of all species were similar:

  13. Temperature Dependence of Vertical Transport in Quantum Hall Multilayers

    NASA Astrophysics Data System (ADS)

    Walling, H. A.; Dougherty, D. P.; Druist, D. P.; Gwinn, E. G.; Maranowski, K. D.; Gossard, A. C.

    2001-03-01

    We study the temperature dependence of vertical transport in AlGaAs/GaAs multilayers in the regime of the quantum Hall effect. At low temperatures vertical transport in quantum Hall states occurs on a 2D chiral sheath of edge states near the sidewalls of the sample mesas. At higher temperatures variable range hopping through the bulk of the sample dominates. To extend the temperature range of sheath-dominated transport, we increase the device perimeters using fractal-shaped mesas defined by e-beam lithography. We report on the freeze-out of bulk transport and the weak temperature dependence of the sheath conductivity.

  14. DENSITY GRADIENT TECHNIQUES

    Microsoft Academic Search

    Gerald Oster; Masahide Yamamoto

    1963-01-01

    The most sensitive and simplest method for determining minute changes in ; density is the density gradient column technique, which is capable of detecting ; density differences as small as 10⁻⁷ g\\/cc. A review is presented of the ; theory and formation of the gradient, the movement of the test object in the ; gradient, and the applications of the

  15. Gradient coils and reciprocity

    Microsoft Academic Search

    J. C. Mallinson

    1991-01-01

    It is observed that the problem of optimizing the design of gradient coils is identical to the problem of optimizing the design of vibrating sample magnetometer (VSM) pick-up coils. The problem of optimizing the design of the gradient coils is that of maximizing the appropriate field gradient at the position of the magnetic sample depending on the design of the

  16. Vertical Map Storage.

    ERIC Educational Resources Information Center

    Perry, Joanne M.

    1982-01-01

    Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

  17. Freeze-drying of lactic acid bacteria.

    PubMed

    Fonseca, Fernanda; Cenard, Stéphanie; Passot, Stéphanie

    2015-01-01

    Lactic acid bacteria are of great importance for the food and biotechnology industry. They are widely used as starters for manufacturing food (e.g., yogurt, cheese, fermented meats, and vegetables) and probiotic products, as well as for green chemistry applications. Freeze-drying or lyophilization is a convenient method for preservation of bacteria. By reducing water activity to values below 0.2, it allows long-term storage and low-cost distribution at suprazero temperatures, while minimizing losses in viability and functionality. Stabilization of bacteria via freeze-drying starts with the addition of a protectant solution to the bacterial suspension. Freeze-drying includes three steps, namely, (1) freezing of the concentrated and protected cell suspension, (2) primary drying to remove ice by sublimation, and (3) secondary drying to remove unfrozen water by desorption. In this chapter we describe a method for freeze-drying of lactic acid bacteria at a pilot scale, thus allowing control of the process parameters for maximal survival and functionality recovery. PMID:25428024

  18. Freeze verification: time for a fresh approach

    SciTech Connect

    Paine, C.

    1983-01-01

    The administration's claim that some elements of a comprehensive nuclear freeze are unverifiable does not specify the nature of those elements and whether they represent a real threat to national security if we trusted the USSR to comply. The author contends that clandestine development of new weapons will have little strategic effect since both sides already have total destructive power. The risks of noncompliance are largely political and less than the risks of continued arms buildup. Since the USSR would also want the US to be bound by freeze terms, deterrence would come from mutual benefit. Hardliners argue that cheating is easier in a closed society; that our democracy would tend to relax and the USSR would move ahead with its plans for world domination. The author argues that, over time, a freeze would diminish Soviet confidence in its nuclear war fighting capabilities and that adequate verification is possible with monitoring and warning arrangements. (DCK)

  19. Study on Freezing of a Single Droplet

    NASA Astrophysics Data System (ADS)

    Fumoto, Koji; Yamagishi, Hideaki; Ikegawa, Masahiro

    The freezing characteristics of a single water droplet placed on the column edge were visually investigated using a video camera. The temperatures of the edge face and the environment air were independently controlled. The solidification process of the water droplet was discussed based on the many pictures obtained. The experimental results indicated that the freezing time of droplet was strongly affected by the edge temperature. Furthermore, we found that the water dispersion thermosensitivity slurry was effective for the observation of the temperature of the droplet. Consequently, it was indicated that the heat transfer characteristics of the droplet under freezing condition were mainly affected by both temperature of the air and surface of the flat plate.

  20. Directional freezing for large volume cryopreservation.

    PubMed

    Saragusty, Joseph

    2015-01-01

    Cryopreservation is currently the method of choice when it comes to long-term preservation of viable biological samples. The process, and consequently the volume of the sample, however, is limited by the ability to achieve homogenous and efficient heat removal. When this cannot be properly managed, ice crystals will grow uncontrollably resulting in extensive damage to the cryopreserved cells or tissues. Directional freezing is a technique that can be used to precisely control heat dissipation and ice crystal growth and morphology even when freezing large volumes. The technique has been used over the years to cryopreserve spermatozoa, oocytes, embryos, tissue slices and whole organs from a wide variety of domestic and wild species. In this chapter a protocol for directional freezing of spermatozoa is described and its benefits and shortcomings are discussed. PMID:25428019

  1. Freezing precipitation in the Southeastern United States

    E-print Network

    Young, William Robert

    1978-01-01

    they assumed that the surface was at 1000 mb. U )~ CQ ~+10 CO LL| +5 CL & o LLt E O -~o CO FREEZI NG RAIN 0? RAI N MIXED PREC IP TYPES No CASES -10 -5 0 +5 SURFACE TEMP(V&ET euLEI) C Fig. 4. Decision graph developed by Hilworth... of surface temperature and thickness but with an 850-mb temperature less than or equal to O'C, A decision graph based on the rules devised by Tang is d-picted in Fig 5 ~ 21 +10 FREEZING RAiN FOR SNOVC, SLEET OR FREEZING RA I N:1QQQ- ~Q 0-mb THICK...

  2. Airborne measurements of cloud condensation nuclei using a new continuous-flow streamwise thermal-gradient CCN chamber

    Microsoft Academic Search

    G. C. Roberts; A. Nenes; T. Vanreken; T. Rissman; W. C. Conant; V. Varutbangkul; H. H. Jonsson; R. C. Flagan; J. H. Seinfeld; V. Ramanathan

    2003-01-01

    A light-weight continuous-flow thermal gradient diffusion chamber was developed for autonomous operation in airborne studies employing a novel technique of generating a supersaturation along the streamwise axis of the instrument. A vertical cylindrical column, whose surfaces are wetted and exposed to an increasing temperature gradient along the vertical axis, constitutes the chamber volume. This design exploits the differences in diffusion

  3. Physiological responses to freezing in hatchlings of freeze-tolerant and -intolerant turtles.

    PubMed

    Costanzo, Jon P; Baker, Patrick J; Lee, Richard E

    2006-09-01

    Freeze tolerance is a complex cold-hardiness adaptation that has independently evolved in a diverse group of organisms, including several ectothermic vertebrates. Because little is known about the mechanistic basis for freeze tolerance in reptiles, we compared responses to experimental freezing in winter-acclimatized hatchlings representing nine taxa of temperate North American turtles, including ones that tolerated freezing and others that did not. Viability rates of hatchlings frozen to -3 degrees C for 72 h ranged from 0 to 100%. Tolerance to freezing was poor in Sternotherus odoratus, Graptemys geographica and Trachemys scripta, intermediate in Chelydra serpentina, and high in Emydoidea blandingii, Chrysemys picta bellii, C. p. marginata, Malaclemys terrapin, and Terrapene ornata, and generally reflected the winter thermal ecology of each taxon. Plasma activity of lactate dehydrogenase (LDH), a novel in vivo index of freeze/thaw damage, corroborated viability assessments and demonstrated that cryoinjury occurred even in surviving turtles. Irrespective of taxon, cryoinjury tended to be higher in smaller individuals and in those having relatively low water contents; however, bases for these associations were not apparent. Screening for certain organic osmolytes that might promote freezing survival by colligatively reducing ice content and limiting cell dehydration showed that the plasma of unfrozen (control) turtles contained small quantities of glucose (1.3-5.8 mmol l(-1)) and lactate (0.6-3.2 mmol l(-1)) and modest amounts of urea (range of mean values for all taxa 8.2-52.3 mmol l(-1)). Frozen/thawed turtles of all taxa accumulated modest amounts of glucose and lactate that jointly raised the plasma solute concentration by 30-100 mmol l(-1). We conclude that organic osmolytes accumulated both before and during freezing may promote survival in species that have evolved a tolerance to freezing, but are not necessarily accumulated for that purpose. PMID:16758216

  4. Stereo transparency and the disparity gradient limit

    NASA Technical Reports Server (NTRS)

    McKee, Suzanne P.; Verghese, Preeti

    2002-01-01

    Several studies (Vision Research 15 (1975) 583; Perception 9 (1980) 671) have shown that binocular fusion is limited by the disparity gradient (disparity/distance) separating image points, rather than by their absolute disparity values. Points separated by a gradient >1 appear diplopic. These results are sometimes interpreted as a constraint on human stereo matching, rather than a constraint on fusion. Here we have used psychophysical measurements on stereo transparency to show that human stereo matching is not constrained by a gradient of 1. We created transparent surfaces composed of many pairs of dots, in which each member of a pair was assigned a disparity equal and opposite to the disparity of the other member. For example, each pair could be composed of one dot with a crossed disparity of 6' and the other with uncrossed disparity of 6', vertically separated by a parametrically varied distance. When the vertical separation between the paired dots was small, the disparity gradient for each pair was very steep. Nevertheless, these opponent-disparity dot pairs produced a striking appearance of two transparent surfaces for disparity gradients ranging between 0.5 and 3. The apparent depth separating the two transparent planes was correctly matched to an equivalent disparity defined by two opaque surfaces. A test target presented between the two transparent planes was easily detected, indicating robust segregation of the disparities associated with the paired dots into two transparent surfaces with few mismatches in the target plane. Our simulations using the Tsai-Victor model show that the response profiles produced by scaled disparity-energy mechanisms can account for many of our results on the transparency generated by steep gradients.

  5. Node of Ranvier formation along fibres regenerating through silicone tube implants: A freeze-fracture and thin-section electron microscopic study

    Microsoft Academic Search

    J. M. Le Beau; H. C. Powell; M. H. Ellisman

    1987-01-01

    Summary Thin-section and freeze-fracture electron microscopy have been used to examine the morphogenesis of the node of Ranvier in peripheral nerves regenerating through silicone tubes. A major question posed by this study is whether node formation in fibres regenerating across a gap recapitulates that occurring in normal development. Node formation occurs concurrently with myelination and follows a similar spatial gradient

  6. Energy Budgets and Temperatures of Nyctinastic Leaves on Freezing Nights 1

    PubMed Central

    Schwintzer, Christa R.

    1971-01-01

    Temperatures of exposed horizontal and vertical soybean leaves (Glycine max [L.] Merr. var. Chippewa) were measured on calm, clear nights with temperatures near freezing. Average leaf-air temperature differences for 5 nights were ?1.5 C and ?1.0 C for horizontal and vertical leaves respectively. The horizontal leaves were cooler than the vertical leaves. The mean of all observed horizontal-vertical leaf temperature differences was ?0.5 C with a maximum average for 1 night of ?0.8 C, while maximum differences theoretically attainable in similar leaves were calculated to be ?1.7 C. No differences were observed in the extent of frost damage in horizontal and vertical leaves. The apparent reduction in frost damage in vertical leaves observed by Charles Darwin was probably caused by his method of using corks to hold the horizontal leaves and not by leaf orientation. Theoretical considerations and the experimental results indicate that nyctinastic leaf movements probably do not provide significant protection from frost for any plants. PMID:16657763

  7. Protein Inhalation Powders: Spray Drying vs Spray Freeze Drying

    Microsoft Academic Search

    Yuh-Fun Maa; Phuong-Anh Nguyen; Theresa Sweeney; Steven J. Shire; Chung C. Hsu

    1999-01-01

    Purpose. To develop a new technique, spray freeze drying, for preparing protein aerosol powders. Also, to compare the spray freeze-dried powders with spray-dried powders in terms of physical properties and aerosol performance.

  8. Preservation of flavor in freeze dried green beans

    NASA Technical Reports Server (NTRS)

    Huber, C. S.; Heidelbaugh, N. D.; Davis, D.

    1973-01-01

    Before freeze drying, green beans are heated to point at which their cell structure is altered. Beans freeze dried with altered cell structure have improved rehydration properties and retain color, flavor, and texture.

  9. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts...satisfactory air circulation and maintained in a clean and sanitary condition. The rooms shall be constructed in the same manner...

  10. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts...satisfactory air circulation and maintained in a clean and sanitary condition. The rooms shall be constructed in the same manner...

  11. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts...satisfactory air circulation and maintained in a clean and sanitary condition. The rooms shall be constructed in the same manner...

  12. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts...satisfactory air circulation and maintained in a clean and sanitary condition. The rooms shall be constructed in the same manner...

  13. OUHSC -Hiring Freeze Guidelines & Procedures (Updated February 2013)

    E-print Network

    Oklahoma, University of

    OUHSC - Hiring Freeze Guidelines & Procedures (Updated February 2013) Revised and effective-Tulsa operations and other operating locations, has revised its operating guidelines and procedures. Freeze transactions remain subject to standard OU policies, operating procedures and guidelines. All staff positions

  14. 40 CFR 52.1135 - Regulation for parking freeze.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 false Regulation for parking freeze. 52.1135 Section 52.1135...Massachusetts § 52.1135 Regulation for parking freeze. (a) Definitions: (1...land filling specifically designed for a parking facility in preparation for...

  15. Unitarity Constraints on Asymmetric Freeze-In

    SciTech Connect

    Hook, Anson; /SLAC

    2011-08-15

    This paper considers unitarity and CPT constraints on asymmetric freeze-in, the use of freeze-in to store baryon number in a dark sector. In this scenario, Sakharov's out of equilibrium condition is satisfied by placing the visible and hidden sectors at different temperatures while a net visible baryon number is produced by storing negative baryon number in a dark sector. It is shown that unitarity and CPT lead to unexpected cancellations. In particular, the transfer of baryon number cancels completely at leading order. This note has shown that if two sectors are in thermal equilibrium with themselves, but not with each other, then the leading effect transferring conserved quantities between the two sectors is of order the the weak coupling connecting them to the third power. When freeze-in is used to produce a net baryon number density, the leading order effect comes from {Omicron}({lambda}{sup 3}) diagrams where the intermediate state that goes on-shell has a different visible baryon number than the final state visible baryon number. Models in which the correct baryon number is generated with freeze-in as the dominant source of abundance, typically require {lambda} {approx}> 10{sup -6} and m{sub bath} {approx}> TeV. m{sub bath} is the mass of the visible particle which communicates with the hidden sector. The lower window is potentially observable at the LHC.

  16. Device and method for determining freezing points

    NASA Technical Reports Server (NTRS)

    Mathiprakasam, Balakrishnan (Inventor)

    1986-01-01

    A freezing point method and device (10) are disclosed. The method and device pertain to an inflection point technique for determining the freezing points of mixtures. In both the method and device (10), the mixture is cooled to a point below its anticipated freezing point and then warmed at a substantially linear rate. During the warming process, the rate of increase of temperature of the mixture is monitored by, for example, thermocouple (28) with the thermocouple output signal being amplified and differentiated by a differentiator (42). The rate of increase of temperature data are analyzed and a peak rate of increase of temperature is identified. In the preferred device (10) a computer (22) is utilized to analyze the rate of increase of temperature data following the warming process. Once the maximum rate of increase of temperature is identified, the corresponding temperature of the mixture is located and earmarked as being substantially equal to the freezing point of the mixture. In a preferred device (10), the computer (22), in addition to collecting the temperature and rate of change of temperature data, controls a programmable power supply (14) to provide a predetermined amount of cooling and warming current to thermoelectric modules (56).

  17. A Fast Hadron Freeze-out Generator

    E-print Network

    N. S. Amelin; R. Lednicky; T. A. Pocheptsov; I. P. Lokhtin; L. V. Malinina; A. M. Snigirev; Iu. A. Karpenko; Yu. M. Sinyukov

    2006-10-13

    We have developed a fast Monte Carlo procedure of hadron generation allowing one to study and analyze various observables for stable hadrons and hadron resonances produced in ultra-relativistic heavy ion collisions. Particle multiplicities are determined based on the concept of chemical freeze-out. Particles can be generated on the chemical or thermal freeze-out hypersurface represented by a parameterization or a numerical solution of relativistic hydrodynamics with given initial conditions and equation of state. Besides standard space-like sectors associated with the volume decay, the hypersurface may also include non-space-like sectors related to the emission from the surface of expanding system. For comparison with other models and experimental data we demonstrate the results based on the standard parameterizations of the hadron freeze-out hypersurface and flow velocity profile under the assumption of a common chemical and thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at http://uhkm.jinr.ru/.

  18. Preservation of corynebacteriophages by freeze-drying

    PubMed Central

    Carne, H. R.; Greaves, R. I. N.

    1974-01-01

    A method of freeze-drying is described by which the activity of a series of eorynebacteriophages was maintained over a test period of 30 months, whereas some of these strains became inactive if stored as liquid filtered lysates at 4° C., or frozen and held at -25° C. PMID:4602040

  19. Freezing of Triangulations J.-P. Kownacki

    E-print Network

    Paris-Sud XI, Université de

    E-mail : kownacki@ptm.u-cergy.fr Abstract Zero temperature dynamics of two dimensional into clusters of same topological charge. It is conjectured that freezing is related to high temperature structure of baby universes. Published in Eur. Phys. J B 38, 485-494 (2004) 1 #12;1 Introduction Two

  20. Freeze verification: time for a fresh approach

    Microsoft Academic Search

    Paine

    1983-01-01

    The administration's claim that some elements of a comprehensive nuclear freeze are unverifiable does not specify the nature of those elements and whether they represent a real threat to national security if we trusted the USSR to comply. The author contends that clandestine development of new weapons will have little strategic effect since both sides already have total destructive power.

  1. FREEZE-FRAME: Fast Action Stress Relief.

    ERIC Educational Resources Information Center

    Childre, Doc Lew

    Recent scientific research has proven that we can, not only manage our stress, we can even prevent it. Ways to achieve stress management are presented in this book. It details a method called FREEZE-FRAME, a process in which individuals mentally stop the chaos that surrounds them and then calmly contemplate their situation. The text opens with an…

  2. Effect of process conditions on recovery of protein activity after freezing and freeze-drying

    Microsoft Academic Search

    Shan Jiang; Steven L Nail

    1998-01-01

    The objective of this research was to gain a better understanding of the degree to which recovery of activity of model proteins after freeze-drying can be maximized by manipulation of freeze-dry process conditions in the absence of protective solutes. Catalase, ?-galactosidase and lactate dehydrogenase (LDH) were used as model proteins. All of the three proteins exhibited a concentration-dependent loss of

  3. Original article Spray-freeze-drying of whey proteins

    E-print Network

    Paris-Sud XI, Université de

    Original article Spray-freeze-drying of whey proteins at sub-atmospheric pressures Chinnaswamy February 2010 Published online 30 March 2010 Abstract ­ Spray-freeze-drying (SFD) involves spraying a solution into a cold medium, and freeze- drying the resultant frozen particles, which can be performed

  4. Modification of physical properties of freeze-dried rice

    NASA Technical Reports Server (NTRS)

    Huber, C. S.

    1971-01-01

    Freeze cycling process consists of alternately freezing and thawing precooked rice for two cycles, rice is then frozen and freeze-dehydrated in vacuum sufficient to remove water from rice by sublimitation. Process modifies rice grain structure and porosity, enabling complete rehydration in one minute in hot water.

  5. Genetics of winter wheat response to two freezing treatments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The inheritance of the ability of winter wheat plants to survive two kinds of freezing stress was investigated in a five-parent diallel cross. Plants were acclimated at +4°C for 5 wks and frozen with or without a –3°C, 16-hour pre-freezing (PF) period prior to freezing to damaging temperatures. The ...

  6. Damage by Early Autumn Freeze Varies with Pecan Cultivar

    Microsoft Academic Search

    Michael W. Smith

    Pecan (Carya illinoinensis (Wangenh.) C. Koch.) trees were injured by freezing temperatures in Oct. 2000, occurring about 4 weeks before the average first freeze and 6 weeks before the normal killing freeze (less than or equal to -2 °C). Nonbearing and bearing cultivars were rated for injury at four sites the following May. Nonbearing cultivars with little or no damage

  7. Interdecadal changes in seasonal freeze and thaw depths in Russia

    Microsoft Academic Search

    Oliver W. Frauenfeld; Tingjun Zhang; Roger G. Barry; David Gilichinsky

    2004-01-01

    Seasonal freezing and thawing processes in cold regions play a major role in ecosystem diversity, productivity, and the Arctic hydrological system. Long-term changes in seasonal freeze and thaw depths are also important indicators of climate change. Only sparse historical measurements of seasonal freeze and thaw depths are available for permafrost and seasonally frozen ground regions. Using mean monthly soil temperature

  8. Foliar applied urea improves freezing protection to avocado and peach

    Microsoft Academic Search

    S. Zilkah; Z. Wiesmann; I. Klein; I. David

    1996-01-01

    The effect of foliar applied urea on freeze hardiness was evaluated under orchard and laboratory conditions. Freezing injury and senescence of avocado (Persea americana Mill.) cv. ‘Hass’ leaves in the orchard was inversely correlated to N content. Three foliar applications of 2% low-biuret urea caused a 26% nitrogen enrichment of leaves. Consequently, leaf freezing hardiness was increased and senescence retarded.

  9. The parenchymal reaction of the kidney after local freezing

    Microsoft Academic Search

    H. Breining; B. Helpap; A. Minderjahn; S. Lymberopoulos

    1974-01-01

    Histological and autoradiographic studies were performed to investigate the reparative processes during wound healing in kidneys after local freezing. 12h after freezing (-186°C, 30 sec) the cryonecrosis is fully developed. After the 5th postoperative day the cryonecrotic area shows a pronounced calcification of necrotic tubules. 30 days after freezing the reparation of the cryolesion in the kidney results in a

  10. VISUALIZATION OF FREEZING PROGRESSION IN TURFGRASSES USING INFRARED VIDEO THERMOGRAPHY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Freezing injury can be a significant problem in turfgrasses. Understanding how freezing develops and ramifies throughout the plant could assist in the development of improved management or screening processes for cultivar improvemen. The development of freezing injury is not well understand due pa...

  11. Objective video quality assessment method for freeze distortion based on freeze aggregation

    NASA Astrophysics Data System (ADS)

    Watanabe, Keishiro; Okamoto, Jun; Kurita, Takaaki

    2006-01-01

    With the development of the broadband network, video communications such as videophone, video distribution, and IPTV services are beginning to become common. In order to provide these services appropriately, we must manage them based on subjective video quality, in addition to designing a network system based on it. Currently, subjective quality assessment is the main method used to quantify video quality. However, it is time-consuming and expensive. Therefore, we need an objective quality assessment technology that can estimate video quality from video characteristics effectively. Video degradation can be categorized into two types: spatial and temporal. Objective quality assessment methods for spatial degradation have been studied extensively, but methods for temporal degradation have hardly been examined even though it occurs frequently due to network degradation and has a large impact on subjective quality. In this paper, we propose an objective quality assessment method for temporal degradation. Our approach is to aggregate multiple freeze distortions into an equivalent freeze distortion and then derive the objective video quality from the equivalent freeze distortion. Specifically, our method considers the total length of all freeze distortions in a video sequence as the length of the equivalent single freeze distortion. In addition, we propose a method using the perceptual characteristics of short freeze distortions. We verified that our method can estimate the objective video quality well within the deviation of subjective video quality.

  12. Ultrastructure of the frog retina after high-pressure freezing and freeze substitution.

    PubMed

    Wilson, M T; Farmer, M A; Karwoski, C J

    1998-03-01

    In many types of tissue, high-pressure freezing (HPF), followed by freeze substitution, can produce excellent ultrastructural preservation at depths over 10 times that obtained by other cryofixation techniques. However, in the case of neural tissue, the benefits of HPF have not been realized. In the present study, isolated frog (Rana pipiens) retina was sliced at a thickness of 150 or 350 microns, rapidly frozen in a Balzers HPM 010 high-pressure freezer, and freeze substituted with 1% OsO4 and 0.1% tannic acid in acetone. Specially designed HPF chambers and specific freezing media (35% high-MW dextran for 150-micron slices or 15% low-MW dextran for 350-micron slices) were required for adequate freezing. The quality of preservation after HPF was excellent throughout the retina in both the 150- and 350-micron slices, compared with chemically fixed slices. Specifically, HPF resulted in better preserved cellular, mitochondrial and nuclear membranes in all retinal layers. This is the first study to successfully cryofix all of the layers of the retina. The increased depths of adequate freezing achieved by HPF should facilitate various ultrastructural studies of retina, as well as of other CNS tissues, where preservation approaching that of the 'native' state is required. PMID:9588021

  13. Control of pore channel size during freeze casting of porous YSZ ceramics with unidirectionally aligned channels using different freezing temperatures

    Microsoft Academic Search

    Liangfa Hu; Chang-An Wang; Yong Huang; Chencheng Sun; Sheng Lu; Zijun Hu

    2010-01-01

    Porous yttria-stabilized zirconia (YSZ) ceramics with unidirectionally aligned pore channels were prepared by freezing YSZ\\/tert-butyl alcohol (TBA) slurry under different freezing temperatures of ?30, ?78 and ?196°C, respectively. After removing the frozen TBA via freeze-drying in vacuum at ?50°C, the green samples were sintered at 1450°C for 2h in air. The results showed that the freezing temperature significantly influenced microstructure

  14. Ambient in-situ immersion freezing measurements - findings from the ZAMBIS 2014 field campaign for three ice nucleation techniques

    NASA Astrophysics Data System (ADS)

    Kohn, Monika; Atkinson, James D.; Lohmann, Ulrike; Kanji, Zamin A.

    2015-04-01

    To estimate the influence of clouds on the Earth's radiation budget, it is crucial to understand cloud formation processes in the atmosphere. A key process, which significantly affects cloud microphysical properties and the initiation of precipitation thus contributing to the hydrological cycle, is the prevailing type of ice nucleation mechanism. In mixed-phase clouds immersion freezing is the dominant ice crystal forming mechanism, whereby ice nucleating particles (INP) first act as cloud condensation nuclei (CCN) and are activated to cloud droplets followed by freezing upon supercooling. There are a number of experimental methods and techniques to investigate the ice nucleating ability in the immersion mode, however most techniques are offline for field sampling or only suitable for laboratory measurements. In-situ atmospheric studies are needed to understand the ice formation processes of 'real world' particles. Laboratory experiments simulate conditions of atmospheric processes like ageing or coating but are still idealized. Our method is able to measure ambient in-situ immersion freezing on single immersed aerosol particles. The instrumental setup consists of the recently developed portable immersion mode cooling chamber (PIMCA) as a vertical extension to the portable ice nucleation chamber (PINC, [1]), where the frozen fraction of activated aerosol particles are detected by the ice optical depolarization detector (IODE, [2]). Two additional immersion freezing techniques based on a droplet freezing array [3,4] are used to sample ambient aerosol particles either in a suspension (fraction larger ~0.6 ?m) or on PM10-filters to compare different ice nucleation techniques. Here, we present ambient in-situ measurements at an urban forest site in Zurich, Switzerland held during the Zurich ambient immersion freezing study (ZAMBIS) in spring 2014. We investigated the ice nucleating ability of natural atmospheric aerosol with the PIMCA/PINC immersion freezing setup as well as a droplet freezing method on aerosol particles either collected in a suspension or on PM10-filters to obtain atmospheric IN concentrations based on the measured ambient aerosol. Investigation of physical properties (number and size distribution) and chemical composition as well as the meteorological conditions provide supplementary information that help to understand the nature of particles and air masses that contribute to immersion freezing. Acknowledgements We thank Hannes Wydler and Hansjörg Frei from ETH Zurich for their technical support. Furthermore, the authors want thank Franz Conen from the University of Basel for sharing equipment and training in the drop freezing experiment. References [1] Chou et al. (2011), Atmos. Chem. Phys., 11, 4725-4738. [2] Nicolet et al. (2010), Atmos. Chem. Phys., 10, 313-325. [3] Conen et al. (2012), Atmos. Meas. Tech., 5, 321-327. [4] Stopelli et al. (2014), Atmos. Meas. Tech., 7, 129-134.

  15. Effects of Freeze\\/Thaw Index, Air Temperature, and Snow Cover on Seasonal Freeze and Thaw Depths in Russia

    Microsoft Academic Search

    O. W. Frauenfeld; T. Zhang; R. G. Barry; D. Gilichinsky; A. J. Etringer

    2003-01-01

    Seasonal freezing and thawing processes in cold regions play an exceedingly important role in ecosystem diversity, productivity, and the Arctic hydrological system in general. Long-term changes in seasonal freeze and thaw depths are also important indicators of climate change. Only sparse observational measurements of seasonal freeze and thaw depths are available in permafrost and seasonally frozen ground regions. However, soil

  16. Quantum computational gradient estimation

    E-print Network

    David Bulger

    2005-07-12

    Classically, determining the gradient of a black-box function f:R^p->R requires p+1 evaluations. Using the quantum Fourier transform, two evaluations suffice. This is based on the approximate local periodicity of exp(2*pi*i*f(x)). It is shown that sufficiently precise machine arithmetic results in gradient estimates of any required accuracy.

  17. Learning the Coordinate Gradients

    Microsoft Academic Search

    Yiming Ying; Qiang Wu; Colin Campbell

    In this paper we study the problem of learning the gradient function with application to variable selection and determining variable covariation. Firstly, we pro- pose a novel unifying framework for coordinate gradient learning from the perspective of multi-task learning. Various variable selection algorithms can be regarded as spe- cial instances of this framework. Secondly, we formulate the dual problems of

  18. Multilayer Gradient Coil Design

    Microsoft Academic Search

    R. Bowtell; P. Robyr

    1998-01-01

    In standard cylindrical gradient coils consisting of wires wound in a single layer, the rapid increase in coil resistance with efficiency is the limiting factor in achieving very large magnetic field gradients. This behavior results from the decrease in the maximum usable wire diameter as the number of turns is increased. By adopting a multilayer design in which the coil

  19. Gradient index metamaterials

    Microsoft Academic Search

    D. R. Smith; J. J. Mock; A. F. Starr; D. Schurig

    2005-01-01

    Metamaterials---artificially structured materials with tailored electromagnetic response---can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam

  20. Very high gradient quadrupoles

    Microsoft Academic Search

    J. Strait

    2001-01-01

    High gradient superconducting quadrupoles are an essential component of high energy hadron colliders, both in the arcs and in the insertions. The highest performance quadrupoles today are those for the Large Hadron Collider (LHC) at CERN. These 56 to 70 mm aperture magnets, developed in Europe, the United States, and Japan, reach gradients on the order of 250 T\\/m, which

  1. Calculation of particle trajectories in the presence of a gradient in turbulent-velocity variance

    Microsoft Academic Search

    J. D. Wilson; B. J. Legg; D. J. Thomson

    1983-01-01

    Recent papers by Wilson et al. (1981b) and Legg and Raupach (1982) give methods for the calculation of particle trajectories in turbulence with a gradient in vertical velocity variance S2w. However the two methods seem contradictory.

  2. Study of freezing-point depression of selected food extracts

    SciTech Connect

    Tanaka, Fumihiko [Kagoshima Univ. (Japan). Dept. of Agricultural Systems Engineering; Murata, Satoshi; Habara, Kazuhiro; Amaratunga, K.S.P. [Kyushu Univ., Fukuoka (Japan). Dept. of Agricultural Engineering

    1996-12-31

    The phenomenon of freezing-point depression that accompanies the solute concentration of selected food extracts was investigated to reveal the characteristics of solid-liquid phase equilibrium. The freezing curves of various food extracts did not exhibit ideal solution behavior in the higher concentration range. The experimental data were fitted to new freezing-point depression equations by the method of nonlinear least squares, and the results clearly indicated that the calculated freezing points at various concentrations were in good agreement with the experimental data. Furthermore, by using the determined parameters, the freezing ratio and the activation coefficient were derived.

  3. Vertical electromagnetic profiling (VEMP)

    Microsoft Academic Search

    Lytle

    1984-01-01

    Vertical seismic profiling (VSP) is based upon reception measurements performed in a borehole with a source near the ground surface. This technology has seen a surge in application and development in the last decade. The analogous concept of vertical electromagnetic profiling (VEMP) consists of reception measurements performed in a borehole with a source near the ground surface. Although the electromagnetic

  4. Exotic Freezing of Response in Quantum Many-Body System

    E-print Network

    Arnab Das

    2010-11-01

    We show that when a quantum many-body system is subjected to coherent periodic driving, the response may exhibit exotic freezing behavior in high driving frequency ($\\omega$) regime. In a periodically driven classical thermodynamic system, freezing at high $\\omega$ occurs when $1/\\omega$ is much smaller than the characteristic relaxation time of the system, and hence the freezing always increases there as $\\omega$ is increased. Here, in the contrary, we see surprising non-monotonic freezing behavior of the response with $\\omega$, showing curious peak-valley structure. Quite interestingly, the entire system tends to freeze almost absolutely (the freezing peaks) when driven with a certain combination of driving parameters values (amplitude and $\\omega$) due to coherent suppression of dynamics of the quantum many-body modes, which has no classical analog. We demonstrate this new freezing phenomenon analytically (supported by large-scale numerics) for a general class of integrable quantum spin systems.

  5. Freeze-out parameters: lattice meets experiment

    E-print Network

    S. Borsanyi; Z. Fodor; S. D. Katz; S. Krieg; C. Ratti; K. K. Szabo

    2013-05-22

    We present our results for ratios of higher order fluctuations of electric charge as functions of the temperature. These results are obtained in a system of 2+1 quark flavors at physical quark masses and continuum extrapolated. We compare them to preliminary data on higher order moments of the net electric charge distribution from the STAR collaboration. This allows us to determine the freeze-out temperature and chemical potential from first principles. We also show continuum-extrapolated results for ratios of higher order fluctuations of baryon number. These will allow to test the consistency of the approach, by comparing them to the corresponding experimental data (once they become available) and thus extracting the freeze-out parameters in an independent way.

  6. Theoretic base of Edge Local Mode triggering by vertical displacements

    NASA Astrophysics Data System (ADS)

    Wang, Z. T.; He, Z. X.; Wang, Z. H.; Wu, N.; Tang, C. J.

    2015-05-01

    Vertical instability is studied with R-dependent displacement. For Solovev's configuration, the stability boundary of the vertical instability is calculated. The pressure gradient is a destabilizing factor which is contrary to Rebhan's result. Equilibrium parallel current density, j// , at plasma boundary is a drive of the vertical instability similar to Peeling-ballooning modes; however, the vertical instability cannot be stabilized by the magnetic shear which tends towards infinity near the separatrix. The induced current observed in the Edge Local Mode (ELM) triggering experiment by vertical modulation is derived. The theory provides some theoretic explanation for the mitigation of type-I ELMS on ASDEX Upgrade. The principle could be also used for ITER.

  7. The ammonia freeze explosion (AFEX) process

    Microsoft Academic Search

    Mark T. Holtzapple; Jae-Hoon Jun; Ganesh Ashok; Srinivas L. Patibandla; Bruce E. Dale

    1991-01-01

    The Ammonia Freeze Explosion (AFEX) process treats lignocellulose with high-pressure liquid ammonia, and then explosively\\u000a releases the pressure. The combined chemical effect (cellulose decrystallization) and physical effect (increased accessible\\u000a surface area) dramatically increase lignocellulose susceptibility to enzymatic attack. There are many adjustable parameters\\u000a in the AFEX process: ammonia loading, water loading, temperature, time, blowdown pressure, and number of treatments. The

  8. Preparation of mesoporous carbon by freeze drying

    Microsoft Academic Search

    H. Tamon; H. Ishizaka; T. Yamamoto; T. Suzuki

    1999-01-01

    Resorcinol–formaldehyde (RF) cryogels were synthesized by sol-gel polycondensation of resorcinol with formaldehyde and freeze drying with t-butanol. The cryogels were characterized by nitrogen adsorption and density measurements. Their porous properties were compared with those of RF aerogels prepared by supercritical drying with carbon dioxide. RF cryogels were mesoporous materials with large mesopore volumes >0.58 cm3\\/g. Although surface areas and mesopore

  9. An Improved Cryogen for Plunge Freezing

    PubMed Central

    Tivol, William F.; Briegel, Ariane; Jensen, Grant J.

    2011-01-01

    The use of an alkane mixture that remains liquid at 77 K to freeze specimens has advantages over the use of a pure alkane that is solid at 77 K. It was found that a mixture of methane and ethane did not give a cooling rate adequate to produce vitreous ice, but a mixture of propane and ethane did result in vitreous ice. Furthermore, the latter mixture produced less damage to specimens mounted on a very thin, fragile holey carbon substrate. PMID:18793481

  10. Freeze Thaw Durability of Modern Concrete Mixtures

    E-print Network

    Techniques #12;Current Measuring Techniques PCA photo ASTM C 231 PCA photo ASTM C 173 ASTM C 138 #12;Current Measuring Techniques PCA photo ASTM C 231 PCA photo ASTM C 173 ASTM C 138 These only measure volume!!! #12;0.0 0.1 0.2 0.3 0.4 0 2 4 6 8 10 air content ASTM C 231 (%) spacingfactor(mm) recommended for freeze

  11. Plant cold acclimation and freezing tolerance.

    PubMed

    Hincha, Dirk K; Zuther, Ellen

    2014-01-01

    This introductory chapter provides a brief overview of plant freezing tolerance and cold acclimation and describes the basic concepts and approaches that are currently followed to investigate these phenomena. We highlight the multidisciplinary nature of these investigations and the necessity to use methodologies from different branches of science, such as ecology, genetics, physiology, biochemistry, and biophysics, to come to a complete understanding of the complex adaptive mechanisms underlying plant cold acclimation. PMID:24852623

  12. Freeze out of the expanding system

    E-print Network

    V. K. Magas; L. P. Csernai; E. Molnar

    2007-02-22

    The freeze out (FO) of the expanding systems, created in relativistic heavy ion collisions, is discussed. We start with kinetic FO model, which realizes complete physical FO in a layer of given thickness, and then combine our gradual FO equations with Bjorken type system expansion into a unified model. We shall see that the basic FO features, pointed out in the earlier works, are not smeared out by the expansion.

  13. Freeze Crystallization Processes: Efficiency by Flexibility 

    E-print Network

    Heist, J. A.; Barron, T. S.

    1983-01-01

    and aromatics have very close bOlllng pOlnts, so fractional distillation is not practical. Extraction with tetramethylene sulfone or tetraethylene glycol (TeEG) is the usual method used to separate the aromatics from the parafins. The aromatics...-20, 1983 ~ CRUDE BTX [25 WTY. DE-PARIFFINED @ EXTRACT [60 WTY. TETRAETHYLENE GLYCOL) EUTECTIC POINT 230 240 220 210 0 x: W t 200 190 180 (CONVENTIONAL REFINING) ? ? ? FIGURE 6 8TX FREEZE REFINING The first of these is illustrated...

  14. A Four-Zone Furnace for Realization of Silver and Gold Freezing Points

    NASA Astrophysics Data System (ADS)

    Ripple, D. C.; Garrity, K. M.; Meyer, C. W.

    2003-09-01

    Recently, the Thermocouple Calibration Laboratory at the National Institute of Standards and Technology has used sodium heat-pipe furnaces for the realization of ITS-90 freezing points of aluminum, silver, and gold. When using a fixed-point cell mounted in a long silica-glass tube that extends to ambient temperature at the top of the furnace, we have observed significant thermal gradients along the well of the fixed-point cell, with the top of the well up to 0.1 K colder than the bottom. Furthermore, the heat-pipe lifetime is limited when used at the gold point (1064.18 °C) for more than a few hundred hours. To address these problems, we have designed and built a four-zone furnace based on a temperature-controlled, graphite isothermal block, suspended inside a three-zone tube furnace. The three-zone furnace is of a commercial design. The graphite block is enclosed in an alloy 600 (Inconel) can, allowing the graphite to be maintained in an argon atmosphere. The argon pressure is maintained at one atmosphere at all temperatures, thereby greatly reducing the stress on the can. Heaters in intimate contact with the can allow temperature control of the fourth inner zone to high accuracy. In this paper, the measured thermal stability and uniformity achieved with this furnace are presented. We also give results of test freezes of a silver freezing-point cell.

  15. Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling.

    PubMed

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

    2011-01-01

    Freezing patterns in the high alpine cushion plants Saxifraga bryoides, Saxifraga caesia, Saxifraga moschata and Silene acaulis were studied by infrared thermography at three reproductive stages (bud, anthesis, fruit development). The single reproductive shoots of a cushion froze independently in all four species at every reproductive stage. Ice formation caused lethal damage to the respective inflorescence. After ice nucleation, which occurred mainly in the stalk or the base of the reproductive shoot, ice propagated throughout that entire shoot, but not into neighboring shoots. However, anatomical ice barriers within cushions were not detected. The naturally occurring temperature gradient within the cushion appeared to interrupt ice propagation thermally. Consequently, every reproductive shoot needed an autonomous ice nucleation event to initiate freezing. Ice nucleation was not only influenced by minimum temperatures but also by the duration of exposure. At moderate subzero exposure temperatures (-4.3 to -7.7 °C) the number of frozen inflorescences increased exponentially. Due to efficient supercooling, single reproductive shoots remained unfrozen down to -17.4 °C (cooling rate 6 K h?¹). Hence, the observed freezing pattern may be advantageous for frost survival of individual inflorescences and reproductive success of high alpine cushion plants, when during episodic summer frosts damage can be avoided by supercooling. PMID:21151351

  16. Bacterial Community Composition in Lake Tanganyika: Vertical and Horizontal Heterogeneity

    Microsoft Academic Search

    Aaike De Wever; Koenraad Muylaert; Katleen Van der Gucht; Samuel Pirlot; Christine Cocquyt; Jean-Pierre Descy; Pierre-Denis Plisnier; Wim Vyverman

    2005-01-01

    Vertical and latitudinal differences in bacterial community composition (BCC) in Lake Tanganyika were studied during the dry season of 2002 by means of denaturing gradient gel electrophoresis analysis of PCR-amplified 16S RNA fragments. Dominant bands were sequenced and identified as members of the Cyanobacteria, Actinobacteria, Nitrospirae, green nonsulfur bacteria, and Firmicutes divisions and the Gamma- and Deltaproteobacteria subdivisions. The BCC

  17. Windchill and the risk of tissue freezing.

    PubMed

    Danielsson, U

    1996-12-01

    Low air temperatures and high wind speeds are associated with an increased risk of freezing of the exposed skin. P. A. Siple and C. F. Passel (Proc. Am. Phil. Soc. 89: 177-199, 1945) derived their windchill index from cooling experiments on a water-filled cylinder to quantify the risk of frostbite. Their results are reexamined here. It is found that their windchill index does not correctly describe the convective heat transfer coefficient (hc) for such a cylinder, the effect of the airspeed (v) is underestimated. New risk curves have been developed, based on the convection equations valid for cylinders in a cross flow, hc infinity v0.62, and tissue freezing data from the literature. An analysis of the data reveals a linear relationship between the frequency of finger frostbite and the surface temperature. This relation closely follows a normal distribution of finger-freezing temperatures, with an SD of 1 degree C. As the skin surface temperature falls from -4.8 to -7.8 degrees C, the risk of frostbite increases from 5 to 95%. These data indicate that the risk of finger frostbite is minor above an air temperature of -10 degrees C, irrespective of v, but below -25 degrees C there is a pronounced risk, even at low v. PMID:9018520

  18. Benchmarking numerical freeze/thaw models

    NASA Astrophysics Data System (ADS)

    Rühaak, Wolfram; Anbergen, Hauke; Molson, John; Grenier, Christophe; Sass, Ingo

    2015-04-01

    The modeling of freezing and thawing of water in porous media is of increasing interest, and for which very different application areas exist. For instance, the modeling of permafrost regression with respect to climate change issues is one area, while others include geotechnical applications in tunneling and for borehole heat exchangers which operate at temperatures below the freezing point. The modeling of these processes requires the solution of a coupled non-linear system of partial differential equations for flow and heat transport in space and time. Different code implementations have been developed in the past. Analytical solutions exist only for simple cases. Consequently, an interest has arisen in benchmarking different codes with analytical solutions, experiments and purely numerical results, similar to the long-standing DECOVALEX and the more recent "Geothermal Code Comparison" activities. The name for this freezing/ thawing benchmark consortium is INTERFROST. In addition to the well-known so-called Lunardini solution for a 1D case (case T1), two different 2D problems will be presented, one which represents melting of a frozen inclusion (case TH2) and another which represents the growth or thaw of permafrost around a talik (case TH3). These talik regions are important for controlling groundwater movement within a mainly frozen ground. First results of the different benchmark results will be shown and discussed.

  19. Fundamental technical elements of freeze-fracture/freeze-etch in biological electron microscopy.

    PubMed

    Carson, Johnny L

    2014-01-01

    Freeze-fracture/freeze-etch describes a process whereby specimens, typically biological or nanomaterial in nature, are frozen, fractured, and replicated to generate a carbon/platinum "cast" intended for examination by transmission electron microscopy. Specimens are subjected to ultrarapid freezing rates, often in the presence of cryoprotective agents to limit ice crystal formation, with subsequent fracturing of the specimen at liquid nitrogen cooled temperatures under high vacuum. The resultant fractured surface is replicated and stabilized by evaporation of carbon and platinum from an angle that confers surface three-dimensional detail to the cast. This technique has proved particularly enlightening for the investigation of cell membranes and their specializations and has contributed considerably to the understanding of cellular form to related cell function. In this report, we survey the instrument requirements and technical protocol for performing freeze-fracture, the associated nomenclature and characteristics of fracture planes, variations on the conventional procedure, and criteria for interpretation of freeze-fracture images. This technique has been widely used for ultrastructural investigation in many areas of cell biology and holds promise as an emerging imaging technique for molecular, nanotechnology, and materials science studies. PMID:25285532

  20. Design of gradient coils for magnetic resonance imaging

    Microsoft Academic Search

    K. Adamiak; B. K. Rutt; W. J. Dabrowski

    1992-01-01

    A numerical technique for designing gradient coils used in magnetic resonance imaging is presented. It is assumed that the coil consists of a finite number of polygonal turns, each carrying identical current. Coordinates of the vertices defining the turns are determined to minimize the mean-square deviation of the actual magnetic flux density from the ideal linear distribution. The zeroth-order Powell

  1. Vertical electromagnetic profiling (VEMP)

    SciTech Connect

    Lytle, R.J.

    1984-08-01

    Vertical seismic profiling (VSP) is based upon reception measurements performed in a borehole with a source near the ground surface. This technology has seen a surge in application and development in the last decade. The analogous concept of vertical electromagnetic profiling (VEMP) consists of reception measurements performed in a borehole with a source near the ground surface. Although the electromagnetic concept has seen some application, this technology has not been as systematically developed and applied as VSP. Vertical electromagnetic profiling provides distinct and complementary data due to sensing different physical parameters than seismic profiling. Certain of the advantages of VEMP are presented. 28 references, 7 figures.

  2. Vertical axis wind turbine

    SciTech Connect

    Kutcher, H.R.

    1984-05-15

    A Darrieus-type vertical axis wind turbine is disclosed which includes a vertically extending rotor tube mounted on a support structure with two or three rotor blades of troposkein configuration on the rotor tube for rotating the tube in response to wind energy and thereby drive a generator to produce electrical power. The turbine includes an erection hinge which permits assembly of the rotor tube and blades at close to ground level followed by upward hinging of the rotor assembly to a vertical position. It also includes a system for automatically lubricating the top bearing upon erection and a system for visually tensioning the guy cables.

  3. Vertical Line Test

    NSDL National Science Digital Library

    2010-01-01

    In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  4. Fast Self-Healing Gradients

    E-print Network

    Beal, Jacob

    We present CRF-Gradient, a self-healing gradient algorithm that provably reconfigures in O(diameter) time. Self-healing gradients are a frequently used building block for distributed self-healing systems, but previous ...

  5. Limitations of determining density or magnetic boundaries from the horizontal gradient of gravity or pseudogravity data.

    USGS Publications Warehouse

    Grauch, V.J.S.; Cordell, L.

    1987-01-01

    Offsets of horizontal-gradient magnitude maxima (gradient maxima) from a position directly over the boundary are predicted for cases where boundaries are not near-vertical or where several boundaries are close together. These are illustrated by offset equations; other factors which cause offsets are discussed briefly. -after Authors

  6. Glutathione protects Lactobacillus sanfranciscensis against freeze-thawing, freeze-drying, and cold treatment.

    PubMed

    Zhang, Juan; Du, Guo-Cheng; Zhang, Yanping; Liao, Xian-Yan; Wang, Miao; Li, Yin; Chen, Jian

    2010-05-01

    Lactobacillus sanfranciscensis DSM20451 cells containing glutathione (GSH) displayed significantly higher resistance against cold stress induced by freeze-drying, freeze-thawing, and 4 degrees C cold treatment than those without GSH. Cells containing GSH were capable of maintaining their membrane structure intact when exposed to freeze-thawing. In addition, cells containing GSH showed a higher proportion of unsaturated fatty acids in cell membranes upon long-term cold treatment. Subsequent studies revealed that the protective role of GSH against cryodamage of the cell membrane is partly due to preventing peroxidation of membrane fatty acids and protecting Na(+),K(+)-ATPase. Intracellular accumulation of GSH enhanced the survival and the biotechnological performance of L. sanfranciscensis, suggesting that the robustness of starters for sourdough fermentation can be improved by selecting GSH-accumulating strains. Moreover, the results of this study may represent a further example of mechanisms for stress responses in lactic acid bacteria. PMID:20208023

  7. Glutathione Protects Lactobacillus sanfranciscensis against Freeze-Thawing, Freeze-Drying, and Cold Treatment?

    PubMed Central

    Zhang, Juan; Du, Guo-Cheng; Zhang, Yanping; Liao, Xian-Yan; Wang, Miao; Li, Yin; Chen, Jian

    2010-01-01

    Lactobacillus sanfranciscensis DSM20451 cells containing glutathione (GSH) displayed significantly higher resistance against cold stress induced by freeze-drying, freeze-thawing, and 4°C cold treatment than those without GSH. Cells containing GSH were capable of maintaining their membrane structure intact when exposed to freeze-thawing. In addition, cells containing GSH showed a higher proportion of unsaturated fatty acids in cell membranes upon long-term cold treatment. Subsequent studies revealed that the protective role of GSH against cryodamage of the cell membrane is partly due to preventing peroxidation of membrane fatty acids and protecting Na+,K+-ATPase. Intracellular accumulation of GSH enhanced the survival and the biotechnological performance of L. sanfranciscensis, suggesting that the robustness of starters for sourdough fermentation can be improved by selecting GSH-accumulating strains. Moreover, the results of this study may represent a further example of mechanisms for stress responses in lactic acid bacteria. PMID:20208023

  8. Vertical neck lifting.

    PubMed

    Jacono, Andrew A; Talei, Benjamin

    2014-05-01

    The authors' vertical neck lifting procedure is an extended deep plane facelift, which elevates the skin and SMAS-platysma complex as a composite unit. The goal is to redrape cervicomental laxity vertically onto the face rather than laterally and postauricularly. The authors consider this an extended technique because it lengthens the deep plane flap from the angle of the mandible into the neck to release the cervical retaining ligaments that limit platysmal redraping. This technique does not routinely use midline platysmal surgery because it counteracts the extent of vertical redraping. A majority of aging face patients are good candidates for this procedure in isolation, but indications for combining vertical neck lifting with submental surgery are elucidated. PMID:24745389

  9. Vertical sleeve gastrectomy

    MedlinePLUS

    ... smaller stomach is about the size of a banana. It limits the amount of food you can ... staples. This creates a long vertical tube or banana-shaped stomach. The surgery does not involve cutting ...

  10. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  11. Type of automatic gradienter

    NASA Astrophysics Data System (ADS)

    Li, Shaohui; He, Liang; Zhang, Gang; Zhang, Zhipeng

    2000-05-01

    Aiming at the requirement that some kinds of big dynamo- electric equipments such as a dam gate of hydro-power plant or a elevator have to keep their balance in the process of being lifted and dropped, a novel and precise gradienter with high resolution and short response time is presented in this article. In this gradienter, the respective hydraulic pressure method is adopted.

  12. High Gradient Induction Cell

    SciTech Connect

    Caporaso, G J

    2004-11-29

    A concept being developed for high current electron beams may have application to HEDP and is described here. It involves the use of planar Blumlein stacks placed inside an induction cell. The output end of the Blumlein stack is applied across a high gradient insulator (HGI). These insulators have been used successfully in the presence of kilo Ampere-level electron beam currents for tens of nanoseconds at gradients of 20 MV/meter.

  13. MODELING OF THE FREEZING PROCESS FOR FISH IN VERTICAL PLATE FREEZERS

    E-print Network

    Gravdahl, Jan Tommy

    , carbohydrates and ash). The overall parameters are calculated by adding up the com- ponent's parameters [-] Temperature [K] k x i c FIGURE 3: Essential parameters The PDE is solved in MATLAB by discretizing in space

  14. Scattering-angle based filtering of the waveform inversion gradients

    NASA Astrophysics Data System (ADS)

    Alkhalifah, Tariq

    2014-01-01

    Full waveform inversion (FWI) requires a hierarchical approach to maneuver the complex non-linearity associated with the problem of velocity update. In anisotropic media, the non-linearity becomes far more complex with the potential trade-off between the multiparameter description of the model. A gradient filter helps us in accessing the parts of the gradient that are suitable to combat the potential non-linearity and parameter trade-off. The filter is based on representing the gradient in the time-lag normalized domain, in which the low scattering angle of the gradient update is initially muted out in the FWI implementation, in what we may refer to as a scattering angle continuation process. The result is a low wavelength update dominated by the transmission part of the update gradient. In this case, even 10 Hz data can produce vertically near-zero wavenumber updates suitable for a background correction of the model. Relaxing the filtering at a later stage in the FWI implementation allows for smaller scattering angles to contribute higher-resolution information to the model. The benefits of the extended domain based filtering of the gradient is not only it's ability in providing low wavenumber gradients guided by the scattering angle, but also in its potential to provide gradients free of unphysical energy that may correspond to unrealistic scattering angles.

  15. Design of Freeze-Drying Processes for Pharmaceuticals: Practical Advice

    Microsoft Academic Search

    Michael J. Pikal

    2004-01-01

    Design of freeze-drying processes is often approached with a “trial and error” experimental plan or, worse yet, the protocol used in the first laboratory run is adopted without further attempts at optimization. Consequently, commercial freeze-drying processes are often neither robust nor efficient. It is our thesis that design of an “optimized” freeze-drying process is not particularly difficult for most products,

  16. Trends in Microwave-Assisted Freeze Drying of Foods

    Microsoft Academic Search

    X. Duan; M. Zhang; A. S. Mujumdar; R. Wang

    2010-01-01

    Microwave-assisted freeze drying (MFD) can be accomplished in two distinct ways: freeze drying assisted concurrently with microwave application (MFD-1) and freeze drying and assisted microwave\\/vacuum microwave drying in two consecutive separate drying stages (MFD-2). MFD is a rapid dehydration technique that can be applied to certain foods, particularly to seafoods, solid soup, and fruits and vegetables. MFD involves much less

  17. Arabidopsis ESK1 encodes a novel regulator of freezing tolerance

    Microsoft Academic Search

    Zhanguo Xin; Ajin Mandaokar; Junping Chen; Robert L. Last; John Browse

    2007-01-01

    Summary The eskimo1 (esk1) mutation of Arabidopsis resulted in a 5.5? C improvement in freezing tolerance in the absence of cold acclimation. Here we show that the increase in freezing tolerance is not associated with any increase in the ability to survive drought or salt stresses, which are similar to freezing in their induction of cellular dehydration. Genome-wide comparisons of

  18. Freezing precipitation in the Southeastern United States 

    E-print Network

    Young, William Robert

    1978-01-01

    FREEZING PRECIPITATION IN THE SOUTHEASTERN UNITED STATES A Thesis NILLIAN ROBERT YOUNG Sxhmitted to the Graduate College of Texas ASN University in partial fulfillsent o( the requirement for the decree of RASTER OF SCIENCE NaY 19'7B rV, 'or... Suoject: Net *oroloRY FREE 1NG PRE fPITATION IN THE SOUTHEASTERN UNITED STATES A Thesis 'NXLDIAN ROBERT YOUNG Approved as to style and coni ent hy: Chairman of Committe "Leaser (Head of Departne. "i Niay 19y8 443?10 Freesing Precipitation...

  19. A molecular dynamics study of freezing in a confined geometry

    NASA Technical Reports Server (NTRS)

    Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel

    1992-01-01

    The dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls is studied by computer simulation. The time development of ordering is quantified and a novel freezing mechanism is observed. The liquid forms layers and subsequent in-plane ordering within a layer is accompanied by a sharpening of the layer in the transverse direction. The effects of channel size, the methods of quench, the liquid-wall interaction and the roughness of walls on the freezing mechanism are elucidated. Comparison with recent experiments on freezing in confined geometries is presented.

  20. Anoxia tolerance and freeze tolerance in hatchling turtles.

    PubMed

    Dinkelacker, S A; Costanzo, J P; Lee, R E

    2005-04-01

    Freezing survival in hatchling turtles may be limited by ischemic anoxia in frozen tissues and the associated accumulation of lactate and reactive oxygen species (ROS). To determine whether mechanisms for coping with anoxia are also important in freeze tolerance, we examined the association between capacities for freezing survival and anoxia tolerance in hatchlings of seven species of turtles. Tolerance to freezing (-2.5 degrees C) was high in Emydoidea blandingii, Chrysemys picta, Terrapene ornata, and Malaclemys terrapin and low in Graptemys geographica, Chelydra serpentina, and Trachemys scripta. Hatchlings survived in a N(2) atmosphere at 4 degrees C for periods ranging from 17 d (M. terrapin) to 50 d (G. geographica), but survival time was not associated with freeze tolerance. Lactate accumulated during both stresses, but plasma levels in frozen/thawed turtles were well below those found in anoxia-exposed animals. Activity of the antioxidant enzyme catalase in liver increased markedly with anoxia exposure in most species, but increased with freezing/thawing only in species with low freeze tolerance. Our results suggest that whereas oxygen deprivation occurs during somatic freezing, freeze tolerance is not limited by anoxia tolerance in hatchling turtles. PMID:15739066

  1. Design of a blood-freezing system for leukemia research

    NASA Technical Reports Server (NTRS)

    Williams, T. E.; Cygnarowicz, T. A.

    1978-01-01

    Leukemia research involves the use of cryogenic freezing and storage equipment. In a program being carried out at the National Cancer Institute (NCI), bone marrow (white blood cells) was frozen using a standard cryogenic biological freezer. With this system, it is difficult to maintain the desired rate of freezing and repeatability from sample to sample. A freezing system was developed that satisfies the requirements for a repeatable, constant freezing rate. The system was delivered to NIC and is now operational. This report describes the design of the major subsystems, the analyses, the operating procedure, and final system test results.

  2. Effects of Electric and Magnetic Field on Freezing and Possible Relevance in Freeze Drying

    Microsoft Academic Search

    M. W. Woo; A. S. Mujumdar

    2010-01-01

    Application of an electric or magnetic field can significantly affect the freezing characteristics of water. A DC electric field will tend to induce ice nucleation at a lower degree of supercooling, and there is evidence to show that an AC electric field delays the onset of ice nucleation. Industrial research has shown that a magnetic field can be used to

  3. Method and apparatus for determining vertical heat flux of geothermal field

    DOEpatents

    Poppendiek, Heinz F. (LaJolla, CA)

    1982-01-01

    A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.

  4. Effect of freeze drying and protectants on viability of the biocontrol yeast Candida sake

    Microsoft Academic Search

    M Abadias; A Benabarre; N Teixidó; J Usall; I Viñas

    2001-01-01

    The effects of freezing method, freeze drying process, and the use of protective agents on the viability of the biocontrol yeast Candida sake were studied. Freezing at ?20°C was the best method to preserve the viability of C. sake cells after freeze drying using 10% skim milk as a protectant (28.9% survival). Liquid nitrogen freezing caused the highest level of

  5. Effect of repeated freeze-thaw cycles on geographically different populations of the freeze-tolerant worm Enchytraeus albidus (Oligochaeta).

    PubMed

    Fisker, Karina Vincents; Holmstrup, Martin; Malte, Hans; Overgaard, Johannes

    2014-11-01

    Freeze-tolerant organisms survive internal ice formation; however, the adaptations to repeated freeze-thaw cycles are often not well investigated. Here we report how three geographically different populations of Enchytraeus albidus (Germany, Iceland and Svalbard) respond to three temperature treatments - constant thawed (0°C), constant freezing (-5°C) and fluctuating temperature (0 to -5°C) - over a period of 42 days. Survival varied between treatments and populations such that enchytraeids from arctic locations had a higher survival following prolonged freeze periods compared with temperate populations. However, enchytraeids from temperate locations had the same survival rate as arctic populations when exposed to repeated freeze-thaw events. Across all populations, metabolic rate decreased markedly in frozen animals (-5°C) compared with thawed controls (0°C). This decrease is likely due to the lower temperature of frozen animals, but also to the transition to the frozen state per se. Animals exposed to repeated freeze-thaw events had an intermediate metabolic rate and freeze-thaw events were not associated with pronounced excess energetic costs. Overwintering under either condition was not associated with a decrease in lipid content; however, during exposure to constant freezing and repeated freeze-thaw events there was a noticeable decrease in carbohydrate stores over time. Thus, animals exposed to constant freezing showed a decrease in glycogen stores, while both glucose and glycogen content decreased over time when the organisms were exposed to repeated freezing. The results therefore suggest that carbohydrate resources are important as a fuel for E. albidus during freezing whereas lipid resources are of marginal importance. PMID:25214492

  6. RESPONSES TO FREEZING EXPOSURE OF HATCHLING TURTLES TRACHEMYS SCRIPTA ELEGANS: FACTORS INFLUENCING THE DEVELOPMENT OF FREEZE TOLERANCE BY REPTILES

    Microsoft Academic Search

    THOMAS A. CHURCHILL; KENNETH B. STOREY

    Summary Hatchling red-eared turtles Trachemys (=Pseudemys) scripta elegans (Wied) from a Louisiana population display a significant ability to withstand the freezing of extracellular body fluids. All animals survived at least 2 h of freezing at -2.5 or —4°C. At -2.5°C, survival declined to 50% after 6h of freezing and no animals recovered after 24 h or longer, when mean ice

  7. Vertical electron transistor (VET) in GaAs with a heterojunction (AlGaAs-GaAs) cathode

    NASA Astrophysics Data System (ADS)

    Mishra, U.; Maki, P. A.; Wendt, J. R.; Schaff, W.; Kohn, E.; Eastman, L. F.

    1984-02-01

    The successful fabrication of submicrometer channel length (0.75 micron) and gate length (0.15 micron) vertical electron transistors with AlGaAs cathodes is reported. Lack of electron velocity enhancement has been proposed to be due to high operating channel temperatures, and low temperature measurements were hindered by carrier freeze-out.

  8. Zone Freezing Study for Pyrochemical Process Waste Minimization

    SciTech Connect

    Ammon Williams

    2012-05-01

    Pyroprocessing technology is a non-aqueous separation process for treatment of used nuclear fuel. At the heart of pyroprocessing lies the electrorefiner, which electrochemically dissolves uranium from the used fuel at the anode and deposits it onto a cathode. During this operation, sodium, transuranics, and fission product chlorides accumulate in the electrolyte salt (LiCl-KCl). These contaminates change the characteristics of the salt overtime and as a result, large volumes of contaminated salt are being removed, reprocessed and stored as radioactive waste. To reduce the storage volumes and improve recycling process for cost minimization, a salt purification method called zone freezing has been proposed at Korea Atomic Energy Research Institute (KAERI). Zone freezing is melt crystallization process similar to the vertical Bridgeman method. In this process, the eutectic salt is slowly cooled axially from top to bottom. As solidification occurs, the fission products are rejected from the solid interface and forced into the liquid phase. The resulting product is a grown crystal with the bulk of the fission products near the bottom of the salt ingot, where they can be easily be sectioned and removed. Despite successful feasibility report from KAERI on this process, there were many unexplored parameters to help understanding and improving its operational routines. Thus, this becomes the main motivation of this proposed study. The majority of this work has been focused on the CsCl-LiCl-KCl ternary salt. CeCl3-LiCl-KCl was also investigated to check whether or not this process is feasible for the trivalent species—surrogate for rare-earths and transuranics. For the main part of the work, several parameters were varied, they are: (1) the retort advancement rate—1.8, 3.2, and 5.0 mm/hr, (2) the crucible lid configurations—lid versus no-lid, (3) the amount or size of mixture—50 and 400 g, (4) the composition of CsCl in the salt—1, 3, and 5 wt%, and (5) the temperature differences between the high and low furnace zones—200 and 300 ?C. During each experiment, the temperatures at selected locations around the crucible were measured and recorded to provide temperature profiles. Following each experiment, samples were collected and elemental analysis was done to determine the composition of iii the salt. Several models—non-mixed, well-mixed, Favier, and hybrid—were explored to describe the zone freezing process. For CsCl-LiCl-KCl system, experimental results indicate that through this process up to 90% of the used salt can be recycled, effectively reducing waste volume by a factor of ten. The optimal configuration was found to be a 5.0 mm/hr rate with a lid configuration and a ?T of 200°C. The larger 400 g mixtures had recycle percentages similar to the 50 g mixtures; however, the throughput per time was greater for the 400 g case. As a result, the 400 g case is recommended. For the CeCl3-LiCl-KCl system, the result implies that it is possible to use this process to separate the rare-earth and transuranics chlorides. Different models were applied to only CsCl ternary system. The best fit model was the hybrid model as a result of a solute transport transition from non- mixed to well-mixed throughout the growing process.

  9. Freezing stress response in woody tissues observed using low-temperature scanning electron microscopy and freeze substitution techniques.

    PubMed

    Malone, S R; Ashworth, E N

    1991-03-01

    The objective of the current research was to examine the response of woody plant tissues to freezing stress by using scanning electron microscopy (SEM). Nonsupercooling species red osier dogwood (Cornus stolonifera Michx.), weeping willow (Salix babylonica L.), and corkscrew willow (Salix matsudana Koidz. f. tortuosa Rehd.) survived freezing stress as low as -60 degrees C. Cell collapse of ray parenchyma cells of these species was expected but did not occur. It was concluded that ray parenchyma cells of these species do not fit into either the supercooling or extracellular freezing classifications. Tissues from flowering dogwood (Cornus florida L.), apple (Malus domestica Borkh. cv "Starking III"), red oak (Quercus rubra L.), scarlet oak (Quercus coccinea Muench.), and red ash (Fraxinus pennsylvanica Marsh) were confirmed as supercooling species, and did not survive exposures below -40 degrees C. Ray parenchyma cells of these species did not collapse in response to freezing stress, as was expected. Cell collapse along the margins of voids were observed in bark of all seven species. Voids were the result of extracellular ice crystals formed in the bark during exposure to freezing stress. Tissues prepared by freeze substitution techniques were found to be adequately preserved when compared to those prepared by conventional fixation and low temperature SEM techniques. A freezing protocol for imposing freezing stress at temperatures lower than experienced naturally in the area where the study was conducted was developed that produced responses comparable to those observed in specimens collected in the field during natural freezing events. PMID:16668066

  10. [Rapid freezing of biologic tissue. Measurement of temperature and rate of freezing by thin-layer thermocouple].

    PubMed

    Escaig, J; Géraud, G; Nicolas, G

    1977-06-13

    An apparatus for rapid freezing of biological tissues by contact with a copper block cooled by liquid helium has been devised to reduce the contamination of copper block surface. It prevents the precooling of the specimen while going through the layers of cold helium gas surrounding the copper block and reduces the quantity of helium necessary for freezing. It also enables one to obtain easily reproducible results from freezing by immersion in liquid coolants. Freezing rates are measured directly, related to the specimen thickness, by a thin film thermocouple; its low thermal inertia gives speed measurements of the order of 100,000 degrees C/s. PMID:408040

  11. High gradient superconducting quadrupoles

    SciTech Connect

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed.

  12. Uniform gradient expansions

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2015-06-01

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  13. HIGH GRADIENT INDUCTION ACCELERATOR

    SciTech Connect

    Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Nunnally, W; Paul, A; Poole, B; Rhodes, M; Sanders, D; Selenes, K; Sullivan, J; Wang, L; Watson, J

    2007-06-21

    A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.

  14. Vertical emitting aperture nanoantennas.

    PubMed

    Yaacobi, Ami; Timurdogan, Erman; Watts, Michael R

    2012-05-01

    Herein we propose, theoretically investigate, and numerically demonstrate a compact design for a vertical emitter at a wavelength of 1.5 ?m based on nanophotonic aperture antennas coupled to a dielectric waveguide. The structure utilizes a plasmonic antenna placed above a Si3N4 waveguide with a ground plane for breaking the up-down symmetry and increasing the emission efficiency. Three-dimensional (3-D) finite-difference time-domain (FDTD) simulations reveal that up to 60% vertical emission efficiency is possible in a structure only four wavelengths long with a 3 dB bandwidth of over 300 nm. PMID:22555702

  15. Temperature dependence of vertical transport in quantum Hall multilayers

    NASA Astrophysics Data System (ADS)

    Walling, H. A.; Dougherty, D. P.; Druist, D. P.; Gwinn, E. G.; Maranowski, K. D.; Gossard, A. C.

    2002-01-01

    We study the temperature dependence of vertical transport in GaAs/Al 0.1Ga 0.9As multilayers, in the regime of the integer quantum Hall effect. At low temperatures, vertical transport in quantum Hall states occurs on a two-dimensional chiral sheath of edge states near the sidewalls of the sample mesas. At higher temperatures, variable-range hopping through the bulk of the sample dominates. To extend the temperature range of sheath-dominated transport, we increase the device perimeters using fractal-shaped mesas defined by e-beam lithography. We report on the freeze-out of bulk transport and the nearly linear increase of the sheath conductivity with temperature.

  16. Gradient Refractive Index Lenses.

    ERIC Educational Resources Information Center

    Morton, N.

    1984-01-01

    Describes the nature of gradient refractive index (GRIN) lenses, focusing on refraction in these materials, focal length of a thin Wood lens, and on manufacturing of such lenses. Indicates that GRIN lenses of small cross section are in limited production with applications suggested for optical communication and photocopying fields. (JN)

  17. SFT: a consistent checkpointing algorithm with shorter freezing time

    Microsoft Academic Search

    Xiaohui Wei; Jiubin Ju

    1998-01-01

    SFT algorithm, a consistent checkpointing algorithm with shorter freezing time, is presented in this paper. SFT is able to implement fault-tolerance in distributed systems. The features of the algorithm include shorter freezing time, lower overhead, and simple roll backing. To reduce checkpointing time, a special control message (Munblock) is used to ensure that at any given time a process can

  18. St. Lawrence River Freeze-Up Forecast Procedure.

    ERIC Educational Resources Information Center

    Assel, R. A.

    A standard operating procedure (SOP) is presented for calculating the date of freeze-up on the St. Lawrence River at Massena, N.Y. The SOP is based on two empirical temperature decline equations developed for Kingston, Ontario, and Massena, N.Y., respectively. Input data needed to forecast freeze-up consist of the forecast December flow rate and…

  19. Studies on Freezing RAM Semen in Absence of Glycerol

    Microsoft Academic Search

    Abdelhady Abdelhakeam Abdelnaby

    1988-01-01

    Glycerol is widely used as a major cryoprotective agent for freezing spermatozoa of almost all species. However, it reduces fertility of sheep inseminated cervically compared with intrauterine insemination. Studies were conducted to develop a method and procedure for freezing ram semen in the absence of glycerol. Post -thaw survival of ram spermatozoa frozen in the absence of glycerol was affected

  20. Promising freeze protection alternatives in solar domestic hot water systems

    Microsoft Academic Search

    1997-01-01

    Since the gains associated with solar thermal energy technologies are comparatively small in relation to the required capital investment, it is vital to maximize conversion efficiency. While providing the necessary function of freeze protection, the heat exchanger commonly included in solar domestic water heating systems represents a system inefficiency. This thesis explores two alternate methods of providing freeze protection without

  1. Ponds Freeze in Winter -- Why Doesn't the Ocean?

    NSDL National Science Digital Library

    New England Aquarium

    2011-01-01

    In this activity, learners explore how salt water freezes in comparison to fresh water. Use this experiment to consider how pond animals survive cold winters in comparison to animals that live in the ocean. This resource includes information about freezing points as well as examples of how different animals respond to the winter cold.

  2. Freeze Out Process with In-Medium Nucleon Mass

    E-print Network

    Sven Zschocke; Laszlo P. Csernai; Etele Molnár; Jaakko Manninen; Agnes Nyiri

    2006-10-16

    We investigate the kinetic freeze out scenario of a nucleon gas through a finite layer. The in-medium mass modification of nucleons and it's impact on the freeze out process is studied. A considerable modification of the thermodynamical parameters temperature, flow-velocity, energy density and particle density has been found in comparison with evaluations which use a constant vacuum nucleon mass.

  3. Using infrared thermography to study freezing in plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Factors that determine when and to what extent a plant will freeze are complex. While thermocouples have served as the main method of monitoring the freezing process in plants, infrared thermography offers distinct advantages, and the use of this latter technology has provided new insights on the p...

  4. Determination of freeze-out conditions from lattice QCD calculations

    NASA Astrophysics Data System (ADS)

    Karsch, Frithjof

    2012-12-01

    Freeze-out conditions in Heavy Ion Collisions are generally determined by comparing experimental results for ratios of particle yields with theoretical predictions based on applications of the Hadron Resonance Gas model. We discuss here how this model dependent determination of freeze-out parameters may eventually be replaced by theoretical predictions based on equilibrium QCD thermodynamics.

  5. Logistic Regression Analysis of Freezing Tolerance in Winter Wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four winter wheat cultivars, Eltan, Froid, Kestrel, and Tiber, were cold-acclimated for five weeks and then tested for freezing tolerance in a programmable freezer. The temperature of the soil was recorded every two minutes and the freezing episode was described as five parameters: the minimum temp...

  6. Vertical shaft windmill

    NASA Technical Reports Server (NTRS)

    Grana, D. C.; Inge, S. V., Jr. (inventors)

    1983-01-01

    A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

  7. 14 CFR 25.1455 - Draining of fluids subject to freezing.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Draining of fluids subject to freezing. 25.1455 Section 25...Miscellaneous Equipment § 25.1455 Draining of fluids subject to freezing. If fluids subject to freezing may be drained...

  8. 14 CFR 25.1455 - Draining of fluids subject to freezing.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 2010-01-01 false Draining of fluids subject to freezing. 25.1455 Section 25...Miscellaneous Equipment § 25.1455 Draining of fluids subject to freezing. If fluids subject to freezing may be drained...

  9. 14 CFR 25.1455 - Draining of fluids subject to freezing.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Draining of fluids subject to freezing. 25.1455 Section 25...Miscellaneous Equipment § 25.1455 Draining of fluids subject to freezing. If fluids subject to freezing may be drained...

  10. 14 CFR 25.1455 - Draining of fluids subject to freezing.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Draining of fluids subject to freezing. 25.1455 Section 25...Miscellaneous Equipment § 25.1455 Draining of fluids subject to freezing. If fluids subject to freezing may be drained...

  11. 14 CFR 25.1455 - Draining of fluids subject to freezing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Draining of fluids subject to freezing. 25.1455 Section 25...Miscellaneous Equipment § 25.1455 Draining of fluids subject to freezing. If fluids subject to freezing may be drained...

  12. Metallicity gradients in disks. Do galaxies form inside-out?

    NASA Astrophysics Data System (ADS)

    Pilkington, K.; Few, C. G.; Gibson, B. K.; Calura, F.; Michel-Dansac, L.; Thacker, R. J.; Mollá, M.; Matteucci, F.; Rahimi, A.; Kawata, D.; Kobayashi, C.; Brook, C. B.; Stinson, G. S.; Couchman, H. M. P.; Bailin, J.; Wadsley, J.

    2012-04-01

    Aims: We examine radial and vertical metallicity gradients using a suite of disk galaxy hydrodynamical simulations, supplemented with two classic chemical evolution approaches. We determine the rate of change of gradient slope and reconcile the differences existing between extant models and observations within the canonical "inside-out" disk growth paradigm. Methods: A suite of 25 cosmological disks is used to examine the evolution of metallicity gradients; this consists of 19 galaxies selected from the RaDES (Ramses Disk Environment Study) sample, realised with the adaptive mesh refinement code ramses, including eight drawn from the "field" and six from "loose group" environments. Four disks are selected from the MUGS (McMaster Unbiased Galaxy Simulations) sample, generated with the smoothed particle hydrodynamics (SPH) code gasoline. Two chemical evolution models of inside-out disk growth were employed to contrast the temporal evolution of their radial gradients with those of the simulations. Results: We first show that generically flatter gradients are observed at redshift zero when comparing older stars with those forming today, consistent with expectations of kinematically hot simulations, but counter to that observed in the Milky Way. The vertical abundance gradients at ~1-3 disk scalelengths are comparable to those observed in the thick disk of the Milky Way, but significantly shallower than those seen in the thin disk. Most importantly, we find that systematic differences exist between the predicted evolution of radial abundance gradients in the RaDES and chemical evolution models, compared with the MUGS sample; specifically, the MUGS simulations are systematically steeper at high-redshift, and present much more rapid evolution in their gradients. Conclusions: We find that the majority of the models predict radial gradients today which are consistent with those observed in late-type disks, but they evolve to this self-similarity in different fashions, despite each adhering to classical "inside-out" growth. We find that radial dependence of the efficiency with which stars form as a function of time drives the differences seen in the gradients; systematic differences in the sub-grid physics between the various codes are responsible for setting these gradients. Recent, albeit limited, data at redshift z ~ 1.5 are consistent with the steeper gradients seen in our SPH sample, suggesting a modest revision of the classical chemical evolution models may be required.

  13. The role of seawater freezing in the formation of subsurface brines

    NASA Astrophysics Data System (ADS)

    Herut, Barak; Starinsky, Avraham; Katz, Amitai; Bein, Amos

    1990-01-01

    Several mechanisms (evaporation, water-rock interaction, ultra-filtration) have been suggested to explain the evolution of ubiquitous Ca-chloride subsurface brines. In the present paper, the freezing of seawater in polar regions, and in even wider areas during glacial periods, is proposed as an additional possible path of brine formation. Four detailed seawater freezing experiments to -14°C (resulting in a concentration factor of about 5) were carried out, and Na, K, Ca, Mg, Sr, Cl, SO 4, and Br were analysed in the residual brines and in the ice. Br and Sr, whose behavior during the freezing of seawater is reported here for the first time, show a conservative behavior throughout the studied temperature range. Our data and earlier literature show that the high salinities, which are common in subsurface brines (>300 g/l), may be obtained by the removal of H 2O as ice in the primary glacial environment. The decrease in the Na/Cl ratio is caused by the crystallization of mirabilite (Na 2SO 4 · 10H 2O), supplemented by hydrohalite (NaCl · 2H 2O). Sulfate is removed both in mirabilite and by bacterial reduction. The brine then migrates to the subsurface, heats-up under the local geothermal gradient, and interacts with the adjacent rocks. At this stage, it may be diluted by meteoric waters, its Mg/Ca ratio decreases (dolomitization and chloritization), the SO 4/Cl ratio varies according to the local gypsum-anhydrite equilibrium conditions, and the Ca/(SO 4 + HCO 3) ratio increases as a result of dolomitization or chloritization. The interaction with rocks in the subsurface may affect both the original 87Sr /86Sr and the 18O /16O ratios of the brine. Although several of the processes which lead to the formation of Ca-chloride brines are common for both the evaporative and the freezing models, the Na-Br-Cl relationship in a given brine can be used to discriminate between the two modes of brine evolution. Several subsurface brines from the Canadian Shield and one brine from Finland are used as examples of the seawater freezing model, and an explanation is proposed for the necessary mass production of brines in glacial environments.

  14. Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets

    NASA Technical Reports Server (NTRS)

    Dorsch, R. G.; Hacker, P. T.

    1950-01-01

    A photomicrographic technique for investigating eupercooled. water droplets has been devised and. used. to determine the spontaneous freezing temperatures of eupercooled. water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained. The average spontaneous freezing temperature decreased with decrease in the size of the droplets. The effect of size on the spontaneous freezing temperature was particularly marked below 60 microns. Frequency-distribution curves of the spontaneous freezing temperatures observed for droplets of a given size were obtained. Although no droplet froze at a temperature above 20 0 F, all droplets melted at 32 F. Results obtained with a copper support did not differ essentially from those obtained with a platinum surface.

  15. Freeze plug proves safe, economical in riser repair

    SciTech Connect

    Nelson, M.J. [Exxon Co. U.S.A., New Orleans, LA (United States)

    1995-05-01

    In October 1992, Exxon Pipeline Co., Houston, performed in the Gulf of Mexico what the company believes to have been the first underwater freeze-plug procedure. To form a plug, water in a small section of the pipe is frozen with liquid nitrogen. In partially replacing a 10-in. riser at South Marsh Island Block 6A, Exxon Pipeline worked closely with a freeze-plug service company to minimize environmental and personnel exposure and to avoid the chance of an oil spill. The freeze plug reduced the time the pipe was open-ended during the repair, and hydrotesting the freeze plug area and repair section ensured integrity. The paper describes onshore testing of the procedures, pre-work surface cleaning, and the freeze-plug procedure.

  16. Evaluation and Validation of the Messinger Freezing Fraction

    NASA Technical Reports Server (NTRS)

    Anderson, David N.; Tsao, Jen-Ching

    2005-01-01

    One of the most important non-dimensional parameters used in ice-accretion modeling and scaling studies is the freezing fraction defined by the heat-balance analysis of Messinger. For fifty years this parameter has been used to indicate how rapidly freezing takes place when super-cooled water strikes a solid body. The value ranges from 0 (no freezing) to 1 (water freezes immediately on impact), and the magnitude has been shown to play a major role in determining the physical appearance of the accreted ice. Because of its importance to ice shape, this parameter and the physics underlying the expressions used to calculate it have been questioned from time to time. Until now, there has been no strong evidence either validating or casting doubt on the current expressions. This paper presents experimental measurements of the leading-edge thickness of a number of ice shapes for a variety of test conditions with nominal freezing fractions from 0.3 to 1.0. From these thickness measurements, experimental freezing fractions were calculated and compared with values found from the Messinger analysis as applied by Ruff. Within the experimental uncertainty of measuring the leading-edge thickness, agreement of the experimental and analytical freezing fraction was very good. It is also shown that values of analytical freezing fraction were entirely consistent with observed ice shapes at and near rime conditions: At an analytical freezing fraction of unity, experimental ice shapes displayed the classic rime shape, while for conditions producing analytical freezing fractions slightly lower than unity, glaze features started to appear.

  17. An improved microscope stage for direct observation of freezing and freeze drying.

    PubMed

    Nail, S L; Her, L M; Proffitt, C P; Nail, L L

    1994-08-01

    A microscope stage for observation of freezing and freeze drying is described. The stage uses thermoelectric (Peltier) heaters configured in two stages, with circulating fluid as a heat sink on the high temperature side. Lowest attainable sample temperature is about -47 degrees C. Principal advantages of this system are closed-loop control of stage temperature, rapid response to changes in temperature set point, and improved documentation of experiments by use of a video recorder system with a character generator which allows display of sample identity and temperature. Accuracy of measuring the sample temperature in the field of view was validated by comparing observed values of eutectic melting with published values for a series of solutes with eutectic temperatures in the range from -2 degrees C to -32 degrees C. Good agreement was obtained throughout this range. PMID:7971708

  18. Uncertainty of data obtained in SRF cavity vertical test

    E-print Network

    He, Feisi

    2013-01-01

    Vertical test is a commonly used experimental method to qualify Superconducting Radio Frequency (SRF) cavities. Taking the experiences at Jefferson Lab (JLab) in US for example, over thousand of vertical tests have been performed on over 500 different cavities up to now [1]. Most of the tests at JLab followed the method as described in [1], but all the uncertainties of the calculated quality factors as well as the gradients were in-accurate due to the wrong algorithm used. In this paper, a first-principle method was applied to analyze the uncertainty of the data, and the results were compared with those in [1] under typical experiment conditions.

  19. Immersion freezing of birch pollen washing water

    NASA Astrophysics Data System (ADS)

    Augustin, S.; Wex, H.; Niedermeier, D.; Pummer, B.; Grothe, H.; Hartmann, S.; Tomsche, L.; Clauss, T.; Voigtländer, J.; Ignatius, K.; Stratmann, F.

    2013-11-01

    Birch pollen grains are known to be ice nucleating active biological particles. The ice nucleating activity has previously been tracked down to biological macromolecules that can be easily extracted from the pollen grains in water. In the present study, we investigated the immersion freezing behavior of these ice nucleating active (INA) macromolecules. Therefore we measured the frozen fractions of particles generated from birch pollen washing water as a function of temperature at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Two different birch pollen samples were considered, with one originating from Sweden and one from the Czech Republic. For the Czech and Swedish birch pollen samples, freezing was observed to start at -19 and -17 °C, respectively. The fraction of frozen droplets increased for both samples down to -24 °C. Further cooling did not increase the frozen fractions any more. Instead, a plateau formed at frozen fractions below 1. This fact could be used to determine the amount of INA macromolecules in the droplets examined here, which in turn allowed for the determination of nucleation rates for single INA macromolecules. The main differences between the Swedish birch pollen and the Czech birch pollen were obvious in the temperature range between -17 and -24 °C. In this range, a second plateau region could be seen for Swedish birch pollen. As we assume INA macromolecules to be the reason for the ice nucleation, we concluded that birch pollen is able to produce at least two different types of INA macromolecules. We were able to derive parameterizations for the heterogeneous nucleation rates for both INA macromolecule types, using two different methods: a simple exponential fit and the Soccer ball model. With these parameterization methods we were able to describe the ice nucleation behavior of single INA macromolecules from both the Czech and the Swedish birch pollen.

  20. Fabrication of porous ceramics by freeze-casting/freeze-drying. Final report, April 1991-December 1992

    SciTech Connect

    Johnson, S.M.; Gusman, M.I.

    1993-04-01

    Porous ceramics have many applications in the gas industry, including gas separation, filtration, catalyst supports and substrates, lightweight insulation, and burners. The report explores the fabrication of porous ceramics by a new approach involving the use of cryogenic processing techniques such as freeze-drying, to characterize the materials formed in this way, and to evaluate the potential of the techniques for making porous ceramics for specific gas industry applications.

  1. Effects of freezing rates and cryoprotectant on thermal expansion of articular cartilage during freezing process.

    PubMed

    Xu, Y; Sun, H J; Lv, Y; Zou, J C; Lin, B L; Hua, T C

    2013-01-01

    The intact articular cartilage has not yet been successfully preserved at low temperature most likely due to the volume expansion from water to ice during freezing. The objective of this current study focuses on examining thermal expansion behavior of articular cartilage (AC) during freezing from 0 degree C to -100 degree C. Thermo Mechanical Analysis (TMA) was used to investigate the effects of different concentrations of dimethyl sulphoxide (DMSO) (0%, 10%, 30% and 60% v/v) and different freezing rates (1 C/min, 3 C/min and 5 C/min). The results showed that: (1) the inhomogeneous thermal expansion (or contraction) presents due to inhomogeneous water distributions in articular cartilage during freezing, which also may be the most likely reason that the matrix has been damaged in cryopreserved intact articular cartilage; (2) at the phase transition temperature range, the maximum thermal strain change value for 5C/min is approximately 1.45 times than that for 1 C/min, but the maximum thermal expansion coefficient of the later is about six times than that of the former; (3) the thermal expansion coefficient decreases with increasing cooling rate at the unfrozen temperature region, but some opposite results are obtained at the frozen temperature region; (4) the higher the DMSO concentration is, at the phase change temperature region, the smaller the thermal strain change as well as the maximum thermal expansion coefficient are, but DMSO concentration exhibits little effect on the thermal expansion coefficient at both unfrozen and frozen region. Once the DMSO concentration increasing enough, e.g. 60% v/v, the thermal strain decreases linearly and smoothly without any abrupt change due to little or no ice crystal forms (i.e. vitrification) in frozen articular cartilage. This study may improve our understanding of the thermal expansion (or contraction) behavior of cryopreserved articular cartilage and it may be useful for the future study on cryopreservation of intact articular cartilage. PMID:23995399

  2. Effect of wettability on sessile drop freezing: when superhydrophobicity stimulates an extreme freezing delay.

    PubMed

    Boinovich, Ludmila; Emelyanenko, Alexandre M; Korolev, Vadim V; Pashinin, Andrei S

    2014-02-18

    An increasing number of studies directed at supercooling water droplets on surfaces with different wettabilities have appeared in recent years. This activity has been stimulated by the recognition that water supercooling phenomena can be effectively used to develop methods for protecting outdoor equipment and infrastructure elements against icing and snow accretion. In this article, we discuss the nucleation kinetics of supercooled sessile water droplets on hydrophilic, hydrophobic, and superhydrophobic surfaces under isothermal conditions at temperatures of -8, -10, and -15 °C and a saturated water vapor atmosphere. The statistics of nucleation events for the ensembles of freezing sessile droplets is completed by the detailed analysis of the contact angle temperature dependence and freezing of individual droplets in a saturated vapor atmosphere. We have demonstrated that the most essential freezing delay is characteristic of the superhydrophobic coating on aluminum, with the texture resistant to contact with ice and water. This delay can reach many hours at T = -8 °C and a few minutes at -23 °C. The observed behavior is analyzed on the basis of different nucleation mechanisms. The dissimilarity in the total nucleation rate, detected for two superhydrophobic substrates having the same apparent contact angle of the water drop but different resistivities of surface texture to the contact with water/ice, is associated with the contribution of heterogeneous nucleation on external centers located at the water droplet/air interface. PMID:24491217

  3. Studies on Freezing RAM Semen in Absence of Glycerol.

    NASA Astrophysics Data System (ADS)

    Abdelnaby, Abdelhady Abdelhakeam

    1988-12-01

    Glycerol is widely used as a major cryoprotective agent for freezing spermatozoa of almost all species. However, it reduces fertility of sheep inseminated cervically compared with intrauterine insemination. Studies were conducted to develop a method and procedure for freezing ram semen in the absence of glycerol. Post -thaw survival of ram spermatozoa frozen in the absence of glycerol was affected by time and temperature after collection and before dilution and time after dilution and before freezing. Increase in time at 5^ circC before or after dilution and before freezing increased both post-thaw motility and number of cells passing through Sephadex filter. A cold dilution method was developed. Slow cooling of fresh ram semen and diluting at 5^circ C 2-3 hr. after collection, then freezing 1 hr. after dilution improved both post-thaw motility and number of cells passing through Sephadex filter compared with immediate dilution at 30-37^circC after collection and freezing 3-4 hr. later (P < 0.05). An extender was developed to freeze ram semen in the absence of glycerol. An increase in post-thaw motility was obtained when semen was extended in TES titrated with Tris to pH 7.0 (TEST) and osmotic pressure of 375-400 mOsm/kg, containing 25-30% (v/v) egg yolk and 10% (v/v) maltose. A special device (boat) for freezing was constructed to insure the same height of the sample above LN _2 and thus the same freezing rate from freeze to freeze. Freezing of semen in 0.25cc straws at 5-10 cm above LN_2 (73.8 to 49.5 ^circC/min) yielded higher post-thaw motility than the rates resulted from freezing at 15 cm above LN_2 or 1 cm above LN _2. Faster Thawing in 37^ circC water for 30 sec. (7.8^ circC/sec.) increased post-thaw motility compared with slower thawing in 5 or 20^circ C water (P < 0.05). A lambing rate of 52.2% was obtained in one fertility trial conducted with ram semen frozen without glycerol and 17.1% in a second trial. One injection (IM) of 15 mg PGF_{2alpha}/ewe for estrus synchronization during breeding season resulted in higher heat response and lambing rate than two injections given 10 days apart.

  4. Florida harvester ant nest architecture, nest relocation and soil carbon dioxide gradients.

    PubMed

    Tschinkel, Walter R

    2013-01-01

    Colonies of the Florida harvester ant, Pogonomyrmex badius, excavate species-typical subterranean nests up the 3 m deep with characteristic vertical distribution of chamber area/shape, spacing between levels and vertical arrangement of the ants by age and brood stage. Colonies excavate and occupy a new nest about once a year, and doing so requires that they have information about the depth below ground. Careful excavation and mapping of vacated and new nests revealed that there was no significant difference between the old and new nests in any measure of nest size, shape or arrangement. Colonies essentially built a replicate of the just-vacated nest (although details differed), and they did so in less than a week. The reason for nest relocation is not apparent. Tschinkel noted that the vertical distribution of chamber area, worker age and brood type was strongly correlated to the soil carbon dioxide gradient, and proposed that this gradient serves as a template for nest excavation and vertical distribution. To test this hypothesis, the carbon dioxide gradient of colonies that were just beginning to excavate a new nest was eliminated by boring 6 vent holes around the forming nest, allowing the soil CO2 to diffuse into the atmosphere and eliminating the gradient. Sadly, neither the nest architecture nor the vertical ant distribution of vented nests differed from either unvented control or from their own vacated nest. In a stronger test, workers excavated a new nest under a reversed carbon dioxide gradient (high concentration near the surface, low below). Even under these conditions, the new and old nests did not differ significantly, showing that the soil carbon dioxide gradient does not serve as a template for nest construction or vertical worker distribution. The possible importance of soil CO2 gradients for soil-dwelling animals is discussed. PMID:23555829

  5. Florida Harvester Ant Nest Architecture, Nest Relocation and Soil Carbon Dioxide Gradients

    PubMed Central

    Tschinkel, Walter R.

    2013-01-01

    Colonies of the Florida harvester ant, Pogonomyrmex badius, excavate species-typical subterranean nests up the 3 m deep with characteristic vertical distribution of chamber area/shape, spacing between levels and vertical arrangement of the ants by age and brood stage. Colonies excavate and occupy a new nest about once a year, and doing so requires that they have information about the depth below ground. Careful excavation and mapping of vacated and new nests revealed that there was no significant difference between the old and new nests in any measure of nest size, shape or arrangement. Colonies essentially built a replicate of the just-vacated nest (although details differed), and they did so in less than a week. The reason for nest relocation is not apparent. Tschinkel noted that the vertical distribution of chamber area, worker age and brood type was strongly correlated to the soil carbon dioxide gradient, and proposed that this gradient serves as a template for nest excavation and vertical distribution. To test this hypothesis, the carbon dioxide gradient of colonies that were just beginning to excavate a new nest was eliminated by boring 6 vent holes around the forming nest, allowing the soil CO2 to diffuse into the atmosphere and eliminating the gradient. Sadly, neither the nest architecture nor the vertical ant distribution of vented nests differed from either unvented control or from their own vacated nest. In a stronger test, workers excavated a new nest under a reversed carbon dioxide gradient (high concentration near the surface, low below). Even under these conditions, the new and old nests did not differ significantly, showing that the soil carbon dioxide gradient does not serve as a template for nest construction or vertical worker distribution. The possible importance of soil CO2 gradients for soil-dwelling animals is discussed. PMID:23555829

  6. Vertical ionospheric sounding measurements

    Microsoft Academic Search

    W. F. Utlaut; T. N. Gautier

    1964-01-01

    This report presents data on the ionospheric perturbations resulting from the five 1962 high-altitude nuclear detonations, Star Fish, Check Mate, Blue Gill, King Fish, and Tight Rope, as obtained with sweep-frequency vertical-incidence ionosondes operated at the Islands of Maui, Tern (French Frigate Shoals), Midway, Wake (Star Fish only), Canton, Tutuila (American Samoa), and Tongatapu. The ionosondes at Midway and Tongataupu

  7. Cold-Induced Freezing Tolerance in Arabidopsis1

    PubMed Central

    Wanner, Leslie A.; Junttila, Olavi

    1999-01-01

    Changes in the physiology of plant leaves are correlated with enhanced freezing tolerance and include accumulation of compatible solutes, changes in membrane composition and behavior, and altered gene expression. Some of these changes are required for enhanced freezing tolerance, whereas others are merely consequences of low temperature. In this study we demonstrated that a combination of cold and light is required for enhanced freezing tolerance in Arabidopsis leaves, and this combination is associated with the accumulation of soluble sugars and proline. Sugar accumulation was evident within 2 h after a shift to low temperature, which preceded measured changes in freezing tolerance. In contrast, significant freezing tolerance was attained before the accumulation of proline or major changes in the percentage of dry weight were detected. Many mRNAs also rapidly accumulated in response to low temperature. All of the cold-induced mRNAs that we examined accumulated at low temperature even in the absence of light, when there was no enhancement of freezing tolerance. Thus, the accumulation of these mRNAs is insufficient for cold-induced freezing tolerance. PMID:10364390

  8. Freeze-thaw durability of air-entrained concrete.

    PubMed

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

  9. Metabolic Changes in Avena sativa Crowns Recovering from Freezing

    PubMed Central

    Henson, Cynthia A.; Duke, Stanley H.; Livingston, David P.

    2014-01-01

    Extensive research has been conducted on cold acclimation and freezing tolerance of fall-sown cereal plants due to their economic importance; however, little has been reported on the biochemical changes occurring over time after the freezing conditions are replaced by conditions favorable for recovery and growth such as would occur during spring. In this study, GC-MS was used to detect metabolic changes in the overwintering crown tissue of oat (Avena sativa L.) during a fourteen day time-course after freezing. Metabolomic analysis revealed increases in most amino acids, particularly proline, 5-oxoproline and arginine, which increased greatly in crowns that were frozen compared to controls and correlated very significantly with days after freezing. In contrast, sugar and sugar related metabolites were little changed by freezing, except sucrose and fructose which decreased dramatically. In frozen tissue all TCA cycle metabolites, especially citrate and malate, decreased in relation to unfrozen tissue. Alterations in some amino acid pools after freezing were similar to those observed in cold acclimation whereas most changes in sugar pools after freezing were not. These similarities and differences suggest that there are common as well as unique genetic mechanisms between these two environmental conditions that are crucial to the winter survival of plants. PMID:24675792

  10. Freeze-Thaw Durability of Air-Entrained Concrete

    PubMed Central

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

  11. Levodopa changes the severity of freezing in Parkinson's disease.

    PubMed

    Fietzek, Urban M; Zwosta, Jens; Schroeteler, Frauke E; Ziegler, Kerstin; Ceballos-Baumann, Andres O

    2013-10-01

    Oral levodopa has been proposed to be one of the more effective medications to alleviate freezing of gait, but there is limited data on its efficacy. We evaluated the gait phenomenology of 20 Parkinson's disease patients with freezing of gait before and 60 min after a standardized levodopa dose using a rating scale based on the assumption that festination and akinetic freezing share a common pathophysiology. Levodopa abolished festination and freezing in 20% of patients (p < 0.0001), and reduced the freezing sum score from a median of 15 (IQR 6.75-27.5) to 3.5 (1-11.25), p < 0.001) in all but one of the remainder. Pre-dose ratings correlated with post-dose ratings, in that those patients with lower pre-dose item-scores also showed lower post-dose outcome scores. Levodopa's effect on both festination and akinetic freezing was linear, thereby supporting the concept that festination and freezing are variants on a continuity of episodic gait disorders in PD. PMID:23642712

  12. Convection in Drying and Freezing Ground

    E-print Network

    Faizal, Mir

    2012-01-01

    In this paper we analyse the drying of a soil composed of particles, water and solute impurities, and study the occurrence of convective instabilities during evaporation. We find that the main driving force for instability is the formation of a concentration gradient at the soil surface due to the evaporation of water. A similar phenomenon may occur during the thawing of frozen ground in Arctic regions.

  13. Convection in drying and freezing ground

    NASA Astrophysics Data System (ADS)

    Faizal, Mir; Peppin, Stephen

    2015-06-01

    In this paper, we analyse the drying of a soil composed of particles, water and solute impurities, and study the occurrence of convective instabilities during evaporation. We find that the main driving force for instability is the formation of a concentration gradient at the soil surface due to the evaporation of water. A similar phenomenon may occur during the thawing of frozen ground in Arctic regions.

  14. Mutagenic effect of freezing on nuclear DNA of Saccharomyces cerevisiae.

    PubMed

    Todorova, T; Pesheva, M; Stamenova, R; Dimitrov, M; Venkov, P

    2012-05-01

    Although fragmentation of DNA has been observed in cells undergoing freezing procedures, a mutagenic effect of sub-zero temperature treatment has not been proved by induction and isolation of mutants in nuclear DNA (nDNA). In this communication we supply evidence for mutagenicity of freezing on nDNA of Saccharomyces cerevisiae cells. In the absence of cryoprotectors, cooling for 2 h at +4°C and freezing for 1 h at -10°C and 16 h at -20°C, with a cooling rate of 3°C/min, resulted in induction of frame-shift and reverse mutations in microsatellite and coding regions of nDNA. The sub-zero temperature exposure also has a strong recombinogenic effect, evidenced by induction of gene-conversion and crossing-over events. Freezing induces mutations and enhances recombination with a frequency equal to or higher than that of methylmethanesulphonate at comparable survival rates. The signals for the appearance of nDNA lesions induced by freezing are detected and transduced by the DNA damage pathway. Extracellular cryoprotectors did not prevent the mutagenic effect of freezing, while accumulation of trehalose inside cells reduced nDNA cryodamage. Freezing of cells is accompanied by generation of high ROS levels, and the oxidative stress raised during the freeze-thaw process is the most likely reason for the DNA damaging effect. Experiments with mitochondrial rho? mutants or scavengers of ROS indicated that mutagenic and recombinogenic effects of sub-zero temperatures can be decreased but not eliminated by reduction of ROS level. The complete protection against cryodamage in nDNA required simultaneous usage of intracellular cryoprotector and ROS scavenger during the freeze-thaw process. PMID:22576810

  15. Predicting global overturning from meridional density gradients

    NASA Astrophysics Data System (ADS)

    Butler, Edward; Oliver, Kevin; Hirschi, Joel

    2015-04-01

    Numerous attempts have been made to scale the strength of the meridional overturning circulation (MOC), principally in the North Atlantic, with large-scale, basin-wide hydrographic properties. In particular, various approaches to scaling the MOC with meridional density gradients have been proposed, but the success of these has only been demonstrated under limited conditions. Here we present a scaling relationship linking overturning to twice vertically-integrated meridional density gradients via the hydrostatic equation and a "rotated" form of the geostrophic equation. This provides a meridional overturning streamfunction as a function of depth for each basin. Using a series of periodically forced experiments in a global, coarse resolution configuration of the general circulation model NEMO, we explore the timescales over which this scaling is temporally valid. We find that the scaling holds well in the upper Atlantic cell (at 1000m) on decadal and longer timescales, explaining at least 94% of overturning variance for timescales of 128 to 2048 years and accurately predicting the relative magnitude of the response for different frequencies. Despite the highly nonlinear response of the Antarctic cell in the abyssal Atlantic, over 77% of the observed variability at 4000m is predicted on timescales of 32 years and longer. The scaling law is also successful in the Indo-Pacific, thus demonstrating its generality. This analysis is extended to a higher resolution, stochastically forced simulation for which correlations of at least 0.79 are obtained with upper Atlantic MOC variance on all timescales greater than 25 years. These results demonstrate that meridional density gradients and overturning are linked via meridional pressure gradients, and that both the strength and structure of the MOC can be predicted from hydrography on multi-decadal and longer timescales provided that the link is made in this way.

  16. Air-Cooled Stack Freeze Tolerance Freeze Failure Modes and Freeze Tolerance Strategies for GenDriveTM Material Handling Application Systems and Stacks Final Scientific Report

    SciTech Connect

    Hancock, David, W.

    2012-02-14

    Air-cooled stack technology offers the potential for a simpler system architecture (versus liquid-cooled) for applications below 4 kilowatts. The combined cooling and cathode air allows for a reduction in part count and hence a lower cost solution. However, efficient heat rejection challenges escalate as power and ambient temperature increase. For applications in ambient temperatures below freezing, the air-cooled approach has additional challenges associated with not overcooling the fuel cell stack. The focus of this project was freeze tolerance while maintaining all other stack and system requirements. Through this project, Plug Power advanced the state of the art in technology for air-cooled PEM fuel cell stacks and related GenDrive material handling application fuel cell systems. This was accomplished through a collaborative work plan to improve freeze tolerance and mitigate freeze-thaw effect failure modes within innovative material handling equipment fuel cell systems designed for use in freezer forklift applications. Freeze tolerance remains an area where additional research and understanding can help fuel cells to become commercially viable. This project evaluated both stack level and system level solutions to improve fuel cell stack freeze tolerance. At this time, the most cost effective solutions are at the system level. The freeze mitigation strategies developed over the course of this project could be used to drive fuel cell commercialization. The fuel cell system studied in this project was Plug Power's commercially available GenDrive platform providing battery replacement for equipment in the material handling industry. The fuel cell stacks were Ballard's commercially available FCvelocity 9SSL (9SSL) liquid-cooled PEM fuel cell stack and FCvelocity 1020ACS (Mk1020) air-cooled PEM fuel cell stack.

  17. Sperm surface changes during the acrosome reaction as observed by freeze-fracture.

    PubMed

    Fléchon, J E

    1985-11-01

    The mammalian acrosome reaction is an exocytotic process that can be analyzed by the technique of freeze-fracture; only sperm cells capacitated in vitro or treated to elicit the acrosome reaction in vitro have been studied, and all pictures published are from material fixed before freezing. All the authors point out the appearance of particle-free areas in the plasma membrane of the acrosomal region during capacitation and before any fusion. This is interpreted as an increase in membrane fluidity as suggested by studies on membrane lipid composition in guinea-pig sperm. We have recently described the induced acrosome reaction in ram spermatozoa. Fusion starts at the limit of the anterior and equatorial segments and progresses forward in the anterior segment along ramified paths, resulting in a fenestration gradient of the acrosomal cap. Fusion propagation may be controlled by fluidity increase in the plasma membrane of the anterior segment, and it is probably inhibited in the equatorial segment by the ordered structure of the acrosomal membrane. PMID:4072941

  18. Effect of local filtering on freezing phenomena of quantum correlation

    NASA Astrophysics Data System (ADS)

    Karmakar, Sumana; Sen, Ajoy; Bhar, Amit; Sarkar, Debasis

    2015-05-01

    General quantum correlation measures such as quantum discord, one-norm geometric quantum discord exhibit freezing, sudden change, and double sudden change behavior in their decay rates under different noisy channels. Therefore, one may attempt to investigate how the freezing behavior and other dynamical features are affected under application of local quantum operations. In this work, we demonstrate the effect of local filtering on the dynamical evolution of quantum correlations. We have found that using local filtering, one may remove freezing depending upon the filtering parameter.

  19. Effect of local filtering on freezing phenomena of quantum correlation

    NASA Astrophysics Data System (ADS)

    Karmakar, Sumana; Sen, Ajoy; Bhar, Amit; Sarkar, Debasis

    2015-07-01

    General quantum correlation measures such as quantum discord, one-norm geometric quantum discord exhibit freezing, sudden change, and double sudden change behavior in their decay rates under different noisy channels. Therefore, one may attempt to investigate how the freezing behavior and other dynamical features are affected under application of local quantum operations. In this work, we demonstrate the effect of local filtering on the dynamical evolution of quantum correlations. We have found that using local filtering, one may remove freezing depending upon the filtering parameter.

  20. Freeze-out volume of hot dense fireball

    E-print Network

    M. Mishra; C. P. Singh

    2007-09-27

    A thermodynamically consistent excluded volume model is proposed to account for the particle multiplicities obtained from lowest SIS energies to the highest RHIC energies. The chemical freeze-out volumes lying in a slice of one unit of rapidity for pions and kaons are separately inferred from this analysis and the results are compared with the corresponding thermal freeze-out volumes obtained from the Hanbury-Brown Twiss (HBT) pion interferometry. Furthermore, we extract the variations of freeze-out number densities for pions and nucleons with the center-of-mass energy in our model and compare them with the HBT data.

  1. Heat Transfer Control in Quiescent Air with Thermal Gradient by Magnetizing Force Under both Gravitational and Nongravitational Fields

    Microsoft Academic Search

    Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe

    2005-01-01

    Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force on quiescent air with thermal gradient in a vertical cylindrical container under both gravitational and nongravitational fields. Several sizes and axial positions of a circular electric coil were tested so that the magnetizing force depended on the magnetic gradient. Under both gravitational and nongravitational fields, the convection

  2. 3-D radial gravity gradient inversion

    NASA Astrophysics Data System (ADS)

    Oliveira, Vanderlei C.; Barbosa, Valéria C. F.

    2013-11-01

    We have presented a joint inversion of all gravity-gradient tensor components to estimate the shape of an isolated 3-D geological body located in subsurface. The method assumes the knowledge about the depth to the top and density contrast of the source. The geological body is approximated by an interpretation model formed by an ensemble of vertically juxtaposed 3-D right prisms, each one with known thickness and density contrast. All prisms forming the interpretation model have a polygonal horizontal cross-section that approximates a depth slice of the body. Each polygon defining a horizontal cross-section has the same fixed number of vertices, which are equally spaced from 0° to 360° and have their horizontal locations described in polar coordinates referred to an arbitrary origin inside the polygon. Although the number of vertices forming each polygon is known, the horizontal coordinates of these vertices are unknown. To retrieve a set of juxtaposed depth slices of the body, and consequently, its shape, our method estimates the radii of all vertices and the horizontal Cartesian coordinates of all arbitrary origins defining the geometry of all polygons describing the horizontal cross-sections of the prisms forming the interpretation model. To obtain a stable estimate that fits the observed data, we impose constraints on the shape of the estimated body. These constraints are imposed through the well-known zeroth- and first-order Tikhonov regularizations allowing, for example, the estimate of vertical or dipping bodies. If the data do not have enough in-depth resolution, the proposed inverse method can obtain a set of stable estimates fitting the observed data with different maximum depths. To analyse the data resolution and deal with this possible ambiguity, we plot the ?2-norm of the residuals (s) against the estimated volume (vp) produced by a set of estimated sources having different maximum depths. If this s × vp curve (s as a function of vp) shows a well-defined minimum of s, the data have enough resolution to recover the shape of the body entirely. Conversely, if the observed data do not have enough resolution, some estimates with different maximum depths produce practically the same minimum value of s on the s × vp curve. In this case, the best estimate among a suite of estimates producing equally data fits is the one fitting the gravity-gradient data and producing the minima of both the source's bottom depth and volume. The histograms of the residuals can be used to quantify and remove systematic errors in the data. After removing these errors, we confirmed the ability of our method to recover the source geometry entirely (or its upper part only), if the data have sufficient (or insufficient) in-depth resolution. By inverting the gravity-gradient data from a survey over the Vinton salt dome (Louisiana, USA) with a density contrast of 0.55 g cm-3, we estimated a massive cap rock whose maximum depth attains 460 ± 10 m and its shallowest portion is elongated in the northeast-southwest direction.

  3. Surfactant-induced gradients in the three-dimensional Belousov-Zhabotinsky reaction

    NASA Astrophysics Data System (ADS)

    Kupitz, Dennis; Alonso, Sergio; Bär, Markus; Hauser, Marcus J. B.

    2011-11-01

    Scroll waves are prominent patterns formed in three-dimensional excitable media, and they are frequently considered highly relevant for some types of cardiac arrhythmias. Experimentally, scroll wave dynamics is often studied by optical tomography in the Belousov-Zhabotinsky reaction, which produces CO2 as an undesired product. Addition of small concentrations of a surfactant to the reaction medium is a popular method to suppress or retard CO2 bubble formation. We show that in closed reactors even these low concentrations of surfactants are sufficient to generate vertical gradients of excitability which are due to gradients in CO2 concentration. In reactors open to the atmosphere such gradients can be avoided. The gradients induce a twist on vertically oriented scroll waves, while a twist is absent in scroll waves in a gradient-free medium. The effects of the CO2 gradients are reproduced by a numerical study, where we extend the Oregonator model to account for the production of CO2 and for its advection against the direction of gravity. The numerical simulations confirm the role of solubilized CO2 as the source of the vertical gradient of excitability in reactors closed to the atmosphere.

  4. Inner ear tissue preservation by rapid freezing: improving fixation by high-pressure freezing and hybrid methods.

    PubMed

    Bullen, A; Taylor, R R; Kachar, B; Moores, C; Fleck, R A; Forge, A

    2014-09-01

    In the preservation of tissues in as 'close to life' state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 ?m) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. PMID:25016142

  5. Inner ear tissue preservation by rapid freezing: Improving fixation by high-pressure freezing and hybrid methods

    PubMed Central

    Bullen, A.; Taylor, R.R.; Kachar, B.; Moores, C.; Fleck, R.A.; Forge, A.

    2014-01-01

    In the preservation of tissues in as ‘close to life’ state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 ?m) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. PMID:25016142

  6. Red blood cell preservation by droplet freezing with polyvinyl pyrrolidone or sucrose/dextrose and by bulk freezing with glycerol

    PubMed Central

    Schmid, Pirmin; Huvard, Michael J.; Lee-Stroka, A. Hallie; Lee, Jae Y.; Byrne, Karen M.; Flegel, Willy A.

    2012-01-01

    Background Red blood cell (RBC) preservation is essential to transfusion medicine. Many blood group reference laboratories need a method to preserve rare blood samples for serologic testing at a later date. This study offers a comparison of three common cryoprotective agents and protocols used today: bulk preservation with glycerol and droplet freezing with sucrose/dextrose (S+D) or polyvinyl pyrrolidone (PVP). Study design and methods Human blood from 14 volunteers was collected and frozen at set intervals over two weeks with PVP, S+D, or glycerol. The frozen RBCs were later thawed and the percentage of surviving RBCs was determined. Detailed protocols and an instructional video are supplied. Results Over a two week period, RBCs preserved with glycerol and thawed with a widely used protocol showed a recovery of 41 ± 16 % (mean ± standard deviation) while those thawed with a modified glycerol protocol showed a recovery of 76 ± 8 %. RBCs preserved by droplet freezing with S+D showed a recovery of 56 ± 11 % while those preserved by droplet freezing with PVP showed a recovery of 85 ± 6 %. Recovery values were similar with ethylenediaminetetraacetic acid (EDTA) or heparin anticoagulants, differing freezing rates, and varying droplet volumes. Conclusion Droplet freezing with PVP offered the greatest recovery. While bulk freezing with glycerol can be effective too, droplet freezing may be a more convenient method overall. It requires less effort to thaw, needs much less storage room, and allows blood group laboratories to be frugal with thawing rare samples. PMID:21790629

  7. Tight junction regulates epidermal calcium ion gradient and differentiation

    SciTech Connect

    Kurasawa, Masumi; Maeda, Tetsuo; Oba, Ai; Yamamoto, Takuya [Pola Chemical Industries Inc., 560 Kashio-cho, Totsuka-ku, Yokohama 244-0812 (Japan)] [Pola Chemical Industries Inc., 560 Kashio-cho, Totsuka-ku, Yokohama 244-0812 (Japan); Sasaki, Hiroyuki, E-mail: sasakih@jikei.ac.jp [Division of Fine Morphology, Core Research Facilities, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461 (Japan) [Division of Fine Morphology, Core Research Facilities, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461 (Japan); The Center for Advanced Medical Engineering and Infomatics, Osaka University, Osaka 565-0871 (Japan)

    2011-03-25

    Research highlights: {yields} We disrupted epidermal tight junction barrier in reconstructed epidermis. {yields} It altered Ca{sup 2+} distribution and consequentially differentiation state as well. {yields} Tight junction should affect epidermal homeostasis by maintaining Ca{sup 2+} gradient. -- Abstract: It is well known that calcium ions (Ca{sup 2+}) induce keratinocyte differentiation. Ca{sup 2+} distributes to form a vertical gradient that peaks at the stratum granulosum. It is thought that the stratum corneum (SC) forms the Ca{sup 2+} gradient since it is considered the only permeability barrier in the skin. However, the epidermal tight junction (TJ) in the granulosum has recently been suggested to restrict molecular movement to assist the SC as a secondary barrier. The objective of this study was to clarify the contribution of the TJ to Ca{sup 2+} gradient and epidermal differentiation in reconstructed human epidermis. When the epidermal TJ barrier was disrupted by sodium caprate treatment, Ca{sup 2+} flux increased and the gradient changed in ion-capture cytochemistry images. Alterations of ultrastructures and proliferation/differentiation markers revealed that both hyperproliferation and precocious differentiation occurred regionally in the epidermis. These results suggest that the TJ plays a crucial role in maintaining epidermal homeostasis by controlling the Ca{sup 2+} gradient.

  8. Rectilinear migration of a drop in a nonlinear thermal gradient

    SciTech Connect

    Sharma, K.R.

    1999-07-01

    The studies hitherto on thermocapillary migration of isolated drops/bubble in a vertical temperature gradient are for the case of linear temperature gradient when the experimental apparatus reaches steady state. The purpose of this study is to quantitate the effect of nonlinear temperature gradient that affects the thermocapillary stress among other things. A good example of this is during the unsteady thermocapillary migration of an isolated immiscible drop that slowly migrates subject to an impulsive interfacial temperature gradient. All other physical properties such as viscosity, heat capacity, density, and thermal conductivity are assumed invariant with temperature and the interfacial tension varies linearly with temperature for the fluid such as silicone oil. The problem requires a numerical solution. The solution was obtained using fourth order Rung Kutta method. The solution was bonded by the asymptotic solutions at short distances and large distances. This analysis can be extended for the periodic temperature profile maintained at the warm pole at sustained state when the thermocapillary motion in microgravity limits is expected to exhibit the yo yo or quasi periodic structure. The findings are applicable to materials that exhibit a nonlinear interfacial tension gradient with temperature and can be studied in the steady state limit of the temperature gradient. The ongoing study is to include the viscosity variation with temperature of the continuous fluid.

  9. Vertical Motion Simulator

    NSDL National Science Digital Library

    The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.

  10. Adaptation to seasonality and the winter freeze

    PubMed Central

    Preston, Jill C.; Sandve, Simen R.

    2013-01-01

    Flowering plants initially diversified during the Mesozoic era at least 140 million years ago in regions of the world where temperate seasonal environments were not encountered. Since then several cooling events resulted in the contraction of warm and wet environments and the establishment of novel temperate zones in both hemispheres. In response, less than half of modern angiosperm families have members that evolved specific adaptations to cold seasonal climates, including cold acclimation, freezing tolerance, endodormancy, and vernalization responsiveness. Despite compelling evidence for multiple independent origins, the level of genetic constraint on the evolution of adaptations to seasonal cold is not well understood. However, the recent increase in molecular genetic studies examining the response of model and crop species to seasonal cold offers new insight into the evolutionary lability of these traits. This insight has major implications for our understanding of complex trait evolution, and the potential role of local adaptation in response to past and future climate change. In this review, we discuss the biochemical, morphological, and developmental basis of adaptations to seasonal cold, and synthesize recent literature on the genetic basis of these traits in a phylogenomic context. We find evidence for multiple genetic links between distinct physiological responses to cold, possibly reinforcing the coordinated expression of these traits. Furthermore, repeated recruitment of the same or similar ancestral pathways suggests that land plants might be somewhat pre-adapted to dealing with temperature stress, perhaps making inducible cold traits relatively easy to evolve. PMID:23761798

  11. Hot water can freeze faster than cold?!?

    E-print Network

    Monwhea Jeng

    2005-12-29

    We review the Mpemba effect, where intially hot water freezes faster than initially cold water. While the effect appears impossible at first sight, it has been seen in numerous experiments, was reported on by Aristotle, Francis Bacon, and Descartes, and has been well-known as folklore around the world. It has a rich and fascinating history, which culminates in the dramatic story of the secondary school student, Erasto Mpemba, who reintroduced the effect to the twentieth century scientific community. The phenomenon, while simple to describe, is deceptively complex, and illustrates numerous important issues about the scientific method: the role of skepticism in scientific inquiry, the influence of theory on experiment and observation, the need for precision in the statement of a scientific hypothesis, and the nature of falsifiability. We survey proposed theoretical mechanisms for the Mpemba effect, and the results of modern experiments on the phenomenon. Studies of the observation that hot water pipes are more likely to burst than cold water pipes are also described.

  12. Drying a tuberculosis vaccine without freezing.

    PubMed

    Wong, Yun-Ling; Sampson, Samantha; Germishuizen, Willem Andreas; Goonesekera, Sunali; Caponetti, Giovanni; Sadoff, Jerry; Bloom, Barry R; Edwards, David

    2007-02-20

    With the increasing incidence of tuberculosis and drug resistant disease in developing countries due to HIV/AIDS, there is a need for vaccines that are more effective than the present bacillus Calmette-Guérin (BCG) vaccine. We demonstrate that BCG vaccine can be dried without traditional freezing and maintained with remarkable refrigerated and room-temperature stability for months through spray drying. Studies with a model Mycobacterium (Mycobacterium smegmatis) revealed that by removing salts and cryoprotectant (e.g., glycerol) from bacterial suspensions, the significant osmotic pressures that are normally produced on bacterial membranes through droplet drying can be reduced sufficiently to minimize loss of viability on drying by up to 2 orders of magnitude. By placing the bacteria in a matrix of leucine, high-yield, free-flowing, "vial-fillable" powders of bacteria (including M. smegmatis and M. bovis BCG) can be produced. These powders show relatively minor losses of activity after maintenance at 4 degrees C and 25 degrees C up to and beyond 4 months. Comparisons with lyophilized material prepared both with the same formulation and with a commercial formulation reveal that the spray-dried BCG has better overall viability on drying. PMID:17299039

  13. GPR utilization in artificial freezing engineering

    NASA Astrophysics Data System (ADS)

    Song, Lei; Yang, Weihao; Huang, Jiahui; Li, Haipeng; Zhang, Xiaojun

    2013-06-01

    To utilize ground penetrating radar (GPR) in artificial freezing engineering (AFE), the electromagnetic parameters (EMP) of frozen soil were measured using a vector network analyser, which showed that the dielectric permittivity and electric conductivity change abruptly at the boundary between the frozen and the non-frozen soil. Then similarity criteria of GPR model experiments were deduced, and GPR laboratory model experiments and field explorations of AFE were carried out. It was found that for AFE, the GPR travel time and profile characters of anomalies in model experiments were similar to those in field explorations, while the amplitude of GPR signals in laboratory model experiments were much stronger than those in field explorations. Numerical simulations were also implemented to analyse the relationship between model experiments and field explorations, which further told us why we could easily find the targets by GPR in the laboratory but not in field explorations. The outputs showed that GPR could be used to detect the thickness of the frozen wall and to find unfrozen soil defects, even though the amplitude of the reflective signals were much weaker than those of laboratory experiments. The research findings have an important theoretical value for AFE and permafrost region engineering, and the deduced GPR similarity criteria could be widely used in other GPR model experiments.

  14. Freezing and Decorated Poisson Point Processes

    NASA Astrophysics Data System (ADS)

    Subag, Eliran; Zeitouni, Ofer

    2015-07-01

    The limiting extremal processes of the branching Brownian motion (BBM), the two-speed BBM, and the branching random walk are known to be randomly shifted decorated Poisson point processes (SDPPP). In the proofs of those results, the Laplace functional of the limiting extremal process is shown to satisfy for any nonzero, nonnegative, compactly supported, continuous function f, where is the shift operator, is a real number that depends on f, and g is a real function that is independent of f. We show that, under some assumptions, this property characterizes the structure of SDPPP. Moreover, when it holds, we show that g has to be a convolution of the Gumbel distribution with some measure. The above property of the Laplace functional is closely related to a `freezing phenomenon' that is expected to occur in a wide class of log-correlated fields, and which has played an important role in the analysis of various models. Our results shed light on this intriguing phenomenon and provide a natural tool for proving an SDPPP structure in these and other models.

  15. Adaptation to seasonality and the winter freeze.

    PubMed

    Preston, Jill C; Sandve, Simen R

    2013-01-01

    Flowering plants initially diversified during the Mesozoic era at least 140 million years ago in regions of the world where temperate seasonal environments were not encountered. Since then several cooling events resulted in the contraction of warm and wet environments and the establishment of novel temperate zones in both hemispheres. In response, less than half of modern angiosperm families have members that evolved specific adaptations to cold seasonal climates, including cold acclimation, freezing tolerance, endodormancy, and vernalization responsiveness. Despite compelling evidence for multiple independent origins, the level of genetic constraint on the evolution of adaptations to seasonal cold is not well understood. However, the recent increase in molecular genetic studies examining the response of model and crop species to seasonal cold offers new insight into the evolutionary lability of these traits. This insight has major implications for our understanding of complex trait evolution, and the potential role of local adaptation in response to past and future climate change. In this review, we discuss the biochemical, morphological, and developmental basis of adaptations to seasonal cold, and synthesize recent literature on the genetic basis of these traits in a phylogenomic context. We find evidence for multiple genetic links between distinct physiological responses to cold, possibly reinforcing the coordinated expression of these traits. Furthermore, repeated recruitment of the same or similar ancestral pathways suggests that land plants might be somewhat pre-adapted to dealing with temperature stress, perhaps making inducible cold traits relatively easy to evolve. PMID:23761798

  16. Satellite freeze forecast system: Executive summary

    NASA Technical Reports Server (NTRS)

    Martsolf, J. D. (principal investigator)

    1983-01-01

    A satellite-based temperature monitoring and prediction system consisting of a computer controlled acquisition, processing, and display system and the ten automated weather stations called by that computer was developed and transferred to the national weather service. This satellite freeze forecasting system (SFFS) acquires satellite data from either one of two sources, surface data from 10 sites, displays the observed data in the form of color-coded thermal maps and in tables of automated weather station temperatures, computes predicted thermal maps when requested and displays such maps either automatically or manually, archives the data acquired, and makes comparisons with historical data. Except for the last function, SFFS handles these tasks in a highly automated fashion if the user so directs. The predicted thermal maps are the result of two models, one a physical energy budget of the soil and atmosphere interface and the other a statistical relationship between the sites at which the physical model predicts temperatures and each of the pixels of the satellite thermal map.

  17. Optoacoustic laser monitoring of cooling and freezing of tissues

    SciTech Connect

    Larin, Kirill V; Larina, I V; Motamedi, M; Esenaliev, R O [University of Texas, Medical Branch, Galveston, TX (United States)

    2002-11-30

    Real-time monitoring of cooling and freezing of tissues, cells, and other biological objects with a high spatial and time resolution, which is necessary for selective destruction of cancer and benign tumours during cryotherapy, as well as for preventing any damage to the structure and functioning of biological objects in cryobiology, is considered. The optoacoustic method, based on the measurement and analysis of acoustic waves induced by short laser pulses, is proposed for monitoring the cooling and freezing of the tissue. The effect of cooling and freezing on the amplitude and time profile of acoustic signals generated in real tissues and in a model object is studied. The experimental results indicate that the optoacoustic laser technique can be used for real-time monitoring of cooling and freezing of biological objects with a submillimeter spatial resolution and a high contrast. (laser biology and medicine)

  18. Hydraulic conductivity of geosynthetic clay liners after freeze-thaw

    SciTech Connect

    Hewitt, R.D. [Haley and Aldrich, Inc., Cambridge, MA (United States); Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States)

    1997-04-01

    Hydraulic conductivity tests were performed in large tanks on intact (single panel) and overlapped samples of three geosynthetic clay liners (GCLs) that has been subjected to freeze-thaw cycles. The compressive stress applied to the GCLs (7.6--12.4 kPa) was selected to simulate final cover systems for landfills. Laboratory flexible-wall permeameter tests were also performed. With the exception of one overlapped GCL, all three GCLs withstood three freeze-thaw cycles without a significant change in hydraulic conductivity. An overlapped, geo-textile-encased, stitch-bonded GCL did undergo a 1,000-fold increase in hydraulic conductivity after one freeze-thaw cycle, but the overlapped area contained stitches, which are left off the edges of the full-sized material that is deployed in the field. In general, the tests showed that GCLs can withstand at least three freeze-thaw cycles without significant changes in hydraulic conductivity.

  19. Universality of tip singularity formation in freezing water drops.

    PubMed

    Marín, A G; Enríquez, O R; Brunet, P; Colinet, P; Snoeijer, J H

    2014-08-01

    A drop of water deposited on a cold plate freezes into an ice drop with a pointy tip. While this phenomenon clearly finds its origin in the expansion of water upon freezing, a quantitative description of the tip singularity has remained elusive. Here we demonstrate how the geometry of the freezing front, determined by heat transfer considerations, is crucial for the tip formation. We perform systematic measurements of the angles of the conical tip, and reveal the dynamics of the solidification front in a Hele-Shaw geometry. It is found that the cone angle is independent of substrate temperature and wetting angle, suggesting a universal, self-similar mechanism that does not depend on the rate of solidification. We propose a model for the freezing front and derive resulting tip angles analytically, in good agreement with the experiments. PMID:25126922

  20. Fast hadron freeze-out generator, part II: noncentral collisions

    E-print Network

    N. S. Amelin; R. Lednicky; I. P. Lokhtin; L. V. Malinina; A. M. Snigirev; Iu. A. Karpenko; Yu. M. Sinyukov; I. Arsene; L. Bravina

    2007-12-13

    The fast Monte Carlo procedure of hadron generation developed in our previous work is extended to describe noncentral collisions of nuclei. We consider different possibilities to introduce appropriate asymmetry of the freeze-out hyper-surface and flow velocity profile. For comparison with other models and experimental data we demonstrate the results based on the standard parametrizations of the hadron freeze-out hyper-surface and flow velocity profile assuming either a common chemical and thermal freeze-out or the chemically frozen evolution from chemical to thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at http://uhkm.jinr.ru/

  1. Multifidelity variance reduction for pick-freeze Sobol index estimation

    E-print Network

    Boyer, Edmond

    Multifidelity variance reduction for pick-freeze Sobol index estimation Alexandre Janon March 25 a large sample of evaluations of the output. We propose a variance reduction technique, based and context . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Variance-reduced estimator

  2. 19. FIRST FLOOR LEVEL BELOW ICE FREEZING TANKS AND LOWER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. FIRST FLOOR LEVEL BELOW ICE FREEZING TANKS AND LOWER LEVEL OF ICE DUMP AND LIFT WHERE FROZEN ICE IS BROUGHT INTO STORAGE. - Atlantic Ice & Coal Company, 135 Prince Street, Montgomery, Montgomery County, AL

  3. Condensation and freezing of droplets on superhydrophobic surfaces.

    PubMed

    Oberli, Linda; Caruso, Dean; Hall, Colin; Fabretto, Manrico; Murphy, Peter J; Evans, Drew

    2014-08-01

    Superhydrophobic coatings are reported as promising candidates for anti-icing applications. Various studies have shown that as well as having ultra water repellency the surfaces have reduced ice adhesion and can delay water freezing. However, the structure or texture (roughness) of the superhydrophobic surface is subject to degradation during the thermocycling or wetting process. This degradation can impair the superhydrophobicity and the icephobicity of those coatings. In this review, a brief overview of the process of droplet freezing on superhydrophobic coatings is presented with respect to their potential in anti-icing applications. To support this discussion, new data is presented about the condensation of water onto physically decorated substrates, and the associated freezing process which impacts on the freezing of macroscopic droplets on the surface. PMID:24200089

  4. Fuel Cells Vehicle Systems Analysis (Fuel Cell Freeze Investigation)

    SciTech Connect

    Pesaran, A.; Kim, G.; Markel, T.; Wipke, K.

    2005-05-01

    Presentation on Fuel Cells Vehicle Systems Analysis (Fuel Cell Freeze Investigation) for the 2005 Hydrogen, Fuel Cells & Infrastructure Technologies Program Annual Review held in Arlington, Virginia on May 23-26, 2005.

  5. Pharmaceutics Seminar: Excipient Phase Behavior in Freeze-Dried Systems November 1, 2012 Michael Burcusa

    E-print Network

    Thomas, David D.

    Pharmaceutics Seminar: Excipient Phase Behavior in Freeze-Dried Systems November 1, 2012 Michael, they are often formulated as freeze-dried powders [3]. During the freezing step of the lyophilization process designed for freeze-drying, the solution will contain, in addition to the API, a buffer, a lyoprotectant

  6. Mechanisms of deterioration of nutrients. [improved quality of freeze-dried foods

    NASA Technical Reports Server (NTRS)

    Karel, M.; Flink, J. M.

    1978-01-01

    Methods for improving the quality of freeze-dried foods were investigated. Areas discussed include: (1) microstructure of freeze-dried systems, (2) structural changes in freeze-dried systems, (3) artificial food matrices, and (4) osmotic preconcentration to yield improved freeze-dried products.

  7. Three keys to the radiation of angiosperms into freezing environments.

    PubMed

    Zanne, Amy E; Tank, David C; Cornwell, William K; Eastman, Jonathan M; Smith, Stephen A; FitzJohn, Richard G; McGlinn, Daniel J; O'Meara, Brian C; Moles, Angela T; Reich, Peter B; Royer, Dana L; Soltis, Douglas E; Stevens, Peter F; Westoby, Mark; Wright, Ian J; Aarssen, Lonnie; Bertin, Robert I; Calaminus, Andre; Govaerts, Rafaël; Hemmings, Frank; Leishman, Michelle R; Oleksyn, Jacek; Soltis, Pamela S; Swenson, Nathan G; Warman, Laura; Beaulieu, Jeremy M

    2014-02-01

    Early flowering plants are thought to have been woody species restricted to warm habitats. This lineage has since radiated into almost every climate, with manifold growth forms. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species' traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold. PMID:24362564

  8. Entropy production at freeze-out from dissipative fluids

    E-print Network

    E. Molnar

    2007-09-17

    Entropy production due to shear viscosity during the continuous freeze-out of a longitudinally expanding dissipative fluid is addressed. Assuming the validity of the fluid dynamical description during the continuous removal of interacting matter we estimated a small entropy production as function of the freeze-out duration and the ratio of dissipative to non-dissipative quantities in case of a relativistic massless pion fluid.

  9. Freeze concentration of dairy products Phase 2. Final report

    SciTech Connect

    Best, D.E.; Vasavada, K.C.

    1993-09-01

    An efficient, electrically driven freeze concentration system offers potential for substantially increasing electricity demand while providing the mature dairy industry with new products for domestic and export markets together with enhanced production efficiencies. Consumer tests indicate that dairy products manufactured from freeze-concentrated ingredients are either preferred or considered equivalent in quality to fresh milk-based products. Economic analyses indicate that this technology should be competitive with thermal evaporation processes on a commercial basis.

  10. Supercooling and Freezing of HNO3\\/H2O Aerosols

    Microsoft Academic Search

    Dustin Dickens

    2000-01-01

    Abstract The freezing kinetics of binary nitric acid\\/water aerosols is of fundamental,importance to the modelling of polar stratospheric clouds and the role they in ozone depletion over the Arctic\\/Antarcticregions. Cirrus clouds are also often composed of nitric acid solutions, hence an understandingof freezing process in these aerosols also aids in modelling the earth’s radiation budget and global warming. This thesis

  11. Chloroplast structure of Cyanidium caldarium shown by freeze-substitution

    Microsoft Academic Search

    Katsumi Ueda; Yukie Chida

    1987-01-01

    The freeze-substituted chloroplast in Cyanidium caldarium was observed by electron microscopy. Double envelope membranes could be clearly seen. Phycobilisomes were much better fixed by freeze-substitution than by chemical fixation. They appeared as slender cords in contrast to the disk or hemispherical shapes assumed by image subjected to chemical fixation. The arrangement of the phycobilisome-cords on the thylakoid was in a

  12. Vertical wind turbine

    SciTech Connect

    Danson, D.P.

    1988-08-16

    This patent describes a wind driven turbine of the vertical axis type comprising: (a) a support base; (b) a generally vertical column rotatably mounted to the support base; (c) upper and lower support means respectively mounted on the column for rotation therewith; wind driven blades connected between the upper and lower support means for rotation about the column and each blade being individually rotatable about a blade axis extending longitudinally through the blade to vary a blade angle of attach thereof relative to wind velocity during rotation about the column; and (e) control means for variably adjusting angles of attack of each blade to incident wind, the control means including a connecting rod means having drive means for rotating each blade about the associated blade axis in response to radial movement of the connecting rod means and control shaft pivotally mounted within the column and having a first shaft portion connected to the connecting rod means and a second shaft portion radially offset from the first shaft portion and pivotally connected to radially displace the first portion and thereby the connecting rod means to vary the blade angles of attack during rotation about the column.

  13. Energy in density gradient

    NASA Astrophysics Data System (ADS)

    Vranjes, J.; Kono, M.

    2015-01-01

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work, the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindrical configuration. This is of practical importance for drift wave instability in various plasmas, and, in particular, in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit volume (per second) in quiet regions in the corona. Consequently, within the life-time of a magnetic structure such energy losses can easily be compensated by the stochastic drift wave heating.

  14. Approaching threats elicit a freeze-like response in humans.

    PubMed

    Sagliano, Laura; Cappuccio, Angela; Trojano, Luigi; Conson, Massimiliano

    2014-02-21

    Freezing is one of the most widely recognized defensive reactions to approaching threats in animals. Here we tested whether the same stimuli can elicit freeze-like responses in healthy humans as well. We used a modified version of the two-frame apparent motion paradigm, in which both size and location of a stimulus within a background were manipulated; by these means, participants perceived the stimuli as approaching or receding. In Experiment 1, we showed that implicitly processed approaching threats (e.g., spiders or snakes) elicited a stronger freeze-like response (operationalized as slower reaction times) with respect to receding threats; freezing was significantly related to higher levels of participants' state anxiety. In Experiment 2, approaching/threatening animals were explicitly judged as more threatening than receding ones. Finally, in two further control experiments we observed that the same manipulation of stimuli's size and location, but in absence of apparent motion, did not affect freezing (Experiment 3) or explicit threat judgements (Experiment 4). The present findings demonstrated that approaching threats are critical to elicit freezing in humans, in line with animals' behaviour. PMID:24373990

  15. Freezing of barley studied by infrared video thermography.

    PubMed

    Pearce, R S; Fuller, M P

    2001-01-01

    Freezing of barley (Hordeum vulgare), Hordeum murinum, and Holcus lanatus was studied using infrared video thermography. In the field, ice could enter H. lanatus leaves through hydathodes. In laboratory tests with barley, initially 0.4% of the leaf water froze, spreading in alternate strips of high and low freezing intensity longitudinally at 1 to 4 cm s(-1), and simultaneously spreading laterally at 0.3 cm s(-1). Similar results were obtained in the field with H. lanatus. A distinct second, more intense, freezing event spread slowly from the margins of the leaves toward the midrib. Organs of uprooted barley tested in the laboratory froze in this order: nucleated leaf, roots, older leaves, younger leaves, and secondary tillers. When ice spread from one leaf to the rest of the plant the crown delayed spread to the roots and other leaves. There was a longer delay above than below -2 degrees C, helping to protect the crown from freezing during mild frosts. Initial spread of freezing was not damaging. However, the initial spread is a prerequisite for the second freezing event, which can cause damage. The route of the initial spread of ice may be extracellular, drawing water from more gel-like parts of the cell wall. PMID:11154332

  16. Review: freeze concentration technology applied to dairy products.

    PubMed

    Sánchez, J; Hernández, E; Auleda, J M; Raventós, M

    2011-02-01

    Freeze concentration is a process of concentrating liquid products by freezing the water content and subsequently removing the so-formed ice crystals from the food system. In dairy processing, this technology offers the advantage of minimizing the heat abuse of sensitive milk components, such as proteins and flavors. It thus provides an opportunity for producing dairy ingredients with enhanced functional and organoleptic qualities. By freeze concentration, skim milk has been concentrated up to 40 wt% total solids (TS) and whole milk up to 44 wt% TS. Lactose and lipids are more concentrated in the ice fraction than in the concentrated fraction. Proteins (casein and whey protein) decrease the ice growth rate and the high viscosity is a limiting factor for the freeze concentration of both skim milk and whole milk. In this study, the most important studies relating to the suspension, block and layer freeze concentration of milk are summarized, analyzing results and indicating how freeze concentration process efficiency of dairy products can be improved. PMID:21364040

  17. Freeze avoidance: a dehydrating moss gathers no ice.

    PubMed

    Lenné, Thomas; Bryant, Gary; Hocart, Charles H; Huang, Cheng X; Ball, Marilyn C

    2010-10-01

    Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ? 20% of their original volume at a nadir temperature of -20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ?-12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes. PMID:20525002

  18. Freeze concentration of dairy products, Phase 1: Final report

    SciTech Connect

    Luksas, A.; Ahmed, S.; Johnson, T.A.

    1989-03-01

    The objective of this study was to explore freeze concentration as a process to replace thermal evaporation in the dairy industry. The goals of the study were to save energy by converting concentration processes to an efficient, electrically powered, refrigeration system, and to create higher quality and innovative products that might bring new life to a nature dairy market. A small freeze concentration pilot plant was used to concentrate products for quality comparisons, for physical and chemical analytical determinations, and to discover any equipment/product attributes or limitations. Data was correlated to compare operating economics of freeze concentrations superior to the fresh feedstock in sensory and functionality tests upon reconstitution. Laboratory testing showed equal or superior quality in resulting spray dried powders from freeze concentrates. Freeze concentration was shown to be economically competitive with thermal processes and second generation freezing technology is projected to produce a substantially less expensive product and offer other advantages over current thermally produced goods. 31 figs., 14 tabs.

  19. Ultrastructural immunolocalization of polyamines in HeLa cells subjected to fast-freezing fixation and freeze substitution

    Microsoft Academic Search

    A. M. Roch; Marie Thérèse Nicolas; Gérard Quash

    1997-01-01

    Polyamines have been localized at the ultrastructural level in HeLa cells subjected first to fast-freezing fixation (FFF)-freeze\\u000a substitution (FS) and then to an immunocytochemical method combining anti-polyamine antibodies and immunogold labelling. Polyamines\\u000a were found in both the cytoplasm and the nucleus and, in the latter, particularly over the dense chromatin area. To our knowledge,\\u000a this is the first example of

  20. Drying of Fennel Plants: Oven, Freeze Drying, Effect of Freeze-Drying Time, and Use of Biopolymers

    Microsoft Academic Search

    Chryssavgi Gardeli; Vasiliki Evageliou; Christoforos Poulos; Stavrianos Yanniotis; Michael Komaitis

    2010-01-01

    Fennel plants were oven and freeze dried. The influence of freeze-drying time on the concentration of the two main components, trans-anethole and isoanethole, of its essential oil was evaluated. Drying time up to 15 h led to 50% reduction of moisture content with minor increase in volatile losses, whereas drying time greater than 15 h resulted in a dried product with an

  1. Measurement of ultralow vertical emittance using a calibrated vertical undulator

    NASA Astrophysics Data System (ADS)

    Wootton, K. P.; Boland, M. J.; Rassool, R. P.

    2014-11-01

    Very few experimental techniques are useful for the direct observation of ultralow vertical emittance in electron storage rings. In this work, quantitative measurements of ultralow (pm rad) electron beam vertical emittance using a vertical undulator are presented. An undulator radiation model was developed using the measured magnetic field of the APPLE-II type undulator. Using calibrated experimental apparatus, a geometric vertical emittance of ?y=0.9 ±0.3 pm rad has been observed. These measurements could also inform modeling of the angular distribution of undulator radiation at high harmonics, for proposed diffraction-limited storage ring light sources.

  2. Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

    SciTech Connect

    Sheridan, T. E.; Katschke, M. R.; Wells, K. D. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

    2007-02-15

    A method for measuring the time-averaged vertical electric field and its gradient in the plasma sheath using clusters with n=2 or 3 floating microspheres of known mass is described. The particle charge q is found by determining the ratio of the breathing frequency to the center-of-mass frequency for horizontal (in-plane) oscillations. The electric field at the position of the particles is then calculated using the measured charge-to-mass ratio, and the electric-field gradient is determined from the vertical resonance frequency. The Debye length is also found. Experimental results are in agreement with a simple sheath model.

  3. Simultaneous measurement of gravity acceleration and gravity gradient with an atom interferometer

    SciTech Connect

    Sorrentino, F.; Lien, Y.-H.; Rosi, G.; Tino, G. M. [Dipartimento di Fisica e Astronomia and LENS, Universita di Firenze, INFN Sezione di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (Italy); Bertoldi, A. [Laboratoire Charles Fabry de l'Institut d'Optique, CNRS and Universite Paris-Sud Campus Polytechnique, RD 128, F-91127 Palaiseau cedex (France); Bodart, Q. [Dipartimento di Fisica e Astronomia and LENS, Universita di Firenze, INFN Sezione di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (Italy); European Space Agency, Research and Scientific Support Department, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands); Cacciapuoti, L. [European Space Agency, Research and Scientific Support Department, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands); Angelis, M. de [Istituto di Fisica Applicata 'Nello Carrara' CNR, via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Prevedelli, M. [Dipartimento di Fisica dell'Universita di Bologna, Via Irnerio 46, I-40126, Bologna (Italy)

    2012-09-10

    We demonstrate a method to measure the gravitational acceleration with a dual cloud atom interferometer; the use of simultaneous atom interferometers reduces the effect of seismic noise on the gravity measurement. At the same time, the apparatus is capable of accurate measurements of the vertical gravity gradient. The ability to determine the gravity acceleration and gravity gradient simultaneously and with the same instrument opens interesting perspectives in geophysical applications.

  4. Controlled E -field gradient coils

    Microsoft Academic Search

    P. Mansfield; R. M. Bowley; B. Haywood

    2003-01-01

    Peripheral neural stimulation is a major problem in current gradient coil designs. Induced current problems in patients relate\\u000a directly to gradient strength and modulation frequency. Current designs of gradient coil tend to limit ultra-high-speed imaging\\u000a methods such as echo-planar imaging through the effect of induced currents which produce tingling sensations and involuntary\\u000a muscle twitch. Neural stimulation could also trigger epileptic

  5. Charge gradient microscopy.

    PubMed

    Hong, Seungbum; Tong, Sheng; Park, Woon Ik; Hiranaga, Yoshiomi; Cho, Yasuo; Roelofs, Andreas

    2014-05-01

    Here we present a simple and fast method to reliably image polarization charges using charge gradient microscopy (CGM). We collected the current from the grounded CGM probe while scanning a periodically poled lithium niobate single crystal and single-crystal LiTaO3 thin film on the Cr electrode. We observed current signals at the domains and domain walls originating from the displacement current and the relocation or removal of surface charges, which enabled us to visualize the ferroelectric domains at a scan frequency above 78 Hz over 10 ?m. We envision that CGM can be used in high-speed ferroelectric domain imaging and piezoelectric energy-harvesting devices. PMID:24760831

  6. Coupled resonator vertical cavity laser

    SciTech Connect

    Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

    1998-01-01

    The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

  7. Dynamics of geckos running vertically

    Microsoft Academic Search

    K. Autumn; S. T. Hsieh; D. M. Dudek; J. Chen; C. Chitaphan; R. J. Full

    2006-01-01

    Geckos with adhesive toe pads rapidly climb even smooth vertical surfaces. We challenged geckos (Hemidactylus garnotii) to climb up a smooth vertical track that contained a force platform. Geckos climbed vertically at up to 77·cm·s -1 with a stride frequency of 15·Hz using a trotting gait. During each step, whole body fore-aft, lateral and normal forces all decreased to zero

  8. A Brightness-Temperature-Variance-Based Passive Microwave Algorithm for Monitoring Soil Freeze/Thaw State on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Han, M.; Yang, K.; Qin, J.; Jin, R.; Ma, Y.; Wen, J.; Chen, Y.; Zhao, L.; La, Z.; Tang, W.

    2014-12-01

    The land surface on the Tibetan Plateau experiences typical diurnal and seasonal freeze/thaw processes that play important roles in the regional water and energy exchanges, and recent passive microwave satellites provide opportunities to detect the soil state for the unique region. With the support of three soil moisture and temperature networks in the Tibetan Plateau, a dual-index microwave algorithm with AMSR-E (Advanced Microwave Scanning Radiometer-Earth Observing System) data is developed for the detection of soil surface freeze/thaw state. One index is the standard deviation index (SDI) of brightness temperature (TB), which is defined as the standard deviation of horizontally polarized brightness temperatures at all AMSR-E frequencies. It is the major index and is used to reflect the reduction of liquid water content after soils get frozen. The other index is the 36.5 GHz vertically-polarized brightness temperature, which is linearly correlated with ground temperature and thus is utilized to detect it. The threshold values of the two indices (SDI and the brightness temperature at 36.5 GHz vertically-polarized) are determined based on a part of in situ data from the network located in a semi-arid climate, and the algorithm was validated against other in situ data from this network. Further validations were conducted based on the other two networks located in different climates (semi-humid and arid, respectively). Results show that this algorithm has accuracy of more than 90% for the semi-humid and semi-arid regions, and misclassifications mainly occur at the transition period between unfrozen and frozen seasons. Nevertheless, the microwave signals have limited capability in identifying the soil surface freeze/thaw state in the arid region, because they can penetrate deep dry soils and thus embody the bulk information beneath the surface.

  9. Vertical landing on an asteroid

    NASA Technical Reports Server (NTRS)

    Harel, D.; Geulman, M.

    1992-01-01

    This work is concerned with the final approach phase and vertical landing on an asteroid with a power-limited, electrically propelled spacecraft. With gravitational effects taken into account, a new solution to the fuel optimal vertical landing on an asteroid was obtained. In this solution, the spacecraft commanded acceleration is explicitly expressed as a function of vehicle velocity and time to go. Based on qualitative methods of analysis, the guidance strategy and the resulting trajectories were studied. It is shown that these fuel-optimal trajectories effectively assure a vertical soft landing on the asteroid. Results of numerical simulations for the vertical landing, starting from an elliptical orbit are presented.

  10. Does Anxiety Cause Freezing of Gait in Parkinson's Disease?

    PubMed Central

    Ehgoetz Martens, Kaylena A.; Ellard, Colin G.; Almeida, Quincy J.

    2014-01-01

    Individuals with Parkinson's disease (PD) commonly experience freezing of gait under time constraints, in narrow spaces, and in the dark. One commonality between these different situations is that they may all provoke anxiety, yet anxiety has never been directly examined as a cause of FOG. In this study, virtual reality was used to induce anxiety and evaluate whether it directly causes FOG. Fourteen patients with PD and freezing of gait (Freezers) and 17 PD without freezing of gait (Non-Freezers) were instructed to walk in two virtual environments: (i) across a plank that was located on the ground (LOW), (ii) across a plank above a deep pit (HIGH). Multiple synchronized motion capture cameras updated participants' movement through the virtual environment in real-time, while their gait was recorded. Anxiety levels were evaluated after each trial using self-assessment manikins. Freezers performed the experiment on two separate occasions (in their ON and OFF state). Freezers reported higher levels of anxiety compared to Non-Freezers (p<0.001) and all patients reported greater levels of anxiety when walking across the HIGH plank compared to the LOW (p<0.001). Freezers experienced significantly more freezing of gait episodes (p?=?0.013) and spent a significantly greater percentage of each trial frozen (p?=?0.005) when crossing the HIGH plank. This finding was even more pronounced when comparing Freezers in their OFF state. Freezers also had greater step length variability in the HIGH compared to the LOW condition, while the step length variability in Non-Freezers did not change. In conclusion, this was the first study to directly compare freezing of gait in anxious and non-anxious situations. These results present strong evidence that anxiety is an important mechanism underlying freezing of gait and supports the notion that the limbic system may have a profound contribution to freezing in PD. PMID:25250691

  11. Particle-size dependence of immersion freezing: Investigation of INUIT test aerosol particles with freely suspended water drops.

    NASA Astrophysics Data System (ADS)

    Diehl, Karoline; Debertshäuser, Michael; Eppers, Oliver; Jantsch, Evelyn; Mitra, Subir K.

    2014-05-01

    One goal of the research group INUIT (Ice Nuclei research UnIT) is to investigate the efficiencies of several test ice nuclei under comparable conditions but with different experimental techniques. In the present studies, two methods are used: the Mainz vertical wind tunnel and an acoustic levitator placed inside a cold chamber. In both cases drops are freely levitated, either at their terminal velocity in the wind tunnel updraft or around the nodes of a standing ultrasonic wave in the acoustic levitator. Thus, heat transfer conditions are well approximated, and wall contact effects on freezing as well as electrical charges of the drops are avoided. Drop radii are 370 ?m and 1 mm, respectively. In the wind tunnel, drops are investigated at constant temperatures within a certain time period and the onset of freezing is observed directly. In the acoustic levitator, the drop temperature decreases during the experiments and is measured by an in-situ calibrated Infrared thermometer. The onset of freezing is indicated by a rapid rise of the drop surface temperature because of the release of latent heat. Investigated test ice nuclei are Snomax® as a proxy of biological particles and illite NX as well as K-feldspar as represents of mineral dust. The particle concentrations are 1 × 10-12 to 3 × 10-6 g Snomax® per drop and 5 × 10-9 to 5 × 10-5 g mineral dust per drop. Freezing temperatures are between -2 and -18° C in case of Snomax® and between -14 and -26° C in case of mineral dust. The lower the particle masses per drop the lower are the freezing temperatures. For similar particle concentrations in the drops, the median freezing temperatures determined by the two techniques agree well within the measurement errors. With the knowledge of the specific particle surface area of the mineral dusts, the results are interpreted also in terms of particle surface area per drop. Results from the wind tunnel experiments which are performed at constant temperatures indicate that the freezing times are shorter the lower the temperatures are. For evaluation and comparisons of the data, two models of heterogeneous freezing are applied, the stochastic and the time-independent singular description. The nucleation rate coefficients J(T) as well as the surface densities of active sites ns(T) or the numbers of active sites nm(T) are determined from the experimental data. It is shown that both models are suited to describe the present heterogeneous freezing results for the range of investigated particle masses or surface areas per drop. The comparison of the results from the two experimental techniques evaluated with the time-independent singular model indicates an excellent agreement within the measurement errors.

  12. Freezing of sessile water droplets on surfaces with various roughness and wettability

    NASA Astrophysics Data System (ADS)

    Hao, Pengfei; Lv, Cunjing; Zhang, Xiwen

    2014-04-01

    This paper focus on the freezing delay time and the freezing time of sessile droplet on smooth, micro-structured and micro/nano-structured surfaces, and the whole freezing process are comparatively studied. The freezing delay time of the smooth surfaces with roughness smaller than the size of the critical ice nuclei is found to be much longer than superhydrophobic surfaces with hierarchical structures. Experimental data and theoretical analysis show that the surface roughness plays a very crucial role in nucleation. The freezing delay time could not be extended further on rough surface with more superhydrophobic for sessile droplet. In addition, decreased roughness can increase the free energy barrier for heterogeneous nucleation, result in significant freezing delay. On the contrary, the freezing time from the start of nucleation to the completion of freezing increases with the contact angle. In addition, surfaces with hierarchical roughness are found to have the longest freezing time.

  13. Freeze-In Dark Matter with Displaced Signatures at Colliders

    E-print Network

    Co, Raymond T; Hall, Lawrence J; Pappadopulo, Duccio

    2015-01-01

    Dark matter, $X$, may be generated by new physics at the TeV scale during an early matter-dominated (MD) era that ends at temperature $T_R \\ll {\\rm TeV}$. Compared to the conventional radiation-dominated (RD) results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. Freeze-In is typically dominated by the decay of a particle $B$ of the thermal bath, $B \\rightarrow X$. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signals at LHC and future colliders, for any $m_X$ in the range ${\\rm keV} < m_X < m_B$ and for values of $m_B$ accessible to these colliders. This result applies whether the early MD era arises after conventional inflation, when $T_R$ is the usual reheat temperature, or is a generic MD era with an alternative origin. I...

  14. Units of freezing of deep supercooled water in woody xylem.

    PubMed

    Hong, S G; Sucoff, E

    1980-07-01

    The low temperature exotherms (LTE) of 1-year-old twigs of Haralson apple (Malus pumila Mill.), shagbark hickory (Carya ovata [Mill.] K. Koch), green ash (Fraxinus pennsylvanica Marsh), honey locust (Gleditsia triacanthos L.), American chestnut (Castanea dentata [Marsh] Borkh.), and red oak (Quercus rubra L.) were determined by differential thermal analysis (DTA). In one type of experiment freezing during a DTA experiment was halted for up to 2.5 hours after part of the supercooled water had frozen at temperatures between -25 and -42 C. Upon resumption of cooling the freezing started within 2 C of the stopping temperature. In a second type of experiment living and dead cells were microscopically observed in the same ray after partial freezing in the DTA apparatus. In another experiment, the LTE persisted even after tangential and radial sectioning of the twig to 0.13 millimeters. In a final experiment the LTE of a single multiseriate ray of red oak had the same shape as the LTE of wood with many uniseriate rays.These experiments confirm that the deep supercooled water in woody xylem or pith freezes in numerous independent events over a span of as much as 20 C. The units which freeze in an event are single cells or small groups of cells. Ice grows very slowly if at all from these units, and water moves very slowly from unfrozen cells to frozen ones. Deep supercooling of ray parenchyma does not require an intact ray. PMID:16661390

  15. Empirical equation estimates geothermal gradients

    SciTech Connect

    Kutasov, I.M. (MultiSpectrum Technologies, Santa Monica, CA (United States))

    1995-01-02

    An empirical equation can estimate geothermal (natural) temperature profiles in new exploration areas. These gradients are useful for cement slurry and mud design and for improving electrical and temperature log interpretation. Downhole circulating temperature logs and surface outlet temperatures are used for predicting the geothermal gradients.

  16. Subspace gradient domain mesh deformation

    Microsoft Academic Search

    Jin Huang; Xiaohan Shi; Xinguo Liu; Kun Zhou; Li-yi Wei; Shang-hua Teng; Hujun Bao; Baining Guo; Heung-yeung Shum

    2006-01-01

    In this paper we present a general framework for performing con- strained mesh deformation tasks with gradient domain techniques. We present a gradient domain technique that works well with a wide variety of linear and nonlinear constraints. The constraints we introduce include the nonlinear volume constraint for volume preservation, the nonlinear skeleton constraint for maintaining the rigidity of limb segments

  17. Multilayer transverse gradient coil design

    Microsoft Academic Search

    J. Leggett; S. Crozier; S. Blackband; B. Beck; R. W. Bowtell

    2003-01-01

    In small, cylindrical gradient coils consisting of a single layer of wires, the limiting factor in achieving large magnetic field gradients is the rapid increase in coil resistance with efficiency. This behavior results from the decrease in the maximum usable wire diameter as the number of turns is increased. By adopting a multilayer design in which the coil wires are

  18. Height and gradient from shading

    Microsoft Academic Search

    Berthold K. P. Horn

    1990-01-01

    The method described here for recovering the shape of a surface from a shaded image can deal with complex, wrinkled surfaces. Integrability can be enforced easily because both surface height and gradient are represented (A gra- dient field is integrable if it is the gradient of some surface height function). The robustness of the method stems in part from linearization

  19. Preparation of chitosan nanocompositeswith a macroporous structure by unidirectional freezing and subsequent freeze-drying.

    PubMed

    Aranaz, Inmaculada; Gutiérrez, María C; Ferrer, María Luisa; del Monte, Francisco

    2014-11-01

    Chitosan is the N-deacetylated derivative of chitin, a naturally abundant mucopolysaccharide that consists of 2-acetamido-2-deoxy-?-d-glucose through a ? (1?4) linkage and is found in nature as the supporting material of crustaceans, insects, etc. Chitosan has been strongly recommended as a suitable functional material because of its excellent biocompatibility, biodegradability, non-toxicity, and adsorption properties. Boosting all these excellent properties to obtain unprecedented performances requires the core competences of materials chemists to design and develop novel processing strategies that ultimately allow tailoring the structure and/or the composition of the resulting chitosan-based materials. For instance, the preparation of macroporous materials is challenging in catalysis, biocatalysis and biomedicine, because the resulting materials will offer a desirable combination of high internal reactive surface area and straightforward molecular transport through broad "highways" leading to such a surface. Moreover, chitosan-based composites made of two or more distinct components will produce structural or functional properties not present in materials composed of one single component. Our group has been working lately on cryogenic processes based on the unidirectional freezing of water slurries and/or hydrogels, the subsequent freeze-drying of which produce macroporous materials with a well-patterned structure. We have applied this process to different gels and colloidal suspensions of inorganic, organic, and hybrid materials. In this review, we will describe the application of the process to chitosan solutions and gels typically containing a second component (e.g., metal and ceramic nanoparticles, or carbon nanotubes) for the formation of chitosan nanocomposites with a macroporous structure. We will also discuss the role played by this tailored composition and structure in the ultimate performance of these materials. PMID:25421320

  20. Latitude and longitude vertical disparities.

    PubMed

    Read, Jenny C A; Phillipson, Graeme P; Glennerster, Andrew

    2009-01-01

    The literature on vertical disparity is complicated by the fact that several different definitions of the term "vertical disparity" are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude disparities. Near the fixation point, these definitions become equivalent, but in general, they have quite different dependences on object distance and binocular eye posture, which have not previously been spelt out. We present analytical approximations for each type of vertical disparity, valid for more general conditions than previous derivations in the literature: we do not restrict ourselves to objects near the fixation point or near the plane of regard, and we allow for non-zero torsion, cyclovergence, and vertical misalignments of the eyes. We use these expressions to derive estimates of the latitude and longitude vertical disparities expected at each point in the visual field, averaged over all natural viewing. Finally, we present analytical expressions showing how binocular eye position-gaze direction, convergence, torsion, cyclovergence, and vertical misalignment-can be derived from the vertical disparity field and its derivatives at the fovea. PMID:20055544

  1. Functions and Vertical Line Test

    NSDL National Science Digital Library

    2010-01-01

    This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

  2. Measuring Growth with Vertical Scales

    ERIC Educational Resources Information Center

    Briggs, Derek C.

    2013-01-01

    A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

  3. Rapid Gradient-Echo Imaging

    PubMed Central

    Hargreaves, Brian

    2012-01-01

    Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

  4. Gradient elution in capillary electrochromatography

    SciTech Connect

    Anex, D.; Rakestraw, D.J. [Sandia National Labs., Livermore, CA (United States); Yan, Chao; Dadoo, R.; Zare, R.N. [Stanford Univ., CA (United States). Dept. of Chemistry

    1997-08-01

    In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically-driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with sub-mL/min flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-mm reversed-phase particles. The inlet of one capillary arm is placed in a solution reservoir containing one mobile phase and the inlet of the other is placed in a second reservoir containing a second mobile phase. Two independent computer-controlled programmable high-voltage power supplies (0-50 kV)--one providing an increasing ramp and the other providing a decreasing ramp--are used to apply variable high-voltage potentials to the mobile phase reservoirs to regulate the electroosmotic flow in each arm. The ratio of the electroosmotic flow rates between the two arms is changed with time according to the computer-controlled voltages to deliver the required gradient profile to the separation column. Experiments were performed to confirm the composition of the mobile phase during a gradient run and to determine the change of the composition in response to the programmed voltage profile. To demonstrate the performance of electroosmotically-driven gradient elution in CEC, a mixture of 16 polycyclic aromatic hydrocarbons (PAHs) was separated in less than 90 minutes. This gradient technique is expected to be well-suited for generating not only solvent gradients in CEC, but also other types of gradients such as pH- and ionic-strength gradients in capillary electrokinetic separations and analyses.

  5. In favour of freezing eggs for non-medical reasons.

    PubMed

    Goold, Imogen; Savulescu, Julian

    2009-01-01

    This article explores the social benefits and moral arguments in favour of women and couples freezing eggs and embryos for social reasons. Social IVF promotes equal participation by women in employment; it offers women more time to choose a partner; it provides better opportunities for the child as it allows couples more time to become financially stable; it may reduce the risk of genetic and chromosomal abnormality; it allows women and couples to have another child if circumstances change; it offers an option to women and children at risk of ovarian failure; it may increase the egg and embryo pool. There are strong arguments based on equal concern and respect for women which require that women have access to this new technology. Freezing eggs also avoids some of the moral objections associated with freezing embryos. PMID:19076941

  6. High-freezing-point fuels used for aviation turbine engines

    NASA Technical Reports Server (NTRS)

    Friedman, R.

    1979-01-01

    Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. The higher-freezing-point fuels can be substituted in the majority of present commercial flights, since temperature data indicate that in-flight fuel temperatures are relatively mild. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple system design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating. Both systems offer advantages that outweigh the obvious penalties.

  7. Freezing of gait: a practical approach to management.

    PubMed

    Nonnekes, Jorik; Snijders, Anke H; Nutt, John G; Deuschl, Günter; Giladi, Nir; Bloem, Bastiaan R

    2015-07-01

    Freezing of gait is a common and disabling symptom in patients with parkinsonism, characterised by sudden and brief episodes of inability to produce effective forward stepping. These episodes typically occur during gait initiation or turning. Treatment is important because freezing of gait is a major risk factor for falls in parkinsonism, and a source of disability to patients. Various treatment approaches exist, including pharmacological and surgical options, as well as physiotherapy and occupational therapy, but evidence is inconclusive for many approaches, and clear treatment protocols are not available. To address this gap, we review medical and non-medical treatment strategies for freezing of gait and present a practical algorithm for the management of this disorder, based on a combination of evidence, when available, and clinical experience of the authors. Further research is needed to formally establish the merits of our proposed treatment protocol. PMID:26018593

  8. Deconfinement of strangeness and freeze-out from charge fluctuations

    E-print Network

    Swagato Mukherjee; Mathias Wagner

    2013-07-23

    We use Lattice QCD calculations of fluctuations and correlations of various conserved charges to show that the deconfinement of strangeness takes place in the chiral crossover region of QCD; however, inside the quark-gluon plasma strange quarks remain strongly interacting at least up to temperatures twice the QCD crossover temperature. Further, we discuss how the freeze-out parameters of heavy-ion collisions can be determined in a model-independent way through direct comparisons between experimentally measured higher order cumulants of conserved charges and corresponding Lattice QCD calculations. Utilizing the preliminary data from the STAR and PHENIX experiments we illustrate this method. Although, the Lattice QCD based determinations of the freeze-out parameters utilizing data sets of different experiments and different observables are currently not consistent with each other, it is tantalizing to see that all the observed freeze-out parameters lie very close to the chiral/deconfinement crossover region of QCD.

  9. Capture of spatially homogeneous chemical reactions in tissue by freezing.

    PubMed Central

    Clark, A; Clark, P A

    1983-01-01

    A useful technique in studying the saturation of hemoglobin in erythrocytes or myoglobin in tissue is cryophotometry, in which tissue is frozen for later spectrophotometric analysis. A general question associated with this technique is whether the freezing process alters the chemical state. This paper presents a theoretical analysis of the simplest model relevant to that question. We study the effect of rapid cooling on a spatially homogeneous chemical reaction. The analysis shows that changes during freezing are negligible near the boundary to which the heat sink is applied, but can be significant deeper in the sample. The distance from the boundary at which the changes during freezing become appreciable can be expressed simply in terms of the chemical reaction rates and the thermal diffusivity of the tissue. Detailed results are given for the case of oxygen and myoglobin in skeletal muscle. PMID:6838980

  10. The development of a freezing rain sensor for automated surface observing systems

    NASA Astrophysics Data System (ADS)

    Starr, Kevin M.; van Cauwenberghe, Roger

    A freezing precipitations sensor and reporting algorithms have been developed that accurately indicate ice accumulation on aircraft. The sensor and algorithms are briefly described and test results in freezing rain and freezing drizzle, wet snow, and dense fog are discussed. The sensor provides consistent and sensitive indications of ice accumulation under these conditions. Some detection insensitivity occurs when the temperature is at or above freezing or when the ice accumulation is trace. The algorithms are successful in reporting the indications of ice accumulation as either freezing rain or wet snow. Sensor precision is mostly very good and deicing time is negligble except when the temperature is very close to freezing.

  11. Effect of freezing on Fossomatic cell counting in ewe milk.

    PubMed

    Martínez, J R; Gonzalo, C; Carriedo, J A; San Primitivo, F

    2003-08-01

    Using the Fossomatic method, a total of 10,072 analytical somatic cell count (SCC) observations were carried out on 4760 aliquots taken from 70 individual ewe milk samples with the objective of studying whether freezing showed significant differences of SCC in comparison with refrigeration, according to different analytical conditions. These conditions were four preservation procedures (without preservation, potassium dichromate, azidiol, and bronopol), two storage temperatures (refrigeration and freezing), five milk ages within storage (24 h postcollection in refrigeration, and 24 h, 15, 30, and 60 d postcollection in freezing), two thawing types (rapid and slow), and two analytical temperatures (40 and 60 degrees C). Preservation, storage, and analytical temperature, type of thawing and milk age within storage, and most of the interactions showed a significant effect on the SCC variation. On average, the SCC was lower after freezing than in refrigeration. This effect depended specifically on type of preservation and analytical temperature of milk. The SCC of milk unpreserved or preserved with bronopol or potassium dichromate, and analyzed at 40 degrees C, was not affected by freezing; however, use of azidiol as a preservative before freezing, and heating the milk to 60 degrees C following thawing resulted in significantly decreased SCC. Milk age had little quantitative influence on SCC of thawed milk. The type of thawing (rapid and slow) did not significantly influence SCC of milk analyzed at 40 degrees C. As a result, when using properly handled samples, the Fossomatic method could be used to enumerate SCC in samples frozen over the 60 d. PMID:12939082

  12. Ultrasonic emissions from conifer xylem exposed to repeated freezing.

    PubMed

    Mayr, Stefan; Zublasing, Verena

    2010-01-01

    Ultrasonic emission measurements enable the analysis of xylem cavitation induced by drought and freeze-thaw events. Several studies have indicated that ultrasonic acoustic emissions (UAE) in conifers occur upon freezing and not upon thawing, although classical theory has postulated gas bubble formation during freezing and cavitation during thawing. We analyzed the pattern and quality of freeze-thaw-induced UAE in seven conifers (Abies alba, Larix decidua, Juniperus communis, Picea abies, Pinus cembra, Pinus mugo, Pinus sylvestris). Axes samples dehydrated to different water potentials were exposed to repeated frost cycles. The number, amplitude and energy of UAE signals were registered and related to water potential, temperature course and wood characteristics (wood density, tracheid diameter). For P. abies, ultrasonic emission analysis was also performed on bark samples, xylem samples without bark, as well as on stems of young potted trees. In all conifers, UAE were registered in water-stressed samples but not in saturated or dehydrated samples. No signals were emitted by the bark of P. abies. Ultrasonic activity occurred only upon freezing, and identical patterns were observed in axes samples and stems of potted P. abies trees. A weak positive relationship between tracheid diameter and UAE energy was observed, indicating wide tracheids to emit signals with higher energy. The classical bubble formation hypothesis cannot sufficiently explain the occurrence of UAE during freezing and upon repeated temperature cycles, as demonstrated in this study. We suggest that the low water potential of ice induces air-seeding near the ice-water interface, and consequently, causes UAE. PMID:19692146

  13. Light gradients and optical microniches in coral tissues

    PubMed Central

    Wangpraseurt, Daniel; Larkum, Anthony W. D.; Ralph, Peter J.; Kühl, Michael

    2012-01-01

    Light quantity and quality are among the most important factors determining the physiology and stress response of zooxanthellate corals. Yet, almost nothing is known about the light field that Symbiodinium experiences within their coral host, and the basic optical properties of coral tissue are unknown. We used scalar irradiance microprobes to characterize vertical and lateral light gradients within and across tissues of several coral species. Our results revealed the presence of steep light gradients with photosynthetically available radiation decreasing by about one order of magnitude from the tissue surface to the coral skeleton. Surface scalar irradiance was consistently higher over polyp tissue than over coenosarc tissue in faviid corals. Coral bleaching increased surface scalar irradiance by ~150% (between 500 and 700 nm) relative to a healthy coral. Photosynthesis peaked around 300 ?m within the tissue, which corresponded to a zone exhibiting strongest depletion of scalar irradiance. Deeper coral tissue layers, e.g., ~1000 ?m into aboral polyp tissues, harbor optical microniches, where only ~10% of the incident irradiance remains. We conclude that the optical microenvironment of corals exhibits strong lateral and vertical gradients of scalar irradiance, which are affected by both tissue and skeleton optical properties. Our results imply that zooxanthellae populations inhabit a strongly heterogeneous light environment and highlight the presence of different optical microniches in corals; an important finding for understanding the photobiology, stress response, as well as the phenotypic and genotypic plasticity of coral symbionts. PMID:22969755

  14. A vertical microfluidic probe.

    PubMed

    Kaigala, G V; Lovchik, R D; Drechsler, U; Delamarche, E

    2011-05-01

    Performing localized chemical events on surfaces is critical for numerous applications. We earlier invented the microfluidic probe (MFP), which circumvented the need to process samples in closed microchannels by hydrodynamically confining liquids that performed chemistries on surfaces (Juncker et al. Nat. Mater. 2005, 4, 622-628). Here we present a new and versatile probe, the vertical MFP (vMFP), which operates in the scanning mode while overcoming earlier challenges that limited the practical implementation of the MFP technology. The key component of the vMFP is the head, a microfluidic device (?1 cm(2) in area) consisting of glass and Si and having microfluidic features fabricated in-plane in the Si layer. The base configuration of the head has two micrometer-size channels that inject/aspirate liquids and terminate at the apex which is ?1 mm(2). In scanning mode, the head is oriented vertically with the apex parallel to the surface with typical spacing of 1-30 ?m. Such length scales and using flow rates from nanoliters/second to microliters/second allow chemical events to be performed on surfaces with tens of picoliter quantities of reagents. Before scanning, the head is clipped on a holder for leak-free, low dead volume interface assembly, providing a simple world-to-chip interface. Surfaces are scanned by mounting the holder on a computer-controlled stage having ?0.1 ?m resolution in positioning. We present detailed steps to fabricate vMFP heads having channels with dimensions from 1 ?m × 1 ?m to 50 ?m × 50 ?m for liquid localization over areas of 10-10,000 ?m(2). Additionally, advanced design strategies are described to achieve high yield in fabrication and to support a broad range of applications. These include particulate filters, redundant aperture architectures, inclined flow-paths that service apertures, and multiple channels to enable symmetric flow confinement. We also present a method to characterize flow confinement and estimate the distance between the head and the surface by monitoring the evolution of a solution of fluorescently labeled antibody on an activated glass surface. This flow characterization reveals regimes of operation suitable for different surface topographies. We further integrate the dispensing of immersion liquid to the vMFP head for processing surfaces for extended periods of time (?60 min). The versatility of the vMFP is exemplified by patterning fluorescently labeled proteins, inactivation of cells using sodium hypochlorite, and staining living NIH fibroblasts with Cellomics. These applications are enabled by the compact design of the head, which provides easy access to the surface, simplifies alignment, and enables processing surfaces having dimensions from the micrometer to the centimeter scale and with large topographical variations. We therefore believe that ease-of-operation, reconfigurability, and conservative use of chemicals by the vMFP will lead to its widespread use by microtechnologists and the chemical and biomedical communities. PMID:21476506

  15. Thermal and Chemical Freeze-out in Spectator Fragmentation

    E-print Network

    W. Trautmann; R. Bassini; M. Begemann-Blaich; A. Ferrero; S. Fritz; S. J. Gaff-Ejakov; C. Gross; G. Imme; I. Iori; U. Kleinevoss

    2007-12-17

    Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragmentation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.

  16. Freeze-out conditions from fluctuations of conserved charges

    NASA Astrophysics Data System (ADS)

    Ratti, C.; Borsanyi, S.; Fodor, Z.; Katz, S. D.; Krieg, S.; Szabo, K. K.

    2014-11-01

    The latest results on fluctuations of electric charge and baryon number, simulated on the lattice by the Wuppertal-Budapest Collaboration, are compared to the moments of multiplicity distribution of the corresponding conserved charges, measured in heavy ion collision experiments by the STAR Collaboration. The purpose of this study is to extract the chemical freeze-out parameters (temperature and chemical potential) as a function of the collision energy, from first principles. Consistency between the freeze-out parameters obtained through the two different conserved charges used in the analysis is discussed.

  17. Thermal and chemical freeze-out in spectator fragmentation

    NASA Astrophysics Data System (ADS)

    Trautmann, W.; Bassini, R.; Begemann-Blaich, M.; Ferrero, A.; Fritz, S.; Gaff-Ejakov, S. J.; Groß, C.; Immé, G.; Iori, I.; Kleinevoß, U.; Kunde, G. J.; Kunze, W. D.; Fèvre, A. Le; Lindenstruth, V.; ?ukasik, J.; Lynen, U.; Maddalena, V.; Mahi, M.; Möhlenkamp, T.; Moroni, A.; Müller, W. F. J.; Nociforo, C.; Ocker, B.; Odeh, T.; Orth, H.; Petruzzelli, F.; Pochodzalla, J.; Raciti, G.; Riccobene, G.; Romano, F. P.; Rubehn, Th.; Saija, A.; Sann, H.; Schnittker, M.; Schüttauf, A.; Schwarz, C.; Seidel, W.; Serfling, V.; Sfienti, C.; Trzci?ski, A.; Tucholski, A.; Verde, G.; Wörner, A.; Xi, Hongfei; Zwiegli?ski, B.

    2007-12-01

    Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in He4, Li5, and Be8, were determined for spectator fragmentation, following collisions of Au197 with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.

  18. High freezing point fuels used for aviation turbine engines

    NASA Technical Reports Server (NTRS)

    Friedman, R.

    1979-01-01

    Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating.

  19. Thermal and chemical freeze-out in spectator fragmentation

    SciTech Connect

    Trautmann, W.; Begemann-Blaich, M.; Fritz, S.; Gross, C.; Kleinevoss, U.; Kunze, W. D.; Le Fevre, A.; Lynen, U.; Mahi, M.; Mueller, W. F. J.; Odeh, T.; Orth, H.; Rubehn, Th.; Sann, H.; Schnittker, M.; Schwarz, C.; Sfienti, C.; Woerner, A.; Xi Hongfei [Gesellschaft fuer Schwerionenforschung mbH, D-64291 Darmstadt (Germany); Bassini, R. [Istituto di Scienze Fisiche, Universita degli Studi di Milano and I. N. F. N., I-20133 Milano (Italy)] (and others)

    2007-12-15

    Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in {sup 4}He, {sup 5}Li, and {sup 8}Be, were determined for spectator fragmentation, following collisions of {sup 197}Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.

  20. Surface Nucleation in the Freezing of Gold Nanoparticles

    E-print Network

    Eduardo Mendez-Villuendas Richard K. Bowles

    2007-04-03

    We use molecular simulation to calculate the nucleation free energy barrier for the freezing of a 456 atom gold cluster over a range of temperatures. The results show that the embryo of the solid cluster grows at the vapor-surface interface for all temperatures studied and that the usual classical nucleation model, with the embryo growing in the core of the cluster, is unable to predict the shape of the free energy barrier. We use a simple partial wetting model that treats the crystal as a lens shaped nucleus at the liquid-vapor interface and find that the line tension plays an important role in the freezing of gold nanoparticles.

  1. Freezing of Spinodal Decompostion by Irreversible Chemical Growth Reaction

    E-print Network

    Michael Schulz; Benjamin Paul

    1998-08-10

    We present a description of the freezing of spinodal decomposition in systems, which contain simultaneous irreversible chemical reactions, in the hydrodynamic limit approximation. From own results we conclude, that the chemical reaction leads to an onset of spinodal decomposition also in the case of an initial system which is completely miscible and can lead to an extreme retardation of the dynamics of the spinodal decomposition, with the probability of a general freezing of this process, which can be experimetally observed in simultaneous IPN formation.

  2. Ice cube maker with new freeze and harvest control

    SciTech Connect

    Josten, M.H.; Merrill, T.L.; Schneider, K.W.; Utter, R.F.

    1988-03-29

    A method of making ice cubes is described comprising the steps of (a) sensing the size of ice frozen upon an evaporator; (b) initiating a hot gas defrost of the evaporator upon the sensing of a predetermined size of ice, and thereby and thereafter harvesting the ice from the evaporator; (c) dropping the ice off of the evaporator and against a curtain; (d) opening the curtain with the dropping ice; (e) changing the mode of a photoelectric emitter-receiver with the curtain during the opening; and (f) terminating the hot gas defrost and restarting a freeze cycle in response to the mode changing, and freezing a subsequent quantity of ice.

  3. Different algal symbionts explain the vertical distribution of dominant reef corals in the eastern Pacific

    Microsoft Academic Search

    R. Iglesias-Prieto; V. H. Beltran; T. C. LaJeunesse; H. Reyes-Bonilla; P. E. Thome

    2004-01-01

    Symbiotic reef corals occupy the entire photic zone; however, most species have distinct zonation patterns within the light intensity gradient. It is hypothesized that the presence of specific symbionts adapted to different light regimes may determine the vertical distribution of particular hosts. We have tested this hypothesis by genetic and in situ physiological analyses of the algal populations occupying two

  4. Laminar forced convection wake above a series of vertical parallel plates

    Microsoft Academic Search

    Zakaria Doulfoukar; Abderrahim Achiq

    2004-01-01

    The study of a laminar forced convection wake above a series of vertical parallel plates is carried out. The development of momentum and energy fields in the near wake is studied analytically. Velocity, temperature and pressure gradient are presented in asymptotic expressions. Furthermore, the temperature in the immediate neighbourhood of the trailing edges, along the plates, is presented in a

  5. Vertical profiles of wind speed, snow concentration, and humidity in blowing snow

    Microsoft Academic Search

    R. A. Schmidt

    1982-01-01

    To estimate the sublimation rate of snow during relocation by wind, sizes and concentration of ice crystal fragments were measured at 6 levels in the lowest 1 m, during ten 10-min runs, in a nocturnal blizzard. Power-law functions of height described the decrease in mean particle diameter and concentration. The vertical gradient of water vapor, measured with a thermocouple psychrometer,

  6. The sub-lethal effects of repeated freezing in the woolly bear caterpillar Pyrrharctia isabella.

    PubMed

    Marshall, Katie E; Sinclair, Brent J

    2011-04-01

    Repeated freeze-thaw cycles are common and are increasing in frequency with climate change in many temperate locations, yet understanding of their impact on freeze-tolerant insects is extremely limited. We investigated the effects of repeated freezing and thawing on the freeze-tolerant final instar caterpillars of the moth Pyrrharctia isabella (Lepidoptera: Arctiidae) by subjecting individuals to either a single sustained 35 h freeze or five 7 h freezes. Sub-lethal effects were quantified with changes in three broad groups of measures: (1) cold hardiness, (2) metabolic rate and energy reserves and (3) survival after challenge with fungal spores. Repeated freeze-thaw cycles increased mortality to almost 30% and increased tissue damage in Malpighian tubules and hemocytes. Repeated freezing increased caterpillar glycerol concentration by 0.82 mol l(-1). There were no changes in metabolic rate or energy reserves with repeated freezing. For the first time, we report increased survival after immune challenge in caterpillars after freezing and suggest that this may be linked to wounding during freezing. We suggest that little repair of freezing damage is possible in P. isabella caterpillars and repeated freeze-thaw cycles may present significant challenges to survival in this species. PMID:21389206

  7. Equivalent Magnetization Current Method Applied to the Design of Gradient Coils for Magnetic Resonance Imaging

    Microsoft Academic Search

    Hector Sanchez Lopez; Feng Liu; Michael Poole; Stuart Crozier

    2009-01-01

    A new method is described for the design of gradient coils for magnetic resonance imaging systems. The method is based on the known equivalence between a magnetized volume surrounded by a conducting surface and its equivalent representation by a surface current density. The curl of a vertical magnetization vector of a magnetized thin volume is equivalent to a surface current

  8. The equivalent magnetizing method applied to the design of gradient coils for MRI

    Microsoft Academic Search

    Hector Sanchez Lopez; Feng Liu; Stuart Crozier

    2008-01-01

    This paper presents a new method for the design of gradient coils for Magnetic Resonance Imaging systems. The method is based on the equivalence between a magnetized volume surrounded by a conducting surface and its equivalent representation in surface current\\/charge density. We demonstrate that the curl of the vertical magnetization induces a surface current density whose stream line defines the

  9. Average electron content gradients and nighttime electron fluxes in the mid-latitude ionosphere

    Microsoft Academic Search

    A. Ebel; G. Schmidt; A. Tauriainen

    1976-01-01

    The behavior of the meridional component of the ionospheric total electron content (TEC) gradient over Lindau (52 deg N, 10 deg E) is investigated in connection with temporal TEC changes using the medians of both quantities. Average TEC increases and their interpretation in terms of vertical and horizontal plasma fluxes are examined. Regular northward ionization increases are found near sunrise

  10. High field gradient particle accelerator

    DOEpatents

    Nation, J.A.; Greenwald, S.

    1989-05-30

    A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

  11. Underground thermo-erosion of ice wedges: numerical simulation of tunnel freeze- back

    NASA Astrophysics Data System (ADS)

    Kim, K.; Fortier, D.

    2008-12-01

    On Bylot Island in the Eastern Canadian Arctic archipelago, Fortier et al. (2007) observed and characterized the formation and development of tunnels initiated by the process of underground thermo-erosion of ice wedges networks. These tunnels often collapsed during the course of one or two summers and developed into gullies. However, observations of such tunnels in permafrost exposures indicate that they can be preserved in the permafrost record. The objective of this study is to estimate the freeze-back time of tunnels filled with water and slurry in cold and warm permafrost conditions. Ultimately, the goal is to evaluate time the tunnels remain "open"" for groundwater flow. We used numerical thermal modeling to conduct simple simulations of the conductive heat transfer during freeze-back of the tunnels. The thermal analyses were performed using the GeoslopeTM unsteady finite element heat conduction model TEMP/W. We used Bylot Island, Nunavut, Canada (Mean air temperature around -15 C) as a cold permafrost study case and Beaver Creek, Yukon Territory, Canada (Mean annual air temperature around -5.5C) as a warm permafrost study case. The air temperature was converted to ground surface temperature by the n-factor method. Zero heat flux was applied at the vertical and bottom boundaries due to the permafrost which is several tens to hundreds of meters thick. Based on previous studies, we simulated tunnels partly cut in ice-wedges and in the adjacent permafrost. The syngenetic permafrost of the case studies was assumed to be fully saturated with 110% gravimetric water content. The geometry of the tunnels was based on field measurements on Bylot Island. We considered three scenarios for the slurry filling the tunnels: 1) 100% water; 2) fully saturated sand with 30% gravimetric water content; and 3) an air layer at the top of the tunnel with water and saturated sands partly filling the bottom of the tunnel. We used three water/slurry temperatures: 1) 0.5C which simulates the water temperature of early snowmelt run-off, a period of active underground thermo- erosion; 2) 2C corresponding to the water temperature of run-off over a partly frozen active layer, which is typical for early summer undergrouns thermo-erosion ; 3) 5C and 15C corresponding to the water temperature lakes at the end of August on Bylot Island and at Beaver Creek respectively. This scenario simulates underground thermo-erosion due to lake drainage through ice wedges. The volumetric heat capacity of the ground was calculated as the sum of the volumetric heat capacities of the three phases multiplied by their volumetric fractions. The thermal conductivity of the permafrost and slurry was calculated by the geometric mean model. The apparent heat capacity method was applied to deal with latent heat generation. The initial permafrost temperature was -12C for the cold permafrost case and -2.5C for the warm permafrost case. The results suggest that thermo-erosion of ice wedges creates underground water flow paths that remain unfrozen for significant period of time, particularly in warm permafrost conditions. Tunnels entirely filled with water took about 1.5 to 2 times longer to freeze back. The presence of air pockets in the tunnel significantly delayed the freeze back time. In the cold permafrost cases, the tunnels froze back in about 3 to 6 months whereas they required between 8 months to about 3 years to freeze back in the warm permafrost cases.

  12. Gradient characterization in magnetic resonance imaging

    E-print Network

    Cheng, Joseph Yitan

    2007-01-01

    Special magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, ...

  13. Investigation of rapid freeze prototyping and investment casting with ice patterns

    NASA Astrophysics Data System (ADS)

    Liu, Qingbin

    Rapid Freeze Prototyping (RFP) can generate three-dimensional ice patterns from CAD models by depositing and solidifying water droplets layer by layer. The waiting time between two successive layers is a critical factor. Finite Element Analysis (FEA) is employed to predict the solidification time of a newly deposited water layer in order to develop a better understanding of heat transfer during the RFP process. The result is used to investigate the effects of various process parameters on the solidification time of an ice column and a vertical ice wall. Experiments are conducted and the measured results are shown to agree well with simulation results. Investment casting with ice patterns is similar to that with wax patterns but with significant process differences. An interface agent can be coated around the ice pattern to protect it from damage during the process. To compensate for the thickness of the interface agent, analytical models have been constructed to predict the thickness of the interface agent for a large ice cylinder and for a small ice part. The dimensional accuracy of the generated metal castings for small parts can be much improved by compensating the interface layer thickness. Due to the use of ice, canned models must be made at sub-freezing temperatures. Success of this process depends significantly on curing kinetics of the slurries and the fracture toughness of mold materials. The curing kinetics of the slurries and mold material fracture toughness from different compositions are examined and the effects of various processing parameters on the results are examined and discussed.

  14. Estimations of the coefficient of vertical turbulent transfer in the lower thermosphere

    NASA Astrophysics Data System (ADS)

    Chunchuzov, E. P.; Shagaev, M. V.

    1984-02-01

    An important parameter of the turbopause, the coefficient of vertical turbulent exchange transfer, may be evaluated in terms of the turbulent energy generation rate, the horizontal gradient of the mean temperature, and a constant (g/Coriolus parameter for middle latitudes). For a determination of the horizontal gradient, a series of temperature measurements were made in three different regions of the night sky. Simultaneous temperature measurements were made across two OH bands. Standard spectral analysis was used to determine the other properties. Individual values of the gradients were significantly large (on the average 0.052 K/km with a dispersion 0.019 K/km), as was the isotropic distribution. This is in part due to internal-gravity-wave dissipation at the hydroxyl layer altitudes. The calculated coefficients of vertical turbulent transfer agree well with a value obtained by rocket methods.

  15. Ground-based measurements of immersion freezing in the eastern Mediterranean

    E-print Network

    Levin, Z.

    Ice nuclei were measured in immersion-freezing mode in the eastern Mediterranean region using the FRIDGE-TAU (FRankfurt Ice-nuclei Deposition freezinG Experiment, the Tel Aviv University version) chamber. Aerosol particles ...

  16. Experimental research of "microcable in a microconduct" system stability to effect of freezing water

    NASA Astrophysics Data System (ADS)

    Andreev, Vladimir A.; Burdin, Vladimir A.; Nikulina, Tatiana G.; Alekhin, Ivan N.; Gavryushin, Sergey A.; Nikulin, Aleksey G.; Praporshchikov, Denis E.

    2011-12-01

    Results of experimental researches of "optical microcable in a microduct" system stability to effect of freezing water are presented. It is shown this system is steadier to water freezing in comparison to lighten optical cable in protective polymer tube.

  17. Can freezing cause floods on Mars? Chi-yuen Wang,1

    E-print Network

    Manga, Michael

    Can freezing cause floods on Mars? Chi-yuen Wang,1 Michael Manga,1 and Jeffrey C. Hanna2 Received channels by repeated floods. Citation: Wang, C.,M. Manga, and J. C. Hanna (2006), Can freezing cause floods

  18. SPECIAL FEATURE Latitudinal Gradients1

    E-print Network

    Agrawal, Anurag

    2261 SPECIAL FEATURE Latitudinal Gradients1 In 1772, J. R. Forster sailed with Captain Cook, and Forster sampled the flora throughout the Pacific. On his return, he published his account of the voyage

  19. Vertically scanned laser sheet microscopy

    NASA Astrophysics Data System (ADS)

    Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

    2014-10-01

    Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.

  20. Correlated Knowledge Gradients: Example alternatives

    E-print Network

    Keinan, Alon

    Correlated Knowledge Gradients: Example -4 -2 0 2 4 alternatives value 0 10 20 30 -10 -8 -6 -4 -2 0;Correlated Knowledge Gradients: Example -4 -2 0 2 4 alternatives value 0 10 20 30 -10 -8 -6 -4 -2 0 num measurements log(KGfactor) 0 10 20 30 0 0.5 1 1.5 2 num measurements opportunitycost #12;Correlated Knowledge

  1. Freeze-drying of bioproducts: putting principles into practice

    Microsoft Academic Search

    Felix Franks

    1998-01-01

    The product and process parameters that determine successful freeze-drying are described and their interrelationships are explored. It is shown that the thermochemical and thermomechanical properties of water-soluble, amorphous materials form the basis of effective formulation design and that coordinated approaches to formulation and process development achieve optimum results with a minimum of trial-and-error experimentation.

  2. Research and Development Needs and Opportunities in Freeze Drying

    Microsoft Academic Search

    A. I. Liapis; M. L. PIM; R. Bruttini

    1996-01-01

    Experimental and theoretical research and development studies are preposed and presented in important areas of the freeze drying process. The practical importance of the synergistic integration of advanced theoretical models and experiments is indicated, and the potential contributions of the proposed

  3. Characterization of vacuum microwave, air and freeze dried carrot slices

    Microsoft Academic Search

    Tein M Lin; Timothy D. Durance; Christine H Scaman

    1998-01-01

    Vacuum microwave drying of carrot slices was compared to air drying and freeze drying on the basis of rehydration potential, color, density, nutritional value, and textural properties. Vacuum microwave dried (VMD) carrot slices had higher rehydration potential, higher ?-carotene and vitamin C content, lower density, and softer texture than those prepared by air drying. Carrot slices that were air dried

  4. Freeze-Drying of the Black Currant Juice

    Microsoft Academic Search

    Irzyniec; J. Klimczak; S. Michalowski

    1995-01-01

    The effect of drying temperature of the black currant juice on the retention of vitamin C and anthocyanins content as well as drying kinetics in the freeze-dried process, has been studied. Non clarified, black currant juice was freered on plates in the layer of 15 mm thick until the temperature of -30 °C in the thermal center of sample has

  5. High pressure freezing and thawing of foods: a review

    Microsoft Academic Search

    A LeBail; D Chevalier; D. M Mussa; M Ghoul

    2002-01-01

    The phase diagram of water shows that the melting temperature of water decreases with pressure down to ?21°C at 210 MPa while the opposite effect is observed above this pressure. This phenomenon allows the achievement of rapid freezing and thawing of foods that mainly contain water. In addition, pressure-assisted thawing has the advantage of inducing a reduction in drip loss

  6. A molecular theory for the freezing of hard spheres

    Microsoft Academic Search

    A. D. J. Haymet

    1983-01-01

    Using statisical mechanics and a series of well-defined approximations we present a calculation of the equilibrium liquid to solid transition for hard spheres. No computer simulation results are used. The transition is located from structural information about the liquid using a first-principles order parameter theory of freezing. The order parameters are the coefficients of a Fourier expansion of the spatially

  7. VOLATILE EMISSIONS OF NAVEL ORANGES AS PREDICTORS OF FREEZE DAMAGE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Volative emissions of navel orange fruit were evaluated as a means for predicting and gauging freeze damage. The fruit were subjected to -5C or -7C treatments in a laboratory freezer for various time periods of 2 to 9.5 hours, and stored at 23C for 1, 2, or 7 days, after which the emission of volat...

  8. Carbohydrates in oat tillers and their relationship to freezing survival

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In grasses the crown is a complex organ from which tillers arise and eventually produce the flower-bearing structure where seeds are eventually born. We have observed that in oats not all tillers have the same ability to survive freezing and while an entire plant may be produced from one surviving ...

  9. IN FAVOUR OF FREEZING EGGS FOR NON-MEDICAL REASONS

    Microsoft Academic Search

    IMOGEN GOOLD; JULIAN SAVULESCU

    2009-01-01

    ABSTRACTThis article explores the social benefits and moral arguments in favour of women and couples freezing eggs and embryos for social reasons. Social IVF promotes equal participation by women in employment; it offers women more time to choose a partner; it provides better opportunities for the child as it allows couples more time to become financially stable; it may reduce

  10. How Circulation of Water Affects Freezing in Ponds

    ERIC Educational Resources Information Center

    Moreau, Theresa; Lamontagne, Robert; Letzring, Daniel

    2007-01-01

    One means of preventing the top of a pond from freezing involves running a circulating pump near the bottom to agitate the surface and expose it to air throughout the winter months. This phenomenon is similar to that of the flowing of streams in subzero temperatures and to the running of taps to prevent pipe bursts in winter. All of these cases…

  11. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pumped water to irrigate their plants for protection from the cold temperatures. The sinkholes destroyed homes, roads and se...

  12. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    The entire root perimeter of this tree collapsed in response to subsidence activity. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pumped water to irrigate their plants for pr...

  13. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    Sinkholes damage roadways and require constant maintenance for road safety. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pumped water to irrigate their plants for protection ...

  14. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    Cracks shown here in the exterior and supporting structures of this home are indicative of subsidence damage associated with sinkhole activity. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting l...

  15. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    A sinkhole formed in a roadway caused traffic to detour around it while it is filled in, stabilized and repaved. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pumped water to...

  16. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    Sinkholes affect roadway safety and require constant maintenance and monitoring. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pumped water to irrigate their plants for p...

  17. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    A section of a strawberry field that was destroyed by a sinkhole and filled in, as is done with many sinkholes if possible. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows as farmers pump...

  18. Sinkholes in West-central Florida, Freeze Event of 2010

    USGS Multimedia Gallery

    Sinkholes affect structures as well as many types of supporting infrastructure such as buried utilities lines seen here. More than 110 sinkholes formed in the Dover area of Florida during a freeze event in January 2010. Ground water levels dropped to record-setting lows ...

  19. Freezing tolerance of winter wheat plants frozen in saturated soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Winter wheat is sown in the autumn and harvested the following summer, necessitating the ability to survive subfreezing temperatures for several months. Autumn months in wheat–growing regions typically experience significant rainfall. Hence, the wheat plants usually are exposed to freezing temperat...

  20. Fructan mobilization during recovery from freezing in winter oat crowns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fructan, which is a carbohydrate polymer similar to starch but based on fructose, is an important cryoprotectant in plants. But how the plant uses this carbohydrate to improve freezing resistance is controversial. We are reporting here results of the first analysis of fructan changes that occur du...

  1. Freeze Dried Zn-DNA: Magnetism Dominated by Water Molecules

    NASA Astrophysics Data System (ADS)

    Kumeta, Tsubasa; Sakamoto, Hirokazu; Mizoguchi, Kenji

    2014-08-01

    Magnetic behaviors in freeze dried DNA complexes with Zn ions (FD-Zn-DNA) are reported. Dehydrated Zn-DNA was prepared from pure Zn-DNA by a freeze drying procedure. Complete dehydration of Zn-DNA by the freeze drying induces an irreversible structural change and produces one ? electron spin at each base pair of FD-Zn-DNA. Magnetic behaviors essential to the ? electron spins are markedly changed by introducing water molecules in FD-Zn-DNA. In the dehydrated FD-Zn-DNA, the paramagnetism of the ? spin system is totally suppressed because of the spin singlet ground state caused by the strong off-site Coulomb repulsion V, which is larger than the on-site Coulomb repulsion U. In contrast, the hydrated FD-Zn-DNA carries large Pauli-like temperature-independent paramagnetism, whose magnitude corresponds to the ?-band width of ?0.24 eV. A possible mechanism of the ? electron spin creation is proposed. As a subsidiary effect of the freeze drying procedure, the nonlinear paramagnetism saturating below 0.1 T is observed in both DNA and Zn-DNA. The nonlinear paramagnetism disappears after the hydration of the sample. On the basis of the magnitude of the saturation magnetization, it is suggested that the origin of the nonlinear paramagnetism is the magnetic impurities in DNA.

  2. Safe high-pressure freezing of infectious micro-organisms.

    PubMed

    Vanhecke, D; Zuber, B; Brugger, S D; Studer, D

    2012-05-01

    We describe how high-pressure freezing of infectious biological material can safely be accomplished with the help of membrane carriers. The method described is easy to perform; however, careful manipulations are required. Existing safety regulations must still be followed. However, the procedure reduces the risk of dissemination of infectious material. PMID:22364646

  3. Computational analysis of fluid dynamics in pharmaceutical freeze-drying.

    PubMed

    Alexeenko, Alina A; Ganguly, Arnab; Nail, Steven L

    2009-09-01

    Analysis of water vapor flows encountered in pharmaceutical freeze-drying systems, laboratory-scale and industrial, is presented based on the computational fluid dynamics (CFD) techniques. The flows under continuum gas conditions are analyzed using the solution of the Navier-Stokes equations whereas the rarefied flow solutions are obtained by the direct simulation Monte Carlo (DSMC) method for the Boltzmann equation. Examples of application of CFD techniques to laboratory-scale and industrial scale freeze-drying processes are discussed with an emphasis on the utility of CFD for improvement of design and experimental characterization of pharmaceutical freeze-drying hardware and processes. The current article presents a two-dimensional simulation of a laboratory scale dryer with an emphasis on the importance of drying conditions and hardware design on process control and a three-dimensional simulation of an industrial dryer containing a comparison of the obtained results with analytical viscous flow solutions. It was found that the presence of clean in place (CIP)/sterilize in place (SIP) piping in the duct lead to significant changes in the flow field characteristics. The simulation results for vapor flow rates in an industrial freeze-dryer have been compared to tunable diode laser absorption spectroscopy (TDLAS) and gravimetric measurements. PMID:19569225

  4. The morphology of freeze-dried rubidium chloride powder

    SciTech Connect

    Panitz, J.K.G.; Voigt, J.A.; Greulich, F.A.; Carr, M.J.; Eatough, M.O.

    1989-01-01

    We have formed powders of a strongly ionic compound, RbCl by freeze-drying. Stock solutions varying from very low concentrations with 4 gm RbCl reagent dissolved in 100 cc water, to saturated solutions with 80 gm reagent in 100 cc water sprayed into isopentane at /minus/160/degree/C. The droplet size in the spray was varied from relatively large 4-mm diameter droplets to extremely small droplets in an aerosol spray. It was determined that both the concentration of the stock solution and the droplet size affect the average size and the size distribution of the primary particles formed and the way in which these primary particles are bonded together. Unlike the powders of many less ionic compounds that are produced by freeze-drying, the primary particles in these RbCl powders are crystalline rather than amorphous. Analysis with an x-ray diffractometer with a cold stage indicates that crystallization occurs during the freezing cycle rather than during the sublimation period of the freeze-drying process. 11 refs., 8 figs.

  5. FREEZING SWINE EMBRYOS: DO SUCCESS RATES DIFFER BETWEEN BREEDS?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successful freezing, or cryopreservation, of embryos could greatly impact the pork industry, serving as a tool for conservation of valuable germplasm and enhancing biosecurity for transfer of genetic material. Pig embryos are very sensitive to cooling and few reports have shown successful developmen...

  6. Prototype capacitor produced by freeze tape-casting

    Microsoft Academic Search

    E. P. Gorzkowski; M.-J. Pan; B. A. Bender

    2011-01-01

    In previous research freeze casting was used to construct ceramic-polymer composites in which the two phases are arranged in an electrically parallel configuration. By doing so, the composites exhibit dielectric constant (K) up to two orders of magnitude higher than that of composites with ceramic particles randomly dispersed in a polymer matrix. This technique has been successful with both an

  7. Cash Freeze for E-Rate Hits Schools

    ERIC Educational Resources Information Center

    Borja, Rhea R.

    2004-01-01

    A freeze on $3.28 billion in requests for aid under the federal E-rate program has left hundreds of school districts scrambling to pay for their technology needs--and, in some cases, crippled classroom instruction. The E-rate program, which has disbursed more than $8 billion since its inception in 1997, helps link public and private schools as…

  8. COMBINED REVERSE OSMOSIS AND FREEZE CONCENTRATION OF BLEACH PLANT EFFLUENTS

    EPA Science Inventory

    Reverse osmosis (RO) and freeze concentration (FC) were evaluated at three different pulp and paper mills as tools for concentrating bleach plant effluents. By these concentration processes, the feed effluent was divided into two streams. The clean water stream approached drinkin...

  9. Hygienic Conditions of Materials for Freezing Bovine Semen

    Microsoft Academic Search

    P. Marinov; H. Bohnel

    1974-01-01

    Dilutor Laiciphos 231 and French packaging material for frozen semen were investigated for bacterial contami- nation in various stages of preparation for deep freezing. Antibacterial proper- ties of dilutor containing penicillin and streptomycin were also examined on bacteria from semen and egg yolk. Laiciphos 231 contained microorgan- isms whose number varied irt different lots and envelopes. During storage of solution,

  10. Frozen bread dough: Effects of freezing storage and dough improvers

    Microsoft Academic Search

    Vania Octaviani Selomulyo; Weibiao Zhou

    2007-01-01

    This review focuses on the effects of freezing storage on the microstructure and baking performance of frozen doughs, and provides an overview of the activities of dough improvers, including emulsifiers, hydrocolloids and other improvers used in frozen dough applications. The overall quality of bread baked from frozen dough deteriorates as the storage of the dough at sub-zero temperatures increases due

  11. Human Platelets Loaded with Trehalose Survive Freeze-Drying

    Microsoft Academic Search

    Willem F. Wolkers; Naomi J. Walker; Fern Tablin; John H. Crowe

    2001-01-01

    Human blood platelets are stored in blood banks for 5 days, after which they are discarded, by federal regulation. This short lifetime has led to a chronic shortage of platelets, a problem that is particularly acute in immunosuppressed patients, such as those with AIDS. We report here that platelets can be preserved by freeze-drying them with trehalose, a sugar found

  12. MELTING, FREEZING, DIFFUSION, AND COALESCENCE OF GOLD NANOCLUSTERS

    E-print Network

    Lewis, Laurent J.

    molecular­dynamics study of the coalescence of gold nanoclusters within the framework of the embedded­atom properties of a 249­atom gold cluster on nickel surfaces. INTRODUCTION Nanometer­size clusters have receivedMELTING, FREEZING, DIFFUSION, AND COALESCENCE OF GOLD NANOCLUSTERS LAURENT J. LEWIS[a] D

  13. FREEZING WATER CLEANING A POSSIBLE IMPROVEMENT IN SRF CAVITY RINSING*

    E-print Network

    ERL 10-3 FREEZING WATER CLEANING ­ A POSSIBLE IMPROVEMENT IN SRF CAVITY RINSING* Valery Shemelin rinsing (HPR) is a necessary stage of SRF cavity preparation [1] because it provides cleaner, field the traditional HPR are at hand in any SRF lab, a simple cooling down of the cavity before rinsing can

  14. Combined Electrohydrodynamic (EHD) and Vacuum Freeze Drying of Sea Cucumber

    Microsoft Academic Search

    Yaxiang Bai; Yaxin Yang; Qiang Huang

    2012-01-01

    A combination of electrohydrodynamic drying (EHD) and vacuum freeze drying (FD) is examined as an improved method for dehydrating sea cucumbers. The energy consumption, shrinkage and rehydration ratio, protein content, and sensory properties, such as the color and trimness, of the dried product in the EHD–FD method are measured. Compared with FD, the combined process consumes less drying time and

  15. Water’s size-dependent freezing to cubic ice

    Microsoft Academic Search

    G. P. Johari

    2005-01-01

    Water has been occasionally found to freeze to cubic ice. To investigate this occurrence thermodynamically, we use the known enthalpy and interfacial energy of hexagonal and cubic ices and calculate a critical radius rc of ?15 nm for a water droplet and a critical thickness ?c of ?10 nm for water’s flat film. Accordingly, water droplets smaller than 15 nm

  16. Water's size-dependent freezing to cubic ice

    Microsoft Academic Search

    G. P. Johari

    2005-01-01

    Water has been occasionally found to freeze to cubic ice. To investigate this occurrence thermodynamically, we use the known enthalpy and interfacial energy of hexagonal and cubic ices and calculate a critical radius rc of ~15 nm for a water droplet and a critical thickness deltac of ~10 nm for water's flat film. Accordingly, water droplets smaller than 15 nm

  17. Freeze Drying of Fruits and Vegetables: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Noble, Richard D.

    1979-01-01

    Describes a laboratory experiment for freeze-drying fruits and vegetables which aims to expose college students to the principles of drying and simultaneous heat and mass transfer. The experimental apparatus, procedure of the experiment, and data analysis are also included. (HM)

  18. ANNAGNPS: ACCOUNTING FOR SNOWPACK, SNOWMELT, FREEZING AND THAWING OF SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The watershed model, AnnAGNPS (Annualized AGricultural Non-Point Source Pollution model) has been enhanced by incorporating winter climate algorithms that account for frozen soil conditions. The model includes snowpack accumulation and melt, and the freeze/thaw process in the soil. Three major imp...

  19. Freezing of parallel hard cubes with rounded edges.

    PubMed

    Marechal, Matthieu; Zimmermann, Urs; Löwen, Hartmut

    2012-04-14

    The freezing transition in a classical three-dimensional system of rounded hard cubes with fixed, equal orientations is studied by computer simulation and fundamental-measure density functional theory. By switching the rounding parameter s from zero to one, one can smoothly interpolate between cubes with sharp edges and hard spheres. The equilibrium phase diagram of rounded parallel hard cubes is computed as a function of their volume fraction and the rounding parameter s. The second order freezing transition known for oriented cubes at s = 0 is found to be persistent up to s = 0.65. The fluid freezes into a simple-cubic crystal which exhibits a large vacancy concentration. Upon a further increase of s, the continuous freezing is replaced by a first-order transition into either a sheared simple cubic lattice or a deformed face-centered cubic lattice with two possible unit cells: body-centered orthorhombic or base-centered monoclinic. In principle, a system of parallel cubes could be realized in experiments on colloids using advanced synthesis techniques and a combination of external fields. PMID:22502532

  20. De-aggregated reliability analysis of freezing rain hazard

    Microsoft Academic Search

    Reza Erfani

    2010-01-01

    This work addresses issues for improving the estimation of the recurrence rate and the distribution in severity of extreme ice events in the Montreal area, which is required in order to determine design criteria for structures such as electric transmission lines. Some of the limitations of current methods for studying extreme freezing rain events are due to the relatively short

  1. Effect of Freezing on Fossomatic Cell Counting in Ewe Milk

    Microsoft Academic Search

    J. R. Martínez; C. Gonzalo; J. A. Carriedo; F. San Primitivo

    2003-01-01

    Using the Fossomatic method, a total of 10,072 ana- lytical somatic cell count (SCC) observations were car- ried out on 4760 aliquots taken from 70 individual ewe milk samples with the objective of studying whether freezing showed significant differences of SCC in com- parison with refrigeration, according to different ana- lytical conditions. These conditions were four preserva- tion procedures (without

  2. Effects of freezing on thermoluminescence in various plant species.

    PubMed

    Janda, Tibor; Szalai, Gabriella; Papp, Nóra; Pál, Magda; Páldi, Emil

    2004-01-01

    The aim of this study was to monitor the effect of sudden frost on the photosynthetic electron transport chain in the leaves of various plant species using the thermoluminescence (TL) technique. A short period of freezing caused a decrease in the afterglow (AG) band in young maize leaves, with a slight upshift in the maximum temperature. The B band induced by far-red (FR) illumination started to decrease at a significantly lower temperature. The flash-induced B band also showed a substantial decrease in intensity after short preliminary freezing. In contrast to other species, for which there was always a well-detectable TL signal even after relatively drastic freezing, there was no TL signal at all in geranium below a threshold temperature. The behavior of the FR-induced TL curve in cucumber plants was a mixture of that found in wheat or pea, on the one hand, and maize, on the other: the AG band gradually decreased with decreasing temperature and finally totally disappeared, as in maize. The FR-induced B band showed an upshift after freezing. These results suggest that AG is a normal component of TL bands induced not only by FR, but also by single turnover flash. PMID:15323581

  3. All-orders infrared freezing of observables in perturbative QCD

    E-print Network

    D. M. Howe; C. J. Maxwell

    2004-04-02

    We consider a Borel sum definition of all-orders perturbation theory for Minkowskian QCD observables such as the R(e+e-) ratio, and show that both this perturbative component and the additional non-perturbative Operator Product Expansion (OPE) component can remain separately well-defined for all values of energy sqrt(s), with the perturbative component dominating as s-->infinity, and with both components contributing as s-->0. In the infrared s-->0 limit the perturbative correction to the parton model result for R(e+e-) has an all-orders perturbation theory component which smoothly freezes to the value R(0)=2/b, where b=(33-2Nf)/6 is the first QCD beta-function coefficient with Nf flavours of massless quarks. For freezing one requires Nf<9. The freezing behaviour is manifested by the ``contour-improved'' or ``Analytic Perturbation Theory'' (APT), in which an infinite subset of analytical continuation terms are resummed to all-orders. We show that for the Euclidean Adler-D function, D(Q^2), the perturbative component remains defined into the infrared provided that ALL the renormalon singularities care taken into account, but no analogue of the APT reorganisation of perturbation theory is possible. We perform phenomenological comparisons of suitably smeared low-energy data for the R(e+e-) ratio, with the perturbative freezing perdictions, and find good agreement.

  4. GENERAL VIEW OF SHARP FREEZE ROOM ON LEVEL 2; LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GENERAL VIEW OF SHARP FREEZE ROOM ON LEVEL 2; LOOKING WEST; PIPES ON CEILING CARRIED COMPRESSED AMMONIA; NOTE NONBEARING GLAZED TILE WALLS BETWEEN COLUMNS; FLOORS ARE BRICK - Rath Packing Company, Cooler Building, Sycamore Street between Elm & Eighteenth Streets, Waterloo, Black Hawk County, IA

  5. Horizontal Inequity and Vertical Redistribution

    Microsoft Academic Search

    Peter J. Lambert; Xavier Ramos

    1997-01-01

    Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by

  6. The TEXT upgrade vertical interferometer

    SciTech Connect

    Hallock, G.A.; Gartman, M.L.; Li, W.; Chiang, K.; Shin, S.; Castles, R.L.; Chatterjee, R.; Rahman, A.S. (The University of Texas at Austin, Austin, Texas 78712 (United States))

    1992-10-01

    A far-infrared interferometer has been installed on TEXT upgrade to obtain electron density profiles. The primary system views the plasma vertically through a set of large (60-cm radial{times}7.62-cm toroidal) diagnostic ports. A 1-cm channel spacing (59 channels total) and fast electronic time response is used, to provide high resolution for radial profiles and perturbation experiments. Initial operation of the vertical system was obtained late in 1991, with six operating channels.

  7. The Metallicity Gradient of the Old Galactic Bulge Population

    NASA Astrophysics Data System (ADS)

    Sans Fuentes, Sara Alejandra; De Ridder, Joris

    Understanding the structure, formation and evolution of the Galactic Bulge requires the proper determination of spatial metallicity gradients in both the radial and vertical directions. RR Lyrae pulsators, known to be excellent distance indicators, may hold the key to determining these gradients. Jurcsik and Kovacs (A&A 312:111, 1996) has shown that RR Lyrae light curves and the phase difference of their Fourier decomposition, ? 31, can be used to estimate photometric metallicities. The existence of galactic bulge metallicity gradients is a currently debated topic that would help pinpoint the Galaxy's formation and evolution. A recent study of the OGLE-III Galactic Bulge RR Lyrae Population by Pietrukowicz et al. (ApJ 750:169, 2012) suggests that the spatial distribution is uniform. We investigate how small a gradient would be detectable within the current S/N levels of the present data set, given the random and systematic errors associated with the derivation of a photometric metallicity versus spatial position relationship.

  8. An Evaluation of Supercritical Drying and PEG/Freeze Drying of Waterlogged

    E-print Network

    Blanchette, Robert A.

    An Evaluation of Supercritical Drying and PEG/Freeze Drying of Waterlogged Archaeological Wood polyethylene glycol (PEG)/freeze drying method. Previous studies have shown supercritical drying and grouped into three treatment sets: one for air drying, one for PEG/freeze drying, and the other

  9. NATURE OF FREE RADICALS IN FREEZE-DRIED FISHERY PRODUCTS AND OTHER LIPID-PROTEIN SYSTEMS

    E-print Network

    NATURE OF FREE RADICALS IN FREEZE-DRIED FISHERY PRODUCTS AND OTHER LIPID-PROTEIN SYSTEMS WILLIAM T radicals which are produced during lipid peroxidation in freeze-dried lipid-protein systems which is known to be mostly free radical in nature. Ac- cordingly, such materials as freeze-dried fish

  10. Mehak Mehta December 13th Controlling the physical form of mannitol in freeze-dried systems

    E-print Network

    Thomas, David D.

    Mehak Mehta December 13th 2012 Controlling the physical form of mannitol in freeze-dried systems Mannitol is a commonly used crystalline bulking agent in freeze-dried formulations. In the anhydrous state formation in freeze-dried products. Our goal was to develop a comprehensive understanding of the factors

  11. Beginning of exocytosis captured by rapid-freezing of Limulus amebocytes

    Microsoft Academic Search

    R. L. Ornberg; T. S. REESE

    1981-01-01

    Structuralchanges underlying exocytosis evoked by the application of endotoxin to Limulus amebocytes were studied at the levelof detailafforded by freeze-fractureand freeze- substitution techniques combined with the time resolution of direct rapid-freezing.The results with amebocytes prepared in this manner differed from those with other secretory cells prepared by conventional means . Exocytosis begins within seconds of endotoxin treatment when the plasmalemma

  12. Optimal freezing and thawing for the survival of periphheral nerves in severed rabbit limbs

    PubMed Central

    Zhu, Zexing; Qiao, Lin; Zhao, Yandong; Zhang, Shuming

    2014-01-01

    This study aimed to investigate the optimal freezing and thawing procedures for the survival of peripheral nerves in severed rabbit limbs. Twenty New Zealand White rabbits were randomized into four groups: normal control, slow-freezing fast-thawing, slow-freezing slow-thawing, fast-freezing fast-thawing, with five animals in each group. The hind limbs of the rabbits were severed at 1 cm above the knee joint. The severed limbs were cryopreserved with various freezing and thawing procedures. The sciatic nerves were harvested and trypsinized into single nerve fibers for morphological evaluation. The cell viability of the nerve fibers was examined by staining with Calcein-AM and propidium iodide. The fluorescent intensity of the nerve fibers was measured with a laser scanning confocal microscope. The morphology of the nerve fibers in the slow-freezing fast-thawing group was very similar with that of the normal control group, with only mild demyelination. The slow-freezing fast-thawing group and slow-freezing slow-thawing group showed severely damaged nerve fibers. The fluorescent intensities of the nerve fibers was significantly different among the four groups, with a decreasing order of normal control, slow-freezing fast-thawing, slow-freezing slow-thawing, and fast-freezing fast-thawing (P < 0.05). Of the various cryopreservative procedures, slow-freezing fast thawing has the minimal effects on the survival of nerve fibers in severed rabbit limbs. PMID:25550819

  13. Comparative studies on tolerance of Medicago truncatula and Medicago falcata to freezing

    Microsoft Academic Search

    Li-Li Zhang; Min-Gui Zhao; Qiu-Ying Tian; Wen-Hao Zhang

    Medicago falcata is a legume species that exhibits great capacity of tolerance to abiotic stresses. To elucidate the mechanism underlying\\u000a tolerance of M. falcata to freezing, we compared the characteristics of M. falcata in response to cold acclimation and freezing with those of the legume model plant Medicago truncatula. M. falcata seedlings were more tolerant to freezing than M. truncatula,

  14. Structural properties of materials created through freeze casting Stephen A. Barr a

    E-print Network

    Mohseni, Hooman

    Structural properties of materials created through freeze casting Stephen A. Barr a , Erik Luijten; Porous material; Molecular dynamics simulations; Freeze casting 1. Introduction Strong, lightweight and biomedical implants. One method to create such materials is freeze casting, in which an aqueous suspension

  15. Optimal freezing and thawing for the survival of periphheral nerves in severed rabbit limbs.

    PubMed

    Zhu, Zexing; Qiao, Lin; Zhao, Yandong; Zhang, Shuming

    2014-01-01

    This study aimed to investigate the optimal freezing and thawing procedures for the survival of peripheral nerves in severed rabbit limbs. Twenty New Zealand White rabbits were randomized into four groups: normal control, slow-freezing fast-thawing, slow-freezing slow-thawing, fast-freezing fast-thawing, with five animals in each group. The hind limbs of the rabbits were severed at 1 cm above the knee joint. The severed limbs were cryopreserved with various freezing and thawing procedures. The sciatic nerves were harvested and trypsinized into single nerve fibers for morphological evaluation. The cell viability of the nerve fibers was examined by staining with Calcein-AM and propidium iodide. The fluorescent intensity of the nerve fibers was measured with a laser scanning confocal microscope. The morphology of the nerve fibers in the slow-freezing fast-thawing group was very similar with that of the normal control group, with only mild demyelination. The slow-freezing fast-thawing group and slow-freezing slow-thawing group showed severely damaged nerve fibers. The fluorescent intensities of the nerve fibers was significantly different among the four groups, with a decreasing order of normal control, slow-freezing fast-thawing, slow-freezing slow-thawing, and fast-freezing fast-thawing (P < 0.05). Of the various cryopreservative procedures, slow-freezing fast thawing has the minimal effects on the survival of nerve fibers in severed rabbit limbs. PMID:25550819

  16. Frozen storage of ram semen I. Processing, freezing, thawing and fertility after cervical insemination

    Microsoft Academic Search

    S. Salamon; W. M. C. Maxwell

    1995-01-01

    Research up to 1993 is reviewed. Various methods for processing, freezing and thawing of semen have been elaborated and their effect on survival and fertility of spermatozoa have been examined in vitro or in fertility tests. Diluents initially used for freezing bull semen had their limitations and were modified or replaced by new media. The freezing diluents investigated included citrate-sugar-,

  17. Remote sensing of changes in near surface freeze and thaw timing from 1988 to 2006

    Microsoft Academic Search

    N. V. Smith-Downey; S. S. Saatchi; J. T. Randerson

    2007-01-01

    We developed a technique to detect the date of near surface soil freeze and thaw using passive microwave satellite data from the SSM\\/I instrument. The difference between the 37 and 19 GHz channels is used as an indicator of soil freeze state. We generated a continuous record of freeze and thaw dates from 1988 to 2006 for all land areas

  18. Gelatin-Filtered Consomme: A Practical Demonstration of the Freezing and Thawing Processes

    ERIC Educational Resources Information Center

    Lahne, Jacob B.; Schmidt, Shelly J.

    2010-01-01

    Freezing is a key food processing and preservation technique widely used in the food industry. Application of best freezing and storage practices extends the shelf-life of foods for several months, while retaining much of the original quality of the fresh food. During freezing, as well as its counterpart process, thawing, a number of critical…

  19. Transcript Differences Associated With Non-Acclimated Freezing Tolerance in Two Barley (Hordeum Vulgare L.) Cultivars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Barley periodically suffers from late spring freezes in area throughout the world, with significant losses to yield. To better understand the response of barley to spring freezes, we examined the response of Dicktoo and Keunal barley varieties in their jointing stage to non-acclimated freezing (NAF...

  20. Reduction of microbial density level in wastewater activated sludge via freezing and thawing

    Microsoft Academic Search

    C. P Chu; W. C Feng; Bea-Ven Chang; C. H Chou; D. J Lee

    1999-01-01

    This note has employed a freeze\\/thaw method for treating activated sludge, with especial attention for the reduction capability of microbial density. The sludge dewaterability is most enhanced if the growing ice front could reject the flocs. On the other hand, the microbial density level heavily relies on the bacterial species and the freezing speed. In this specific case, the freeze\\/thaw

  1. Method of freezing living cells and tissues with improved subsequent survival

    DOEpatents

    Senkan, Selim M. (Oak Ridge, TN); Hirsch, Gerald P. (Oak Ridge, TN)

    1980-01-01

    This invention relates to an improved method for freezing red blood cells, ther living cells, or tissues with improved subsequent survival, wherein constant-volume freezing is utilized that results in significantly improved survival compared with constant-pressure freezing; optimization is attainable through the use of different vessel geometries, cooling baths and warming baths, and sample concentrations.

  2. Vertical Profiles in NO3 and N2O5

    NASA Astrophysics Data System (ADS)

    Brown, S. S.; Osthoff, H. D.; Dube, W. P.; Ryerson, T. B.; de Gouw, J. A.; Warneke, C.; Stutz, J.; Fehsenfeld, F. C.; Ravishankara, A. R.

    2005-12-01

    The nocturnal formation and subsequent reactions of NO3 (the nitrate radical) and N2O5 (dinitrogen pentoxide) are an important component of atmospheric nitrogen oxide chemistry. However, relatively little is known about their spatial distribution and variability, mainly because in-situ instruments for measurement of their ambient concentrations have only recently become available. This presentation will show the vertical distributions of NO3 and N2O5 (and related compounds) from two recent field campaigns; measurements from the NOAA P3 aircraft over the Northeast United States and the North Atlantic during the summer of 2004, and from a tower site near Boulder, CO in the fall of 2004. The aircraft data show vertical distributions from 0-3.5 km, while those from the tower site cover the range from 0-300 m with high vertical resolution (< 1 m). A common feature in both data sets is the large increase in NO3 and N2O5 mixing ratios measured aloft compared those at the surface, even in the absence of similar vertical variations in NOx and ozone. While there are varying reasons for these gradients, it is clear that nocturnal nitrogen oxide chemistry aloft leads to different evolution of NOx and VOC than that at the surface, an observation that will influence the understanding of the lifetime, transport and distribution of atmospheric NOx.

  3. Underground structure detection by surface magnetic gradient measurements

    SciTech Connect

    Kelly, R. E. (Robert E.)

    2001-01-01

    This problem involves magnetic induction methods to locate and determine the depth of a subsurface line source of magnetic field. The origin of the field may be self-generated or induced by a surface transmitter. The experimental method requires measuring the horizontal gradient of either the vertical or horizontal component of the field rather than the field itself so as to increase signal to noise ratio. A mathematical outline is presented and experimental results are discussed. Keywords: underground detection, electromagnetic theory, magnetic induction, tunnels, underground structures, imaging

  4. Proteomic analyses reveal differences in cold acclimation mechanisms in freezing-tolerant and freezing-sensitive cultivars of alfalfa

    PubMed Central

    Chen, Jing; Han, Guiqing; Shang, Chen; Li, Jikai; Zhang, Hailing; Liu, Fengqi; Wang, Jianli; Liu, Huiying; Zhang, Yuexue

    2015-01-01

    Cold acclimation in alfalfa (Medicago sativa L.) plays a crucial role in cold tolerance to harsh winters. To examine the cold acclimation mechanisms in freezing-tolerant alfalfa (ZD) and freezing-sensitive alfalfa (W5), holoproteins, and low-abundance proteins (after the removal of RuBisCO) from leaves were extracted to analyze differences at the protein level. A total of 84 spots were selected, and 67 spots were identified. Of these, the abundance of 49 spots and 24 spots in ZD and W5, respectively, were altered during adaptation to chilling stress. Proteomic results revealed that proteins involved in photosynthesis, protein metabolism, energy metabolism, stress and redox and other proteins were mobilized in adaptation to chilling stress. In ZD, a greater number of changes were observed in proteins, and autologous metabolism and biosynthesis were slowed in response to chilling stress, thereby reducing consumption, allowing for homeostasis. The capability for protein folding and protein biosynthesis in W5 was enhanced, which allows protection against chilling stress. The ability to perceive low temperatures was more sensitive in freezing-tolerant alfalfa compared to freezing-sensitive alfalfa. This proteomics study provides new insights into the cold acclimation mechanism in alfalfa. PMID:25774161

  5. Immersion freezing of different kinds of combustion ashes

    NASA Astrophysics Data System (ADS)

    Augustin-Bauditz, Stefanie; Grawe, Sarah; Hellner, Lisa; Wex, Heike; Pettersson, Jan B. C.; Stratmann, Frank

    2015-04-01

    Ice particles in the atmosphere influence both, weather and climate. Therefore it is important to know which kind of particles can act as ice nucleating particles (INP) under atmospheric conditions. In the last years, a lot of effort has been made to investigate the freezing abilities of natural INPs such as dusts and biological particles (Murray et al., 2012, Hoose and Möhler, 2012). However, there are only a few investigations concerning the ice nucleation ability of combustion ashes, which are the remains of fossil fuel and wood combustion and thus a possible source for anthropogenic INPs. Ash particles have similar compositions as mineral dust particles. However, the actual contribution of combustion ash particles to the atmospheric ice nucleation is rather unclear. A recent study by Umo et al. (2014) showed that combustion ashes could have a significant impact on the ice nucleation in clouds and thus should be the focus of further research. Ash particles can be lifted to the atmosphere by wind (bottom ashes) or directly during the combustion process (fly ashes). In the present study we investigated the freezing behavior of bottom ash particles which originated from wood as well as from coal. Additionally we investigated particles from fly ash from a coal-fired power plant. Particles were generated by dry dispersion and afterwards size selected with a differential mobility analyzer (DMA). The immersion freezing ability of the different ash particles was quantified utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS, Hartmann et al., 2011), where exactly one size segregated ash particle is immersed in a droplet. We found significant differences between the freezing abilities of the different ash types. Particles from wood bottom ashes initiate freezing at rather low temperatures near the homogenous freezing point (around -36°C). Particles from coal bottom ashes show significant higher ice nucleation abilities than the wood bottom ash, with observed freezing temperatures similar to those of clay minerals (around -30°C). The particles from the fly ash showed the best freezing ability, which was significantly higher than the freezing ability of the clay minerals but still not as good as that of K-feldspar. Hartmann, S., Niedermeier, D., Voigtländer, J., Clauss, T., Shaw, R. A., Wex, H., Kiselev, A., and Stratmann, F.: Atmos. Chem. Phys., 11, 1753-1767, doi:10.5194/acp-11-1753-2011, 2011. Hoose, C. and O. Möhler, Atmos. Chem. Phys., 12, 9817-9854, 2012. Murray, B. J., O'Sullivan, D., Atkinson, J. D. and Webb, M. E., Chem. Soc. Rev., 41, 6519-6554, 2012. Umo N. S., Murray B. J., Baeza-Romero M. T., Jones J. M., Lea-Langton A. R., Malkin T. L., O'Sullivan D., Plane J. M. C. and Williams A., Atmos. Chem. Phys. Discuss., 14, 28845-28883, 2014

  6. Analysis and Improvement of Policy Gradient Estimation

    E-print Network

    Sugiyama, Masashi

    Analysis and Improvement of Policy Gradient Estimation Tingting Zhao, Hirotaka Hachiya, Gang Niu gradient methods. We first prove that the vari- ance of gradient estimates in the PGPE (policy gradients with parameter-based exploration) method is smaller than that of the classical REINFORCE method under a mild

  7. The freeze-out properties of hyperons in a microscopic transport model

    E-print Network

    Zhenglian Xie; Pingzhi Ning; Steffen A. Bass

    2009-11-23

    The excitation function of freeze-out time, average freeze-out temperature and freeze-out energy density of (multi-) strange baryons created in relativistic heavy-ion collisions is investigated in the framework of a microscopic transport model. We find that the Omega on average freezes out earlier than the nucleon, Xi and Lambda. The average freeze-out temperature and energy density as well as the spread between the different baryonicstates increase monotonously with increasing beam energy and should approach a universal value in the case of a hadronizing Quark-Gluon-Plasma.

  8. Vertical saccades in dyslexic children.

    PubMed

    Tiadi, Aimé; Seassau, Magali; Bui-Quoc, Emmanuel; Gerard, Christophe-Loïc; Bucci, Maria Pia

    2014-11-01

    Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering. PMID:25151607

  9. Relationship between ocean velocity and motionally induced electrical signals: 1. In the presence of horizontal velocity gradients

    Microsoft Academic Search

    Zoltan B. Szuts

    2010-01-01

    Motionally induced electric fields and electric currents in the ocean depend to first order solely on the vertical dimension. We investigate the significance of two-dimensional (2-D) perturbations that arise in the presence of horizontal velocity gradients. The full electric response is calculated for two schematic geometries that contain horizontal velocity gradients, have a two-layer ocean with a layer of sediment

  10. Method of total field reconstruction from aeromagnetic gradients data

    NASA Astrophysics Data System (ADS)

    Li, H.; Yu, H.

    2013-12-01

    The total field reconstructed from the measured gradient data is diurnal free. It is important approach to eliminate diurnal for some survey area that is not possible to have a base-station magnetometer. In this work, method of total field reconstruction from gradients data in frequency domain was investigated. Transformation of potential field by fast Fourier transform technique in frequency domain is common used, the equations describing these geophysical problems are often much simpler when expressed in frequency terms, and the computation speed is very fast, this is very important for large dataset of aeromagnetic survey. The widely used fast Fourier transform technique, applied to total field reconstruction has a major difficulty which is those expressions of transform operators are undefined when u or v equal to zero or u and v are simultaneously equal to zero (u is the frequency in x-direction and v is the frequency in y-direction), the operators can not be sampled at these frequencies. Consequently, the traditional Fourier methods are not applicable for these singular points. Shift sampling theory proposed by Chai etal is employed for resolving this problem, and the method is illustrated by application to theoretical and field data. The performance of the method was assessed using theoretical magnetic total field and gradient anomaly produced by three prisms. Comparisons of the computed results with theoretical total field show excellent agreement in anomaly shapes and amplitude. All mean relative errors of computed total field are less than 2%, in contrast, the results calculated from vertical gradient and calculated from longitudinal and transverse gradients by using Hilbert transform relations are better, the mean relative errors are less than 1%. In addition, random noise was added to theoretical gradient data to test the feasibility of the method. Model tests indicate that the algorithm is stable and produces good results.The technique was tested on aeromagnetic gradients data collected by three axis airborne gradiometer. Comparisons of the calculated results with measured total field show good agreement in anomaly shapes, but the amplitudes are not good agree with the measured total field for most of the region, there are more obvious long-period errors, the total fields obtained from gradients can eliminate diurnal problem but have other errors. The errors source need to be analyzed further.

  11. Contact freezing of supercooled cloud droplets on collision with mineral dust particles: effect of particle size

    NASA Astrophysics Data System (ADS)

    Hoffmann, Nadine; Duft, Denis; Kiselev, Alexei; Leisner, Thomas

    2013-04-01

    The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in the tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. However, the laboratory experiments of contact freezing are very challenging due to the number of factors affecting the probability of ice formation. In our experiment we study single water droplets freely levitated in the laminar flow of mineral dust particles acting as the contact freezing nuclei. By repeating the freezing experiment sufficient number of times we are able to reproduce statistical freezing behavior of large ensembles of supercooled droplets and measure the average rate of freezing events. We show that the rate of freezing at given temperature is governed only by the rate of droplet -particle collision and by the properties of the contact ice nuclei. In this contribution we investigate the relationship between the freezing probability and the size of mineral dust particle (represented by illite) and show that their IN efficiency scales with the particle size. Based on this observation, we discuss the similarity between the freezing of supercooled water droplets in immersion and contact modes and possible mechanisms of apparent enhancement of the contact freezing efficiency. [1] - K.C. Young, The role of contact nucleation in ice phase initiation in clouds, Journal of the Atmospheric Sciences 31, 1974

  12. Dielectric gradient metasurface optical elements.

    PubMed

    Lin, Dianmin; Fan, Pengyu; Hasman, Erez; Brongersma, Mark L

    2014-07-18

    Gradient metasurfaces are two-dimensional optical elements capable of manipulating light by imparting local, space-variant phase changes on an incident electromagnetic wave. These surfaces have thus far been constructed from nanometallic optical antennas, and high diffraction efficiencies have been limited to operation in reflection mode. We describe the experimental realization and operation of dielectric gradient metasurface optical elements capable of also achieving high efficiencies in transmission mode in the visible spectrum. Ultrathin gratings, lenses, and axicons have been realized by patterning a 100-nanometer-thick Si layer into a dense arrangement of Si nanobeam antennas. The use of semiconductors can broaden the general applicability of gradient metasurfaces, as they offer facile integration with electronics and can be realized by mature semiconductor fabrication technologies. PMID:25035488

  13. In vivo experiments and numerical investigations on nanocryosurgical freezing of target tissues with large blood vessels.

    PubMed

    Sun, Zi-Qiao; Yang, Yang; Liu, Jing

    2012-02-01

    This study presented the first in vivo animal experiments of using nano-cryosurgical modality to completely freezing tumor tissues embedded with large blood vessels, which is a tough issue to tackle otherwise. Three-dimensional theoretical simulations were also performed on the complex freezing problems by considering flow and heat transfer of blood flow in large vessels. According to the experimental measurements and numerical predictions, injecting the nanoparticles with high thermal conductivity into the freezing target can significantly reduce the heating effect of blood vessel, shorten the freezing time, and enlarge the freezing range. Most importantly, the introduction of nanoparticles successfully overcomes the classical challenges in completely ablating the tumor region with large blood vessel and enhancing the freezing efficacy of cryosurgery. This investigation consolidates the practical and theoretical foundation for nano-cryosurgery which suggests a highly efficient freezing strategy for treating late stage tumor. PMID:22515090

  14. Dependence of scroll-wave dynamics on the orientation of a gradient of excitability

    NASA Astrophysics Data System (ADS)

    Dähmlow, Patricia; Hauser, Marcus J. B.

    2013-12-01

    The dynamics of scroll waves with a variable orientation to a vertically oriented gradient of excitability is studied by optical tomography in the ferroin-catalyzed Belousov-Zhabotinsky reaction. An almost perpendicular orientation between the scroll wave and gradient induces a pair of twists of opposite handedness on the scroll wave. The position of the nodal plane formed between the twists is governed by the time delay of the twist formation and therefore leads to a symmetric or asymmetric twisted scroll wave. Larger inclinations between scroll wave and gradient cause a drift of the filament along the reactor wall until it reaches the bottom of the reaction container. In this case, the scroll wave does not twist, suggesting that a drift acts as an alternative mechanism of responding to the gradient.

  15. Evaluation of vertical profiles to design continuous descent approach procedure

    NASA Astrophysics Data System (ADS)

    Pradeep, Priyank

    The current research focuses on predictability, variability and operational feasibility aspect of Continuous Descent Approach (CDA), which is among the key concepts of the Next Generation Air Transportation System (NextGen). The idle-thrust CDA is a fuel economical, noise and emission abatement procedure, but requires increased separation to accommodate for variability and uncertainties in vertical and speed profiles of arriving aircraft. Although a considerable amount of researches have been devoted to the estimation of potential benefits of the CDA, only few have attempted to explain the predictability, variability and operational feasibility aspect of CDA. The analytical equations derived using flight dynamics and Base of Aircraft and Data (BADA) Total Energy Model (TEM) in this research gives insight into dependency of vertical profile of CDA on various factors like wind speed and gradient, weight, aircraft type and configuration, thrust settings, atmospheric factors (deviation from ISA (DISA), pressure and density of the air) and descent speed profile. Application of the derived equations to idle-thrust CDA gives an insight into sensitivity of its vertical profile to multiple factors. This suggests fixed geometric flight path angle (FPA) CDA has higher degree of predictability and lesser variability at the cost of non-idle and low thrust engine settings. However, with optimized design this impact can be overall minimized. The CDA simulations were performed using Future ATM Concept Evaluation Tool (FACET) based on radar-track and aircraft type data (BADA) of the real air-traffic to some of the busiest airports in the USA (ATL, SFO and New York Metroplex (JFK, EWR and LGA)). The statistical analysis of the vertical profiles of CDA shows 1) mean geometric FPAs derived from various simulated vertical profiles are consistently shallower than 3° glideslope angle and 2) high level of variability in vertical profiles of idle-thrust CDA even in absence of uncertainties in external factors. Analysis from operational feasibility perspective suggests that two key features of the performance based Flight Management System (FMS) i.e. required time of arrival (RTA) and geometric descent path would help in reduction of unpredictability associated with arrival time and vertical profile of aircraft guided by the FMS coupled with auto-pilot (AP) and auto-throttle (AT). The statistical analysis of the vertical profiles of CDA also suggests that for procedure design window type, 'AT or above' and 'AT or below' altitude and FPA constraints are more realistic and useful compared to obsolete 'AT' type altitude constraint.

  16. Validation of simulated flow direction and hydraulic gradients with hydraulic head observations using open source GIS

    NASA Astrophysics Data System (ADS)

    Vandersteen, Katrijn; Rogiers, Bart; Gedeon, Matej

    2015-04-01

    It is recommended to check hydraulic gradients and flow directions predicted by a groundwater flow model that is calibrated solely with hydraulic head observations. It has been demonstrated in literature that substantial errors can be made when the model is not calibrated on these state variables. Therefore, in this work, we perform a validation of a steady-state groundwater flow model, representing part of the Neogene aquifer (60 km2) in Belgium. This model was developed and calibrated solely on groundwater head measurements, in the framework of the environmental impact assessment of the near surface repository for low- and intermediate-level short-lived waste, realized by ONDRAF/NIRAS at Dessel, Belgium. Horizontal flow directions, horizontal and vertical gradients for the entire area of the groundwater model were estimated from measurements at shallow monitoring wells within the groundwater flow model domain, and compared to the flow directions and vertical gradients predicted by the model. For obtaining horizontal flow directions and gradients, triangulation of groundwater levels was performed for combinations of three neighboring hydraulic head observations in the same hydrogeological layer within the model. The simulated equivalents at the same monitoring wells were used to repeat the same methodology, and calculate flow direction components. This analysis was performed in SAGA GIS and was visualized through QGIS. Comparison of the flow directions and flow gradients obtained from measurements and simulations gives an indication on the model performance. The calculations were performed for three sandy hydrogeological units used in the model. A similar procedure was performed for the vertical hydraulic head gradients, where any combination of two hydraulic head observations at the same location but at different levels within the aquifer were used to validate the vertical gradients predicted by the model. Besides model validation on average hydraulic heads, the variability of flow direction and hydraulic gradients in time was checked, by using the actually measured monthly time series, to verify the applicability of the steady-state modelling approach. This basic assessment of flow directions and gradients using open source GIS can be used to identify potential areas of interest, were more detailed investigations would be recommended.

  17. Gradient waveform synthesis for magnetic propulsion using MRI gradient coils

    Microsoft Academic Search

    B H Han; S Y Lee

    2008-01-01

    Navigating an untethered micro device in a living subject is of great interest for both diagnostic and therapeutic applications. Magnetic propulsion of an untethered device carrying a magnetic core in it is one of the promising methods to navigate the device. MRI gradients coils are thought to be suitable for navigating the device since they are capable of magnetic propulsion

  18. Space-time gradient metasurfaces

    E-print Network

    Hadad, Y; Alu, A

    2015-01-01

    Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the nanoscale. Here we add a temporal gradient to the picture, showing that spatio-temporal variations over a surface may largely extend the degree of light manipulation in metasurfaces, and break several of their constraints associated to symmetries. As an example, we synthesize a non-reciprocal classical analogue to electromagnetic induced transparency, opening a narrow window of one-way transmission in an otherwise opaque surface. These properties pave the way to magnetic free, planarized non-reciprocal ultrathin surfaces for free-space isolation.

  19. Deliquescence and freezing of stratospheric aerosol observed by balloonborne backscattersondes

    NASA Astrophysics Data System (ADS)

    Larsen, Niels; Rosen, James M.; Kjome, Norman T.; Knudsen, Bjorn

    1995-05-01

    Stratospheric sulfate aerosols, originating from the Mt. Pinatubo volcanic eruption, have been observed during three winters in the Arctic by balloonborne backscattersondes. A measured color index, defined as the quotient between the aerosol backscatter ratios at wavelengths 940 and 480 nm, provides information of the size of the observed particles. The effects of liquid particle growth, by water vapor uptake, clearly show up as changes in the color index, whereas measurements on other days indicate the particles to be frozen. Air parcel trajectories have been calculated, providing the temperature history of the observed particles. Evidences appear of a temperature hysteresis in the freezing and melting cycle of the aerosol, indicating melting temperatures around 215-220 K in good agreement with laboratory measurements, and freezing of the particles within less than 5 K above the ice frost point. The changes in color index of the liquid particles are in good agreement with predictions from theoretical model calculations of growth by water vapor uptake.

  20. Enthalpy relaxation of freeze concentrated sucrose-water glass.

    PubMed

    Inoue, Chiharu; Suzuki, Toru

    2006-02-01

    The enthalpy relaxation of freeze concentrated sucrose-water glass was investigated using 40% sucrose, differential scanning calorimetry (DSC) with isothermal ageing for 1-6 days at various temperatures (-70, -65, -60, and -55 degrees C). The enthalpy relaxation was observed as an endothermic peak superimposed on the endothermic step-wise change due to the glass transition around -47 degrees C. The enthalpy relaxation was found to increase with ageing time and temperature. An 80% sucrose glass was also investigated at ageing temperatures of -60 and -65 degrees C, and this material exhibited a similar glass transition and enthalpy relaxation to that observed with the frozen 40% sucrose solution. The calculated activation energy of the enthalpy relaxation of the sucrose-water glass was smaller than that reported for pure sucrose. These results suggest that the freeze concentrated sucrose-water glass could have a higher molecular mobility and less stability than pure sucrose glass. PMID:16321366