Science.gov

Sample records for vertical gradient freeze

  1. Effects of a traveling magnetic field on vertical gradient freeze growth of cadmium zinc telluride

    NASA Astrophysics Data System (ADS)

    Yeckel, Andrew; Derby, Jeffrey J.

    2011-09-01

    The effects of a traveling magnetic field (TMF) on vertical gradient freeze (VGF) growth of cadmium zinc telluride (CZT) are studied using a coupled model of magnetic induction, fluid dynamics, and heat transfer. Simulations are performed to determine the influences of current and frequency on melt flow and growth interface shape. A downward traveling electromagnetic wave drives flow downward at the wall, which tends to flatten the interface, whereas an upward traveling wave has the opposite effect. TMF makes a significant impact on interface shape in the absence of thermal buoyancy, but is ineffectual under realistic conditions in a 4 inch diameter ampoule, for which buoyancy dominates Lorentz force throughout the melt.

  2. Design and fabrication of eight zone vertical dynamic gradient freeze system for organic single crystal growth.

    PubMed

    Prabhakaran, S P; Babu, R Ramesh; Ramamurthi, K

    2013-08-01

    Design and construction of the vertical dynamic gradient freeze (VDGF) system operating in the temperature range from 50 °C to 500 °C for growing organic single crystals are described. The design of VDGF system consists of furnace, control system, translation assembly, and image capturing device. Furnace has been constructed with eight zones controlled independently by a dynamic temperature control system for achieving desired thermal environment and multiple temperature gradients, which are essential for the growth of organic single crystals. The transparent furnace enables direct observation to record and monitor the solid-liquid interface and growth of crystals through charge coupled device based video camera. The system is fully computerized hence it is possible to retrieve the complete growth and furnace history. In order to investigate the functioning of the constructed VDGF system for the growth of organic single crystals, a well known organic nonlinear optical single crystal of benzimidazole was grown. The crystalline quality and the optical transmittance of the grown crystal were studied. PMID:24007079

  3. Electron Backscatter Diffraction Analysis of a CZT Growth Tip from a Vertical Gradient Freeze Furnace

    SciTech Connect

    Sundaram, S. K.; Henager, Charles H.; Edwards, Danny J.; Schemer-Kohrn, Alan L.; Bliss, Mary; Riley, Brian J.

    2011-08-15

    Electronic backscatter diffraction (EBSD) was used to characterize the growth-tip region of a 4.2-cm diameter CdZnTe (CZT) boule grown using low-pressure Bridgman method in a vertical gradient freeze furnace. The boule was sectioned and polished and a section taken along the boule longitudinal centerline with an approximate surface area of 1-cm2 was used for optical and scanning electron microscopy. A collage was assembled using EBSD/SEM images to show morphological features, e.g., twin structure, grain structure, and overall crystal growth direction. Severely twinned regions originating from the tip and side walls were observed. The overall growth orientation was close to <110> and <112> directions. In some regions, the (001) poles of the CZT matrix aligned with the growth direction, while twins aligned such that (111) and (112) poles aligned with the growth direction. In some other areas, (112) or (011) poles of the CZT matrix aligned with the growth direction. New relationships between the CZT matrix and large Te polycrystalline particles were revealed: {11 }CZT{1 00}Te and {001}CZT{0 1}Te.

  4. Synthesis and crystal growth of Mg2Si by the liquid encapsulated vertical gradient freezing method

    NASA Astrophysics Data System (ADS)

    Nakagawa, Reo; Katsumata, Hiroshi; Hashimoto, Satoshi; Sakuragi, Shiro

    2015-08-01

    The synthesis of Mg2Si bulk crystals was performed by the vertical gradient freezing method using a KCl-MgCl2 eutectic liquid encapsulant. Stoichiometric polycrystalline Mg2Si bulk crystals were successfully grown by changing the composition ratio of starting Mg and Si powders (Mg/Si) from 2.0 to 3.5. A chemical reaction between Mg2Si and the crucible materials was inhibited using encapsulant materials, and the contamination by K or Cl originating from the encapsulant materials was not detected in almost all the samples. However, Mg evaporation could not be prevented completely during the synthesis and crystal growth. The optical band-gap energy of Mg2Si bulk crystals became minimal (0.79 eV) at a Mg/Si ratio of 2.5, at which the maximum electron mobility of 202 cm2V-1s-1 was obtained. These results indicate that the composition ratio of Mg/Si = 2.5 for starting Mg and Si powders was optimal for synthesizing Mg2Si bulk crystals with high crystalline quality.

  5. 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.

  6. The prospects for traveling magnetic fields to affect interface shape in the vertical gradient freeze growth of cadmium zinc telluride

    NASA Astrophysics Data System (ADS)

    Yeckel, Andrew; Derby, Jeffrey J.

    2013-02-01

    The influence of a traveling magnetic field (TMF) on vertical gradient freeze (VGF) growth of cadmium zinc telluride (CZT) is studied using a coupled model of magnetic induction, fluid dynamics, and heat transfer. Simulations are performed to determine the influences of current, phase shift, and frequency on melt flow and growth interface shape. A downward traveling electromagnetic wave drives flow downward at the wall, which tends to flatten the interface, whereas an upward traveling wave has the opposite effect. An optimum phase shift that maximizes Lorentz force is found to depend only on system geometry. Large currents (˜300 A) and high frequencies (˜500 Hz) make a significant impact on interface shape in the absence of thermal buoyancy, but are ineffectual under realistic conditions in a 4 in.-diameter ampoule, for which buoyancy dominates Lorentz force throughout the melt. The results indicate that interface shape in this CZT growth system is strongly governed by furnace heat transfer and is difficult to modify by TMF-driven forced convection.

  7. Synchrotron X-ray topographic study of dislocations in GaAs detector crystals grown by vertical gradient freeze technique

    SciTech Connect

    Tuomi, T.; Juvonen, M.; Rantamaeki, R.

    1998-12-31

    Large area transmission and section topographs of semi-insulating gallium arsenide wafers grown by the gradient freeze technique are made with synchrotron radiation at HASYLAB in Hamburg and at ESRF in Grenoble. Several high-resolution images including stereo pairs are obtained on the same film at a time. A typical dislocation line is an arc of a circle which starts from one surface and ends at the same surface. From the disappearance of the dislocation image and using the g {center_dot} b = 0 criterion it is concluded that the Burgers vector b of the most common dislocations is parallel to <110>. Rather large volumes of the wafer are dislocation-free. Section topographs of epitaxial wafers show defects and strain fields at the interface between an n-type substrate and the epitaxial layers grown by chemical vapor deposition. The results are compared with those obtained from detector performance measurements.

  8. 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.

  9. Semiconductor apparatus utilizing gradient freeze and liquid-solid techniques

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

    1998-01-01

    Transition metals of Group VIII (Co, Rh and Ir) have been prepared as semiconductor compounds with the general formula TSb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freezing techniques and/or liquid phase sintering techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 1200 cm.sup.2.V.sup.-1.s.sup.-1) and good Seebeck coefficients (up to 150 .mu.VK.sup.-1 between 300.degree. C. and 700.degree. C.). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a substantial increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400.degree. C. for thermoelectric elements fabricated from such semiconductor materials.

  10. Controlled Temperature Gradient Improves Freezing Alloy

    NASA Technical Reports Server (NTRS)

    Schmidt, Deborah; Alter, Wendy S.; Hamilton, William D.

    1991-01-01

    Controlled gradient of temperature in advancing zone of solidification increases fatigue life of directionally solidified nickel-base superalloy. Improved solidification process eliminates, reduces, or controls microstructure of deleterious brittle phases, including carbides and gamma/gamma prime eutectic. Also reduces microsegregation and makes discrete carbides (if present) become fine and blocky. Expected to improve properties of other alloys, of both directionally-solidified polycrystalline and single-crystal forms.

  11. Convective flows in enclosures with vertical temperature or concentration gradients

    NASA Technical Reports Server (NTRS)

    Wang, L. W.; Chai, A. T.; Sun, D. J.

    1988-01-01

    The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.

  12. Convective flows in enclosures with vertical temperature or concentration gradients

    NASA Technical Reports Server (NTRS)

    Wang, L. W.; Chai, A. T.; Sun, D. J.

    1989-01-01

    The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.

  13. Daytime and Nighttime Vertical Gradients of HONO in Houston, TX.

    NASA Astrophysics Data System (ADS)

    Wong, K.; Stutz, J.; Oh, H.

    2008-12-01

    Nitrous acid (HONO) plays an important role in tropospheric photochemistry as a precursor of the hydroxyl radical (OH), the primary oxidizing agent in the atmosphere. Nevertheless, the sources of HONO have not yet been fully understood. Recently, daytime HONO concentrations higher than expected have been observed in various field experiments. The cause of these elevated HONO levels is currently unclear. The vertical distribution of HONO at night and during the day, which can have a considerable impact on the importance of HONO for ozone formation, is also currently poorly characterized by observations and models. Measurements of daytime and nighttime HONO vertical profiles were made in Houston in Summer 2006 during the TexAQS II Radical and Aerosol Measurement Project (TRAMP) using long path DOAS. HONO developed negative concentration gradients during the night, due to inefficient vertical mixing, and a combination of ground deposition of NO2 and HONO and heterogeneous conversion of NO2 to HONO on surfaces. Despite the efficient vertical mixing during the day, boundary layer HONO gradients were also observed, indicating possible unknown source of HONO near the ground. Here we present and discuss the field observations of HONO and other traces gases during TRAMP and the modeling of daytime and nighttime HONO gradients using a one dimensional (1-D) chemistry and transport model.

  14. Using absolute gravimeter data to determine vertical gravity gradients

    USGS Publications Warehouse

    Robertson, D.S.

    2001-01-01

    The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may be applicable to a broader class of data that may be contaminated with "system response" errors of larger magnitude than were evident in the data used by Hipkin. This system response function is usually modelled as a sum of exponentially decaying sinusoidal components. The technique employed here involves combining the x0, v0 and g parameters from all the drops made during a site occupation into a single least-squares solution, and including the value of the vertical gradient and the coefficients of system response function in the same solution. The resulting non-linear equations must be solved iteratively and convergence presents some difficulties. Sparse matrix techniques are used to make the least-squares problem computationally tractable.

  15. Freezing tolerance in grasses along an altitudinal gradient in the Venezuelan Andes.

    PubMed

    Márquez, Edjuly J; Rada, Fermín; Fariñas, Mario R

    2006-12-01

    The tropical high Andes experience greater daily temperature oscillations compared to seasonal ones as well as a high frequency of night frost occurrence year round. Survival of organisms, under such environmental conditions, has been determined by selective forces which have evolved into adaptations including avoidance or tolerance to freezing. These adaptations have been studied in different species of trees, shrubs and perennial herbs in páramo ecosystems, while they have not been considered in grasses, an important family of the páramo. In order to understand survival of Poaceae, resistance mechanisms were determined. The study was performed along an altitudinal gradient (2,500-4,200 m a.s.l.) in the páramo. Supercooling capacity and frost injury temperature were determined in nine species in order to establish cold resistance mechanisms. Grasses registered a very low supercooling capacity along the altitudinal gradient, with ice formation between -6 and -3 degrees C. On the other hand, frost injury temperature oscillated between -18 and -7 degrees C. Our results suggest that grasses exhibit freezing tolerance as their main cold resistance mechanism. Since grasses grow at ground level, where greatest heat loss takes place, tolerance may be related to this life form as reported for other small life forms. PMID:17024382

  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. 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.

  18. 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.

  19. Retained functional integrity of bull spermatozoa after double freezing and thawing using PureSperm density gradient centrifugation.

    PubMed

    Maxwell, W M C; Parrilla, I; Caballero, I; Garcia, E; Roca, J; Martinez, E A; Vazquez, J M; Rath, D

    2007-10-01

    The main aim of this study was to compare the motility and functional integrity of bull spermatozoa after single and double freezing and thawing. The viability and morphological integrity of spermatozoa selected by PureSperm density gradient centrifugation after cryopreservation of bovine semen in two commercial extenders (Experiment 1) and the function of bull spermatozoa before and after a second freezing and thawing assisted by PureSperm selection (Experiment 2) were examined. On average, 35.8 +/- 12.1% of sperm loaded onto the PureSperm density gradient were recovered after centrifugation. In Experiment 1, post-thaw motility and acrosome integrity were higher for spermatozoa frozen in Tris-egg yolk extender than in AndroMed, whether the assessments were made immediately after thawing [80.4 +/- 12.7 vs 47.6 +/- 19.0% motile and 78.8 +/- 8.3 vs 50.1 +/- 19.5% normal apical ridge (NAR), p < 0.05] or after preparation on the gradient (83.3 +/- 8.6 vs 69.4 +/- 15.9% motile and 89.5 +/- 7.2 vs 69.1 +/- 11.4% NAR, p < 0.05). For semen frozen in Tris-egg yolk extender, selection on the PureSperm gradient did not influence total motility but significantly improved the proportion of acrosome-intact spermatozoa. After the gradient, both the total motility and percentage of normal acrosomes increased for spermatozoa frozen in AndroMed (Minitb Tiefenbach, Germany). In Experiment 2, there was no difference in sperm motility after the first and second freeze-thawing (82.9 +/- 12.7 vs 68.8 +/- 18.7%). However, the proportion of acrosome-intact spermatozoa was significantly improved by selection through the PureSperm gradient, whether measured by phase contrast microscopy (78.9 +/- 9.7 vs 90.4 +/- 4.0% NAR, p < 0.05) or flow cytometry (53.4 +/- 11.7 vs 76.3 +/- 6.0% viable acrosome-intact spermatozoa, p < 0.001). The improvement in the percentage of spermatozoa with normal acrosomes was maintained after resuspension in the cooling extender and cooling to 4 degrees C (88.2 +/- 6.2) and after re-freezing and thawing (83.6 +/- 6.56% NAR). However, flow cytometric assessment of the sperm membranes revealed a decline in the percentage of viable spermatozoa with intact membranes after the second freezing and thawing compared with after gradient centrifugation (76.3 +/- 6.0% vs 46.6 +/- 6.6%, p < 0.001) to levels equivalent to those obtained after the first round of freeze-thawing (53.4 +/- 11.7% viable acrosome-intact spermatozoa). Sperm movement characteristics assessed by computer-assisted analysis were unaffected in the population selected on the PureSperm gradients but declined after cooling of the selected and extended spermatozoa to 4 degrees C. There was no further change in these kinematic measurements after the cooled spermatozoa had undergone the second round of freeze-thawing. These results demonstrate that bull semen can be frozen and thawed, followed by a second freeze-thawing cycle of a population of spermatozoa selected by PureSperm, with retained motility and functional integrity. This points to the possibility of using double frozen spermatozoa in bovine artificial insemination programmes and to the potential benefits of PureSperm density gradient centrifugation for the application of cryopreserved bull spermatozoa to other biotechnological procedures such as flow cytometric sex sorting followed by re-freezing and thawing. PMID:17845604

  20. Freezing mechanisms of aqueous binary solution on the oscillating vertical cooled plate

    SciTech Connect

    Kawabe, Hiromichi; Fukusako, Shoichiro; Yamada, Masahiko; Yanagida, Koki

    1999-07-01

    An experimental and analytical study concerning the freezing characteristics of aqueous binary solution on the oscillating cooled wall was conducted for the purpose of establishment of the continuous production method of slush ice. Ethylene glycol solution was adopted as the test fluid and froze on a vertical cooled plate with an oscillation motion in a vessel. Experiments were carried out for a variety of conditions such as initial concentration of solution, oscillating acceleration, and stroke of the motion. As a result, it was found that the frozen layer being formed on the cooled plate continuously separated from it under the appropriate conditions. Furthermore, the condition range where the continuous production of slush ice may be available was well predicted by using the present analytical results. The experimental setup is depicted in Figure A-1. The essential components of the apparatus are the test section, a cooling brine circulation loop, and associated instrumentation. Figure A-2 presents the continuous production range of slush ice, in which the ordinate is the maximum acceleration of the cooled plate and the abscissa denotes the initial concentration of aqueous binary solution. It is evident from the figure that the tendency of the production range of slush ice obtained by the present analysis well predicts the experimental results.

  1. Modeling of daytime HONO vertical gradients during SHARP 2009

    NASA Astrophysics Data System (ADS)

    Wong, K. W.; Tsai, C.; Lefer, B.; Grossberg, N.; Stutz, J.

    2012-10-01

    Nitrous Acid (HONO) acts as a major precursor of the hydroxyl radical (OH) in the urban atmospheric boundary layer in the morning and throughout the day. Despite its importance, HONO formation mechanisms are not yet completely understood. It is generally accepted that conversion of NO2 on surfaces in the presence of water is responsible for the formation of HONO in the nocturnal boundary layer, although the type of surface on which the mechanism occurs is still under debate. Recent observations of higher than expected daytime HONO concentrations in both urban and rural areas indicate the presence of unknown daytime HONO source(s). Various formation pathways in the gas-phase and on aerosol and ground surfaces have been proposed to explain the presence of daytime HONO. However, it is unclear which mechanism dominates and, in the cases of heterogeneous mechanisms, on which surfaces they occur. Vertical concentration profiles of HONO and its precursors can help in identifying the dominant HONO formation pathways. In this study, daytime HONO and NO2 vertical profiles, measured in three different height intervals (20-70 m, 70-130 m and 130-300 m) in Houston, TX during the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) are analyzed using a one-dimensional (1-D) chemistry and transport model. Model results with various HONO formation pathways suggested in the literature are compared to the the daytime HONO and HONO/NO2 ratios observed during SHARP. The best agreement of HONO and HONO/NO2 ratios between model and observations is achieved by including both a photolytic source of HONO at the ground and on the aerosol. Model sensitivity studies show that the observed diurnal variations of HONO/NO2 ratio are not reproduced by the model if there is only a photolytic HONO source on aerosol or in the gas-phase from NO2* + H2O. Further analysis of the formation and loss pathways of HONO shows a vertical dependence of HONO chemistry during the day. Photolytic HONO formation at the ground is the major formation pathway in the lowest 20 m, while a combination of gas-phase, photolytic formation on aerosol, and vertical transport is responsible for daytime HONO between 200-300 m a.g.l. HONO removal is dominated by vertical transport below 20 m and photolysis between 200-300 m a.g.l.

  2. Modeling of daytime HONO vertical gradients during SHARP 2009

    NASA Astrophysics Data System (ADS)

    Wong, K. W.; Tsai, C.; Lefer, B.; Grossberg, N.; Stutz, J.

    2013-04-01

    Nitrous acid (HONO) acts as a major precursor of the hydroxyl radical (OH) in the urban atmospheric boundary layer in the morning and throughout the day. Despite its importance, HONO formation mechanisms are not yet completely understood. It is generally accepted that conversion of NO2 on surfaces in the presence of water is responsible for the formation of HONO in the nocturnal boundary layer, although the type of surface on which the mechanism occurs is still under debate. Recent observations of higher than expected daytime HONO concentrations in both urban and rural areas indicate the presence of unknown daytime HONO source(s). Various formation pathways in the gas phase, and on aerosol and ground surfaces have been proposed to explain the presence of daytime HONO. However, it is unclear which mechanism dominates and, in the cases of heterogeneous mechanisms, on which surfaces they occur. Vertical concentration profiles of HONO and its precursors can help in identifying the dominant HONO formation pathways. In this study, daytime HONO and NO2 vertical profiles, measured in three different height intervals (20-70, 70-130, and 130-300 m) in Houston, TX, during the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) are analyzed using a one-dimensional (1-D) chemistry and transport model. Model results with various HONO formation pathways suggested in the literature are compared to the the daytime HONO and HONO/NO2 ratios observed during SHARP. The best agreement of HONO and HONO/NO2 ratios between model and observations is achieved by including both a photolytic source of HONO at the ground and on the aerosol. Model sensitivity studies show that the observed diurnal variations of the HONO/NO2 ratio are not reproduced by the model if there is only a photolytic HONO source on aerosol or in the gas phase from NO2* + H2O. Further analysis of the formation and loss pathways of HONO shows a vertical dependence of HONO chemistry during the day. Photolytic HONO formation at the ground is the major formation pathway in the lowest 20 m, while a combination of gas-phase, photolytic formation on aerosol, and vertical transport is responsible for daytime HONO between 200-300 m a.g.l. HONO removal is dominated by vertical transport below 20 m and photolysis between 200-300 m a.g.l.

  3. 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.

  4. Overburden Pressure as a Cause of Vertical Velocity Gradient

    NASA Astrophysics Data System (ADS)

    Korneev, V. A.

    2012-12-01

    Nonlinear effect of rocks stressed by the overburden pressure causes anisotropy. Evaluation shows that such anisotropy can be significant, reaching several tens of percent and probably more. This result is consistent with common practices, when stacking velocity needs extra corrections with a changing offset. This also implies that at field scales all the rocks are likely to be anisotropic, and this property needs to be accounted for during migration of data, tomography, AVO analysis etc. The laboratory velocity measurements need to be corrected for the nonlinear overburden effects, when applied to the field scales. Nonlinear rock coefficients can be determined from the special laboratory measurements. They also can be evaluated from observation of the nonlinear propagation effects, such as multiple frequency generation. Nonlinear coefficient for Berea sandstone turned out to be by an order of magnitude larger than that estimated from borehole data. This is likely due to low stiffness and low fluid saturation of the used sample. This also suggests possibility of very high velocity gradient at shallow depths in some rocks. An assumption that the amplitudes of the static strains well exceed those related to the dynamic field is not critical. It was made in order to simplify the derivations. If both components are comparable, then the solution would have an additional nonlinear component representing a multiple harmonic. The relations between the nonlinear elastic constants and the elastic constants of the effective TI medium are very simple and allow straightforward estimate of the medium anisotropy induced by an applied stress. There are other causes of anisotropy in rocks besides an applied stress. The rock can possibly be anisotropic on a microscopic (clays) and mesoscopic (sedimentary layering) levels. The combined contribution of all the causes can either reduce or increase the overall effect. Same rock at different depths might have different wave propagation properties. Proper geological interpretation of seismic velocity maps requires application of local depth corrections, which can remove the overburden pressure effects.verage velocity model for Los Angeles basin (blue line) and a least-squares fit (red line) using nonlinear theory.

  5. 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.

  6. Suppression of Hydrophobic Recovery by Plasma Polymer Films with Vertical Chemical Gradients.

    PubMed

    Hegemann, Dirk; Lorusso, Emanuela; Butron-Garcia, Maria-Isabel; Blanchard, Noémi E; Rupper, Patrick; Favia, Pietro; Heuberger, Manfred; Vandenbossche, Marianne

    2016-01-26

    Vertical chemical gradients extending over a few nanometers were explored. The gradients are based on plasma-polymerized oxygen-containing ethylene (ppOEt) films. Using plasma conditions with low CO2/C2H4 ratio and high energy input, cross-linked films were deposited as base layer, while increasing CO2 and lowering energy input resulted in less cross-linked yet highly functional films as applied as top layer. Aging studies indicate that, in particular, for very thin gradient structures, the cross-linked subsurface zone effectively hinders reorientation of the surface functional groups, thus restricting hydrophobic recovery and oxidation effects. PMID:26716609

  7. Comparison of heat-pulse flow measurements and vertical gradients in a fractured limestone aquifer

    SciTech Connect

    Dearborn, L.L.; Calkin, S.F.; Andolsek, R.H.; Allison, W.S.

    1996-11-01

    Establishing a site-specific relationship between heat-pulse flowmeter (HPFM) data and corresponding vertical gradient data may allow prediction of potential vertical gradients through BPFM logging alone. Vertical gradient and corresponding BPFM rates were determined for 117 test intervals in a fractured limestone bedrock aquifer. From these data, it appears that HPFM data can be used in place of more labor intensive borehole packer testing to provide estimates of vertical gradients in this type of hydrogeologic system. Groundwater conditions in the fractured bedrock were investigated through testing of 66 open boreholes, as part of the hazardous waste remedial investigation at the former Loring Air Force Base (LAFB) in northern Maine, USA. Borehole geophysical logging tools, including BPFM and acoustic televiewer (ATV), in conjunction with air hammer drilling logs, were used to target specific fracture(s) to test using conventional straddle packers. HPFM and head data from 41 boreholes met general requirements for comparison purposes, and a linear correlation trend was identified.

  8. Creating stiffness gradient polyvinyl alcohol hydrogel using a simple gradual freezing-thawing method to investigate stem cell differentiation behaviors.

    PubMed

    Kim, Tae Ho; An, Dan Bi; Oh, Se Heang; Kang, Min Kwan; Song, Hyun Hoon; Lee, Jin Ho

    2015-02-01

    Polyvinyl alcohol (PVA) cylindrical hydrogel with a stiffness gradient was prepared using a simple liquid nitrogen (LN2)-contacting gradual freezing and thawing method in order to investigate the effects of substrate stiffness on stem cell differentiation into specific cell types. The prepared cylindrical PVA hydrogel showed a gradually increasing stiffness along the longitudinal direction from the top at approximately 1 kPa to the bottom (LN2 contacted side) at approximately 24 kPa. From the in vitro culture of bone marrow stem cells, it was observed that each soft (∼1 kPa) and stiff (∼24 kPa) hydrogel section promotes effective neurogenesis and osteogenesis of the cells, respectively, with the tendency to gradually decrease toward the opposing characteristic's side. The stiffness gradient cylindrical PVA hydrogel fabricated using this simple gradual freezing and thawing method can be a useful tool for basic studies, including the determination of optimum stiffness ranges for a variety of stem cell differentiations, as well as the investigation of cell migration in terms of substrate stiffness. PMID:25467820

  9. Does vertical temperature gradient of the atmosphere matter for El Niño development?

    NASA Astrophysics Data System (ADS)

    Hu, Zeng-Zhen; Huang, Bohua; Tseng, Yu-heng; Wang, Wanqiu; Kumar, Arun; Zhu, Jieshun; Jha, Bhaskar

    2016-05-01

    In this work, we examine the connection of vertical temperature gradient of the tropospheric atmosphere along the equator with El Niño-Southern Oscillation (ENSO) and the possible impact of the long-term change of the gradient. It is suggested that when the temperature anomalies in the lower troposphere are relatively warmer (cooler) than in the upper troposphere, the atmosphere is less (more) stable and favors an El Niño (a La Niña) event to develop. ENSO evolutions in 1997-1998 and 2014-2015 events are good examples of this relationship. They started from similar ocean anomaly states in the springs of 1997 and 2014, but developed into an extreme El Niño in 1997-1998 and a borderline El Niño in 2014-2015. That may be partially due to differences in the evolutions of the vertical temperature anomaly gradient in troposphere. Thus, in addition to the significant atmospheric response to ENSO, the preconditioning of vertical gradient of the tropospheric temperature due to internal atmospheric processes to some extent may play an active role in affecting ENSO evolution. The long-term trend with more pronounced warming in the upper troposphere than in the lower troposphere causes a reduction in the vertical temperature gradient in the troposphere. Moreover, unlike almost homogenous warm anomalies in the upper troposphere, the lower troposphere shows remarkable regional features along the equator during 1979-2014, with cold anomaly trends over the central and eastern Pacific Ocean associated with the so-called hiatus and some warm anomalies on its two sides in the east and west. This vertical and zonal distribution of the air temperature trends in the troposphere over the Pacific Ocean is consistent with the convection suppression over the central Pacific since 2000, implying a weakening of atmosphere and ocean coupling.

  10. Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method

    NASA Technical Reports Server (NTRS)

    Choi, J.; Cruz, Magda; Metzl, R.; Wang, W. S.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.

    1998-01-01

    A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

  11. HONO Vertical Gradients during the 2006 TRAMP and the 2009 SHARP experiments in Houston, TX

    NASA Astrophysics Data System (ADS)

    Wong, K.; Tsai, C.; Pikelnaya, O.; Stutz, J.; Fu, D.

    2009-12-01

    Nitrous acid (HONO) plays a significant role in tropospheric photochemistry as a precursor of the hydroxyl radical (OH). Despite the importance of HONO photolysis for the OH budget in the early morning, HONO formation mechanisms are not yet fully understood. In addition, recent observations of higher than expected daytime HONO concentrations are currently unexplained. The vertical distribution of HONO in the morning and during the day can have a considerable impact on its importance for ozone formation in the boundary layer. The observation of vertical profiles is also important to allow a better understanding of HONO formation in the atmosphere. Consequently there is an urgent need to provide observations and detailed model calculations of vertical HONO profiles. During the 2009 SHARP experiment from April 15 to May 29, 2009 in Houston, TX, we performed measurements of HONO, NO2, O3 and other trace gases in three altitude intervals (30-70m, 70 - 130m, and 130 - 300m), using UCLA’s long path DOAS instrument. Vertical gradients of all atmospheric trace gases were frequently observed during stable nights. HONO established negative gradients, with higher concentrations near the ground, indicating that the source of HONO is at or near the ground. Daytime HONO gradients were also observed during some days. Here we compare our results with observations made at the same location in 2006 and with results from a 1-D chemical transport model to elucidate the mechanisms forming HONO in urban areas.

  12. GOCE derived vertical gravity gradient delineates great earthquake rupture zones along the Chilean margin

    NASA Astrophysics Data System (ADS)

    Álvarez, Orlando; Nacif, Silvina; Gimenez, Mario; Folguera, Andres; Braitenberg, Carla

    2014-05-01

    In the south Central Andes region, the Nazca oceanic plate that subducts beneath the South American plate is characterized by a rough topography derived from different oceanic features that collide against the continental margin. These features determine an important segmentation of both the margin and of the interplate zone. The Chilean subduction margin has been characterized by megathrust earthquakes affecting the plate interface with large rupture areas reaching hundreds of kilometers parallel to the trench. The occurrence of these phenomena has been linked, among other causes, to the subduction of sediments that fill the trench and their spatial relation to the relatively prominent oceanic features. We calculated the topography corrected vertical gravity gradient from GOCE satellite data and from EGM2008 model in order to delineate mass heterogeneities related to density variations along the south-central Chile subduction zone. Obtained results show a spatial relation between the subduction of the Nazca oceanic highs and associated along-strike segmentation of the vertical gravity gradients over the interplate zone. We compared our results with the different rupture areas and found a good correspondence with the ellipses for the main earthquakes such as the Valdivia-1960 and Maule-2010 ones. Then, we compared vertical gravity gradients with slip distribution obtained from different models, finding that they are actually correlated with high slip over negative vertical gradient. The GOCE derived gradient adjusts better with the main slip distribution contour since its signal has a characteristic high wavelength. Instead, the EGM2008 model presents a better performance in defining the high frequency anomalies. However, the last results need to be considered only in those regions where the statistical comparison with GOCE data shows a good performance. This is because EGM2008 model data present varying quality of the original terrestrial data, while the quality of the GOCE data is locally homogeneous.

  13. Vertical two-phase flow regimes and pressure gradients: Effect of viscosity

    SciTech Connect

    Da Hlaing, Nan; Sirivat, Anuvat; Siemanond, Kitipat; Wilkes, James O.

    2007-05-15

    The effect of liquid viscosity on the flow regimes and the corresponding pressure gradients along the vertical two-phase flow was investigated. Experiment was carried out in a vertical transparent tube of 0.019 m in diameter and 3 m in length and the pressure gradients were measured by a U-tube manometer. Water and a 50 vol.% glycerol solution were used as the working fluids whose kinematic viscosities were 0.85 x 10{sup -6} and 4.0 x 10{sup -6} m{sup 2}/s, respectively. In our air-liquid annular two-phase flow, the liquid film of various thicknesses flowed adjacent to the wall and the gas phase flowed at the center of the tube. The superficial air velocity, j{sub air}, was varied between 0.0021 and 58.7 m/s and the superficial liquid velocity, j{sub liquid}, was varied between 0 and 0.1053 m/s. In the bubble, the slug and the slug-churn flow regimes, the pressure gradients decreased with increasing Reynolds number. But in the annular and the mist flow regimes, pressure gradients increased with increasing Reynolds number. Finally, the experimentally measured pressure gradient values were compared and are in good agreement with the theoretical values. (author)

  14. Vertical gradients and seasonal variation in stem CO2 efflux within a Norway spruce stand.

    PubMed

    Tarvainen, Lasse; Räntfors, Mats; Wallin, Göran

    2014-05-01

    Stem CO2 efflux is known to vary seasonally and vertically along tree stems. However, annual tree- and stand-scale efflux estimates are commonly based on measurements made only a few times a year, during daytime and at breast height. In this study, the effect of these simplifying assumptions on annual efflux estimates and their influence on the estimates of the importance of stems in stand-scale carbon cycling are evaluated. In order to assess the strength of seasonal, diurnal and along-stem variability in CO2 efflux, half-hourly measurements were carried out at three heights on three mature Norway spruce (Picea abies (L.) Karst.) trees over a period of 3 years. Making the common assumption of breast height efflux rates being representative of the entire stem was found to result in underestimations of 10-17% in the annual tree-scale CO2 efflux. Upscaling using only daytime measurements from breast height increased the underestimation to 15-20%. Furthermore, the results show that the strength of the vertical gradient varies seasonally, being strongest in the early summer and non-existent during the cool months. The observed seasonality in the vertical CO2 efflux gradient could not be explained by variation in stem temperature, temperature response of the CO2 efflux (Q10), outer-bark permeability, CO2 transport in the xylem or CO2 release from the phloem. However, the estimated CO2 concentration immediately beneath the bark was considerably higher in the upper stem during the main period of diameter growth, coinciding with the strongest vertical efflux gradient. These results suggest that higher growth rates in the upper stem are the main cause for the observed vertical variation in the stem CO2 effluxes. Furthermore, the results indicate that accounting for the vertical efflux variation is essential for assessments of the importance of stems in stand-scale carbon cycling. PMID:24878562

  15. 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.

  16. The effect of vocal fold vertical stiffness gradient on sound production

    NASA Astrophysics Data System (ADS)

    Geng, Biao; Xue, Qian; Zheng, Xudong

    2015-11-01

    It is observed in some experimental studies on canine vocal folds (VFs) that the inferior aspect of the vocal fold (VF) is much stiffer than the superior aspect under relatively large strain. Such vertical difference is supposed to promote the convergent-divergent shape during VF vibration and consequently facilitate the production of sound. In this study, we investigate the effect of vertical variation of VF stiffness on sound production using a numerical model. The vertical variation of stiffness is produced by linearly increasing the Young's modulus and shear modulus from the superior to inferior aspects in the cover layer, and its effect on phonation is examined in terms of aerodynamic and acoustic quantities such as flow rate, open quotient, skewness of flow wave form, sound intensity and vocal efficiency. The flow-induced vibration of the VF is solved with a finite element solver coupled with 1D Bernoulli equation, which is further coupled with a digital waveguide model. This study is designed to find out whether it's beneficial to artificially induce the vertical stiffness gradient by certain implanting material in VF restoring surgery, and if it is beneficial, what gradient is the most favorable.

  17. Estimating Effective Vertical Diffusivity in Shallow Ponds by a Constrained Flux-Gradient Method

    NASA Astrophysics Data System (ADS)

    Bean, J. R.; Torgersen, T.

    2004-12-01

    Shallow ponds have been used to mitigate the deleterious effects of storm water run-off by acting as detention/retention basins that sequester run-off associated pollutants in sediments. Studies show that the retention efficiency of these systems can decrease over time as a result of the internal loading of nutrients/contaminants from the sediments back to the water column where they are available for export downstream. Quantifying the vertical transport of gases (down) and sediment derived materials (up) is vital to the modeling and understanding of the processes that contribute to the magnitude of internal loading. A critical parameter is the effective vertical diffusion coefficient: Kz=Dmolecular +Deddy (cm2 sec-1). The flux gradient method for estimating effective vertical thermal diffusivity has been applied with success in large lakes which undergo stratification cycles on seasonal or longer time scales. We offer a constrained version of the flux-gradient method that has been adapted for use in a shallow pond with a daily stratification cycle. The method employs heat as a tracer and assumes that transport in the face of a stable gradient is diffusive. By shrinking the spatial and temporal resolution of measurement to scales appropriate to the system of interest and carefully accounting for internal source and sink terms of heat (e.g solar radiation and sediment heat fluxes) we are able to calculate Kz as a function of time and depth during periods of stable stratification, i.e when the pond is not vertically well-mixed. Results show the magnitude of Kz varies from ca. 10-3 to 10-1 (cm2 sec-1) under stratified conditions depending primarily on the strength of stratification.

  18. The vertical metallicity gradient of the Milky Way disk: transitions in [α/Fe] populations

    SciTech Connect

    Schlesinger, Katharine J.; Johnson, Jennifer A.; Rockosi, Constance M.; Beers, Timothy C.; Harding, Paul; Allende Prieto, Carlos; Bird, Jonathan C.; Schönrich, Ralph; Yanny, Brian; Schneider, Donald P.; Weaver, Benjamin A.; Brinkmann, Jon

    2014-08-20

    Using G dwarfs from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey, we have determined the vertical metallicity gradient in the Milky Way's disk and examined how this gradient varies for different [α/Fe] subsamples. Our sample contains over 40,000 stars with low-resolution spectroscopy over 144 lines of sight. It also covers a significant disk volume, between ∼0.3 and 1.6 kpc from the Galactic plane, and allows us to examine the disk in situ, whereas previous analyses were more limited in scope. Furthermore, this work does not presuppose a disk structure, whether composed of a single complex population or distinct thin and thick disk components. We employ the SEGUE Stellar Parameter Pipeline to obtain estimates of stellar parameters, [Fe/H], and [α/Fe] and extract multiple volume-complete subsamples of approximately 1000 stars each. Based on SEGUE's target-selection algorithm, we adjust each subsample to determine an unbiased picture of disk chemistry; consequently, each individual star represents the properties of many. The metallicity gradient is –0.243{sub −0.053}{sup +0.039} dex kpc{sup –1} for the entire sample, which we compare to various literature results. This gradient stems from the different [α/Fe] populations inhabiting different ranges of height above the Galactic plane. Each [α/Fe] subsample shows little change in median [Fe/H] with height. If we associate [α/Fe] with age, the negligible gradients of our [α/Fe] subsamples suggest that stars formed in different epochs exhibit comparable vertical structure, implying similar star formation processes and evolution.

  19. 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 μm 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.

  20. Vertical two-phase flow regimes and pressure gradients under the influence of SDS surfactant

    SciTech Connect

    Duangprasert, Tanabordee; Sirivat, Anuvat; Siemanond, Kitipat; Wilkes, James O.

    2008-01-15

    Two-phase gas/liquid flows in vertical pipes have been systematically investigated. Water and SDS surfactant solutions at various concentrations were used as the working fluids. In particular, we focus our work on the influence of surfactant addition on the flow regimes, the corresponding pressure gradients, and the bubble sizes and velocity. Adding the surfactant lowers the air critical Reynolds numbers for the bubble-slug flow and the slug flow transitions. The pressure gradients of SDS solutions are lower than those of pure water especially in the slug flow and the slug-churn flow regimes, implying turbulent drag reduction. At low Re{sub air}, the bubble sizes of the surfactant solution are lower than those of pure water due to the increase in viscosity. With increasing and at high Re{sub air}, the bubble sizes of the SDS solution become greater than those of pure water which is attributed to the effect of surface tension. (author)

  1. Sensitivity of airborne fluorosensor measurements to linear vertical gradients in chlorophyll concentration

    NASA Technical Reports Server (NTRS)

    Venable, D. D.; Punjabi, A. R.; Poole, L. R.

    1984-01-01

    A semianalytic Monte Carlo radiative transfer simulation model for airborne laser fluorosensors has been extended to investigate the effects of inhomogeneities in the vertical distribution of phytoplankton concentrations in clear seawater. Simulation results for linearly varying step concentrations of chlorophyll are presented. The results indicate that statistically significant differences can be seen under certain conditions in the water Raman-normalized fluorescence signals between nonhomogeneous and homogeneous cases. A statistical test has been used to establish ranges of surface concentrations and/or verticl gradients in which calibration by surface samples would by inappropriate, and the results are discussed.

  2. The horizontal gradients of the recent vertical movements in the Carpatho-Balkan Region

    NASA Astrophysics Data System (ADS)

    Jo, I.

    1993-12-01

    In the countries of the Carpatho-Balkan Region (CBR) intensive research of recent crustal movements has been carried out by repeated geodetic measurements for more than two decades. Within the framework of this programme during the last few years finer tendencies of the movements begin to become resolved in the measured values. For this purpose in the network of about 27,000 km total length, horizontal gradients of the vertical velocities were deduced for each levelling section and the geological sections of the lines were completed. We present the gradients for the whole CBR jointly on a thematical map, scale 1:1,000,000 (Jo et al., 1991a); a separate explanatory description belongs to it. The map was printed in colour together with English and Russian texts. It also presents the morphology. In this work the following countries took part: Czech and Slovak Republics, Poland, part of the earlier Soviet Union, Rumania, Bulgaria and Hungary. The investigations were coordinated by Hungary and the publishing of the map was done there. Within this paper the following will be presented: the method of investigation, the data used, the important intermediate steps of the work and the results including the map of horizontal gradients itself.

  3. Use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer

    USGS Publications Warehouse

    McCoy, K.J.; Kozar, M.D.

    2008-01-01

    The carbonate-rock aquifer in the Great Valley, West Virginia, USA, was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural, lithologic, and topographic influences on the groundwater flow system. The enhanced permeability of the aquifer is characterized in part by the many sinkholes, springs, and solutionally enlarged fractures throughout the valley. Yet, vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood. To address this problem, this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification: (1) the distribution of sinkholes and (2) the occurrence of wells with relatively high specific capacity. Statistical results indicate that sinkholes (funnel and collapse) occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest. Conversely, high specific capacity values are common along prominent joints perpendicular or oblique to strike. The similarity of the latter distribution to that of springs suggests these fractures are areas of upward-convergent flow. These differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing. ?? 2007 Springer-Verlag.

  4. Impacts of freezing and thawing dynamics on foliar litter carbon release in alpine/subalpine forests along an altitudinal gradient in the eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Fuzhong, W.; Changhui, P.; Jianxiao, Z.; Jian, Z.; Bo, T.; Wanqin, Y.

    2014-11-01

    Carbon (C) release from foliar litter is a primary component in C exchange among the atmosphere, vegetation, soil and water from respiration and leaching, but little information is currently related to the effects of freezing and thawing dynamics on C release of foliar litter in cold regions. A 2-year field litter decomposition experiment was conducted along an altitudinal gradient (~ 2700 to ~ 3600 m) to mimic temperature increases in the eastern Tibetan Plateau. C release was investigated for fresh foliar litter of spruce, fir and birch. The onset of the frozen stage, deep frozen stage and thawing stage was partitioned according to changes in the freezing and thawing dynamics of each winter. More rapid 2-year C released from fresh foliar litter at upper elevations compared to lower elevations in the alpine/subalpine region. However, high C release was observed at low altitudes during winter stages, but high altitudes exhibited high C release during growing season stages. The deep frozen stage showed higher rates of C release than other stages in the second year of decomposition. Negative-degree days showing freezing degrees were correlated to C release rates for the deep frozen stages in both years, and this relationship continued for the duration of the experiment, indicating that changes in freezing can directly modify C release from foliar litter. The results suggested that the changed freezing and thawing dynamics could delay the onset of C release in fresh litter in this cold region in the scenario of climate warming.

  5. Global grids of gravity anomalies and vertical gravity gradients at 10 km altitude from GOCE gradient data 2009-2011 and polar gravity.

    NASA Astrophysics Data System (ADS)

    Tscherning, Carl Christian; Arabelos, Dimitrios; Reguzzoni, Mirko

    2013-04-01

    The GOCE satellite measures gravity gradients which are filtered and transformed to gradients into an Earth-referenced frame by the GOCE High Level processing Facility. More than 80000000 data with 6 components are available from the period 2009-2011. IAG Arctic gravity was used north of 83 deg., while data at the Antarctic was not used due to bureaucratic restrictions by the data-holders. Subsets of the data have been used to produce gridded values at 10 km altitude of gravity anomalies and vertical gravity gradients in 20 deg. x 20 deg. blocks with 10' spacing. Various combinations and densities of data were used to obtain values in areas with known gravity anomalies. The (marginally) best choice was vertical gravity gradients selected with an approximately 0.125 deg spacing. Using Least-Squares Collocation, error-estimates were computed and compared to the difference between the GOCE-grids and grids derived from EGM2008 to deg. 512. In general a good agreement was found, however with some inconsistencies in certain areas. The computation time on a usual server with 24 processors was typically 100 minutes for a block with generally 40000 GOCE vertical gradients as input. The computations will be updated with new Wiener-filtered data in the near future.

  6. Flow regimes in a vertical Taylor-Couette system with a radial thermal gradient

    NASA Astrophysics Data System (ADS)

    Guillerm, R.; Kang, C.; Savaro, C.; Lepiller, V.; Prigent, A.; Yang, K.-S.; Mutabazi, I.

    2015-09-01

    A rich variety of flow regimes in a Newtonian fluid inside a vertical large-aspect ratio and a wide-gap Taylor-Couette system with a radial temperature gradient has been determined in experiments and in direct numerical simulations (DNSs). Compared to previous experiments and numerical studies, a wider range of temperature differences (i.e., of the Grashof number Gr) and of the rotation rate (the Taylor number Ta) has been covered. The combined effect of rotation and of the radial temperature gradient is the occurrence of helicoidal vortices or modulated waves at the onset. Stationary axisymmetric vortices are found for very weak temperature differences. A good agreement was found for critical states between results from experiments, linear stability analysis, and DNS. Higher instability modes have been determined for a wide range of parameters and a state diagram of observable flow regimes has been established in the plane spanned by Gr and Ta. Some higher states observed in experiments were retrieved in DNS.

  7. 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.

    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)

  8. Individual and population plasticity of the seagrass Zostera noltii along a vertical intertidal gradient

    NASA Astrophysics Data System (ADS)

    Cabaço, Susana; Machás, Raquel; Santos, Rui

    2009-04-01

    The seasonal plasticity of individual Zostera noltii architectural, reproductive and elemental content features, of plant epiphyte load and of meadow biomass-density relationships was investigated along a vertical intertidal gradient at Ria Formosa lagoon, southern Portugal. The vertical variability of the seagrass environment was evident in the sediment characteristics, which showed coarser grain size, less organic matter, lower N content and higher ammonium concentration in the low intertidal than in medium and high intertidal. A clear vertical differentiation in Z. noltii morphology was observed from longer and wider leaves, longer and wider internodes and shorter roots at low intertidal, to shorter and narrow leaves, shorter and narrower internodes and longer roots at high intertidal. The leaf size was negatively related to light availability and positively related to nutrient availability whereas the root size was negatively related to nutrient availability. The lower leaf N and P content found in low intertidal plants may reflect a dilution effect of the nutrients due to higher growth rates. Lower N content of low intertidal leaves supports previous findings that the nitrate reductase activity is lower in plants from this level. The higher epiphyte load observed in Z. noltii leaves of the low intertidal may be a consequence of the lower exposure period, but also of higher hydrodynamics that increase the availability of nutrients. No evidence of the influence of the intertidal level on the flowering shoot density was found. The cyclic temporal pattern of the biomass-density relationship was much wider at low and medium intertidal than at high intertidal. At low intertidal, the decline in shoot density during fall and winter was coincident with a biomass decrease and its increase in spring and summer coincided with the biomass increase. In medium and high intertidal, the biomass and density seasonal variations were decoupled. As a result, only at low intertidal there was a significant positive relationship between biomass and density. This suggests that Z. noltii population structure along the intertidal is regulated by different factors. Light is probably the most important factor regulating the population structure in the low intertidal, whereas desiccation is probably the main factor regulating the populations in upper intertidal. Zostera noltii showed a considerable plasticity at a physiological-, plant- and population-level along the intertidal zone, indicative of the species acclimation to the steep environmental gradient of this particular ecosystem.

  9. Impact of changes in freezing and thawing on foliar litter carbon release in alpine/subalpine forests along an altitudinal gradient in the eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wu, F.; Peng, C.; Zhu, J.; Zhang, J.; Tan, B.; Yang, W.

    2014-06-01

    Carbon (C) release from foliar litter is a primary component in C exchange between the atmosphere and terrestrial ecosystems, but little information is currently related to the effects of freezing and thawing dynamics on C release of foliar litter in cold regions. A two-year field litter decomposition experiment was conducted along an altitudinal gradient (∼2700 m to ∼3600 m) to mimic temperature increases in the eastern Tibetan Plateau. C release was investigated for fresh foliar litter of spruce, fir and birch. The onset of the frozen stage, deep frozen stage, and thawing stage were partitioned according to changes in freezing and thawing dynamics of each winter. High C release was observed in lower altitudes during winter stages, but higher altitudes exhibited high C release during growing season stages. The deep frozen stage showed higher rates of C release than other stages in the second year of decomposition. Negative degree-days showing freezing degree were correlated to C release rates for the deep frozen stages in both years, and this relationship continued for the duration of the experiment, indicating that changes in freezing can directly modify C release from foliar litter. The results suggested that climate warming could delay the onset of C release in fresh litter in this cold region.

  10. Large vertical gradient of reactive nitrogen oxides in the boundary layer: Modeling analysis of DISCOVER-AQ 2011 observations

    NASA Astrophysics Data System (ADS)

    Zhang, Yuzhong; Wang, Yuhang; Chen, Gao; Smeltzer, Charles; Crawford, James; Olson, Jennifer; Szykman, James; Weinheimer, Andrew J.; Knapp, David J.; Montzka, Denise D.; Wisthaler, Armin; Mikoviny, Tomas; Fried, Alan; Diskin, Glenn

    2016-02-01

    An often used assumption in air pollution studies is a well-mixed boundary layer (BL), where pollutants are evenly distributed. Because of the difficulty in obtaining vertically resolved measurements, the validity of the assumption has not been thoroughly evaluated. In this study, we use more than 200 vertical profiles observed in the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) aircraft campaign in July 2011 to examine the vertical distributions of pollutants over the Washington-Baltimore area. While many long-lived species are well mixed in daytime, the observed average vertical profile of NOx shows a large negative gradient with increasing altitude in the BL. Our analysis suggests that the magnitude of the NOx gradient is highly sensitive to atmospheric stability. We investigate how parameterizations of the BL and land-surface processes impact vertical profiles in a 1-D chemical transport model, using three BL schemes (Asymmetric Convective Model version 2 (ACM2), Yonsei University (YSU), and Mellor-Yamada-Janjic (MYJ)) and two land-surface schemes (Noah and Rapid Update Cycle (RUC)). The model reasonably reproduces the median vertical profiles of NOx under different BL stability conditions within 30% of observations, classified based on potential temperature gradient and BL height. Comparisons with NOx observations for individual vertical profiles reveal that while YSU performs better in the turbulent and deep BL case, in general, ACM2 (RMSE = 2.0 ppbv) outperforms YSU (RMSE = 2.5 ppbv) and MYJ (RMSE = 2.2 ppbv). Results also indicate that the land-surface schemes in the Weather Research and Forecasting (WRF) model have a small impact on the NOx gradient. Using model simulations, we analyze the impact of BL NOx gradient on the calculation of the ozone production rate and satellite NO2 retrieval. We show that using surface measurements and the well-mixed BL assumption causes a ~45% high bias in the estimated BL ozone production rate and that the variability of NO2 vertical profiles is responsible for 5-10% variability in the retrieved NO2 tropospheric vertical columns.

  11. 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...

  12. Seasonality of Isoprenoid Vertical Gradient Within a Primary Rainforest in Central Amazonia

    NASA Astrophysics Data System (ADS)

    Alves, E. G.; Jardine, K.; Tota, J.; Jardine, A. B.; Yanez-Serrano, A. M.; Karl, T.; Guenther, A. B.; Tavares, J. V.; Nelson, B. W.

    2014-12-01

    Vertical mixing ratio gradients of isoprene, total monoterpenes (TMt) and total sesquiterpenes (TSt) were quantified, within and above the canopy, in a primary rainforest in central Amazonia , using a Proton Transfer Reaction - Mass Spectrometer (PTR-MS). We also estimated the fluxes of these compounds from the canopy into the atmosphere. Measurements were carried out from the dry season (Sept/2010) to the wet season (Jan/2011), continuously. All compound mixing ratios were higher during the dry season than during the wet season; the same behavior was observed for ambient air temperature and photosynthetically active radiation (PAR). Isoprene and TMt mixing ratios were higher within the canopy as compared to near the ground and above the canopy. Daytime TSt mixing ratios were higher near the ground than within and above the canopy. Isoprene and TMt had a diurnal cycle similar to diurnal cycles of air temperature and PAR suggesting that the emission of these compounds are light dependent and stimulated by increasing temperature. However, this same behavior was not observed for TSt. This is probably due to the fact that sesquiterpene emissions are not strongly light dependent; the ozonolysis of sesquiterpenes during daytime could reduce ambient sesquiterpene concentrations; and a less turbulent atmospheric boundary layer during nighttime could make the mixing ratio of sesquiterpenes higher near the surface at nighttime. Daytime flux estimations also presented seasonal variation for the fluxes of all compounds, such that fluxes of: isoprene ranged from 0.4 to 1.5 mg m-2 h-1, TMt ranged from 0.2 to 0.8 mg m-2 h-1, and TSt ranged from 0.1 to 0.25 mg m-2 h-1, being the highest end during the dry season. These flux estimations suggested that the canopy could be the main source of those compounds for the atmosphere for all seasons. Our results provide the first in situ observations of seasonal mixing ratio gradients of isoprenoids in central Amazonia, and suggest that some of the isoprenoid seasonal variations could be driven by changes in light, temperature and leaf phenology.

  13. The Effect of Vertical Temperature Gradient on the Propagation of Three-dimensional Waves in a Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Lee, Wing-Kit; Gu, Pin-Gao

    2015-11-01

    Excitation and propagation of waves in a thermally stratified disk with an arbitrary vertical temperature profile are studied. Previous analytical studies of three-dimensional waves had been focused on either isothermal or polytropic vertical disk structures. However, at the location in a protoplanetary disk where the dominant heating source is stellar irradiation, the temperature gradient may become positive in the vertical direction. We extend the analysis to study the effects of the vertical temperature structure on the waves that are excited at the Lindblad resonances. For a hotter disk atmosphere, the f-mode contributes less to the torque and remains confined near the midplane as it propagates away from the resonances. On the other hand, the excitation of the g-modes is stronger. As they propagate, they channel to the top of disk atmosphere and their group velocities decrease. The differences compared to previous studies may have implications in understanding the wave dynamics in a realistic disk structure.

  14. A meridional structure of static stability and ozone vertical gradient around the tropopause in the Southern Hemisphere extratropics

    NASA Astrophysics Data System (ADS)

    Tomikawa, Y.; Yamanouchi, T.

    2010-08-01

    An analysis of the static stability and ozone vertical gradient in the ozone tropopause based (OTB) coordinate is applied to the ozonesonde data at 10 stations in the Southern Hemisphere (SH) extratropics. The tropopause inversion layer (TIL) with a static stability maximum just above the tropopause shows similar seasonal variations at two Antarctic stations, which are latitudinally far from each other. Since the sunshine hour varies with time in a quite different way between these two stations, it implies that the radiative heating due to solar ultraviolet absorption of ozone does not contribute to the seasonal variation of the TIL. A meridional section of the static stability in the OTB coordinate shows that the static stability just above the tropopause has a large latitudinal gradient between 60° S and 70° S in austral winter because of the absence of the TIL over the Antarctic. It is accompanied by an increase of westerly shear with height above the tropopause, so that the polar-night jet is formed above this latitude region. This result suggests a close relationship between the absence of the TIL and the stratospheric polar vortex in the Antarctic winter. A vertical gradient of ozone mixing ratio, referred to as ozone vertical gradient, around the tropopause shows similar latitudinal and seasonal variations with the static stability in the SH extratropics. In a height region above the TIL, a small ozone vertical gradient in the midlatitudes associated with the Antarctic ozone hole is observed in a height region of the subvortex but not around the polar vortex. This is a clear evidence of active latitudinal mixing between the midlatitudes and subvortex.

  15. Vertical canopy gradient in photosynthesis and monoterpenoid emissions: An insight into the chemistry and physiology behind

    NASA Astrophysics Data System (ADS)

    Šimpraga, M.; Verbeeck, H.; Bloemen, J.; Vanhaecke, L.; Demarcke, M.; Joó, E.; Pokorska, O.; Amelynck, C.; Schoon, N.; Dewulf, J.; Van Langenhove, H.; Heinesch, B.; Aubinet, M.; Steppe, K.

    2013-12-01

    It is well known that vertical canopy gradients and varying sky conditions influence photosynthesis (Pn), specific leaf area (SLA), leaf thickness (LT) and leaf pigments (lutein, â-carotene and chlorophyll). In contrast, little is known about these effects on monoterpenoid (MT) emissions. Our study examines simultaneously measured Pn, MT emissions and the MT/Pn ratio along the canopy of an adult European beech tree (Fagus sylvatica L.) in natural forest conditions. Dynamic branch enclosure systems were used at four heights in the canopy (7, 14, 21 and 25 m) in order to establish relationships and better understand the interaction between Pn and MT emissions under both sunny and cloudy sky conditions. Clear differences in Pn, MT emissions and the MT/Pn ratio were detected within the canopy. The highest Pn rates were observed in the sun leaves at 25 m due to the higher intercepted light levels, whereas MT emissions (and the MT/Pn ratio) were unexpectedly highest in the semi-shaded leaves at 21 m. The higher Pn rates and, apparently contradictory, lower MT emissions in the sun leaves may be explained by the hypothesis of Owen and Peñuelas (2005), stating synthesis of more photo-protective carotenoids may decrease the emissions of volatile isoprenoids (including MTs) because they both share the same biochemical precursors. In addition, leaf traits like SLA, LT and leaf pigments clearly differed with height in the canopy, suggesting that the leaf's physiological status cannot be neglected in future research on biogenic volatile organic compounds (BVOCs) when aiming at developing new and/or improved emission algorithms.

  16. Large Vertical Gradient of Reactive Nitrogen Oxides in the Boundary Layer: Modeling Analysis of DISCOVER-AQ Observations

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Wang, Y.; Chen, G.; Smeltzer, C.; Liu, Z.; Crawford, J. H.; Olson, J. R.; Szykman, J.

    2013-12-01

    An often-used assumption of air pollution studies is the well-mixed planetary boundary layer (PBL), in which pollutants are evenly distributed. Because of the difficulty in obtaining vertically-resolved measurements, the validity of the assumption has not been thoroughly established. In this study, we use more than 200 vertical profiles observed in the DISCOVER-AQ aircraft campaign in 2011 to examine the vertical distributions of air pollutants over the Baltimore area during the summer. Contrary to the well-mixed profile, the observed median vertical profile of NOx, an important ozone precursor, shows a sharp negative gradient in the PBL. Our analysis suggests that the magnitude of NOx gradients is highly sensitive to atmospheric stability. Using a 1-D chemical transport model (REAM), we are able to reproduce the vertical profiles under different PBL stability conditions, classified based on the potential temperature gradient and the PBL height. To investigate how the parameterizations of the PBL and surface processes impact vertical profiles in 3-D chemical transport models, we test PBL mixing properties using two PBL schemes (Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ)) and two land-surface schemes (Noah and RUC) in the WRF model. Comparisons reveal that the YSU scheme performs better in turbulent and high PBL height conditions while the MYJ scheme performs better in less turbulent conditions. Results also show that the land-surface schemes in WRF do not have as large an influence as the PBL mixing schemes. Using the model results, we evaluate the impact of NOx gradient in the PBL on the calculation of the ozone production rate and satellite NO2 retrieval. We show that using the surface measurements and the well-mixed PBL assumption result in a ~30% high bias in the PBL ozone production rate. Our results also show that biases in the PBL height and the NOx gradient lead to a moderate bias (about 5%) in the retrieval of NO2 tropospheric vertical columns. In addition, we diagnose the isoprene emission flux in the 1-D model, which is constrained by in situ observations of NOx, O3, and VOCs including isoprene, and find it in good agreement with that calculated in the MEGAN model.

  17. [A 61-year-old man with progressive gait disturbance, freezing, and vertical gaze paresis who developed esophagus cancer].

    PubMed

    Miyashita, N; Kondo, T; Wakiya, M; Mori, H; Shirai, T; Takubo, H; Mizuno, Y

    1998-11-01

    We report a 61-year-old Japanese man who died of complications of esophagus cancer surgery. He was well until his 55 years of the age, when he had an onset of speech disturbance and hand writing. He was seen by a neurologist who prescribed Menesit 600 mg/day. His symptoms improved with this medication. In 1993, three years after the onset, he started to show gait disturbance and easy to fall. In 1995, he noted difficulty in eye opening. He visited our clinic on October 26, 1996. On examination, he showed vertical gaze paresis, masked face, nuchal rigidity, small step gait, freezing phenomena, and festination. His mental status was normal. He was treated with 800 mg/day of Menesit, 800 mg/day of L-dops, and 10 mg/day of bromocriptine with little improvement in his symptoms. Cranial CT scan revealed some dilatation of the third ventricle. Subsequent clinical course was one of the slow progression of his parkinsonism. In September of 1997, he noted difficulty in swallowing. He was admitted to the gastrointestinal service of our hospital on October 14, 1997. On admission, neurologic status was essentially similar to the previous one, but he showed more advanced state of his parkinsonism. Upper gastrointestinal series revealed a mass lesion of about 11.5 cm in length protruding into the lower esophagus lumen. Subtotal esophagus resection including the mass was performed on December 2, 1997. The stomach was elevated for anastomosis with the upper esophagus. No metastases were found in the mediastinum except for two lymph nodes in the para-esophageal region. The subsequent course was complicated by marked elevation of GOT, GPT, LDH, total bilirubin as well as direct bilirubin, alkaliphosphatase, and amylase starting in the evening of the surgery. On December 7, leukocytosis and pneumonic shadow were seen involving his right lung. On December 10, he developed cardiopulmonary arrest. He was once resuscitated; however, he developed cardiac arrest again seven hours later and pronounced dead. He was discussed in a neurologic CPC. The chief discussant arrived at the conclusion that the patient had PSP and the cause of the death was ascribed to circulatory disturbance to the liver. The discussant also thought that the terminal course was complicated by cholangitis or cholecystitis, sepsis, and pulmonary embolism. Surgical specimen of the esophagus tumor revealed carcinosarcoma. Postmortem examination revealed yellowish discoloration of the peritoneum and mesenterium, and accumulation of clouded ascites indicating the presence of peritonitis. Inflammatory change extended to the mediastinum. On microscopic examination, various kinds of bacilli and candida spores were seen. The liver was enlarged and a perforation was noted in the gallbladder causing biliary necrosis in the adjacent liver. An extensive infarct was seen in the left lobe of the liver; this was found to be due to obstruction of the hepatic artery at the site of the duodenohepatic mesenterium and obstruction of intrahepatic portal vein secondary to retrograde intrahepatic cholangitis in the left lobe. A piece of surgical threads was seen adjacent to the hepatic artery; foreign body granulomatous reaction was seen surrounding the surgical thread. The rupture of the gallbladder appeared to be due to the obstruction of the left branch of the hepatic artery. Neuropathologic examination revealed extensive degeneration of the pallidum, the substantia nigra, and the subthalamic nucleus and presence of neurofibrillary tangles in the remaining neurons. The neuropathologic findings were consistent with progressive supranuclear palsy, although the pathologic changes in the midbrain tegmentum was only mild gliosis. PMID:9866133

  18. Combining high resolution vertical gradients and sequence stratigraphy to delineate hydrogeologic units for a contaminated sedimentary rock aquifer system

    NASA Astrophysics Data System (ADS)

    Meyer, Jessica R.; Parker, Beth L.; Arnaud, Emmanuelle; Runkel, Anthony C.

    2016-03-01

    Hydrogeologic units (HGUs), representing subsurface contrasts in hydraulic conductivity, form the basis for all conceptual and numerical models of groundwater flow. However, conventionally, delineation of these units relies heavily on data sets indirect with respect to hydraulic properties. Here, we use the spatial and temporal characteristics of the vertical component of hydraulic gradient (i.e., vertical gradient) as the primary line of evidence for delineating HGUs for Cambrian-Ordovician sedimentary rocks at a site in Dane County, Wisconsin. The site includes a 16 km2 area encompassing a 3 km long mixed organic contaminants plume. The vertical gradients are derived from hydraulic head profiles obtained using high resolution Westbay multilevel systems installed at 7 locations along two, orthogonal 4 km long cross-sections and monitoring to depths between 90 and 146 m with an average of 3-4 monitoring zones per 10 m. These vertical gradient cross-sections reveal 11 laterally extensive HGUs with contrasting vertical hydraulic conductivity (Kv). The position and thickness of the Kv contrasts are consistently associated with sequence stratigraphic features (maximum flooding intervals and sequence boundaries) distinguished at the site using cores and borehole geophysical logs. The same sequence stratigraphic features are also traceable across much of the Cambrian-Ordovician aquifer system of the Midwest US. The vertical gradients and sequence stratigraphy were arrived at independently and when combined provide a hydraulically calibrated sequence stratigraphic framework for the site. This framework provides increased confidence in the precise delineation and description of the nature of HGU contacts in each borehole, reduced uncertainty in interpolation of the HGUs between boreholes, and some capability to predict HGU boundaries and thickness in offsite areas where high resolution hydraulic data sets are not available. Consequently, this HGU conceptual model will serve as a better basis for numerical simulations of groundwater flow and contaminant transport needed for continued risk assessment and to evaluate potential remedial technologies for the site. More broadly, the association between Kv contrasts and sequence stratigraphy demonstrated at this site provides valuable insight into the relationship between geology and hydraulic contrasts that can be transferred to other areas of the upper Midwest US and perhaps elsewhere to strata deposited in similar settings.

  19. 3D unconstrained and geologically constrained stochastic inversion of airborne vertical gravity gradient data

    NASA Astrophysics Data System (ADS)

    Tchikaya, Euloge Budet; Chouteau, Michel; Keating, Pierre; Shamsipour, Pejman

    2016-02-01

    We present an inversion tool for airborne gravity gradient data that yields a 3D density model using stochastic methods i.e. cokriging and conditional simulation. This method uses geostatistical properties of the measured gravity gradient to estimate a 3D density model whose gravity response fits the measured gravity gradient anomaly. Linearity between gravity gradient data and density allows estimation of the model (density) covariance using observed data, i.e. we adjust iteratively the density covariance matrix by fitting experimental and theoretical gravity gradient covariance matrices. Inversion can be constrained by including densities known at some locations. In addition we can explore various reasonable solutions that honour both the estimated density covariance model and the gravity gradient data using geostatistical simulation. The proposed method is first tested with two synthetic datasets generated from a sharp-boundary model and a smooth stochastic model respectively. The results show the method to be capable of retrieving models compatible with the true models; it also allows the integration of complex a priori information. The technique is then applied to gravity gradient survey data collected for the Geological Survey of Canada in the area of McFaulds Lake (Ontario, Canada) using the Falcon airborne gravity system. Unconstrained inversion returns a density model that is geologically plausible and the computed response exactly fits the observed gravity gradient anomaly.

  20. Vertical GPS ground motion rates in the Euro-Mediterranean region: new evidence of vertical velocity gradients at different spatial scales along the Nubia-Eurasia plate boundary

    NASA Astrophysics Data System (ADS)

    Serpelloni, E.; Faccenna, C.; Spada, G.; Dong, D.; Williams, S. D.

    2013-12-01

    We use 2.5 to 14 years long position time-series from ~1000 continuous GPS stations to study vertical ground motions in the Euro-Mediterranean region and provide a first synoptic view of the vertical velocity field along the broad Nubia-Eurasia plate boundary. By estimating and removing common mode errors in position time-series from the results of a principal component analysis, we obtain a significant gain in the signal-to-noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index ~-0.7, we adopt a power-law + white noise stochastic model in estimating the final vertical rates, and find 95% of the velocities within ×2 mm/yr in the study area, with uncertainties from filtered time-series ~40% smaller than from the unfiltered ones. We evaluate the contribute of the glacial isostatic adjustment (GIA) signal to the vertical velocity budget using two different global models, characterized by distinct rheological layering of the Earth's mantle and different descriptions of the time-history of the mass of continental ice sheets since the Last Glacial Maximum. The analysis carried out allows us to highlight, for the first time, the presence of statistically significant, and spatially coherent, velocity gradients where a higher density of stations is available. We find undulations of the vertical velocity field occurring at different spatial scales both in regions characterized by tectonic activity, like eastern Alps, Apennines and eastern Mediterranean, and regions characterized by low to null tectonic activity, like central Iberia and western Alps. Correcting the observed velocities for GIA, although the two models used predict different GIA velocities and patterns, doesn't change significantly the velocity gradients. A correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area. GIA and weathering processes cannot completely explain the measured rates, and a combination of active tectonics and deep-seated geodynamic processes must be used to explain our observations. Excluding areas where more localized processes are likely, or where subduction/delamination processes may be active, mantle dynamics is the most likely process, but regional mantle modeling is required for a better understanding.

  1. On the propagation of a gravity current into a fluid with horizontal and vertical density gradient

    NASA Astrophysics Data System (ADS)

    Pham, Hieu; Sarkar, Sutanu

    2015-11-01

    Large-eddy simulations are used to investigate the dynamics of a rotating gravity current propagating in the ocean surface mixed layer on top of a pycnocline. Two simulations with different conditions in the surface mixed layer are performed: one with a homogenous mixed layer and one with a horizontal density gradient. In the latter case, the density in the mixed layer decreases with propagating distance. In both cases, a nonlinear bore forms at the front of the gravity current with Kelvin-Helmholtz billows that develop below and in the region behind the bore. In the case with a homogeneous mixed layer, the bore propagates at a constant speed which is proportional to √{g' H } where g' is the reduced gravity and H is the mixed layer depth. In the case with the horizontal gradient, the speed decreases in time. It is found that the horizontal density gradient influences the propagation of the bore in the following ways: (1) It reduces the buoyancy difference which drives the bore; (2) It generates a horizontal pressure gradient which drives a counter gravity current opposing the bore. The counter current creates a flow-converging zone ahead of the bore. The speed of the bore is found be dependent of the horizontal density gradient and the traveling distance of the bore.

  2. Freeze drying method

    DOEpatents

    Coppa, Nicholas V.; Stewart, Paul; Renzi, Ernesto

    1999-01-01

    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.

  3. Freeze drying apparatus

    DOEpatents

    Coppa, Nicholas V.; Stewart, Paul; Renzi, Ernesto

    2001-01-01

    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.

  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. 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.

  6. The photospheric vector magnetic field of a sunspot and its vertical gradient

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; West, E. A.; Tandberg-Hanssen, E.; Smith, J. E.; Henze, W., Jr.; Beckers, J. M.; Bruner, E. C.; Hyder, C. L.; Gurman, J. B.; Shine, R. A.

    1981-01-01

    The results of direct comparisons of photospheric and transition region line-of-sight field observations of sunspots using the SMM UV spectrometer and polarimeter are reported. The analysis accompanying the data is concentrated on demonstrating that the sunspot concentrated magnetic field extends into the transition region. An observation of a sunspot on Oct. 23, 1980 at the S 18 E 03 location is used as an example. Maximum field strengths ranged from 2030-2240 gauss for large and small umbrae viewed and inclination of the field to the line-of-sight was determined for the photosphere and transition region. The distribution of the magnetic field over the sunspot and variation of the line-of-sight gradient are discussed, as are the magnitudes and gradients of the photospheric field across the penumbral-photospheric boundaries.

  7. Estimation of the depth to the fresh-water/salt-water interface from vertical head gradients in wells in coastal and island aquifers

    USGS Publications Warehouse

    Izuka, S.K.; Gingerich, S.B.

    1998-01-01

    An accurate estimate of the depth to the theoretical interface between fresh, water and salt water is critical to estimates of well yields in coastal and island aquifers. The Ghyben-Herzberg relation, which is commonly used to estimate interface depth, can greatly underestimate or overestimate the fresh-water thickness, because it assumes no vertical head gradients and no vertical flow. Estimation of the interface depth needs to consider the vertical head gradients and aquifer anisotropy that may be present. This paper presents a method to calculate vertical head gradients using water-level measurements made during drilling of a partially penetrating well; the gradient is then used to estimate interface depth. Application of the method to a numerically simulated fresh-water/salt-water system shows that the method is most accurate when the gradient is measured in a deeply penetrating well. Even using a shallow well, the method more accurately estimates the interface position than does the Ghyben-Herzberg relation where substantial vertical head gradients exist. Application of the method to field data shows that drilling, collection methods of water-level data, and aquifer inhomogeneities can cause difficulties, but the effects of these difficulties can be minimized.

  8. Denitrification in nitrate-contaminated groundwater: Occurrence in steep vertical geochemical gradients

    NASA Astrophysics Data System (ADS)

    Smith, Richard L.; Howes, Brian L.; Duff, John H.

    1991-07-01

    A relatively narrow vertical zone (5-6 m thick) of NO 3- containing groundwater was identified using multilevel sampling devices in a sand and gravel aquifer on Cape Cod, MA, USA. The aquifer has been chronically contaminated by surface disposal of treated sewage 0.3 km upgradient from the study area. The NO 3- zone was anoxic and contained high concentrations of N 2O (16.5 ?M), suggesting that it was a zone of active denitrification. Denitrifying activity was confirmed with direct measurement using acetylene block incubations with aquifer core material; the peak rate was 2.4 nmol N reduced (g sed) -1 day -1. Concentrations of dissolved inorganic carbon and N 2 were close to atmospheric equilibrium in uncontaminated groundwater, but were more than 2 times higher within the contaminant plume. Excess CO 2 and N 2 suggested in situ formation with a stoichiometry of C and N mineralized via denitrification of 0.8 (C/N). Denitrification within the aquifer resulted in an increase in the natural ?15N of NO 3- (from +13.6 to +42.0%.) and the N 2 produced, with an isotopic enrichment factor, ?, of -13.9%.. Vertical profiles of NH 4+ and ?15N of NH 4+ indicated that dissimilatory reduction of NO 3- to NH 4+ was also occurring but mass balance calculations indicated that denitrification was the predominant process. These results demonstrate that a combination approach using field mass balance, stable isotope analysis, and laboratory incubations yields useful insight as to the significance of denitrification in aquifer sediments and that closely spaced vertical sampling is necessary to adequately quantify the processes controlling C and N transport and transformation within these environments.

  9. Meridional gradients in aerosol vertical distribution over Indian Mainland: Observations and model simulations

    NASA Astrophysics Data System (ADS)

    Prijith, S. S.; Suresh Babu, S.; Lakshmi, N. B.; Satheesh, S. K.; Krishna Moorthy, K.

    2016-01-01

    Multi-year observations from the network of ground-based observatories (ARFINET), established under the project 'Aerosol Radiative Forcing over India' (ARFI) of Indian Space Research Organization and space-borne lidar 'Cloud Aerosol Lidar with Orthogonal Polarization' (CALIOP) along with simulations from the chemical transport model 'Goddard Chemistry Aerosol Radiation and Transport' (GOCART), are used to characterize the vertical distribution of atmospheric aerosols over the Indian landmass and its spatial structure. While the vertical distribution of aerosol extinction showed higher values close to the surface followed by a gradual decrease at increasing altitudes, a strong meridional increase is observed in the vertical spread of aerosols across the Indian region in all seasons. It emerges that the strong thermal convections cause deepening of the atmospheric boundary layer, which although reduces the aerosol concentration at lower altitudes, enhances the concentration at higher elevations by pumping up more aerosols from below and also helping the lofted particles to reach higher levels in the atmosphere. Aerosol depolarization ratios derived from CALIPSO as well as the GOCART simulations indicate the dominance of mineral dust aerosols during spring and summer and anthropogenic aerosols in winter. During summer monsoon, though heavy rainfall associated with the Indian monsoon removes large amounts of aerosols, the prevailing southwesterly winds advect more marine aerosols over to landmass (from the adjoining oceans) leading to increase in aerosol loading at lower altitudes than in spring. During spring and summer months, aerosol loading is found to be significant, even at altitudes as high as 4 km, and this is proposed to have significant impacts on the regional climate systems such as Indian monsoon.

  10. Denitrification in nitrate-contaminated groundwater: Occurrence in steep vertical geochemical gradients

    USGS Publications Warehouse

    Smith, R.L.; Howes, B.L.; Duff, J.H.

    1991-01-01

    A relatively narrow vertical zone (5-6 m thick) of NO3- containing groundwater was identified using multilevel sampling devices in a sand and gravel aquifer on Cape Cod, MA, USA. The aquifer has been chronically contaminated by surface disposal of treated sewage 0.3 km upgradient from the study area. The NO3- zone was anoxic and contained high concentrations of N2O (16.5 ??M), suggesting that it was a zone of active denitrification. Denitrifying activity was confirmed with direct measurement using acetylene block incubations with aquifer core material; the peak rate was 2.4 nmol N reduced (g sed)-1 day-1. Concentrations of dissolved inorganic carbon and N2 were close to atmospheric equilibrium in uncontaminated groundwater, but were more than 2 times higher within the contaminant plume. Excess CO2 and N2 suggested in situ formation with a stoichiometry of C and N mineralized via denitrification of 0.8 (C/N). Denitrification within the aquifer resulted in an increase in the natural ??15N of NO3- (from +13.6 to +42.0%.) and the N2 produced, with an isotopic enrichment factor, ??{lunate}, of -13.9%.. Vertical profiles of NH4+ and ??15N of NH4+ indicated that dissimilatory reduction of NO3- to NH4+ was also occurring but mass balance calculations indicated that denitrification was the predominant process. These results demonstrate that a combination approach using field mass balance, stable isotope analysis, and laboratory incubations yields useful insight as to the significance of denitrification in aquifer sediments and that closely spaced vertical sampling is necessary to adequately quantify the processes controlling C and N transport and transformation within these environments. ?? 1991.

  11. FILIF Measurements of HCHO Vertical Gradients and Flux via Eddy Covariance during BEACHON-ROCS 2010

    NASA Astrophysics Data System (ADS)

    Digangi, J. P.; Boyle, E.; Henry, S. B.; Keutsch, F. N.; Beachon-Rocs Science Team

    2010-12-01

    Models of HOx chemistry in rural (low NOx) environments can drastically underpredict OH concentrations compared to measurements. In addition, models of OH reactivity based on modeled VOC emissions also underpredict OH reactivity. The combination of these facts implies a significant misunderstanding of HOx chemistry in rural environments. Formaldehyde (HCHO) is one of the most ubiquitous VOC oxidation products and therefore is an important tracer of VOC oxidation. Formaldehyde may be formed via the fast oxidation of biogenic VOCs (BVOCs), such as isoprene and terpenes emitted from forests, giving a measure of any potential missing VOCs as a cause of the inconsistency in OH reactivity. Also, as the loss pathways of HCHO are well understood, HCHO concentrations can provide further information about OH concentrations. As a result, measurements of HCHO gradients and fluxes in pristine forests can provide valuable insight into this rural HOx chemistry. We present the first reported measurements of HCHO flux via eddy covariance, as well as HCHO concentrations and gradients as observed by the Madison FIber Laser-Induced Fluorescence (FILIF) Instrument during the BEACHON-ROCS 2010 campaign in a rural coniferous forest northwest of Colorado Springs, CO. Midday upward HCHO fluxes as high as 150 μg/m2/hr were observed. These results will be discussed in the context of rapid in-canopy BVOC oxidation and the uncertainties in the HOx budget inside forest canopies.

  12. Variation in community structure across vertical intertidal stress gradients: how does it compare with horizontal variation at different scales?

    PubMed

    Valdivia, Nelson; Scrosati, Ricardo A; Molis, Markus; Knox, Amanda S

    2011-01-01

    In rocky intertidal habitats, the pronounced increase in environmental stress from low to high elevations greatly affects community structure, that is, the combined measure of species identity and their relative abundance. Recent studies have shown that ecological variation also occurs along the coastline at a variety of spatial scales. Little is known, however, on how vertical variation compares with horizontal variation measured at increasing spatial scales (in terms of sampling interval). Because broad-scale processes can generate geographical patterns in community structure, we tested the hypothesis that vertical ecological variation is higher than fine-scale horizontal variation but lower than broad-scale horizontal variation. To test this prediction, we compared the variation in community structure across intertidal elevations on rocky shores of Helgoland Island with independent estimates of horizontal variation measured at the scale of patches (quadrats separated by 10s of cm), sites (quadrats separated by a few m), and shores (quadrats separated by 100s to 1000s of m). The multivariate analyses done on community structure supported our prediction. Specifically, vertical variation was significantly higher than patch- and site-scale horizontal variation but lower than shore-scale horizontal variation. Similar patterns were found for the variation in abundance of foundation taxa such as Fucus spp. and Mastocarpus stellatus, suggesting that the effects of these canopy-forming algae, known to function as ecosystem engineers, may explain part of the observed variability in community structure. Our findings suggest that broad-scale processes affecting species performance increase ecological variability relative to the pervasive fine-scale patchiness already described for marine coasts and the well known variation caused by vertical stress gradients. Our results also indicate that experimental research aiming to understand community structure on marine shores should benefit from applying a multi-scale approach. PMID:21887371

  13. Variation in Community Structure across Vertical Intertidal Stress Gradients: How Does It Compare with Horizontal Variation at Different Scales?

    PubMed Central

    Valdivia, Nelson; Scrosati, Ricardo A.; Molis, Markus; Knox, Amanda S.

    2011-01-01

    In rocky intertidal habitats, the pronounced increase in environmental stress from low to high elevations greatly affects community structure, that is, the combined measure of species identity and their relative abundance. Recent studies have shown that ecological variation also occurs along the coastline at a variety of spatial scales. Little is known, however, on how vertical variation compares with horizontal variation measured at increasing spatial scales (in terms of sampling interval). Because broad-scale processes can generate geographical patterns in community structure, we tested the hypothesis that vertical ecological variation is higher than fine-scale horizontal variation but lower than broad-scale horizontal variation. To test this prediction, we compared the variation in community structure across intertidal elevations on rocky shores of Helgoland Island with independent estimates of horizontal variation measured at the scale of patches (quadrats separated by 10s of cm), sites (quadrats separated by a few m), and shores (quadrats separated by 100s to 1000s of m). The multivariate analyses done on community structure supported our prediction. Specifically, vertical variation was significantly higher than patch- and site-scale horizontal variation but lower than shore-scale horizontal variation. Similar patterns were found for the variation in abundance of foundation taxa such as Fucus spp. and Mastocarpus stellatus, suggesting that the effects of these canopy-forming algae, known to function as ecosystem engineers, may explain part of the observed variability in community structure. Our findings suggest that broad-scale processes affecting species performance increase ecological variability relative to the pervasive fine-scale patchiness already described for marine coasts and the well known variation caused by vertical stress gradients. Our results also indicate that experimental research aiming to understand community structure on marine shores should benefit from applying a multi-scale approach. PMID:21887371

  14. Transient buoyancy-driven flow in a vertical cylindrical enclosure with wavy-sidewall due to thermal and concentration gradients

    NASA Astrophysics Data System (ADS)

    Sanchez, Fausto; Martinez, Simon; Ramirez, Hugo; Medina, Abraham

    2010-11-01

    An axisymmetric transient convection flow, due to thermal and concentration gradients within a vertical cylindrical enclosure with adiabatic wavy sidewall, was studied. The two important cases of enclosure heated from below and heated from the top were studied. An analytical coordinate transformation was used to change the computation domain into a square. The heat and mass transfer were analyzed using non-dimensional parameters which include the cavity aspect ratio, the dimensionless wavelength and amplitude of the wavy-wall, Rayleigh and Prandtl numbers and the buoyancy ratio. For all cases the upper surface is consider as the one with high concentration, while the others are impermeable. Numerical results using a streamfunction formulation were developed. Heatlines and mass lines were used to illustrate the transport phenomena. Average Nusselt and Sherwood numbers were evaluated while the convection patterns arise within the cavity. The wavy-wall was found to promote thermal stratification and low velocity multiple cell patterns for low buoyancy ratio.

  15. Feeding and distribution of zooplankton in the desalinated ``lens'' in the Kara Sea: Impact of the vertical salinity gradient

    NASA Astrophysics Data System (ADS)

    Pasternak, A. F.; Drits, A. V.; Abyzova, G. A.; Semenova, T. N.; Sergeeva, V. M.; Flint, M. V.

    2015-11-01

    The feeding rates and distribution of dominant zooplankton in the area of the Kara Sea "lens" (upper desalinated layer) were studied in August 2014. Zooplankton abundance was low along the transect across the center of the lens but noticeably increased at the margin of the lens. Calanus glacialis, C. finmarchicus, Oithona similis, and Pseudocalanus spp. dominated among zooplankton, constituting 60-80% of the total biomass. Within the lens area, chlorophyll peaked at a depth of about 10 m, whereas zooplankton was distributed deeper than 30 m, and no diel vertical migrations were recorded. Outside the lens, zooplankton was distributed in the upper mixed layer. Specific daily rations on phytoplankton within the lens area were considerably higher than outside (5-50 and 0.2-6%, respectively). We hypothesized that accumulation of the suspended matter over a sharp density (salinity) gradient contributes to an increase in daily rations. A significant positive correlation between the values of daily ration and salinity gradients was obtained. The grazing impact of zooplankton on the primary production and the phytoplankton biomass was maximum (94 and 8%) at the lens margin, which was due to the combination of high values of zooplankton abundance and daily rations.

  16. Active bacterial community structure along vertical redox gradients in Baltic Sea sediment

    SciTech Connect

    Jansson, Janet; Edlund, Anna; Hardeman, Fredrik; Jansson, Janet K.; Sjoling, Sara

    2008-05-15

    Community structures of active bacterial populations were investigated along a vertical redox profile in coastal Baltic Sea sediments by terminal-restriction fragment length polymorphism (T-RFLP) and clone library analysis. According to correspondence analysis of T-RFLP results and sequencing of cloned 16S rRNA genes, the microbial community structures at three redox depths (179 mV, -64 mV and -337 mV) differed significantly. The bacterial communities in the community DNA differed from those in bromodeoxyuridine (BrdU)-labeled DNA, indicating that the growing members of the community that incorporated BrdU were not necessarily the most dominant members. The structures of the actively growing bacterial communities were most strongly correlated to organic carbon followed by total nitrogen and redox potentials. Bacterial identification by sequencing of 16S rRNA genes from clones of BrdU-labeled DNA and DNA from reverse transcription PCR (rt-PCR) showed that bacterial taxa involved in nitrogen and sulfur cycling were metabolically active along the redox profiles. Several sequences had low similarities to previously detected sequences indicating that novel lineages of bacteria are present in Baltic Sea sediments. Also, a high number of different 16S rRNA gene sequences representing different phyla were detected at all sampling depths.

  17. Measurement of the vertical gradient of the semidiurnal tidal wind phase in winter at the 95 km level

    NASA Astrophysics Data System (ADS)

    Schminder, R.; Kurschner, D.

    1984-05-01

    When supplemented by absolute reflection height measurements, low frequency wind measurements in the 90-100 km height range become truly competitive in comparison with the more widely used radar meteor wind observations. For example, height profiles of the wind parameters in the so-called meteor zone can be obtained due to the considerable interdiurnal variability of the average nighttime reflection heights controlled by geomagnetic activity. The phase of the semidiurnal tidal wind is particularly height-dependent. The measured vertical gradient of 1/4 h/km in winter corresponds to a vertical wavelength of about 50 km. Wind measurements in the upper atmosphere, at heights between 90 and 100 km, were carried out at the Collm Geophysical Observatory of Karl Marx University Leipzig for a number of years. These measurements use the closely-spaced receiver method and three measuring paths, on 179, 227, and 272 kHz. They take place every day between sunset and sunrise, i.e., nightly. A night in this sense may last as long as 18 hours in winter. Both the measurements and their evaluation are completely automatic, and the prevailing winds and tides are separated.

  18. Measurement of the Vertical Gradient of the Semidiurnal Tidal Wind Phase in Winter at the 95 Km Level

    NASA Technical Reports Server (NTRS)

    Schminder, R.; Kurschner, D.

    1984-01-01

    When supplemented by absolute reflection height measurements, low frequency wind measurements in the 90-100 km height range become truly competitive in comparison with the more widely used radar meteor wind observations. For example, height profiles of the wind parameters in the so-called meteor zone can be obtained due to the considerable interdiurnal variability of the average nighttime reflection heights controlled by geomagnetic activity. The phase of the semidiurnal tidal wind is particularly height-dependent. The measured vertical gradient of 1/4 h/km in winter corresponds to a vertical wavelength of about 50 km. Wind measurements in the upper atmosphere, at heights between 90 and 100 km, were carried out at the Collm Geophysical Observatory of Karl Marx University Leipzig for a number of years. These measurements use the closely-spaced receiver method and three measuring paths, on 179, 227, and 272 kHz. They take place every day between sunset and sunrise, i.e., nightly. A night in this sense may last as long as 18 hours in winter. Both the measurements and their evaluation are completely automatic, and the prevailing winds and tides are separated.

  19. Observations of BVOC (Biogenic Volatile Organic Compound) Fluxes and Vertical Gradients in a Ponderosa Pine Forest during BEARPEX 2009

    NASA Astrophysics Data System (ADS)

    Park, J.; Fares, S.; Weber, R.; Goldstein, A.

    2010-12-01

    During summer 2009 an intensive field campaign (Biosphere Effects on AeRosols and Photochemistry EXperiment - BEARPEX) took place in Blodgett Forest, a Ponderosa pine forest in the Sierra Nevada Mountains of California. The campaign aimed to investigate biosphere-atmosphere interactions during a period of intense photochemical activity, to elucidate the fate BVOC (Biogenic Volatile Organic Compounds) in the atmosphere, and explore the processes of secondary organic aerosol formation. In this study, a PTR-MS (Proton Transfer Reaction - Mass Spectrometry) was used to measure 19 compounds (masses) including methanol, isoprene + MBO (2-Methyl-3-butene-2-ol), monoterpenes, sesquiterpenes, and some oxygenated BVOCs at 5 heights of a vertical gradient from the forest floor to above the canopy. Fluxes of the 4 dominant BVOCs were measured above the canopy with the Eddy covariance technique. In parallel with BVOC measurements, ozone fluxes and gradients, and meteorological parameters (PAR, temperature, relative humidity, wind speed, and wind direction) were recorded in order to investigate the dependence of BVOC emissions and chemistry on meteorological conditions and to test the hypothesis that BVOC remove atmospheric ozone through gas-phase reactions. BVOCs which are directly emitted from pine trees generally have the highest concentration at the lowest measurement height and the lowest concentration above the canopy. Sesquiterpenes were observed at lower concentration than monoterpenes, but with very similar vertical gradient patterns, indicating their emission patterns are similar. The observed MBO flux was approximately twice the Monoterpene flux. Measured monoterpene canopy scale flux was consistent with modeled emissions based on scaling up from branch enclosure measurements at this site (basal emission rate F30= 0.61 ±0.14 mgC m-2 hr-1 and temperature response β= 0.15 ±0.09 °C-1). We find that m/z 113, an unidentified OVOCs (oxygenated volatile organic compounds), is clearly produced by both isoprene and terpene oxidation, arriving in air advected to the site from the west indicative of the oxidation of isoprene released by oak trees ~30 km downhill, and also produced from local terpene oxidation and deposited in the pine forest canopy.

  20. Comparison of model-derived and radar-observed freezing-level heights: Implications for vertical reflectivity profile-correction schemes

    NASA Astrophysics Data System (ADS)

    Mittermaier, Marion P.; Illingworth, Anthony J.

    2003-01-01

    In the current operational Met Office scheme for deriving rainfall rates from radar, the height of the enhanced radar return associated with melting snow, the bright band, is determined using the height of the 0 °C isotherm obtained from the Met Office Unified Mesoscale Model (UM) forecast. In this paper the potential errors of using model forecast heights as input to the bright-band correction scheme are investigated. The UM and European Centre for Medium-Range Weather Forecasts (ECMWF) model forecasts of wet-bulb 0 °C isotherm heights (WBZ) are compared with the height of the 'step' increase in reflectivity in the vertical profiles recorded by the vertically pointing 94 GHz Galileo cloud radar at Chilbolton. High-frequency radars do not measure an enhanced 'bright band' at the melting layer, rather a sudden increase of reflectivity as the ice particles become coated in water. This sudden step can be used to locate accurately the height of the WBZ. Results show that the UM predicts the WBZ height with a root-mean-square error of 147 m and a bias of 15 m. This is within the worst-case tolerance of 200 m of the operational bright-band correction scheme. Factors that may influence the accuracy are the presence of deep isothermal layers and timing errors concerning the passage of fronts, but these are found not to be serious. An investigation into the deterioration of the UM 36-hour forecast shows that half the error is introduced at the initialization time, highlighting the fact that further improvements can be achieved through a better definition of the initial state of the atmosphere. The ECMWF forecast is for a longer lead time, but comparison for the same lead-time errors as the UM shows that the performance of the two models is comparable. An alternative approach is to derive the bright-band height from volumetric radar scans at different elevations. This study suggests that, at least in the UK, operational model predictions of the freezing-level height are within the specified 200 m error, but that the use of volumetric scans, even under idealized conditions, cannot achieve this accuracy.

  1. 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.

  2. The Effect of Pre-Impact Porosity and Vertical Density Gradients on the Gravity Signature of Lunar Craters

    NASA Astrophysics Data System (ADS)

    Milbury, Colleen; Johnson, Brandon C.; Melosh, H. Jay; Collins, Gareth S.; Blair, David M.; Soderblom, Jason M.; Nimmo, Francis; Phillips, Roger J.; Bierson, Carver J.; Zuber, Maria T.

    2015-11-01

    As a result of NASA’s dual spacecraft Gravity Recovery And Interior Laboratory (GRAIL) mission [Zuber et al., 2013; doi:10.1126/science.1231507], we now know that the lunar crust is highly porous and that the porosity varies laterally [Wieczorek et al., 2013; doi:10.1126/science.1231530] and vertically [Besserer et al., 2014; doi:10.1002/2014GL060240]. Analysis of complex craters located within the lunar highlands reveals that: 1) craters larger than diameter D~210 have positive Bouguer Anomalies (BAs), 2) craters with D ≲ 100 km have both positive and negative BAs that vary about the (near 0) mean by approximately ± 25 mGal, and, 3) D and BA are anticorrelated for craters with D ≲ 100 km [Soderblom et al., 2015; doi:10.1002/2015GL065022]. Numerical modeling by Milbury et al. [2015, LPSC] shows that pre-impact porosity is the dominant influence on the gravity signature of complex craters with D ≲ 100 km, and mantle uplift dominates the gravity for those with D > 140 km. Phillips et al. [2015, LPSC] showed that complex craters located in the South Pole-Aitken (SPA) basin tend to have more-negative BAs than similar craters in the highlands. We use the iSALE hydrocode including pore space compaction [Wünnemann et al., 2006; doi:10.1016/j.icarus.2005.10.013] and dilatant bulking [Collins, 2014; doi:10.1002/2014JE004708] to understand how the gravity signature of impact craters develop. In this study we vary crustal porosity with depth. We find that simulations that have constant porosity with depth have a lower BA for a given crater diameter than those with the same mean porosity, but that vary with depth. We used two different mean porosities (7% and 14%) and found that the BA increases with increasing porosity, similar to simulations with constant porosity. We reproduce the observed anticorrelation between BA and D for D ≲ 100 km only for simulations where the pre-impact porosity is zero or low. Our results support the observation that SPA has lower overall porosity, but higher vertical gradients, giving craters within SPA more-negative BAs than those within the highlands crust. These simulations demonstrate that the BA and porosities reported here are valid for determining general trends only.

  3. [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

  4. [FeFe]-hydrogenase abundance and diversity along a vertical redox gradient in Great Salt Lake, USA.

    PubMed

    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

  5. Estimation of the depth to the fresh-water/salt-water interface from vertical head gradients in wells in coastal and island aquifers

    NASA Astrophysics Data System (ADS)

    Izuka, Scot K.; Gingerich, Stephen B.

    An accurate estimate of the depth to the theoretical interface between fresh, water and salt water is critical to estimates of well yields in coastal and island aquifers. The Ghyben-Herzberg relation, which is commonly used to estimate interface depth, can greatly underestimate or overestimate the fresh-water thickness, because it assumes no vertical head gradients and no vertical flow. Estimation of the interface depth needs to consider the vertical head gradients and aquifer anisotropy that may be present. This paper presents a method to calculate vertical head gradients using water-level measurements made during drilling of a partially penetrating well; the gradient is then used to estimate interface depth. Application of the method to a numerically simulated fresh-water/salt-water system shows that the method is most accurate when the gradient is measured in a deeply penetrating well. Even using a shallow well, the method more accurately estimates the interface position than does the Ghyben-Herzberg relation where substantial vertical head gradients exist. Application of the method to field data shows that drilling, collection methods of water-level data, and aquifer inhomogeneities can cause difficulties, but the effects of these difficulties can be minimized. Résumé Une estimation précise de la profondeur de l'interface théorique entre l'eau douce et l'eau salée est un élément critique dans les estimations de rendement des puits dans les aquifères insulaires et littoraux. La relation de Ghyben-Herzberg, qui est habituellement utilisée pour estimer la profondeur de cette interface, peut fortement sous-estimer ou surestimer l'épaisseur de l'eau douce, parce qu'elle suppose l'absence de gradient vertical de charge et d'écoulement vertical. L'estimation de la profondeur de l'interface requiert de prendre en considération les gradients verticaux de charge et l'éventuelle anisotropie de l'aquifère. Cet article propose une méthode de calcul des gradients verticaux de charge à partir des mesures de niveau piézométrique faites en cours de foration d'un puits incomplet; le gradient est alors utilisé pour estimer la profondeur de l'interface. L'application de cette méthode à un système eau douce - eau salée simulé numériquement montre que la méthode est la plus précise lorsque le gradient est mesuré dans un puits pénétrant profondément dans l'aquifère. Même en utilisant un puits peu profond, la méthode estime la position de l'interface avec plus de précision que ne le fait la relation de Ghyben-Herzberg lorsqu'il existe un gradient vertical de charge bien marqué. L'application de la méthode à des données de terrain montre que la foration, les méthodes de mesure de niveau et les hétérogénéités au sein de l'aquifère peuvent être la cause de difficultés, mais que les effets de ces difficultés peuvent être réduits. Resumen Para la estimación de la productividad de pozos en acuíferos costeros y en islas es necesaria una estimación precisa de la profundidad de la interfaz teórica entre agua dulce y agua salada. La relación de Ghyben-Herzberg, usada habitualmente para estimar la profundidad de la interfaz, puede subestimar o sobrestimar el espesor de agua dulce, al asumir la ausencia de flujos y gradientes verticales. La estimación de la profundidad de la interfaz debe considerar tanto estos gradientes verticales, como la posible anisotropía del acuífero. En este artículo se presenta un método para calcular los gradientes verticales de niveles a partir de las medidas obtenidas durante la perforación de un pozo parcialmente penetrante para, a partir de este gradiente, estimar la profundidad de la interfaz. La aplicación del método a un sistema de agua dulce/agua salada simulado numéricamente muestra que el método es más preciso cuando el gradiente se mide en un pozo profundo. Incluso en el caso de un pozo superficial, el método permite una estimación más precisa de la profundidad de la interfaz que la aplicación de la fórmula de Ghyben-Herzberg, en los casos en los que existen gradientes verticales significativos. La aplicación del método a datos reales muestra que la perforación, la recogida de datos de niveles y la heterogeneidad en el acuífero pueden causar dificultades en la aplicación del método, pero que estas pueden minimizarse.

  6. Highly Efficient Organic Solar Cells with Improved Vertical Donor-Acceptor Compositional Gradient Via an Inverted Off-Center Spinning Method.

    PubMed

    Huang, Jiang; Carpenter, Joshua H; Li, Chang-Zhi; Yu, Jun-Sheng; Ade, Harald; Jen, Alex K-Y

    2016-02-01

    A novel, yet simple solution fabrication technique to address the trade-off between photocurrent and fill factor in thick bulk heterojunction organic solar cells is described. The inverted off-center spinning technique promotes a vertical gradient of the donor-acceptor phase-separated morphology, enabling devices with near 100% internal quantum efficiency and a high power conversion efficiency of 10.95%. PMID:26628195

  7. In situ modulation of the vertical distribution in a blend of P3HT and PC60BM via the addition of a composition gradient inducer

    NASA Astrophysics Data System (ADS)

    Moon, Byung Joon; Lee, Gang-Young; Im, Min Jeong; Song, Seulki; Park, Taiho

    2014-01-01

    2,2,3,3,4,4,4-Heptafluoro-N-phenyl-butyr-amide (F-ADD) was synthesized and shown to induce a composition gradient in a blend of P3HT and PC60BM. The addition of small amounts (ca. 0.5 wt%) of F-ADD modulated the chemical distribution in the blend along the vertical direction by controlling the blend component interface energy through selective interactions between F-ADD and PC60BM. A homogeneous compositional distribution along the vertical direction in the nanostructured bulk heterojunction (BHJ) increased the interfacial area, which shortened the exciton path length to the donor-acceptor interface and improved the photovoltaic performance.2,2,3,3,4,4,4-Heptafluoro-N-phenyl-butyr-amide (F-ADD) was synthesized and shown to induce a composition gradient in a blend of P3HT and PC60BM. The addition of small amounts (ca. 0.5 wt%) of F-ADD modulated the chemical distribution in the blend along the vertical direction by controlling the blend component interface energy through selective interactions between F-ADD and PC60BM. A homogeneous compositional distribution along the vertical direction in the nanostructured bulk heterojunction (BHJ) increased the interfacial area, which shortened the exciton path length to the donor-acceptor interface and improved the photovoltaic performance. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05312a

  8. 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 (θv). Average θv was inversely related to bulk root water potential (Ψ(root)). In turn, Ψ(root) was correlated with both average [ABA](root) and [RX-ABA](sap). Despite large gradients in θv, [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

  9. In situ modulation of the vertical distribution in a blend of P3HT and PC(60)BM via the addition of a composition gradient inducer.

    PubMed

    Moon, Byung Joon; Lee, Gang-Young; Im, Min Jeong; Song, Seulki; Park, Taiho

    2014-02-21

    2,2,3,3,4,4,4-Heptafluoro-N-phenyl-butyr-amide (F-ADD) was synthesized and shown to induce a composition gradient in a blend of P3HT and PC60BM. The addition of small amounts (ca. 0.5 wt%) of F-ADD modulated the chemical distribution in the blend along the vertical direction by controlling the blend component interface energy through selective interactions between F-ADD and PC60BM. A homogeneous compositional distribution along the vertical direction in the nanostructured bulk heterojunction (BHJ) increased the interfacial area, which shortened the exciton path length to the donor-acceptor interface and improved the photovoltaic performance. PMID:24441576

  10. Acclimation of Leaf Nitrogen to Vertical Light Gradient at Anthesis in Wheat Is a Whole-Plant Process That Scales with the Size of the Canopy1[W][OA

    PubMed Central

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

    2012-01-01

    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

  11. When hot water freezes before cold

    NASA Astrophysics Data System (ADS)

    Katz, J. I.

    2009-01-01

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

  12. The effects of vertical gradient of disparity and combination mode of features on the occurrence of double fusion in Panum's limiting case.

    PubMed

    Li, Huayun; Xie, Ying; Li, Shengming; Xie, Shuiqing; Gao, Chuang; Yang, Zhongle

    2012-01-01

    Panum's limiting case generally refers to the phenomenon that two features presented to one eye and a single feature presented to the other are combined and then perceived as two features at different depths. It is still not clear why experimental results derived from the Panum-type configuration (all lines parallel) support a double fusion viewpoint, but they do not for the Wheatstone-type configuration (one line not parallel to the others). Some experimental results support the double fusion theory, while others do not, even under a small disparity. Here we report that, under a small disparity, when the vertical gradients of the horizontal disparity ofdichoptic feature pairs in previous Wheatstone-type configurations were increased or decreased, the evidence which was considered to be very convincing in previous studies, either supporting or against the double fusion viewpoint, was challenged, and even turned to support the opposite view. Moreover, it was discovered that changes in the way features were arranged altered the results. Together, these results indicate that double fusion is the common basis for all kinds of Panum-type configurations. But for the Wheatstone-type configurations double fusion is also constrained by the vertical gradient of disparity of the configurations in addition to disparity and influenced by the degree of similarity/conflict between binocular cues and monocular cues resulting from different arrangements of features. PMID:23513617

  13. Large vertical δ13CDIC gradients in Early Triassic seas of the South China craton: Implications for oceanographic changes related to Siberian Traps volcanism

    NASA Astrophysics Data System (ADS)

    Song, Huyue; Tong, Jinnan; Algeo, Thomas J.; Horacek, Micha; Qiu, Haiou; Song, Haijun; Tian, Li; Chen, Zhong-Qiang

    2013-06-01

    Vertical gradients in the δ13C of seawater dissolved inorganic carbon (Δδ13CDIC) can be estimated for paleomarine systems based on δ13Ccarb data from sections representing a range of depositional water depths. An analysis of eight Lower Triassic sections from the northern Yangtze Platform and Nanpanjiang Basin, representing water depths of ~ 50 to 500 m, allowed reconstruction of Δδ13CDIC in Early Triassic seas of the South China craton for seven time slices representing four negative (N) and three positive (P) carbon-isotope excursions: 8.5‰ (N1), 5.8‰ (P1), 3.5‰ (N2), 6.5‰ (P2), 7.8‰ (N3), - 1.9‰ (P3), and 2.2‰ (N4). These values are much larger than vertical δ13CDIC gradients in the modern ocean (~ 1-3‰) due to intensified stratification and reduced vertical mixing in Early Triassic seas. Peaks in Δδ13CDIC around the PTB (N1) and in the early to mid-Smithian (P2-N3) coincided with episodes of strong climatic warming, reduced marine productivity, and expanded ocean anoxia. The Dienerian-Smithian boundary marks the onset of a major mid-Early Triassic disturbance, commencing ~ 1 Myr after the latest Permian mass extinction, that we link to a second eruptive stage of the Siberian Traps. Inhospitable oceanic conditions generally persisted until the early Spathian, when strong climatic cooling caused re-invigoration of global-ocean circulation, leading to an interval of negative Δδ13CDIC values and a sharp increase in δ13Ccarb driven by upwelling of nutrient-rich deepwaters. These developments marked the end of the main eruptive stage of the Siberian Traps.

  14. Lagrangian Stochastic Modelling of Dispersion in the Convective Boundary Layer with Skewed Turbulence Conditions and a Vertical Density Gradient: Formulation and Implementation in the FLEXPART Model

    NASA Astrophysics Data System (ADS)

    Cassiani, Massimo; Stohl, Andreas; Brioude, Jerome

    2015-03-01

    A correction for the vertical gradient of air density has been incorporated into a skewed probability density function formulation for turbulence in the convective boundary layer. The related drift term for Lagrangian stochastic dispersion modelling has been derived based on the well-mixed condition. Furthermore, the formulation has been extended to include unsteady turbulence statistics and the related additional component of the drift term obtained. These formulations are an extension of the drift formulation reported by Luhar et al. (Atmos Environ 30:1407-1418, 1996) following the well-mixed condition proposed by Thomson (J Fluid Mech 180:529-556, 1987). Comprehensive tests were carried out to validate the formulations including consistency between forward and backward simulations and preservation of a well-mixed state with unsteady conditions. The stationary state CBL drift term with density correction was incorporated into the FLEXPART and FLEXPART-WRF Lagrangian models, and included the use of an ad hoc transition function that modulates the third moment of the vertical velocity based on stability parameters. Due to the current implementation of the FLEXPART models, only a steady-state horizontally homogeneous drift term could be included. To avoid numerical instability, in the presence of non-stationary and horizontally inhomogeneous conditions, a re-initialization procedure for particle velocity was used. The criteria for re-initialization and resulting errors were assessed for the case of non-stationary conditions by comparing a reference numerical solution in simplified unsteady conditions, obtained using the non-stationary drift term, and a solution based on the steady drift with re-initialization. Two examples of "real-world" numerical simulations were performed under different convective conditions to demonstrate the effect of the vertical gradient in density on the particle dispersion in the CBL.

  15. Eddy covariance fluxes and vertical concentration gradient measurements of NO and NO2 over a ponderosa pine ecosystem: observational evidence for within canopy removal of NOx

    NASA Astrophysics Data System (ADS)

    Min, K.-E.; Pusede, S. E.; Browne, E. C.; LaFranchi, B. W.; Wooldridge, P. J.; Cohen, R. C.

    2013-05-01

    Exchange of NOx (NO+NO2) between the atmosphere and biosphere is important for air quality, climate change, and ecosystem nutrient dynamics. There are few direct ecosystem scale measurements of the direction and rate of atmosphere-biosphere exchange of NOx. As a result, a complete description of the processes affecting NOx following emission from soils and/or plants as they transit from within the plant/forest canopy to the free atmosphere remains poorly constrained and debated. Here, we describe measurements of NO and NO2 fluxes and vertical concentration gradients made during the Biosphere Effects on AeRosols and Photochemistry EXperiment 2009. In general, during daytime we observe upward fluxes of NO and NO2 with counter-gradient fluxes of NO. We find that NOx fluxes from the forest canopy are smaller than calculated using observed flux-gradient relationships for conserved tracers and also smaller than measured soil NO emissions. We interpret these differences as evidence for the existence of a "canopy reduction factor". We suggest that at this site it is primarily due to chemistry converting NOx to higher nitrogen oxides within the forest canopy.

  16. Eddy covariance fluxes and vertical concentration gradient measurements of NO and NO2 over a ponderosa pine ecosystem: observational evidence for within-canopy chemical removal of NOx

    NASA Astrophysics Data System (ADS)

    Min, K.-E.; Pusede, S. E.; Browne, E. C.; LaFranchi, B. W.; Cohen, R. C.

    2014-06-01

    Exchange of NOx (NO+NO2) between the atmosphere and biosphere is important for air quality, climate change, and ecosystem nutrient dynamics. There are few direct ecosystem-scale measurements of the direction and rate of atmosphere-biosphere exchange of NOx. As a result, a complete description of the processes affecting NOx following emission from soils and/or plants as they transit from within the plant/forest canopy to the free atmosphere remains poorly constrained and debated. Here, we describe measurements of NO and NO2 fluxes and vertical concentration gradients made during the Biosphere Effects on AeRosols and Photochemistry EXperiment 2009. In general, during daytime we observe upward fluxes of NO and NO2 with counter-gradient fluxes of NO. We find that NOx fluxes from the forest canopy are smaller than calculated using observed flux-gradient relationships for conserved tracers and also smaller than measured soil NO emissions. We interpret these differences as primarily due to chemistry converting NOx to higher nitrogen oxides within the forest canopy, which might be part of a mechanistic explanation for the "canopy reduction factor" applied to soil NOx emissions in large-scale models.

  17. 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

  18. Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching.

    PubMed

    Otte, M A; Solis-Tinoco, V; Prieto, P; Borrisé, X; Lechuga, L M; González, M U; Sepulveda, B

    2015-09-01

    In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics. PMID:26033973

  19. 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

  20. 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 (δ13C) 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 δ13C from the Atlantic Ocean have revealed the development of a sharp vertical δ13C gradient between 2300-2500m water depth during successive glacial periods throughout the Late Quaternary, with extremely negative δ13C 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 δ13C values originated in the Southern Ocean. However the mechanisms behind the formation of this gradient and extreme δ13C 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 δ13C 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 δ13C 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 δ13C is restricted to the Atlantic Sector of the Southern Ocean, with increasingly positive δ13C values found in the Southwest Pacific and the south-eastern Pacific sector of the Southern Ocean. This implies that the δ13C 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 δ13C deep waters or increased vertical mixing in the Indian and Pacific sectors of the glacial Southern Ocean.

  1. Field-Testing the Suitability of Microrain Radars to Describe the Spatial Gradients of the Vertical Structure of Rainfall in Mountainous Regions

    NASA Astrophysics Data System (ADS)

    Prat, O. P.; Barros, A. P.

    2009-04-01

    A Micro Rain Radar (MRR) was deployed twice in July/August and October/November 2008 for a total duration of three months at the top of a mountain ridge in the Great Smoky Mountains National Park in the Southern Appalachians. For the second period of observation, a second MRR was deployed at a lower altitude in a nearby valley. Observations from rain gauges and the MRR were used along with a microphysical model to simulate the rainfall events observed during the radar deployment. Results from an integrated analysis of the observations are presented here, with emphasis on characterizing the diurnal cycle of rainfall and ridge-valley gradients in vertical structure of rainfall with an emphasis on microphysical properties.

  2. Changes in hydrocarbon groups, soil ecotoxicity and microbiology along horizontal and vertical contamination gradients in an old landfarming field for oil refinery waste.

    PubMed

    Mikkonen, Anu; Hakala, Kati P; Lappi, Kaisa; Kondo, Elina; Vaalama, Anu; Suominen, Leena

    2012-03-01

    Horizontal and vertical contaminant gradients in an old landfarming field for oil refinery waste were characterised with the aim to assess parallel changes in hydrocarbon groups and general, microbiological and ecotoxicological soil characteristics. In the surface soil polar compounds were the most prevalent fraction of heptane-extractable hydrocarbons, superseding GC-FID-resolvable and high-molar-mass aliphatics and aromatics, but there was no indication of their relatively higher mobility or toxicity. The size of the polar fraction correlated poorly with soil physical, chemical and microbiological properties, which were better explained by the total heptane-extractable and total petroleum hydrocarbons (TPH). Deleterious effects on soil microbiology in situ were observed at surprisingly low TPH concentrations (0.3%). Due to the accumulation of polar and complexed degradation products, TPH seems an insufficient measure to assess the quality and monitor the remediation of soil with weathered hydrocarbon contamination. PMID:22243888

  3. Formulation of a Lagrangian stochastic model of dispersion in the convective boundary layer with skewed turbulence conditions and vertical density gradient

    NASA Astrophysics Data System (ADS)

    cassiani, massimo; stohl, andreas; brioude, jerome

    2014-05-01

    The vertical gradient of air density has been included in a skewed probability density function formulation for turbulence in the convective boundary layer and the related drift term for Lagrangian stochastic particle modelling has been obtained based on the well-mixed condition. The formulation has been extended to include unsteady turbulence statistics. Tests were carried out to validate the model including consistency between forward and backward simulations and preservation of well-mixed state with unsteady conditions. The stationary state CBL drift term with density correction was incorporated in the FLEXPART/FLEXPART-WRF Lagrangian models. Currently only the steady state horizontally homogeneous drift term were included. To avoid numerical instability, using the steady homogenous drift in the presence of non-stationary and horizontally non-homogeneous conditions, a re-initialization procedure for particle velocity was used. The criteria for re-initialization and resulting errors were assessed.

  4. Freeze Technology for Nuclear Applications - 13590

    SciTech Connect

    Rostmark, Susanne C.; Knutsson, Sven; Lindberg, Maria

    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)

  5. 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 Δδ13C 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 Δδ13C can be influenced by changes in the whole ocean inventory of δ13C, 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 Δδ13C from the biological signal could certainly arise due to δ13C 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 δ13C. 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 (ΔCdsw) over the past 150,000 years. Comparison of ΔCdsw to Δδ13C from the same samples from core MD02-2588 in the Southern Ocean indicate a very similar downcore variability which supports the use of the Δδ13C method to reconstruct the biological pump during the MPT.

  6. New freeze pipe systems for nitrogen freezing

    NASA Astrophysics Data System (ADS)

    Rephan, D.

    A number of field and laboratory experiments have been carried out using new kinds of freezing pipe systems. These systems particularly enable freezing to be performed in stages. They further enable liquid gas consumption to be minimized. One system is particularly suitable for shaft freezing while another lends itself to tunnelling.

  7. Vertical gradient solution growth of N-type Si0.73Ge0.27 bulk crystals with homogeneous composition and its thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Omprakash, M.; Arivanandhan, M.; Sabarinathan, M.; Koyama, T.; Momose, Y.; Ikeda, H.; Tatsuoka, H.; Aswal, D. K.; Bhattacharya, S.; Inatomi, Y.; Hayakawa, Y.

    2016-05-01

    Compositionally homogeneous Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 bulk crystals were grown by a vertical gradient solution growth method. The sandwich sample Si (seed)/Sb-doped Ge/ Si(feed) was set up inside a furnace under a mild temperature gradient 0.57 °C/mm for homogeneous growth. The Si composition was analyzed by electron probe micro- analysis (EPMA). It revealed that the Si composition was homogeneous and the lengths of the Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 bulk crystals were 18.3 and 15.1 mm, respectively. Grain distribution was investigated by electron backscattered diffraction spectrum (EBSD). The Seebeck coefficients (-440 and -426 μV/K) of Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 were higher than the reported value (-211 μV/K) of P-doped (5×1019 cm-3) Si0.8Ge0.2 at room temperature. Thermal conductivity of Ga and Sb-doped SiGe was decreased with temperature due to scattering of phonon at the temperature range between 313 and 913 K. The maximum ZT values of Ga and Sb-doped SiGe were 0.34 and 0.44 at 820 K, respectively. The ZT values of Ga and Sb-doped SiGe were higher (0.07 and 0.13) than the reported value of Ga-doped Si0.81Ge0.19 (0.05) and P-doped (5×1019 cm-3) Si0.8Ge0.2 bulk crystals at room temperature. The improvement in ZT value was caused by a decrease of thermal conductivity which related to a composition of the alloy and doping concentration in the crystal.

  8. Throughfall deposition and canopy exchange processes along a vertical gradient within the canopy of beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst).

    PubMed

    Adriaenssens, Sandy; Hansen, Karin; Staelens, Jeroen; Wuyts, Karen; De Schrijver, An; Baeten, Lander; Boeckx, Pascal; Samson, Roeland; Verheyen, Kris

    2012-03-15

    To assess the impact of air pollution on forest ecosystems, the canopy is usually considered as a constant single layer in interaction with the atmosphere and incident rain, which could influence the measurement accuracy. In this study the variation of througfall deposition and derived dry deposition and canopy exchange were studied along a vertical gradient in the canopy of one European beech (Fagus sylvatica L.) tree and two Norway spruce (Picea abies (L.) Karst) trees. Throughfall and net throughfall deposition of all ions other than H(+) increased significantly with canopy depth in the middle and lower canopy of the beech tree and in the whole canopy of the spruce trees. Moreover, throughfall and net throughfall of all ions in the spruce canopy decreased with increasing distance to the trunk. Dry deposition occurred mainly in the upper canopy and was highest during the growing season for H(+), NH(4)(+), NO(3)(-) and highest during the dormant season for Na(+), Cl(-), SO(4)(2-) (beech and spruce) and K(+), Ca(2+) and Mg(2+) (spruce only). Canopy leaching of K(+), Ca(2+) and Mg(2+) was observed at all canopy levels and was higher for the beech tree compared to the spruce trees. Canopy uptake of inorganic nitrogen and H(+) occurred mainly in the upper canopy, although significant canopy uptake was found in the middle canopy as well. Canopy exchange was always higher during the growing season compared to the dormant season. This spatial and temporal variation indicates that biogeochemical deposition models would benefit from a multilayer approach for shade-tolerant tree species such as beech and spruce. PMID:22325986

  9. Freezing and Food Safety

    MedlinePlus

    ... Forms FSIS United States Department of Agriculture Food Safety and Inspection Service About FSIS District Offices Careers ... JSR 286) Actions ${title} Loading... Freezing and Food Safety What Can You Freeze? Is Frozen Food Safe? ...

  10. Radiobrightness of diurnally heated, freezing soil

    NASA Technical Reports Server (NTRS)

    England, Anthony W.

    1990-01-01

    Freezing and thawing soils exhibit unique radiometric characteristics. To examine these characteristics, diurnal insolation is modeled as one-dimensional heating of a moist soil half-space during a typical fall at a northern Great Plains site. The one-dimensional heat flow equation is nonlinear because both the enthalpy (the change in internal energy with temperature at constant pressure) and the thermal conductivity of freezing soils are nonlinear functions of temperature. The problem is particularly difficult because phase boundaries propagate in time, and because soils, particularly clay-rich soils, freeze over a range of temperatures rather than at 0 C. Diurnal radiobrightness curves at 10.7, 18.0, and 37.0-GHz were computed for each month. The 37.0-GHz radiobrightness best tracks soil surface temperature; the 10.7-37.0-GHz spectral gradient of thawed soils is strongly positive; the spectral gradient of frozen soils is slightly negative; and the midnight-to-noon spectral gradient is shifted by approximately +0.1 K/GHz by diurnal changes in the surface temperature and the thermal gradient. These observations support the use of the scanning multichannel microwave radiometer 37.0-GHz radiobrightness and its 10.7-37.0-GHz spectral gradient as discriminants in a frozen soil classifier for high-latitude prairie.

  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. Periodic ice banding in freezing colloidal dispersions.

    PubMed

    Anderson, Anthony M; Worster, M Grae

    2012-12-01

    Concentrated colloidal alumina dispersions were frozen in a directional solidification apparatus that provides independent control of the freezing rate and temperature gradient. Two distinct steady-state modes of periodic ice banding were observed in the range of freezing rates examined. For each mode, the wavelength between successive bands of segregated ice decreases with increasing freezing rate. At low freezing rates (0.25-3 ?m s(-1)), the ice segregates from the suspension into ice lenses, which are cracklike in appearance, and there is visible structure in the layer of rejected particles in the unfrozen region ahead of the ice lenses. In this regime, we argue that compressive cryosuction forces lead to the irreversible aggregation of the rejected particles into a close-packed cohesive layer. The temperature in the aggregated layer is depressed below the bulk freezing point by more than 2 C before the ice lenses are encountered; moreover, this undercooled region appears as a light-colored layer. The magnitude of the undercooling and the color change in this region both suggest the presence of pore ice and the formation of a frozen fringe. The possibility of a frozen fringe is supported by a quantitative model of the freezing behavior. At intermediate freezing rates, around 4 ?m s(-1), the pattern of ice segregation is disordered, coinciding with the disappearance of the dark- and light-colored layers. Finally, at high freezing rates (5-10 ?m s(-1)), there is a new mode of periodic ice banding that is no longer cracklike and is absent of any visible structure in the suspension ahead of the ice bands. We discuss the implications of our experimental findings for theories of ice lensing. PMID:23110707

  13. The Freezing Bomb

    ERIC Educational Resources Information Center

    Mills, Allan

    2010-01-01

    The extreme pressures that are generated when water freezes were traditionally demonstrated by sealing a small volume in a massive cast iron "bomb" and then surrounding it with a freezing mixture of ice and salt. This vessel would dramatically fail by brittle fracture, but no quantitative measurement of bursting pressure was available. Calculation…

  14. 3 CFR - Pay Freeze

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 3 The President 1 2010-01-01 2010-01-01 false Pay Freeze Presidential Documents Other Presidential Documents Memorandum of January 21, 2009 Pay Freeze Memorandum for the Assistant to the President and Chief... many more feel uncertain about the future. In these circumstances, Government must act forcefully...

  15. 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

  16. Repeated vitrification/warming of human sperm gives better results than repeated slow programmable freezing

    PubMed Central

    Vutyavanich, Teraporn; Lattiwongsakorn, Worashorn; Piromlertamorn, Waraporn; Samchimchom, Sudarat

    2012-01-01

    In this study, we compared the effects of repeated freezing/thawing of human sperm by our in-house method of rapid freezing with slow programmable freezing. Sperm samples from 11 normozoospermic subjects were processed through density gradients and divided into three aliquots: non-frozen, rapid freezing and slow programmable freezing. Sperm in the rapid freezing group had better motility and viability than those in the slow freezing group (P<0.01) after the first, second and third cycles of freezing/thawing, but there was no difference in morphology. In the second experiment, rapid freezing was repeated three times in 20 subjects. The samples from each thawing cycle were evaluated for DNA fragmentation using the alkaline comet assay. DNA fragmentation began to increase considerably after the second cycle of freezing/thawing, but to a level that was not clinically important. In the third experiment, rapid freezing was done repeatedly in 10 subjects, until no motile sperm were observed after thawing. The median number of repeated freezing/thawing that yielded no motile sperm was seven (range: 5–8, mean: 6.8). In conclusion, we demonstrated that repeated freezing/thawing of processed semen using our rapid freezing method gave better results than standard slow programmable freezing. This method can help maximize the usage of precious cryopreserved sperm samples in assisted reproduction technology. PMID:23064685

  17. Increased spring freezing vulnerability for alpine shrubs under early snowmelt.

    PubMed

    Wheeler, J A; Hoch, G; Corts, A J; Sedlacek, J; Wipf, S; Rixen, C

    2014-05-01

    Alpine dwarf shrub communities are phenologically linked with snowmelt timing, so early spring exposure may increase risk of freezing damage during early development, and consequently reduce seasonal growth. We examined whether environmental factors (duration of snow cover, elevation) influenced size and the vulnerability of shrubs to spring freezing along elevational gradients and snow microhabitats by modelling the past frequency of spring freezing events. We sampled biomass and measured the size of Salix herbacea, Vaccinium myrtillus, Vaccinium uliginosum and Loiseleuria procumbens in late spring. Leaves were exposed to freezing temperatures to determine the temperature at which 50% of specimens are killed for each species and sampling site. By linking site snowmelt and temperatures to long-term climate measurements, we extrapolated the frequency of spring freezing events at each elevation, snow microhabitat and per species over 37 years. Snowmelt timing was significantly driven by microhabitat effects, but was independent of elevation. Shrub growth was neither enhanced nor reduced by earlier snowmelt, but decreased with elevation. Freezing resistance was strongly species dependent, and did not differ along the elevation or snowmelt gradient. Microclimate extrapolation suggested that potentially lethal freezing events (in May and June) occurred for three of the four species examined. Freezing events never occurred on late snow beds, and increased in frequency with earlier snowmelt and higher elevation. Extrapolated freezing events showed a slight, non-significant increase over the 37-year record. We suggest that earlier snowmelt does not enhance growth in four dominant alpine shrubs, but increases the risk of lethal spring freezing exposure for less freezing-resistant species. PMID:24435708

  18. Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

    NASA Astrophysics Data System (ADS)

    Wiaux, F.; Vanclooster, M.; Van Oost, K.

    2015-08-01

    In this study we aim to elucidate the role of physical conditions and gas transfer mechanism along soil profiles in the decomposition and storage of soil organic carbon (OC) in subsoil layers. We use a qualitative approach showing the temporal evolution and the vertical profile description of CO2 fluxes and abiotic variables. We assessed soil CO2 fluxes throughout two contrasted soil profiles (i.e. summit and footslope positions) along a hillslope in the central loess belt of Belgium. We measured the time series of soil temperature, soil moisture and CO2 concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO2 flux at different depths using Fick's diffusion law and horizon specific diffusivity coefficients. The calculated fluxes allowed assessing the contribution of different soil layers to surface CO2 fluxes. We constrained the soil gas diffusivity coefficients using direct observations of soil surface CO2 fluxes from chamber-based measurements and obtained a good prediction power of soil surface CO2 fluxes with an R2 of 92 %. We observed that the temporal evolution of soil CO2 emissions at the summit position is mainly controlled by temperature. In contrast, at the footslope, we found that long periods of CO2 accumulation in the subsoil alternates with short peaks of important CO2 release. This was related to the high water filled pore space that limits the transfer of CO2 along the soil profile at this slope position. Furthermore, the results show that approximately 90 to 95 % of the surface CO2 fluxes originate from the first 10 cm of the soil profile at the footslope. This indicates that soil OC in this depositional context can be stabilized at depth, i.e. below 10 cm. This study highlights the need to consider soil physical properties and their dynamics when assessing and modeling soil CO2 emissions. Finally, changes in the physical environment of depositional soils (e.g. longer dry periods) may affect the long-term stability of the large stock of easily decomposable OC that is currently stored in these environments.

  19. Ultrasound-Assisted Freezing

    NASA Astrophysics Data System (ADS)

    Delgado, A. E.; Sun, Da-Wen

    Freezing is a well-known preservation method widely used in the food industry. The advantages of freezing are to a certain degree counterbalanced by the risk of damage caused by the formation and size of ice crystals. Over recent years new approaches have been developed to improve and control the crystallization process, and among these approaches sonocrystallization has proved to be very useful, since it can enhance both the nucleation rate and the crystal growth rate. Although ultrasound has been successfully used for many years in the evaluation of various aspects of foods and in medical applications, the use of power ultrasound to directly improve processes and products is less popular in food manufacturing. Foodstuffs are very complex materials, and research is needed in order to define the specific sound parameters that aid the freezing process and that can later be used for the scale-up and production of commercial frozen food products.

  20. Pharmaceutical spray freeze drying.

    PubMed

    Wanning, Stefan; Süverkrüp, Richard; Lamprecht, Alf

    2015-07-01

    Pharmaceutical spray-freeze drying (SFD) includes a heterogeneous set of technologies with primary applications in apparent solubility enhancement, pulmonary drug delivery, intradermal ballistic administration and delivery of vaccines to the nasal mucosa. The methods comprise of three steps: droplet generation, freezing and sublimation drying, which can be matched to the requirements given by the dosage form and route of administration. The objectives, various methods and physicochemical and pharmacological outcomes have been reviewed with a scope including related fields of science and technology. PMID:25900097

  1. Freeze-cast alumina pore networks: Effects of freezing conditions and dispersion medium

    SciTech Connect

    Miller, S. M.; Xiao, X.; Faber, K. T.

    2015-11-01

    Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys, and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium. (C) 2015 Elsevier Ltd. All rights reserved.

  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. 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 permea...

  4. Entropy, Disorder, and Freezing

    NASA Astrophysics Data System (ADS)

    Laird, Brian B.

    1999-10-01

    It is argued that the usual view that entropy is a measure of "disorder" is problematic and that there exist systems at high density, for which packing considerations dominate, where a spatially ordered state has a higher entropy than a disordered one. A classic example is a system of hard-sphere atoms, for which freezing is known to be purely entropy driven. Such a model has relevance to the real world, since it provides a good qualitative (and nearly quantitative) description of solid-liquid coexistence in simple systems such as argon. An analogy based on the packing of suitcases is given to illustrate the main point. A simple classroom demonstration is also described in which an analog simulation of the freezing of hard particles is performed.

  5. The freezing bomb

    NASA Astrophysics Data System (ADS)

    Mills, Allan

    2010-03-01

    The extreme pressures that are generated when water freezes were traditionally demonstrated by sealing a small volume in a massive cast iron 'bomb' and then surrounding it with a freezing mixture of ice and salt. This vessel would dramatically fail by brittle fracture, but no quantitative measurement of bursting pressure was available. Calculation suggests a maximum of about 55 MPa (8000 psi) might have been achieved, with some 2.3% of the water frozen into a hollow shell around the interior of the vessel. In a sufficiently strong alloy steel container the pressure might rise to a maximum of 210 MPa (30 460 psi), this limiting figure being due to the collapse of ordinary ice (ice I) to the denser forms ice II or ice III.

  6. Satellite freeze forecast system

    NASA Technical Reports Server (NTRS)

    Martsolf, J. D. (Principal Investigator)

    1983-01-01

    Provisions for back-up operations for the satellite freeze forecast system are discussed including software and hardware maintenance and DS/1000-1V linkage; troubleshooting; and digitized radar usage. The documentation developed; dissemination of data products via television and the IFAS computer network; data base management; predictive models; the installation of and progress towards the operational status of key stations; and digital data acquisition are also considered. The d addition of dew point temperature into the P-model is outlined.

  7. Spatiotemporal measurement of freezing-induced deformation of engineered tissues

    PubMed Central

    Teo, Ka Yaw; Dutton, J. Craig; Han, Bumsoo

    2010-01-01

    In order to cryopreserve functional engineered tissues (ETs), the microstructure of the extracellular matrix (ECM) should be maintained as well as the cellular viability since the functionality is closely related to the ECM microstructure. Since the post-thaw ECM microstructure is determined by the deformation of ETs during cryopreservation, freezing-induced deformation of ETs was measured with a newly developed quantum dot (QD)-mediated cell image deformetry system using dermal equivalents as a model tissue. The dermal equivalents were constructed by seeding QD-labeled fibroblasts in type I collagen matrices. After 24 hour incubation, the ETs were directionally frozen by exposing them to a spatial temperature gradient (from 4 °C to −20 °C over a distance of 6 mm). While being frozen, the ETs were consecutively imaged, and consecutive pairs of these images were two-dimensionally cross-correlated to determine the local deformation during freezing. The results showed that freezing induced the deformation of ET, and its magnitude varied with both time and location. The maximum local dilatation was 0.006 s−1 and was always observed at the phase change interface. Due to this local expansion, the unfrozen region in front of the freezing interface experienced compression. This expansion-compression pattern was observed throughout the freezing process. In the unfrozen region, the deformation rate gradually decreased away from the freezing interface. After freezing/thawing, the ET experienced an approximately 28% decrease in thickness and 8% loss in weight. These results indicate that freezing-induced deformation caused the transport of interstitial fluid and the interstitial fluid was extruded. In summary, the results suggest that complex cell-fluid-matrix interactions occur within ETs during freezing, and these interactions determine the post-thaw ECM microstructure and eventual post-thaw tissue functionality. PMID:20459191

  8. Mechanisms of Freezing lnjuly in Cellular Leve

    NASA Astrophysics Data System (ADS)

    Fujikawa, Seizo

    The mechanisms of freezing injury in living cells were reviewed. The freezing injury takes place by at least two different factors depending upon cooling rate, those are intracellular freezing and extracellular freezing. The freezing injury caused by extracellular freezing also takes place by two different factors, those are direct and indirect effects by the formation of extracellular ice. These different stresses by freezing cause different damages on the plasma membranes in the same cell. Furthermore, freezing of different cell results in different form of membrane damage. Thus, the occurrence of freezing injury takes place by diverse mechanisms depending upon not only different freezing stresses but also difference of cell type.

  9. 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).

  10. Growth of gallium antimonide by vertical Bridgman technique with planar crystal-melt interface

    NASA Astrophysics Data System (ADS)

    Dutta, P. S.; Sangunni, K. S.; Bhat, H. L.; Kumar, Vikram

    1994-08-01

    High quality single crystals of GaSb were grown using vertical Bridgman technique with a planar melt-solid interface. Various factors affecting the interface shape during growth were investigated. In general, the shape of the freezing isotherm was found to depend on the furnace temperature profile near the melt-solid interface, the ampoule lowering rate, the ampoule geometry, the mode of heat extraction from the tip of the ampoule and the extent of lateral heat loss from the side walls of the ampoule. A critical ratio of temperature gradient of the furnace at the melting point to ampoule lowering rate was found to be necessary for planar interface shape during the growth. The sensitivity of the interface shape was found to decrease with increasing temperature gradient of the furnace and ampoule diameter. Crystals grown by employing the flat melt-solid interface exhibited superior quality than those with non-planar interfaces.

  11. Poromechanics of freezing materials

    NASA Astrophysics Data System (ADS)

    Coussy, Olivier

    2005-08-01

    When subjected to a uniform cooling below the freezing point a water-infiltrated porous material undergoes a cryo-deformation resulting from various combined actions: (i) the difference of density between the liquid water and the ice crystal, which results in the initial build-up of an in-pore pressure at the onset of crystallization; (ii) the interfacial effects arising between the different constituents, which eventually govern the crystallization process in connection with the pore access radius distribution; (iii) the drainage of the liquid water expelled from the freezing sites towards the air voids; (iv) the cryo-suction process, which drives liquid water towards the already frozen pores as the temperature further decreases; (v) the thermomechanical coupling between the solid matrix, the liquid water and the ice crystal. We work out a comprehensive theory able to encompass this whole set of actions. A macroscopic approach first provides the constitutive equations of freezing poroelastic materials, including the interfacial energy effects. This approach reveals the existence of a thermodynamic state function—namely the liquid saturation degree as a function of the temperature only. The macroscopic ice-dependent poroelastic properties are then upscaled from the knowledge of the elastic properties of the solid matrix, of the pore access radius distribution, and of the capillary curve. The theory is finally illustrated by analysing quantitatively the effects of the cooling rate and of the pore radius distribution upon the cryo-deformation of water-infiltrated porous materials. The theory succeeds in accounting for the experimentally observed shrinkage of embedded air voids, while predicting the partial melting of the ice already formed when the cooling suddenly stops.

  12. Freeze-Tolerant Condensers

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.; Elkouhk, Nabil

    2004-01-01

    Two condensers designed for use in dissipating heat carried by working fluids feature two-phase, self-adjusting configurations such that their working lengths automatically vary to suit their input power levels and/or heat-sink temperatures. A key advantage of these condensers is that they can function even if the temperatures of their heat sinks fall below the freezing temperatures of their working fluids and the fluids freeze. The condensers can even be restarted from the frozen condition. The top part of the figure depicts the layout of the first condenser. A two-phase (liquid and vapor) condenser/vapor tube is thermally connected to a heat sink typically, a radiatively or convectively cooled metal panel. A single-phase (liquid) condensate-return tube (return artery) is also thermally connected to the heat sink. At intervals along their lengths, the condenser/vapor tube and the return artery are interconnected through porous plugs. This condenser configuration affords tolerance of freezing, variable effective thermal conductance (such that the return temperature remains nearly constant, independently of the ultimate sink temperature), and overall pressure drop smaller than it would be without the porous interconnections. An additional benefit of this configuration is that the condenser can be made to recover from the completely frozen condition either without using heaters, or else with the help of heaters much smaller than would otherwise be needed. The second condenser affords the same advantages and is based on a similar principle, but it has a different configuration that affords improved flow of working fluid, simplified construction, reduced weight, and faster recovery from a frozen condition.

  13. Biomaterials by freeze casting.

    PubMed

    Wegst, Ulrike G K; Schecter, Matthew; Donius, Amalie E; Hunger, Philipp M

    2010-04-28

    The functional requirements for synthetic tissue substitutes appear deceptively simple: they should provide a porous matrix with interconnecting porosity and surface properties that promote rapid tissue ingrowth; at the same time, they should possess sufficient stiffness, strength and toughness to prevent crushing under physiological loads until full integration and healing are reached. Despite extensive efforts and first encouraging results, current biomaterials for tissue regeneration tend to suffer common limitations: insufficient tissue-material interaction and an inherent lack of strength and toughness associated with porosity. The challenge persists to synthesize materials that mimic both structure and mechanical performance of the natural tissue and permit strong tissue-implant interfaces to be formed. In the case of bone substitute materials, for example, the goal is to engineer high-performance composites with effective properties that, similar to natural mineralized tissue, exceed by orders of magnitude the properties of its constituents. It is still difficult with current technology to emulate in synthetic biomaterials multi-level hierarchical composite structures that are thought to be the origin of the observed mechanical property amplification in biological materials. Freeze casting permits to manufacture such complex, hybrid materials through excellent control of structural and mechanical properties. As a processing technique for the manufacture of biomaterials, freeze casting therefore has great promise. PMID:20308117

  14. 9 CFR 590.534 - Freezing facilities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Freezing facilities. 590.534 Section..., and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off the premises, shall be capable of freezing all liquid egg products in accordance with the freezing...

  15. 9 CFR 590.534 - Freezing facilities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 2 2013-01-01 2013-01-01 false Freezing facilities. 590.534 Section..., and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off the premises, shall be capable of freezing all liquid egg products in accordance with the freezing...

  16. 9 CFR 590.534 - Freezing facilities.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 2 2014-01-01 2014-01-01 false Freezing facilities. 590.534 Section..., and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off the premises, shall be capable of freezing all liquid egg products in accordance with the freezing...

  17. Performance Characteristics of an Isothermal Freeze Valve

    SciTech Connect

    Hailey, A.E.

    2001-08-22

    This document discusses performance characteristics of an isothermal freeze valve. A freeze valve has been specified for draining the DWPF melter at the end of its lifetime. Two freeze valve designs have been evaluated on the Small Cylindrical Melter-2 (SCM-2). In order to size the DWPF freeze valve, the basic principles governing freeze valve behavior need to be identified and understood.

  18. Variation and co-variation of PM10, particle number concentration, NOx and NO2 in the urban air - Relationships with wind speed, vertical temperature gradient and weather type

    NASA Astrophysics Data System (ADS)

    Grundström, M.; Hak, C.; Chen, D.; Hallquist, M.; Pleijel, H.

    2015-11-01

    Atmospheric ultrafine particles (UFP; diameter < 0.1 μm) represent a growing global health concern in urban environments and has a strong link to traffic related emissions. UFP is usually the dominating fraction of atmospheric particle number concentrations (PNC) despite being a minor part of total particle mass. The aim of this study was to empirically investigate the relationship between PNC and other air pollutants (NOX, NO2 and PM10) in the urban environment and their dependence on meteorology and weather type, using the Lamb Weather Type (LWT) classification scheme. The study was carried out in Gothenburg, Sweden, at an urban background site during April 2007-May 2008. It was found that daily average [PNC] correlated very well with [NOx] (R2 = 0.73) during inversion days, to a lesser extent with [NO2] (R2 = 0.58) and poorly with [PM10] (R2 = 0.07). Both PNC and NOx had similar response patterns to wind speed and to the strength of temperature inversions. PNC displayed two regimes, one strongly correlated to NOx and a second poorly correlated to NOx which was characterised by high wind speed. For concentration averages based on LWTs, the PNC-[NOx] relationship remained strong (R2 = 0.70) where the windy LWT W deviated noticeably. Exclusion of observations with wind speed >5 ms-1 or ΔT < 0 °C from LWTs produced more uniform and stronger relationships (R2 = 0.90; R2 = 0.93). Low wind speeds and positive vertical temperature gradients were most common during LWTs A, NW, N and NE. These weather types were also associated with the highest daily means of NOx (˜30 ppb) and PNC (˜10 000 # cm-3). A conclusion from this study is that NOx (but not PM10) is a good proxy for PNC especially during calm and stable conditions and that LWTs A, NW, N and NE are high risk weather types for elevated NOx and PNC.

  19. Freezing of living cells

    SciTech Connect

    Mazur, P.

    1985-01-01

    It can be calculated that a living cell will survive more than 5000 years at -196/sup 0/C. This ability to essentially stop biological time has important implications in medicine and agriculture, and in biological research. In medicine the chief implications are in the banking of transplantable tissues and organs and in in vitro fertilization. In agriculture the applications stem in part from the role of frozen embryos in amplifying the number of calves produced by high quanlity cows. The problem is how can cells survive both the cooling to such very low temperatures and the return to normal temperatures. The answers involve fundamental characteristics of cells such as the permeability of their surface membranes to water and solutes. These characteristics determine whether or not cells undergo lethal internal ice formation and other response during freezing and thawing. 27 refs., 12 figs.

  20. Understanding Slag Freeze Linings

    NASA Astrophysics Data System (ADS)

    Fallah-Mehrjardi, Ata; Hayes, Peter C.; Jak, Evgueni

    2014-09-01

    Slag freeze linings, the formation of protective deposit layers on the inner walls of furnaces and reactors, are increasingly used in industrial pyrometallurgical processes to ensure that furnace integrity is maintained in these aggressive, high-temperature environments. Most previous studies of freeze-linings have analyzed the formation of slag deposits based solely on heat transfer considerations. These thermal models have assumed that the interface between the stationary frozen layer and the agitated molten bath at steady-state deposit thickness consists of the primary phase, which stays in contact with the bulk liquid at the liquidus temperature. Recent experimental studies, however, have clearly demonstrated that the temperature of the deposit/liquid bath interface can be lower than the liquidus temperature of the bulk liquid. A conceptual framework has been proposed to explain the observations and the factors influencing the microstructure and the temperature of the interface at steady-state conditions. The observations are consistent with a dynamic steady state that is a balance between (I) the rate of nucleation and growth of solids on detached crystals in a subliquidus layer as this fluid material moves toward the stagnant deposit interface and (II) the dissolution of these detached crystals as they are transported away from the interface by turbulent eddies. It is argued that the assumption that the interface temperature is the liquidus of the bulk material represents only a limiting condition, and that the interface temperature can be between T liquidus and T solidus depending on the process conditions and bath chemistry. These findings have implications for the modeling approach and boundary conditions required to accurately describe these systems. They also indicate the opportunity to integrate considerations of heat and mass flows with the selection of melt chemistries in the design of future high temperature industrial reactors.

  1. Coil freezing: What a relief!

    SciTech Connect

    Jacobs, T.L.

    1995-12-01

    This article describes why a coil freezes, what happens during the freezing, and what is required to alleviate the damage. Water and steam have been used to cool and heat air in finned-tube heat exchanger coils almost since the inception of heating and air conditioning. Freezing of the fluid and the resultant coil damage have also been around for the same length of time. It is a systematic problem that many times is preventable, but one knows that this is not a perfect world. Nor are the HVAC and process systems that have been in service for decades. It is fairly simple to understand the basics of a liquid phase freeze. The ambient conditions must be at or below 32 F, and that can, in turn cause the water inside the coil to fall below 32 F as well. If kept below the freezing temperature of fluid long enough, the coil may be damaged by this condition.

  2. Wastewater treatment by radial freezing with stirring effects.

    PubMed

    Gay, Guillaume; Lorain, Olivier; Azouni, Aza; Aurelle, Yves

    2003-05-01

    Radial freezing experiments on wastewater models were conducted in the presence of imposed stirring in order to remove impurities. The studied samples (dilute Na-montmorillonite suspensions charged with nitrates and with zinc or lead) were placed inside a cylindrical annulus, cooled at a controlled temperature around -7 degrees C at its inner wall which rotated around a vertical axis. The freezing front propagated toward the still outer wall which was maintained at a constant temperature around +1 degrees C. Thanks to stirring, considerable purification rates up to 99.97% were attained. It was also demonstrated that combining radial freezing and stirring ended in residual concentrations which agreed with drinking water standards. PMID:12727265

  3. Biomimetic Materials by Freeze Casting

    NASA Astrophysics Data System (ADS)

    Porter, Michael M.; Mckittrick, Joanna; Meyers, Marc A.

    2013-06-01

    Natural materials, such as bone and abalone nacre, exhibit exceptional mechanical properties, a product of their intricate microstructural organization. Freeze casting is a relatively simple, inexpensive, and adaptable materials processing method to form porous ceramic scaffolds with controllable microstructural features. After infiltration of a second polymeric phase, hybrid ceramic-polymer composites can be fabricated that closely resemble the architecture and mechanical performance of natural bone and nacre. Inspired by the narwhal tusk, magnetic fields applied during freeze casting can be used to further control architectural alignment, resulting in freeze-cast materials with enhanced mechanical properties.

  4. Peripheral Blood Mononuclear Cells: Isolation, Freezing, Thawing, and Culture.

    PubMed

    Riedhammer, Christine; Halbritter, Dagmar; Weissert, Robert

    2016-01-01

    The work with peripheral blood mononuclear cells (PBMCs), which comprise lymphocytes and monocytes, is indispensable in immunological diagnostics and research. The isolation of PBMCs takes advantage of differences in cell density of the different blood components. Density gradient centrifugation of diluted whole blood layered over a density gradient medium yields PBMCs; two subsequent washing steps remove remaining platelets. To store the cells for future assays, they can be frozen and thawed when required. Dimethyl sulfoxide (DMSO) serves as a cryoprotectant for freezing PBMCs, but must be removed by washing after thawing, as it can become toxic to the cells on longer exposure. PMID:25092056

  5. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures shall...

  6. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures shall...

  7. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 2 2011-01-01 2011-01-01 false Freezing operations. 590.536 Section..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... products shall be examined by organoleptic examination after freezing to determine their fitness for...

  8. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures shall...

  9. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures shall...

  10. 7 CFR 58.621 - Freezing tunnels.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Freezing tunnels. 58.621 Section 58.621 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....621 Freezing tunnels. Freezing tunnels for quick freezing at extremely low temperatures shall...

  11. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 2 2013-01-01 2013-01-01 false Freezing operations. 590.536 Section..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... products shall be examined by organoleptic examination after freezing to determine their fitness for...

  12. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Freezing operations. 590.536 Section..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... products shall be examined by organoleptic examination after freezing to determine their fitness for...

  13. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Freezing operations. 590.536 Section..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... products shall be examined by organoleptic examination after freezing to determine their fitness for...

  14. 9 CFR 590.536 - Freezing operations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 2 2014-01-01 2014-01-01 false Freezing operations. 590.536 Section..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... products shall be examined by organoleptic examination after freezing to determine their fitness for...

  15. Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model

    NASA Technical Reports Server (NTRS)

    Friedman, R.; Stockemer, F. J.

    1980-01-01

    Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank, to simulate internal temperature gradients encountered in commercial airplane wing tanks. Two low-temperature situations were observed. Where the bulk of the fuel is above the specification freezing point, pumpout of the fuel removes all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depends on the fuel temperature near these surfaces. Where the bulk of the fuel is at or below the freezing point, pumpout ceases when solids block the pump inlet, and the unpumpable fraction depends on the overall average temperature.

  16. Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model

    NASA Technical Reports Server (NTRS)

    Friedman, R.; Stockemer, F. J.

    1980-01-01

    Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank chilled to simulate internal temperature gradients encountered in commercial airplane wing tanks. When the bulk of the fuel was above the specification freezing point, pumpout of the fuel removed all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depended on the fuel temperature near these surfaces. When the bulk of the fuel was at or below the freezing point, pumpout ceased when solids blocked the pump inlet, and the unpumpable fraction depended on the overall average temperature.

  17. Facing freeze: social threat induces bodily freeze in humans.

    PubMed

    Roelofs, Karin; Hagenaars, Muriel A; Stins, John

    2010-11-01

    Freezing is a common defensive response in animals threatened by predators. It is characterized by reduced body motion and decreased heart rate (bradycardia). However, despite the relevance of animal defense models in human stress research, studies have not shown whether social threat cues elicit similar freeze-like responses in humans. We investigated body sway and heart rate in 50 female participants while they were standing on a stabilometric force platform and viewing cues that were socially threatening, socially neutral, and socially affiliative (angry, neutral, and happy faces, respectively). Posturographic analyses showed that angry faces (compared with neutral faces and happy faces) induced significant reductions in body sway. In addition, the reduced body sway for angry faces was accompanied by bradycardia and correlated significantly with subjective anxiety. Together, these findings indicate that spontaneous body responses to social threat cues involve freeze-like behavior in humans that mimics animal freeze responses. These findings open avenues for studying human freeze responses in relation to various sociobiological markers and social-affective disorders. PMID:20876881

  18. Fundamentals of freeze-drying.

    PubMed

    Nail, Steven L; Jiang, Shan; Chongprasert, Suchart; Knopp, Shawn A

    2002-01-01

    Given the increasing importance of reducing development time for new pharmaceutical products, formulation and process development scientists must continually look for ways to "work smarter, not harder." Within the product development arena, this means reducing the amount of trial and error empiricism in arriving at a formulation and identification of processing conditions which will result in a quality final dosage form. Characterization of the freezing behavior of the intended formulation is necessary for developing processing conditions which will result in the shortest drying time while maintaining all critical quality attributes of the freeze-dried product. Analysis of frozen systems was discussed in detail, particularly with respect to the glass transition as the physical event underlying collapse during freeze-drying, eutectic mixture formation, and crystallization events upon warming of frozen systems. Experiments to determine how freezing and freeze-drying behavior is affected by changes in the composition of the formulation are often useful in establishing the "robustness" of a formulation. It is not uncommon for seemingly subtle changes in composition of the formulation, such as a change in formulation pH, buffer salt, drug concentration, or an additional excipient, to result in striking differences in freezing and freeze-drying behavior. With regard to selecting a formulation, it is wise to keep the formulation as simple as possible. If a buffer is needed, a minimum concentration should be used. The same principle applies to added salts: If used at all, the concentration should be kept to a minimum. For many proteins a combination of an amorphous excipient, such as a disaccharide, and a crystallizing excipient, such as glycine, will result in a suitable combination of chemical stability and physical stability of the freeze-dried solid. Concepts of heat and mass transfer are valuable in rational design of processing conditions. Heat transfer by conduction--the dominant mechanism of heat transfer in freeze-drying--is inefficient at the pressures used in freeze-drying. Steps should be taken to improve the thermal contact between the product and the shelf of the freeze dryer, such as eliminating metal trays from the drying process. Quantitation of the heat transfer coefficient for the geometry used is a useful way of assessing the impact of changes in the system such as elimination of product trays and changes in the vial. Because heat transfer by conduction through the vapor increases with increasing pressure, the commonly held point of view that "the lower the pressure, the better" is not true with respect to process efficiency. The optimum pressure for a given product is a function of the temperature at which freeze-drying is carried out, and lower pressures are needed at low product temperatures. The controlling resistance to mass transfer is almost always the resistance of the partially dried solids above the submination interface. This resistance can be minimized by avoiding fill volumes of more than about half the volume of the container. The development scientist should also recognize that very high concentrations of solute may not be appropriate for optimum freeze-drying, particularly if the resistance of the dried product layer increases sharply with concentration. Although the last 10 years has seen the publication of a significant body of literature of great value in allowing development scientists and engineers to "work smarter," there is still much work needed in both the science and the technology of freeze-drying. Scientific development is needed for improving analytical methodology for characterization of frozen systems and freeze-dried solids. A better understanding of the relationship between molecular mobility and reactivity is needed to allow accurate prediction of product stability at the intended storage temperature based on accelerated stability at higher temperatures. This requires that the temperature dependence of glass transition-associated mobility, particularly at temperatures below the glass transition, be studied in greater depth. The relevance of the concept of strong and fragile glasses to frozen systems and freeze-dried solids has only begun to be explored. The list of pharmaceutically acceptable protective solutes is very short, and more imagination--and work--is needed in order to develop pharmaceutically acceptable alternative stabilizers. There is a need for technology development in process monitoring, particularly in developing a way to measure the status of the product during freezing and freeze-drying without placing temperature measurement probes in individual vials of product. The current practice of placing thermocouples in vials is uncertain with respect to reliability of the data, inconsistent with elimination of personnel in close proximity to open vials of product in an aseptic environment, and incompatible with technology for automatic material handling in freeze-drying. In addition, a method for controlling the degree of supercooling during freezing would allow better control of freezing rate and would, in many cases, result in more consistent product quality. PMID:12189727

  19. THE VERTICAL

    NASA Technical Reports Server (NTRS)

    Albert, Stephen L.; Spencer, Jeffrey B.

    1994-01-01

    'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.

  20. Heat freezes niche evolution.

    PubMed

    Arajo, Miguel B; Ferri-Yez, 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

  1. Basic concepts in freezing cells

    SciTech Connect

    Mazur, P.

    1985-01-01

    Freezing involves the lowering of temperature and the formation of ice. Most cells have not been found to be sensitive to the former; rather injury is a consequence of the removal of water from the system in the form of ice. Some cells such as boar sperm and those of many tropical crops are susceptible to even short-term lowering of temperature to near O/sup 0/C. This susceptiblity, which is independent of the rate of temperature drop, is defined as chilling injury. Other cells are injured by chilling only if the rate of cooling is high, a phenomenon referred to as thermal shock. This paper discusses the physical-chemical events during freezing and on freezing injury will assume that lowered temperature per se is not injurious.

  2. Freeze-in through portals

    SciTech Connect

    Blennow, Mattias; Fernandez-Martínez, Enrique; Zaldívar, Bryan E-mail: enrique.fernandez-martinez@uam.es

    2014-01-01

    The popular freeze-out paradigm for Dark Matter (DM) production, relies on DM-baryon couplings of the order of the weak interactions. However, different search strategies for DM have failed to provide a conclusive evidence of such (non-gravitational) interactions, while greatly reducing the parameter space of many representative models. This motivates the study of alternative mechanisms for DM genesis. In the freeze-in framework, the DM is slowly populated from the thermal bath while never reaching equilibrium. In this work, we analyse in detail the possibility of producing a frozen-in DM via a mediator particle which acts as a portal. We give analytical estimates of different freeze-in regimes and support them with full numerical analyses, taking into account the proper distribution functions of bath particles. Finally, we constrain the parameter space of generic models by requiring agreement with DM relic abundance observations.

  3. Freezing of a liquid marble.

    PubMed

    Hashmi, Ali; Strauss, Adam; Xu, Jie

    2012-07-17

    In this study, we present for the first time the observations of a freezing liquid marble. In the experiment, liquid marbles are gently placed on the cold side of a thermo-electric cooler (TEC), and the morphological changes are recorded and characterized thereafter. These liquid marbles are noticed to undergo a shape transition from a spherical to a flying-saucer-shaped morphology. The freezing dynamics of liquid marbles is observed to be very different from that of a freezing water droplet on a superhydrophobic surface. For example, the pointy tip appearing on a frozen water drop could not be observed for a frozen liquid marble. In the end, we highlight a possible explanation of the observed morphology. PMID:22746403

  4. Water freezing and ice melting

    DOE PAGESBeta

    Malolepsza, Edyta; Keyes, Tom

    2015-10-12

    The generalized replica exchange method (gREM) is designed to sample states with coexisting phases and thereby to describe strong first order phase transitions. The isobaric MD version of the gREM is presented and applied to freezing of liquid water, and melting of hexagonal and cubic ice. It is confirmed that coexisting states are well sampled. The statistical temperature as a function of enthalpy, TS(H), is obtained. Hysteresis between freezing and melting is observed and discussed. The entropic analysis of phase transitions is applied and equilibrium transition temperatures, latent heats, and surface tensions are obtained for hexagonal ice↔liquid and cubic ice↔liquid,more » with excellent agreement with published values. A new method is given to assign water molecules among various symmetry types. As a result, pathways for water freezing, ultimately leading to hexagonal ice, are found to contain intermediate layered structures built from hexagonal and cubic ice.« less

  5. Water freezing and ice melting

    SciTech Connect

    Malolepsza, Edyta; Keyes, Tom

    2015-10-12

    The generalized replica exchange method (gREM) is designed to sample states with coexisting phases and thereby to describe strong first order phase transitions. The isobaric MD version of the gREM is presented and applied to freezing of liquid water, and melting of hexagonal and cubic ice. It is confirmed that coexisting states are well sampled. The statistical temperature as a function of enthalpy, TS(H), is obtained. Hysteresis between freezing and melting is observed and discussed. The entropic analysis of phase transitions is applied and equilibrium transition temperatures, latent heats, and surface tensions are obtained for hexagonal ice↔liquid and cubic ice↔liquid, with excellent agreement with published values. A new method is given to assign water molecules among various symmetry types. As a result, pathways for water freezing, ultimately leading to hexagonal ice, are found to contain intermediate layered structures built from hexagonal and cubic ice.

  6. Water Freezing and Ice Melting.

    PubMed

    Małolepsza, Edyta; Keyes, Tom

    2015-12-01

    The generalized replica exchange method (gREM) is designed to sample states with coexisting phases and thereby to describe strong first order phase transitions. The isobaric MD version of the gREM is presented and applied to the freezing of liquid water and the melting of hexagonal and cubic ice. It is confirmed that coexisting states are well-sampled. The statistical temperature as a function of enthalpy, TS(H), is obtained. Hysteresis between freezing and melting is observed and discussed. The entropic analysis of phase transitions is applied and equilibrium transition temperatures, latent heats, and surface tensions are obtained for hexagonal ice ↔ liquid and cubic ice ↔ liquid with excellent agreement with published values. A new method is given to assign water molecules among various symmetry types. Pathways for water freezing, ultimately leading to hexagonal ice, are found to contain intermediate layered structures built from hexagonal and cubic ice. PMID:26642983

  7. Freeze-dried microarterial allografts

    SciTech Connect

    Raman, J.; Hargrave, J.C.

    1990-02-01

    Rehydrated freeze-dried microarterial allografts were implanted to bridge arterial defects using New Zealand White rabbits as the experimental model. Segments of artery from the rabbit ear and thigh were harvested and preserved for a minimum of 2 weeks after freeze-drying. These allografts, approximately 1 mm in diameter and ranging from 1.5 to 2.5 cm in length, were rehydrated and then implanted in low-pressure and high-pressure arterial systems. Poor patency was noted in low-pressure systems in both allografts and autografts, tested in 12 rabbits. In the high-pressure arterial systems, allografts that were freeze-dried and reconstituted failed in a group of 10 rabbits with an 8-week patency rate of 30 percent. Gamma irradiation in an effort to reduce infection and antigenicity of grafts after freeze-drying was associated with a patency rate of 10 percent at 8 weeks in this system in another group of 10 rabbits. Postoperative cyclosporin A therapy was associated with a patency rate of 22.2 percent in the high-pressure arterial system in a 9-rabbit group. Control autografts in this system in a group of 10 rabbits showed a 100 percent patency at 8 weeks. Microarterial grafts depend on perfusion pressure of the vascular bed for long-term patency. Rehydrated freeze-dried microarterial allografts do not seem to function well in lengths of 1 to 2.5 cm when implanted in a high-pressure arterial system. Freeze-dried arterial allografts are probably not antigenic.

  8. Irradiance gradients

    SciTech Connect

    Ward, G.J. Ecole Polytechnique Federale, Lausanne ); Heckbert, P.S. . School of Computer Science Technische Hogeschool Delft . Dept. of Technical Mathematics and Informatics)

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques.

  9. Tunable shape transformation of freezing liquid water marbles.

    PubMed

    Zang, Duyang; Lin, Kejun; Wang, Wenkai; Gu, Yaxi; Zhang, Yongjian; Geng, Xingguo; Binks, Bernard P

    2014-03-01

    Liquid water marbles coated with fumed silica nanoparticles exhibit various shape transformations upon freezing which are dependent on the hydrophobicity of the nanoparticles. The shape can be recovered during re-melting. For marbles coated with the most hydrophobic particles, a vertically prolonged morphology with a pointed protrusion on the top is formed on freezing. For marbles coated with less hydrophobic particles, a lateral expanded flying saucer-shaped morphology is formed. The different responses to freezing result from the different heterogeneous nucleation sites owing to the different positions of the particles at the air-water interface. If the particles are more immersed in water, ice embryos tend to form in the concave cavities between the particles. The volume expansion of water caused by freezing and continuous nucleation lead to continuous lateral stretching of the particle network coating the droplet surface and ultimately to the horizontally inflated shape of the marble. If the particles are more exposed to air, nucleation occurs on the convex surface of the particles, similar to that of a bare water droplet on a hydrophobic substrate. PMID:24651262

  10. Non-freezing cold injury.

    PubMed

    Glennie, J S; Milner, R

    2014-01-01

    Non-freezing cold injury can be a diagnostic challenge for clinicians in the United Kingdom Armed Forces. It is associated with operations in adverse climatic conditions, and may result in significant long-term morbidity. In this article we discuss the operational importance of this condition and the current best practice in its management and prevention. PMID:25895405

  11. 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.

  12. 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

  13. 9 CFR 590.534 - Freezing facilities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... PRODUCTS INSPECTION INSPECTION OF EGGS AND EGG PRODUCTS (EGG PRODUCTS INSPECTION ACT) Sanitary, Processing, and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off...

  14. 9 CFR 590.534 - Freezing facilities.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... PRODUCTS INSPECTION INSPECTION OF EGGS AND EGG PRODUCTS (EGG PRODUCTS INSPECTION ACT) Sanitary, Processing, and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off...

  15. 7 CFR 51.1562 - Freezing.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Freezing. 51.1562 Section 51.1562 Agriculture..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1562 Freezing. Freezing means that the potato is frozen or shows evidence of having been frozen....

  16. 7 CFR 51.1562 - Freezing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Freezing. 51.1562 Section 51.1562 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Potatoes 1 Definitions § 51.1562 Freezing. Freezing means that the potato is...

  17. 7 CFR 51.1562 - Freezing.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Freezing. 51.1562 Section 51.1562 Agriculture..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1562 Freezing. Freezing means that the potato is frozen or shows evidence of having been frozen....

  18. 7 CFR 51.1562 - Freezing.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Freezing. 51.1562 Section 51.1562 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Potatoes 1 Definitions § 51.1562 Freezing. Freezing means that the potato is...

  19. 7 CFR 51.1562 - Freezing.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Freezing. 51.1562 Section 51.1562 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Potatoes 1 Definitions § 51.1562 Freezing. Freezing means that the potato is...

  20. Measuring freezing tolerance: Survival and regrowth assays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Screening plants for freezing tolerance under tightly-controlled conditions is an invaluable technique for studying freezing tolerance and selecting for improved winterhardiness. Artificial freezing tests of cereal plants historically have used isolated crown and stem tissue prepared by “removing a...

  1. 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...

  2. 23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false LCV freeze; cargo-carrying unit freeze. 658.23 Section 658.23 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS-LENGTH, WIDTH AND WEIGHT LIMITATIONS § 658.23 LCV freeze; cargo-carrying unit freeze....

  3. Non Linear Conjugate Gradient

    Energy Science and Technology Software Center (ESTSC)

    2006-11-17

    Software that simulates and inverts electromagnetic field data for subsurface electrical properties (electrical conductivity) of geological media. The software treats data produced by a time harmonic source field excitation arising from the following antenna geometery: loops and grounded bipoles, as well as point electric and magnetic dioples. The inversion process is carried out using a non-linear conjugate gradient optimization scheme, which minimizes the misfit between field data and model data using a least squares criteria.more » The software is an upgrade from the code NLCGCS_MP ver 1.0. The upgrade includes the following components: Incorporation of new 1 D field sourcing routines to more accurately simulate the 3D electromagnetic field for arbitrary geologic& media, treatment for generalized finite length transmitting antenna geometry (antennas with vertical and horizontal component directions). In addition, the software has been upgraded to treat transverse anisotropy in electrical conductivity.« less

  4. Freeze chromatography method and apparatus

    DOEpatents

    Scott, C.D.

    1987-04-16

    A freeze chromatography method and apparatus are provided which enable separation of the solutes contained in a sample. The apparatus includes an annular column construction comprising cylindrical inner and outer surfaces defining an annular passage therebetween. One of the surfaces is heated and the other cooled while passing an eluent through the annular passageway so that the eluent in contact with the cooled surface freezes and forms a frozen eluent layer thereon. A mixture of solutes dissolved in eluent is passed through the annular passageway in contact with the frozen layer so that the sample solutes in the mixture will tend to migrate either toward or away the frozen layer. The rate at which the mixture flows through the annular passageway is controlled so that the distribution of the sample solutes approaches that at equilibrium and thus a separation between the sample solutes occurs. 3 figs.

  5. 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.

  6. Updating freeze: aligning animal and human research.

    PubMed

    Hagenaars, Muriel A; Oitzl, Melly; Roelofs, Karin

    2014-11-01

    Freezing is widely used as the main outcome measure for fear in animal studies. Freezing is also getting attention more frequently in human stress research, as it is considered to play an important role in the development of psychopathology. Human models on defense behavior are largely based on animal models. Unfortunately, direct translations between animal and human studies are hampered by differences in definitions and methods. The present review therefore aims to clarify the conceptualization of freezing. Neurophysiological and neuroanatomical correlates are discussed and a translational model is proposed. We review the upcoming research on freezing in humans that aims to match animal studies by using physiological indicators of freezing (bradycardia and objective reduction in movement). Finally, we set the agenda for future research in order to optimize mutual animal-human translations and stimulate consistency and systematization in future empirical research on the freezing phenomenon. PMID:25108035

  7. Predicting Freezing for Some Repulsive Potentials

    SciTech Connect

    Khrapak, S. A.; Morfill, G. E.

    2009-12-18

    We propose a simple method to approximately predict the freezing (fluid-solid) phase transition in systems of particles interacting via purely repulsive potentials. The method is based on the striking universality of the freezing curve for the model Yukawa and inverse-power-law interactions. This method is applied to draw an exemplary phase diagram of complex plasmas. We suggest that it can also be used to locate freezing transition in other substances with similar properties of interaction.

  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. Relationship between heat transfer parameters and the characteristic damage variables for the freezing of beef.

    PubMed

    Mascheroni, R H; Calvelo, A

    1980-08-01

    One of the most suitable parameters for relating the freezing rate to the volume of drip produced during the thawing of meat is the characteristic time, defined as the time necessary to reduce the temperature of the sample from -1·1°C (initial freezing point in beef) to -7°C (80% of the water frozen). However, as the freezing of beef in factories takes place with important temperature gradients, distributions of these characteristic times must be expected along the pieces of frozen meat. In order to relate these characteristic time distributions to heat transfer parameters under industrial freezing conditions, a mathematical model which simulates the freezing of beef is developed in this paper. The model establishes the heat transfer equations with simultaneous change of phase, taking into account the dependence of the thermal properties with the ice content and considering the anisotropy of the thermal conductivity according to the direction of the fibres. Boundary conditions include the possibility of thermal resistances in the refrigerated interphase. The model developed was compared with laboratory experiments performed under factory freezing conditions and showed a satisfactory agreement between theory and experiment. PMID:22055769

  10. Giant panda (Ailuropoda melanoleuca) sperm morphometry and function after repeated freezing and thawing.

    PubMed

    Santiago-Moreno, J; Esteso, M C; Pradiee, J; Castaño, C; Toledano-Díaz, A; O'Brien, E; Lopez-Sebastián, A; Martínez-Nevado, E; Delclaux, M; Fernández-Morán, J; Zhihe, Z

    2016-05-01

    This work examines the effects of subsequent cycles of freezing-thawing on giant panda (Ailuropoda melanoleuca) sperm morphometry and function, and assesses whether density-gradient centrifugation (DGC) can increase the number of freezing-thawing cycles this sperm can withstand. A sperm sample was collected by electroejaculation from a mature giant panda and subjected to five freezing-thawing cycles. Although repeated freezing-thawing negatively affected (P < 0.05) sperm motility and membrane integrity, in both nonselected and DCG-selected sperm samples, >60% of the sperm cells in both treatments showed acrosome integrity even after the fifth freezing cycle. In fresh semen, the sperm head length was 4.7 μm, the head width 3.6 μm, area 14.3 μm(2) and perimeter length 14.1 μm. The present results suggest that giant panda sperm trends to be resistant to repeated freezing-thawing, even without DGC selection. PMID:26268795

  11. Egg freezing: a breakthrough for reproductive autonomy?

    PubMed

    Harwood, Karey

    2009-01-01

    This article describes the relatively new technology of freezing human eggs and examines whether egg freezing, specifically when it is used by healthy women as 'insurance' against age-related infertility, is a legitimate exercise of reproductive autonomy. Although egg freezing has the potential to expand women's reproductive options and thus may represent a breakthrough for reproductive autonomy, I argue that without adequate information about likely outcomes and risks, women may be choosing to freeze their eggs in a commercially exploitative context, thus undermining rather than expanding reproductive autonomy. PMID:18945249

  12. 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...

  13. 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.

  14. Mechanisms of deterioration of nutrients. [of freeze dried foods

    NASA Technical Reports Server (NTRS)

    Karel, M.; Flink, J. M.

    1976-01-01

    Methods which produce freeze dried foods of improved quality were examined with emphasis on storage stability. Specific topics discussed include: microstructure of freeze dried systems, investigation of structural changes in freeze dried systems, artificial food matrices, osmotic preconcentration to yield improved quality freeze dried fruits, and storage stability of osmotically preconcentrated freeze dried fruits.

  15. Urban Modification of Freezing-Rain Events.

    NASA Astrophysics Data System (ADS)

    Changnon, Stanley A.

    2003-06-01

    A new national database for freezing-rain occurrences during the 1945-2000 period provided an opportunity for a study of the potential urban effects on freezing-rain events. Numerous past studies of snowfall events in urban areas have defined decreases of 10%-35% related to the urban heat island. The heat island, which acts to elevate near-surface temperatures, could also keep some freezing-rain situations from occurring in the city. The study involved four cities in the Midwest and Northeast for which the average annual number of days with freezing rain are three or more, for which data from in-city stations existed, and for which data for several surrounding rural stations existed. The two largest qualifying cities, New York City, New York, and Chicago, Illinois, had sizable reductions in average and maximum annual freezing-rain-day frequencies, ranging from 16% to 43% less than values of surrounding rural stations, and their freezing-rain `seasons' were 1-2 months shorter than those in surrounding rural areas. The ocean/lake influences at both cities, along with the heat island, also helped to reduce the local incidence of freezing-rain events. Two qualifying smaller urban areas, Washington, District of Columbia, and St. Louis, Missouri, had reductions in freezing-rain-day occurrences but had no shifts in the length of their freezing-rain seasons. Results suggest that freezing-rain occurrences in large cities are decreased between 10% and 30% by the heat island, which acts to keep rain from freezing to urban surfaces.

  16. Identification, analysis and monitoring of risks of freezing affecting aircraft flying over the Guadarrama Mountains (Spain)

    NASA Astrophysics Data System (ADS)

    Fernández-González, Sergio; Sánchez, José Luis; Gascón, Estíbaliz; Merino, Andrés; Hermida, Lucía; López, Laura; Marcos, José Luis; García-Ortega, Eduardo

    2014-05-01

    Freezing is one of the main causes of aircraft accidents registered over the last few decades. This means it is very important to be able to predict this situation so that aircraft can change their routes to avoid freezing risk areas. Also, by using satellites it is possible to observe changes in the horizontal and vertical extension of cloud cover likely to cause freezing in real time as well as microphysical changes in the clouds. The METEOSAT Second Generation (MSG) makes it possible to create different red-green-blue (RGB) compositions that provide a large amount of information associated with the microphysics of clouds, in order to identify super-cooled water clouds that pose a high risk of freezing to aircraft. During the winter of 2011/12 in the Guadarrama Mountains, in the centre of the Iberian Peninsula, a series of scientific flights (conducted by INTA) were organised in order to study the cloud systems that affected this region during the winter. On the flight of the 1st of February 2012, the aircraft was affected by freezing after crossing over a mountain ridge with supercooled large drops (SLD). Although freezing was not expected during that day's flight, the orography caused a series of mesoscale factors that led to the appearance of localised freezing conditions. By analysing this case, we have been able to conclude that the use of satellite images makes it possible to monitor the risk of freezing, especially under specific mesoscale circumstances. Acknowledgements S. Fernández-González acknowledges the grant supported from the FPU program (AP 2010-2093). This study was supported by the following grants: GRANIMETRO (CGL2010-15930); MICROMETEO (IPT-310000-2010-22). The authors would like to thank the INTA for its scientific flights.

  17. 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.

  18. Avoiding gas bubble formation during freeze substitution.

    PubMed

    Fisher, D B

    1991-01-01

    Gas bubbles frequently are formed during freeze substitution, especially when tissues are warmed to room temperature. The problem arises largely from the extreme solubility of CO2 in the freeze substitution solvent. Gas bubbles may be minimized by briefly transferring the tissue to freshly chilled solvent before warming to room temperature. PMID:1790241

  19. A Simple Method for Quick-Freezing

    PubMed Central

    BEARER, ELAINE L.; ORCI, LELIO

    2015-01-01

    In conventional freeze-fracture replicas produced from tissue cryoprotected with glycerol, the hydrophobic inner surfaces of membranes are revealed, but hydrophillic structures are obscured in the surrounding ice. Quick-freezing of tissue obviates the need for glycerol, which prevents the removal of this ice by etching or freeze-drying, but the major problem in freezing without glycerol cryoprotection is ice crystal formation. We describe here a simple method for quick-freezing tissue, in the absence of glycerol, on a nitrogen-cooled copper block with a hand-held specimen holder. This method freezes samples well enough to preserve molecular detail that can be revealed by subsequent etching. We show some examples of the quality of this freezing with respect to the visualization of molecular detail in isolated protein molecules such as ferritin and catalase. Furthermore, we show examples of in situ cellular structures that are revealed by this method, and we compare the structure seen in these replicas with structures preserved by quick-freezing at liquid helium temperatures. PMID:26549928

  20. Inherent freeze protection for solar water heaters

    SciTech Connect

    Jeter, S.M.; Leonaitis, L.L.; Leonaitis, L.L.

    1981-05-01

    Research and development of a method for protection of a solar collector from freezing is described. The method is shown to be technically and economically feasible. A prototype water heating system using the inherent freeze protection method was successfully operated during the winter of 1980 to 1981.

  1. HOST CADAVERS PROTECT ENTOMOPATHOGENIC NEMATODES DURING FREEZING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four species of insect-killing nematodes were exposed to freezing temperatures while inside their hosts. Survival was assessed by observing live and dead nematodes inside cadavers and by counting the infective juveniles (IJs) tht emerged after freezing. We 1) measured the effects of 24 hours of fr...

  2. Bioinspired Design: Magnetic Freeze Casting

    NASA Astrophysics Data System (ADS)

    Porter, Michael Martin

    Nature is the ultimate experimental scientist, having billions of years of evolution to design, test, and adapt a variety of multifunctional systems for a plethora of diverse applications. Next-generation materials that draw inspiration from the structure-property-function relationships of natural biological materials have led to many high-performance structural materials with hybrid, hierarchical architectures that fit form to function. In this dissertation, a novel materials processing method, magnetic freeze casting, is introduced to develop porous scaffolds and hybrid composites with micro-architectures that emulate bone, abalone nacre, and other hard biological materials. This method uses ice as a template to form ceramic-based materials with continuously, interconnected microstructures and magnetic fields to control the alignment of these structures in multiple directions. The resulting materials have anisotropic properties with enhanced mechanical performance that have potential applications as bone implants or lightweight structural composites, among others.

  3. Homogeneous freezing nucleation of stratospheric solution droplets

    NASA Technical Reports Server (NTRS)

    Jensen, Eric J.; Toon, Owen B.; Hamill, Patrick

    1991-01-01

    The classical theory of homogeneous nucleation was used to calculate the freezing rate of sulfuric acid solution aerosols under stratospheric conditions. The freezing of stratospheric aerosols would be important for the nucleation of nitric acid trihydrate particles in the Arctic and Antarctic stratospheres. In addition, the rate of heterogeneous chemical reactions on stratospheric aerosols may be very sensitive to their state. The calculations indicate that homogeneous freezing nucleation of pure water ice in the stratospheric solution droplets would occur at temperatures below about 192 K. However, the physical properties of H2SO4 solution at such low temperatures are not well known, and it is possible that sulfuric acid aerosols will freeze out at temperatures ranging from about 180 to 195 K. It is also shown that the temperature at which the aerosols freeze is nearly independent of their size.

  4. 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.

  5. 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

  6. On the freezing precipitation in korea and the basic schemes for its potential prediction

    NASA Astrophysics Data System (ADS)

    Kwon, Sang-Hoon; Byun, Hi-Ryong; Park, Chang-Kyun; Kwon, Hui-Nae

    2016-02-01

    This study aims to improve the forecasting skill for freezing precipitation. A total of 102 freezing precipitation cases were collected in South and North Korea from 2001 onwards. Temperature fields on the ground and in the atmosphere, vertical temperature profiles, geopotential fields, thickness fields and their spatiotemporal variations, and their combinations using the predominant precipitation-type nomograms (P-type nomograms) were classified and investigated to determine whether or not these data could be used as predictors. Results show that 1) the combination of the thicknesses of 1000-850 hPa and 850-700 hPa is recommended for the P-type nomograms for Korea, which is different from that used in the United States in threshold values; 2) 35 out of 72 synoptic situations are possible conditions for freezing precipitation; and 3) 3 groups out of those 35 situations, i.e., the 1000 hPa warmfront group, the mid-level southerly category of 850 hPa, and the mid-layer warm type in the vertical temperature profile, show the greatest frequency. Freezing precipitation occurs only in a small part of a possible area. Therefore, despite the increasing observations in the year-on-year trend, only a few of the cases have been detected. The possibility of observation errors is also one of the biggest problems. Therefore, the need for new equipment, such as a freezing rain detector (FRAD), to detect the phenomenon automatically is required and proposed. A denser observing system of FRADs and an ultra-fine gridded numerical model are suggested as a solution for the prediction of freezing precipitation.

  7. 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.

  8. Mimicking the quasi-random assembly of protein fibers in the dermis by freeze-drying method.

    PubMed

    Ghaleh, Hakimeh; Abbasi, Farhang; Alizadeh, Mina; Khoshfetrat, Ali Baradar

    2015-04-01

    Freeze-drying is extensively used for fabrication of porous materials in tissue engineering and biomedical applications, due to its versatility and use of no toxic solvent. However, it has some significant drawbacks. Conventional freeze-drying technique leads to the production of heterogeneous porous structures with side orientated columnar pores. As the top and bottom surfaces of the sample are not in contact with similar environments, different rates of heat transfer in the surfaces and the temperature gradient across the sample establish the preferential direction of heat transfer. To achieve a scaffold with a desirable microstructure for skin tissue engineering, freeze-drying method was modified by controlling the rate of cooling and regulation of heat transfer across the sample during the freezing step. It could create a homogeneous porous structure with more equiaxed non-oriented pores. Freezing the polymeric solution in the aluminum mold enhanced pore interconnectivity relative to the polystyrene mold. Recrystallization process was discussed how to influence the mean pore size of the scaffold when the final freezing temperature varied. Higher final freezing temperature can easily provide the energy required for the recrystallization process, which lead to enlarged ice crystals and resulting pores. PMID:25687012

  9. 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.

  10. 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

  11. Fast acclimation of freezing resistance suggests no influence of winter minimum temperature on the range limit of European beech.

    PubMed

    Lenz, Armando; Hoch, Günter; Vitasse, Yann

    2016-04-01

    Low temperature extremes drive species distribution at a global scale. Here, we assessed the acclimation potential of freezing resistance in European beech (Fagus sylvaticaL.) during winter. We specifically asked (i) how do beech populations growing in contrasting climates differ in their maximum freezing resistance, (ii) do differences result from genetic differentiation or phenotypic plasticity to preceding temperatures and (iii) is beech at risk of freezing damage in winter across its distribution range. We investigated the genetic and environmental components of freezing resistance in buds of adult beech trees from three different populations along a natural large temperature gradient in north-western Switzerland, including the site holding the cold temperature record in Switzerland. Freezing resistance of leaf primordia in buds varied significantly among populations, with LT50values (lethal temperature for 50% of samples) ranging from -25 to -40 °C, correlating with midwinter temperatures of the site of origin. Cambial meristems and the pith of shoots showed high freezing resistance in all three populations, with only a trend to lower freezing resistance at the warmer site. After hardening samples at -6 °C for 5 days, freezing resistance of leaf primordia increased in all provenances by up to 4.5 K. After additional hardening at -15 °C for 3 days, all leaf primordia were freezing resistant to -40 °C. We demonstrate that freezing resistance ofF. sylvaticahas a high ability to acclimate to temperature changes in winter, whereas the genetic differentiation of freezing resistance among populations seems negligible over this small geographic scale but large climatic gradient. In contrast to the assumption made in most of the species distribution models, we suggest that absolute minimum temperature in winter is unlikely to shape the cold range limit of beech. We conclude that the rapid acclimation of freezing resistance to winter temperatures allows beech to track changing climatic conditions, especially during unusually warm winters interrupted by very cold weather. PMID:26888891

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

    SciTech Connect

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

    2015-02-14

    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.

  13. Vertical sleeve gastrectomy

    MedlinePlus

    Gastrectomy - sleeve; Gastrectomy - greater curvature; Gastrectomy - parietal; Gastric reduction; Vertical gastroplasty ... been able to lose weight through diet and exercise. Vertical sleeve gastrectomy is not a quick fix ...

  14. Freeze Denaturation of Fish Muscle Proteins

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Takahide

    Studies on the freeze denaturation of fish muscle proteins were reviewed with emphasis given to changes in their physicochemical and biochemical properties during frozen storage. Denaturation of actomyosin commonly occurs during frozen storage and side-to-side aggregation of myosin molecules apppears to major role in this reaction. The author's group performed freezing studies with isolated preparations of proteins from carp muscle, namely actomyosin, myosin, H-meromyosin, L-meromyosin, and actin. Freeze denaturation occurred with indvidual proteins as well as with their subunits. Not only aggregation but also some conformational changes were observed. Denaturation was inhibited in the presence of added glutamate.

  15. Investigating the Mpemba Effect: When Hot Water Freezes Faster than Cold Water

    ERIC Educational Resources Information Center

    Ibekwe, R. T.; Cullerne, J. P.

    2016-01-01

    Under certain conditions a body of hot liquid may cool faster and freeze before a body of colder liquid, a phenomenon known as the Mpemba Effect. An initial difference in temperature of 3.2 °C enabled warmer water to reach 0 °C in 14% less time than colder water. Convection currents in the liquid generate a temperature gradient that causes more…

  16. Freeze concentration beats the heat

    SciTech Connect

    Rosen, J.

    1990-12-01

    This paper reports on freeze concentration (FC) which saves energy and money in packaging, shipping, and storing food products. FC---in contrast to existing heat-evaporation processes---retains volatile flavor and aroma compounds in food products so that no additives are required to restore the taste and smell of the original product. In recent tests on orange, grapefruit, and pineapple juices, reconstituted FC juices were found to be superior in taste to juices produced by evaporation and similar to the original pasteurized juices. The dairy industry, which is the largest user of energy for concentration in the food sector, is looking to FC for new products such as frozen concentrated milk as well as better use of the milk by-products of cheese production. The biggest potential for new FC applications is in those industries that consume large amounts of energy for separation processing, according to a 1987 report prepared for EPRI. In the food industry, this includes milk, vinegar, and beer producers. Potential applications also abound in the pulp and paper, pharmaceutical, chemical, and petroleum industries. FC separates substances via crystallization at substantial energy savings.

  17. Evaluation of spin freezing versus conventional freezing as part of a continuous pharmaceutical freeze-drying concept for unit doses.

    PubMed

    De Meyer, L; Van Bockstal, P-J; Corver, J; Vervaet, C; Remon, J P; De Beer, T

    2015-12-30

    Spin-freezing as alternative freezing approach was evaluated as part of an innovative continuous pharmaceutical freeze-drying concept for unit doses. The aim of this paper was to compare the sublimation rate of spin-frozen vials versus traditionally frozen vials in a batch freeze-dryer, and its impact on total drying time. Five different formulations, each having a different dry cake resistance, were tested. After freezing, the traditionally frozen vials were placed on the shelves while the spin-frozen vials were placed in aluminum vial holders providing radial energy supply during drying. Different primary drying conditions and chamber pressures were evaluated. After 2h of primary drying, the amount of sublimed ice was determined in each vial. Each formulation was monitored in-line using NIR spectroscopy during drying to determine the sublimation endpoint and the influence of drying conditions upon total drying time. For all tested formulations and applied freeze-drying conditions, there was a significant higher sublimation rate in the spin-frozen vials. This can be explained by the larger product surface and the lower importance of product resistance because of the much thinner product layers in the spin frozen vials. The in-line NIR measurements allowed evaluating the influence of applied drying conditions on the drying trajectories. PMID:25981618

  18. Vertical temperature gradients on Uranus - Implications for layered convection

    NASA Technical Reports Server (NTRS)

    Gierasch, Peter J.; Conrath, Barney J.

    1987-01-01

    Analyses of Voyager IR spectroscopy and radio occultation measurements confirm ground-based observations that the deep lapse rate of Uranus exceeds that for an adiabat of H2 in thermodynamic equilibrium. However, in approximately the same region of the atmosphere, Voyager IR and ground-based observations also indicate that the ratio of ortho to para hydrogen is near the equilibrium value. These two sets of observations can be reconciled by postulating the existence of rapid convective overturning within layers which are thin in comparison to a pressure scale height. Two forms of layered convection are examined. In one case, deposition of kinetic energy results in thin, rapidly overturning layers. Possible kinetic energy sources include braking waves and local instabilities. In the second case considered, molecular-weight discontinuities due to CH4 stratification stabilize the interfaces of thin layers. It is argued that both forms may be important in the convective portion of the Uranus atmosphere.

  19. About the vertical gradient of composition in Titan's lakes

    NASA Astrophysics Data System (ADS)

    Cordier, D.; Roussel, J.; Rannou, P.

    2015-10-01

    The hydrocarbons seas of Titan, discovered by Cassini/Huygens mission are among the most interesting features of this object. However, their chemical composition remains not well known. Due to the presence of the methane in the atmosphere, only a few indications favoring the existence of some amount of ethane in Ontario Lacus have been brought by observations reported in [2, 10]. Several numerical models have been proposed: Dubouloz et al. (1989), Cordier et al. (2009,2013) based on the Regular Solution Theory, Glein et al. (2013) [4] and Tan et al. (2013) [13] respectively based on a RST family model and on the advanced equation of state PC-SAFT1 [5, 13, 10, 3]. The atmosphere of Titan is dominated by nitrogen and contains a few percents of methane. The latter, photolyzed by solar radiations in the stratosphere, gives rise to a complex organic chemistry yielding to the production of a plethora of compounds [7]. According to numerical models, the most abundant species, produced by photochemistry, should be ethane. Then, the bulk composition of Titan's lakes can reasonably regarded as a mixture of methane and ethane, withsome amount of dissolved N2. This latter has a melting temperature (63.3 K) much below than that for methane (around 91 K) and ethane (101 K determined by Streng, 1971; 89.2 K measured by Timmermans,1935); as the ground temperature of Titan in the range 90-95K, the nitrogenmay play a role of an antifreezing solute.

  20. Automated Assessment of Pavlovian Conditioned Freezing and Shock Reactivity in Mice Using the Video Freeze System

    PubMed Central

    Anagnostaras, Stephan G.; Wood, Suzanne C.; Shuman, Tristan; Cai, Denise J.; LeDuc, Arthur D.; Zurn, Karl R.; Zurn, J. Brooks; Sage, Jennifer R.; Herrera, Gerald M.

    2009-01-01

    The Pavlovian conditioned freezing paradigm has become a prominent mouse and rat model of learning and memory, as well as of pathological fear. Due to its efficiency, reproducibility and well-defined neurobiology, the paradigm has become widely adopted in large-scale genetic and pharmacological screens. However, one major shortcoming of the use of freezing behavior has been that it has required the use of tedious hand scoring, or a variety of proprietary automated methods that are often poorly validated or difficult to obtain and implement. Here we report an extensive validation of the Video Freeze system in mice, a “turn-key” all-inclusive system for fear conditioning in small animals. Using digital video and near-infrared lighting, the system achieved outstanding performance in scoring both freezing and movement. Given the large-scale adoption of the conditioned freezing paradigm, we encourage similar validation of other automated systems for scoring freezing, or other behaviors. PMID:20953248

  1. 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.

  2. Freeze-thaw stability of water-in-oil emulsions.

    PubMed

    Ghosh, S; Rousseau, D

    2009-11-01

    Factors influencing water-in-oil emulsion stability during freeze/thaw-cycling, namely interfacial crystallization vs. network crystallization and the sequence of crystallization events (i.e., dispersed vs. continuous phase or vice versa), are assessed. We show that destabilization is most apparent with a liquid-state emulsifier and a continuous oil phase that solidifies prior to the dispersed phase. Emulsions stable to F/T-cycling are obtained when the emulsifier crystallizes at the oil-water interface or in emulsions where the continuous phase crystallizes after the dispersed aqueous phase. The materials used are two food-grade oil-soluble emulsifiers - polyglycerol polyricinoleate (PGPR) and glycerol monostearin (GMS) and two continuous oil phases with differing crystallization temperatures - canola oil and coconut oil. Emulsion stability is assessed with pulsed field gradient NMR droplet size analysis, sedimentation, microscopy and differential scanning calorimetry. This study demonstrates the sequence of crystallization events and the physical state of the surfactant at the oil-water interface strongly impact the freeze-thaw stability of water-in-oil emulsions. PMID:19683718

  3. 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.

  4. Freeze-thaw cycles as drivers of complex ribozyme assembly

    PubMed Central

    Mutschler, Hannes; Wochner, Aniela; Holliger, Philipp

    2015-01-01

    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. PMID:25991529

  5. Freeze-thaw cycles as drivers of complex ribozyme assembly.

    PubMed

    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. PMID:25991529

  6. Evaluation of anti-freeze viscosity modifier for potential external tank applications

    NASA Technical Reports Server (NTRS)

    Lynn, R. O. L.

    1981-01-01

    Viscosity modifiers and gelling agents were evaluated in combination with ethylene glycol and dimethyl sulfoxide water eutectics. Pectin and agarose are found to gel these eutectics effectively in low concentration, but the anti-freeze protection afforded by these compositions is found to be marginal in simulations of the intended applications. Oxygen vent shutters and vertical metallic surfaces were simulated, with water supplied as a spray, dropwise, and by condensation from the air.

  7. [Freezing and gait disorders in Parkinson's disease].

    PubMed

    Gonçalves, Giovanna; Pereira, João

    2013-06-01

    More than one third of patients with Parkinson disease experience freezing. It is characterized by the feeling that one's feet are "glued to the floor", and it is more common in the later stages of the disease. The causes of this gait disorder are not yet fully established, but it may lead patients to suffer falls and lose their independence. As a consequence, the development of therapeutic measures which can overcome freezing is of fundamental important for the autonomy of such individuals. There is no consensus in the literature on the most recommended therapeutic measures for the prevention or attenuation of freezing in gait. What seems to be defined are the phenomenological aspects of the disorder and good therapy, represented by the association between drug therapy and sensorial stimuli or motor coordination training geared towards the specificities to avoid motor difficulties of freezing, when triggering factors are present. PMID:24121579

  8. Cell-encapsulating droplet formation and freezing

    NASA Astrophysics Data System (ADS)

    Ryoun Youn, Jae; Seok Song, Young

    2012-09-01

    Cell-encapsulating droplets are vitrified for biopreservation applications. The dynamics of micro-droplet formation and its freezing mechanism are analyzed numerically and experimentally. In addition, the microdroplet encapsulation technique is applied to cryopreserve cells.

  9. Freezing tolerance of conifer seeds and germinants.

    PubMed

    Hawkins, B J; Guest, H J; Kolotelo, D

    2003-12-01

    Survival after freezing was measured for seeds and germinants of four seedlots each of interior spruce (Picea glauca x engelmannii complex), lodgepole pine (Pinus contorta Dougl. ex Loud.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata Donn ex D. Donn). Effects of eight seed treatments on post-freezing survival of seeds and germinants were tested: dry, imbibed and stratified seed, and seed placed in a growth chamber for 2, 5, 10, 15, 20 or 30 days in a 16-h photoperiod and a 22/17 degrees C thermoperiod. Survival was related to the water content of seeds and germinants, germination rate and seedlot origin. After freezing for 3 h at -196 degrees C, dry seed of most seedlots of interior spruce, Douglas-fir and western red cedar had 84-96% germination, whereas lodgepole pine seedlots had 53-82% germination. Freezing tolerance declined significantly after imbibition in lodgepole pine, Douglas-fir and interior spruce seed (western red cedar was not tested), and mean LT50 of imbibed seed of these species was -30, -24.5 and -20 degrees C, respectively. Freezing tolerance continued to decline to a minimum LT50 of -4 to -7 degrees C after 10 days in a growth chamber for interior spruce, Douglas-fir and lodgepole pine, or after 15 days for western red cedar. Minimum freezing tolerance was reached at the stage of rapid hypocotyl elongation. In all species, a slight increase in freezing tolerance of germinants was observed once cotyledons emerged from the seed coat. The decrease in freezing tolerance during the transition from dry to germinating seed correlated with increases in seed water content. Changes in freezing tolerance between 10 and 30 days in the growth chamber were not correlated with seedling water content. Within a species, seedlots differed significantly in freezing tolerance after 2 or 5 days in the growth chamber. Because all seedlots of interior spruce and lodgepole pine germinated quickly, there was no correlation between seedlot hardiness and rate of germination. Germination rate and freezing tolerance of Douglas-fir and western red cedar seedlots was negatively correlated. There was a significant correlation between LT50 after 10 days in the growth chamber and minimum spring temperature at the location of seedlot origin for interior spruce and three seedlots of western red cedar, but no relationship was apparent for lodgepole pine and Douglas-fir. PMID:14652223

  10. Notes on the freezing of simple substances

    SciTech Connect

    Stishov, S. M.

    2006-08-15

    Experimental data on the freezing of argon and the helium isotopes at high pressures are analyzed. It is found that attractive forces in argon can be adequately described by the van der Waals mean field theory. An analogous approximation may also be applicable to helium, but this cannot be established conclusively because of quantum effects. However, an analysis of experimental results on the freezing of helium intuitively suggests that the solid-phase stability region is enlarged by quantum effects.

  11. Freezing of living cells: mechanisms and implications

    SciTech Connect

    Mazur, P.

    1984-01-01

    Cells can endure storage at low temperatures such as -196/sup 0/C for centuries. The challenge is to determine how they can survive both the cooling to such temperatures and the subsequent return to physiological conditions. A major factor is whether they freeze intracellularly. They do so if cooling is too rapid, because with rapid cooling insufficient cell water is removed osmotically to eliminate supercooling. Equations have been developed that describe the kinetics of this water loss and permit one to predict the likelihood of intracellular freezing as a function of cooling rate. Such predictions agree well with observations. Although the avoidance of intracellular freezing is usually necessary for survival, it is not sufficient. Slow freezing itself can be injurious. As ice forms outside the cell, the residual unfrozen medium forms channels of decreasing size and increasing solute concentration. The cells lie in the channels and shrink in osmotic response to the rising solute concentration. Prior theories have ascribed slow freezing injury to the concentration of solutes or the cell shrinkage. Recent experiments, however, indicate that the damage is due more to the decrease in the size of the unfrozen channels. This new view of the mechanism of slow freezing injury ought to facilitate the development of procedures for the preservation of complex assemblages of cells of biological, medical, and agricultural significance. 126 references, 18 figures, 2 tables.

  12. 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.

  13. Impacts from Time-dependent Freezing of Rain and Wet Hail on Deep Convection Simulated by a Cloud Model with Spectral Bin Microphysics

    NASA Astrophysics Data System (ADS)

    Phillips, V. T.; Khain, A.; Ilotoviz, E.; BenMoshe, N.

    2014-12-01

    Any hydrometeor containing some supercooled liquid can only freeze it as fast as latent heat is dissipated to the ambient air. Consequently, at sub-zero temperatures any given particle in a cloud can contain both ice and liquid water. Wet growth of hail occurs when supercooled cloud-liquid is accreted faster than it can freeze immediately on impact. Equally, raindrops in clear air can take up to a few mins to freeze. A new theory of time-dependent freezing is proposed in this presentation. First, wet growth of hail is represented by treating inhomogeneities of liquid coverage and temperature over the surface of the particle. Radial heat fluxes from the sponge layer through the liquid skin to the air are predicted, as well as heat fluxes between its wet and dry parts. Gradual internal freezing of liquid that soaks the interior of the hail or graupel particle during dry growth ('riming') is represented. The microphysical recycling with alternating episodes of wet and dry growth is predicted. Second, the time-dependent process of raindrop freezing is represented by including thermodynamic effects from accretion of cloud-liquid and -ice. Freezing drops larger than about 0.1 mm are represented as a new microphysical species in a cloud model with spectral bin microphysics. The freezing drops consist of interior water covered by ice initially. Possibilities of both dry and wet growth of freezing drops are represented. Schemes of time-dependent freezing for rain and wet growth of hail and graupel were implemented in a spectral bin microphysics cloud model. The model predicted that accretion of liquid produces giant freezing drops of 0.5-2 cm in diameter, due to downdraft-updraft recirculation and wet growth of freezing drops. Appreciable contents of freezing drops reach a height level of 7 km (-30 degC) in the simulated storm. The critical diameter separating wet and dry growth regimes is predicted to increase with height for freezing drops. It is more vertically uniform for hail. A sensitivity test with the cloud model shows that time-dependent freezing delays formation of the first hail. Later in the mature stage of the storm, it boosts hail amounts. Convection is invigorated. Hail and freezing drops are upwelled to higher levels, and hail grows to sizes up to twice as large, than without time-dependent freezing.

  14. Gradient echo imaging.

    PubMed

    Markl, Michael; Leupold, Jochen

    2012-06-01

    Magnetic resonance imaging (MRI) based on gradient echoes is used in a wide variety of imaging techniques and clinical applications. Gradient echo sequences form the basis for an essential group of imaging methods that find widespread use in clinical practice, particularly when fast imaging is important, as for example in cardiac MRI or contrast-enhanced MR angiography. However, the term "gradient echo sequence" is somewhat unspecific, as even images acquired with the most common sequences employing the gradient echo for data acquisition can significantly differ in signal, contrast, artifact behavior, and sensitivity to, eg, flow. This is due to the different use of sequence timing and basic sequence building blocks such as spoiler gradients or specific radiofrequency (RF) pulse phase patterns. In this article the basic principles of gradient echo formation compared to spin echo imaging are reviewed and the properties of gradient echo imaging in its simplest form (TR ? T(2)) are described. Further, the most common three variants of fast gradient echo sequences (TR < T(2)), namely, unbalanced gradient echo, RF spoiled gradient echo, and balanced steady state free precession; are discussed. For each gradient echo sequence type, examples of applications exploiting the specific properties of the individual technique are presented. PMID:22588993

  15. A new freeze casting technique for ceramics

    NASA Astrophysics Data System (ADS)

    Araki, Kiyoshi

    A new freeze casting technique for ceramics capable of manufacturing near room temperature with a sublimable vehicle has been developed in order to eliminate expensive processes under extremely cold temperatures in the conventional freeze casting. Fluid concentrated slurries of Al2O 3 powder in molten camphene (C10H16) were successfully prepared at 55°C with a small amount of a dispersant. These slurries were quickly solidified (frozen) at room temperature to yield a rigid solid green body, where the frozen camphene was easily removed by sublimation (freeze-drying) with negligible shrinkage. Sintering was successfully conducted without any special binder burnout process to yield dense sintered bodies (over 98% T.D). An organic alloy with a eutectic composition in the naphthalene (C 10H8)-camphor (C10H16O) binary system with a eutectic temperature of 31°C was also found to be a successful vehicle for the new ceramic freeze casting. The fabrication processes are almost the same as those with camphene. It was found that vehicles with off-eutectic compositions resulted in large voids in the sintered body due to the ceramic particle rejection by pro-eutectic crystals during freezing. At the eutectic composition, fine lamellar microstructure in the solidified vehicle inhibits the particle rejection. The proposed advantages of the new freeze casting technique with a sublimable vehicle include; (1) elimination of extremely cold temperatures used in conventional freeze casting; (2) elimination of troublesome binder burnout process; and (3) fast manufacturing cycle due to quick solidification. Porous ceramic bodies with unique interconnected pore channels were fabricated by the new freeze casting with lower solid content. The unique channels surrounded by fully dense walls have nearly circular cross-sections unlike conventional aqueous freeze casting. The porosity and the channel diameters are controllable by the solid content in the slurry. The unique channels are replicas of entangled dendrites of frozen camphene, which sublimes during freeze-drying process. The unique porous structure with interconnected pore channels, which is completely new, is considered potentially useful in many applications such as filters and implantable bone scaffolds.

  16. 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.

  17. A thermobaric instability of Lagrangian vertical coordinate ocean models

    NASA Astrophysics Data System (ADS)

    Hallberg, Robert

    Lagrangian- (and isopycnic-) vertical coordinate ocean models are subject to an exponentially growing numerical instability in weakly stratified regions when thermobaricity is not accurately compensated. Inaccurate compensation for compressibility in the pressure gradient terms leads to pressure gradient truncation errors (due to the vertical discretization) that can drive the Lagrangian coordinate surfaces to reinforce these errors. It is possible to avoid this instability while using the full non-linear equation of state for seawater by using an optimal alternate discretization of the pressure gradient terms and extracting a slowly spatially varying reference compressibility that approximates the compressibility of the ocean's mean state.

  18. Freezing and thawing or freezing, thawing, and aging effects on beef tenderness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL) and semitendinosus (ST) steaks relative to aged, fresh steaks. Left-side LL and ST (n=35 each) ...

  19. 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...

  20. Freeze Tolerance of Nine Zoysiagrass Cultivars Using Natural Cold Acclimation and Freeze Chambers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Winter hardiness of zoysiagrass (Zoysia spp.) cultivars is an important attribute throughout the biogeographical transition zone, thus the inability to withstand freezing temperatures may limit the use of these cultivars. The objective of this research was to determine the freeze tolerance (LT50) of...

  1. The role of calcium and calmodulin in freezing-induced freezing resistance of Populus tomentosa cuttings.

    PubMed

    Lin, Shan-Zhi; Zhang, Zhi-Yi; Lin, Yuan-Zhen; Zhang, Qian; Guo, Huan

    2004-02-01

    To explore the role of calcium-calmodulin messenger system in the transduction of low temperature signal in woody plants, Populus tomentosa cuttings after being treated with CaCl(2) (10 mmol/L), Ca(2+) chelator EGTA (3 mmol/L), Ca(2+) channel inhibitor LaCl(3) (100 mmol/L) or CaM antagonist CPZ (50 mmol/L) were used for freezing acclimation at -3 degrees C. The changes in the calmodulin (CaM) and malonaldehyde (MDA) contents, the activities of superoxide dismutase (SOD), peroxidase (POD) and Ca(2+)-dependent adenosinetriphosphatase (Ca(2+)-ATPase) of mitochondrial membrane as well as freezing resistance (expressed as LT(50)) of cuttings were investigated to elucidate the physiological mechanisms by which trees adapt to freezing. The results showed that freezing acclimation increased the CaM content, the activities of SOD, POD and Ca(2+)-ATPase of mitochondrial membrane as well as freezing resistance of cuttings, and decreased the MDA content as compared with control cuttings. Treatment with CaCl(2) at the time of freezing acclimation enhanced the effect of freezing acclimation on the above-mentioned indexes, but this enhancement was abolished by Ca(2+)chelator EGTA, Ca(2+) channel inhibitor LaCl(3) or CaM antagonist CPZ, indicating that the calcium-calmodulin messenger system was involved in the course of freezing resistance development. The presence of CaCl(2) at the same time of freezing acclimation also reduced the degree of decline in CaM content, and in SOD, POD and Ca(2+)-ATPase activities caused by freezing stress at -14 degrees C, and enhanced the level of increase in CaM content, and in SOD, POD and Ca(2+)-ATPase activity in the recovery periods at 25 degrees C . The change in CaM content was found to be closely correlated to the levels of SOD, POD and Ca(2+)-ATPase, and to the degree of freezing resistance of cuttings during freezing acclimation either with or without CaCl(2) treatment. It was suggested that the increase of CaM content induced by CaCl(2) treatment promote the formation of Ca(2+)-CaM complexes, which effectively activates the activities of SOD, POD and mitochondrial Ca(2+)-ATPase and then further result in the adaptive changes associated with the development and enhancement of freezing resistance. Thus, It could be concluded that Ca(2+)-calmodulin may be involved in the regulation of the increase in SOD, POD and Ca(2+)-ATPase activities, and the induction of freezing resistance of cuttings. PMID:15583410

  2. Effect of freezing rate and dendritic ice formation on concentration profiles of proteins frozen in cylindrical vessels.

    PubMed

    Rodrigues, Miguel A; Miller, Maria A; Glass, Matt A; Singh, Satish K; Johnston, Keith P

    2011-04-01

    The process of freezing protein solutions can perturb the conformation of the protein and potentially lead to aggregate formation during long-term storage in the frozen state. Radial macroscopic freeze concentration and temperature profiles for bovine serum albumin (BSA) solutions in small cylindrical stainless steel vessels were determined for various freezing rates. The measured concentrations of both BSA and immunoglobulin G2, as well as trehalose in sampled ice sections, increased by up to twofold to threefold toward the bottom and radial center for slow freezing rates produced in stagnant air freezers. The concentration and temperature profiles result in density gradients that transport solutes by convective flow. For faster external cooling by either forced convection of air or a liquid coolant, the increased freezing rate raised the ice front velocity resulting in enhanced dendritic ice growth. The ice trapped the solutes more effectively before they were removed from the ice front by diffusion and convection, resulting in more uniform solute concentration profiles. The dynamic temperature profiles from multiple radial thermocouples were consistent with the independently measured freeze concentration profiles. The ability to control the protein concentration profile in the frozen state offers the potential to improve stability of protein in long-term frozen storage. PMID:24081467

  3. Freezing of Lennard-Jones-type fluids

    SciTech Connect

    Khrapak, Sergey A.; Chaudhuri, Manis; Morfill, Gregor E.

    2011-02-07

    We put forward an approximate method to locate the fluid-solid (freezing) phase transition in systems of classical particles interacting via a wide range of Lennard-Jones-type potentials. This method is based on the constancy of the properly normalized second derivative of the interaction potential (freezing indicator) along the freezing curve. As demonstrated recently it yields remarkably good agreement with previous numerical simulation studies of the conventional 12-6 Lennard-Jones (LJ) fluid [S.A.Khrapak, M.Chaudhuri, G.E.Morfill, Phys. Rev. B 134, 052101 (2010)]. In this paper, we test this approach using a wide range of the LJ-type potentials, including LJ n-6 and exp-6 models, and find that it remains sufficiently accurate and reliable in reproducing the corresponding freezing curves, down to the triple-point temperatures. One of the possible application of the method--estimation of the freezing conditions in complex (dusty) plasmas with ''tunable'' interactions--is briefly discussed.

  4. 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

  5. Droplet coalescence and freezing on hydrophilic, hydrophobic, and biphilic surfaces

    NASA Astrophysics Data System (ADS)

    Van Dyke, Alexander S.; Collard, Diane; Derby, Melanie M.; Betz, Amy Rachel

    2015-10-01

    Frost and ice formation can have severe negative consequences, such as aircraft safety and reliability. At atmospheric pressure, water heterogeneously condenses and then freezes at low temperatures. To alter this freezing process, this research examines the effects of biphilic surfaces (surfaces which combine hydrophilic and hydrophobic regions) on heterogeneous water nucleation, growth, and freezing. Silicon wafers were coated with a self-assembled monolayer and patterned to create biphilic surfaces. Samples were placed on a freezing stage in an environmental chamber at atmospheric pressure, at a temperature of 295 K, and relative humidities of 30%, 60%, and 75%. Biphilic surfaces had a significant effect on droplet dynamics and freezing behavior. The addition of biphilic patterns decreased the temperature required for freezing by 6 K. Biphilic surfaces also changed the size and number of droplets on a surface at freezing and delayed the time required for a surface to freeze. The main mechanism affecting freezing characteristics was the coalescence behavior.

  6. Freeze thaw cycles in Toronto, Canada in a changing climate

    NASA Astrophysics Data System (ADS)

    Ho, E.; Gough, W. A.

    2006-01-01

    Freeze thaw cycles are examined in Toronto Canada. Using data from 1960 to 1989 for three Toronto area weather stations, trends in freeze thaw activity, the relationship to mean monthly temperature and projections of freeze thaw activity are examined. For downtown Toronto the annual frequency of freeze thaw cycles is decreasing significantly, most notably in the shoulder months of October and April. At the Pearson International Airport and the Toronto Island Airport similar annual trends were not found, however there was evidence of decreased freeze thaw activity in April and October. Polynomial curve fitting provided functional relationships between mean monthly temperature and freeze thaw activity. These relationships enabled the assessment of freeze thaw activity under synthetic warming conditions. The results of this analysis show that the warming of the magnitude typically projected for the rest of this century will not likely generate a significant change in the freeze thaw activity although there are indications that the freeze thaw season will contract.

  7. 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.

  8. Freezing promotes perception of coarse visual features.

    PubMed

    Lojowska, Maria; Gladwin, Thomas E; Hermans, Erno J; Roelofs, Karin

    2015-12-01

    Freezing is an evolutionarily preserved defensive behavior, characterized by immobility and heart rate deceleration, which is thought to promote visual perception. Rapid perceptual assessment of threat is crucial in life-threatening situations; for example, when policemen need to make split-second decisions about the use of deadly force. Here, we hypothesized that freezing is specifically associated with better perception of rapidly processed coarse, low-spatial frequency (LSF) features. We used a visual discrimination task in which participants determined the orientation of LSF and high-spatial frequency (HSF) gratings under threat of shock and safe conditions. As predicted, threat anticipation improved perception of LSF at the expense of HSF gratings. Crucially, stronger decrease in heart rate, a parasympathetic physiological index of freezing, was linked to better perception of LSF. These results provide empirical evidence for the comobilization of physiological and perceptual processes, which may play an important role in decision making under acute stress. PMID:26595839

  9. 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

  10. UltraViolet freeze-in

    NASA Astrophysics Data System (ADS)

    Elahi, Fatemeh; Kolda, Christopher; Unwin, James

    2015-03-01

    If dark matter is thermally decoupled from the visible sector, the observed relic density can potentially be obtained via freeze-in production of dark matter. Typically in such models it is assumed that the dark matter is connected to the thermal bath through feeble renormalisable interactions. Here, rather, we consider the case in which the hidden and visible sectors are coupled only via non-renormalisable operators. This is arguably a more generic realisation of the dark matter freeze-in scenario, as it does not require the introduction of diminutive renormalisable couplings. We examine general aspects of freeze-in via non-renormalisable operators in a number of toy models and present several motivated implementations in the context of Beyond the Standard Model (BSM) physics. Specifically, we study models related to the Peccei-Quinn mechanism and Z ' portals.

  11. High-speed Imaging of Freezing Drops: Investigating the Role of Point-like Contact in Heterogeneous Ice Nucleation

    NASA Astrophysics Data System (ADS)

    Gurganus, C.; Charnawskas, J.; Shaw, R. A.; Kostinski, A. B.

    2013-12-01

    Formation of ice by contact nucleation remains enigmatic and the possible role of the three-phase boundary (i.e., liquid water-ice-aerosol contact line) is still undetermined. Because aerosol size, surface area, composition and exact region of contact remain difficult to measure, we examine a simpler geometry with a spherical cap droplet resting on a substrate. In this configuration, the droplet simultaneously experiences a two-phase immersion region and a three phase contact region around the perimeter of the droplet. Utilizing high speed imaging of the droplet-substrate plane, we are able to identify nucleation sites in individual droplets. This technique allows for a spatial distribution of freezing sites in addition to a freezing temperature distribution. Our initial study indicated no preference for nucleation originating at the three phase boundary for an atomically smooth homogenous substrate [1]. The nucleation site distribution agreed well with the stochastic view in that the germ sites are distributed uniformly over the surface area. In that study we minimized the thermal variation (?T) across a droplet during cooling to prevent biased observations. We also compared ?T for several experiments in literature using a simple formulation of droplet size (r) and cooling rate (?). Large variations in some experiments could possibly explain observed 'contact nucleation' events in the laboratory as artifacts of radial thermal variations during droplet cooling. As a continuation of this study, we redesigned our system to enable much greater substrate cooling rates, but these experiments too revealed no preference for nucleation in the contact mode. Thermal modeling of the new system confirmed that while a vertical thermal gradient does develop within the droplet, no horizontal gradient is induced in the drop near the substrate. This result argues against a thermodynamic bias toward contact nucleation in substrate cooled geometries. Another possible explanation for this contact phenomenon comes in a lowering of the energy barrier for nucleation due to the existence of a line tension at the point of contact. A scale analysis of the line and surface energy values available in the literature suggests that line tension may become dominant below length scales of ~10 nm [1]. From this simple result we postulate that 'point-like' surface features might play an important role at the three phase boundary. To mimic these features on substrates we introduce chemical and mechanical processes to enhance substrate surface roughness. Using these new substrates we repeat our experimental procedure to compare effectiveness of the immersion (two phase) and contact (three phase) regions for a variety of surface topologies. Here we report the initial findings from this work. 1. Gurganus, C.; Kostinski, A. B.; Shaw, R. A., Fast Imaging of Freezing Drops: No Preference for Nucleation at the Contact Line. J Phys Chem Lett 2011, 2 (12) Identifying nucleation sites with two high speed cameras.

  12. 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.

  13. Stratospheric Polar Freezing Belt Causes Denitrification

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Jensen, E. J.; Toon, O. B.; Drdla, K.; Schoeberl, M. R.; Gore, Warren J. (Technical Monitor)

    2001-01-01

    Trajectory cloud model calculations are presented to show that homogeneous freezing of nitric acid hydrates can produce a polar freezing belt in both hemispheres that can cause denitrification. While hydrate cloud microphysical properties are similar over both poles, the shorter persistence of clouds in the Arctic prevents the depth of the denitrified layers from growing beyond a few kilometers. The 1999-2000 Arctic winter is unique in showing a distinct denitrification profile with a depth of approx. 4.5 km that is nearly half as deep as that computed for a typical Antarctic winter.

  14. Effect of vertical magnetic field on convection and segregation in vertical Bridgman crystal growth

    NASA Technical Reports Server (NTRS)

    Kim, Do Hyun; Adornato, Peter M.; Brown, Robert A.

    1988-01-01

    A previous finite-element analysis of vertical Bridgman growth for dilute and nondilute alloys is extended to include the effect of a vertically-aligned magnetic field in the limit of zero magnetic Reynolds number. Calculations are presented for growth of a dilute gallium-germanium alloy in a vertically stabilized Bridgman-Stockbarger system and in a furnace with a uniform temperature gradient imposed along the ampoule. Steady cellular convection driven by radial temperature gradients causes good axial and radial mixing in both systems without a magnetic field. A weak magnetic field decreases the intensity of convection and the effectiveness of solute mixing. The radial nonuniformity is greatest for an intermediate field strength. Stronger fields suppress flow recirculation completely, and lead to uniform solute segregation across the crystal and to diffusion-controlled axial segregation.

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

    PubMed

    Jiang, S; Nail, S L

    1998-05-01

    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, beta-galactosidase and lactate dehydrogenase (LDH) were used as model proteins. All of the three proteins exhibited a concentration-dependent loss of activity after freezing, with significantly higher recovery at higher concentration. The freezing method and the type of buffer were also important, with sodium phosphate buffer and freezing by immersion of vials in liquid nitrogen associated with the lowest recovery of activity. Differential scanning calorimetry was predictive of the onset of collapse during freeze-drying only for beta-galactosidase. For the other proteins, either no Tg' transition was observed, or the apparent glass transition did not correlate with the microscopically-observed collapse temperature. The time course of activity loss for beta-galactosidase and LDH was compared during freeze-drying under conditions which produced collapse of the dried matrix and conditions which produced retention of microstructure in the dried solid. Recovery of activity decreased continuously during primary drying, with no sharp drop in recovery of activity associated with the onset of collapse. The most important drying process variable affecting recovery of activity was residual moisture level, with a dramatic drop in activity recovery associated with residual moisture levels less than about 10%. PMID:9653629

  16. To freeze or not to freeze embryos: clarity, confusion and conflict.

    PubMed

    Goswami, Mohar; Murdoch, Alison P; Haimes, Erica

    2015-06-01

    Although embryo freezing is a routine clinical practice, there is little contemporary evidence on how couples make the decision to freeze their surplus embryos, or of their perceptions during that time. This article describes a qualitative study of 16 couples who have had in vitro fertilisation (IVF) treatment. The study question was 'What are the personal and social factors that patients consider when deciding whether to freeze embryos?' We show that while the desire for a baby is the dominant drive, couples' views revealed more nuanced and complex considerations in the decision-making process. It was clear that the desire to have a baby influenced couples' decision-making and that they saw freezing as 'part of the process'. However, there were confusions associated with the term 'freezing' related to concerns about the safety of the procedure. Despite being given written information, couples were confused about the practical aspects of embryo freezing, which suggests they were preoccupied with the immediate demands of IVF. Couples expressed ethical conflicts about freezing 'babies'. We hope the findings from this study will inform clinicians and assist them in providing support to couples confronted with this difficult decision-making. PMID:25660099

  17. Reproducing Black's experiments: freezing point depression and supercooling of water

    NASA Astrophysics Data System (ADS)

    Güémez, J.; Fiolhais, C.; Fiolhais, M.

    2002-01-01

    We carried out two historical experiments referred to by Joseph Black, one on freezing mixtures of salted water with ice and another on freezing supercooled pure water by a small disturbance. The results confirm thermodynamical predictions for the depression of the freezing point of salted water and for the latent heat of freezing of supercooled water respectively, which came after Black. The depression of the freezing point can hardly be fitted in the framework of the caloric theory of heat, which was taken for granted by Black, and the instantaneous freezing of supercooled water also poses some difficulties for that theory.

  18. Vertical bounce of two vertically aligned balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2007-11-01

    When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

  19. The ice nucleating ability of pollen:. Part II. Laboratory studies in immersion and contact freezing modes

    NASA Astrophysics Data System (ADS)

    Diehl, K.; Matthias-Maser, S.; Jaenicke, R.; Mitra, S. K.

    Laboratory tests were conducted of the ice nucleating ability of four kinds of pollen in the immersion and the contact freezing modes. The diameters of the selected pollen were between 25 and 70 μm. The experiments were carried out at the Mainz vertical wind tunnel with freely suspended supercooled droplets at temperatures down to -28 °C. The immersion freezing experiments were conducted with drops of radii between 250 and 375 μm formed from distilled water with a defined amount of pollen added. The drops were freely floated in the wind tunnel while being supercooled. For the contact freezing experiments, a short burst of pollen was allowed to collide with freely suspended, supercooled pure water drops of 360-μm radius. The results showed that particle-free water drops in particle-free air in the wind tunnel did not freeze at temperatures above -28 °C while water drops containing pollen froze at temperatures as high as -9 °C, and water drops colliding with pollen froze at temperatures -5 °C and lower. Combined with earlier results about the ice nucleating ability of some bacteria, marine plankton, and leaf litters, the present results confirm the importance of biological aerosol particles as potential ice nuclei at relatively warm temperatures.

  20. Freezing Models For Heterogeneous Drop Freezing In Immersion and Contact Modes

    NASA Astrophysics Data System (ADS)

    Diehl, K.; Wurzler, S.

    Field measurements showed that supercooled liquid water drops and frozen drops can coexist in tropospheric clouds at temperatures down to -40 C with an incidence of ice particles already at -4 C. The freezing behaviour of water drops depends on their sizes, on their content of soluble particles (freezing point depression) and of insoluble particles (potential immersion ice nuclei) as well as on the collision with dry particles (potential contact ice nuclei). In the present model studies, the influence of soluble and insoluble particles on drop freezing in immersion and contact modes are considered. Using a two dimensional field of drop and aerosol particle sizes the numerical simula- tion of the coexistence of similar sized drops with different compositions is possible, also the combination of different collision partners. The freezing point depression of salt solution drops was calculated according to physical chemistry equations. The median freezing temperatures of particles in the immersion and contact modes were derived from laboratory results for typical atmospheric ice nuclei. The collision effi- ciency was calculated based on experimental results and numerical estimations. The results obtained with the freezing models are consistent with experimental results. They show that in the whole temperature range relevant for the troposphere the com- position of the drops has an important influence on their freezing in the immersion mode. The smaller the drop sizes, the more effecting are the soluble particles. A sig- nificant influence of insoluble immersion ice nuclei on atmospheric drop f reezing can be expected at temperatures of -20 C and lower, in the contact freezing mode already at temperatures around -10 C, with the different insoluble particles not showing large deviations. However, the freezing efficiency of contact ice nuclei is restricted by the collision efficiency which is dependant on both, the drop and aerosol particle size.

  1. 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.

  2. How low-permeability rocks freeze: A laboratory study on resistivity pathways of thawed, supercooled and frozen permafrost rocks

    NASA Astrophysics Data System (ADS)

    Krautblatter, M.; Zisser, N.

    2009-04-01

    Resistivity - temperature paths are among the most important proxies in permafrost research. Testing 8 sedimentary, metamorphic and igneous rocks from European permafrost summits, we found evidence that the theoretical background developed in the 70s does not describe the physics of low-permability rocks correctly, which dominate these environments. Saturated rocks with permeabilities below 10 D have an equilibrium freezing point depression of -0.5C to -1.55C and indicate metastable supercooling effects between -0.5 and -1.4 C. Instantaneous freezing from metastable stages occurs with sudden warming of the rock sample with up to 0.9C temperature difference. This is due to the spontaneous dissipation of freezing energy subsequent to supercooling. Warming occurs over tens of seconds to a few minutes and coincides with a jump in resistivity. Unfrozen and frozen temperature-resistivity paths match bilinear functions with an R of 0.88 to 1.00. The frozen temperature-resistivity gradient is 12-34 times steeper that the unfrozen resistivity gradient. Low permeability may decide the ratio of frozen and unfrozen gradients while porosity influences the 0C resistivity value and the unfrozen gradient. Here we show that separate linear approximation of unfrozen, supercooled and frozen temperature-resistivity behaviour provides a better explanation of involved physics than exponential fits.

  3. Vertical axis wind turbines

    DOEpatents

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  4. Vertical axis wind turbine

    SciTech Connect

    Kato, Y.; Seki, K.; Shimizu, Y.

    1981-01-27

    Wind turbines are largely divided into vertical axis wind turbines and propeller (Horizontal axis) wind turbines. The present invention discloses a vertical axis high speed wind turbine provided with a starting and braking control system. This vertical axis wind turbine is formed by having blades of a proper airfoil fitted to respective supporting arms provided radially from a vertical rotary axis by keeping the blade span-wise direction in parallel with the axis and being provided with a low speed control windmill in which the radial position of each operating piece varies with a centrifugal force produced by the rotation of the vertical rotary axis.

  5. 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

  6. 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.

  7. 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).

  8. Polybutylene pipe freeze/thaw reliability testing

    SciTech Connect

    Farrington, R.B.

    1987-04-01

    This paper discusses the ability of polybutylene pipe to withstand repeated freezing and thawing. The test apparatus, test procedure, list of chronological events, and results are discussed. Polybutylene piping has potential use in active solar heating systems and integral-collector-storage systems.

  9. Aversive life events enhance human freezing responses.

    PubMed

    Hagenaars, Muriel A; Stins, John F; Roelofs, Karin

    2012-02-01

    In the present study, we investigated the effect of prior aversive life events on freezing-like responses. Fifty healthy females were presented neutral, pleasant, and unpleasant images from the International Affective Picture System while standing on a stabilometric platform and wearing a polar band to assess body sway and heart rate. In the total sample, only unpleasant pictures elicited reduced body sway and reduced heart rate (freezing). Moreover, participants who had experienced 1 or more aversive life events showed greater reductions in heart rate for unpleasant versus pleasant pictures than those who had experienced no such event. In addition, relative to no-event participants, single-event participants showed reduced body sway to unpleasant pictures, while multiple-event participants showed reduced body sway in response to all picture categories. These results indicate that aversive life events affect automatic freezing responses and may indicate the cumulative effect of multiple trauma. The experimental paradigm presented is a promising method to study freezing as a primary defense response in trauma-related disorders. PMID:21767043

  10. Managing damaging freeze events in Louisiana sugarcane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exposure of sugarcane to damaging frosts occurs in approximately 25% of the sugarcane producing countries of the world, but is most frequent on the mainland of the United States, especially in the state of Louisiana. The frequent winter freezes that occur in the sugarcane areas of Louisiana have fo...

  11. 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…

  12. Freeze-thaw induced gelation of alginates.

    PubMed

    Zhao, Ying; Shen, Wei; Chen, Zhigang; Wu, Tao

    2016-09-01

    Adding divalent ions or lowering pH below the pKa values of alginate monomers are common ways in preparing alginate gels. Herein a new way of preparing alginate gels using freeze-thaw technique is described. Solvent crystallization during freezing drove the polymers to associate into certain structures that became the junction zones of hydrogels after thawing. It enabled the preparation of alginate gels at pH 4.0 and 3.5, two pH at which the gel could not be formed previously. At pH 3.0 where alginate gel could be formed initially, applying freeze-thaw treatment increased the gel storage modulus almost 100 times. The formation of hydrogels and the resulting gel properties, such as dynamic moduli and gel syneresis were influenced by the pH values, number of freeze-thaw cycles, alginate concentrations, and ionic strengths. The obtained hydrogels were soft and demonstrated a melting behavior upon storage, which may find novel applications in the biomedical industry. PMID:27185114

  13. Investigating the Mpemba Effect: when hot water freezes faster than cold water

    NASA Astrophysics Data System (ADS)

    Ibekwe, R. T.; Cullerne, J. P.

    2016-03-01

    Under certain conditions a body of hot liquid may cool faster and freeze before a body of colder liquid, a phenomenon known as the Mpemba Effect. An initial difference in temperature of 3.2 °C enabled warmer water to reach 0 °C in 14% less time than colder water. Convection currents in the liquid generate a temperature gradient that causes more rapid heat loss by surface radiation and evaporation than obtains for uniform temperature. This more rapid cooling enables the initially warmer liquid to overtake the cooler liquid, reaching 0 °C earlier and freezing first. Liquid cooling under natural convection follows a five-fourths power law (temperature of liquid T , temperature of surroundings {{T}a} , cooling constant k ): \\frac{\\text{d}T}{\\text{d}t}=k{{≤ft(T-{{T}a}\\right)}\\frac{5{4}}} . In this investigation we found that with evaporation this becomes a four-thirds power law:

  14. Directional freezing of sperm and associated derived technologies.

    PubMed

    Arav, Amir; Saragusty, Joseph

    2016-06-01

    Directional freezing has now completed 30 years of development since it was first introduced to cryobiology. In the field of sperm cryopreservation, directional freezing has been shown to be advantageous over slow freezing for numerous domestic and wildlife species. In particular, it was shown that freezing of large volume is possible. Furthermore, double freezing of sperm and freezing of sex-sorted sperm are possible and became the routine in the sex sorted sperm industry. In wild animals, our labs and others showed that sperm from a wide range of terrestrial and aquatic species can be successfully cryopreserved using directional freezing. Finally, we will describe for the first time the successful freeze-drying of human sperm in an aseptic method. Using a device that produces clean liquid air, we froze human sperm in small droplets and then dried them in a bench top lyophilizer that was sterilized prior to use. More than 80% of DNA integrity was found after rehydration. PMID:26879097

  15. Nucleation Pathways For Freezing Of Two Grades Of Zirconium

    NASA Technical Reports Server (NTRS)

    Rhim, Won-Kyu; Rulison, Aaron; Bayuzick, Robert; Hofmeister, William; Morton, Craig

    1996-01-01

    Report discusses classical nucleation theory of freezing and describes experimental study of nucleation mechanisms that predominate during freezing of spherical specimens of initially molten zirconium levitated electrostatically in vacuum.

  16. Canalization of freeze tolerance in an alpine grasshopper.

    PubMed

    Hawes, Timothy C

    2015-10-01

    In the Rock and Pillar Range, New Zealand, the alpine grasshopper, Sigaus australis Hutton, survives equilibrium freezing (EF) all-year round. A comparison of freeze tolerance (FT) in grasshoppers over four austral seasons for a 1 year period finds that: (a) the majority (>70%) of the sample population of grasshoppers survive single freeze-stress throughout the year; (b) exposure to increased freeze stress (multiple freeze-stress events) does not lead to a loss of freeze tolerance; and (c) responses to increased freeze stress reveal seasonal tuning of the FT adaptation to environmental temperatures. The Rock and Pillar sample population provides a clear example of the canalization of the FT adaptation. Seasonal variability in the extent of tolerance of multiple freezing events indicates that physiology is modulated to environmental temperatures by phenotypic plasticity - i.e. the FT adaptation is permanent and adjustable. PMID:26210007

  17. 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.

  18. 23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... OPERATIONS TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS-LENGTH, WIDTH AND WEIGHT LIMITATIONS § 658.23 LCV freeze... and pavement design characteristics of the alternate route should be equivalent to those of...

  19. 23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... OPERATIONS TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS-LENGTH, WIDTH AND WEIGHT LIMITATIONS § 658.23 LCV freeze... and pavement design characteristics of the alternate route should be equivalent to those of...

  20. 23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... OPERATIONS TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS-LENGTH, WIDTH AND WEIGHT LIMITATIONS § 658.23 LCV freeze... and pavement design characteristics of the alternate route should be equivalent to those of...

  1. The influence of freezing and freeze-drying of tissue specimens on enzyme activity.

    PubMed

    Meijer, A E; Benson, D; Scholte, H R

    1977-04-01

    In the presented study the influence of freezing and freeze-drying on enzyme activity is described. Attention is paid to 16 enzymes which can be used for quantitative enzyme histochemical techniques. With the exception of succinate dehydrogenase only, no significant inactivation during freezing and freeze-drying procedures could be demonstrated with lactate dehydrogenase, malate dehydrogenase (NAD+), malate dehydrogenase (decarboxylating) (NADP+), isocitrate dehydrogenase (NADP+), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADH-oxydoreductase, mitochondrial glycerol-3-phosphate dehydrogenase, cytochrome c oxidase, phosphoglucomutase, glucosephosphate isomerase, glucose-6-phosphatase, acid phosphatase, beta-glucuronidase and non specific aryl esterase. Therefore, the results supply a sound foundation for those quantitative enzyme histochemical techniques in which tissue specimens are frozen or frozen-dried before enzyme estimations are performed. PMID:870461

  2. Gradient Driven Fluctuations

    NASA Technical Reports Server (NTRS)

    Cannell, David

    2005-01-01

    We have worked with our collaborators at the University of Milan (Professor Marzio Giglio and his group-supported by ASI) to define the science required to measure gradient driven fluctuations in the microgravity environment. Such a study would provide an accurate test of the extent to which the theory of fluctuating hydrodynamics can be used to predict the properties of fluids maintained in a stressed, non-equilibrium state. As mentioned above, the results should also provide direct visual insight into the behavior of a variety of fluid systems containing gradients or interfaces, when placed in the microgravity environment. With support from the current grant, we have identified three key systems for detailed investigation. These three systems are: 1) A single-component fluid to be studied in the presence of a temperature gradient; 2) A mixture of two organic liquids to be studied both in the presence of a temperature gradient, which induces a steady-state concentration gradient, and with the temperature gradient removed, but while the concentration gradient is dying by means of diffusion; 3) Various pairs of liquids undergoing free diffusion, including a proteidbuffer solution and pairs of mixtures having different concentrations, to allow us to vary the differences in fluid properties in a controlled manner.

  3. High-presssure shift freezing. Part 2. Modeling of freezing times for a finite cylindrical model.

    PubMed

    Sanz, P D; Otero, L

    2000-01-01

    A comprehensive vision of the heat transfer process involved in high-pressure shift freezing (HPSF) is shown in comparison to the process at atmospheric pressure. In addition, a mathematical model to predict the freezing times is presented. This model takes into consideration the dependence of the thermophysical properties relating to temperature and pressure and the supercooling reached by liquid water at atmospheric pressure after adiabatic expansion in the HPSF process. Experimental and theoretical data appear to agree. PMID:11101332

  4. Aquaporin-mediated improvement of freeze tolerance of Saccharomyces cerevisiae is restricted to rapid freezing conditions.

    PubMed

    Tanghe, An; Van Dijck, Patrick; Colavizza, Didier; Thevelein, Johan M

    2004-06-01

    Previous observations that aquaporin overexpression increases the freeze tolerance of baker's yeast (Saccharomyces cerevisiae) without negatively affecting the growth or fermentation characteristics held promise for the development of commercial baker's yeast strains used in frozen dough applications. In this study we found that overexpression of the aquaporin-encoding genes AQY1-1 and AQY2-1 improves the freeze tolerance of industrial strain AT25, but only in small doughs under laboratory conditions and not in large doughs under industrial conditions. We found that the difference in the freezing rate is apparently responsible for the difference in the results. We tested six different cooling rates and found that at high cooling rates aquaporin overexpression significantly improved the survival of yeast cells, while at low cooling rates there was no significant effect. Differences in the cultivation conditions and in the thawing rate did not influence the freeze tolerance under the conditions tested. Survival after freezing is determined mainly by two factors, cellular dehydration and intracellular ice crystal formation, which depend in an inverse manner on the cooling velocity. In accordance with this so-called two-factor hypothesis of freezing injury, we suggest that water permeability is limiting, and therefore that aquaporin function is advantageous, only under rapid freezing conditions. If this hypothesis is correct, then aquaporin overexpression is not expected to affect the leavening capacity of yeast cells in large, industrial frozen doughs, which do not freeze rapidly. Our results imply that aquaporin-overexpressing strains have less potential for use in frozen doughs than originally thought. PMID:15184134

  5. Shadowgraph Study of Gradient Driven Fluctuations

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    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-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 gradient died on a time scale of seconds, leaving the Soret induced concentration gradient in place. Again, large-scale fluctuations were observed and died away slowly in amplitude as diffusion destroyed the initial concentration gradient.

  6. 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 gradient died on a time scale of seconds, leaving the Soret induced concentration gradient in place. Again, large-scale fluctuations were observed and died away slowly in amplitude as diffusion destroyed the initial concentration gradient.

  7. GOCE gravity gradient data for lithospheric modeling

    NASA Astrophysics Data System (ADS)

    Bouman, Johannes; Ebbing, Jörg; Meekes, Sjef; Abdul Fattah, Rader; Fuchs, Martin; Gradmann, Sofie; Haagmans, Roger; Lieb, Verena; Schmidt, Michael; Dettmering, Denise; Bosch, Wolfgang

    2015-03-01

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) is the European Space Agency's (ESA) satellite gravity mission to determine the Earth's mean gravity field. GOCE delivers gravity gradients, a new type of satellite data. We study how these data can improve modeling of the Earth's lithosphere. We discuss the use of the original GOCE gravity gradients versus the use of gravity gradients in grids at satellite altitude or close the Earth's surface and conclude that grids are easier to handle than the original data because one does not have to deal with very different error characteristics of the different gradients, given in a rotating frame at varying heights. The downward continuation to the surface enhances signal and better reflects the near-surface geology. But this does not outweigh the amplification of noise and omission errors, which is why we recommend using the field at mean satellite altitude for lithospheric modeling. The North-East Atlantic region is ideal to analyze the additional value of GOCE gravity gradients because it is a well-studied region in terms of regional geophysics. We calculated the gradient sensitivity for crustal depth slices using a 3D lithospheric model. This reveals that especially interfaces with large density contrasts have a distinct signal in the gravity gradients, but that they are quite insensitive to intra-crustal density sources, which can have quite a large effect on surface gravity data. We also show that the satellite gradients have a depth sensitivity well suited to study the upper mantle density structure, making them complementary to gravity and seismic tomography. In the underexplored Rub'al-Khali area the GOCE vertical gradient was used to invert for crustal thickness. The updated Moho model gives a good fit to four of the six gradients and independent depths from seismic stations. The Moho model was used to update the heat flow model and source rock maturity maps, which are generally consistent with known source rock maturity trends in the surrounding regions. GOCE gradients are therefore useful to map crustal thickness and deep regional structures for frontier areas. In combination with other data, heat flow can be modeled which is essential for basin maturity evaluation.

  8. 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.

  9. 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...

  10. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Freezing and packaging rooms. 58.620 Section 58.620 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall...

  11. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Freezing and packaging rooms. 58.620 Section 58.620 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall...

  12. 7 CFR 58.638 - Freezing the mix.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as... and further freezing....

  13. 7 CFR 58.638 - Freezing the mix.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as... and further freezing....

  14. 7 CFR 58.638 - Freezing the mix.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as... and further freezing....

  15. 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 ...

  16. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Freezing and packaging rooms. 58.620 Section 58.620 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall...

  17. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Freezing and packaging rooms. 58.620 Section 58.620 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall...

  18. 7 CFR 58.620 - Freezing and packaging rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Freezing and packaging rooms. 58.620 Section 58.620 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall...

  19. 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.

  20. Interspecific analysis of xylem freezing responses in Acer and Betula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Temperate woody plants have evolved two methods for coping with seasonal exposure to sub-zero temperatures. Supercooling is a freeze-avoidance strategy where cells are able to resist the freezing of intracellular water below sub-zero temperatures. Non-supercooling is a freeze-tolerance strategy wh...

  1. Laser textured surface gradients

    NASA Astrophysics Data System (ADS)

    Ta, Van Duong; Dunn, Andrew; Wasley, Thomas J.; Li, Ji; Kay, Robert W.; Stringer, Jonathan; Smith, Patrick J.; Esenturk, Emre; Connaughton, Colm; Shephard, Jonathan D.

    2016-05-01

    This work demonstrates a novel technique for fabricating surfaces with roughness and wettability gradients and their subsequent applications for chemical sensors. Surface roughness gradients on brass sheets are obtained directly by nanosecond laser texturing. When these structured surfaces are exposed to air, their wettability decreases with time (up to 20 days) achieving both spatial and temporal wettability gradients. The surfaces are responsive to organic solvents. Contact angles of a series of dilute isopropanol solutions decay exponentially with concentration. In particular, a fall of 132° in contact angle is observed on a surface gradient, one order of magnitude higher than the 14° observed for the unprocessed surface, when the isopropanol concentration increased from 0 to 15.6 wt%. As the wettability changes gradually over the surface, contact angle also changes correspondingly. This effect offers multi-sensitivity at different zones on the surface and is useful for accurate measurement of chemical concentration.

  2. Vertical Axis Wind Turbine

    Energy Science and Technology Software Center (ESTSC)

    2002-04-01

    Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). VAWT-SAL Vertical Axis Wind Turbine- Stochastic Aerodynamic Loads Ver 3.2 numerically simulates the stochastic (random0 aerodynamic loads of the Vertical-Axis Wind Turbine (VAWT) created by the atomspheric turbulence. The program takes into account the rotor geometry, operating conditions, and assumed turbulence properties.

  3. 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.

  4. Vertical axis wind turbine

    SciTech Connect

    Kato, Y.; Seki, K.; Shimizu, Y.

    1981-01-27

    Wind turbines are largely divided into vertical axis wind turbines and propeller (Horizontal axis) wind turbines. The present invention discloses a vertical axis high speed wind turbine provided with rotational speed control systems. This vertical axis wind turbine is formed by having blades of a proper airfoil fitted to respective supporting arms provided radially from a vertical rotating shaft by keeping the blade span-wise direction in parallel with the shaft and being provided with aerodynamic control elements operating manually or automatically to control the rotational speed of the turbine.

  5. Rupture of vertical soap films

    NASA Astrophysics Data System (ADS)

    Rio, Emmanuelle

    2014-11-01

    Soap films are ephemeral and fragile objects. They tend to thin under gravity, which gives rise to the fascinating variations of colors at their interfaces but leads systematically to rupture. Even a child can create, manipulate and admire soap films and bubbles. Nevertheless, the reason why it suddenly bursts remains a mystery although the soap chosen to stabilize the film as well as the humidity of the air seem very important. One difficulty to study the rupture of vertical soap films is to control the initial solution. To avoid this problem we choose to study the rupture during the generation of the film at a controlled velocity. We have built an experiment, in which we measure the maximum length of the film together with its lifetime. The generation of the film is due to the presence of a gradient of surface concentration of surfactants at the liquid/air interface. This leads to a Marangoni force directed toward the top of the film. The film is expected to burst only when its weight is not balanced anymore by this force. We will show that this leads to the surprising result that the thicker films have shorter lifetimes than the thinner ones. It is thus the ability of the interface to sustain a surface concentration gradient of surfactants which controls its stability.

  6. Vortex Formation in Vertically Stratified Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Stewart, Glen R.

    2013-10-01

    A central problem of planet formation is how to form large planetesimals in a turbulent protoplanetary disk. Recent work suggests that MRI turbulence would excite such large velocities that the planetesimals would collisionally fragment rather than grow. The structure of chondritic meteorites indicates a gentle nebular environment where chondrules are sorted by size and cemented together rapidly. Although it is well established that anticyclones can concentrate particles that are weakly coupled to the gas in protoplanetary disks, the conditions required for the formation and long-time stability of anticyclones in a vertically stratified disk are still highly uncertain. Fully three dimensional fluid dynamic simulations of protoplanetary disks are computationally expensive when one requires a computational domain that is large compared to the vertical scale height of the disk. An alternative simulation approach is to use potential temperature as the vertical coordinate so that the equations of motion resemble the shallow water equations (Dowling et al. 1998). We have therefore modified a multilayer shallow water simulation code to model the formation of vortices in a vertically stratified protoplanetary disk with a radial entropy gradient. Vertical stratification of the disk is modeled by using multiple layers, where each layer has a different constant value of the entropy. By forcing a slope in the interfaces between the layers, we impose a radial entropy gradient in the disk. Radiative heating and cooling causes vertical mass exchange between adjacent constant entropy layers according to a Newton cooling formula. We find that the formation of anticyclones is robust, and that these vortices actively excite density waves, which in turn, transport angular momentum through the disk. Our simulations therefore yield new insights on how the dusty dead zones of protoplanetary disks can transport angular momentum through the disk by purely hydrodynamic processes. Support from NASA’s Origins of Solar Systems program is gratefully acknowledged.

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

    PubMed

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

    1998-11-01

    In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to - 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared to those obtained by air-blast and liquid N(2). Samples from the surface and centre of the frozen muscle were histologically analysed using an indirect technique (isothermal-freeze fixation). Air-blast and cryogenic fluid freezing, having thermal gradients, showed non-uniform ice crystal distributions. High-pressure-assisted frozen samples, both at the surface and at the central zones, showed similar, small-sized ice crystals. This technique is particularly useful for freezing large pieces of food when uniform ice crystal sizes are required. PMID:22061149

  8. Cavitation and water fluxes driven by ice water potential in Juglans regia during freeze-thaw cycles.

    PubMed

    Charra-Vaskou, Katline; Badel, Eric; Charrier, Guillaume; Ponomarenko, Alexandre; Bonhomme, Marc; Foucat, Loïc; Mayr, Stefan; Améglio, Thierry

    2016-02-01

    Freeze-thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice-liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree-water relations. We investigated water fluxes induced by ice formation during freeze-thaw cycles in Juglans regia L. stems using four non-invasive and complementary approaches: a microdendrometer, magnetic resonance imaging, X-ray microtomography, and ultrasonic acoustic emissions analysis. When the temperature dropped, ice nucleation occurred, probably in the cambium or pith areas, inducing high water potential gradients within the stem. The water was therefore redistributed within the stem toward the ice front. We could thus observe dehydration of the bark's living cells leading to drastic shrinkage of this tissue, as well as high tension within wood conduits reaching the cavitation threshold in sap vessels. Ultrasonic emissions, which were strictly emitted only during freezing, indicated cavitation events (i.e. bubble formation) following ice formation in the xylem sap. However, embolism formation (i.e. bubble expansion) in stems was observed only on thawing via X-ray microtomography for the first time on the same sample. Ultrasonic emissions were detected during freezing and were not directly related to embolism formation. These results provide new insights into the complex process and dynamics of water movements and ice formation during freeze-thaw cycles in tree stems. PMID:26585223

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

    SciTech Connect

    Tanaka, Fumihiko; Murata, Satoshi; Habara, Kazuhiro; Amaratunga, K.S.P.

    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.

  10. Hibernation physiology, freezing adaptation and extreme freeze tolerance in a northern population of the wood frog.

    PubMed

    Costanzo, Jon P; do Amaral, M Clara F; Rosendale, Andrew J; Lee, Richard E

    2013-09-15

    We investigated hibernation physiology and freeze tolerance in a population of the wood frog, Rana sylvatica, indigenous to Interior Alaska, USA, near the northernmost limit of the species' range. Winter acclimatization responses included a 233% increase in the hepatic glycogen depot that was subsidized by fat body and skeletal muscle catabolism, and a rise in plasma osmolality that reflected accrual of urea (to 106±10 μmol ml(-1)) and an unidentified solute (to ~73 μmol ml(-1)). In contrast, frogs from a cool-temperate population (southern Ohio, USA) amassed much less glycogen, had a lower uremia (28±5 μmol ml(-1)) and apparently lacked the unidentified solute. Alaskan frogs survived freezing at temperatures as low as -16°C, some 10-13°C below those tolerated by southern conspecifics, and endured a 2-month bout of freezing at -4°C. The profound freeze tolerance is presumably due to their high levels of organic osmolytes and bound water, which limits ice formation. Adaptive responses to freezing (-2.5°C for 48 h) and subsequent thawing (4°C) included synthesis of the cryoprotectants urea and glucose, and dehydration of certain tissues. Alaskan frogs differed from Ohioan frogs in retaining a substantial reserve capacity for glucose synthesis, accumulating high levels of cryoprotectants in brain tissue, and remaining hyperglycemic long after thawing. The northern phenotype also incurred less stress during freezing/thawing, as indicated by limited cryohemolysis and lactate accumulation. Post-glacial colonization of high latitudes by R. sylvatica required a substantial increase in freeze tolerance that was at least partly achieved by enhancing their cryoprotectant system. PMID:23966588

  11. Biotechnological applications of plant freezing associated proteins.

    PubMed

    Breton, G; Danyluk, J; Ouellet, F; Sarhan, F

    2000-01-01

    Plants use a wide array of proteins to protect themselves against low temperature and freezing conditions. The identification of these freezing tolerance associated proteins and the elucidation of their cryoprotective functions will have important applications in several fields. Genes encoding structural proteins, osmolyte producing enzymes, oxidative stress scavenging enzymes, lipid desaturases and gene regulators have been used to produce transgenic plants. These studies have revealed the potential capacity of different genes to protect against temperature related stresses. In some cases, transgenic plants with significant cold tolerance have been produced. Furthermore, the biochemical characterization of the cold induced antifreeze proteins and dehydrins reveals many applications in the food and the medical industries. These proteins are being considered as food additives to improve the quality and shelf-life of frozen foods, as cryoprotective agents for organ and cell cryopreservation, and as chemical adjuvant in cancer cryosurgery. PMID:11193297

  12. Freeze-out, Hadronization and Statistical Model

    NASA Astrophysics Data System (ADS)

    Castorina, Paolo

    2016-01-01

    The comparison of the statistical hadronization model with experimental data and lattice QCD results is not always straightforward. Indeed, the interpretation of the ϕ meson production, of the proton to pion multiplicity ratio at LHC and the agreement of the freeze-out curve with the lattice critical line in the T — µB plane, require further analyses. Moreover the dynamics of the hadronization has to be compatible with: 1) the statitical behavior also observed in elementary high energy collisions; 2) a universal hadronization temperature for all high energy collisions; 3) the freeze-out criteria. In these lecture notes the SHM is recalled and some explanations of the puzzling aspects of its comparison with data are discussed.

  13. Freezing and melting water in lamellar structures.

    PubMed Central

    Gleeson, J T; Erramilli, S; Gruner, S M

    1994-01-01

    The manner in which ice forms in lamellar suspensions of dielaidoylphosphatidylethanolamine, dielaidoylphosphatidylcholine, and dioleoylphosphatidylcholine in water depends strongly on the water fraction. For weight fractions between 15 and 9%, the freezing and melting temperatures are significantly depressed below 0 degree C. The ice exhibits a continuous melting transition spanning as much as 20 degrees C. When the water weight fraction is below 9%, ice never forms at temperatures as low as -40 degrees C. We show that when water contained in a lamellar lipid suspension freezes, the ice is not found between the bilayers; it exists as pools of crystalline ice in equilibrium with the bound water associated with the polar lipid headgroups. We have used this effect, together with the known chemical potential of ice, to measure hydration forces between lipid bilayers. We find exponentially decaying hydration repulsion when the bilayers are less than about 7 A apart. For larger separations, we find significant deviations from single exponential decay. PMID:7948683

  14. [Non-freezing cold injury in soldiers].

    PubMed

    Melamed, E; Glassberg, E

    2002-12-01

    Non-freezing cold injury (NFCI) is an injury of the hands or feet resulting from exposure to wet conditions and temperatures just above freezing, typically found in soldiers. NFCI is due to microvascular endothelial damage, stasis and vascular occlusion. At first, the tissue is cold and anesthetic, progressing to hyperemia in 24-48 hours. Hyperemia is accompanied by an intense painful burning sensation as well as blisters, redness, and possibly, ulcerations. NFCI management raises frustration in both medical officers and commanders. Most authorities are not aware of or remain unimpressed with the severity of NFCI, nor do they realize that it produces lifelong symptomatology. The following review of the available literature attempts to clear up some issues regarding the definition, pathogenesis, symptoms and preventative measures available in NFCI, including our own experience. PMID:12534203

  15. Ground freezing for containment of hazardous waste

    SciTech Connect

    Sayles, F.N.; Iskandar, I.K.

    1998-07-01

    The freezing of ground for the containment of subsurface hazardous waste is a promising method that is environmentally friendly and offers a safe alternative to other methods of waste retention in many cases. The frozen soil method offers two concepts for retaining waste. One concept is to freeze the entire waste area into a solid block of frozen soil thus locking the waste in situ. For small areas where the contaminated soil does not include vessels that would rupture from frost action, this concept may be simpler to install. A second concept, of course, is to create a frozen soil barrier to confine the waste within prescribed unfrozen soil boundaries; initial research in this area was funded by EPA, Cincinnati, OH, and the Army Corps of Engineers. The paper discusses advantages and limitations, a case study from Oak Ridge, TN, and a mesh generation program that simulates the cryogenic technology.

  16. Fast Melting and Freezing for Microgravity Experiments

    NASA Technical Reports Server (NTRS)

    Poorman, Richard M.

    1987-01-01

    Commercial tube welders adapted to metallurgical research. Proposed furnace melts and resolidifies small metal samples during brief periods. In furnace, sample surrounded by large heat sinks and rapidly heated near midlength by intense source of heat. Furnace intended for use in experiments in microgravity: entire melting-and-freezing process requires less than 20 s of near weightlessness experienced in parabolic climb and dive of KC-135 airplane.

  17. Vogel-Fulcher freezing in relaxor ferroelectrics

    SciTech Connect

    Pirc, R.; Blinc, R.

    2007-07-01

    A physical mechanism for the freezing of polar nanoregions (PNRs) in relaxor ferroelectrics is presented. Assuming that the activation energy for the reorientation of a cluster of PNRs scales with the mean volume of the cluster, the characteristic relaxation time {tau} is found to diverge as the cluster volume reaches the percolation limit. Applying the mean field theory of continuum percolation, the familiar Vogel-Fulcher equation for the temperature dependence of {tau} is derived.

  18. Freeze tolerance in an arctic Alaska stonefly.

    PubMed

    Walters, Kent R; Sformo, Todd; Barnes, Brian M; Duman, John G

    2009-01-01

    Most aquatic insects do not survive subzero temperatures and, for those that do, the physiology has not been well characterized. Nemoura arctica is a species of stonefly widely distributed throughout arctic and subarctic Alaska. We collected nymphs from the headwaters of the Chandalar River, where we recorded streambed temperatures as low as -12.7 degrees C in midwinter. When in contact with ice, autumn-collected N. arctica cool to -1.5+/-0.4 degrees C before freezing, but individuals survived temperatures as low as -15 degrees C, making this the first described species of freeze-tolerant stonefly. N. arctica clearly survive freezing in nature, as winter-collected nymphs encased in ice demonstrated high survivorship when thawed. In the laboratory, 87% of N. arctica nymphs frozen to -15 degrees C for 2.5 weeks survived and, within one month of thawing, 95% of the last-instar nymphs emerged. N. arctica produce both glycerol and ice-binding factors (e.g. antifreeze protein) in response to low temperature. Hemolymph glycerol concentrations increased from 3 mmol l(-1) to 930+/-114 mmol l(-1) when temperatures were decreased from 4 degrees C to -8 degrees C, and N. arctica continued to produce glycerol even while frozen. Although the hemolymph of individual cold-acclimated nymphs occasionally exhibited more than a degree of thermal hysteresis, typically the hemolymph exhibited only hexagonal crystal growth, indicating a low concentration of ice-binding factor. Hemolymph of nymphs acclimated to subzero temperatures had recrystallization inhibition. These results demonstrate that, in the face of freezing conditions, N. arctica exhibit overwintering adaptations similar to those of terrestrial insects. PMID:19112150

  19. Vertical axis windmill

    SciTech Connect

    Campbell, J.S.

    1980-04-08

    A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.

  20. 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.

  1. Human freezing in response to affective films.

    PubMed

    Hagenaars, Muriel A; Roelofs, Karin; Stins, John F

    2014-01-01

    Human freezing has been objectively assessed using a passive picture viewing paradigm as an analog for threat. These results should be replicated for other stimuli in order to determine their stability and generalizability. Affective films are used frequently to elicit affective responses, but it is unknown whether they also elicit freezing-like defense responses. To test whether this is the case, 50 participants watched neutral, pleasant and unpleasant film fragments while standing on a stabilometric platform and wearing a polar band to assess heart rate. Freezing-like responses (indicated by overall reduced body sway and heart rate deceleration) were observed for the unpleasant film only. The unpleasant film also elicited early reduced body sway (1-2 s after stimulus onset). Heart rate and body sway were correlated during the unpleasant film only. The results suggest that ecologically valid stimuli like films are adequate stimuli in evoking defense responses. The results also underscore the importance of including time courses in human experimental research on defense reactions in order to delineate different stages in the defense response. PMID:23805855

  2. Steam consumption reduction by eutectic freeze crystallization

    SciTech Connect

    Bichsel, S.E.; Cleary, M.; Barron, T.S.; Heist, J.A.

    1985-01-01

    Steam production in American beet sugar factories can be reduced by 600 pounds per ton of beets by using hydrate freeze crystallization in place of pan evaporators for sugar crystallization. This is a relatively constant number, regardless of current factory energy use. Further reduction is limited by the juice heating needs in the purification operations. Steam for juice heating is 20 to 30% on beets, or 400 to 600 pounds of steam per ton. In efficient factories this is about the steam flow to the evaporators when the pan crystallizers are replaced by freeze crystallization. An approach is described here for a rapid evaluation of effects on the steam balance of basic process changes. It provides a visual guide to restructuring the steam balance that simplifies optimization when such changes are made. The graphic approach is useful in illustrating methods of reducing energy use in a sugar factory, in addition to the current analysis of integration of the hydrate freeze process. For example, membrane and vapor recompression evaporators for juice concentration must be accompanied by major factory modifications to produce any net savings of steam. The reason is the needs for specific steam quantity and quality for the pan evaporators and juice heaters, supplied through the current evaporator trains. Reduction of the steam rate below 25 to 35% on beets will require changes to the conventional juice purification process.

  3. Radioluminescence and scintillation results of horizontal gradient freeze grown aliovalently-doped CeBr3.

    SciTech Connect

    Linnick, C.; Harrison, Mark J.; Doty, F. Patrick; McGregor, D. S.; McCreary, M.; Brinton, S.; Montag, B.

    2008-11-01

    Strengthening the crystal lattice of lanthanide halides, which are brittle, anisotropic, ionic crystals, may prove to increase the availability and ruggedness of these scintillators for room-temperature gamma-ray spectroscopy applications. Eight aliovalent dopants for CeBr{sub 3} were explored in an effort to find the optimal aliovalent strengthening agent. Eight dopants, CaBr{sub 2}, SrBr{sub 2}, BaBr{sub 2}, ZrBr{sub 4}, HfBr{sub 4}, ZnBr{sub 2}, CdBr[sub 2}, and PbBr{sub 2}, were explored at two levels of doping, 500 and 1000 ppm. From each ingot, samples were harvested for radioluminescence spectrum measurement and scintillation testing. Of the eight dopants explored, only BaBr{sub 2} and PbBr{sub 2} were found to clearly decrease total light yield. ZnBr{sub 2} and CdBr{sub 2} dopants both affected the radioluminescence emission spectrum very little as compared to undoped CeBr{sub 3}. HfBr{sub 2}- and ZnBr{sub 4}-doped CeBr{sub 3} exhibited the highest light yields.

  4. Subsurface temperatures and geothermal gradients on the North Slope, Alaska

    USGS Publications Warehouse

    Collett, Timothy S.; Bird, Kenneth J.; Magoon, Leslie B.

    1989-01-01

    Geothermal gradients as interpreted from a series of high-resolution stabilized well-bore-temperature surveys from 46 North Slope, Alaska, wells vary laterally and vertically throughout the near-surface sediment (0-2,000 m). The data from these surveys have been used in conjunction with depths of ice-bearing permafrost, as interpreted from 102 well logs, to project geothermal gradients within and below the ice-bearing permafrost sequence. The geothermal gradients calculated from the projected temperature profiles are similar to the geothermal gradients measured in the temperature surveys. Measured and projected geothermal gradients in the ice-bearing permafrost sequence range from 1.5??C/100m in the Prudhoe Bay area to 5.1??C/100m in the National Petroleum Reserve in Alaska (NPRA).

  5. Response of New zealand mudsnails Potamopyrgus antipodarum to freezing and near freezing fluctuating water temperatures

    USGS Publications Warehouse

    Moffitt, Christine M.; James, Christopher A.

    2012-01-01

    We explored the resilience of the invasive New Zealand mudsnail Potamopyrgus antipodarum to fluctuating winter freezing and near-freezing temperature cycles in laboratory tests. Our goal was to provide data to confirm field observations of mortality and presumed mortality in stream habitats with fluctuating freezing to near-freezing temperatures. We tested individuals from 2 locations with distinctly different thermal regimes and population densities. One location had low snail densities and water temperatures with strong diel and seasonal water variation. The other location had high snail densities and nearly constant water temperatures. Groups of individuals from both locations were tested in each of 3 laboratory-created diel thermal cycles around nominal temperatures of 0, 2, or 4°C. Mortality occurred in cycles around 0°C in both populations, and little to no mortality occurred at temperatures >0°C. Individuals from both sources held in diel 0°C cycles for 72 h showed 100% mortality. Our findings support observations from published field studies that survival was limited in infested habitats subject to freezing temperatures.

  6. Aquaporin expression correlates with freeze tolerance in baker's yeast, and overexpression improves freeze tolerance in industrial strains.

    PubMed

    Tanghe, An; Van Dijck, Patrick; Dumortier, Françoise; Teunissen, Aloys; Hohmann, Stefan; Thevelein, Johan M

    2002-12-01

    Little information is available about the precise mechanisms and determinants of freeze resistance in baker's yeast, Saccharomyces cerevisiae. Genomewide gene expression analysis and Northern analysis of different freeze-resistant and freeze-sensitive strains have now revealed a correlation between freeze resistance and the aquaporin genes AQY1 and AQY2. Deletion of these genes in a laboratory strain rendered yeast cells more sensitive to freezing, while overexpression of the respective genes, as well as heterologous expression of the human aquaporin gene hAQP1, improved freeze tolerance. These findings support a role for plasma membrane water transport activity in determination of freeze tolerance in yeast. This appears to be the first clear physiological function identified for microbial aquaporins. We suggest that a rapid, osmotically driven efflux of water during the freezing process reduces intracellular ice crystal formation and resulting cell damage. Aquaporin overexpression also improved maintenance of the viability of industrial yeast strains, both in cell suspensions and in small doughs stored frozen or submitted to freeze-thaw cycles. Furthermore, an aquaporin overexpression transformant could be selected based on its improved freeze-thaw resistance without the need for a selectable marker gene. Since aquaporin overexpression does not seem to affect the growth and fermentation characteristics of yeast, these results open new perspectives for the successful development of freeze-resistant baker's yeast strains for use in frozen dough applications. PMID:12450819

  7. The role of Langmuir circulation in suspension freezing

    NASA Astrophysics Data System (ADS)

    Kempema, Edward W.; Dethleff, Dirk

    In November 2004 we used an acoustic Doppler velocimeter (ADV) to measure the three components of velocity in Langmuir circulation (LC) cells when frazil was forming in a lake. LC circulation was indicated by windrows of slush ice on the water surface. We also collected samples of lake water, ice interstitial water and ice to determine their sediment concentrations. The ADV record showed rotating currents in the cross-wind/vertical plane indicative of LC. Downward-directed velocities were large enough to entrain frazil into the water column for 27% of the 97 min observation time at the ADV location. Sediment concentrations in the ice and interstitial water samples were greater than concentrations in water-column samples collected in upwelling zones of LC cells. We conclude that suspension freezing was forming particle-laden ice as frazil trapped below LC convergence zones grew in downwelled, supercooled water. The rotating roll vortices of Langmuir circulation play an important role in forming sediment-laden ice.

  8. 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.

  9. 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.

  10. Gradient tabu search.

    PubMed

    Stepanenko, Svetlana; Engels, Bernd

    2007-01-30

    This paper presents a modification of the tabu search called gradient tabu search (GTS). It uses analytical gradients for a fast minimization to the next local minimum and analytical diagonal elements of the Hessian to escape local minima. For an efficient blocking of already visited areas tabu regions and tabu directions are introduced into the tabu list (TL). Trials with various well-known test functions indicate that the GTS is a very promising approach to determine local and global minima of differentiable functions. Possible application areas could be optimization routines for force field parameters or conformational searches for large molecules. PMID:17186482

  11. High gradient electron guns

    SciTech Connect

    Fant, K.S.; Caryotakis, G.; Koontz, R.F.; Vlieks, A.E. ); Miram, G. , Atherton, CA )

    1990-08-01

    Experiments have been conducted to determine peak operating gradients attainable in thermionic electron guns. These tests are part of a study of high-current-density, long-life cathodes suitable for use in high power klystrons. We also investigated the use of chromium oxide coating as a means of inhibiting electronic breakdown across the focus electrode anode gap. Field gradients in excess of 280 kV/cm have been achieved for a gun operating at 240 kV with a beam current of 228 A, at pulse widths of the order of 1 {mu}s. 3 refs., 5 figs.

  12. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, Norman L.

    1986-01-01

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  13. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, N.L.

    1983-11-10

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  14. Freeze-Thaw Injury to Isolated Spinach Protoplasts and Its Simulation at Above Freezing Temperatures 1

    PubMed Central

    Wiest, Steven C.; Steponkus, Peter L.

    1978-01-01

    Possibilities to account for the mechanism of freeze-thaw injury to isolated protoplasts of Spinacia oleracea L. cv. Winter Bloomsdale were investigated. A freeze-thaw cycle to ?3.9 C resulted in 80% lysis of the protoplasts. At ?3.9 C, protoplasts are exposed to the equivalent of a 2.1 osmolal solution. Isolated protoplasts behave as ideal osmometers in the range of concentrations tested (0.35 to 2.75 osmolal), arguing against a minimum critical volume as a mechanism of injury. Average protoplast volume after a freeze-thaw cycle was not greatly different than the volume before freezing, arguing against an irreversible influx of solutes while frozen. A wide variety of sugars and sugar alcohols, none of which was freely permeant, were capable of protecting against injury which occurred when protoplasts were frozen in salt solutions. The extent of injury was also dependent upon the type of monovalent ions present, with Li = Na > K = Rb = Cs and Cl ? Br > I, in order of decreasing protoplast survival. Osmotic conditions encountered during a freeze-thaw cycle were established at room temperature by exposing protoplasts to high salt concentrations and then diluting the osmoticum. Injury occurred only after dilution of the osmoticum and was correlated with the expansion of the plasma membrane. Injury observed in frozen-thawed protoplasts was correlated with the increase in surface area the plasma membrane should have undergone during thawing, supporting the contention that contraction of the plasma membrane during freezing and its expansion during thawing are two interacting lesions which cause protoplast lysis during a freezethaw cycle. PMID:16660588

  15. Freeze-thaw Laboratory Column Experiments using Arctic Permafrost Cores: Exploring Controls of Subsurface Heterogeneity on Greenhouse Gas Release

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Kneafsey, T. J.; Nakagawa, S.; Borglin, S. E.; Cook, P.; Tas, N.; Torn, M. S.; Jansson, J.; Hubbard, S. S.

    2013-12-01

    Although warming induced permafrost thaw and greenhouse gas release to the atmosphere is considered to be one of the largest possible ecosystem feedbacks to climate change in the Arctic, there are significant uncertainties associated with subsurface hydrological, geochemical and microbial controls over the magnitude and rate of the greenhouse gas release. Gaining an understanding of the controls of typically heterogeneous subsurface properties on greenhouse gas release is exacerbated by the difficulty in sufficiently quantifying subsurface dynamics and gas exchange in-situ and in response to freeze-thaw perturbations. As a part of the DOE's Next Generation Ecosystem Experiments (NGEE) in the Arctic, we are performing a series of controlled laboratory freeze-thaw experiments to study CO2, CH4, and N2O gas release in vertical permafrost columns as a function of dynamic and vertically heterogeneous hydrological, geochemical and microbial properties. The column studies are being performed using representative ~ 0.75 m cores collected at the NGEE Barrow, AK site from the ground surface into the permafrost. The experimental apparatus was designed to simulate the seasonal freeze-thaw of the Barrow active layer. The column is equipped with several types of sensors and sampling devices, including thermistors, geophysical (seismic and electrical) sensors, and ports that allow sampling for solids, fluids, and gasses. Our preliminary tests simulated seasonal temperature variation from ~ -20°C to +5°C. Our results demonstrated the success of the freeze-thaw control of the experimental apparatus and the capability of the geophysical methods to monitor the freeze-thaw spatiotemporal dynamics. Samples collected during the experiment also revealed the changes of the hydrological and biogeochemical conditions of the column and its linkage to carbon degradation and release in a vertical permafrost soil column. While our initial experiments were conducted to simulate the seasonal freeze thaw of a fairly homogeneous active layer under current climate conditions, subsequent experiments will be designed to (a) investigate thaw of deeper permafrost and associated hydrological, geochemical and microbiological processes, including greenhouse gas release; (b) quantify the effect of vertical subsurface heterogeneity on the integrated above-ground greenhouse gas response.

  16. Tunable high-gradient permanent magnet quadrupoles

    NASA Astrophysics Data System (ADS)

    Shepherd, B. J. A.; Clarke, J. A.; Marks, N.; Collomb, N. A.; Stokes, D. G.; Modena, M.; Struik, M.; Bartalesi, A.

    2014-11-01

    A novel type of highly tunable permanent magnet (PM) based quadrupole has been designed by the ZEPTO collaboration. A prototype of the design (ZEPTO-Q1), intended to match the specification for the CLIC Drive Beam Decelerator, was built and magnetically measured at Daresbury Laboratory and CERN. The prototype utilises two pairs of PMs which move in opposite directions along a single vertical axis to produce a quadrupole gradient variable between 15 and 60 T/m. The prototype meets CLIC's challenging specification in terms of the strength and tunability of the magnet.

  17. Numerical simulation of the interaction of biological cells with an ice front during freezing

    NASA Astrophysics Data System (ADS)

    Carin, M.; Jaeger, M.

    2001-12-01

    The goal of this study is a better understanding of the interaction between cells and a solidification front during a cryopreservation process. This technique of freezing is commonly used to conserve biological material for long periods at low temperatures. However the biophysical mechanisms of cell injuries during freezing are difficult to understand because a cell is a very sophisticated microstructure interacting with its environment. We have developed a finite element model to simulate the response of cells to an advancing solidification front. A special front-tracking technique is used to compute the motion of the cell membrane and the ice front during freezing. The model solves the conductive heat transfer equation and the diffusion equation of a solute on a domain containing three phases: one or more cells, the extra-cellular solution and the growing ice. This solid phase growing from a binary salt solution rejects the solute in the liquid phase and increases the solute gradient around the cell. This induces the shrinkage of the cell. The model is used to simulate the engulfment of one cell modelling a red blood cell by an advancing solidification front initially planar or not is computed. We compare the incorporation of a cell with that of a solid particle.

  18. Structural effects caused by spray- and freeze-drying of liposomes and bilayer disks.

    PubMed

    Wessman, Per; Edwards, Katarina; Mahlin, Denny

    2010-04-01

    Cryo-TEM and dynamic light scattering was used to investigate morphological changes induced by spray- and freeze-drying of liposomes and nanosized bilayer disks composed of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-5000] (DSPE-PEG) from lactose solution. Particular focus was put on the identification of structural alterations that risk influencing the performance of liposomes and bilayer disks as carriers for protein and peptide drugs. Significant changes in the lipid aggregate structure and/or size was noted upon dehydration. Uni-lamellar liposomes tended to shrink in size and become bi-lamellar as a consequence of the drying process. The same transformation was observed upon deliberate establishment of a lactose gradient over the membranes of liposomes in solution. A mechanism based on an osmotically driven invagination of the liposomes is proposed to explain the change from uni- to bi-lamellar structures. PEGylation promoted formation of larger liposomes during spray-drying, and had a similar, but less pronounced, effect also during freeze-drying. The observed structural changes may have important consequences for the bioavailability of protein/peptide drugs bound to, or embedded in, the liposome membranes. The radius of bilayer disks increased upon both spray- and freeze-drying, but the drying procedure did not change the open single-bilayer structure of the disks. PMID:19894278

  19. 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)

  20. Manipulating the Gradient

    ERIC Educational Resources Information Center

    Gaze, Eric C.

    2005-01-01

    We introduce a cooperative learning, group lab for a Calculus III course to facilitate comprehension of the gradient vector and directional derivative concepts. The lab is a hands-on experience allowing students to manipulate a tangent plane and empirically measure the effect of partial derivatives on the direction of optimal ascent. (Contains 7…

  1. Micromachined electrostatic vertical actuator

    SciTech Connect

    Lee, A.P.; Sommargren, G.E.; McConaghy, C.F.; Krulevitch, P.A.

    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.

  2. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    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.

  3. Influence of vertical flows in wells on groundwater sampling

    NASA Astrophysics Data System (ADS)

    McMillan, Lindsay A.; Rivett, Michael O.; Tellam, John H.; Dumble, Peter; Sharp, Helen

    2014-11-01

    Pumped groundwater sampling evaluations often assume that horizontal head gradients predominate and the sample comprises an average of water quality variation over the well screen interval weighted towards contributing zones of higher hydraulic conductivity (a permeability-weighted sample). However, the pumping rate used during sampling may not always be sufficient to overcome vertical flows in wells driven by ambient vertical head gradients. Such flows are reported in wells with screens between 3 and 10 m in length where lower pumping rates are more likely to be used during sampling. Here, numerical flow and particle transport modeling is used to provide insight into the origin of samples under ambient vertical head gradients and under a range of pumping rates. When vertical gradients are present, sample provenance is sensitive to pump intake position, pumping rate and pumping duration. The sample may not be drawn from the whole screen interval even with extended pumping times. Sample bias is present even when the ambient vertical flow in the wellbore is less than the pumping rate. Knowledge of the maximum ambient vertical flow in the well does, however, allow estimation of the pumping rate that will yield a permeability-weighted sample. This rate may be much greater than that recommended for low-flow sampling. In practice at monitored sites, the sampling bias introduced by ambient vertical flows in wells may often be unrecognized or underestimated when drawing conclusions from sampling results. It follows that care should be taken in the interpretation of sampling data if supporting flow investigations have not been undertaken.

  4. How to freeze drop oscillations with powders

    NASA Astrophysics Data System (ADS)

    Marston, Jeremy; Zhu, Ying; Vakarelski, Ivan; Thoroddsen, Sigurdur

    2012-11-01

    We present experiments that show when a water drop impacts onto a bed of fine, hydrophobic powder, the final form of the drop can be very different from the spherical form with which it impacts. For all drop impact speeds, the drop rebounds due to the hydrophobic nature of the powder. However, we observe that above a critical impact speed, the drop undergoes a permanent deformation to a highly non-spherical shape with a complete coverage of powder, thus creating a deformed liquid marble. This powder coating acts to freeze the drop oscillations during rebound.

  5. Freeze Tolerant Radiator for an Advanced EMU

    NASA Technical Reports Server (NTRS)

    Copeland, Robert J.; Elliott, Jeannine; Weislogel, Mark

    2004-01-01

    During an Extravehicular Activity (EVA), the astronaut s metabolic heat and the heat produced by the Portable Life Support Unit (PLSS) must be rejected. This heat load is currently rejected by a sublimator, which vents up to eight pounds of water each EVA. However, for advanced space missions of the future, water venting to space needs to be minimized because resupply impacts from earth will be prohibitive. If this heat load could be radiated to space from the PLSS, which has enough surface area to radiate most of the heat, the amount of water now vented could be greatly reduced. Unfortunately, a radiator rejects heat at a relatively constant rate, but the astronauts generate a variable heat load depending on how hard they are working. Without a way to vary the heat removal rate, the astronaut would experience cold discomfort or even frostbite. A proven method allowing a radiator to be turned-down is to sequentially allow tubes that carry the heat transfer fluid to the radiator to freeze. A drawback of current freezable radiators using this method is that they are far to heavy for use on a PLSS, because they use heavy construction to prevent the tubes from bursting as they freeze and thaw. This creates the need for a large radiator to reject most of the heat but with a lightweight tube that doesn t burst as it freezes and thaws. The new freezable radiator for the Extravehicular Mobility Unit (EMU) has features to accommodate the expansion of the radiator fluid when it freezes, and still have the high tube to fin conductance needed to minimize the number and weight of the tubes. Radiator fluid candidates are water and a propylene glycol-water mixture. This design maintains all materials within their elastic limits so that large volume changes can be achieved without breaking the tube. This concept couples this elastic expansion with an extremely lightweight, extremely high conductivity carbon fiber fin that can carry the heat needed to thaw a frozen tube. By using most of the exposed surface area of the PLSS as a radiator, the system can reject about 75% of the highest heat load, and reduce the loss of water through sublimation by a factor of four. The proposed radiator and a small water tank can be no heavier than the current system.

  6. Freezing distributed entanglement in spin chains

    SciTech Connect

    D'Amico, Irene; Lovett, Brendon W.; Spiller, Timothy P.

    2007-09-15

    We show how to freeze distributed entanglement that has been created from the natural dynamics of spin chain systems. The technique that we propose simply requires single-qubit operations and isolates the entanglement in specific qubits at the ends of branches. Such frozen entanglement provides a useful resource, for example for teleportation or distributed quantum processing. The scheme can be applied to a wide range of systems--including actual spin systems and alternative qubit embodiments in strings of quantum dots, molecules, or atoms.

  7. Freeze-drying of live virus vaccines: A review.

    PubMed

    Hansen, L J J; Daoussi, R; Vervaet, C; Remon, J-P; De Beer, T R M

    2015-10-13

    Freeze-drying is the preferred method for stabilizing live, attenuated virus vaccines. After decades of research on several aspects of the process like the stabilization and destabilization mechanisms of the live, attenuated viruses during freeze-drying, the optimal formulation components and process settings are still matter of research. The molecular complexity of live, attenuated viruses, the multiple destabilization pathways and the lack of analytical techniques allowing the measurement of physicochemical changes in the antigen's structure during and after freeze-drying mean that they form a particular lyophilization challenge. The purpose of this review is to overview the available information on the development of the freeze-drying process of live, attenuated virus vaccines, herewith focusing on the freezing and drying stresses the viruses can undergo during processing as well as on the mechanisms and strategies (formulation and process) that are used to stabilize them during freeze-drying. PMID:26364685

  8. Two-dimensional freezing criteria for crystallizing colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Wang, Ziren; Alsayed, Ahmed M.; Yodh, Arjun G.; Han, Yilong

    2010-04-01

    Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen-Verlet freezing rule, the Löwen-Palberg-Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing.

  9. Two-dimensional freezing criteria for crystallizing colloidal monolayers

    SciTech Connect

    Wang Ziren; Han Yilong; Alsayed, Ahmed M.

    2010-04-21

    Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen-Verlet freezing rule, the Loewen-Palberg-Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing.

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

    SciTech Connect

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

    2015-05-15

    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{sub //}, 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.

  11. High-pressure freezing and freeze substitution of Arabidopsis for electron microscopy.

    PubMed

    Austin, Jotham R

    2014-01-01

    The objectives of electron microscopy ultrastructural studies are to examine cellular architecture and relate the cell's structural machinery to dynamic functional roles. This aspiration is difficult to achieve if specimens have not been adequately preserved in a "living state"; hence specimen preparation is of the utmost importance for the success of any electron micrographic study. High-pressure freezing (HPF)/freeze substitution (FS) has long been recognized as the primer technique for the preservation of ultrastructure in biological samples. In most cases a basic HPF/freeze substitution protocol is sufficient to obtain superior ultrastructural preservation and structural contrast, which allows one to use more advanced microscopy techniques such as 3D electron tomography. However, for plant tissues, which have a thick cell wall, large water-filled vacuoles, and air spaces (all of which are detrimental to cryopreservation), these basic HPF/FS protocols often yield undesirable results. In particular, ice crystal artifacts and the staining of membrane systems are often poorly or negatively stained, which make 3D segmentation of a tomogram difficult. To overcome these problems, various aspects of the HPF/FS protocol can be altered, including the cryo-filler(s) used, freeze substitution cocktail, and the resin infiltration process. This chapter will describe these modifications for the preparation of plant tissues for routine electron microscopic studies, immunocytochemistry, and 3D tomographic electron imaging. PMID:24057382

  12. Integrated gravity and gravity gradient 3D inversion using the non-linear conjugate gradient

    NASA Astrophysics Data System (ADS)

    Qin, Pengbo; Huang, Danian; Yuan, Yuan; Geng, Meixia; Liu, Jie

    2016-03-01

    Gravity data, which are critical in mineral, oil, and gas exploration, are obtained from the vertical component of the gravity field, while gravity gradient data are measured from changes in the gravity field in three directions. However, few studies have sought to improve exploration techniques by integrating gravity and gravity gradient data using inversion methods. In this study, we developed a new method to integrate gravity and gravity gradient data in a 3D density inversion using the non-linear conjugate gradient (NLCG) method and the minimum gradient support (MGS) functional to regularize the 3D inverse problem and to obtain a clear and accurate image of the anomalous body. The NLCG algorithm, which is suitable for solving large-scale nonlinear optimization problems and requires no memory storage, was compared to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton algorithm and the results indicated that the convergence rate of NLCG is slower, but that the storage requirement and computation time is lower. To counteract the decay in kernel function, we introduced a depth weighting function for anomalous bodies at the same depth, with information about anomalous body depth obtained from well log and seismic exploration data. For anomalous bodies at different depths, we introduced a spatial gradient weighting function to incorporate additional information obtained in the inversion. We concluded that the spatial gradient weighting function enhanced the spatial resolution of the recovered model. Furthermore, our results showed that including multiple components for inversion increased the resolution of the recovered model. We validated our model by applying our inversion method to survey data from Vinton salt dome, Louisiana, USA. The results showed good agreement with known geologic information; thus confirming the accuracy of this approach.

  13. Retarded condensate freezing propagation on superhydrophobic surfaces patterned with micropillars

    NASA Astrophysics Data System (ADS)

    Zhao, Yugang; Yang, Chun

    2016-02-01

    Previous studies have shown ice delay on nano-structured or hierarchical surfaces with nanoscale roughness. Here we report retarded condensate freezing on superhydrophobic silicon substrates fabricated with patterned micropillars of small aspect ratio. We further investigated the pillar size effects on freezing propagation. We found that the velocity of freezing propagation on the surface patterned with proper micropillars can be reduced by one order of magnitude, compared to that on the smooth untreated silicon surface. Additionally, we developed an analytical model to describe the condensate freezing propagation on a structured surface with micropillars and the model predictions were compared with our experimental results.

  14. Reversible Photoinhibition in Antarctic Moss during Freezing and Thawing.

    PubMed

    Lovelock, C. E.; Jackson, A. E.; Melick, D. R.; Seppelt, R. D.

    1995-11-01

    Tolerance of antarctic moss to freezing and thawing stress was investigated using chlorophyll a fluorescence. Freezing in darkness caused reductions in Fv/Fm (ratio of variable to maximum fluorescence) and Fo (initial fluorescence) that were reversible upon thawing. Reductions in Fv/Fm and Fo during freezing in darkness indicate a reduction in the potential efficiency of photosystem II that may be due to conformational changes in pigment-protein complexes due to desiccation associated with freezing. The absorption of light during freezing further reduced Fv/Fm and Fo but was also reversible. Using dithiothreitol (DTT), which inhibits the formation of the carotenoid zeaxanthin, we found reduced flurorescence quenching during freezing and reduced concentrations of zeaxanthin and antheraxanthin after freezing in DTT-treated moss. Reduced concentrations of zeaxanthin and antheraxanthin in DTT-treated moss were partially associated with reductions in nonphotochemical fluorescence quenching. The reversible photoinhibition observed in antarctic moss during freezing indicates the existence of processes that protect from photoinhibitory damage in environments where freezing temperatures occur in conjunction with high solar radiation levels. These processes may limit the need for repair cycles that require temperatures favorable for enzyme activity. PMID:12228644

  15. 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.

  16. 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.

  17. Freezing efficiency of Silver Iodide, ATD and Kaolinite in the contact freezing mode

    NASA Astrophysics Data System (ADS)

    Nagare, Baban; Marcolli, Claudia; Stetzer, Olaf; Lohmann, Ulrike

    2014-05-01

    The importance of heterogeneous ice nucleation via contact freezing is one of the open questions in the atmospheric science community. In our laboratory, we built the Collision Nucleation CHamber (CLINCH) (Ladino et al. 2011) in which falling cloud droplets can collide with aerosol particles. In this study, contact freezing experiments are conducted to investigate the ice nucleation ability of silver iodide (AgI), kaolinite and Arizona Test Dust (ATD). Silver iodide has been known for its ice nucleation ability since 1940s (Vonnegut 1947) while kaolinite is a clay mineral and known to be a moderate ice nucleus. ATD is a commercial dust sample used by many groups to compare different setups. In CLINCH, size selected aerosol particles collide with water droplets of 80 m diameter. With the extension in chamber length it is possible to vary the interaction time of ice nuclei and the droplets. Our experiments are performed between -10 to -36 C for various concentrations of ice nuclei and different interaction times. The frozen fraction of the droplets is determined using the custom-made depolarization detector IODE (Nicolet et al., 2010). Depolarization of linearly polarized incident laser light is used to determine the ratio of frozen droplets to all droplets. Frozen fractions of the three particle types with different residence times from CLINCH will be presented in this study. The number of collisions between a single droplet and several aerosol particles can be calculated by accounting for the theoretical collision efficiency at the experimental conditions in order to obtain the freezing efficiency (frozen fraction/number of collisions). Nucleation efficiency is compared with other contact freezing studies and with immersion freezing

  18. Simultaneous measurements of wind shear and temperature gradient spectra in the stratosphere

    SciTech Connect

    Barat, J.; Cot, C. )

    1989-10-01

    The authors present in this paper the first high resolution analysis of wind shears and temperature gradient measured over 25 m in the low stratosphere. Their power spectral densities deduced by two different methods show that for vertical wavelengths greater than 500 m the behaviors of the temperature and vertical velocity fluctuating field are significantly different from the saturated wave model predictions.

  19. Fundamental Boiling and RP-1 Freezing Experiments

    NASA Technical Reports Server (NTRS)

    Goode, Brian; Turner, Larry D. (Technical Monitor)

    2001-01-01

    This paper describes results from experiments performed to help understand certain aspects of the MC-1 engine prestart thermal conditioning procedure. The procedure was constrained by the fact that the engine must chill long enough to get quality LOX at the LOX pump inlet but must be short enough to prevent freezing of RP-1 in the fuel pump. A chill test of an MC-1 LOX impeller was performed in LN2 to obtain data on film boiling, transition boiling and impeller temperature histories. The transition boiling data was important to the chill time so a subsequent experiment was performed chilling simple steel plates in LOX to obtain similar data for LOX. To address the fuel freezing concern, two experiments were performed. First, fuel was frozen in a tray and its physical characteristics were observed and temperatures of the fuel were measured. The result was physical characteristics as a function of temperature. Second was an attempt to measure the frozen thickness of RP-1 on a cold wall submerged in warm RP-1 and to develop a method for calculating that thickness for other conditions.

  20. Morphological study of endothelial cells during freezing.

    PubMed

    Zhang, A; Xu, L X; Sandison, G A; Cheng, S

    2006-12-01

    Microvascular injury is recognized as a major tissue damage mechanism of ablative cryosurgery. Endothelial cells lining the vessel wall are thought to be the initial target of freezing. However, details of this injury mechanism are not yet completely understood. In this study, ECMatrix 625 was used to mimic the tumour environment and to allow the endothelial cells cultured in vitro to form the tube-like structure of the vasculature. The influence of water dehydration on the integrity of this structure was investigated. It was found that the initial cell shape change was mainly controlled by water dehydration, dependent on the cooling rate, resulting in the shrinkage of cells in the direction normal to the free surface. As the cooling was prolonged and temperature was lowered, further cell shape change could be induced by the chilling effects on intracellular proteins, and focal adhesions to the basement membrane. Quantitative analysis showed that the freezing induced dehydration greatly enhanced the cell surface stresses, especially in the axial direction. This could be one of the major causes of the final breaking of the cell junction and cell detachment. PMID:17110769

  1. Entropy Budgets in Oscillating and Freezing Systems

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2005-12-01

    An interesting spontaneously oscillating system was demonstrated some decades ago by Welander : an open-topped water tank supplied with a continuous supply of heat is exposed to chilled air. A layer of ice forms, as one might expect. However, the ice retards the loss of heat to the air, and the water temperature rises until eventually the ice melts. The enhanced heat loss allows the system to cool again to the point where ice can form, and the cycle repeats. The oscillating behaviour is counterintuitive (like another freezing phenomenon, the Mpemba effect, wherein a warm liquid will begin freezing before a cool one), but is in full accord with the laws of thermodynamics and can be demonstrated in the laboratory and with numerical models. Oscillations occur in specific regions of parameter space (heating rate, heat transfer coefficients etc) - smooth variation, e.g. of the ice:air heat transfer coefficient yields a smooth variation of entropy production, except for a jump to increased entropy production when oscillations begin. A geophysical system where similar oscillations may occur is the icy Jovian satellite Europa, which appears to have a young crust. More generally, where a system is subject to a varying excitation (such as diurnal or seasonal forcing of the climate of Earth or Mars) the presence of phase changes such as melting of water or the condensation of carbon dioxide as frost have an important impact on the entropy budget of the system.

  2. Freeze-drying today and tomorrow.

    PubMed

    Leary, J H; Stanford, E A

    1976-10-01

    The freeze-drying process and equipment have been improved over the years; the cycle times have shortened and the dried products have improved as a result. This talk will deal with these improvements and how we have progressed from the early systems to where we are today. Such areas of discussion will include: vacuum pumping systems, how they are sized and designed to meet the needs for general and special applications; heat transfer systems, and their use in maintaining the drying profile; condensing surface design, and what is best for certain types of dryers; controls and instrumentation, and how these have played a big part in the drying process and have made it possible to get repeatability; refrigeration systems, and the part they play in the performance of freeze-drying; and lastly the effect of internal stoppering, bottomless trays, and other items such as these have had on the present state of the art. It goes without saying that there have been many changes and there will continue to be changes and we shall endeavor to look into the future--as to what might well bo some of these changes. Included in the talk will be a number of slides and illustrations to point out the various items as they are discussed. PMID:1030422

  3. Stress-gradient plasticity

    PubMed Central

    Chakravarthy, Srinath S.; Curtin, W. A.

    2011-01-01

    A new model, stress-gradient plasticity, is presented that provides unique mechanistic insight into size-dependent phenomena in plasticity. This dislocation-based model predicts strengthening of materials when a gradient in stress acts over dislocation source–obstacle configurations. The model has a physical length scale, the spacing of dislocation obstacles, and is validated by several levels of discrete-dislocation simulations. When incorporated into a continuum viscoplastic model, predictions for bending and torsion in polycrystalline metals show excellent agreement with experiments in the initial strengthening and subsequent hardening as a function of both sample-size dependence and grain size, when the operative obstacle spacing is proportional to the grain size. PMID:21911403

  4. Bigravity from gradient expansion

    NASA Astrophysics Data System (ADS)

    Yamashita, Yasuho; Tanaka, Takahiro

    2016-05-01

    We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.

  5. Expression of freeze-responsive proteins, Fr10 and Li16, from freeze-tolerant frogs enhances freezing survival of BmN insect cells.

    PubMed

    Biggar, Kyle K; Kotani, Eiji; Furusawa, Toshiharu; Storey, Kenneth B

    2013-08-01

    To date, two novel freeze-responsive proteins, Fr10 and Li16, have been discovered in the wood frog, Rana sylvatica, and likely support freezing survival. Although previous studies have established tissue distribution of each protein, there have been no studies that explore their functional consequences in intolerant cells. To assess the ability of Fr10 and Li16 to confer freeze tolerance, we transfected each protein into a freeze-intolerant silkworm cell line (BmN). Selected controls were the transfection of an unrelated protein (CAT) and a no-transfection sample. Li16 and Fr10 showed 1.8 ± 0.1- and 1.7 ± 0.2-fold, respectively, greater survival after freezing at -6°C for 1 h than did transfection controls. To investigate how these novel proteins protect cells from freezing damage, protein structures were predicted from primary amino acid sequences. Analysis of the structures indicated that Fr10 is a secreted protein and may be a new type IV antifreeze protein, whereas Li16 may have intracellular membrane associated functions. This study shows that freezing protection can be provided to intolerant cells by the overexpression of transfected Li16 and Fr10 frog proteins. Results from this study will provide new insights into adapting intolerant cells for medical organ cryoprotection using a natural vertebrate model of tolerance. PMID:23657819

  6. 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 (0C), constant freezing (-5C) and fluctuating temperature (0 to -5C) - 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 (-5C) compared with thawed controls (0C). 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

  7. Nappe emplacement under lateral pressure gradient

    NASA Astrophysics Data System (ADS)

    Podladchikov, Yury; Schmalholz, Stefan

    2014-05-01

    New thin viscous approximation is under development specifically targeted to model spontaneous initiation and tens of kilometers horizontal displacement of tectonic nappes. Nappes are few kilometers thing and tens of kilometers long rock units trusted towards foreland often preserving internal lithological consistency and laying at near horizontal position at the end of the emplacement. Significant shear stresses and deviation of principal stresses from vertical is required to explain this very peculiar strain localization style from mechanical point of view. There is also a need for the explanation of their common appearances in most collisional settings. Both pure shear thin sheet and flexural models kinematically eliminate nappes formation. Spreading viscous sheet models, such as used to model glaciers, are also not applicable as the direction of motion is upward, against gravity. The reason for this discrepancy is the hydrostatic pressure approximation of the gravity-driven spreading models. Actually, the thin sheet approximation is not sensitive to the assumptions made on pressure profile. Lateral non-lithostatic pressure gradient-driven viscous sheet model is appropriate for modeling of nappes. In turn, significant non-lithostatic pressure must be supported by flexural rigidity of overlying and underlying units. Lateral gradients of this non-lithostatic pressure are responsible for the significant shear stress and, therefore, deviation of principal stress from vertical.

  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 survival, body ice content and blood composition of the freeze-tolerant European common lizard, Lacerta vivipara.

    PubMed

    Voituron, Y; Storey, J M; Grenot, C; Storey, K B

    2002-01-01

    To investigate the freeze tolerance of the European common lizard, Lacerta vivipara, we froze 17 individuals to body temperatures as low as -4 degrees C under controlled laboratory conditions. The data show that this species tolerates the freezing of 50% of total body water and can survive freezing exposures of at least 24-h duration. Currently, this represents the best known development of freeze tolerance among squamate reptiles. Freezing stimulated a significant increase in blood glucose levels (16.15+/- 1.73 micromol x ml(-1) for controls versus 25.06 +/- 2.92 micromol x ml(-1) after thawing) but this increase had no significant effect on serum osmolality which was unchanged between control and freeze-exposed lizards (506.0 +/- 23.8 mosmol x l(-1) versus 501.0 +/- 25.3 mosmol x l(-1), respectively). Tests that assessed the possible presence of antifreeze proteins in lizard blood were negative. Recovery at 5 degrees C after freezing was assessed by measurements of the mean time for the return of breathing (5.9 +/- 0.5 h) and of the righting reflex (44.8 +/- 4.5 h). Because this species hibernates in wet substrates inoculative freezing may frequently occur in nature and the substantial freeze tolerance of this lizard should play a key role in its winter survival. PMID:11824405

  10. Effect of long-term freezing and freeze-thaw cycles on indigenous and inoculated microorganisms in dewatered blackwater.

    PubMed

    Gunnarsdóttir, Ragnhildur; Müller, Karoline; Jensen, Pernille Erland; Jenssen, Petter Deinboll; Villumsen, Arne

    2012-11-20

    Wastewater treatment in many Arctic regions is inadequate, even nonexisting. Natural freezing of wastewater in those areas may be beneficial for reduction of microorganisms. The aim of this study was to investigate the effect of long-term freezing, and repeated freezing and thawing, on indigenous coliforms, fecal streptococci, and antibiotic-resistant (AR) bacteria, and inoculated Salmonella Enteriditis and E. coli bacteriophage ΦX174 in dewatered blackwater. At the end of the long-term freezing experiment (10 months), an MPN recovery study was done, including the microbial groups that had shown the largest reduction, using tryptone soy broth at incubation temperatures of 10 and 20 °C overnight for the coliforms and AR bacteria, and buffered peptone water at incubation temperature of 37 °C for 18-20 h for Salmonella. Fecal streptococci were more resistant to long-term freezing than the coliform group. Total number of AR bacteria decreased slowly but constantly over the 10-month freezing period. Salmonella rapidly decreased and were nondetectable within a week but exhibited some recovery after 10 months of freezing, whereas limited or no recovery of coliforms and AR-bacteria was detected. Bacteriophages showed limited reduction during the long-term freezing. Repeated freezing and thawing increased the reduction of all tested microbial groups markedly. PMID:23113759

  11. Controlled Freeze-thaw Experiments to Study Biogeochemical Process and its Effects on Greenhouse Gas Release in Arctic Soil Columns

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Kneafsey, T. J.; Tas, N.; Bill, M.; Ulrich, C.; Hubbard, S. S.

    2014-12-01

    Greenhouse gas release associated with permafrost thawing is one of the largest uncertainties in future climate prediction. Improvement of such prediction relies on a better representation of the interactions between hydrological, geochemical and microbial processes in the Arctic ecosystem that occur over a wide range of space and time scales and under dynamic freeze-thaw conditions. As part of the Next Generation Ecosystem Experiments in the Arctic (NGEE-Arctic), we conducted controlled laboratory freeze-thaw experiments to study greenhouse gas release in vertical permafrost soil columns with vertically heterogeneous hydrological, geochemical and microbial properties. The studies were performed using soil cores collected from the NGEE Barrow, AK site. Two cores collected next to each other with very similar soil structures were used for the experiment. One of the cores was destructively sampled for baseline characterization, and the second core was used for the freeze-thaw experiments. The core extends from the ground surface into the permafrost with roughly 40 cm of active layer. The column was instrumented with various sensors and sampling devices, including thermocouples, geophysical (electrical) sensors, and sampling ports for solids and fluids. The headspace of the soil column was purged with CO2 free air and the gas samples were collected periodically for greenhouse gas analysis. Our initial tests simulated seasonal temperature variation from ~ -10°C to +10°C at the ground surface. Our results demonstrated that temperature and geophysical data provided real time information on the freeze thaw dynamics of the column and the surface greenhouse gas fluxes correlated with the freeze thaw stages and associated hydrological and biogeochemical processes in the vertical soil column. For example, surface fluxes data revealed an early burst of GHG concentrations during the initial thawing of the surface ice rich layer of the soil, indicating the presence of trapped gases from previous season activities. In addition, the dynamics of the surface flux are closely related to the changes of the geochemical and microbial conditions during the freeze thaw processes.

  12. Vertical flowline connector

    SciTech Connect

    Saliger, K. C.

    1985-10-01

    Several embodiments are disclosed of a vertical type of flowline connector for providing a fluid connection between a horizontal flowline and an additional subsea facility. The upper and lower portions of the connector can be properly positioned relative to each other by simply lowering an upper female portion of the connector onto a lower male portion thereof. The lower portion of the connector at the subsea facility is provided with at least two vertically positioned, upwardly facing male mandrel connectors. The upper portion of the connector assembly includes at least two vertically positioned, downwardly facing corresponding female connectors designed to be lowered onto the corresponding male mandrel connectors. At least one of the female connectors is mounted on the connector assembly by a free floating mounting. The free floating mounting allows for slight misalignments of the female connectors relative to the corresponding male connectors as the upper connector assembly is lowered onto, and passively positioned relative to, the lower connector assembly.

  13. Improved vertical scanning interferometry

    NASA Astrophysics Data System (ADS)

    Harasaki, Akiko

    2000-11-01

    Vertical scanning interferometers are routinely used for the measurement of optical fiber connectors. There are increasing needs for measurements of such items as machined surfaces, contact lenses, paint texture, cell structure, and integrated circuit devices, to name a few. These structures have too much depth, or are too rough, to measure with standard interferometry methods. Phase- measurement interferometry methods are limited to surfaces that do not have any discontinuities larger than one quarter of the operating wavelength. On the other hand, vertical scanning interferometers can be very effective, even though they have low height resolution compared to that of phase-measurement interferometers. Improving the height resolution of vertical scanning interferometers from the point of hardware improvement and signal processing has been one of the major research interests in the surface metrology area. This work provides a new algorithm, which called here ``PSI on the Fly'' technique, as a solution for improving height resolution of vertical scanning interferometers. This dissertation begins with a review of white-light interference microscopes. The height and lateral resolutions are derived based on scalar diffraction theory. Next, various well-established. algorithms for finding a topographic map of the small object surface are discussed. The work proceeds with a discussion of the phase change upon reflection and its influence on the coherence envelope. Then phase measurement interferometry methods are reviewed. The emphasis is in errors in phase measurement resulting from using a white light source instead of a monochromatic light source as in the usual case. The following chapter describes and examines an often- observed artifact of vertical-scanning interferometry when applied to step heights. The artifact is called ``bat wings'' because of its appearance. The physical cause of the ``bat wings'' artifact is discussed through a diffraction model. The next chapter proposes an improved vertical-scanning interferometry algorithm. The method, called here ``PSI on the Fly'' technique, has been developed by combining regular vertical-scanning interferometry and a monochromatic phase-shifting interferometry technique. The PSI on the Fly technique improves the surface height resolution of vertical scanning interferometry to that of a phase-shifting interferometry measurement. In addition to the resolution improvement, the algorithm also successfully removes the ``bat wings'' artifact.

  14. Freezing in porous media: Phase behavior, dynamics and transport phenomena

    SciTech Connect

    Wettlaufer, John S.

    2012-12-21

    This research was focused on developing the underlying framework for the mechanisms that control the nature of the solidification of a broad range of porous media. To encompass the scope of porous media under consideration we considered material ranging from a dilute colloidal suspension to a highly packed saturated host matrix with a known geometry. The basic physical processes that occur when the interstitial liquid phase solidifies revealed a host of surprises with a broad range of implications from geophysics to materials science and engineering. We now understand that ostensibly microscopic films of unfrozen liquid control both the equilibrium and transport properties of a highly packed saturated host matrix as well as a rather dilute colloidal suspension. However, our description of the effective medium behavior in these settings is rather different and this sets the stage for the future research based on our past results. Once the liquid phase of a saturated relatively densely packed material is frozen, there is a rich dynamical behavior of particles for example due to the directed motion driven by thermomolecular pressure gradients or the confined Brownian motion of the particles. In quite striking contrast, when one freezes a dilute suspension the behavior can be rather more like that of a binary alloy with the particles playing the role of a ``solute''. We probed such systems quantitatively by (i) using X ray photon correlation spectroscopy (XPCS) and Small Angle X-ray Scattering (SAXS) at the Advanced Photon Source at Argonne (ii) studying the Argonne cell in the laboratory using optical microscopy and imagery (because it is not directly visible while in the vacuum can). (3) analyzed the general transport phenomena within the framework of both irreversible thermodynamics and alloy solidification and (4) applied the results to the study of the redistribution of solid particles in a frozen interstitial material. This research has gone a long way towards establishing a quantitative foundation for a wide class of problems in environmental and technological settings.

  15. Metabolic changes in Avena sativa crowns recovering from freezing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 recove...

  16. Prospective Primary School Teachers' Perceptions on Boiling and Freezing

    ERIC Educational Resources Information Center

    Senocak, Erdal

    2009-01-01

    The aim of this study was to investigate the perceptions of prospective primary school teachers on the physical state of water during the processes of boiling and freezing. There were three stages in the investigation: First, open-ended questions concerning the boiling and freezing of water were given to two groups of prospective primary school…

  17. Understanding freeze stress in biological tissues: thermodynamics of interfacial water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A thermodynamic approach to distinguish forms of freeze energy that injure plants as the temperature decreases is developed. The pattern resulting from this analysis dictated the sequence of thermal requirements for water to exist as an independent state. Improvement of freezing tolerance in biolo...

  18. Observation of a freezing drizzle episode: A case study

    NASA Astrophysics Data System (ADS)

    Fernández-González, S.; Valero, F.; Sanchez, Jose L.; Gascón, E.; López, L.; García-Ortega, E.; Merino, A.

    2014-11-01

    On 5 February 2012 an episode of freezing precipitation took place in the Guadarrama Mountains, at the center of the Iberian Peninsula. This precipitation affected high elevations, where temperatures remained below freezing because of snow cover that had accumulated from snowfall during the previous days. The case study was recorded by surface synoptic observations (SYNOP) at Navacerrada Pass meteorological observatory (belonging to the National Weather Service of Spain). To study winter cloud systems during the TEcoAgua project, a multichannel ground-based microwave radiometer (MMWR), Micro Rain Radar (MRR-2), and isothermal cloud chamber were installed in the study area, thus permitting the monitoring of the freezing precipitation event. Analysis using Meteosat Second Generation (MSG) satellite data and observations permitted the determination of factors that triggered the freezing precipitation event. Freezing drizzle was interspersed with the passage of a warm and cold front. During frontal passage, mid-level clouds inhibited the generation of freezing drizzle, with snowfall recorded in the study area. However, during the period between the two fronts, an absence of mid-level clouds permitted low-level orographic clouds to persist upwind of the mountain system, producing freezing drizzle at the surface. The decisive factors for the generation of freezing drizzle were high humidity at low levels, weak mesoscale updrafts caused by the topography, stability at mid levels, cloud-top temperatures warmer than - 15 °C, and low concentrations of ice nuclei.

  19. 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...

  20. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events

    PubMed Central

    O’Keefe, Kimberly; Nippert, Jesse B.; Swemmer, Anthony M.

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  1. Experimental investigation of molten metal freezing on to a structure

    SciTech Connect

    Mizanur Rahman, M.; Hino, Tomohiko; Morita, Koji; Matsumoto, Tatsuya; Nakagawa, Kiyoshi; Fukuda, Kenji; Maschek, Werner

    2007-10-15

    During core disruptive accidents (CDAs) of Liquid Metal Reactors (LMRs), it is important to understand the freezing phenomena of molten metal, which may prevent fuel dispersal and subsequent shutdown. The present paper describes the freezing behavior of molten metal during interaction with a structure with a view to the safety of LMRs. In this study, Wood's metal (melting point 78.8 C) was used as a simulant melt, while stainless steel and copper were used as freezing structures. A series of simulation experiments was conducted to study the freezing behavior of Wood's metal during pouring on to the freezing structures immersed in a coolant. In the experiments, simulant melt was poured into a stainless steel tube and finally ejected into a coolant through a nozzle so as to observe the freezing behavior of the molten metal. The penetration length and width were measured in the air cooled experiments, whereas penetration length and the proportion of adhering frozen metal were measured in water coolant experiment. The melt flow and distribution were observed in both types of experiment using a high-speed video camera. Distinct freezing modes were observed in the water coolant experiments, whereas only one freezing mode with a longer melt penetration was found in air coolant experiments. The present result will be utilized to create a relevant database for the verification of reactor safety analysis codes. (author)

  2. Spin dynamics and freezing in magnetic rare-earth quasicrystals

    NASA Astrophysics Data System (ADS)

    Noakes, D. R.; Kalvius, G. M.; Wäppling, R.; Stronach, C. E.; White, M. F., Jr.; Saito, H.; Fukamichi, K.

    1998-02-01

    Muon spin relaxation measurements of RE 8Mg 42Zn 50 (RE = Gd, Tb) quasicrystals have revealed slower spin dynamics and more prompt spin freezing for Tb than Gd, due to “crystalline electric field” splitting in low rare-earth site symmetry. Inhomogeneous spin freezing leads to a low-temperature state with local field distribution characteristic of a concentrated disordered magnet.

  3. Optimum parameters for freeze-drying decellularized arterial scaffolds.

    PubMed

    Sheridan, William S; Duffy, Garry P; Murphy, Bruce P

    2013-12-01

    Decellularized arterial scaffolds have achieved success in advancing toward clinical use as vascular grafts. However, concerns remain regarding long-term preservation and sterilization of these scaffolds. Freeze drying offers a means of overcoming these concerns. In this study, we investigated the effects of various freeze-drying protocols on decellularized porcine carotid arteries and consequently, determined the optimum parameters to fabricate a stable, preserved scaffold with unaltered mechanical properties. Freeze drying by constant slow cooling to two final temperatures ((Tf), -10 °C and -40 °C) versus instant freezing was investigated by histological examination and mechanical testing. Slow cooling to Tf= -10 °C produced a stiffer and less distensible response than the non freeze-dried scaffolds and resulted in disruption to the collagen fibers. The mechanical response of Tf= -40 °C scaffolds demonstrated disruption to the elastin network, which was confirmed with histology. Snap freezing scaffolds in liquid nitrogen and freeze drying to Tf= -40 °C with a precooled shelf at -60 °C produced scaffolds with unaltered mechanical properties and a histology resembling non-freeze-dried scaffolds. The results of this study demonstrate the importance of optimizing the nucleation and ice crystal growth/size to ensure homogenous drying, preventing extracellular matrix disruption and subsequent inferior mechanical properties. This new manufacturing protocol creates the means for the preservation and sterilization of decellularized arterial scaffolds while simultaneously maintaining the mechanical properties of the tissue. PMID:23614758

  4. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 5 2011-01-01 2011-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze...

  5. Design of freeze-drying processes for pharmaceuticals: practical advice.

    PubMed

    Tang, Xiaolin; Pikal, Michael J

    2004-02-01

    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, as long as some simple rules based on well-accepted scientific principles are followed. It is the purpose of this review to discuss the scientific foundations of the freeze-drying process design and then to consolidate these principles into a set of guidelines for rational process design and optimization. General advice is given concerning common stability issues with proteins, but unusual and difficult stability issues are beyond the scope of this review. Control of ice nucleation and crystallization during the freezing step is discussed, and the impact of freezing on the rest of the process and final product quality is reviewed. Representative freezing protocols are presented. The significance of the collapse temperature and the thermal transition, denoted Tg', are discussed, and procedures for the selection of the "target product temperature" for primary drying are presented. Furthermore, guidelines are given for selection of the optimal shelf temperature and chamber pressure settings required to achieve the target product temperature without thermal and/or mass transfer overload of the freeze dryer. Finally, guidelines and "rules" for optimization of secondary drying and representative secondary drying protocols are presented. PMID:15032301

  6. 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…

  7. 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...

  8. 7 CFR 305.7 - Quick freeze treatment requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 5 2012-01-01 2012-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze...

  9. 40 CFR 52.1135 - Regulation for parking freeze.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... conform to the requirements of 40 CFR 51.4(b); and the agency rules or procedures may provide that if no... 40 Protection of Environment 4 2011-07-01 2011-07-01 false Regulation for parking freeze. 52.1135... for parking freeze. (a) Definitions: (1) The phrase to commence construction means to engage in...

  10. 40 CFR 52.1135 - Regulation for parking freeze.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... conform to the requirements of 40 CFR 51.4(b); and the agency rules or procedures may provide that if no... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Regulation for parking freeze. 52.1135... for parking freeze. (a) Definitions: (1) The phrase to commence construction means to engage in...

  11. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events.

    PubMed

    O'Keefe, Kimberly; Nippert, Jesse B; Swemmer, Anthony M

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  12. 40 CFR 52.1135 - Regulation for parking freeze.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 4 2013-07-01 2013-07-01 false Regulation for parking freeze. 52.1135 Section 52.1135 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS (CONTINUED) Massachusetts § 52.1135 Regulation for parking freeze. (a) Definitions:...

  13. 40 CFR 52.1135 - Regulation for parking freeze.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Regulation for parking freeze. 52.1135 Section 52.1135 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS (CONTINUED) Massachusetts § 52.1135 Regulation for parking freeze. (a) Definitions:...

  14. 47 CFR 64.1190 - Preferred carrier freezes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... electronic authorization should confirm appropriate verification data (e.g., the subscriber's date of birth... subscriber's date of birth or social security number) and the information required in § 64.1190(d)(3)(ii)(A... carrier administering the freeze and the subscriber in order to lift a freeze. When engaged in...

  15. Stopping biological time: The freezing of living cells

    SciTech Connect

    Mazur, P.

    1987-01-01

    The fundamental physical-chemical events that occur during the freezing and thawing of cells are outlined and the manner in which cell permeability determines the response of the cell to freezing is discussed both in terms of physical response and in terms of survival. 40 refs., 12 figs.

  16. Optimum Parameters for Freeze-Drying Decellularized Arterial Scaffolds

    PubMed Central

    Sheridan, William S.; Duffy, Garry P.

    2013-01-01

    Decellularized arterial scaffolds have achieved success in advancing toward clinical use as vascular grafts. However, concerns remain regarding long-term preservation and sterilization of these scaffolds. Freeze drying offers a means of overcoming these concerns. In this study, we investigated the effects of various freeze-drying protocols on decellularized porcine carotid arteries and consequently, determined the optimum parameters to fabricate a stable, preserved scaffold with unaltered mechanical properties. Freeze drying by constant slow cooling to two final temperatures ((Tf), −10°C and −40°C) versus instant freezing was investigated by histological examination and mechanical testing. Slow cooling to Tf= −10°C produced a stiffer and less distensible response than the non freeze-dried scaffolds and resulted in disruption to the collagen fibers. The mechanical response of Tf= −40°C scaffolds demonstrated disruption to the elastin network, which was confirmed with histology. Snap freezing scaffolds in liquid nitrogen and freeze drying to Tf= −40°C with a precooled shelf at −60°C produced scaffolds with unaltered mechanical properties and a histology resembling non-freeze-dried scaffolds. The results of this study demonstrate the importance of optimizing the nucleation and ice crystal growth/size to ensure homogenous drying, preventing extracellular matrix disruption and subsequent inferior mechanical properties. This new manufacturing protocol creates the means for the preservation and sterilization of decellularized arterial scaffolds while simultaneously maintaining the mechanical properties of the tissue. PMID:23614758

  17. Heat pump with freeze-up prevention

    DOEpatents

    Ecker, Amir L.

    1981-01-01

    What is disclosed is a heat pump apparatus for conditioning a fluid characterized by a fluid handler and path for circulating the fluid in heat exchange relationship with a refrigerant fluid; at least two refrigerant heat exchangers, one for effecting heat exchange with the fluid and a second for effecting heat exchange between refrigerant and a heat exchange fluid and the ambient air; a compressor for efficiently compressing the refrigerant; at least one throttling valve for throttling liquid refrigerant; a refrigerant circuit; refrigerant; a source of heat exchange fluid; heat exchange fluid circulating device and heat exchange fluid circuit for circulating the heat exchange fluid in heat exchange relationship with the refrigerant; and valves or switches for selecting the heat exchangers and direction of flow of the refrigerant therethrough for selecting a particular mode of operation. The heat exchange fluid prevents freeze up of the second heat exchanger by keeping the temperature above the dew point; and, optionally, provides heat for efficient operation.

  18. STEFINS: a steel freezing integral simulation program

    SciTech Connect

    Frank, M.V.

    1980-09-01

    STEFINS (STEel Freezing INtegral Simulation) is a computer program for the calculation of the rate of solidification of molten steel on solid steel. Such computations arize when investigating core melt accidents in fast reactors. In principle this problem involves a coupled two-dimensional thermal and hydraulic approach. However, by physically reasonable assumptions a decoupled approach has been developed. The transient solidification of molten steel on a cold wall is solved in the direction normal to the molten steel flow and independent from the solution for the molten steel temperature and Nusselt number along the direction of flow. The solutions to the applicable energy equations have been programmed in cylindrical and slab geometries. Internal gamma heating of steel is included.

  19. Freezing of Martian streams under climatic conditions

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1984-01-01

    The valley networks of Mars are widely believed to have formed at a time when climatic conditions on the planet were significantly different from those that currently prevail. This view arises from the following observations: (1) the valleys form integrated branching networks which suggests fluid drainage, and water is the most plausible fluid, (2) the present atmosphere contains only minute amounts of water, (3) the networks appear to be more akin to terrestrial valleys that are eroded by streams of modest discharges than features that form by catastrophic floods, and (4) small streams of water will rapidly freeze under present climatic conditions. Climatic conditions at the time of formation of the valleys are studied based on the assumption that they were cut by running water.

  20. Freezing D2O clay gels.

    PubMed

    Letellier, M

    1998-01-01

    To obtain the T1 surface value in smectites/D2O diluted suspensions or gels, as was obtained on a monolayer deuterated clay, we freeze them. The broad Pake's doublets similar to ice doublets and with the same T1 show that we can separate frozen from unfrozen D2O. The latter exhibits a narrower line and a single T1 and is attributed to the liquid surface water layer in rapid exchange with the nearby supercooled water, the quantity of which diminishes with the lowering of the temperature depending on the gel porosity. It is possible to measure the supercooled water quantity and to correct the T1 measured values to extract the T1 surface. The value extrapolated at room temperature allows the complete clay surface area measurement. The example of a montmorillonite is given and a comparison with laponite is made. PMID:9803898

  1. Crystal structures and freezing of dipolar fluids.

    PubMed

    Groh, B; Dietrich, S

    2001-02-01

    We investigate the crystal structure of classical systems of spherical particles with an embedded point dipole at T=0. The ferroelectric ground state energy is calculated using generalizations of the Ewald summation technique. Due to the reduced symmetry compared to the nonpolar case the crystals are never strictly cubic. For the Stockmayer (i.e., Lennard-Jones plus dipolar) interaction three phases are found upon increasing the dipole moment: hexagonal, body-centered orthorhombic, and body-centered tetragonal. An even richer phase diagram arises for dipolar soft spheres with a purely repulsive inverse power law potential approximately r(-n). A crossover between qualitatively different sequences of phases occurs near the exponent n=12. The results are applicable to electro- and magnetorheological fluids. In addition to the exact ground state analysis we study freezing of the Stockmayer fluid by density-functional theory. PMID:11308482

  2. Conservation of mouse models through embryo freezing.

    PubMed

    Guan, Mo; Bogani, Debora; Marschall, Susan; Raspa, Marcello; Takeo, Toru; Nakagata, Naomi; Fray, Martin

    2014-01-01

    The ability to interrogate the entire coding sequence of the mouse combined with the tools to manipulate the genome has firmly established the mouse as the model organism of choice for studying the causes of human disease. Consequently, a huge number of novel mouse models are generated each year to support active research programs. However, it is neither ethically justifiable, nor economically viable to maintain mouse colonies on the shelf that are not part of active research programs. This means that novel mouse lines have to be preserved in some way. If this is not done and the line is simply killed off, the genetics will be lost to future generations of scientists. This article describes the current practices used in cryopreservation laboratories to archive and recover mouse embryos frozen using controlled-rate freezing and vitrification techniques. PMID:25723186

  3. Climatic variability and the evolution of insect freeze tolerance.

    PubMed

    Sinclair, Brent J; Addo-Bediako, A; Chown, Steven L

    2003-05-01

    Insects may survive subzero temperatures by two general strategies: Freeze-tolerant insects withstand the formation of internal ice, while freeze-avoiding insects die upon freezing. While it is widely recognized that these represent alternative strategies to survive low temperatures, and mechanistic understanding of the physical and molecular process of cold tolerance are becoming well elucidated, the reasons why one strategy or the other is adopted remain unclear. Freeze avoidance is clearly basal within the arthropod lineages, and it seems that freeze tolerance has evolved convergently at least six times among the insects (in the Blattaria, Orthoptera, Coleoptera, Hymenoptera, Diptera and Lepidoptera). Of the pterygote insect species whose cold-tolerance strategy has been reported in the literature, 29% (69 of 241 species studied) of those in the Northern Hemisphere, whereas 85 % (11 of 13 species) in the Southern Hemisphere exhibit freeze tolerance. A randomization test indicates that this predominance of freeze tolerance in the Southern Hemisphere is too great to be due to chance, and there is no evidence of a recent publication bias in favour of new reports of freeze-tolerant species. We conclude from this that the specific nature of cold insect habitats in the Southern Hemisphere, which are characterized by oceanic influence and climate variability must lead to strong selection in favour of freeze tolerance in this hemisphere. We envisage two main scenarios where it would prove advantageous for insects to be freeze tolerant. In the first, characteristic of cold continental habitats of the Northern Hemisphere, freeze tolerance allows insects to survive very low temperatures for long periods of time, and to avoid desiccation. These responses tend to be strongly seasonal, and insects in these habitats are only freeze tolerant for the overwintering period. By contrast, in mild and unpredictable environments, characteristic of habitats influenced by the Southern Ocean, freeze tolerance allows insects which habitually have ice nucleators in their guts to survive summer cold snaps, and to take advantage of mild winter periods without the need for extensive seasonal cold hardening. Thus, we conclude that the climates of the two hemispheres have led to the parallel evolution of freeze tolerance for very different reasons, and that this hemispheric difference is symptomatic of many wide-scale disparities in Northern and Southern ecological processes. PMID:12803420

  4. 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.

  5. Aiding Vertical Guidance Understanding

    NASA Technical Reports Server (NTRS)

    Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

    1998-01-01

    A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

  6. Vertical shaft windmill

    NASA Technical Reports Server (NTRS)

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

    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. Versatile Aerogel Fabrication by Freezing and Subsequent Freeze-Drying of Colloidal Nanoparticle Solutions.

    PubMed

    Freytag, Axel; Sánchez-Paradinas, Sara; Naskar, Suraj; Wendt, Natalja; Colombo, Massimo; Pugliese, Giammarino; Poppe, Jan; Demirci, Cansunur; Kretschmer, Imme; Bahnemann, Detlef W; Behrens, Peter; Bigall, Nadja C

    2016-01-18

    A versatile method to fabricate self-supported aerogels of nanoparticle (NP) building blocks is presented. This approach is based on freezing colloidal NPs and subsequent freeze drying. This means that the colloidal NPs are directly transferred into dry aerogel-like monolithic superstructures without previous lyogelation as would be the case for conventional aerogel and cryogel fabrication methods. The assembly process, based on a physical concept, is highly versatile: cryogelation is applicable for noble metal, metal oxide, and semiconductor NPs, and no impact of the surface chemistry or NP shape on the resulting morphology is observed. Under optimized conditions the shape and volume of the liquid equal those of the resulting aerogels. Also, we show that thin and homogeneous films of the material can be obtained. Furthermore, the physical properties of the aerogels are discussed. PMID:26638874

  8. What happens in freezing bodies? Experimental study of histological tissue change caused by freezing injuries.

    PubMed

    Schäfer, A T; Kaufmann, J D

    1999-06-28

    In order to evaluate histological features of freezing damages to human tissue after death, we froze samples of liver and heart tissue to temperatures of -12 degrees C, -28 degrees C and -80 degrees C, and stored them for 24 and 72 h, respectively, at those temperatures. After thawing and routine preparation for histology, the samples were evaluated both by microscope and with an electronic image analyzer. In all cases, we found extended extracellular spaces and shrunken cells resulting from the freeze-thaw cycle. These features were more pronounced in tissues stored for longer durations. Such findings seem to be typical of tissue that has been frozen prior to examination. Two cases of dead bodies found outdoors at subzero temperatures demonstrate that formerly frozen and unfrozen tissues can be distinguished histologically. The findings are examined in relation to the fundamental laws of cryobiology. PMID:10464930

  9. Freeze-fracture cytochemistry: partition of glycophorin in freeze- fractured human erythrocyte membranes

    PubMed Central

    1982-01-01

    Thin-section and critical-point-dried fracture-labeled preparations are used to determine the distribution and partition of glycophorin- associated wheat germ agglutinin (WGA) binding sites over protoplasmic and exoplasmic faces of freeze-fractured human erythrocyte membranes. Most wheat germ agglutinin binding sites are found over exoplasmic faces. Label is sparse over the protoplasmic faces. These results contrast with previous observations of the partition of band 3 component where biochemical analysis and fracture-label of concanavalin A (Con A) binding sites show preferential partition of this transmembrane protein with the protoplasmic face. Presence of characteristic proportions of WGA and Con A binding sites over each fracture face is interpreted to indicate the operation of a stochastic process during freeze-fracture. This process appears modulated by the relative expression of each transmembrane protein at either surface as well as by their association to components of the erythrocyte membrane skeleton. PMID:7096449

  10. 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

  11. 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.

  12. Freeze plug proves safe, economical in riser repair

    SciTech Connect

    Nelson, M.J.

    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.

  13. Sources of Data on Freezing Rain and Resulting Damages.

    NASA Astrophysics Data System (ADS)

    Changnon, Stanley A.; Creech, Tamara G.

    2003-10-01

    Freezing rain produces major damages each year in the United States, and various affected groups continue to seek data on the incidence and losses produced by freezing rain. The various kinds of data available about freezing rain and related damages have been identified and assessed as part of a project to develop long-term databases. Data include long-term records of the occurrences of freezing rain, 50-yr records of insured property losses, and measures and estimates of ice loading on wires and structures. Many years of interactions with affected and interested groups and individuals, such as the insurance industry and design engineers, led to the preparation of this summary that describes the various sources of data on freezing-rain and ice-storm damages. The benefits and limitations of each form of data are presented to help to guide potential data users.

  14. 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.

  15. 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.

  16. 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

  17. Energy in density gradient

    SciTech Connect

    Vranjes, J.; Kono, M.

    2015-01-15

    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.

  18. Investigation of the stabilizing effects of hydroxyethyl cellulose on LDH during freeze drying and freeze thawing cycles.

    PubMed

    Al-Hussein, Anas; Gieseler, Henning

    2015-01-01

    The objective of this study was to investigate both the cryoprotective and lyoprotective effects of the polymer hydroxyethyl cellulose (HEC) on the model protein lactate dehydrogenase (LDH) during freeze thawing and freeze drying cycles. The effect of annealing on both protein stability and the physical state of HEC was evaluated. HEC was used as a sole excipient in the protein formulations, and its stabilizing was compared to that of other excipients which are commonly used in freeze dried protein formulations. Furthermore, other quality aspects of the freeze dried samples containing solely HEC were investigated, such as, reconstitution time and product elegance. Protein stability was evaluated functionally by measuring the activity recovery of the model protein LDH. The physical state of HEC after freeze drying was investigated and compared to this of other studied solutes using differential scanning calorimetry and X-ray powder diffractometry. HEC showed superior cryoprotective effects on LDH during freeze thawing, and considerable lyoprotective effects during the freeze drying process. Annealing had limited influence on the stabilizing effect of HEC. The extensive reconstitution times of the HEC lyophilisates could be greatly improved by incorporation of the surfactant Tween 80 into the formulations prior to freeze drying. PMID:24286265

  19. 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.

  20. Two-Zone Bridgman Furnace With Sharp Thermal Gradient

    NASA Technical Reports Server (NTRS)

    Borshchevsky, Alex; Caillat, Thierry; Fleurial, Jean-Pierre

    1994-01-01

    Two-zone vertical directional-solidification furnace designed and built to grow crystals from stoichiometric and nonstoichiometric melts and from solutions. Includes conventional wire heater in lower zone, tubular silicon carbide heating element in upper zone, and thermal baffle between zones. Temperature gradients up to 125 degrees centigrade per centimeter achieved in the crystal-growth region. Sharper gradient enables both faster growth and better separation between solid and liquid. Furnace used in laboratory or industrial setting for growth of crystals from congruently melting materials as well as for growth of compounds formed by peritectic reactions.

  1. Freezing Behavior of Water in Small Pores and the Possible Role in the Freezing of Plant Tissues

    PubMed Central

    Ashworth, Edward N.; Abeles, Fred B.

    1984-01-01

    Two model systems were used to study the freezing of water in small diameter pores. Water in pores having a diameter of less than 100 nanometers froze at lower temperatures than bulk water. Data obtained with a range of pore sizes were consistent with predicted values based on equations developed by Mazur (1965 Ann NY Acad Sci 125: 658-676), and Homshaw (1980 J Soil Sci 31: 399-414). The addition of solutes lowered the freezing point of water in small pores. We propose that the freezing behavior of water in small pores may account for some of the freezing patterns observed in plant tissues. In tissues where cells are tightly packed, share common walls, and lack intercellular spaces, the presence of water in cell wall microcapillaries would alter the freezing temperature of tissue water, impede the spread of ice, and facilitate supercooling. PMID:16663798

  2. Effects of industrial pre-freezing processing and freezing handling on glucosinolates and antioxidant attributes in broccoli florets.

    PubMed

    Cai, Congxi; Miao, Huiying; Qian, Hongmei; Yao, Leishuan; Wang, Bingliang; Wang, Qiaomei

    2016-11-01

    The effects of industrial pre-freezing processing and freezing handling on the contents of glucosinolates and antioxidants (vitamin C, polyphenols, carotenoid and chlorophyll), as well as the antioxidant capacity in broccoli (Brassica oleracea L. var. italica) florets were investigated in the present study. Our results showed that the glucosinolate accumulations were significantly decreased after pre-freezing processing, whereas elevated levels of phenols, carotenoids, chlorophyll, and also antioxidant capacity were observed in frozen broccoli florets. The contents of vitamin C remained constant during above mentioned processing. In conclusion, the current industrial freezing processing method is a good practice for the preservation of main antioxidant nutrients in broccoli florets, although some improvements in pre-freezing processing, such as steam blanching and ice-water cooling, are needed to attenuate the decrease in glucosinolate content. PMID:27211670

  3. 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.

  4. Reconstructing global overturning from meridional density gradients

    NASA Astrophysics Data System (ADS)

    Butler, E. D.; Oliver, K. I. C.; Hirschi, J. J.-M.; Mecking, J. V.

    2016-04-01

    Despite the complexity of the global ocean system, 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 1000 m) for multi-decadal (and longer) timescales, accurately reconstructing the relative magnitude of the response for different frequencies and explaining over 85 % of overturning variance on timescales of 64-2048 years. Despite the highly nonlinear response of the Antarctic cell in the abyssal Atlantic, between 76 and 94 % of the observed variability at 4000 m is reconstructed on timescales of 32 years (and longer). The scaling law is also applied in the Indo-Pacific. This analysis is extended to a higher resolution, stochastically forced simulation for which correlations of between 0.79 and 0.99 are obtained with upper Atlantic MOC variability on timescales >25 years. These results indicate that meridional density gradients and overturning are linked via meridional pressure gradients, and that both the strength and structure of the MOC can be reconstructed from hydrography on multi-decadal and longer timescales provided that the link is made in this way.

  5. Reconstructing global overturning from meridional density gradients

    NASA Astrophysics Data System (ADS)

    Butler, E. D.; Oliver, K. I. C.; Hirschi, J. J.-M.; Mecking, J. V.

    2015-07-01

    Despite the complexity of the global ocean system, 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 1000 m) for multi-decadal (and longer) timescales, accurately reconstructing the relative magnitude of the response for different frequencies and explaining over 85 % of overturning variance on timescales of 64-2048 years. Despite the highly nonlinear response of the Antarctic cell in the abyssal Atlantic, between 76 and 94 % of the observed variability at 4000 m is reconstructed on timescales of 32 years (and longer). The scaling law is also applied in the Indo-Pacific. This analysis is extended to a higher resolution, stochastically forced simulation for which correlations of between 0.79 and 0.99 are obtained with upper Atlantic MOC variability on timescales >25 years. These results indicate that meridional density gradients and overturning are linked via meridional pressure gradients, and that both the strength and structure of the MOC can be reconstructed from hydrography on multi-decadal and longer timescales provided that the link is made in this way.

  6. Magnetic shielding for the Fermilab Vertical Cavity Test Facility

    SciTech Connect

    Ginsburg, Camille M.; Reid, Clark; Sergatskov, Dmitri A.; /Fermilab

    2008-09-01

    A superconducting RF cavity has to be shielded from magnetic fields present during cool down below the critical temperature to avoid freezing in the magnetic flux at localized impurities, thereby degrading the cavity intrinsic quality factor Q{sub 0}. The magnetic shielding designed for the Fermilab vertical cavity test facility (VCTF), a facility for CW RF vertical testing of bare ILC 1.3 GHz 9-cell SRF cavities, was recently completed. For the magnetic shielding design, we used two cylindrical layers: a room temperature 'outer' shield of Amumetal (80% Ni alloy), and a 2K 'inner' shield of Cryoperm 10. The magnetic and mechanical design of the magnetic shielding and measurement of the remanent magnetic field inside the shielding are described.

  7. 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.

  8. Purification of very high density lipoproteins by differential density gradient ultracentrifugation.

    PubMed

    Haunerland, N H; Ryan, R O; Law, J H; Bowers, W S

    1987-03-01

    Differential density gradient ultracentrifugation procedures, utilizing a vertical rotor, were developed for the preparative purification of very high density lipoproteins (VHDL, density greater than 1.21 g/ml). The VHDLs of several insect species were purified as follows. An initial density gradient ultracentrifugation step removed lipoproteins of lower density from the VHDL-fraction, which partially separated from the nonlipoproteins present in the infranatant. A complete separation was achieved by a second centrifugation step employing a modified gradient system. The use of a vertical rotor and specially designed discontinuous gradients allows a relatively fast, efficient, and economical isolation of the class of very high density lipoproteins. Similar gradient systems should be useful for the detection and purification of VHDLs from other sources. PMID:3578796

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

    DOEpatents

    Poppendiek, Heinz F.

    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.

  10. 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 ℓ2-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.

  11. The effect of water-soluble polymers on the microstructure and properties of freeze-cast alumina ceramics

    NASA Astrophysics Data System (ADS)

    Pekor, Christopher Michael

    Porous ceramics can be divided into three separate classes based on their pore size: microporous ceramics with pores less than 2 nm, mesoporous ceramics with pores in the range of 2--50 nm and macroporous ceramics with pores that are greater than 50 nm. In particular, macroporous ceramics are used in a variety of applications such as refractories, molten metal filtration, diesel particulate filters, heterogeneous catalyst supports and biomedical scaffolds. Freeze casting is a novel method used to create macroporous ceramics. In this method growing ice crystals act as a template for the pores and are solidified, often directionally, through a ceramic dispersion and removed from the green body through a freeze drying procedure. This method has attracted some attention over the past few years due to its relative simplicity, flexibility and environmental friendliness. On top of this freeze casting is capable of producing materials with high pore volume fractions, which is an advantage over processing by packing and necking of particles, where the pore volume fraction is typically less than 50%. Many of the basic processing variables that affect the freeze cast microstructure, such as the temperature gradient, interfacial velocity and solid loading of the dispersion have been well established in the literature. On the other hand, areas such as the effect of additives on the microstructure and mechanical properties have not been covered in great detail. In this study the concept of constitutional supercooling from basic solidification theory is used to explain the effects of two water-soluble polymers, polyethylene glycol and polyvinyl alcohol, on the microstructure of freeze cast alumina ceramics. In addition, changes in the observed microstructure will be related to experimentally determined values of permeability and compressive strength.

  12. Soil respiration and carbon loss relationship with temperature and land use conversion in freeze-thaw agricultural area.

    PubMed

    Ouyang, Wei; Lai, Xuehui; Li, Xia; Liu, Heying; Lin, Chunye; Hao, Fanghua

    2015-11-15

    Soil respiration (Rs) was hypothesized to have a special response pattern to soil temperature and land use conversion in the freeze-thaw area. The Rs differences of eight types of land use conversions during agricultural development were observed and the impacts of Rs on soil organic carbon (SOC) loss were assessed. The land use conversions during last three decades were categorized into eight types, and the 141 SOC sampling sites were grouped by conversion type. The typical soil sampling sites were subsequently selected for monitoring of soil temperature and Rs of each land use conversion types. The Rs correlations with temperature at difference depths and different conversion types were identified with statistical analysis. The empirical mean error model and the biophysical theoretical model with Arrhenius equation about the Rs sensitivity to temperature were both analyzed and shared the similar patterns. The temperature dependence of soil respiration (Q10) analysis further demonstrated that the averaged value of eight types of land use in this freeze-thaw agricultural area ranged from 1.15 to 1.73, which was lower than the other cold areas. The temperature dependence analysis demonstrated that the Rs in the top layer of natural land covers was more sensitive to temperature and experienced a large vertical difference. The natural land covers exhibited smaller Rs and the farmlands had the bigger value due to tillage practices. The positive relationships between SOC loss and Rs were identified, which demonstrated that Rs was the key chain for SOC loss during land use conversion. The spatial-vertical distributions of SOC concentration with the 1.5-km grid sampling showed that the more SOC loss in the farmland, which was coincided with the higher Rs in farmlands. The analysis of Rs dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area. The analysis of Rs dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area. PMID:26172588

  13. Vertical organic transistors

    NASA Astrophysics Data System (ADS)

    Lüssem, Björn; Günther, Alrun; Fischer, Axel; Kasemann, Daniel; Leo, Karl

    2015-11-01

    Organic switching devices such as field effect transistors (OFETs) are a key element of future flexible electronic devices. So far, however, a commercial breakthrough has not been achieved because these devices usually lack in switching speed (e.g. for logic applications) and current density (e.g. for display pixel driving). The limited performance is caused by a combination of comparatively low charge carrier mobilities and the large channel length caused by the need for low-cost structuring. Vertical Organic Transistors are a novel technology that has the potential to overcome these limitations of OFETs. Vertical Organic Transistors allow to scale the channel length of organic transistors into the 100 nm regime without cost intensive structuring techniques. Several different approaches have been proposed in literature, which show high output currents, low operation voltages, and comparatively high speed even without sub-μm structuring technologies. In this review, these different approaches are compared and recent progress is highlighted.

  14. Immersion freezing on mineral dust particles

    NASA Astrophysics Data System (ADS)

    Zolles, Tobias; Grothe, Hinrich; Pummer, Bernhard

    2013-04-01

    Mineral dust is considered to play a major role in ice cloud nucleation in the troposphere. More than 1.000 Tg of mineral dust are aerosolized from the ground every year, 1-10% of these reach the upper troposphere [1]. At an altitude of about 8 km ice residual particle analysis has shown that about 50% of all ice nuclei (IN) are mineral dust[2]. In principle, natural occurring dusts may either be IN-active themselves or are carriers of organic and/or biological IN. Up to now the ice nucleation, i.e. cloud glaciation, has not been quantized. However, different authors report a high IN-activity for many mineral dust samples, although a systematic comparison between different minerals is still missing. Therefore, we studied selected mineral dust samples which were characterized by X-ray diffraction, FTIR spectroscopy, and scanning electron microscopy before use. Oil immersion measurements were performed on the most common minerals, clay materials and volcanic ash. The median freezing temperatures range from -21°C up to homogenous freezing at 38°C. Even though quite a few dust samples show a reasonable high IN-activity, their median freezing temperatures are low compared to biological samples [3, 4]. Furthermore, heat treatment of the dusts was applied in order to decompose and to denaturize organic and/or biological surfactants. Finally, some dust samples had a high loss of activity and thus were subjects of further experiments. These mineral dust particles were suspended in water and after an incubation time were removed. In some cases the washing water had become IN-active, but lost its activity after enzymatic treatment. The observed high IN-activity can thus be explained by adsorbed biological materials. The results suggest that some mineral dusts are IN-active, and if it is not intrinsic they may even enhance IN-activity of organic and biological IN if these are adsorbed on the dust particle surface. A relatively high IN-activity of the pure mineral dusts was only observed in quartz, clays, and mixed natural dusts (ATD), which are mainly composed of SiO2 and clays. References. [1] C. S. Zender, R. L. Miller and I. Tegen, Eos Trans. AGU, 2004,85, 509. [2] K. A. Pratt, P. J. DeMott, J. R. French, Z. Wang, D. L. Westphal, A. J. Heymsfield, C. H. Twohy, A. J. Prenni, K. A. Prather, Nat. Geosci., 2009, 2, 397-400. [3] B. Pummer, H. Bauer, J. Bernardi, S. Bleicher and H. Grothe, Atmos. Chem. Phys., 2012, 12, 2541-2550. [4] V. T. J. Phillips, C. Andronache, B. Christner, C. E. Morris, D. C. Sands, A. Bansemer, A. Lauer, C. McNaughton and C. Seman, Biogeosciences, 2009, 6, 987-1014.

  15. Charge gradient microscopy

    PubMed Central

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

    2014-01-01

    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 μm. We envision that CGM can be used in high-speed ferroelectric domain imaging and piezoelectric energy-harvesting devices. PMID:24760831

  16. 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

  17. Freeze-Thaw Days in the Northeastern United States.

    NASA Astrophysics Data System (ADS)

    Schmidlin, Thomas W.; Dethier, Bernard E.; Eggleston, Keith L.

    1987-01-01

    A freeze-thaw day is defined as a weather observation day with a maximum temperature of 0°C or above and a minimum temperature of 2.2°C or below recorded in an instrument shelter 1.5 m above the ground. The 30 winter during 1950-80 are examined at 228 stations in nine northeastern states. Average annual freeze-thaw days range from over 90 at high elevations in the north to less than 50 along the Long Island and New Jersey shores and in the Philadelphia area. Freeze-thaw days are most common during midwinter months in the south but peak in March across inland sections. Freeze-thaw days are most numerous with average monthly temperatures between 2°C and 0°C and approach zero at monthly temperatures below 13°C and above 11°C.The number of freeze-thaw days with less than 7.5 cm of snow cover is about 95% of the total number along the southern coasts and less than 50% of the total in northern snowy climates. The air at 15 cm height experiences 13% more freeze-thaw days than the air at 150 cm, due to a larger daily temperature range. Hilltops experience fewer freeze-thaw days than valley bottoms.

  18. 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

  19. Water Relations of Pachysandra Leaves during Freezing and Thawing 1

    PubMed Central

    Zhu, Jian-Jun; Beck, Erwin

    1991-01-01

    The evergreen herb Pachysandra terminalis becomes moderately frost-hardy in winter. The water relations of its frost-hardy leaves were studied during a freeze-thaw cycle. Leaf water potentials, measured by psychrometry at subfreezing temperatures, were identical with those of ice, indicating equilibrium freezing. Microscopic observations showed extracellular freezing of tissue water. As evidenced by thermal analysis, the freezing process starts with the crystallization of a minor volume which was identified as apoplasmic water. The following long-lasting exotherm indicated slow export of water from the protoplasts driven by extracellular crystallization. In partially frozen leaves, the fractions of liquid water were measured at several subfreezing temperatures by nuclear magnetic resonance spectroscopy. They were consistently greater than those calculated from the osmotic potentials of cellular fluid, and the differences increased with decreasing temperature. About 50% of the differences could be abolished by freeze-killing of the leaf and was thus ascribed to the effect of a (negative) pressure reinforcing the osmotic potential. The persistent part of the differences may have reflected a matric component. At ?7C, the absolute values of both potentials were ?1.7 megapascals each. The water relations of Pachysandra leaves clearly indicate nonideal equilibrium freezing where negative pressures and matric potentials contribute to the leaf water potential and thus alleviate freeze-dehydration of the tissue. ImagesFigure 1Figure 5 PMID:16668501

  20. 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

  1. Hilly Surroundings (vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 360-degree view of the terrain surrounding NASA's Mars Exploration Rover Spirit was taken on the rover's 189th sol on Mars (July 15, 2004). It was assembled from images taken by the rover's navigation camera at a position referred to as Site 72, which is at the base of the 'West Spur' portion of the 'Columbia Hills.'' The view is presented in a vertical projection with geometrical seam correction.

  2. Vertical bloch line memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R. (Inventor); Stadler, Henry L. (Inventor); Wu, Jiin-chuan (Inventor)

    1995-01-01

    A new read gate design for the vertical Bloch line (VBL) memory is disclosed which offers larger operating margin than the existing read gate designs. In the existing read gate designs, a current is applied to all the stripes. The stripes that contain a VBL pair are chopped, while the stripes that do not contain a VBL pair are not chopped. The information is then detected by inspecting the presence or absence of the bubble. The margin of the chopping current amplitude is very small, and sometimes non-existent. A new method of reading Vertical Bloch Line memory is also disclosed. Instead of using the wall chirality to separate the two binary states, the spatial deflection of the stripe head is used. Also disclosed herein is a compact memory which uses vertical Bloch line (VBL) memory technology for providing data storage. A three-dimensional arrangement in the form of stacks of VBL memory layers is used to achieve high volumetric storage density. High data transfer rate is achieved by operating all the layers in parallel. Using Hall effect sensing, and optical sensing via the Faraday effect to access the data from within the three-dimensional packages, an even higher data transfer rate can be achieved due to parallel operation within each layer.

  3. 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.

  4. Laser scanning microscopy of broad freezing interfaces with applications to biological cells

    NASA Astrophysics Data System (ADS)

    Neils, Christopher Martin

    2000-09-01

    A new, vertical cryostage was used for microscopic observation of broad-front freezing in aqueous solutions. This cryostage complements traditional studies of cell behavior and interface morphology in cryobiology. Traditional systems directionally solidify thin samples perpendicular to the optical axis. Thin samples confer thermal and optical advantages for video brightfield microscopy. However, sample thickness can affect the interface morphology. In the new cryostage, ice propagates parallel to the microscope optical axis. The sample cup is 1 cm tall and 1.5 cm in diameter, with insulated sides and a nitrogen-cooled base to freeze the solution upward. The top of the solution is warmed passively through a cover glass or immersion objective. The freezing solutions contain dilute fluorescein dye, which is visible where it is concentrated by exclusion from the ice. The stage is mounted on a confocal laser-scanning microscope, and thermal control and image capture routines are centralized in a LabView user interface. Filtered water, physiological saline, 9.5% glycerol, and 10% glycerol with PBS were frozen at rates between -2°C/min and -10°C/min and sequential images at one plane were captured. Images distinctly revealed a lamellar interface but could not resolve 3-D morphology. The average lamellar spacing was quantified using image analysis. Physiological saline was frozen in flat glass capillary tubes with 0.05 to 0.4 mm path length, mounted vertically to observe internal ice in cross-section. Lamellae were randomly oriented with respect to the glass, suggesting caution when measuring dendrite spacing in a horizontal cryostage. No correlation between capillary size and lamellar spacing was noted. Cell monolayers and synthetic membranes were mounted horizontally to let a well-developed ice front approach the layer broadly. In transparent membranes, ice-membrane interaction was visible until ice grew over and obscured the membrane. The vertical cryostage improved our ability to observe ice lamellae in cross section. The broad phase front revealed dendrites' interaction with each other, rather than with the container walls. The arrangement permitted immersion objectives, which are normally avoided in cryomicroscopy because of heat transfer. The signal-to-noise ratio was too low for effective confocal microscopy, but laser-scanning microscopy provided good contrast compared to standard epi-fluorescence methods.

  5. Freeze Tape Casting of Functionally Graded Porous Ceramics

    NASA Technical Reports Server (NTRS)

    Sofie, Stephen W.

    2007-01-01

    Freeze tape casting is a means of making preforms of ceramic sheets that, upon subsequent completion of fabrication processing, can have anisotropic and/or functionally graded properties that notably include aligned and graded porosity. Freeze tape casting was developed to enable optimization of the microstructures of porous ceramic components for use as solid oxide electrodes in fuel cells: Through alignment and grading of pores, one can tailor surface areas and diffusion channels for flows of gas and liquid species involved in fuel-cell reactions. Freeze tape casting offers similar benefits for fabrication of optimally porous ceramics for use as catalysts, gas sensors, and filters.

  6. Freezing-induced deformation of biomaterials in cryomedicine

    NASA Astrophysics Data System (ADS)

    Ozcelikkale, Altug

    Cryomedicine utilizes low temperature treatments of biological proteins, cells and tissues for cryopreservation, materials processing and cryotherapy. Lack of proper understanding of cryodamage that occurs during these applications remains to be the primary bottleneck for development of successful tissue cryopreservation and cryosurgery procedures. An engineering approach based on a view of biological systems as functional biomaterials can help identify, predict and control the primary cryodamage mechanisms by developing an understanding of underlying freezing-induced biophysical processes. In particular, freezing constitutes the main structural/mechanical origin of cryodamage and results in significant deformation of biomaterials at multiple length scales. Understanding of these freezing-induced deformation processes and their effects on post-thaw biomaterial functionality is currently lacking but will be critical to engineer improved cryomedicine procedures. This dissertation addresses this problem by presenting three separate but related studies of freezing-induced deformation at multiple length scales including nanometer-scale protein fibrils, single cells and whole tissues. A combination of rigorous experimentation and computational modeling is used to characterize post-thaw biomaterial structure and properties, predict biomaterial behavior and assess its post-thaw biological functionality. Firstly, freezing-induced damage on hierarchical extracellular matrix structure of collagen is investigated at molecular, fibril and matrix levels. Results indicate to a specific kind of fibril damage due to freezing-induced expansion of intrafibrillar fluid. This is followed by a study of freezing-induced cell and tissue deformation coupled to osmotically driven cellular water transport. Computational and semi empirical modeling of these processes indicate that intracellular deformation of the cell during freezing is heterogeneous and can interfere with cellular water transport, thereby leading to previously unconsidered mechanisms of cell freezing response. In addition, cellular water transport is identified as the critical limiting factor on the amount of freezing-induced tissue deformation, particularly in native tissues with high cell densities. Finally, effects of cryopreservation on post-thaw biological functionality of collagen engineered tissue constructs is investigated where cell-matrix interactions during fibroblast migration are considered as the functional response. Simultaneous cell migration and extracellular matrix deformation are characterized. Results show diminished cell-matrix coupling by freeze/thaw accompanied by a subtle decrease in cell migration. A connection between these results and freezing-induced collagen fibril damage is also suggested. Overall, this dissertation provides new fundamental knowledge on cryodamage mechanisms and a collection of novel multi-purpose engineering tools that will open the way for rational design of cryomedicine technologies.

  7. Delayed freezing of water droplet on silver nanocolumnar thin film

    NASA Astrophysics Data System (ADS)

    Singh, Dhruv P.; Singh, Jitendra P.

    2013-06-01

    Silver nanocolumns were grown on Si substrate using glancing angle deposition method. Interestingly, the cold nanocolumnar surface was observed to make a delay of more than 62 s in freezing compared to the conventional silver thin film. The observed delay in freezing on silver nanocolumns is explainable in terms of reduction in effective liquid-solid interface area within the framework of Cassie-Baxter model. This study shows the possibility of using silver nanocolumnar films in ice free coatings and surfaces with tunable freezing properties.

  8. Nanoparticle manipulation by thermal gradient

    PubMed Central

    2012-01-01

    A method was proposed to manipulate nanoparticles through a thermal gradient. The motion of a fullerene molecule enclosed inside a (10, 10) carbon nanotube with a thermal gradient was studied by molecular dynamics simulations. We created a one-dimensional potential valley by imposing a symmetrical thermal gradient inside the nanotube. When the temperature gradient was large enough, the fullerene sank into the valley and became trapped. The escaping velocities of the fullerene were evaluated based on the relationship between thermal gradient and thermophoretic force. We then introduced a new way to manipulate the position of nanoparticles by translating the position of thermostats with desirable thermal gradients. Compared to nanomanipulation using a scanning tunneling microscope or an atomic force microscope, our method for nanomanipulation has a great advantage by not requiring a direct contact between the probe and the object. PMID:22364240

  9. Amplitude Manipulation Evokes Upper Limb Freezing during Handwriting in Patients with Parkinson’s Disease with Freezing of Gait

    PubMed Central

    Heremans, Elke; Nackaerts, Evelien; Vervoort, Griet; Vercruysse, Sarah; Broeder, Sanne; Strouwen, Carolien; Swinnen, Stephan P.; Nieuwboer, Alice

    2015-01-01

    Background Recent studies show that besides freezing of gait (FOG), many people with Parkinson’s disease (PD) also suffer from freezing in the upper limbs (FOUL). Up to now, it is unclear which task constraints provoke and explain upper limb freezing. Objective To investigate whether upper limb freezing and other kinematic abnormalities during writing are provoked by (i) gradual changes in amplitude or by (ii) sustained amplitude generation in patients with and without freezing of gait. Methods Thirty-four patients with PD, including 17 with and 17 without FOG, performed a writing task on a touch-sensitive writing tablet requiring writing at constant small and large size as well as writing at gradually increasing and decreasing size. Patients of both groups were matched for disease severity, tested while ‘on’ medication and compared to healthy age-matched controls. Results Fifty upper limb freezing episodes were detected in 10 patients, including 8 with and 2 without FOG. The majority of the episodes occurred when participants had to write at small or gradually decreasing size. The occurrence of FOUL and the number of FOUL episodes per patient significantly correlated with the occurrence and severity of FOG. Patients with FOUL also showed a significantly smaller amplitude in the writing parts outside the freezing episodes. Conclusions Corroborating findings of gait research, the current study supports a core problem in amplitude control underlying FOUL, both in maintaining as well as in flexibly adapting the cycle size. PMID:26580556

  10. Comparison of the depth of tissue necrosis between double-freeze and single-freeze nitrous oxide-based cryotherapy

    PubMed Central

    Adepiti, Akinfolarin Clement; Ajenifuja, Olusegun Kayode; Fadahunsi, Oluwaseyi Olatunji; Osasan, Stephen Adebayo; Pelemo, Olumuyiwa Eyitayo; Loto, Morebishe Olabisi

    2016-01-01

    Background: Cryotherapy is one the methods of treating cervical premalignant lesions. It is particularly suitable for low-resource countries because of it is relative cheaper, has low cost of maintenance, ease of use and that does not require electricity which is in short supply in many rural areas of developing countries where the incidence and mortality from cervical cancer is very high. In this study we compared single and double freezing on the cervices of women admitted for hysterectomy for benign conditions using Nitrous-based cryotherapy. Materials and Methods: Patients admitted for elective hysterectomy for benign gynaecological conditions were randomized into two arms. The first group had single freeze cryotherapy while the second arm received double freeze cryotherapy. The cervices were examined 24 hours later to determine the depth of tissue necrosis. Results: In this comparative study, the depth of tissue necrosis was deeper with double freeze compared with single freeze. Also in both arms, the depth of necrosis was deeper on anterior lips than on posterior lips of the cervix. Conclusion: Double freeze technique achieve more depth of tissue necrosis than single-freeze on both anterior and posterior lips of the cervix. PMID:27185971

  11. 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

  12. Freezing water in no-man's land.

    PubMed

    Manka, Alexandra; Pathak, Harshad; Tanimura, Shinobu; Wölk, Judith; Strey, Reinhard; Wyslouzil, Barbara E

    2012-04-01

    We report homogeneous ice nucleation rates between 202 K and 215 K, thereby reducing the measurement gap that previously existed between 203 K and 228 K. These temperatures are significantly below the homogenous freezing limit, T(H)≈ 235 K for bulk water, and well within no-man's land. The ice nucleation rates are determined by characterizing nanodroplets with radii between 3.2 and 5.8 nm produced in a supersonic nozzle using three techniques: (1) pressure trace measurements to determine the properties of the flow as well as the temperature and velocity of the droplets, (2) small angle X-ray scattering (SAXS) to measure the size and number density of the droplets, and (3) Fourier Transform Infrared (FTIR) spectroscopy to follow the liquid to solid phase transition. Assuming that nucleation occurs throughout the droplet volume, the measured ice nucleation rates J(ice,V) are on the order of 10(23) cm(-3) s(-1), and agree well with published values near 203 K. PMID:22354018

  13. 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.

  14. 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

  15. Estimating collision efficiencies from contact freezing experiments

    NASA Astrophysics Data System (ADS)

    Nagare, B.; Marcolli, C.; Stetzer, O.; Lohmann, U.

    2015-04-01

    Interactions of atmospheric aerosols with clouds influence cloud properties and modify the aerosol life cycle. Aerosol particles act as cloud condensation nuclei and ice nucleating particles or become incorporated into cloud droplets by scavenging. For an accurate description of aerosol scavenging and ice nucleation in contact mode, collision efficiency between droplets and aerosol particles needs to be known. This study derives the collision rate from experimental contact freezing data obtained with the ETH Collision Ice Nucleation Chamber CLINCH. Freely falling 80 μm water droplets are exposed to an aerosol consisting of 200 nm diameter silver iodide particles of concentrations from 500-5000 cm-3, which act as ice nucleating particles in contact mode. The chamber is kept at ice saturation in the temperature range from 236-261 K leading to slow evaporation of water droplets giving rise to thermophoresis and diffusiophoresis. Droplets and particles bear charges inducing electrophoresis. The experimentally derived collision efficiency of 0.13 is around one order of magnitude higher than theoretical formulations which include Brownian diffusion, impaction, interception, thermophoretic, diffusiophoretic and electric forces. This discrepancy is most probably due to uncertainties and inaccuracies in the description of thermophoretic and diffusiophoretic processes acting together. This is to the authors knowledge the first dataset of collision efficiencies acquired below 273 K. More such experiments with different droplet and particle diameters are needed to improve our understanding of collision processes acting together.

  16. Stochastic flux freezing and magnetic dynamo.

    PubMed

    Eyink, Gregory L

    2011-05-01

    Magnetic flux conservation in turbulent plasmas at high magnetic Reynolds numbers is argued neither to hold in the conventional sense nor to be entirely broken, but instead to be valid in a statistical sense associated to the "spontaneous stochasticity" of Lagrangian particle trajectories. The latter phenomenon is due to the explosive separation of particles undergoing turbulent Richardson diffusion, which leads to a breakdown of Laplacian determinism for classical dynamics. Empirical evidence is presented for spontaneous stochasticity, including numerical results. A Lagrangian path-integral approach is then exploited to establish stochastic flux freezing for resistive hydromagnetic equations and to argue, based on the properties of Richardson diffusion, that flux conservation must remain stochastic at infinite magnetic Reynolds number. An important application of these results is the kinematic, fluctuation dynamo in nonhelical, incompressible turbulence at magnetic Prandtl number (Pr(m)) equal to unity. Numerical results on the Lagrangian dynamo mechanisms by a stochastic particle method demonstrate a strong similarity between the Pr(m)=1 and 0 dynamos. Stochasticity of field-line motion is an essential ingredient of both. Finally, some consequences for nonlinear magnetohydrodynamic turbulence, dynamo, and reconnection are briefly considered. PMID:21728673

  17. 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

  18. Stochastic flux freezing and magnetic dynamo

    SciTech Connect

    Eyink, Gregory L.

    2011-05-15

    Magnetic flux conservation in turbulent plasmas at high magnetic Reynolds numbers is argued neither to hold in the conventional sense nor to be entirely broken, but instead to be valid in a statistical sense associated to the ''spontaneous stochasticity'' of Lagrangian particle trajectories. The latter phenomenon is due to the explosive separation of particles undergoing turbulent Richardson diffusion, which leads to a breakdown of Laplacian determinism for classical dynamics. Empirical evidence is presented for spontaneous stochasticity, including numerical results. A Lagrangian path-integral approach is then exploited to establish stochastic flux freezing for resistive hydromagnetic equations and to argue, based on the properties of Richardson diffusion, that flux conservation must remain stochastic at infinite magnetic Reynolds number. An important application of these results is the kinematic, fluctuation dynamo in nonhelical, incompressible turbulence at magnetic Prandtl number (Pr{sub m}) equal to unity. Numerical results on the Lagrangian dynamo mechanisms by a stochastic particle method demonstrate a strong similarity between the Pr{sub m}=1 and 0 dynamos. Stochasticity of field-line motion is an essential ingredient of both. Finally, some consequences for nonlinear magnetohydrodynamic turbulence, dynamo, and reconnection are briefly considered.

  19. Effect of geometrical frustration on inverse freezing

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Morais, C. V.; Zimmer, F. M.

    2016-01-01

    The interplay between geometrical frustration (GF) and inverse freezing (IF) is studied within a cluster approach. The model considers first-neighbor (J1) and second-neighbor (J2) intracluster antiferromagnetic interactions between Ising spins on a checkerboard lattice and long-range disordered couplings (J ) among clusters. We obtain phase diagrams of temperature versus J1/J in two cases: the absence of J2 interaction and the isotropic limit J2=J1 , where GF takes place. An IF reentrant transition from the spin-glass (SG) to paramagnetic (PM) phase is found for a certain range of J1/J in both cases. The J1 interaction leads to a SG state with high entropy at the same time that can introduce a low-entropy PM phase. In addition, it is observed that the cluster size plays an important role. The GF increases the PM phase entropy, but larger clusters can give an entropic advantage for the SG phase that favors IF. Therefore, our results suggest that disordered systems with antiferromagnetic clusters can exhibit an IF transition even in the presence of GF.

  20. 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

  1. Vertical dynamical transport of mesospheric constituents by dissipating gravity waves

    NASA Astrophysics Data System (ADS)

    Liu, Alan Z.; Gardner, Chester S.

    2004-02-01

    Over 400h of Na wind/temperature lidar observations, obtained at the Starfire Optical Range, NM, are used to study the vertical dynamical transport of Na in the mesopause region between 85 and 100km. Dynamical transport occurs when dissipating, non-breaking gravity waves impart a net vertical displacement in atmospheric constituents as they propagate through a region. We show that the vertical constituent flux can be related in a simple way to the vertical heat flux. Breaking gravity waves also contribute to eddy transport by generating turbulence. Because eddy transport is a mixing process, it only occurs in the presence of a gradient in the concentration profile of the constituent, while dynamical transport can be sustained even in the absence of such a gradient. The dynamical Na flux is compared with the predicted eddy flux. The maximum downward dynamical flux of Na is -280m/scm3 at 88km. The maximum downward eddy flux is -160m/scm3 at the same altitude assuming the diffusion coefficient is 200m2/s. The observational results are consistent with theoretical predictions below 93km and show that dynamical transport often exceeds the vertical transport associated with eddy diffusion. The theoretical models are used to predict the dynamical and eddy fluxes of atomic oxygen and show that for this constituent, dynamical transport is also a significant transport mechanism.

  2. The structure of the cytoplasmic matrix preserved by freeze-drying and freeze-substitution.

    PubMed

    Porter, K R; Anderson, K L

    1982-11-01

    This paper reports a study of the cytoplasmic matrix in whole cultured cells examined by high voltage electron microscopy. In order to acquaint ourselves with the influence of preparation procedures on the morphology depicted, PtK2 cells were prepared for examination by first freezing in propane at -185 degrees C and then drying while maintained at -95 degrees C. Other cells of the same type were first fixed with glutaraldehyde and OsO4 and then frozen dried. Others were prepared by freeze-substitution and eventually dried by the critical-point method from CO2. And finally, some were preserved by conventional techniques of glutaraldehyde and OsO4 followed by dehydration in alcohol and critical-point drying. The observations are presented in stereo images. The morphologies after these various procedures are quite similar. All show the characteristic three-dimensional lattice or meshwork of slender filaments called microtrabeculae. In cells rapidly frozen and then dried from the frozen state, there is less evidence of shrinkage and probable change in the trabecular structure than in cells first fixed with glutaraldehyde and then frozen dried. The differences we relate to the demonstrable failure of glutaraldehyde to penetrate the cell quickly and fix instantly any component that is in active motion. Other differences that can be observed between all four types of preparation are not recognizably striking and are thought to reflect as much as anything morphological diversity in the original cells. In some instances, the amorphous ice of the initial freezing at -185 degrees C was allowed to crystallize at -80 degrees C. The small crystals that form push aside the microtrabeculae and leave obvious imprints on the structure. The essential message from these experiments is that the cytomatrix is structured. PMID:6818029

  3. 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

  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. Gradient boosting machines, a tutorial

    PubMed Central

    Natekin, Alexey; Knoll, Alois

    2013-01-01

    Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods with a strong focus on machine learning aspects of modeling. A theoretical information is complemented with descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. Three practical examples of gradient boosting applications are presented and comprehensively analyzed. PMID:24409142

  6. Strength of depth effects induced by three types of vertical disparity.

    PubMed

    Berends, E M; Erkelens, C J

    2001-01-01

    The goal of the present study is to compare the strengths of depth effects induced by different types of vertical disparity. We use a nulling task, in which the depth effects induced by vertical disparity are nulled by horizontal disparity. The advantage of this method is that it prevents cue conflicts from arising between disparity and other depth cues. The ratios between horizontal and vertical disparity that evoke the percept of a fronto-parallel stimulus vary per type of vertical disparity. The ratios determined for vertical scale and vertical quadratic mix (vertical scale with a horizontal gradient) vary strongly across subjects. The ratios for vertical shear are constant, since all subjects needed the same amount of horizontal and vertical shear to perceive a fronto-parallel plane. In these experiments, one conflict cannot be avoided, namely the conflict between vertical disparity and oculomotor signals. This conflict may cause differential weighting of vertical disparity and oculomotor signals, which could explain the individual differences. The different ratios for different types of vertical disparity suggest that weighting is specific for each type of vertical disparity and the associated oculomotor signal. PMID:11163614

  7. Improvement of parameters of freezing medium and freezing protocol for bull sperm using two osmotic supports.

    PubMed

    Chaveiro, A; Machado, L; Frijters, A; Engel, B; Woelders, H

    2006-06-01

    The aim of this study was to improve the freezing protocol of bull sperm, by investigating the influence on sperm viability after freeze/thawing of different freezing medium components, as well as the effect of cooling rates in the different stages of the cooling protocol, in single factor experiments. The experimental variables were: (1) salt-based versus a sugar-based medium (Tris versus sucrose); (2) glycerol concentration; (3) detergent (Equex) concentration; (4) presence of bicarbonate; (5) rate of cooling from 22 degrees C to holding temperature (CR1); (6) holding temperature (HT); (7) rate of cooling from holding temperature to -6 degrees C (CR2); (8) rate of cooling from -10 to -100 degrees C (CR3). All experiments were performed using five bulls per experiment (three ejaculates per bull). Sperm motility after freezing and thawing was assessed by CASA system, and sperm membrane integrity was assessed by flow cytometry. Sucrose-based medium did not offer a clear significant benefit compared to Tris medium. The concentration of Equex that gave the best results in Tris-based media group and sucrose-based media group was in a range between 2-7 and 4-7 g/l, respectively. In both media groups, a glycerol concentration of 800 mM was the best in any post-thaw viability parameters. In the Tris media group, the presence of bicarbonate had a negative effect on sperm viability. CR1 and CR2 had no significant effect on any of the post-thaw sperm viability parameters, but a CR1=0.2 degrees C/min and CR2=4 degrees C/min appeared to give better results in both media. The holding temperature (HT) that gave the best results was found to be in the range of 5-9 degrees C. There was a significant disadvantage of using a low CR3 of 10 degrees C/min, while 150 degrees C/min appeared to be the best cooling rate for either medium. PMID:16310842

  8. Tight junction regulates epidermal calcium ion gradient and differentiation

    SciTech Connect

    Kurasawa, Masumi; Maeda, Tetsuo; Oba, Ai; Yamamoto, Takuya; Sasaki, Hiroyuki; The Center for Advanced Medical Engineering and Infomatics, Osaka University, Osaka 565-0871

    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.

  9. Atmospheric gradients from very long baseline interferometry observations

    NASA Technical Reports Server (NTRS)

    Macmillan, D. S.

    1995-01-01

    Azimuthal asymmetries in the atmospheric refractive index can lead to errors in estimated vertical and horizontal station coordinates. Daily average gradient effects can be as large as 50 mm of delay at a 7 deg elevation. To model gradients, the constrained estimation of gradient paramters was added to the standard VLBI solution procedure. Here the analysis of two sets of data is summarized: the set of all geodetic VLBI experiments from 1990-1993 and a series of 12 state-of-the-art R&D experiments run on consecutive days in January 1994. In both cases, when the gradient parameters are estimated, the overall fit of the geodetic solution is improved at greater than the 99% confidence level. Repeatabilities of baseline lengths ranging up to 11,000 km are improved by 1 to 8 mm in a root-sum-square sense. This varies from about 20% to 40% of the total baseline length scatter without gradient modeling for the 1990-1993 series and 40% to 50% for the January series. Gradients estimated independently for each day as a piecewise linear function are mostly continuous from day to day within their formal uncertainties.

  10. Amine-phenyl multi-component gradient stationary phases.

    PubMed

    Dewoolkar, Veeren C; Kannan, Balamurali; Ashraf, Kayesh M; Higgins, Daniel A; Collinson, Maryanne M

    2015-09-01

    Continuous multi-component gradients in amine and phenyl groups were fabricated using controlled rate infusion (CRI). Solutions prepared from either 3-aminopropyltriethoxysilane (APTEOS) or phenyltrimethoxysilane (PTMOS) were infused, in a sequential fashion, at a controlled rate into an empty graduated cylinder housing a vertically aligned thin layer chromatography (TLC) plate. The hydrolyzed precursors reacted with an abundance of silanol (SiOH) groups on the TLC plates, covalently attaching the functionalized silane to its surface. The extent of modification by phenyl and amine was determined by the kinetics of each reaction and the exposure time at each point along the TLC plate. The local concentrations of phenyl and amine were measured using diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy, respectively. The profile of the multi-component gradients strongly depended on the order of infusion, the direction of the gradient and the presence of available surface silanol groups. A slightly higher amount of phenyl can be deposited on the TLC plate by first modifying its surface with amine groups as they serve as a catalyst, enhancing condensation. Separation of water- and fat-soluble vitamins and the control of retention factors were demonstrated on the multi-component gradient TLC plates. Uniformly modified and single-component TLC plates gave different separations compared to the multi-component gradient plates. The retention factors of the individual vitamins depended on the order of surface modification, the spotting end, and whether the multi-component gradients align or oppose each other. PMID:26255112

  11. Computation of the gravity field and its gradient: Some applications

    NASA Astrophysics Data System (ADS)

    Dubey, C. P.; Tiwari, V. M.

    2016-03-01

    New measuring instruments of Earth's gravity gradient tensors (GGT) have offered a fresh impetus to gravimetry and its application in subsurface exploration. Several efforts have been made to provide a thorough understanding of the complex properties of the gravity gradient tensor and its mathematical formulations to compute GGT. However, there is not much open source software available. Understanding of the tensor properties leads to important guidelines in the development of real three dimensional geological models. We present a MATLAB computational algorithm to calculate the gravity field and full gravity gradient tensor for an undulated surface followed by regular geometries like an infinite horizontal slab, a vertical sheet, a solid sphere, a vertical cylinder, a normal fault model and a rectangular lamina or conglomerations of such bodies and the results are compared with responses using professional software based on different computational schemes. Real subsurface geometries of complex geological structures of interest are approximated through arrangements of vertical rectangular laminas. The geological application of this algorithm is demonstrated over a horst-type structure of Oklahoma Aulacogen, USA and Vredefort Dome, South Africa, where measured GGT data are available.

  12. Freeze shoe sampler for the collection of hyporheic zone sediments and porewater.

    PubMed

    Bianchin, M; Smith, L; Beckie, R

    2015-01-01

    The Starr and Ingleton (1992) drive point piston sampler (DPPS) design was modified by fitting it with a Murphy and Herkelrath (1996) type sample-freezing drive shoe (SFDS), which uses liquid carbon dioxide as a cryogen. Liquid carbon dioxide was used to freeze sediments in the lower 0.1 m of the core and the drive-point piston sealed the core at the top preserving the reductive-oxidation (redox) sensitive sediments from the atmosphere and maintaining natural stratigraphy. The use of nitrogen gas to provide positive pressure on the gas system blocked the ingress of water which froze on contact with the cryogen thus blocking the gas lines with ice. With this adaptation to the gas system cores could be collected at greater depths beneath the static water level. This tool was used to collect intact saturated sediment cores from the hyporheic zone of the tidally influenced Fraser River in Vancouver, British Columbia, Canada where steep geochemical and microbial gradients develop within the interface between discharging anaerobic groundwater and recharging aerobic river water. In total, 25 cores driven through a 1.5 m sampling interval were collected from the river bed with a mean core recovery of 75%. The ability to deploy this method from a fishing vessel makes the tool more cost effective than traditional marine-based drilling operations which often use barges, tug boats, and drilling rigs. PMID:24825508

  13. Gradient forests: calculating importance gradients on physical predictors.

    PubMed

    Ellis, Nick; Smith, Stephen J; Pitcher, C Roland

    2012-01-01

    In ecological analyses of species and community distributions there is interest in the nature of their responses to environmental gradients and in identifying the most important environmental variables, which may be used for predicting patterns of biodiversity. Methods such as random forests already exist to assess predictor importance for individual species and to indicate where along gradients abundance changes. However, there is a need to extend these methods to whole assemblages, to establish where along the range of these gradients the important compositional changes occur, and to identify any important thresholds or change points. We develop such a method, called "gradient forest," which is an extension of the random forest approach. By synthesizing the cross-validated R2 and accuracy importance measures from univariate random forest analyses across multiple species, sampling devices, and surveys, gradient forest obtains a monotonic function of each predictor that represents the compositional turnover along the gradient of the predictor. When applied to a synthetic data set, the method correctly identified the important predictors and delineated where the compositional change points occurred along these gradients. Application of gradient forest to a real data set from part of the Great Barrier Reef identified mud fraction of the sediment as the most important predictor, with highest compositional turnover occurring at mud fraction values around 25%, and provided similar information for other predictors. Such refined information allows for more accurate capturing of biodiversity patterns for the purposes of bioregionalization, delineation of protected areas, or designing of biodiversity surveys. PMID:22486096

  14. An approximation for homogeneous freezing temperature of water droplets

    NASA Astrophysics Data System (ADS)

    O, K.-T.; Wood, R.

    2015-11-01

    In this work, based on the well-known formulae of classical nucleation theory (CNT), the temperature TNc = 1 at which the mean number of critical embryos inside a droplet is unity is derived and proposed as a new approximation for homogeneous freezing temperature of water droplets. Without consideration of time dependence and stochastic nature of the ice nucleation process, the approximation TNc = 1 is able to reproduce the dependence of homogeneous freezing temperature on drop size and water activity of aqueous drops observed in a wide range of experimental studies. We use the TNc = 1 approximation to argue that the distribution of homogeneous freezing temperatures observed in the experiments may largely be explained by the spread in the size distribution of droplets used in the particular experiment. It thus appears that this approximation is useful for predicting homogeneous freezing temperatures of water droplets in the atmosphere.

  15. 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

  16. Challenging endeavour for preservation of freeze-dried mammalian spermatozoa.

    PubMed

    Hochi, Shinichi; Abdalla, Hany; Hara, Hiromasa; Hirabayashi, Masumi

    2011-10-01

    Freeze-drying (lyophilization) has been proposed as an alternative method for sperm preservation to overcome the disadvantages of the current cryopreservation method such as the high maintenance cost of frozen stocks, the problems associated with transportation of frozen materials and the potential risk of total loss of the frozen stock. Since freeze-dried spermatozoa after rehydration lose their motility, which is an essential requirement to complete physiological fertilization, a relatively difficult microinsemination technique must be applied to rehydrated spermatozoa. Theoretically, it has been supposed that freeze-dried spermatozoa could maintain their functions and abilities to interact with the oocyte cytoplasm after prolonged storage at refrigerator temperature. However, sufficient yield of transferable blastocysts and production of live offspring derived from freeze-dried sperm samples are still subjects to be challenged and overcome in large domestic species. PMID:22052044

  17. Atmospheric science: Sea-spray particles cause freezing in clouds

    NASA Astrophysics Data System (ADS)

    Russell, Lynn M.

    2015-09-01

    Ice clouds in marine regions at high latitudes might form in warmer and drier air than was previously believed because of freezing induced by airborne particles that contain organic materials from ocean surface waters. See Letter p.234

  18. Supercooling in overwintering azalea flower buds: additional freezing parameters.

    PubMed

    George, M F; Burke, M J

    1977-02-01

    Results of calorimetric, nuclear magnetic resonance, and low temperature light microscopic studies on supercooled azalea (Rhododendron kosterianum, Schneid.) floral primordia are reported. Heat release during freezing of the supercooled floral primordia is in the range predicted for supercooled pure water. Spin-lattice and spin-spin relaxation times measured by pulsed nuclear magnetic resonance spectroscopy decreased after freezing, suggesting that a redistribution of tissue water is associated with injury to the floral primordium. The calorimetric and low temperature microscopy studies showed no detectable ice formation in floral primordia until the major freezing event at low temperature. No resistance to ice growth is found to exist in the primordium tissues, indicating that a freezing barrier or thermodynamic equilibrium exists between the unfrozen primordium and other flower bud parts which contain ice at subfreezing temperatures. PMID:16659842

  19. ARCTIC FOUNDATIONS, INC. FREEZE BARRIER SYSTEM - SITE TECHNOLOGY CAPSULE

    EPA Science Inventory

    Arctic Foundations, Inc. (AFI), of Anchorage, Alaska has developed a freeze barrier technology designed to prevent the migration of contaminants in groundwater by completely isolating contaminant source areas until appropriate remediation techniques can be applied. With this tec...

  20. ARCTIC FOUNDATIONS, INC. FREEZE BARRIER TECHNOLOGY; INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    Arctic Foundations, Inc. (AFI), of Anchorage, Alaska has developed a freeze barrier technology designed to prevent the migration of contaminants in groundwater by completely isolating contaminant source areas until appropriate remediation techniques can be applied. With this tech...

  1. Normal freezing of ideal ternary systems of the pseudobinary type

    NASA Technical Reports Server (NTRS)

    Li, C. H.

    1972-01-01

    Perfect liquid mixing but no solid diffusion is assumed in normal freezing. In addition, the molar compositions of the freezing solid and remaining liquid, respectively, follow the solidus and liquidus curves of the constitutional diagram. For the linear case, in which both the liquidus and solidus are perfectly straight lines, the normal freezing equation giving the fraction solidified at each melt temperature and the solute concentration profile in the frozen solid was determined as early as 1902, and has since been repeatedly published. Corresponding equations for quadratic, cubic or higher-degree liquidus and solidus lines have also been obtained. The equation of normal freezing for ideal ternary liquid solutions solidified into ideal solid solutions of the pseudobinary type is given. Sample computations with the use of this new equation were made and are given for the Ga-Al-As system.

  2. 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

  3. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF... dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated cranberries or other cranberry products by any commercial process....

  4. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF... dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated cranberries or other cranberry products by any commercial process....

  5. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF... dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated cranberries or other cranberry products by any commercial process....

  6. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF... dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated cranberries or other cranberry products by any commercial process....

  7. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF... dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated cranberries or other cranberry products by any commercial process....

  8. Multiphoton imaging of biological samples during freezing and heating

    NASA Astrophysics Data System (ADS)

    Breunig, H. G.; Uchugonova, A.; König, K.

    2014-02-01

    We applied multiphoton microscopic imaging to observe freezing and heating effects in plant- and animal cell samples. The experimental setups consisted of a multiphoton imaging system and a heating and cooling stage which allows for precise temperature control from liquid nitrogen temperature (-196°C 77 K) up to +600°C (873 K) with heating/freezing rates between 0.01 K/min and 150 K/min. Two multiphoton imaging systems were used: a system based on a modified optical microscope and a flexible mobile system. To illustrate the imaging capabilities, plant leafs as well as animal cells were microscopically imaged in vivo during freezing based on autofluorescence lifetime and intensity of intrinsic molecules. The measurements illustrate the usefulness of multiphoton imaging to investigate freezing effects on animal and plant cells.

  9. 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.

  10. [Freezing of gait is a symptom of Parkinson disease].

    PubMed

    Mezzarobba, Susanna; Bandel, Dora; Capus, Livio; Torre, Paola; Moretti, Rita

    2004-09-01

    One could distinguish between "off freezing", which is a symptom tightly bound to L-dopa dosage and titration, and is clinically bound to wearing off, and, on the contrary, "on freezing" which does not respond to therapy modifications or to different drug's titration. On freezing seems to be related to frontal-basal ganglia-pontine neural pathway disruption. This neural disruption may be related with altered perception of extra and peri-personal space which are two major problems of these patients. We demonstrate in a group of patients with "on freezing" evident defect of attention, focus capability, of set-shifting properties, and of alteration in body/space relationship. We discuss on results obtained by specific training of physiotherapy with an review on literature. PMID:15473380

  11. [Freezing of gait is a symptom of Parkinson disease].

    TOXLINE Toxicology Bibliographic Information

    Mezzarobba S; Bandel D; Capus L; Torre P; Moretti R

    2004-09-01

    One could distinguish between "off freezing", which is a symptom tightly bound to L-dopa dosage and titration, and is clinically bound to wearing off, and, on the contrary, "on freezing" which does not respond to therapy modifications or to different drug's titration. On freezing seems to be related to frontal-basal ganglia-pontine neural pathway disruption. This neural disruption may be related with altered perception of extra and peri-personal space which are two major problems of these patients. We demonstrate in a group of patients with "on freezing" evident defect of attention, focus capability, of set-shifting properties, and of alteration in body/space relationship. We discuss on results obtained by specific training of physiotherapy with an review on literature.

  12. Long-term storage of bionanodevices by freezing and lyophilization.

    PubMed

    Seetharam, Raviraja; Wada, Yuuko; Ramachandran, Sujatha; Hess, Henry; Satir, Peter

    2006-09-01

    Successful long-term storage of a "smart dust" device integrating biomolecular motors and complex protein assemblies has been demonstrated using freezing or lyophilization, which implies that fabrication and application can be separated even for complex bionanodevices. PMID:16929405

  13. Optoacoustic laser monitoring of cooling and freezing of tissues

    SciTech Connect

    Larin, Kirill V; Larina, I V; Motamedi, M; Esenaliev, R O

    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)

  14. 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

  15. Universal Public Argument and the Failure of Nuclear Freeze.

    ERIC Educational Resources Information Center

    King, Andrew; Petress, Kenneth

    1990-01-01

    Examines the strategy of universalization during the nuclear freeze movement of 1981-82 by drawing upon the insights of Celeste Condit and William Bailey. Identifies strengths and weaknesses of the Condit/Bailey concepts and suggests modifications. (KEH)

  16. Optical coherence tomography-based freeze-drying microscopy

    PubMed Central

    Mujat, Mircea; Greco, Kristyn; Galbally-Kinney, Kristin L.; Hammer, Daniel X.; Ferguson, R. Daniel; Iftimia, Nicusor; Mulhall, Phillip; Sharma, Puneet; Pikal, Michael J.; Kessler, William J.

    2011-01-01

    A new type of freeze-drying microscope based upon time-domain optical coherence tomography is presented here (OCT-FDM). The microscope allows for real-time, in situ 3D imaging of pharmaceutical formulations in vials relevant for manufacturing processes with a lateral resolution of <7 μm and an axial resolution of <5 μm. Correlation of volumetric structural imaging with product temperature measured during the freeze-drying cycle allowed investigation of structural changes in the product and determination of the temperature at which the freeze-dried cake collapses. This critical temperature is the most important parameter in designing freeze-drying processes of pharmaceutical products. PMID:22254168

  17. Advances in process chromatography gradient elution using binary linear gradients.

    PubMed

    Natarajan, V; Purdom, G

    2001-01-26

    A number of chromatography techniques utilize mobile phase gradients with changing buffer concentration to effect separation. At process scale the majority of gradients are stepwise or isocratic. There are a number of instances where process performance or economics indicate that linear gradients would deliver better theoretical performance. However, to date this process advantage has not been implemented due to concerns about the accuracy, reliability or reproducibility of equipment used to produce linear changes in gradient composition. In this manuscript, recent developments in simple feedforward control and data from the resultant process-scale performance are presented. Information is provided on the practical heuristics underlying the control strategy. The data presented in this paper illustrate how the feedforward control strategy has been implemented on a commercial system to achieve better than +/- 2% accuracy of process-scale linear gradients. PMID:11218118

  18. The vertical motion simulator

    NASA Technical Reports Server (NTRS)

    Hosein, Todd

    1988-01-01

    Today's flight simulators, such as NASA's multimillion dollar Vertical Motion Simulator (VMS), recreate an authentic aircraft environment, and reproduce the sensations of flight by mechanically generating true physical events. In addition to their application as a training tool for pilots, simulators have become essential in the design, construction, and testing of new aircraft. Simulators allow engineers to study an aircraft's flight performance and characteristics without the cost or risk of an actual test flight. Because of their practicality, simulators will become more and more important in the development and design of new, safer aircraft.

  19. 'Endurance' Untouched (vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This navigation camera mosaic, created from images taken by NASA's Mars Exploration Rover Opportunity on sols 115 and 116 (May 21 and 22, 2004) provides a dramatic view of 'Endurance Crater.' The rover engineering team carefully plotted the safest path into the football field-sized crater, eventually easing the rover down the slopes around sol 130 (June 12, 2004). To the upper left of the crater sits the rover's protective heatshield, which sheltered Opportunity as it passed through the martian atmosphere. The 360-degree view is presented in a vertical projection, with geometric and radiometric seam correction.

  20. Gradients in analyzability.

    PubMed

    Grotstein, J S

    A discussion of "Some Communicative Properties of the Bipersonal Field" by Robert Langs, M.D. In response to Dr. Langs' delineation of the bipersonal field concept and his clinical elaboration of a triad of disorders which are graded into classifications of descending analyzability: Types A,B, and C fields. I confirm his thesis and endeavor to demonstrate some underlying foundations of his categorical assumptions, namely the conceptions of projective identification, of the intactness of the background object of primary identification, the conception of a dual-track theory of infantile development in order to delineate the parallel between the separated self and the continuation of primary identification, and the postulation of manic and schizoid types of narcissistic character disorders (Types B and C respectively). All of these conceptions are vicissitudes of the varying ways in which patients confront the depressive position of separation-individuation with rapprochement and, thereby, conform to a gradient in which symbolization interpretations can be utilized in analytic treatment. PMID:738806