WorldWideScience

Sample records for surface freezing transitions

  1. Surface freezing of n-octane nanodroplets

    Science.gov (United States)

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

    2013-05-01

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

  2. Multiple Glass Transitions and Freezing Events of Aqueous Citric Acid

    Science.gov (United States)

    2014-01-01

    Calorimetric and optical cryo-microscope measurements of 10–64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid–glass transitions upon cooling and from one to six liquid–glass and reverse glass–liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role. PMID:25482069

  3. Multiple glass transitions and freezing events of aqueous citric acid.

    Science.gov (United States)

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki; Loerting, Thomas

    2015-05-14

    Calorimetric and optical cryo-microscope measurements of 10-64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid-glass transitions upon cooling and from one to six liquid-glass and reverse glass-liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role.

  4. Hydrophobic Surfaces: Topography Effects on Wetting by Supercooled Water and Freezing Delay

    DEFF Research Database (Denmark)

    Heydari, Golrokh; Thormann, Esben; Järn, Mikael

    2013-01-01

    the dew point. In contrast, no significant wetting transition is observed on the smooth hydrophobic surface. The freezing temperature and the freezing delay time were determined for water droplets resting on a range of surfaces with similar chemistry but different topography, including smooth and rough...... surfaces in either the Wenzel or the Cassie–Baxter state as characterized by water contact angle measurements at room temperature. We find that the water freezing delay time is not significantly affected by the surface topography and discuss this finding within the classical theory of heterogeneous...

  5. A remote controlled freeze corer for sampling unconsolidated surface sediments

    NARCIS (Netherlands)

    Lotter, A.F.; Renberg, I.; Hansson, H.; Stöckli, R.; Sturm, M.

    1997-01-01

    A new coring device is presented which allows the recovery of loose watery surface sediments and the water/sediment interface by in situ freezing, resulting in well preserved samples. The instrument consists of a tripod with adjustable legs, a hydraulic system, an insulated thermos (with

  6. Freezing and glass transitions upon cooling and warming and ice/freeze-concentration-solution morphology of emulsified aqueous citric acid.

    Science.gov (United States)

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki

    2016-12-01

    Although freeze-induced phase separation and the ice/FCS (freeze-concentration solution) morphology of aqueous solutions play an important role in fields ranging from life sciences and biotechnology to geophysics and high-altitude ice clouds, their understanding is far from complete. Herein, using differential scanning calorimetry (DSC) and optical cryo-microscope (OC-M), we have studied the freezing and glass transition behavior and the ice/FCS morphology of emulsified 10-60wt% CA (citric acid) solutions in the temperature region of ∼308and153K. We have obtained a lot of new result which are understandable and unclear. The most essential understandable results are as follows: (i) similar to bulk CA/H2O, emulsified CA/H2O also freezes upon cooling and warming and (ii) the ice/FCS morphology of frozen drops smaller than ∼3-4μm is less ramified than that of frozen bulk solutions. Unclear results, among others, are as follows: (i) in contrast to bulk solutions, which produce one freezing event, emulsified CA/H2O produces two freezing events and (ii) in emulsions, drop concentration is not uniform. Our results demonstrate that DSC thermograms and OC-M images/movies are mutually supplementary and allow us to extract important information which cannot be gained when DSC and OC-M techniques are used alone. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Remote sensing of freeze-thaw transitions in Arctic soils using the complex resistivity method

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuxin [Lawrence Berkeley National Laboratory (LBNL); Hubbard, Susan S [Lawrence Berkeley National Laboratory (LBNL); Ulrich, Craig [Lawrence Berkeley National Laboratory (LBNL); Wullschleger, Stan D [ORNL

    2013-01-01

    Our ability to monitor freeze - thaw transitions is critical to developing a predictive understanding of biogeochemical transitions and carbon dynamics in high latitude environments. In this study, we conducted laboratory column experiments to explore the potential of the complex resistivity method for monitoring the freeze - thaw transitions of the arctic permafrost soils. Samples for the experiment were collected from the upper active layer of Gelisol soils at the Barrow Environmental Observatory, Barrow Alaska. Freeze - thaw transitions were induced through exposing the soil column to controlled temperature environments at 4 C and -20 C. Complex resistivity and temperature measurements were collected regularly during the freeze - thaw transitions using electrodes and temperature sensors installed along the column. During the experiments, over two orders of magnitude of resistivity variations were observed when the temperature was increased or decreased between -20 C and 0 C. Smaller resistivity variations were also observed during the isothermal thawing or freezing processes that occurred near 0 C. Single frequency electrical phase response and imaginary conductivity at 1 Hz were found to be exclusively related to the unfrozen water in the soil matrix, suggesting that these geophysical 24 attributes can be used as a proxy for the monitoring of the onset and progression of the freeze - thaw transitions. Spectral electrical responses and fitted Cole Cole parameters contained additional information about the freeze - thaw transition affected by the soil grain size distribution. Specifically, a shift of the observed spectral response to lower frequency was observed during isothermal thawing process, which we interpret to be due to sequential thawing, first from fine then to coarse particles within the soil matrix. Our study demonstrates the potential of the complex resistivity method for remote monitoring of freeze - thaw transitions in arctic soils. Although

  8. Heat transfer with freezing in a scraped surface heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Lakhdar, M.B. [LGL France Refrigerating Division, Genas (France); Cerecero, R.; Alvarez, G.; Guilpart, J. [Cemagref, Antony cedex (France). Food Process Engineering; Flick, D. [Institut National Agronomique, Paris (France); Lallemand, A. [Institut National des Sciences Appliquees de Lyon (France). Centre de Thermique

    2005-01-01

    An experimental study was carried out on a scraped surface heat exchanger used for freezing of water-ethanol mixture and aqueous sucrose solution. The influence of various parameters on heat transfer intensity was established: product type and composition, flow rate, blade rotation speed, distance between blades and wall. During starting (transient period) the solution is first supercooled, then ice crystals appear on the scraped surface (heterogeneous nucleation) and no more supercooling is observed. It seems that, when blades are 3 mm far from the surface, a constant ice layer is formed having this thickness and acting as a thermal resistance. But when the blades rotate at 1 mm from the surface, periodically all the ice layer is removed despite the surface is not really scraped. This could simplify ice generator technology. An internal heat transfer coefficient was defined; it depends mainly on rotation speed. Correlations were proposed for its prediction, which could be applied, at least as a first approach, for the most common freezing applications of scraped surface heat exchanger i.e. ice creams (which are derived from sucrose solutions) and two-phase secondary refrigerants (which are principally ethanol solutions). (author)

  9. Thermal analysis of ice and glass transitions in insects that do and do not survive freezing.

    Science.gov (United States)

    Rozsypal, Jan; Moos, Martin; Šimek, Petr; Koštál, Vladimír

    2018-03-01

    Some insects rely on the strategy of freeze tolerance for winter survival. During freezing, extracellular body water transitions from the liquid to solid phase and cells undergo freeze-induced dehydration. Here we present results of a thermal analysis (from differential scanning calorimetry) of ice fraction dynamics during gradual cooling after inoculative freezing in variously acclimated larvae of two drosophilid flies, Drosophila melanogaster and Chymomyza costata. Although the species and variants ranged broadly between 0 and close to 100% survival of freezing, there were relatively small differences in ice fraction dynamics. For instance, the maximum ice fraction (IF max ) ranged between 67.9 and 77.7% total body water (TBW). The C. costata larvae showed statistically significant phenotypic shifts in parameters of ice fraction dynamics (melting point and IF max ) upon entry into diapause, cold-acclimation, and feeding on a proline-augmented diet. These differences were mostly driven by colligative effects of accumulated proline (ranging between 6 and 487 mmol.kg -1 TBW) and other metabolites. Our data suggest that these colligative effects per se do not represent a sufficient mechanistic explanation for high freeze tolerance observed in diapausing, cold-acclimated C. costata larvae. Instead, we hypothesize that accumulated proline exerts its protective role via a combination of mechanisms. Specifically, we found a tight association between proline-induced stimulation of glass transition in partially-frozen body liquids (vitrification) and survival of cryopreservation in liquid nitrogen. © 2018. Published by The Company of Biologists Ltd.

  10. Reversed freeze quench method near the solvent phase transition.

    Science.gov (United States)

    Marchanka, Aliaksandr; van Gastel, Maurice

    2012-04-19

    Freeze quenching is a general method for trapping reaction intermediates on a (sub)millisecond time scale. The method relies on a mixing and subsequent rapid freezing of solutions of reactants. If the reaction is limited by diffusion, it may be advantageous to initially mix the reactants under conditions where the reaction does not proceed, e.g., by mixing them at low temperature as solids. The temperature may then be raised close to the melting point of the solvent. Depending on the viscosity of the solvent, the temperature can be raised either by heating or by applying laser pulses of nanosecond length with concomitant conversion of light into heat. A reduction of the dead time and a good control of the reaction speed in comparison to the standard freeze quench technique has been achieved with this method. The feasibility of the method in combination with EPR spectroscopy is verified by examining the important prototypical reductions of benzoquinone and 2,6-dichlorophenolindophenol by ascorbate as representatives for two-step redox reactions. By using light pulses of a laser, the reaction could be driven with rates lowered by 4 orders of magnitude as compared to room temperature reaction rates. This has allowed the observation of previously unobserved radical intermediates: the reduction of DCPIP by ascorbate is found to be strongly pH dependent. It proceeds via two one-electron steps at low pH, whereas at neutral pH, the reduction of DCPIP by ascorbate proceeds in a 1:2 stoichiometry followed by a disproportionation of the ascorbate radicals. © 2012 American Chemical Society

  11. Electrical and seismic response of saline permafrost soil during freeze - Thaw transition

    Science.gov (United States)

    Wu, Yuxin; Nakagawa, Seiji; Kneafsey, Timothy J.; Dafflon, Baptiste; Hubbard, Susan

    2017-11-01

    We conducted laboratory studies on the geophysical signals from Arctic saline permafrost soils to help understand the physical and mechanical processes during freeze-thaw cycles. Our results revealed low electrical resistivity (freezing process, affected by concurrent changes of temperature, salinity, and ice formation. An anomalous induced polarization response was first observed during the transient period of supercooling and the onset of ice nucleation. Seismic measurements showed a characteristic maximal attenuation at the temperatures immediately below the freezing point, followed by a decrease with decreasing temperature. The calculated elastic moduli showed a non-hysteric response during the freeze - thaw cycle, which was different from the concurrently measured electrical resistivity response where a differential resistivity signal is observed depending on whether the soil is experiencing freezing or thawing. The differential electrical resistivity signal presents challenges for unfrozen water content estimation based on Archie's law. Using an improved formulation of Archie's law with a variable cementation exponent, the unfrozen water content estimation showed a large variation depending on the choice of the resistivity data during either a freezing or thawing cycle. Combining the electrical and seismic results, we suggest that, rather than a large hysteresis in the actual unfrozen water content, the shift of the resistivity response may reflect the changes of the distribution pattern of the unfrozen water (or ice) in the soil matrix during repeated freeze and thaw processes. Collectively, our results provide an improved petrophysical understanding of the physical and mechanical properties of saline permafrost during freeze - thaw transitions, and suggest that large uncertainty may exist when estimating the unfrozen water content using electrical resistivity data.

  12. Perspective: Surface freezing in water: A nexus of experiments and simulations

    Science.gov (United States)

    Haji-Akbari, Amir; Debenedetti, Pablo G.

    2017-08-01

    Surface freezing is a phenomenon in which crystallization is enhanced at a vapor-liquid interface. In some systems, such as n-alkanes, this enhancement is dramatic and results in the formation of a crystalline layer at the free interface even at temperatures slightly above the equilibrium bulk freezing temperature. There are, however, systems in which the enhancement is purely kinetic and only involves faster nucleation at or near the interface. The first, thermodynamic, type of surface freezing is easier to confirm in experiments, requiring only the verification of the existence of crystalline order at the interface. The second, kinetic, type of surface freezing is far more difficult to prove experimentally. One material that is suspected of undergoing the second type of surface freezing is liquid water. Despite strong indications that the freezing of liquid water is kinetically enhanced at vapor-liquid interfaces, the findings are far from conclusive, and the topic remains controversial. In this perspective, we present a simple thermodynamic framework to understand conceptually and distinguish these two types of surface freezing. We then briefly survey fifteen years of experimental and computational work aimed at elucidating the surface freezing conundrum in water.

  13. Understanding and Analyzing Freezing-Point Transitions of Confined Fluids within Nanopores.

    Science.gov (United States)

    Shimizu, Steven; Agrawal, Kumar Varoon; O'Mahony, Marcus; Drahushuk, Lee W; Manohar, Neha; Myerson, Allan S; Strano, Michael S

    2015-09-22

    Understanding phase transitions of fluids confined within nanopores is important for a wide variety of technological applications. It is well known that fluids confined in nanopores typically demonstrate freezing-point depressions, ΔTf, described by the Gibbs-Thomson (GT) equation. Herein, we highlight and correct several thermodynamic inconsistencies in the conventional use of the GT equation, including the fact that the enthalpy of melting, ΔHm, and the solid-liquid surface energy, γ(SL), are functions of pore diameter, complicating their prediction. We propose a theoretical analysis that employs the Turnbull coefficient, originally derived from metal nucleation theory, and show its consistency as a more reliable quantity for the prediction of ΔTf. This analysis provides a straightforward method to estimate ΔTf of nanoconfined organic fluids. As an example, we apply this technique to ibuprofen, an active pharmaceutical ingredient (API), and show that this theory fits well to the experimental ΔTf of nanoconfined ibuprofen.

  14. Fracture Surface Fractal Characteristics of Alkali-Slag Concrete under Freeze-Thaw Cycles

    Directory of Open Access Journals (Sweden)

    Wantong Cai

    2017-01-01

    Full Text Available Fractal theory is introduced in fracture surface research of alkali-slag concrete (ASC under freeze-thaw cycles; crack distribution of ASC fracture surface and freeze-thaw damage zone were calculated. Through fractal analysis of ASC sample fracture surfaces, relevance between section fractal dimension and fracture toughness and relationship between material composition and section fractal dimension are clarified. Results show that the specimen’s cracks before freeze-thaw extend along force direction gently, and there are more twists and turns after freezing and thawing; the fractal dimension D also grows from 1.10 to 1.33. SEM internal microcracks’ D of ASC internal microstructure after freezing and thawing is 1.37; 0 to 300 times ASC fractal dimension under freezing and thawing is between 2.10 and 2.23; with freeze-thaw times increasing, ASC fracture toughness decreases and fractal dimension increases, the fractal dimension and fracture toughness have a good linear relationship, and the fractal dimension can reflect the toughening effect of ASC. It is very feasible to evaluate ASC fracture behaviour under freezing and thawing with the fractal theory. Fractal dimension generally increases with activator solution-slag (A/S for short or slag content. The greater the amount of A/S or slag content, the lower the dimension.

  15. Vacuum-Induced Surface Freezing to Produce Monoliths of Aligned Porous Alumina

    Directory of Open Access Journals (Sweden)

    Sandra Großberger

    2016-12-01

    Full Text Available Vacuum-induced surface freezing has been used to produce uni-directional freezing of colloidal aluminum oxide dispersions. It leads to zones of different structure within the resulting sintered monoliths that are highly similar to those known for freeze casting using a cryogen cold source. A more-or-less dense surface layer and a cellular sub-surface region are formed, beneath which is a middle region of aligned lamellae and pores that stretches through most of the depth of the monolith. This is the case even at a volume fraction of dispersed phase as low as 0.032. A more-dense but still porous base layer is formed by accumulation of rejected nanoparticles preceding the freezing front and differs from previous reports in that no ice lenses are observed. X-ray micro-computed tomography reveals a uniform aligned pore structure vertically through the monolith. The pores close to the periphery are oriented radially or as chords, while the center region contains domains of parallel pores/lamellae. The domains are randomly oriented to one another, as already reported for regular freeze casting. This technique for directional freezing is convenient and easy to perform, but requires further refinement in that the temperature gradient and freezing rates remain yet to be measured. Also, control of the temperature gradient by varying chamber vacuum and shelf temperature needs to be evaluated.

  16. Snowmelt and Surface Freeze/Thaw Timings over Alaska derived from Passive Microwave Observations using a Wavelet Classifier

    Science.gov (United States)

    Steiner, N.; McDonald, K. C.; Dinardo, S. J.; Miller, C. E.

    2015-12-01

    Arctic permafrost soils contain a vast amount of organic carbon that will be released into the atmosphere as carbon dioxide or methane when thawed. Surface to air greenhouse gas fluxes are largely dependent on such surface controls as the frozen/thawed state of the snow and soil. Satellite remote sensing is an important means to create continuous mapping of surface properties. Advances in the ability to determine soil and snow freeze/thaw timings from microwave frequency observations improves upon our ability to predict the response of carbon gas emission to warming through synthesis with in-situ observation, such as the 2012-2015 Carbon in Arctic Reservoir Vulnerability Experiment (CARVE). Surface freeze/thaw or snowmelt timings are often derived using a constant or spatially/temporally variable threshold applied to time-series observations. Alternately, time-series singularity classifiers aim to detect discontinuous changes, or "edges", in time-series data similar to those that occur from the large contrast in dielectric constant during the freezing or thaw of soil or snow. We use multi-scale analysis of continuous wavelet transform spectral gradient brightness temperatures from various channel combinations of passive microwave radiometers, Advanced Microwave Scanning Radiometer (AMSR-E, AMSR2) and Special Sensor Microwave Imager (SSM/I F17) gridded at a 10 km posting with resolution proportional to the observational footprint. Channel combinations presented here aim to illustrate and differentiate timings of "edges" from transitions in surface water related to various landscape components (e.g. snow-melt, soil-thaw). To support an understanding of the physical basis of observed "edges" we compare satellite measurements with simple radiative transfer microwave-emission modeling of the snow, soil and vegetation using in-situ observations from the SNOw TELemetry (SNOTEL) automated weather stations. Results of freeze/thaw and snow-melt timings and trends are

  17. Modeling the capability of penetrating a jammed crowd to eliminate freezing transition

    Science.gov (United States)

    Mohammed Mahmod, Shuaib

    2016-05-01

    Frozen state from jammed state is one of the most interesting aspects produced when simulating the multidirectional pedestrian flow of high density crowds. Cases of real life situations for such a phenomenon are not exhaustively treated. Our observations in the Hajj crowd show that freezing transition does not occur very often. On the contrary, penetrating a jammed crowd is a common aspect. We believe the kindness of pedestrians facing others whose walking is blocked is a main factor in eliminating the frozen state as well as in relieving the jammed state. We refine the social force model by incorporating a new social force to enable the simulated pedestrians to mimic the real behavior observed in the Hajj area. Simulations are performed to validate the work qualitatively.

  18. Glass transition near the free surface studied by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sikorski, M.

    2008-06-15

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-{mu}m length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  19. Synergistic structures from magnetic freeze casting with surface magnetized alumina particles and platelets.

    Science.gov (United States)

    Frank, Michael B; Hei Siu, Sze; Karandikar, Keyur; Liu, Chin-Hung; Naleway, Steven E; Porter, Michael M; Graeve, Olivia A; McKittrick, Joanna

    2017-12-01

    Magnetic freeze casting utilizes the freezing of water, a low magnetic field and surface magnetized materials to make multi-axis strengthened porous scaffolds. A much greater magnetic moment was measured for larger magnetized alumina platelets compared with smaller particles, which indicated that more platelet aggregation occurred within slurries. This led to more lamellar wall alignment along the magnetic field direction during magnetic freeze casting at 75 mT. Slurries with varying ratios of magnetized particles to platelets (0:1, 1:3, 1:1, 3:1, 7:1, 1:0) produced porous scaffolds with different structural features and degrees of lamellar wall alignment. The greatest mechanical enhancement in the magnetic field direction was identified in the synergistic condition with the highest particle to platelet ratio (7:1). Magnetic freeze casting with varying ratios of magnetized anisotropic and isotropic alumina provided insights about how heterogeneous morphologies aggregate within lamellar walls that impact mechanical properties. Fabrication of strengthened scaffolds with multi-axis aligned porosity was achieved without introducing different solid materials, freezing agents or additives. Resemblance of 7:1 particle to platelet scaffold microstructure to wood light-frame house construction is framed in the context of assembly inspiration being derived from both natural and synthetic sources. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Electrical Capacitance Tomography Measurement of the Migration of Ice Frontal Surface in Freezing Soil

    Directory of Open Access Journals (Sweden)

    Liu J.

    2016-12-01

    Full Text Available The tracking of the migration of ice frontal surface is crucial for the understanding of the underlying physical mechanisms in freezing soil. Owing to the distinct advantages, including non-invasive sensing, high safety, low cost and high data acquisition speed, the electrical capacitance tomography (ECT is considered to be a promising visualization measurement method. In this paper, the ECT method is used to visualize the migration of ice frontal surface in freezing soil. With the main motivation of the improvement of imaging quality, a loss function with multiple regularizers that incorporate the prior formation related to the imaging objects is proposed to cast the ECT image reconstruction task into an optimization problem. An iteration scheme that integrates the superiority of the split Bregman iteration (SBI method is developed for searching for the optimal solution of the proposed loss function. An unclosed electrodes sensor is designed for satisfying the requirements of practical measurements. An experimental system of one dimensional freezing in frozen soil is constructed, and the ice frontal surface migration in the freezing process of the wet soil sample containing five percent of moisture is measured. The visualization measurement results validate the feasibility and effectiveness of the ECT visualization method

  1. MAS1H NMR Probes Freezing Point Depression of Water and Liquid-Gel Phase Transitions in Liposomes.

    Science.gov (United States)

    Mandal, Abhishek; van der Wel, Patrick C A

    2016-11-01

    The lipid bilayer typical of hydrated biological membranes is characterized by a liquid-crystalline, highly dynamic state. Upon cooling or dehydration, these membranes undergo a cooperative transition to a rigidified, more-ordered, gel phase. This characteristic phase transition is of significant biological and biophysical interest, for instance in studies of freezing-tolerant organisms. Magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy allows for the detection and characterization of the phase transitions over a wide temperature range. In this study we employ MAS 1 H NMR to probe the phase transitions of both solvent molecules and different hydrated phospholipids, including tetraoleoyl cardiolipin (TOCL) and several phosphatidylcholine lipid species. The employed MAS NMR sample conditions cause a previously noted substantial reduction in the freezing point of the solvent phase. The effect on the solvent is caused by confinement of the aqueous solvent in the small and densely packed MAS NMR samples. In this study we report and examine how the freezing point depression also impacts the lipid phase transition, causing a ssNMR-observed reduction in the lipids' melting temperature (T m ). The molecular underpinnings of this phenomenon are discussed and compared with previous studies of membrane-associated water phases and the impact of membrane-protective cryoprotectants. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  2. Freeze-Drying Above the Glass Transition Temperature in Amorphous Protein Formulations While Maintaining Product Quality and Improving Process Efficiency.

    Science.gov (United States)

    Depaz, Roberto A; Pansare, Swapnil; Patel, Sajal Manubhai

    2016-01-01

    This study explored the ability to conduct primary drying during lyophilization at product temperatures above the glass transition temperature of the maximally freeze-concentrated solution (Tg′) in amorphous formulations for four proteins from three different classes. Drying above Tg′ resulted in significant reductions in lyophilization cycle time. At higher protein concentrations, formulations freeze dried above Tg′ but below the collapse temperature yielded pharmaceutically acceptable cakes. However, using an immunoglobulin G type 4 monoclonal antibody as an example, we found that as protein concentration decreased, minor extents of collapse were observed in formulations dried at higher temperatures. No other impacts to product quality, physical stability, or chemical stability were observed in this study among the different drying conditions for the different proteins. Drying amorphous formulations above Tg′, particularly high protein concentration formulations, is a viable means to achieve significant time and cost savings in freeze-drying processes.

  3. Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition.

    Science.gov (United States)

    Syamaladevi, Roopesh M; Sablani, Shyam S; Tang, Juming; Powers, Joseph; Swanson, Barry G

    2011-08-01

    Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze-dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at -80, -35, and -20 °C, while freeze-dried raspberries were stored at selected water activity (a(w)) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T'(g)) of raspberries with high water content and glass transition temperature (T(g)) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze-dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at -20 and -35, and -80 °C. Anthocyanin degradation in freeze-dried raspberries ranged from 27% to 32% and 78% to 89% at a(w) values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze-dried raspberries stored at a(w) values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze-dried raspberries. The 1(st)-order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days⁻¹ at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze-dried raspberries during long-term storage. However, the rate of anthocyanin degradation in freeze-dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state. © 2011 Institute of Food Technologists®

  4. Surface properties of 3d transition metals

    Science.gov (United States)

    Punkkinen, M. P. J.; Hu, Q.-M.; Kwon, S. K.; Johansson, B.; Kollár, J.; Vitos, L.

    2011-09-01

    Using the projector augmented wave method within density functional theory, we present a systematic study of the layer relaxation, surface energy and surface stress of 3d transition metals. Comparing the calculated trends for the surface energy and stress with those obtained for 4d and 5d metals we find that magnetism has a significant effect on the surface properties. Enhanced surface magnetic moments decrease the size of the surface relaxation, lower the surface energy and surface stress, leading to compressive stress in Cr and Mn.

  5. Nonuniversal surface behavior of dynamic phase transitions.

    Science.gov (United States)

    Riego, Patricia; Berger, Andreas

    2015-06-01

    We have studied the dynamic phase transition (DPT) of the kinetic Ising model in systems with surfaces within the mean-field approximation. Varying the surface exchange coupling strength J(s), the amplitude of the externally applied oscillating field h(0), and its period P, we explore the dynamic behavior of the layer-dependent magnetization and the associated DPTs. The surface phase diagram shows several features that resemble those of the equilibrium case, with an extraordinary bulk transition and a surface transition for high J(s) values, independent from the value of h(0). For low J(s), however, h(0) is found to be a crucial parameter that leads to nonuniversal surface behavior at the ordinary bulk transition point. Specifically, we observed here a bulk-supported surface DPT for high field amplitudes h(0) and correspondingly short critical periods P(c), whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h(0). The suppression of the DPT for low h(0) not only occurs for the topmost surface layer, but also affects a significant number of subsurface layers. We find that the key physical quantity that explains this nonuniversal behavior is the time correlation between the dynamic surface and bulk magnetizations at the bulk critical point. This time correlation has to pass a threshold value to trigger a bulk-induced DPT in the surface layers. Otherwise, dynamic phase transitions are absent at the surface in stark contrast to the equilibrium behavior of the corresponding thermodynamic Ising model. Also, we have analyzed the penetration depth of the dynamically ordered phase for the surface DPT that occurs for large J(s) values. Here we find that the penetration depth depends strongly on J(s) and behaves identically to the corresponding equilibrium Ising model.

  6. Research into action of surface soil moistening, drying or freezing on electrical characteristics of grounding device

    Directory of Open Access Journals (Sweden)

    I.V. Nizhevskiy

    2014-03-01

    Full Text Available The analysis made has shown expediency of modernization rather than reconstruction of earth electrodes, after inspection of long operating substations grounding grids, via building a two-level structure. It will result in both technical and economic effects. The novelty of the results consists in studying, by means of a mathematical model, electrical characteristics of a two-level earth electrode versus the depth of surface soil drying or freezing.

  7. Freezing transitions and extreme values: random matrix theory, and disordered landscapes

    Science.gov (United States)

    Fyodorov, Yan V.; Keating, Jonathan P.

    2014-01-01

    We argue that the freezing transition scenario, previously conjectured to occur in the statistical mechanics of 1/f-noise random energy models, governs, after reinterpretation, the value distribution of the maximum of the modulus of the characteristic polynomials pN(θ) of large N×N random unitary (circular unitary ensemble) matrices UN; i.e. the extreme value statistics of pN(θ) when . In addition, we argue that it leads to multi-fractal-like behaviour in the total length μN(x) of the intervals in which |pN(θ)|>Nx,x>0, in the same limit. We speculate that our results extend to the large values taken by the Riemann zeta function ζ(s) over stretches of the critical line of given constant length and present the results of numerical computations of the large values of ). Our main purpose is to draw attention to the unexpected connections between these different extreme value problems. PMID:24344336

  8. Surface transition in spin crossover nanoparticles

    Science.gov (United States)

    Mikolasek, Mirko; Nicolazzi, William; Terki, Férial; Molnár, Gábor; Bousseksou, Azzedine

    2017-06-01

    The spin transition in a square lattice nanoparticle, whose the primitive cell is constituted of 2 metallic centres, is investigated using a two-variable elastic Ising-like model solved by Monte Carlo simulations. We show that the specific lattice geometry can lead to an important surface relaxation of both the structure and the spin-state, which are analysed by mapping the local strain. The consequence of this surface relaxation is the occurrence of a stepwise spin transition where the surface and the core switch at different temperatures.

  9. Spray Irrigation Effects on Surface-Layer Stability in an Experimental Citrus Orchard during Winter Freezes.

    Science.gov (United States)

    Cooper, Harry J.; Smith, Eric A.; Martsolf, J. David

    1997-02-01

    Observations taken by two surface radiation and energy budget stations deployed in the University of Florida/Institute for Food and Agricultural Service experimental citrus orchard in Gainesville, Florida, have been analyzed to identify the effects of sprayer irrigation on thermal stability and circulation processes within the orchard during three 1992 winter freeze episodes. Lapse rates of temperature observed from a micrometeorological tower near the center of the orchard were also recorded during periods of irrigation for incorporation into the analysis. Comparisons of the near-surface temperature lapse rates observed with the two energy budget stations show consistency between the two sites and with the tower-based lapse rates taken over a vertical layer from 1.5 to 15 m above ground level. A theoretical framework was developed that demonstrates that turbulent-scale processes originating within the canopy, driven by latent heat release associated with condensation and freezing processes from water vapor and liquid water released from sprayer nozzles, can destabilize lapse rates and promote warm air mixing above the orchard canopy. The orchard data were then analyzed in the context of the theory for evidence of local overturning and displacement of surface-layer air, with warmer air from aloft driven by locally buoyant plumes generated by water vapor injected into the orchard during the irrigation periods. It was found that surface-layer lapse rates were lower during irrigation periods than under similar conditions when irrigation was not occurring, indicating a greater degree of vertical mixing of surface-layer air with air from above treetops, as a result of local convective overturning induced by the condensation heating of water vapor released at the nozzles of the sprinklers. This provides an additional explanation to the well-accepted heat of fusion release effect, of how undertree irrigation of a citrus orchard during a freeze period helps protect crops

  10. Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

    Science.gov (United States)

    Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

    2013-06-18

    For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  11. Effect of Aluminum Substrate Surface Modification on Wettability and Freezing Delay of Water Droplet at Subzero Temperatures

    DEFF Research Database (Denmark)

    Rahimi, Maral; Afshari, Alireza; Thormann, Esben

    2016-01-01

    In this study, we have investigated the freezing delay of a water droplet on precooled substrates of an aluminum alloy that is commonly used for heat-exchanger fins. The surfaces of the substrates were modified to obtain surfaces with different hydrophilicity/hydrophobicity and different surface ...... chemistry plays a significant role in the kinetics of the ice formation process when a water droplet is placed on a precooled substrate.......In this study, we have investigated the freezing delay of a water droplet on precooled substrates of an aluminum alloy that is commonly used for heat-exchanger fins. The surfaces of the substrates were modified to obtain surfaces with different hydrophilicity/hydrophobicity and different surface...... chemistry but without significantly modifying the surface topography. The freezing delays and water contact angles were measured as a function of the substrate temperature and the results were compared to the predictions of the heterogeneous ice nucleation theory. Although the trends for each sample...

  12. Freeze-Drying of Plant Tissue Containing HBV Surface Antigen for the Oral Vaccine against Hepatitis B

    Directory of Open Access Journals (Sweden)

    Marcin Czyż

    2014-01-01

    Full Text Available The aim of this study was to develop a freeze-drying protocol facilitating successful processing of plant material containing the small surface antigen of hepatitis B virus (S-HBsAg while preserving its VLP structure and immunogenicity. Freeze-drying of the antigen in lettuce leaf tissue, without any isolation or purification step, was investigated. Each process step was consecutively evaluated and the best parameters were applied. Several drying profiles and excipients were tested. The profile of 20°C for 20 h for primary and 22°C for 2 h for secondary drying as well as sucrose expressed efficient stabilisation of S-HBsAg during freeze-drying. Freezing rate and postprocess residual moisture were also analysed as important factors affecting S-HBsAg preservation. The process was reproducible and provided a product with VLP content up to 200 µg/g DW. Assays for VLPs and total antigen together with animal immunisation trials confirmed preservation of antigenicity and immunogenicity of S-HBsAg in freeze-dried powder. Long-term stability tests revealed that the stored freeze-dried product was stable at 4°C for one year, but degraded at elevated temperatures. As a result, a basis for an efficient freeze-drying process has been established and a suitable semiproduct for oral plant-derived vaccine against HBV was obtained.

  13. Understanding the physical stability of freeze dried dosage forms from the glass transition temperature of the amorphous components.

    Science.gov (United States)

    Fitzpatrick, Shaun; Saklatvala, Robert

    2003-12-01

    Modulated differential scanning calorimetry has been applied to understanding the long-term physical stability of freeze-dried units. It is known that these units are liable to contract on exposure to elevated temperature or humidity. The contraction occurs when the storage temperature is above the glass transition temperature of the amorphous components in the system. The effect of moisture content on the glass transition temperature of the amorphous components in the system has been studied. By combining this information with the moisture sorption isotherm it has been demonstrated that it is possible to predict the temperature and humidity conditions that will induce contraction of the unit. The magnitude of the glass transition temperature is composed of the contribution of each of the amorphous components in the system. It is proposed that it should be possible to develop a more robust system by the rational selection of excipients that increase the glass transition temperature or by modification of the processing conditions to promote crystallization of components that would otherwise depress the glass transition temperature. Copyright 2003 Wiley-Liss, Inc.

  14. Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets

    Directory of Open Access Journals (Sweden)

    T. Kuhn

    2011-03-01

    Full Text Available The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 μm. Temperature- and size-dependent values of volume- and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 μm. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered.

  15. Glass transition-related changes in molecular mobility below glass transition temperature of freeze-dried formulations, as measured by dielectric spectroscopy and solid state nuclear magnetic resonance.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio

    2005-02-01

    The purpose of this study was to explore why changes in the molecular mobility associated with glass transition, the timescale of which is on the order of 100 s, can be detected by measuring the nuclear magnetic resonance relaxation times that reflect molecular motions on the order of 10 kHz and 1 MHz. The molecular motions in freeze-dried dextran 40k, dextran 1k, isomaltotriose (IMT), and alpha-glucose comprising a common unit but with different glass transition temperatures, were investigated by dielectric spectroscopy (DES) in the frequency range of 0.01 Hz to 100 kHz and in the temperature range of -20 degrees to 200 degrees C, in order to compare with the molecular motions reflected in nuclear magnetic resonance relaxation times. The alpha-relaxation process for freeze-dried alpha-glucose was visualized by DES, whereas those for freeze-dried dextran 40k, dextran 1k, and IMT were too slow to be visualized by DES. The latter freeze-dried cakes exhibited quasi-dc polarization because of proton-hopping-like motion rather than alpha-relaxation process. The correlation time (tau(c)) for the backbone carbon of dextran 40k and IMT, calculated from the measured value of spin-lattice relaxation time in the rotating frame, was found to be close to the relaxation time of proton-hopping-like motion determined by DES (tau(DES)) at temperatures around glass transition temperature. The timescales of molecular motions reflected in the tau(c) and tau(DES) were significantly smaller than that of motions leading to molecular rearrangement (molecular rearrangement motions), which correspond to alpha-relaxation. However, the shapes of temperature dependence for the tau(c) and tau(DES) were similar to that of the calorimetrically determined relaxation time of molecular rearrangement motions. Results suggest that the molecular motions reflected in the tau(c) and tau(DES) are linked to molecular rearrangement motions, such that enhancement of molecular rearrangement motions enhances

  16. Assimilation of Freeze - Thaw Observations into the NASA Catchment Land Surface Model

    Science.gov (United States)

    Farhadi, Leila; Reichle, Rolf H.; DeLannoy, Gabrielle J. M.; Kimball, John S.

    2014-01-01

    The land surface freeze-thaw (F-T) state plays a key role in the hydrological and carbon cycles and thus affects water and energy exchanges and vegetation productivity at the land surface. In this study, we developed an F-T assimilation algorithm for the NASA Goddard Earth Observing System, version 5 (GEOS-5) modeling and assimilation framework. The algorithm includes a newly developed observation operator that diagnoses the landscape F-T state in the GEOS-5 Catchment land surface model. The F-T analysis is a rule-based approach that adjusts Catchment model state variables in response to binary F-T observations, while also considering forecast and observation errors. A regional observing system simulation experiment was conducted using synthetically generated F-T observations. The assimilation of perfect (error-free) F-T observations reduced the root-mean-square errors (RMSE) of surface temperature and soil temperature by 0.206 C and 0.061 C, respectively, when compared to model estimates (equivalent to a relative RMSE reduction of 6.7 percent and 3.1 percent, respectively). For a maximum classification error (CEmax) of 10 percent in the synthetic F-T observations, the F-T assimilation reduced the RMSE of surface temperature and soil temperature by 0.178 C and 0.036 C, respectively. For CEmax=20 percent, the F-T assimilation still reduces the RMSE of model surface temperature estimates by 0.149 C but yields no improvement over the model soil temperature estimates. The F-T assimilation scheme is being developed to exploit planned operational F-T products from the NASA Soil Moisture Active Passive (SMAP) mission.

  17. Optimization of a cryoprotective medium to increase the viability of freeze-dried Streptococcus thermophilus by response surface methodology

    Science.gov (United States)

    Streptococcus thermophilus normally exhibits different survival rates in different bacteria medium during freeze-drying. In this study, response surface methodology (RSM) was applied on the design of experiments for optimizing the cryoprotective medium. Results showed that the most significant facto...

  18. Effect of transition metal cations on commensurate freezing of n-hexane confined in micropores of ZSM-5

    Directory of Open Access Journals (Sweden)

    Hercigonja Radmila

    2015-01-01

    Full Text Available Besides its importance concerning fundamental studies on gas adsorption in narrow pores, investigation of commensurate freezing of fluid within the zeolite is of practical importance in application of zeolite in the process of adsorption, separation and catalysis. In this work the adsorption of n-hexane on HZSM-5 and its transition metal ion-exchanged modified forms was studied at 303 K by means of microcalorimetry. The thermal molar entropies of adsorption were calculated and thus, the freezing like behaviour of n-hexane inside the structure of zeolite as a confinement media was noticed. This effect is governed by the attractive interactions between n-hexane molecules and the pore walls, and is also influenced by the length of the pores and the nature of charge-balancing cations. Among the investigated zeolites, solid like phase of n-hexane in the pores of zeolites with Fe2+ ions is the most like a solid n-hexane bulk, while the presence of Cu2+ ions contribute to the lowest ordering obtained solid like phase of n-hexane. [Projekat Ministarstva nauke Republike Srbije, br. 172018

  19. A novel collagen film with micro-rough surface structure for corneal epithelial repair fabricated by freeze drying technique

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Ren, Li, E-mail: psliren@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Wang, Yingjun, E-mail: imwangyj@163.com [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China)

    2014-05-01

    Highlights: • Collagen film with micro-rough surface is fabricated by freeze drying technique. • The film has suitable water uptake capability and toughness performance. • The film has good optical performance. • Human corneal epithelial cells studies confirmed the biocompatibility of the film. - Abstract: Corneal epithelial defect is a common disease and keratoplasty is a common treatment method. A collagen film with micro-rough surface was fabricated through a simple freeze drying technique in this study. Compared with the air-dried collagen film (AD-Col), this freeze-dried collagen film (FD-Col) has a more suitable water uptake capability (about 85.5%) and toughness performance. Both of the two films have good optical properties and the luminousness of them is higher than 80%. Besides, the adhesion and proliferation rate of human corneal epithelial cells on the micro-rough surface of FD-Col film is higher than that on the smooth surface of AD-Col film. The results indicate that this FD-Col film may have potential applications for corneal epithelial repair.

  20. The Soil Moisture Active Passive (SMAP) Radar: Measurements at High Latitudes and of Surface Freeze/Thaw State

    Science.gov (United States)

    Spencer, Michael; Dunbar, Scott; Chen, Curtis

    2013-01-01

    The Soil Moisture Active/Passive (SMAP) mission is scheduled for a late 2014 launch date. The mission will use both active radar and passive radiometer instruments at L-Band in order to achieve the science objectives of measuring soil moisture and land surface freeze-thaw state. To achieve requirements for a wide swath at sufficiently high resolution for both active and passive channels, an instrument architecture that uses a large rotating reflector is employed. In this paper, focus will be placed on the radar design. The radar will employ synthetic-aperture processing to achieve a "moderate" resolution dual-pol product over a 1000 km swath. Because the radar is operating continuously, very frequent temporal coverage will be achieved at high latitudes. This data will be used to produce a surface freeze/thaw state data product.

  1. Freezing on a sphere.

    Science.gov (United States)

    Guerra, Rodrigo E; Kelleher, Colm P; Hollingsworth, Andrew D; Chaikin, Paul M

    2018-02-14

    The best understood crystal ordering transition is that of two-dimensional freezing, which proceeds by the rapid eradication of lattice defects as the temperature is lowered below a critical threshold. But crystals that assemble on closed surfaces are required by topology to have a minimum number of lattice defects, called disclinations, that act as conserved topological charges-consider the 12 pentagons on a football or the 12 pentamers on a viral capsid. Moreover, crystals assembled on curved surfaces can spontaneously develop additional lattice defects to alleviate the stress imposed by the curvature. It is therefore unclear how crystallization can proceed on a sphere, the simplest curved surface on which it is impossible to eliminate such defects. Here we show that freezing on the surface of a sphere proceeds by the formation of a single, encompassing crystalline 'continent', which forces defects into 12 isolated 'seas' with the same icosahedral symmetry as footballs and viruses. We use this broken symmetry-aligning the vertices of an icosahedron with the defect seas and unfolding the faces onto a plane-to construct a new order parameter that reveals the underlying long-range orientational order of the lattice. The effects of geometry on crystallization could be taken into account in the design of nanometre- and micrometre-scale structures in which mobile defects are sequestered into self-ordered arrays. Our results may also be relevant in understanding the properties and occurrence of natural icosahedral structures such as viruses.

  2. Compressive Surface Stress in Magnetic Transition Metals

    Science.gov (United States)

    Punkkinen, M. P. J.; Kwon, S. K.; Kollár, J.; Johansson, B.; Vitos, L.

    2011-02-01

    Because of the increased electron density within the surface layer, metal surfaces are generally expected to have tensile surface stress. Here, using first-principles density functional calculations, we demonstrate that in magnetic 3d metals surface magnetism can alter this commonly accepted picture. We find that the thermodynamically stable surfaces of chromium and manganese possess compressive surface stress. The revealed negative surface stress is shown to be ascribed to the enhanced magnetic moments within the surface layer relative to the bulk values.

  3. Response Surface Optimization of Lyoprotectant from Amino Acids and Salts for Bifidobacterium Bifidum During Vacuum Freeze-Drying

    Directory of Open Access Journals (Sweden)

    Qi Kangru

    2017-12-01

    Full Text Available High quality probiotic powder can lay the foundation for the commercial production of functional dairy products. The freeze-drying method was used for the preservation of microorganisms, having a deleterious effect on the microorganisms viability. In order to reduce the damage to probiotics and to improve the survival rate of probiotics during freeze-drying, the Response Surface Methodology (RSM was adopted in this research to optimize lyoprotectant composed of amino acids (glycine, arginine and salts (NaHCO3 and ascorbic acid. Probiotic used was Bifidobacterium bifidum BB01. The regression model (p<0.05 was obtained by Box–Behnken experiment design, indicating this model can evaluate the freeze-drying survival rate of B. bifidum BB01 under different lyoprotectants. The results indicated these concentrations as optimal (in W/V: glycine 4.5%, arginine 5.5%, NaHCO3 0.8% and ascorbic acid 2.3%, respectively. Under these optimal conditions, the survival rate of lyophilized powder of B. bifidum BB01 was significantly increased by 80.9% compared to the control group (6.9±0.62%, the results were agreement with the model prediction value (88.7%.

  4. PHBV/PLLA-based composite scaffolds fabricated using an emulsion freezing/freeze-drying technique for bone tissue engineering: surface modification and in vitro biological evaluation.

    Science.gov (United States)

    Sultana, Naznin; Wang, Min

    2012-03-01

    Tissue engineering combines living cells with biodegradable materials and/or bioactive components. Composite scaffolds containing biodegradable polymers and nanosized osteoconductive bioceramic with suitable properties are promising for bone tissue regeneration. In this paper, based on blending two biodegradable and biocompatible polymers, namely poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(L-lactic acid) (PLLA) with incorporated nano hydroxyapatite (HA), three-dimensional composite scaffolds with controlled microstructures and an interconnected porous structure, together with high porosity, were fabricated using an emulsion freezing/freeze-drying technique. The influence of various parameters involved in the emulsion freezing/freeze-drying technique was studied for the fabrication of good-quality polymer scaffolds based on PHBV polymers. The morphology, mechanical properties and crystallinity of PHBV/PLLA and HA in PHBV/PLLA composite scaffolds and PHBV polymer scaffolds were studied. The scaffolds were coated with collagen in order to improve wettability. During in vitro biological evaluation study, it was observed that SaOS-2 cells had high attachment on collagen-coated scaffolds. Significant improvement in cell proliferation and alkaline phosphatase activity for HA-incorporated composite scaffolds was observed due to the incorporation of HA. After 3 and 7 days of culture on all scaffolds, SaOS-2 cells also had normal morphology and growth. These results indicated that PHBV/PLLA-based scaffolds fabricated via an emulsion freezing/freeze-drying technique were favorable sites for osteoblastic cells and are promising for the applications of bone tissue engineering.

  5. Surface Premelting Coupled with Bulk Phase Transitions in Colloidal Crystals

    Science.gov (United States)

    Li, Bo; Wang, Feng; Zhou, Di; Cao, Xin; Peng, Yi; Ni, Ran; Liao, Maijia; Han, Yilong

    2015-03-01

    Colloids have been used as outstanding model systems for the studies of various phase transitions in bulk, but not at interface yet. Here we obtained equilibrium crystal-vapor interfaces using tunable attractive colloidal spheres and studied the surface premelting at the single-particle level by video microscopy. We found that monolayer crystals exhibit a bulk isostructural solid-solid transition which triggers the surface premelting. The premelting is incomplete due to the interruption of a mechanical-instability-induced bulk melting. By contrast, two- or multilayer crystals do not have the solid-solid transition and the mechanical instability, hence they exhibit complete premelting with divergent surface-liquid thickness. These novel interplays between bulk and surface phase transitions cast new lights for both types of transitions.

  6. Single bacteriorhodopsin molecules revealed on both surfaces of freeze- dried and heavy metal-decorated purple membranes

    Science.gov (United States)

    1981-01-01

    The flat sheets of the purple membrane from Halobacterium halobium contain only a single protein (bacteriorhodopsin) arranged in a hexagonal lattice. After freeze-drying at -80 degrees C (a method that is superior to air-drying), shadowing with tantalum/tungsten, and image processing, structural details on both surfaces are portrayed in the range of 2 nm. One surface is rough and lattice lines are clearly visible, whereas the other is smooth and the hexagonal order seems to be absent. The optical diffraction patterns, however, indicate a hexagonal lattice for both surfaces. In addition, these diffraction patterns are characteristic and easily distinguished. The orientation of the two surfaces was identified by silver decoration: partial condensation of silver on purple membranes enabled the smooth surface to be identified as the plasmatic and the rough surface as the exoplasmic surface. After image processing, the exoplasmic surface shows a triplet structure which exactly fits the projected structure determined by Unwin and Henderson (1975. Nature(Lond.). 257:28-32) at molecular resolution, whereas, on the plasmatic surface, four image details per unit cell are visible. Three of them match the arrangement of bacteriorhodopsin, whereas the fourth must be located over a lipidic array. Summarizing these results, it is possible to show the part of each single bacteriorhodopsin protein that is present in the surfaces of the purple membrane. By "shadowing" the membranes perpendicularly, we prove that these components of the surfaces are mainly portrayed by a decoration effect of the tantalum/tungsten condensate. PMID:7251671

  7. Uniqueness of SRB measures for transitive diffeomorphisms on surfaces

    OpenAIRE

    Hertz, F. Rodriguez; Hertz, M. A. Rodriguez; Tahzibi, A.; Ures, R.

    2010-01-01

    We give a description of ergodic components of SRB measures in terms of ergodic homoclinic classes associated to hyperbolic periodic points. For transitive surface diffeomorphisms, we prove that there exists at most one SRB measure.

  8. Surface Micromachined Arrays of Transition-Edge Detectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An innovative surface micromachining technique is described for the fabrication of closely-packed arrays of transition edge sensor (TES) x-ray microcalorimeters....

  9. Methanol Oxidation on Model Elemental and Bimetallic Transition Metal Surfaces

    DEFF Research Database (Denmark)

    Tritsaris, G. A.; Rossmeisl, J.

    2012-01-01

    Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, flat...... sites on the surface and to screen for novel bimetallic surfaces of enhanced activity. We suggest platinum copper surfaces as promising anode catalysts for direct methanol fuel cells....

  10. Surface segregation energies in transition-metal alloys

    DEFF Research Database (Denmark)

    Ruban, Andrei; Skriver, Hans Lomholt; Nørskov, Jens Kehlet

    1999-01-01

    We present a database of 24 x 24 surface segregation energies of single transition metal impurities in transition-metal hosts obtained by a Green's-function linear-muffin-tin-orbitals method in conjunction with the coherent potential and atomic sphere approximations including a multipole correction...... to the electrostatic potential and energy. We use the database to establish the major factors which govern surface segregation in transition metal alloys. We find that the calculated trends are well described by Friedel's rectangular state density model and that the few but significant deviations from the simple...

  11. Optimization of Freeze-Drying Process Parameters for Qualitative Evaluation of Button Mushroom (Agaricus bisporus Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Ayon Tarafdar

    2017-01-01

    Full Text Available Button mushroom cubes of constant cross-sectional area (0.75 cm × 1.5 cm and varying thickness (2 mm, 5 mm, and 8 mm were freeze-dried. Pressure (0.04, 0.07, and 0.10 mbar, primary drying temperature (−2°C, −5°C, and −8°C, and secondary drying temperature (25°C, 28°C, and 31°C were taken as drying parameters. The protein, ascorbic acid, and antioxidant contents were taken as quality estimates for freeze-dried mushrooms. It was observed that the secondary drying temperature affected the protein (p<0.05 and antioxidant content (p<0.01 significantly, whereas all three freeze-drying parameters affected the ascorbic acid content with higher effect due to temperature parameters (p<0.01 as compared to pressure (p<0.05. The optimized values for protein, ascorbic acid, and antioxidant content obtained using response surface methodology were 7.28±0.56 mg/g, 26.92±0.87 mg/100 g, and 8.60±0.44 mg/g, respectively, as compared to 8.43±0.21 mg/g, 28.00±0.53 mg/100 g, and 9.10±0.10 mg/g, respectively, for fresh button mushrooms. The optimum values for process variables were obtained as 0.09 mbar, 0.36 cm, and −7.53°C and 25.03°C for pressure, sample thickness, and primary and secondary drying temperatures, respectively.

  12. Wettability transition of laser textured brass surfaces inside different mediums

    Science.gov (United States)

    Yan, Huangping; Abdul Rashid, Mohamed Raiz B.; Khew, Si Ying; Li, Fengping; Hong, Minghui

    2018-01-01

    Hydrophobic surface on brass has attracted intensive attention owing to its importance in scientific research and practical applications. Laser texturing provides a simple and promising method to achieve it. Reducing wettability transition time from hydrophilicity to hydrophobicity or superhydrophobicity remains a challenge. Herein, wettability transition of brass surfaces with hybrid micro/nano-structures fabricated by laser texturing was investigated by immersing the samples inside different mediums. Scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy and surface contact angle measurement were employed to characterize surface morphology, chemical composition and wettability of the fabricated surfaces of brass samples. Wettability transition time from hydrophilicity to hydrophobicity was shortened by immersion into isopropyl alcohol for a period of 3 h as a result of the absorption and accumulation of organic substances on the textured brass surface. When the textured brass sample was immersed into sodium bicarbonate solution, flower-like structures on the sample surface played a key role in slowing down wettability transition. Moreover, it had the smallest steady state contact angle as compared to the others. This study provides a facile method to construct textured surfaces with tunable wetting behaviors and effectively extend the industrial applications of brass.

  13. Dilution in Transition Zone between Rising Plumes and Surface Plumes

    DEFF Research Database (Denmark)

    Larsen, Torben

    2004-01-01

    The papers presents some physical experiments with the dilution of sea outfall plumes with emphasize on the transition zone where the relative fast flowing vertical plume turns to a horizontal surface plume following the slow sea surface currents. The experiments show that a considerable dilution...

  14. Direct NO decomposition over stepped transition-metal surfaces

    DEFF Research Database (Denmark)

    Falsig, Hanne; Bligaard, Thomas; Christensen, Claus H.

    2007-01-01

    We establish the full potential energy diagram for the direct NO decomposition reaction over stepped transition-metal surfaces by combining a database of adsorption energies on stepped metal surfaces with known Bronsted-Evans-Polanyi (BEP) relations for the activation barriers of dissociation...

  15. Surface relaxation and stress for 5d transition metals

    Science.gov (United States)

    Zólyomi, V.; Vitos, L.; Kwon, S. K.; Kollár, J.

    2009-03-01

    Using the density functional theory, we present a systematic theoretical study of the layer relaxation and surface stress of 5d transition metals. Our calculations predict layer contractions for all surfaces, except for the (111) surface of face centered cubic Pt and Au, where slight expansions are obtained similarly to the case of the 4d series. We also find that the relaxations of the close packed surfaces decrease with increasing occupation number through the 5d series. The surface stress for the relaxed, most closely packed surfaces shows similar atomic number dependence as the surface energy. Using Cammarata's model and our calculated surface stress and surface energy values, we examine the possibility of surface reconstructions, which is in reasonable agreement with the experimental observations.

  16. Optimisation of phenolic extraction from Averrhoa carambola pomace by response surface methodology and its microencapsulation by spray and freeze drying.

    Science.gov (United States)

    Saikia, Sangeeta; Mahnot, Nikhil Kumar; Mahanta, Charu Lata

    2015-03-15

    Optimised of the extraction of polyphenol from star fruit (Averrhoa carambola) pomace using response surface methodology was carried out. Two variables viz. temperature (°C) and ethanol concentration (%) with 5 levels (-1.414, -1, 0, +1 and +1.414) were used to design the optimisation model using central composite rotatable design where, -1.414 and +1.414 refer to axial values, -1 and +1 mean factorial points and 0 refers to centre point of the design. The two variables, temperature of 40°C and ethanol concentration of 65% were the optimised conditions for the response variables of total phenolic content, ferric reducing antioxidant capacity and 2,2-diphenyl-1-picrylhydrazyl scavenging activity. The reverse phase-high pressure liquid chromatography chromatogram of the polyphenol extract showed eight phenolic acids and ascorbic acid. The extract was then encapsulated with maltodextrin (⩽ DE 20) by spray and freeze drying methods at three different concentrations. Highest encapsulating efficiency was obtained in freeze dried encapsulates (78-97%). The obtained optimised model could be used for polyphenol extraction from star fruit pomace and microencapsulates can be incorporated in different food systems to enhance their antioxidant property. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Anti-icing properties of a superhydrophobic surface in a salt environment: an unexpected increase in freezing delay times for weak brine droplets.

    Science.gov (United States)

    Boinovich, Ludmila B; Emelyanenko, Alexandre M; Emelyanenko, Kirill A; Maslakov, Konstantin I

    2016-01-28

    Superhydrophobic coatings on the aluminum alloy were fabricated by intensive nanosecond pulsed laser treatment and chemical surface hydrophobization, which are chemically stable in contact with 0.5 M NaCl aqueous solutions and mechanically durable against stresses arising in the repetitive freezing/thawing of brine. The statistics of the crystallization of ensembles of sessile supercooled droplets deposited on above superhydrophobic coatings indicate considerable anti-icing properties. The comparative analysis of crystallization statistics of deionized water and of brine at a temperature of -20 °C allows detecting a striking increase in freezing delay times for the latter case with freezing delay for brine droplets reaching more than 6 hours. We explain the observed phenomenon based on the structure of the double electric layer in the vicinity of the hydrophobic surface and the solution/air interface and on the concept of structure making/breaking ions.

  18. Phase transitions and adsorbate restructuring at metal surface

    CERN Document Server

    King, DA

    1994-01-01

    The objective in initiating this series in 1980 was to provide an in-depth review of advances made in the understanding key aspects of surface chemistry and physics through the application of new techniques to the study of well-defined surfaces. Since then the field of surface science has greatly matured, and further important techniques, particularly scanning probe microscopies, have been successfully assimilated into the applications armoury of the surface scientist. The present volume is a series of timely reviews by many of the current experts in the field of phase transitions an

  19. Hydrophobic durability characteristics of butterfly wing surface after freezing cycles towards the design of nature inspired anti-icing surfaces.

    Science.gov (United States)

    Chen, Tingkun; Cong, Qian; Qi, Yingchun; Jin, Jingfu; Choy, Kwang-Leong

    2018-01-01

    The hydrophobicity and anti-icing performance of the surfaces of some artificial hydrophobic coatings degraded after several icing and de-icing cycles. In this paper, the frost formation on the surfaces of butterfly wings from ten different species was observed, and the contact angles were measured after 0 to 6 frosting/defrosting cycles. The results show that no obvious changes in contact angle for the butterfly wing specimens were not obvious during the frosting/defrosting process. Further, the conclusion was inferred that the topography of the butterfly wing surface forms a special space structure which has a larger space inside that can accommodate more frozen droplets; this behavior prevents destruction of the structure. The findings of this study may provide a basis and new concepts for the design of novel industrially important surfaces to inhibit frost/ice growth, such as durable anti-icing coatings, which may decrease or prevent the socio-economic loss.

  20. Suppression of sub-surface freezing in free-standing thin films of a coarse-grained model of water.

    Science.gov (United States)

    Haji-Akbari, Amir; DeFever, Ryan S; Sarupria, Sapna; Debenedetti, Pablo G

    2014-12-21

    Freezing in the vicinity of water-vapor interfaces is of considerable interest to a wide range of disciplines, most notably the atmospheric sciences. In this work, we use molecular dynamics and two advanced sampling techniques, forward flux sampling and umbrella sampling, to study homogeneous nucleation of ice in free-standing thin films of supercooled water. We use a coarse-grained monoatomic model of water, known as mW, and we find that in this model a vapor-liquid interface suppresses crystallization in its vicinity. This suppression occurs in the vicinity of flat interfaces where no net Laplace pressure in induced. Our free energy calculations reveal that the pre-critical crystalline nuclei that emerge near the interface are thermodynamically less stable than those that emerge in the bulk. We investigate the origin of this instability by computing the average asphericity of nuclei that form in different regions of the film, and observe that average asphericity increases closer to the interface, which is consistent with an increase in the free energy due to increased surface-to-volume ratios.

  1. Novel Combined Freeze-Drying and Instant Controlled Pressure Drop Drying for Restructured Carrot-Potato Chips: Optimized by Response Surface Method

    OpenAIRE

    Yi, Jianyong; Hou, Chunhui; Bi, Jinfeng; Zhao, Yuanyuan; Peng, Jian; Liu, Changjin

    2018-01-01

    Combined freeze-drying and instant controlled pressure drop process (FD-DIC) for restructured carrot-potato chips was developed and its processing conditions were optimized using response surface methodology (RSM) with the purpose of improving the quality of products and reducing energy consumption. Three critical variables including the amount of carrot, the moisture content of the partially dried product before DIC treatment, and equilibrium temperature of DIC for the restructured chips wer...

  2. Surface entropy of liquid transition and noble metals

    Science.gov (United States)

    Gosh, R. C.; Das, Ramprosad; Sen, Sumon C.; Bhuiyan, G. M.

    2015-07-01

    Surface entropy of liquid transition and noble metals has been investigated using an expression obtained from the hard-sphere (HS) theory of liquid. The expression is developed from the Mayer's extended surface tension formula [Journal of Non-Crystalline Solids 380 (2013) 42-47]. For interionic interaction in metals, Brettonet-Silbert (BS) pseudopotentials and embedded atom method (EAM) potentials have been used. The liquid structure is described by the variational modified hypernetted chain (VMHNC) theory. The essential ingredient of the expression is the temperature dependent effective HS diameter (or packing fraction), which is calculated from the aforementioned potentials together with the VMHNC theory. The obtained results for the surface entropy using the effective HS diameter are found to be good in agreement with the available experimental as well as other theoretical values.

  3. Electron Scattering at Surfaces and Interfaces of Transition Metals

    Science.gov (United States)

    Zheng, Pengyuan

    The effect of surfaces on the electron transport at reduced scales is attracting continuous interest due to its broad impact on both the understanding of materials properties and their application for nanoelectronics. The size dependence of for conductor's electrical resistivity rho due to electron surface scattering is most commonly described within the framework of Fuchs and Sondheimer (FS) and their various extensions, which uses a phenomenological scattering parameter p to define the probability of electrons being elastically (i.e. specularly) scattered by the surface without causing an increase of rho at reduced size. However, a basic understanding of what surface chemistry and structure parameters determine the specularity p is still lacking. In addition, the assumption of a spherical Fermi surface in the FS model is too simple for transition metals to give accurate account of the actual surface scattering effect. The goal of this study is to develop an understanding of the physics governing electron surface/interface scattering in transition metals and to study the significance of their Fermi surface shape on surface scattering. The advancement of the scientific knowledge in electron surface and interface scattering of transition metals can provide insights into how to design high-conductivity nanowires that will facilitate the viable development of advanced integrated circuits, thermoelectric power generation and spintronics. Sequential in situ and ex situ transport measurements as a function of surface chemistry demonstrate that electron surface/interface scattering can be engineered by surface doping, causing a decrease in the rho. For instance, the rho of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11--13% when coated with 0.75 nm Ni. This is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces

  4. Influence of Surface Morphology on the Antimicrobial Effect of Transition Metal Oxides in Polymer Surface.

    Science.gov (United States)

    Oh, Yoo Jin; Hubauer-Brenner, Michael; Hinterdorfer, Peter

    2015-10-01

    In this study, the physical properties of transition metal oxide surfaces were examined using scanning probe microscopic (SPM) techniques for elucidating the antimicrobial activity of molybdenum trioxide (MoO3), tungsten trioxide (WO3), and zinc oxide (ZnO) embedded into the polymers thermoplastic polyurethane (TPU) and polypropylene (PP). We utilized atomic force microscopy (AFM) in the contact imaging mode and its derivative single-pass Kelvin probe force microscopy for investigating samples that were presumably identical in their compositions, but showed different antimicrobial activity in bacterial adhesion tests. Our results revealed that surfaces with larger roughness and higher surface potential variation showed stronger antimicrobial activities compared to smoother and homogeneously charge-distributed surfaces. In addition, capacitance gradient (dC/dZ) measurements were performed to elucidate the antimicrobial activity arising from the different dielectric behavior of the transition metal oxides in this heterogeneous polymer surface. We found that the nano-scale exposure of transition metal oxides on polymer surfaces provided strong antimicrobial effects. Applications arising from our studies will be useful for public and healthcare environments.

  5. Temporal Monitoring of the Soil Freeze-Thaw Cycles over a Snow-Covered Surface by Using Air-Launched Ground-Penetrating Radar

    Directory of Open Access Journals (Sweden)

    Khan Zaib Jadoon

    2015-09-01

    Full Text Available We tested an off-ground ground-penetrating radar (GPR system at a fixed location over a bare agricultural field to monitor the soil freeze-thaw cycles over a snow-covered surface. The GPR system consisted of a monostatic horn antenna combined with a vector network analyzer, providing an ultra-wideband stepped-frequency continuous-wave radar. An antenna calibration experiment was performed to filter antenna and back scattered effects from the raw GPR data. Near the GPR setup, sensors were installed in the soil to monitor the dynamics of soil temperature and dielectric permittivity at different depths. The soil permittivity was retrieved via inversion of time domain GPR data focused on the surface reflection. Significant effects of soil dynamics were observed in the time-lapse GPR, temperature and dielectric permittivity measurements. In particular, five freeze and thaw events were clearly detectable, indicating that the GPR signals respond to the contrast between the dielectric permittivity of frozen and thawed soil. The GPR-derived permittivity was in good agreement with sensor observations. Overall, the off-ground nature of the GPR system permits non-invasive time-lapse observation of the soil freeze-thaw dynamics without disturbing the structure of the snow cover. The proposed method shows promise for the real-time mapping and monitoring of the shallow frozen layer at the field scale.

  6. Temporal Monitoring of the Soil Freeze-Thaw Cycles over a Snow-Covered Surface by Using Air-Launched Ground-Penetrating Radar

    KAUST Repository

    Jadoon, Khan

    2015-09-18

    We tested an off-ground ground-penetrating radar (GPR) system at a fixed location over a bare agricultural field to monitor the soil freeze-thaw cycles over a snow-covered surface. The GPR system consisted of a monostatic horn antenna combined with a vector network analyzer, providing an ultra-wideband stepped-frequency continuous-wave radar. An antenna calibration experiment was performed to filter antenna and back scattered effects from the raw GPR data. Near the GPR setup, sensors were installed in the soil to monitor the dynamics of soil temperature and dielectric permittivity at different depths. The soil permittivity was retrieved via inversion of time domain GPR data focused on the surface reflection. Significant effects of soil dynamics were observed in the time-lapse GPR, temperature and dielectric permittivity measurements. In particular, five freeze and thaw events were clearly detectable, indicating that the GPR signals respond to the contrast between the dielectric permittivity of frozen and thawed soil. The GPR-derived permittivity was in good agreement with sensor observations. Overall, the off-ground nature of the GPR system permits non-invasive time-lapse observation of the soil freeze-thaw dynamics without disturbing the structure of the snow cover. The proposed method shows promise for the real-time mapping and monitoring of the shallow frozen layer at the field scale.

  7. Optimization of thermophysical properties of Pacific white shrimp (Litopenaeus vannamei) previously treated with freezing-point regulators using response surface methodology.

    Science.gov (United States)

    Wang, Liang; Liu, Zunying; Zhao, Yuanhui; Dong, Shiyuan; Zeng, Mingyong; Yang, Huicheng

    2015-08-01

    Three freezing-point regulators (glycine, sodium chloride and D-sorbitol) were employed to optimize thermophysical properties of Pacific white shrimp (Litopenaeus vannamei) using response surface methodology (RSM). The independent variables were glycine content (0.250-1.250 %), sodium chloride content (0.500-2.500 %) and D-sorbitol content (0.125-0.625 %) and analysis of variance showed that the effects of glycine, sodium chloride and D-sorbitol on the thermophysical properties were statistically significant (P freezing point (T i ), unfreezable water mass fraction (W u ), apparent specific heat (C app ) and Enthalpy (H) were 0.896 ~ 0.999. The combined effects of these independent variables on T i , W u , C app and H were investigated. The results indicated that T i , C app and H varied curvilinearly with increasing of glycine, sodium chloride and D-sorbitol content whereas W u increased nearly linearly. Based on response plots and desirability functions, the optimum combination of process variables for Pacific white shrimp previously treated with freezing-point regulators were 0.876 % for glycine content, 2.298 % for sodium chloride content and 0.589 % for D-sorbitol content, correspondently the optimized thermophysical properties were T i , - 5.086 °C; W u , 17.222 %; C app , 41.038 J/g °C and H, 155.942 J/g, respectively. Briefly, the application of freezing-point regulators depressed T i and obtained the optimum W u , C app and H, which would be obviously beneficial for the exploitation of various thermal processing and food storage.

  8. The effects of formulation and moisture on the stability of a freeze-dried monoclonal antibody-vinca conjugate: a test of the WLF glass transition theory.

    Science.gov (United States)

    Roy, M L; Pikal, M J; Rickard, E C; Maloney, A M

    1992-01-01

    Deacetylvinblastine (DAVLB) hydrazide, a cytotoxic vinca alkaloid, has been linked to the monoclonal antibody, KS1/4, via aldehyde residues of the oxidized carbohydrate groups on the antibody. The resulting KS1/4-DAVLB hydrazide conjugate is unstable in solution with both the acyl hydrazone linkage and the vinca moiety being subject to significant degradation, even at 5 degrees C. This necessitated the development of a freeze-dried formulation of the antibody-drug conjugate. Formulation factors considered were pH, ionic strength, buffer, excipient types, and excipient ratios. A formulation with equal weight ratios of mannitol, glycine, and conjugate in a low ionic strength phosphate buffer at near neutral pH was selected. Stability was studied at various moisture levels (1.4%, 3.0%, and 4.7%) and temperatures (5 degrees C, 25 degrees C, and 40 degrees C). Degradation was measured by size exclusion HPLC (aggregate formation) and by reverse phase HPLC (hydrolysis of hydrazone linkage and vinca decomposition). Differential scanning calorimetry (DSC) indicated that all samples were above their glass transition temperatures, Tg, when stored at 40 degrees C. When stored at 25 degrees C, only the highest moisture sample was initially above its Tg. However, due to crystallization of the excipients during storage and the resulting decrease in Tg, samples stored at 25 degrees C were also above their Tg during much of the storage period. The degradation rate, R, increased sharply with increasing temperature and with increasing moisture level. Degradation kinetics obeyed the Williams-Landel-Ferry relationship, R/Rg = exp[k(T-Tg)], where Rg is the degradation rate at Tg. For all three moisture levels and all three degradation pathways, k = 0.143.

  9. A new approach to define surface/sub-surface transition in gravel beds

    Science.gov (United States)

    Haynes, Heather; Ockelford, Anne-Marie; Vignaga, Elisa; Holmes, William

    2012-12-01

    The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.

  10. Theory of magnetic transition metal nanoclusters on surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lounis, S.

    2007-04-17

    This thesis is motivated by the quest for the understanding and the exploration of complex magnetism provided by atomic scale magnetic clusters deposited on surfaces or embedded in the bulk. Use is made of the density functional theory (DFT). Acting within this framework, we have developed and implemented the treatment of non-collinear magnetism into the Juelich version of the full-potential Korringa-Kohn-Rostoker Green Function (KKR-GF) method. Firstly, the method was applied to 3d transition-metal clusters on different ferromagnetic surfaces. Different types of magnetic clusters where selected. In order to investigate magnetic frustration due to competing interactions within the ad-cluster we considered a (001) oriented surface of fcc metals, a topology which usually does not lead to non-collinear magnetism. We tuned the strength of the magnetic coupling between the ad-clusters and the ferromagnetic surface by varying the substrate from the case of Ni(001) with a rather weak hybridization of the Ni d-states with the adatom d-states to the case of Fe{sub 3ML}/Cu(001) with a much stronger hybridization due to the larger extend of the Fe wavefunctions. On Ni(001), the interaction between the Cr- as well as the Mn-dimer adatoms is of antiferromagnetic nature, which is in competition with the interaction with the substrate atoms. After performing total energy calculations we find that for Cr-dimer the ground state is collinear whereas the Mn-dimer prefers the non-collinear configuration as ground state. Bigger clusters are found to be magnetically collinear. These calculations were extended to 3d multimers on Fe{sub 3ML}/Cu(001). All neighboring Cr(Mn) moments in the compact tetramer are antiferromagnetically aligned in-plane, with the directions slightly tilted towards (outwards from) the substrate to gain some exchange interaction energy. The second type of frustration was investigated employing a Ni(111) surface, a surface with a triangular lattice of atoms, were

  11. Hydrogen collisions with transition metal surfaces: Universal electronically nonadiabatic adsorption

    Science.gov (United States)

    Dorenkamp, Yvonne; Jiang, Hongyan; Köckert, Hansjochen; Hertl, Nils; Kammler, Marvin; Janke, Svenja M.; Kandratsenka, Alexander; Wodtke, Alec M.; Bünermann, Oliver

    2018-01-01

    Inelastic scattering of H and D atoms from the (111) surfaces of six fcc transition metals (Au, Pt, Ag, Pd, Cu, and Ni) was investigated, and in each case, excitation of electron-hole pairs dominates the inelasticity. The results are very similar for all six metals. Differences in the average kinetic energy losses between metals can mainly be attributed to different efficiencies in the coupling to phonons due to the different masses of the metal atoms. The experimental observations can be reproduced by molecular dynamics simulations based on full-dimensional potential energy surfaces and including electronic excitations by using electronic friction in the local density friction approximation. The determining factors for the energy loss are the electron density at the surface, which is similar for all six metals, and the mass ratio between the impinging atoms and the surface atoms. Details of the electronic structure of the metal do not play a significant role. The experimentally validated simulations are used to explore sticking over a wide range of incidence conditions. We find that the sticking probability increases for H and D collisions near normal incidence—consistent with a previously reported penetration-resurfacing mechanism. The sticking probability for H or D on any of these metals may be represented as a simple function of the incidence energy, Ein, metal atom mass, M, and incidence angle, 𝜗i n. S =(S0+a ṡEi n+b ṡM ) *(1 -h (𝜗i n-c ) (1 -cos(𝜗 i n-c ) d ṡh (Ei n-e ) (Ei n-e ) ) ) , where h is the Heaviside step function and for H, S0 = 1.081, a = -0.125 eV-1, b =-8.40 ṡ1 0-4 u-1, c = 28.88°, d = 1.166 eV-1, and e = 0.442 eV; whereas for D, S0 = 1.120, a = -0.124 eV-1, b =-1.20 ṡ1 0-3 u-1, c = 28.62°, d = 1.196 eV-1, and e = 0.474 eV.

  12. Noncollinear magnetism in surfaces and interfaces of transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Huahai

    2009-09-15

    Noncollinear (NC) magnetism is common in nature, especially when there exist geometrical frustration and chemical imparity in the system. In this work we studied the NC magnetism and the response to external magnetic fields in surfaces and interfaces of transition metals by using an semi-empirical tight-binding (TB) method that parameterized to the ab initio TB-LMTO calculations. We implemented this method to study two systems. The first one is the system of 6 Mn monolayers on Fe(001) substrate. Due to the complex structure and magnetic properties of Mn, we found 23 collinear magnetic configurations but only one NC configuration. The collinear ground state has a layered antiferromagnetic (AFM) coupling which agrees with previous experiments and calculations. In the NC configuration the local AFM coupling in the Mn layers is preserved, but the surface is 90 degree coupled to the substrate. Similar to the experiment in CdCr{sub 2}O{sub 4}, we obtained a collinear plateau in the NC evolution of the average magnetic moment in Mn slab under external magnetic fields. Another is the system of a Cr monolayer on a stepped Fe(001) substrate. As expected, the local AFM coupling in the interface of Cr and Fe are preserved. However, the edge Cr atoms is about 90 coupled to their nearest Fe neighbors. We also simulated the procedure of adding more Cr coverages gradually to a Cr bilayer coverage. As coverages increase, the magnetic moments in the Cr interface reduce, and the collinear plateau becomes wider as coverages increase. However, the saturation fields in both the two systems are extremely high, around 10 kT.We expect that when the effect of temperature is taken into account, and in some proper systems, the saturation fields could be largely reduced to the scale that can be implemented in experiment, and our study may shed light on information storage devices with ultrahigh storage density. (orig.)

  13. Surface modification of nanoclays by catalytically active transition metal ions.

    Science.gov (United States)

    Nawani, Pranav; Gelfer, Mikhail Y; Hsiao, Benjamin S; Frenkel, Anatoly; Gilman, Jeffrey W; Khalid, Syed

    2007-09-11

    A unique class of nanoclays was prepared by modification of pristine clays or organoclays (Cloisite C20A) with transition metal ions (TMIs). The composition, structure, morphology and thermal properties of TMI-modified nanoclays were investigated by atomic absorption spectroscopy (AAS), elemental analysis (EA), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray absorption near-edge structure (XANES) spectroscopy. The content of TMIs in modified clays was found to be close to the limiting value of ion exchange capacity. SEM and X-ray results confirmed that TMIs were located between the mineral layers instead of being adsorbed on the surface of clay particles. TGA results indicated that the TMI treatment of organoclays could significantly increase the thermal stability, which was more pronounced in air than in nitrogen. Temperature-resolved SAXS measurements revealed that the presence of TMIs increased the onset temperature of structural degradation. The higher thermal stability of TMI-modified organoclays can be attributed to the change in the thermal degradation mechanism, resulting in a decrease in the yield of volatile products and the formation of char facilitated by the presence of catalytically active TMIs.

  14. Surface Modification of Nanoclays by Catalytically Active Transition Metal Ions

    Energy Technology Data Exchange (ETDEWEB)

    Nawani,P.; Gelfer, M.; Hsiao, B.; Frenkel, A.; Gilman, J.; Khalid, S.

    2007-01-01

    A unique class of nanoclays was prepared by modification of pristine clays or organoclays (Cloisite C20A) with transition metal ions (TMIs). The composition, structure, morphology and thermal properties of TMI-modified nanoclays were investigated by atomic absorption spectroscopy (AAS), elemental analysis (EA), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray absorption near-edge structure (XANES) spectroscopy. The content of TMIs in modified clays was found to be close to the limiting value of ion exchange capacity. SEM and X-ray results confirmed that TMIs were located between the mineral layers instead of being adsorbed on the surface of clay particles. TGA results indicated that the TMI treatment of organoclays could significantly increase the thermal stability, which was more pronounced in air than in nitrogen. Temperature-resolved SAXS measurements revealed that the presence of TMIs increased the onset temperature of structural degradation. The higher thermal stability of TMI-modified organoclays can be attributed to the change in the thermal degradation mechanism, resulting in a decrease in the yield of volatile products and the formation of char facilitated by the presence of catalytically active TMIs.

  15. Laser surface alloying of aluminium-transition metal alloys

    Directory of Open Access Journals (Sweden)

    Almeida, A.

    1998-04-01

    Full Text Available Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM alloys. Cr and Mo are particularly interesting alloying elements to produce stable highstrength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO2 laser. This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloys, over the last years.

    En el presente trabajo se estudia la aleación superficial mediante láser de aluminio con metales de transición. El cromo y el molibdeno son particularmente interesantes porque producen aleaciones de alta resistencia y por el bajo coeficiente de difusión y solución sólida en aluminio. Para producir estas aleaciones se ha seguido un procedimiento desarrollado en dos partes. En primer lugar, el material se alea usando una baja velocidad de procesado y en segundo lugar la estructura se modifica mediante un refinamiento posterior. Este procedimiento se ha empleado en la producción de aleaciones Al-Cr, Al-Mo y Al-Nb mediante aleación con láser de CO2 de polvos de Cr, Mo o Nb en aluminio y la aleación 7175. Este trabajo es una revisión del desarrollado en el Instituto Superior Técnico de Lisboa en los últimos años.

  16. Transition from diffusive to localized regimes in surface corrugated waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Martin, A.; Saenz, J. J. [Universidad Autonoma de Madrid, Madrid (Spain); Nieto-Vesperinas, M. [Instituto de Ciencias de Materiales de Madrid, Madrid (Spain)

    2001-03-01

    Exact calculations of transmission and reflection coefficients in surface randomly corrugated waveguides are presented. The elastic scattering of diffuse light classical waves from a rough surface induces a diffusive transport along the waveguide axis. As the length of the corrugated part of the waveguide increases, a transition from the diffusive to the localized regime is observed. This involves an analogy with electron conduction in nano wires, and hence, a concept analogous to that of resistance can be introduced. An oscillatory behavior of different transport properties (elastic mean free path, localization length, enhanced backscattering), versus the wavelength is predicted. An analysis of the transmission coefficients (transmitted speckle) shows that as the length of the corrugated part of the waveguide increases there is a strong preference to forward coupling through the lowest mode. This marks a clear anisotropy in the forward propagation which is absent in the case of volume disorder. The statistics of reflection coefficients is analyzed, first using random matrix theory (Rm) to analytically deduce the probability densities in the localization regime, afterwards exact numerical calculations of the coupling to backward modes in surface corrugated waveguides will be put forward for comparison. We show that the reflected speckle distribution are independent of the transport regime, at variance with the regime transition found in the transmission case. Despite the strong anisotropy, the analysis of the probability distributions of both transmitted and reflected waves confirms the distributions predicted by Random Matrix Theory for volume disorder. [Spanish] Presentamos calculos exactos de los coeficientes de transmision y reflexion en guias de onda con desorden de superficie. La dispersion elastica de luz difusa o de otras ondas clasicas por una superficie rugosa induce un transporte difusivo a lo largo del eje de la guia. A medida que la longitud de la zona

  17. Dissociation of N2, NO, and CO on transition metal surfaces

    DEFF Research Database (Denmark)

    Mavrikakis, Manos; Hansen, Lars Bruno; Mortensen, Jens Jørgen

    1999-01-01

    Using density functional theory we study the dissociation of N2, NO, and CO on transition metal surfaces. We discuss an efficient method to locate the minimum energy path and the transition state, and review recent calculations using this method to determine the transition state for dissociation...... of N2 on Ru(0001) and NO on Pd(111), Pd(211), and Rh(111) surfaces. We also show how steps and adsorbed alkali metal atoms can significantly decrease the dissociation barrier. Finally, trends in the properties of the transition state for N2, NO and CO dissociation on transition metals are discussed...

  18. Surface analysis of transition metal oxalates: Damage aspects

    Energy Technology Data Exchange (ETDEWEB)

    Chenakin, S.P., E-mail: chenakin@imp.kiev.ua [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, B-1050 Bruxelles (Belgium); Institute of Metal Physics, Nat. Acad. Sci. of Ukraine, Akad. Vernadsky Blvd. 36, 03680 Kiev (Ukraine); Szukiewicz, R. [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, B-1050 Bruxelles (Belgium); Barbosa, R.; Kruse, N. [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, B-1050 Bruxelles (Belgium); Voiland School of Chemical Engineering and Bioengineering, Washington State University, 155 Wegner Hall, Pullman, WA 99164-6515 (United States)

    2016-05-15

    Highlights: • Gas evolution from the Mn, Co, Ni and Cu oxalate hydrates in vacuum, during exposure to X-rays and after termination of X-ray irradiation is studied. • A comparative study of the damage caused by X-rays in NiC{sub 2}O{sub 4} and CuC{sub 2}O{sub 4} is carried out. • Effect of Ar{sup +} bombardment on the structure and composition of CoC{sub 2}O{sub 4} is studied. - Abstract: The behavior of transition metal oxalates in vacuum, under X-ray irradiation and low-energy Ar{sup +} ion bombardment was studied. A comparative mass-spectrometric analysis was carried out of gas evolution from the surface of Mn, Co, Ni and Cu oxalate hydrates in vacuum, during exposure to X-rays and after termination of X-ray irradiation. The rates of H{sub 2}O and CO{sub 2} liberation from the oxalates were found to be in an inverse correlation with the temperatures of dehydration and decomposition, respectively. X-ray photoelectron spectroscopy (XPS) was employed to study the X-ray induced damage in NiC{sub 2}O{sub 4} and CuC{sub 2}O{sub 4} by measuring the various XP spectral characteristics and surface composition of the oxalates as a function of time of exposure to X-rays. It was shown that Cu oxalate underwent a significantly faster degradation than Ni oxalate and demonstrated a high degree of X-ray induced reduction from the Cu{sup 2+} to the Cu{sup 1+} chemical state. 500 eV Ar{sup +} sputter cleaning of CoC{sub 2}O{sub 4} for 10 min was found to cause a strong transformation of the oxalate structure which manifested itself in an appreciable alteration of the XP core-level and valence band spectra. The analysis of changes in stoichiometry and comparison of XP spectra of bombarded oxalate with respective spectra of a reference carbonate CoCO{sub 3} implied that the bombardment-induced decomposition of CoC{sub 2}O{sub 4} gave rise to the formation of CoO-like and disordered CoCO{sub 3}-like phases.

  19. Trends in catalytic NO decomposition over transition metal surfaces

    DEFF Research Database (Denmark)

    Falsig, Hanne; Bligaard, Thomas; Rass-Hansen, Jeppe

    2007-01-01

    The formation of NOx from combustion of fossil and renewable fuels continues to be a dominant environmental issue. We take one step towards rationalizing trends in catalytic activity of transition metal catalysts for NO decomposition by combining microkinetic modelling with density functional the...

  20. X-Ray Studies of Phase Transitions on Surfaces

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1984-01-01

    The density variation across the surface from vapor to liquid in liquid crystal materials has been measured in the isotropic, nematic and smectic A phases by specular reflection of X rays with grazing angles from θc to θB (total reflection angle and Bragg angle for smectic A layering, respectively......) using synchroton X-rays in HASYLAB, Hamburg. Crystalline surface structures may be deduced from X-ray diffraction, utilizing the evanescent beam occuring for grazing angles less than θc to obtain surface sensitivity. Results from the reconstruction of Au(110) surface are reviewed....

  1. Scaling Relationships for Adsorption Energies of C2 Hydrocarbons on Transition Metal Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G

    2011-08-18

    Using density functional theory calculations we show that the adsorption energies for C{sub 2}H{sub x}-type adsorbates on transition metal surfaces scale with each other according to a simple bond order conservation model. This observation generalizes some recently recognized adsorption energy scaling laws for AH{sub x}-type adsorbates to unsaturated hydrocarbons and establishes a coherent simplified description of saturated as well as unsaturated hydrocarbons adsorbed on transition metal surfaces. A number of potential applications are discussed. We apply the model to the dehydrogenation of ethane over pure transition metal catalysts. Comparison with the corresponding full density functional theory calculations shows excellent agreement.

  2. Nanoscopy of Surface-Induced van der Waals-Zeeman Transitions

    Science.gov (United States)

    Hamamda, M.; Grucker, J.; Dutier, G.; Perales, F.; Bocvarski, V.; Baudon, J.; Ducloy, M.

    2008-10-01

    van der Waals transitions among magnetic sub-levels of a metastable rare gas atom passing near a surface immersed in a magnetic field, are described. Related transition amplitudes are calculated using both the sudden and the Landau-Zener approximations. Experimental data for Ne*(3P2) atoms traversing a copper grating are presented. For a pair of surfaces (e.g. the opposite edges of a slit) and a sufficiently large coherence width, Fresnel's biprism interference fringes are obtained. From this interference pattern, detailed information about the transition amplitude at a sub-nanometric scale can be derived. The effect of gravity on this pattern is examined.

  3. Transition States for Submerged Superhydrophobic Surfaces: Partially-Pinned Air-Water Interface

    Science.gov (United States)

    Tafreshi, Hooman; Hemeda, Ahmed; VCU Team

    2015-11-01

    The pressure at which a superhydrophobic surface transitions from the Cassie state to the Wenzel state is often referred to as the critical pressure. Our mathematical simulations have shown that the Cassie-to-Wenzel transition is a gradual process that takes place over a range of pressures as oppose to an event that happens at a certain pressure. During the transition period, the air-water interface may go through a series pinned, partially-pinned, and de-pinned states that depend on the geometry of the surface asperities. This in turn indicates that the drag-reduction effect produced by a submerged superhydrophobic surface can vary with the hydrostatic pressure, and is highly dependent on sharpness of the surface asperities. The study reported here reviews our recent discoveries in simulating the wetted area and drag reduction effect of superhydrophobic surfaces with different microstructures. National Science Foundation CMM 1029924 and CBET 1402655 programs.

  4. An effect of chemisorbing surface reaction poisons on the transition from internal to external oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Luckman, G.; Polizzotti, R.S.

    1985-01-01

    The authors consider the effect of a chemisorbing surface reaction poison on the transition from internal to external oxidation for a model binary alloy subject to selective oxidation. The authors solve the diffusion equations for internal oxidation, using the rate of a surface reaction as a boundary condition. Th gas-phase concentration of a strongly chemisorbing poison appears in the analysis through its retarding effect on that surface reaction. It is shown that the slow surface reaction can promote the formation of a protective oxide scale by slowing down the initial uptake of oxygen and allowing metal atoms with the highest oxygen affinity sufficient time to diffuse to the surface. As a result, a larger volum fraction of oxide forms near to the surface (with that volume fraction initially inversely proportional to the rate of the surface reaction), and the critical volume fraction required for the transition to an external scale is more easily exceeded.

  5. A Theory of Immersion Freezing

    Science.gov (United States)

    Barahona, Donifan

    2017-01-01

    Immersion freezing is likely involved in the initiation of precipitation and determines to large extent the phase partitioning in convective clouds. Theoretical models commonly used to describe immersion freezing in atmospheric models are based on the classical nucleation theory which however neglects important interactions near the immersed particle that may affect nucleation rates. This work introduces a new theory of immersion freezing based on two premises. First, immersion ice nucleation is mediated by the modification of the properties of water near the particle-liquid interface, rather than by the geometry of the ice germ. Second, the same mechanism that leads to the decrease in the work of germ formation also decreases the mobility of water molecules near the immersed particle. These two premises allow establishing general thermodynamic constraints to the ice nucleation rate. Analysis of the new theory shows that active sites likely trigger ice nucleation, but they do not control the overall nucleation rate nor the probability of freezing. It also suggests that materials with different ice nucleation efficiency may exhibit similar freezing temperatures under similar conditions but differ in their sensitivity to particle surface area and cooling rate. Predicted nucleation rates show good agreement with observations for a diverse set of materials including dust, black carbon and bacterial ice nucleating particles. The application of the new theory within the NASA Global Earth System Model (GEOS-5) is also discussed.

  6. Freezing and Food Safety

    Science.gov (United States)

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

  7. Trends in the chemical properties in early transition metal carbide surfaces: A density functional study

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.

    2005-01-01

    In this paper we present density functional theory (DFT) investigations of the physical, chemical and electronic structure properties of several close-packed surfaces of early transition metal carbides, including beta-Mo2C(0 0 0 1), and the (1 1 1) surfaces of TiC, VC, NbC, and TaC. The results a...

  8. A Coupled Groundwater-Surface Water Modeling Framework for Simulating Transition Zone Processes.

    Science.gov (United States)

    Mugunthan, Pradeep; Russell, Kevin T; Gong, Binglei; Riley, Michael J; Chin, Arthur; McDonald, Blair G; Eastcott, Linda J

    2017-05-01

    There is an identified need for fully representing groundwater-surface water transition zone (i.e., the sediment zone that connects groundwater and surface water) processes in modeling fate and transport of contaminants to assist with management of contaminated sediments. Most existing groundwater and surface water fate and transport models are not dynamically linked and do not consider transition zone processes such as bioturbation and deposition and erosion of sediments. An interface module is developed herein to holistically simulate the fate and transport by coupling two commonly used models, Environmental Fluid Dynamics Code (EFDC) and SEAWAT, to simulate surface water and groundwater hydrodynamics, while providing an enhanced representation of the processes in the transition zone. Transition zone and surface water contaminant processes were represented through an enhanced version of the EFDC model, AQFATE. AQFATE also includes SEDZLJ, a state-of-the-science surface water sediment transport model. The modeling framework was tested on a published test problem and applied to evaluate field-scale two- and three-dimensional contaminant transport. The model accurately simulated concentrations of salinity from a published test case. For the field-scale applications, the model showed excellent mass balance closure for the transition zone and provided accurate simulations of all transition zone processes represented in the modeling framework. The model predictions for the two-dimensional field case were consistent with site-specific observations of contaminant migration. This modeling framework represents advancement in the simulation of transition zone processes and can help inform risk assessment at sites where contaminant sources from upland areas have the potential to impact sediments and surface water. © 2016, National Ground Water Association.

  9. Oral application of freeze-dried yeast particles expressing the PCV2b Cap protein on their surface induce protection to subsequent PCV2b challenge in vivo.

    Science.gov (United States)

    Patterson, Robert; Eley, Thomas; Browne, Christopher; Martineau, Henny M; Werling, Dirk

    2015-11-17

    Porcine circovirus type 2 (PCV2) is now endemic in every major pig producing country, causing PCV-associated disease (PCVAD), linked with large scale economic losses. Current vaccination strategies are based on the capsid protein of the virus and are reasonably successful in preventing PCVAD but fail to induce sterile immunity. Additionally, vaccinating whole herds is expensive and time consuming. In the present study a "proof of concept" vaccine trial was employed to test the effectiveness of powdered freeze-dried recombinant Saccharomyces cerevisiae yeast stably expressing the capsid protein of PCV2b on its surface as an orally applied vaccine. PCV2-free pigs were given 3 doses of vaccine or left un-vaccinated before challenge with a defined PCV2b strain. Rectal temperatures were measured and serum and faeces samples were collected weekly. At the end of the study, pigs were euthanized, tissue samples taken and tested for PCV2b load by qPCR and immunohistochemistry. The peak of viraemia in sera and faeces of unvaccinated pigs was higher than that of vaccinated pigs. Additionally more sIgA was found in faeces of vaccinated pigs than unvaccinated. Vaccination was associated with lower serum concentrations of TNFα and IL-1β but higher concentrations of IFNα and IFNγ in comparison to the unvaccinated animals. At the end of the trial, a higher viral load was found in several lymphatic tissues and the ileum of unvaccinated pigs in comparison to vaccinated pigs. The difference between groups was especially apparent in the ileum. The results presented here demonstrate a possible use for recombinant S. cerevisiae expressing viral proteins as an oral vaccine against PCV2. A powdered freeze-dried recombinant S. cerevisiae used as an oral vaccine could be mixed with feed and may offer a cheap and less labour intensive alternative to inoculation with the additional advantage that no cooling chain would be required for vaccine transport and storage. Copyright © 2015 The

  10. Efficient Geometry Minimization and Transition Structure Optimization Using Interpolated Potential Energy Surfaces and Iteratively Updated Hessians.

    Science.gov (United States)

    Zheng, Jingjing; Frisch, Michael J

    2017-12-12

    An efficient geometry optimization algorithm based on interpolated potential energy surfaces with iteratively updated Hessians is presented in this work. At each step of geometry optimization (including both minimization and transition structure search), an interpolated potential energy surface is properly constructed by using the previously calculated information (energies, gradients, and Hessians/updated Hessians), and Hessians of the two latest geometries are updated in an iterative manner. The optimized minimum or transition structure on the interpolated surface is used for the starting geometry of the next geometry optimization step. The cost of searching the minimum or transition structure on the interpolated surface and iteratively updating Hessians is usually negligible compared with most electronic structure single gradient calculations. These interpolated potential energy surfaces are often better representations of the true potential energy surface in a broader range than a local quadratic approximation that is usually used in most geometry optimization algorithms. Tests on a series of large and floppy molecules and transition structures both in gas phase and in solutions show that the new algorithm can significantly improve the optimization efficiency by using the iteratively updated Hessians and optimizations on interpolated surfaces.

  11. Experimental study of the transitional flow of a sphere located at the free surface

    OpenAIRE

    James, Marion; Forrester, Alex; Hudson, Dominic; Taunton, Dominic; Turnock, Stephen

    2015-01-01

    The investigation of transitional flow past a sphere at the free surface is a challenging problem due to a complex interaction between the free surface and evolution of the boundary layer and resultant separation on the sphere’s surface. An increased knowledge about the fluid phenomena around bluff bodies would be of benefit to the design of offshore structures and ships’ bulbous bows. In this paper, experiments conducted in a towing tank environment are presented for a 225mm-diameter sphere ...

  12. Transition State Theory for solvated reactions beyond recrossing-free dividing surfaces

    OpenAIRE

    Revuelta, F.; Bartsch, Thomas; Garcia-Muller, P. L.; Hernandez, Rigoberto; Benito, R. M.; Borondo, F.

    2016-01-01

    The accuracy of rate constants calculated using transition state theory depends crucially on the correct identification of a recrossing--free dividing surface. We show here that it is possible to define such optimal dividing surface in systems with non--Markovian friction. However, a more direct approach to rate calculation is based on invariant manifolds and avoids the use of a dividing surface altogether, Using that method we obtain an explicit expression for the rate of crossing an anharmo...

  13. Photoelectron diffraction studies of molecular adsorbates on transition metal surfaces

    CERN Document Server

    Kang, J H

    2001-01-01

    Quantitative structure determinations using scanned- energy mode photoelectron diffraction are presented for three adsorption systems. For the Ni(110)/C sub 6 H sub 6 system it was determined that the benzene molecule is adsorbed above the on hollow site. The molecular plane is parallel to the surface, and the molecule is centered on a four-fold coordinated site with two opposite C-C bonds perpendicular to axis. The C-Ni nearest-neighbour layer spacing is 1.81+-0.03 A. A very high precision for the C-C distance (1.45+-0.03 A) was found and an isotropic expansion of the C-C bond lengths was confirmed. A study of the adsorption site of CO in the Ni (111)/p(2x2)-O/CO coadsorbed phase over different sample preparation temperatures revealed that the atop site is favoured. The Ni-C spacing is given by 1.77+-0.01 A. Reanalysis of old data for a surface prepared at 120 K, which is a previous analysis concluded had hcp (70 %) and fcc (30 %) site occupation, showed a mixture of hop (65 %) and atop (35 %) sites. The oc...

  14. Transition absorption as a mechanism of surface photoelectron emission from metals

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Protsenko, Igor E.; Ikhsanov, Renat Sh

    2015-01-01

    Transition absorption of a photon by an electron passingthrough a boundary between two media with different permit-tivities is described both classically and quantum mechani-cally. Transition absorption is shown to make a substantialcontribution to photoelectron emission at a metal/semicon-ductor....../semicon-ductor interface in nanoplasmonic systems, and is put forth asa possible microscopic mechanism of the surface photoelec-tric effect in photodetectors and solar cells containing plas-monic nanoparticles....

  15. Freeze chromatography method and apparatus

    Science.gov (United States)

    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.

  16. On the onset of surface condensation: formation and transition mechanisms of condensation mode.

    Science.gov (United States)

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-08-02

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the 'classical hypotheses' of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation.

  17. Numerical modeling of laboratory-scale surface-to-crown fire transition

    Science.gov (United States)

    Castle, Drew Clayton

    Understanding the conditions leading to the transition of fire spread from a surface fuel to an elevated (crown) fuel is critical to effective fire risk assessment and management. Surface fires that successfully transition to crown fires can be very difficult to suppress, potentially leading to damages in the natural and built environments. This is relevant to chaparral shrub lands which are common throughout parts of the Southwest U.S. and represent a significant part of the wildland urban interface. The ability of the Wildland-Urban Interface Fire Dynamic Simulator (WFDS) to model surface-to-crown fire transition was evaluated through comparison to laboratory experiments. The WFDS model is being developed by the U.S. Forest Service (USFS) and the National Institute of Standards and Technology. The experiments were conducted at the USFS Forest Fire Laboratory in Riverside, California. The experiments measured the ignition of chamise (Adenostoma fasciculatum) crown fuel held above a surface fire spreading through excelsior fuel. Cases with different crown fuel bulk densities, crown fuel base heights, and imposed wind speeds were considered. Cold-flow simulations yielded wind speed profiles that closely matched the experimental measurements. Next, fire simulations with only the surface fuel were conducted to verify the rate of spread while factors such as substrate properties were varied. Finally, simulations with both a surface fuel and a crown fuel were completed. Examination of specific surface fire characteristics (rate of spread, flame angle, etc.) and the corresponding experimental surface fire behavior provided a basis for comparison of the factors most responsible for transition from a surface fire to the raised fuel ignition. The rate of spread was determined by tracking the flame in the Smokeview animations using a tool developed for tracking an actual flame in a video. WFDS simulations produced results in both surface fire spread and raised fuel bed

  18. Urban Transit System Microbial Communities Differ by Surface Type and Interaction with Humans and the Environment.

    Science.gov (United States)

    Hsu, Tiffany; Joice, Regina; Vallarino, Jose; Abu-Ali, Galeb; Hartmann, Erica M; Shafquat, Afrah; DuLong, Casey; Baranowski, Catherine; Gevers, Dirk; Green, Jessica L; Morgan, Xochitl C; Spengler, John D; Huttenhower, Curtis

    2016-01-01

    Public transit systems are ideal for studying the urban microbiome and interindividual community transfer. In this study, we used 16S amplicon and shotgun metagenomic sequencing to profile microbial communities on multiple transit surfaces across train lines and stations in the Boston metropolitan transit system. The greatest determinant of microbial community structure was the transit surface type. In contrast, little variation was observed between geographically distinct train lines and stations serving different demographics. All surfaces were dominated by human skin and oral commensals such as Propionibacterium , Corynebacterium , Staphylococcus , and Streptococcus . The detected taxa not associated with humans included generalists from alphaproteobacteria, which were especially abundant on outdoor touchscreens. Shotgun metagenomics further identified viral and eukaryotic microbes, including Propionibacterium phage and Malassezia globosa . Functional profiling showed that Propionibacterium acnes pathways such as propionate production and porphyrin synthesis were enriched on train holding surfaces (holds), while electron transport chain components for aerobic respiration were enriched on touchscreens and seats. Lastly, the transit environment was not found to be a reservoir of antimicrobial resistance and virulence genes. Our results suggest that microbial communities on transit surfaces are maintained from a metapopulation of human skin commensals and environmental generalists, with enrichments corresponding to local interactions with the human body and environmental exposures. IMPORTANCE Mass transit environments, specifically, urban subways, are distinct microbial environments with high occupant densities, diversities, and turnovers, and they are thus especially relevant to public health. Despite this, only three culture-independent subway studies have been performed, all since 2013 and all with widely differing designs and conclusions. In this study, we

  19. The Turbulent-Laminar Transition on the Rocket Surface During the Injection

    Directory of Open Access Journals (Sweden)

    I. I. Yurchenko

    2014-01-01

    Full Text Available The variety of turbulent-laminar transition criteria in such environments as the launch vehicle injection points to the essential influence of spherical nose roughness, which is included in one form or another in the critical Reynolds numbers for a lot of explorers of blunt bodies. Some of researchers of the reentry bodies have founded the correlation functions between the momentum thickness Reynolds number and Max number as the transition criteria.In this article we have considered results of flight tests carried out using launch vehicles to define boundary layer regime on the payload fairing surface. The measurements were carried out using specially designed complex of gages consisted of calorimeters, surface temperature gages, and pressure gages. The turbulent-laminar transition was defined in accordance with the sharp change of calorimeter readings and flow separation pressure gages indication.The universal criterion of turbulent-laminar transition has been identified for blunted payload fairings i.e. Reynolds number Reek based on the boundary layer edge parameters in the sonic point of the payload fairing spherical nose and surface roughness height k, which gives the best correlation of all data of flight experiment conducted to define turbulent-laminar transition in boundary layer. The criterion allows defining time margins when boundary layer regime is turbulent at Reek=20±14 existing on space head surfaces and at Reek=6±5 the boundary layer regime is totally laminar.It was defined that under conditions when there are jointly high background disturbances of free stream flux at operation of main launch vehicle engines and influence of the surface roughness the critical value of Reynolds number is an order-diminished value as compared to the values obtained in wind tunnels and in free flight.It was found that with decreasing of roughness influence in growing boundary layer the flow disturbances evolution wide apart the payload fairing

  20. Surface antiferromagnetism and incipient metal-insulator transition in strained manganite films

    Science.gov (United States)

    Cossu, F.; Schwingenschlögl, U.; Colizzi, G.; Filippetti, A.; Fiorentini, Vincenzo

    2013-06-01

    Using first-principles calculations, we show that the (001) surface of the ferromagnet La0.7Sr0.3MnO3 under an epitaxial compressive strain favors antiferromagnetic (AF) order in the surface layers, coexisting with ferromagnetic (FM) bulk order. Surface antiferromagnetism is accompanied by a very marked surface-related spectral pseudogap, signaling an incomplete metal-insulator transition at the surface. The different relaxation and rumpling of the MnO2 and LaO surface planes in the two competing magnetic phases cause distinct work-function changes, which are of potential diagnostic use. The AF phase is recognized as an extreme surface-assisted case of the combination of in-plane AF super-exchange and vertical FM double-exchange couplings that rules magnetism in manganites under in-plane compression.

  1. Surface antiferromagnetism and incipient metal-insulator transition in strained manganite films

    KAUST Repository

    Cossu, Fabrizio

    2013-06-21

    Using first-principles calculations, we show that the (001) surface of the ferromagnet La0.7Sr0.3MnO3 under an epitaxial compressive strain favors antiferromagnetic (AF) order in the surface layers, coexisting with ferromagnetic (FM) bulk order. Surface antiferromagnetism is accompanied by a very marked surface-related spectral pseudogap, signaling an incomplete metal-insulator transition at the surface. The different relaxation and rumpling of the MnO2 and LaO surface planes in the two competing magnetic phases cause distinct work-function changes, which are of potential diagnostic use. The AF phase is recognized as an extreme surface-assisted case of the combination of in-plane AF super-exchange and vertical FM double-exchange couplings that rules magnetism in manganites under in-plane compression.

  2. Heat transfer and fluid mechanics measurements in transitional boundary layers on convex-curved surfaces

    Science.gov (United States)

    Wang, T.; Simon, T. W.

    1987-01-01

    The test section of the present experiment to ascertain the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii, R. Attention is given to results for the cases of R = infinity, 180 cm, and 90 cm, each with two freestream turbulence intensity levels. While the mild convex curvature of R = 180 cm delays transition, further bending to R = 90 cm leads to no signifucant further delay of transition. Cases with both curvature and higher freestream disturbance effects exhibit the latter's pronounced dominance. These data are pertinent to the development of transition prediction models for gas turbine blade design.

  3. Modification of transition's factor in the compact surface-potential-based MOSFET model

    Directory of Open Access Journals (Sweden)

    Kevkić Tijana

    2016-01-01

    Full Text Available The modification of an important transition's factor which enables continual behavior of the surface potential in entire useful range of MOSFET operation is presented. The various modifications have been made in order to obtain an accurate and computationally efficient compact MOSFET model. The best results have been achieved by introducing the generalized logistic function (GL in fitting of considered factor. The smoothness and speed of the transition of the surface potential from the depletion to the strong inversion region can be controlled in this way. The results of the explicit model with this GL functional form for transition's factor have been verified extensively with the numerical data. A great agreement was found for a wide range of substrate doping and oxide thickness. Moreover, the proposed approach can be also applied on the case where quantum mechanical effects play important role in inversion mode.

  4. Scaling relationships for adsorption energies of C2 hydrocarbons on transition metal surfaces

    DEFF Research Database (Denmark)

    Jones, Glenn; Studt, Felix; Abild-Pedersen, Frank

    2011-01-01

    Using density functional theory calculations we show that the adsorption energies for C2Hx-type adsorbates on transition metal surfaces scale with each other according to a simple bond order conservation model. This observation generalizes some recently recognized adsorption energy scaling laws f...

  5. Effects of freezing on soil temperature, freezing front propagation and moisture redistribution in peat: laboratory investigations

    Directory of Open Access Journals (Sweden)

    R. M. Nagare

    2012-02-01

    Full Text Available There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost. Soil water movement towards the freezing front (from warmer to colder regions was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.

  6. Surface science approach to heterogeneous catalysis: CO hydrogenation on transition metals

    Science.gov (United States)

    Bonzel, H. P.; Krebs, H. J.

    1982-05-01

    Modern surface sensitive electron spectroscopies and other surface analytical techniques have in recent years been extensively applied to the study of H 2 and CO adorption on transition metals. This work has now been extended to include the heterogeneous reaction between adsorbed H 2 and CO on these metals. The combination of surface analysis (carried out under ultra-high vacuum conditions) and reaction rate measurements in the range of 100 mbar to 1 bar total pressure is being practiced. This approach yields information on changes of the surface composition of the catalyst as well as data on reaction kinetics and the possible time dependence of the reaction rate. Low surface area samples — either single or polycrystalline - are used for these studies. In the present paper the results obtained by this approach will be reviewed and discussed in the light of the adsorption data. Recent advances in the direction of studying either poisoned or promoted catalytic surfaces will also be mentioned.

  7. Surface transition on ice induced by the formation of a grain boundary.

    Directory of Open Access Journals (Sweden)

    Christian Pedersen

    Full Text Available Interfaces between individual ice crystals, usually referred to as grain boundaries, play an important part in many processes in nature. Grain boundary properties are, for example, governing the sintering processes in snow and ice which transform a snowpack into a glacier. In the case of snow sintering, it has been assumed that there are no variations in surface roughness and surface melting, when considering the ice-air interface of an individual crystal. In contrast to that assumption, the present work suggests that there is an increased probability of molecular surface disorder in the vicinity of a grain boundary. The conclusion is based on the first detailed visualization of the formation of an ice grain boundary. The visualization is enabled by studying ice crystals growing into contact, at temperatures between -20°C and -15°C and pressures of 1-2 Torr, using Environmental Scanning Electron Microscopy. It is observed that the formation of a grain boundary induces a surface transition on the facets in contact. The transition does not propagate across facet edges. The surface transition is interpreted as the spreading of crystal dislocations away from the grain boundary. The observation constitutes a qualitatively new finding, and can potentially increase the understanding of specific processes in nature where ice grain boundaries are involved.

  8. Transition state theory for solvated reactions beyond recrossing-free dividing surfaces.

    Science.gov (United States)

    Revuelta, F; Bartsch, Thomas; Garcia-Muller, P L; Hernandez, Rigoberto; Benito, R M; Borondo, F

    2016-06-01

    The accuracy of rate constants calculated using transition state theory depends crucially on the correct identification of a recrossing-free dividing surface. We show here that it is possible to define such optimal dividing surface in systems with non-Markovian friction. However, a more direct approach to rate calculation is based on invariant manifolds and avoids the use of a dividing surface altogether, Using that method we obtain an explicit expression for the rate of crossing an anharmonic potential barrier. The excellent performance of our method is illustrated with an application to a realistic model for LiNC⇌LiCN isomerization.

  9. The formation energy for steps and kinks on cubic transition metal surfaces

    DEFF Research Database (Denmark)

    Vitos, Levente; Skriver, Hans Lomholt; Kollàr, Janos

    1999-01-01

    We have used our first-principles database of surface energies for metals in conjunction with the concept of vicinal surfaces to derive the energies of formation of monoatomic steps and corresponding kinks on close-packed surface facets of bcc and fee transition metals. The entries in the database...... allow for a direct calculation of the energies of a number of important steps. For the remaining steps and for all the kinks the energies of formation have been estimated from pair potential expansions of the entries in the database. (C) 1999 Elsevier Science B.V. All rights reserved....

  10. Chiral universality class of normal-superconducting and exciton condensation transitions on surface of topological insulator

    Science.gov (United States)

    Li, Dingping; Rosenstein, Baruch; Shapiro, B. Ya.; Shapiro, I.

    2015-06-01

    New two-dimensional systems such as the surfaces of topological insulators (TIs) and graphene offer the possibility of experimentally investigating situations considered exotic just a decade ago. These situations include the quantum phase transition of the chiral type in electronic systems with a relativistic spectrum. Phonon-mediated (conventional) pairing in the Dirac semimetal appearing on the surface of a TI causes a transition into a chiral superconducting state, and exciton condensation in these gapless systems has long been envisioned in the physics of narrow-band semiconductors. Starting from the microscopic Dirac Hamiltonian with local attraction or repulsion, the Bardeen-Cooper-Schrieffer type of Gaussian approximation is developed in the framework of functional integrals. It is shown that owing to an ultrarelativistic dispersion relation, there is a quantum critical point governing the zero-temperature transition to a superconducting state or the exciton condensed state. Quantum transitions having critical exponents differ greatly from conventional ones and belong to the chiral universality class. We discuss the application of these results to recent experiments in which surface superconductivity was found in TIs and estimate the feasibility of phonon pairing.

  11. 3 CFR - Pay Freeze

    Science.gov (United States)

    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... the White House staff forgo pay increases until further notice. Accordingly, as a signal of our shared...

  12. The Freezing Bomb

    Science.gov (United States)

    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…

  13. Freeze drying method

    Science.gov (United States)

    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.

  14. Freeze drying apparatus

    Science.gov (United States)

    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.

  15. Surface engineering of transition metal dichalcogenides for two-dimensional electronic device applications

    Science.gov (United States)

    Azcatl Zacatzi, Angelica

    Two-dimensional transition metal dichalcogenides (TMDs) are considered potential channel materials for emerging electronic devices in the roadmap beyond Si-CMOS technology. Layered TMDs offer intrinsically an ultrathin body without compromising the semiconducting properties. For the implementation of TMDs in electronic device structures, the understanding of their surface properties is essential. This work combines a variety of materials characterization techniques such as in-situ X-ray photoelectron spectroscopy, atomic force microscopy, transmission electron microscopy, and Raman spectroscopy to investigate the chemistry and structure of TMDs upon different surface treatments. In addition, first-principle calculations are presented to give insights on the mechanism involved in the surface modification of TMD. The impact of the TMDs surface modification on processes for gate-oxide integration by atomic layer deposition and covalent doping are investigated here. This work provides a comprehensive understanding of the surface chemistry of TMDs for two-dimensional electronic device applications.

  16. Ranking the Stability of Transition-Metal Complexes by On-Surface Atom Exchange.

    Science.gov (United States)

    Rieger, Alexandra; Schnidrig, Stephan; Probst, Benjamin; Ernst, Karl-Heinz; Wäckerlin, Christian

    2017-12-21

    Surface-adsorbed macrocycles exhibit a number of interesting physical and chemical properties; many of them are determined by their transition-metal centers. The hierarchical exchange of the central metal atom in such surface-adsorbed complexes is demonstrated, specifically in the porphyrin-like macrocycle pyrphyrin adsorbed on Cu(111). Using scanning tunneling microscopy and X-ray photoelectron spectroscopy, we show that Cu as central metal atom is easily exchanged with Ni or Fe atoms supplied in trace amounts to the surface. Atom exchange of Ni centers with Fe atoms also occurs, with moderate yield. These results allow ranking the stability of the surface-adsorbed Cu, Ni, and Fe complexes. The fact that the atom exchange occurs at 423 K shows that surface-adsorbed macrocycles can be surprisingly easily transformed.

  17. CO adsorption on metal-oxide surfaces doped with transition-metal adatoms

    Energy Technology Data Exchange (ETDEWEB)

    Blomqvist, Janne; Lehman, Lauri; Salo, Petri [Department of Applied Physics, Aalto University, FI-00076 Aalto (Finland)

    2012-05-15

    Using first principles density functional theory calculations, we have studied the adsorption of carbon monoxide (CO) on clean, Ag and Pd doped MgO(001), TiO{sub 2}(110), and {alpha}-Al{sub 2}O{sub 3}(0001) surfaces. Our results show that adsorption of CO on the clean surfaces is generally weak. Ag doping improves the adsorption only weakly, except on the TiO{sub 2} surface. The presence of Pd, however, significantly improves adsorption on all the surfaces studied. On the doped surfaces, the best adsorption sites are always the sites on top of the transition metal adatom, and the interaction range is 3-4 Aa around an isolated adatom. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Bjorken model with Freeze Out

    OpenAIRE

    Magas, V. K.; Csernai, L. P.

    2007-01-01

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

  19. Exploring the Nature of Contact Freezing

    Science.gov (United States)

    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.

  20. The additional phase transition of DPPC monolayers at high surface pressure confirmed by GIXD study

    DEFF Research Database (Denmark)

    Shen, Chen; Serna, Jorge B. de la; Struth, Bernd

    -expanded/liquid-condensed (LE/LC) phase transition at ~10mN/m is well known. Here we present results from Langmuir isotherm measurements that evidence a so far not documented second phase transition at elevated surface pressure Π (~50mN/m). The varying lateral structures of the monolayer at 8mN/m, 20mN/m, 30mN/m, 40mN/m, 50m......N/m, 60mN/m, 70mN/m were investigated by grazing incidence X-ray diffraction (GIXD). The results report on the 2D packing lattice with the inter-chain distance dxy. Moreover, the tilt angle of the palmitoyl chains was calculated combining the lattice parameters and the geometrical boundary conditions....... The course of the inter-chain distance versus surface pressure exhibits three regimes, separated by the LE/LC transition and the second phase transition at the higher pressure. This feature may assign a functional task to DPPC in the lung surfactant since it contributes to the mechanical stability...

  1. Noise-and delay-induced phase transitions of the dimer-monomer surface reaction model

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Chunhua, E-mail: zchh2009@126.com [Faculty of Science, Kunming University of Science and Technology, Kunming 650093 (China) and Center of Metallurgical Energy Conservation and Emission Reduction, Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China); Wang Hua, E-mail: wanghuaheat@hotmail.com [Center of Metallurgical Energy Conservation and Emission Reduction, Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China)

    2012-06-19

    Highlights: Black-Right-Pointing-Pointer We study the dimer-monomer surface reaction model. Black-Right-Pointing-Pointer We show that noise induces first-order irreversible phase transition (IPT). Black-Right-Pointing-Pointer Combination of noise and time-delayed feedback induce first- and second-order IPT. Black-Right-Pointing-Pointer First- and second-order IPT is viewed as noise-and delay-induced phase transitions. - Abstract: The effects of noise and time-delayed feedback in the dimer-monomer (DM) surface reaction model are investigated. Applying small delay approximation, we construct a stochastic delayed differential equation and its Fokker-Planck equation to describe the state evolution of the DM reaction model. We show that the noise can only induce first-order irreversible phase transition (IPT) characteristic of the DM model, however the combination of the noise and time-delayed feedback can simultaneously induce first- and second-order IPT characteristics of the DM model. Therefore, it is shown that the well-known first- and second-order IPT characteristics of the DM model may be viewed as noise-and delay-induced phase transitions.

  2. Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces

    Science.gov (United States)

    Murphy, Colin J.; Carrasco, Javier; Lawton, Timothy J.; Liriano, Melissa L.; Baber, Ashleigh E.; Lewis, Emily A.; Michaelides, Angelos; Sykes, E. Charles H.

    2014-07-01

    Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

  3. Irving Langmuir Prize Lecture - A predictive theory of transition metal surface catalysis

    Science.gov (United States)

    Norskov, Jens

    2015-03-01

    The lecture will outline a theory of heterogeneous catalysis that allows a detailed understanding of elementary chemical processes at transition metal surfaces and singles out the most important parameters determining catalytic activity and selectivity. It will be shown how scaling relations allow the identification of descriptors of catalytic activity and how they can be used to construct activity and selectivity maps. The maps can be used to define catalyst design rules and examples of their use will be given.

  4. Safer Ski Jumps: Design of Landing Surfaces and Clothoidal In-Run Transitions

    Science.gov (United States)

    2010-06-01

    www.skiingthebackcountry.com/Early_Skiing_History.php [Accessed: February 25, 2010]. [4] M. Lund, ―A Short History of Alpine Skiing ,‖ Skiing ...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited SAFER SKI JUMPS...DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE: Safer Ski Jumps: Design of Landing Surfaces and Clothoidal In-Run Transitions 5. FUNDING

  5. Tuning the metal-insulator transition in manganite films through surface exchange coupling with magnetic nanodots.

    Science.gov (United States)

    Ward, T Z; Gai, Z; Xu, X Y; Guo, H W; Yin, L F; Shen, J

    2011-04-15

    In strongly correlated electronic systems, the global transport behavior depends sensitively on spin ordering. We show that spin ordering in manganites can be controlled by depositing isolated ferromagnetic nanodots at the surface. The exchange field at the interface is tunable with nanodot density and makes it possible to overcome dimensionality and strain effects in frustrated systems to greatly increasing the metal-insulator transition and magnetoresistance. These findings indicate that electronic phase separation can be controlled by the presence of magnetic nanodots.

  6. BEP-relations for N2 dissociation over stepped transition metal and alloy surfaces

    DEFF Research Database (Denmark)

    Fronczek-Munter, Ture Rønved; Bligaard, Thomas; Christensen, Claus H.

    2008-01-01

    , a perfectly linear Bronsted-Evans-Polanyi (BEP) relation between the transition-state potential energy and the dissociative chemisorption energy is obtained. The perfect BEP relation, which extends over 12 eV in chemisorption energy, suggests that the manifestation of BEP relations for surface reactions...... is a general electronic structure effect, and that geometric effects are responsible for the scatter which is normally observed around the BEP line. The BEP relation is also shown to be valid for both surface and bulk alloys. The scatter is, however, larger than for the pure elements. This can be understood...

  7. Unraveling wetting transition through surface textures with X-rays: liquid meniscus penetration phenomena.

    Science.gov (United States)

    Antonini, C; Lee, J B; Maitra, T; Irvine, S; Derome, D; Tiwari, Manish K; Carmeliet, J; Poulikakos, D

    2014-02-11

    In this report we show that synchrotron X-ray radiography is a powerful method to study liquid-air interface penetration through opaque microtextured surface roughness, leading to wetting transition. We investigate this wetting phenomenon in the context of sessile drop evaporation, and establish that liquid interface sinking into the surface texture is indeed dictated by the balance of capillary and Laplace pressures, where the intrinsically three-dimensional nature of the meniscus must be accounted for. Air bubble entrapment in the texture underneath impacting water drops is also visualized and the mechanisms of post-impact drop evaporation are discussed.

  8. Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

    2017-08-01

    The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

  9. Activation of CO2 on transition metal surfaces and oxide supported metal thin films

    Science.gov (United States)

    Paul, Sujata; Buongiorno Nardelli, Marco

    2009-03-01

    Using first principles simulations based on Density Functional Theory, we have investigated the adsorption and activation properties of CO2 on a variety of transition metal surfaces and oxide supported metal thin films. We intend to focus on the chemical conversion of CO2 through heterogeneous catalysis using surfaces and interfaces where there is nanoscale control over charge density at the reactive sites. The activation of CO2 on clean metal surfaces is possible at very high temperatures and the situations changes drastically when reaction happens on oxide supported metal thin film. The chemical reactivity of the molecule on the surface depends on the charge rearrangement at the metal-alkaline earth oxide interface. We want to understand the possible catalytic systems and characterize the relevant geometrical and electronic parameters related to the reaction mechanisms, rates and yield.

  10. DFT studies on the adsorption of thiols at transition metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Seema, Porntip; Behler, Joerg; Marx, Dominik [Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum (Germany)

    2011-07-01

    The interaction of sulfur-containing molecules with transition metal surfaces plays an important role for example in the poisoning of heterogeneous catalysts and the formation of self-assembled monolayers. A large number of theoretical and experimental studies has been carried out in recent years, but still several questions on the structures of these systems remain open. We present density-functional theory (DFT) calculations for the adsorption of several sulfur-containing species (e.g. S atoms, H{sub 2}S, CH{sub 3}SH) on Cu(111) and Ag(111) surfaces. Calculations have been carried out for a variety of adsorbate coverages, binding sites and surface models (slabs and clusters). We find that the order of the binding energies is S>SH>SCH{sub 3}, with an increased binding energy at surface defects. In general, the sulfur-metal interaction is stronger for Cu(111) than for Ag(111).

  11. DFT studies on the interaction of sulfur with transition metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Seema, Porntip; Behler, Joerg; Marx, Dominik [Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2010-07-01

    The interaction of sulfur atoms with transition metal surfaces plays an important role for example in the poisoning of heterogeneous catalysts and the formation of self-assembled monolayers of thiolates. In the present work, the sulfur adsorption on Cu(111), Ag(111) and Au(111) surfaces has been studied within the framework of density-functional theory (DFT). Calculations have been carried out for a variety of adsorbate phases, and the sulfur binding sites and binding energies have been investigated systematically as a function of coverage at ideal surfaces as well as at defects. We find that the order of the adsorption energies of the sulfur atoms on the different defect-free metal slabs is Cu(111)>Ag(111)>Au(111). This result is independent of the coverage of the surface.

  12. Cake shrinkage during freeze drying: a combined experimental and theoretical study.

    Science.gov (United States)

    Rambhatla, S; Obert, J P; Luthra, S; Bhugra, C; Pikal, Michael J

    2005-01-01

    The aim of this study is to investigate, by experimental studies and theoretical analysis, the phenomenon of cake shrinkage during the lyophilization process and to investigate the effect of shelf temperature during primary drying and secondary drying on the degree of cake shrinkage. Freeze-drying experiments were performed using 5% w/v sucrose where the drying protocols were altered in order to produce differing product temperature profiles. Resistance data during freeze drying were evaluated by the Manometric Temperature Measurement (MTM) method. Theoretical simulation of the freeze-drying process was performed using the Passage Freeze-Drying software. The difference between the glass transition temperature and the product temperature (Tg-T) obtained from the theoretical analysis was calculated and used for correlation with experimental shrinkage data. The Brunauer, Emmeth, Teller (BET) Specific Surface Area (SSA) Analysis was used as a method to quantify the degree of shrinkage. Samples were also analyzed for pore volume by mercury porosimetry. The SSA analysis on the freeze-dried samples showed an increase in SSA when samples were freeze dried at a lower shelf temperature during primary drying and at a slower ramp rate during secondary drying. The trend in surface area values was consistent with that obtained for pore size values. However, differences obtained among the various samples are small and cake diameter measurements showed that there was approximately 17% shrinkage even in the sample freeze dried at temperatures well below the Tg' and Tg. Variations in process and product temperature only accounted for an additional 2%-3% shrinkage. Resistance data obtained at various primary drying shelf temperatures showed a good correlation with surface area. The Tg-T behavior of the freeze-dried samples showed that a slow ramp rate of 0.1 degrees C/min during secondary drying maintains a product well below the Tg at all times and a higher ramp rate gives negative

  13. Freezing small pelagic fish

    National Research Council Canada - National Science Library

    McDonald, I

    1978-01-01

    This note gives advice on the handling and freezing of small pelagic fish, notably herring and mackerel, in quantity soon after capture, either on the fishing vessel or at the port processing plant...

  14. Surface element segregation and electrical conductivity of lithium layered transition-metal oxide cathode materials

    Science.gov (United States)

    Li, Guohua; Li, Qi; Li, Liping; Fan, Jianming; Ge, Qingqin; Xie, Dongjiu; Zheng, Jing; Li, Guangshe

    2018-01-01

    Surface element segregation and electric conductivity are critical in determining lithium storage ability of given cathode materials, which are poorly understood and not correlated with the structure and overall performance. Here, layered lithium transition-metal oxides, one of the state-of-the-art cathode materials for lithium ion batteries are chosen to study. A serial of LiNixCo1-2xMnxO2 samples were prepared via a solid state reaction and subsequently characterized by XRD in conjunction with structural refinement, XPS depth profiling, and AC impedance spectroscopy. Slightly different expansion rates are observed for lattice parameters (a and c/3) with varying of Ni content, which is attributed to the increase of average metal-ion radius and an increase of eg electron that enhances the columbic repulsion between transition metal and oxygen atoms. XPS depth profiling results show that surface composition is significantly deviated from bulk, in which Ni and Mn atoms tend to enrich in the surface region, while Co element is relatively deficient. Further, surface element segregation is alleviated by the increase of Ni/Mn content. Moreover, increasing the Ni/Mn content also raises the activation energy of bulk conduction.

  15. Modification of the surface electronic and chemical properties of Pt(111) by subsurface 3d transition metals

    DEFF Research Database (Denmark)

    Kitchin, J. R.; Nørskov, Jens Kehlet; Barteau, M. A.

    2004-01-01

    The modification of the electronic and chemical properties of Pt(111) surfaces by subsurface 3d transition metals was studied using density-functional theory. In each case investigated, the Pt surface d-band was broadened and lowered in energy by interactions with the subsurface 3d metals......, resulting in weaker dissociative adsorption energies of hydrogen and oxygen on these surfaces. The magnitude of the decrease in adsorption energy was largest for the early 3d transition metals and smallest for the late 3d transition metals. In some cases, dissociative adsorption was calculated...

  16. Atomic Structure of a Spinel-like Transition Al2O3 (100) Surface

    DEFF Research Database (Denmark)

    Jensen, Thomas Nørregaard; Meinander, Kristoffer; Helveg, Stig

    2014-01-01

    We study a crystalline epitaxial alumina thin film with the characteristics of a spinel-type transition Al2O3(100) surface by using atom-resolved noncontact atomic force microscopy and density functional theory. It is shown that the films are terminated by an Al-O layer rich in Al vacancies......, exhibiting a strong preference for surface hydroxyl group formation in two configurations. The transition alumina films are crystalline and perfectly stable in ambient atmospheres, a quality which is expected to open the door to new fundamental studies of the surfaces of transition aluminas....

  17. Adsorption and dissociation of dinitrogen on transition metal (Ta, W and Re) doped MgO surface

    KAUST Repository

    Yadav, Manoj Kumar

    2016-06-16

    The adsorption and dissociation of dinitrogen on transition metal (Ta, W and Re) doped MgO(100) surface has been studied employing density functional theory. It is found that all these transition metals (TM) on MgO(100) surface are capable of adsorbing dinitrogen (N2), however there is no dissociative adsorption of N2 on single transition metal dopant. When two TM atoms are doped on MgO(100) surface, dissociative adsorption of dinitrogen occurs in all the three cases. Whether the dissociation is spontaneous or is it associated with activation barrier depends on the orientation of N2 molecule approaching the dopant site.

  18. Fermi surface reconstruction and multiple quantum phase transitions in the antiferromagnet CeRhIn5

    Science.gov (United States)

    Jiao, Lin; Chen, Ye; Kohama, Yoshimitsu; Graf, David; Bauer, E. D.; Singleton, John; Zhu, Jian-Xin; Weng, Zongfa; Pang, Guiming; Shang, Tian; Zhang, Jinglei; Lee, Han-Oh; Park, Tuson; Jaime, Marcelo; Thompson, J. D.; Steglich, Frank; Si, Qimiao; Yuan, H. Q.

    2015-01-01

    Conventional, thermally driven continuous phase transitions are described by universal critical behavior that is independent of the specific microscopic details of a material. However, many current studies focus on materials that exhibit quantum-driven continuous phase transitions (quantum critical points, or QCPs) at absolute zero temperature. The classification of such QCPs and the question of whether they show universal behavior remain open issues. Here we report measurements of heat capacity and de Haas–van Alphen (dHvA) oscillations at low temperatures across a field-induced antiferromagnetic QCP (Bc0 ≈ 50 T) in the heavy-fermion metal CeRhIn5. A sharp, magnetic-field-induced change in Fermi surface is detected both in the dHvA effect and Hall resistivity at B0* ≈ 30 T, well inside the antiferromagnetic phase. Comparisons with band-structure calculations and properties of isostructural CeCoIn5 suggest that the Fermi-surface change at B0* is associated with a localized-to-itinerant transition of the Ce-4f electrons in CeRhIn5. Taken in conjunction with pressure experiments, our results demonstrate that at least two distinct classes of QCP are observable in CeRhIn5, a significant step toward the derivation of a universal phase diagram for QCPs. PMID:25561536

  19. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong

    2014-02-07

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  20. Surfactant-modified diffusion on transition-metal surfaces (reprinted with the addition of the appendices)

    Energy Technology Data Exchange (ETDEWEB)

    FEIBELMAN,PETER J.; KELLOGG,GARY LEE

    2000-03-01

    Wanting to convert surface impurities from a nuisance to a systematically applicable nano-fabrication tool, the authors have sought to understand how such impurities affect self-diffusion on transition-metal surfaces. Their field-ion microscope experiments reveal that in the presence of surface hydrogen, self-diffusion on Rh(100) is promoted, while on Pt(100), not only is it inhibited, but its mechanism changes. First-principles calculations aimed at learning how oxygen fosters perfect layerwise growth on a growing Pt(111) crystal contradict the idea in the literature that it does so by directly promoting transport over Pt island boundaries. The discovery that its real effect is to burn off adventitious adsorbed carbon monoxide demonstrates the predictive value of state-of-the-art calculation methods.

  1. Surface Properties of Titanium dioxide and its Structural Modifications by Reactions with Transition Metals

    Science.gov (United States)

    Halpegamage, Sandamali

    Surfaces of metal oxides play a vital role in many technologically important applications. The surfaces of titanium dioxide, in particular, show quite promising properties that can be utilized in solid-state gas sensing and photocatalysis applications. In the first part of this dissertation we investigate these properties of TiO2 surfaces through a vigorous surface scientific approach. In the second part, we investigate the possibilities of modifying the TiO2 surfaces by depositing multi-component transition metal oxide monolayers so that the properties of bare TiO2 surface can be influenced in a beneficial way. For instance, via formation of new surface sites or cations that have different valance states, the chemisorption and catalytic properties can be modified. We use sophisticated experimental surface science techniques that are compatible with ultra-high vacuum technology for surface characterization. All the experimental results, except for the photocatalysis experiments, were compared to and verified by supporting DFT-based theoretical results produced by our theory collaborators. TiO2 based solid-state gas sensors have been used before for detecting trace amounts of explosives such as 2,4-dinitrololuene (DNT), a toxic decomposition product of the explosive 2,4,6-trinitrotoluene (TNT) that have very low vapor pressure. However, the adsorption, desorption and reaction mechanism were not well- understood. Here, we investigate 2,4-DNT adsorption on rutile-TiO2(110) surface in order to gain insight about these mechanisms in an atomistic level and we propose an efficient way of desorbing DNT from the surface through UV-light induced photoreactions. TiO2 exists in different polymorphs and the photocatalytic activity differs from one polymorph to another. Rutile and anatase are the most famous forms of TiO2 in photocatalysis and anatase is known to show higher activity than rutile. The photoactivity also varies depending on the surface orientation for the same

  2. Freezing precipitation in Russia and the Ukraine

    Directory of Open Access Journals (Sweden)

    A. A. Zavyalova

    2007-04-01

    Full Text Available Conditions for freezing precipitation (FP, including freezing rain (FR and freezing drizzle (FZ for 8 airports in Russia and 4 in the Ukraine are studied on the basis of 10 to 20-year series of surface observations, radiosonde and objective analysis data. Statistical characteristics are presented of the FP episode durations and of occurrence frequency dependences on surface air temperature, wind direction and speed and cloud base height. From the radiosonde data, it is found that the "classical mechanism" of FP generation (for which, stratification of "warm nose" type in the cloud layer is necessary is not frequent: most of FP cases are associated with "all cold" conditions in the lower 3-km layer, that is, with negative temperatures in and below the clouds.

  3. The additional phase transition of DPPC monolayers at high surface pressure confirmed by GIXD study

    DEFF Research Database (Denmark)

    Shen, Chen; Serna, Jorge B. de la; Struth, Bernd

    Pulmonary surfactant forms the alveolar monolayer at the air/aqueous interface within the lung. During the breathing process, the surface pressure periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. The monolayer consists...... of ~90% of lipid with 10% integrated proteins. Among its lipid compounds, di- palmitoyl-phosphatidylcholine (DPPC) dominates (~45wt%). No other lipid but DPPC was so far reported to be compressible to very high surface pressure (~70mN/m) before its monolayer collapsed. Its liquid......-expanded/liquid-condensed (LE/LC) phase transition at ~10mN/m is well known. Here we present results from Langmuir isotherm measurements that evidence a so far not documented second phase transition at elevated surface pressure Π (~50mN/m). The varying lateral structures of the monolayer at 8mN/m, 20mN/m, 30mN/m, 40mN/m, 50m...

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

    Science.gov (United States)

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

    2014-11-01

    Freeze-tolerant organisms survive internal ice formation; however, the adaptations to repeated freeze-thaw cycles are often not well investigated. Here we report how three geographically different populations of Enchytraeus albidus (Germany, Iceland and Svalbard) respond to three temperature treatments - constant thawed (0°C), constant freezing (-5°C) and fluctuating temperature (0 to -5°C) - over a period of 42 days. Survival varied between treatments and populations such that enchytraeids from arctic locations had a higher survival following prolonged freeze periods compared with temperate populations. However, enchytraeids from temperate locations had the same survival rate as arctic populations when exposed to repeated freeze-thaw events. Across all populations, metabolic rate decreased markedly in frozen animals (-5°C) compared with thawed controls (0°C). This decrease is likely due to the lower temperature of frozen animals, but also to the transition to the frozen state per se. Animals exposed to repeated freeze-thaw events had an intermediate metabolic rate and freeze-thaw events were not associated with pronounced excess energetic costs. Overwintering under either condition was not associated with a decrease in lipid content; however, during exposure to constant freezing and repeated freeze-thaw events there was a noticeable decrease in carbohydrate stores over time. Thus, animals exposed to constant freezing showed a decrease in glycogen stores, while both glucose and glycogen content decreased over time when the organisms were exposed to repeated freezing. The results therefore suggest that carbohydrate resources are important as a fuel for E. albidus during freezing whereas lipid resources are of marginal importance. © 2014. Published by The Company of Biologists Ltd.

  5. Identification of Soil Freezing and Thawing States Using SAR Polarimetry at C-Band

    Directory of Open Access Journals (Sweden)

    Thomas Jagdhuber

    2014-03-01

    Full Text Available The monitoring of soil freezing and thawing states over large areas is very challenging on ground. In order to investigate the potential and the limitations of space-borne SAR polarimetry at C-band for soil state survey, analyses were conducted on an entire winter time series of fully polarimetric RADARSAT-2 data from 2011/2012 to identify freezing as well as thawing states within the soil. The polarimetric data were acquired over the Sodankylä test site in Finland together with in situ measurements of the soil and the snow cover. The analyses indicate clearly that the dynamics of the polarimetric entropy and mean scattering alpha angle are directly correlated to soil freezing and thawing states, even under distinct dry snow cover. First modeling attempts using the Extended Bragg soil scattering model justify the observed trends, which indicate surface-like scattering during frozen soil conditions and multiple/volume scattering for thawed soils. Hence, these first investigations at C-band foster motivation to work towards a robust polarimetric detection of soil freezing and thawing states as well as their transition phase.

  6. Theory and numerical application of subsurface flow and transport for transient freezing conditions

    Energy Technology Data Exchange (ETDEWEB)

    White, M.D. [Pacific Northwest Lab., Richland, WA (United States). Earth and Environmental Sciences Center

    1995-04-01

    Protective barriers are being investigated for the containment of radioactive waste within subsurface environments. Predicting the effectiveness of cryogenic barriers and near-surface barriers in temperate or arctic climates requires capabilities for numerically modeling subsurface flow and transport for freezing soil conditions. A predictive numerical model is developed herein to simulate the flow and transport of radioactive solutes for three-phase (water-ice-air) systems under freezing conditions. This physically based model simulates the simultaneous flow of water, air, heat, and radioactive solutes through variably saturated and variably frozen geologic media. Expressions for ice (frozen water) and liquid water saturations as functions of temperature, interfacial pressure differences, and osmotic potential are developed from nonhysteretic versions of the Brooks and Corey and van Genuchten functions for soil moisture retention. Aqueous relative permeability functions for variably saturated and variably frozen geologic media are developed from the Mualem and Burdine theories for predicting relative permeability of unsaturated soil. Soil deformations, caused by freezing and melting transitions, are neglected. Algorithms developed for predicting ice and liquid water saturations and aqueous-phase permeabilities were incorporated into the finite-difference based numerical simulator STOMP (Subsurface Transport Over Multiple Phases). Application of the theory is demonstrated by the solution of heat and mass transport in a horizontal cylinder of partially saturated porous media with differentially cooled ends, with the colder end held below the liquid water freezing point. This problem represents an essential capability for modeling cryogenic barriers in variably saturated geologic media.

  7. Chiral universality class of the normal-superconducting and the exciton condensation transition on the surface of topological insulator

    OpenAIRE

    Li, Dingping; Rosenstein, Baruch; Shapiro, B. Ya.; Shapiro, I.

    2015-01-01

    New two dimensional systems like surface of topological insulator and graphene offer a possibility to experimentally investigate situations considered "exotic" just a decade ago. One of those is the quantum phase transition of the "chiral" type in electronic systems with relativistic spectrum. Phonon mediated ("conventional") pairing in the Dirac semimetal appearing on the surface of topological insulator leads to transition into a chiral superconducting state, while exciton condensation in t...

  8. Peculiarities of phase transitions in the iron-nanoclay surface system studied by Mössbauer spectroscopy

    Science.gov (United States)

    Zalutskii, A. A.

    2014-10-01

    Results of an experimental investigation of the peculiarities of phase transitions in iron compounds localized in natural low-dimensional systems (nanoclays) are reported. Conditions for observation of the phase transition by Mössbauer spectroscopy in thin films of ice adsorbed on the surface of typical clays are established for the first time. Data obtained by the proposed method for the geography of iron exchange complexes on aluminosilicate clay surface are presented.

  9. Surface-dependent conductivity, transition type, and energy band structure in amorphous indium tin oxide films

    Science.gov (United States)

    Wang, Yaqin; Tang, Wu

    2017-12-01

    Amorphous indium tin oxide (ITO) thin films were deposited on polymethylmethacrylate and polyethyleneterephthalate substrates by radio frequency magnetron sputtering at room temperature. An interesting substrate morphology effect of ITO films on the conductivity, optical transition type and energy band structure was observed. A simplified film system model with a square potential for surface morphology was employed to explain the difference of conductivity. The energy band structures were also calculated based on the theory of amorphous semiconductor. The conclusion demonstrated the width of optical band gap, as well as the relative position of the Fermi level and mobility edge, which can easily be extended to the band structure determination of other transparent conductive films.

  10. Active directional switching of surface plasmon polaritons using a phase transition material.

    Science.gov (United States)

    Kim, Sun-Je; Yun, Hansik; Park, Kyungsoo; Hong, Jongwoo; Yun, Jeong-Geun; Lee, Kyookeun; Kim, Joonsoo; Jeong, Sun Jae; Mun, Sang-Eun; Sung, Jangwoon; Lee, Yong Wook; Lee, Byoungho

    2017-03-06

    Active switching of near-field directivity, which is an essential functionality for compact integrated photonics and small optoelectronic elements, has been challenging due to small modulation depth and complicated fabrication methods for devices including active optical materials. Here, we theoretically and experimentally realize a nanoscale active directional switching of surface plasmon polaritons (SPPs) using a phase transition material for the first time. The SPP switching device with noticeable distinction is demonstrated based on the phase transition of vanadium dioxide (VO2) at the telecom wavelength. As the insulator-to-metal phase transition (IMT) of VO2 induces the large change of VO2 permittivity at telecom wavelengths, the plasmonic response of a nanoantenna made of VO2 can be largely tuned by external thermal stimuli. The VO2-insulator-metal (VIM) nanoantenna and its periodic array, the VIM metagrating, are suggested as optical switches. The directional power distinction ratio is designed to change from 8.13:1 to 1:10.56 by the IMT and it is experimentally verified that the ratio changes from 3.725:1 to 1:3.132 as the VIM metagratings are heated up to 90 °C. With an electro-thermally controllable configuration and an optimized resonant design, we expect potential applications of the active switching mechanism for integrable active plasmonic elements and reconfigurable imaging.

  11. Schlieren imaging of nano-scale atom-surface inelastic transition using a Fresnel biprism atom interferometer

    Science.gov (United States)

    Grucker, J.; Baudon, J.; Perales, F.; Dutier, G.; Bocvarski, V.; Karam, J.-C.; Vassilev, G.; Ducloy, M.

    2008-05-01

    Surface-induced exo-energetic inelastic transitions among atomic Zeeman states in a magnetic field (“van der Waals Zeeman” transitions) are useable as tuneable beam splitters. A transversally coherent atom beam impinging a pair of opposite surfaces (e.g. 2 edges of a slit or of an ensemble of periodic slits) gives rise to two coherently diffracted wave packets. Within the wave packet overlap, non-localised interference fringes of the Young-slit type are predicted. From the diffraction pattern observed in the Fraunhofer regime (Schlieren image), detailed information about the transition amplitude on a scale of a few nanometers should be derived.

  12. Porosity and water activity effects on stability of crystalline β-carotene in freeze-dried solids.

    Science.gov (United States)

    Harnkarnsujarit, Nathdanai; Charoenrein, Sanguansri; Roos, Yrjö H

    2012-11-01

    Stability of entrapped crystalline β-carotene as affected by water activity, solids microstructure, and composition of freeze-dried systems was investigated. Aliquots (1000 mm(3) , 20% w/w solids) of solutions of maltodextrins of various dextrose equivalents (M040:DE6, M100:DE11, and M250:DE25.5), M100-sugars (1:1 glucose, fructose and sucrose), and agar for gelation with dispersed β-carotene were frozen at -20, -40, or -80 °C and freeze-dried. Glass transition and α-relaxation temperatures were determined with differential scanning calorimetry and dynamic mechanical analysis, respectively. β-Carotene contents were monitored spectrophotometrically. In the glassy solids, pore microstructure had a major effect on β-carotene stability. Small pores with thin walls and large surface area allowed β-carotene exposure to oxygen which led to a higher loss, whereas structural collapse enhanced stability of β-carotene by decreasing exposure to oxygen. As water plasticized matrices, an increase in molecular mobility in the matrix enhanced β-carotene degradation. Stability of dispersed β-carotene was highest at around 0.2 a(w) , but decreasing structural relaxation times above the glass transition correlated well with the rate of β-carotene degradation at higher a(w) . Microstructure, a(w) , and component mobility are important factors in the control of stability of β-carotene in freeze-dried solids. β-Carotene expresses various nutritional benefits; however, it is sensitive to oxygen and the degradation contributes to loss of nutritional values as well as product color. To increase stability of β-carotene in freeze-dried foods, the amount of oxygen penetration need to be limited. The modification of freeze-dried food structures, for example, porosity and structural collapse, components, and humidity effectively enhance the stability of dispersed β-carotene in freeze-dried solids. © 2012 Institute of Food Technologists®

  13. Atomic structure of the adsorption of transition metals on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Cocoletzi, G.H. [IF-BUAP, 72000 Puebla (Mexico); Takeuchi, N. [CCMC-UNAM, Ensenada, BCN (Mexico)

    2007-07-01

    Full text: Solid state devices are useful for their high sensitivity in a small volume. Applications of such devices as dose materials include semi-conducting dose-rate, and dose-reading measuring devices. Transition metals (TM) have electronic and atomic properties similar to those of rare earth elements when they are adsorbed on silicon surfaces. The interfaces of transition metals silicides with Si (111) have very small lattice mismatches, sharp interfaces, and low Schottky barrier, making them ideal in electronic devices, such as infrared detectors and rectifying contacts. In this work we shall describe our first principles total energy calculations to investigate structural properties of bulk ScSi and YSi, the two dimensional arrangement of ScSi{sub 2} and YSi{sub 2} on the Si(111) surface, and the growth of a few layers of ScSi{sub 1.7} and YSi{sub 1.7} on the Si(111) surface. Our calculated bulk structural parameters are in excellent agreement with experimental values. It will be shown that one monolayer of a TM on Si( l l 1) yields a two dimensional phase with (lxl) periodicity consisting of a layer of TM atoms on T4 sites and a Si bilayer on top. This double layer of Si atoms is very close to ideal Si(111)-(1x1) surface, but rotated 180 with respect to the rest of the crystal. More layers of TM silicide epitaxially grown on Si(l 11) result in a hexagonal structure similar to bulk ScSi2 and YSi2: graphite-like Si planes (with vacancies) intercalated with TM planes, and forming a ({radical}3x{radical}3) arrangement with a ScSi{sub 1.7} and YSi{sub 1.7} stoichiometry. The top Si layer does not contain vacancies and it does not present a graphite-like structure, but forms a bilayer arrangement as in bulk Si. (Author)

  14. Doubly Reentrant Cavities Prevent Catastrophic Wetting Transitions on Intrinsically Wetting Surfaces

    KAUST Repository

    Domingues, Eddy

    2017-06-05

    Omniphobic surfaces, i.e. which repel all known liquids, have proven of value in applications ranging from membrane distillation to underwater drag reduction. A limitation of currently employed omniphobic surfaces is that they rely on perfluorinated coatings, increasing cost and environmental impact, and preventing applications in harsh environments. There is, thus, a keen interest in rendering conventional materials, such as plastics, omniphobic by micro/nano-texturing rather than via chemical make-up, with notable success having been achieved for silica surfaces with doubly reentrant micropillars. However, we found a critical limitation of microtextures comprising of pillars that they undergo catastrophic wetting transitions (apparent contact angles, θr → 0° from θr > 90°) in the presence of localized physical damages/defects or on immersion in wetting liquids. In response, a doubly reentrant cavity microtexture is introduced, which can prevent catastrophic wetting transitions in the presence of localized structural damage/defects or on immersion in wetting liquids. Remarkably, our silica surfaces with doubly reentrant cavities could exhibited apparent contact angles, θr ≈ 135° for mineral oil, where the intrinsic contact angle, θo ≈ 20°. Further, when immersed in mineral oil or water, doubly reentrant microtextures in silica (θo ≈ 40° for water) were not penetrated even after several days of investigation. Thus, microtextures comprising of doubly reentrant cavities might enable applications of conventional materials without chemical modifications, especially in scenarios that are prone to localized damages or immersion in wetting liquids, e.g. hydrodynamic drag reduction and membrane distillation.

  15. Dynamic Linkages Between the Transition Zone & Surface Plate Motions in 2D Models of Subduction

    Science.gov (United States)

    Arredondo, K.; Billen, M. I.

    2013-12-01

    While slab pull is considered the dominant force controlling plate motion and speed, its magnitude is controlled by slab behavior in the mantle, where tomographic studies show a wide range of possibilities from direct penetration to folding, or stagnation directly above the lower mantle (e.g. Fukao et al., 2009). Geodynamic studies have investigated various parameters, such as plate age and two phase transitions, to recreate observed behavior (e.g. Běhounková and Cízková, 2008). However, past geodynamic models have left out known slab characteristics that may have a large impact on slab behavior and our understanding of subduction processes. Mineral experiments and seismic observations have indicated the existence of additional phase transitions in the mantle transition zone that may produce buoyancy forces large enough to affect the descent of a subducting slab (e.g. Ricard et al., 2005). The current study systematically tests different common assumptions used in geodynamic models: kinematic versus free-slip boundary conditions, the effects of adiabatic heating, viscous dissipation and latent heat, compositional layering and a more complete suite of phase transitions. Final models have a complete energy equation, with eclogite, harzburgite and pyrolite lithosphere compositional layers, and seven composition-dependent phase transitions within the olivine, pyroxene and garnet polymorph minerals. Results show important feedback loops between different assumptions and new behavior from the most complete models. Kinematic models show slab weakening or breaking above the 660 km boundary and between compositional layers. The behavior in dynamic models with a free-moving trench and overriding plate is compared to the more commonly found kinematic models. The new behavior may have important implications for the depth distribution of deep earthquakes within the slab. Though the thermodynamic parameters of certain phase transitions may be uncertain, their presence and

  16. A sharp interface method for compressible liquid–vapor flow with phase transition and surface tension

    Energy Technology Data Exchange (ETDEWEB)

    Fechter, Stefan, E-mail: stefan.fechter@iag.uni-stuttgart.de [Institut für Aerodynamik und Gasdynamik, Universität Stuttgart, Pfaffenwaldring 21, 70569 Stuttgart (Germany); Munz, Claus-Dieter, E-mail: munz@iag.uni-stuttgart.de [Institut für Aerodynamik und Gasdynamik, Universität Stuttgart, Pfaffenwaldring 21, 70569 Stuttgart (Germany); Rohde, Christian, E-mail: Christian.Rohde@mathematik.uni-stuttgart.de [Institut für Angewandte Analysis und Numerische Simulation, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Zeiler, Christoph, E-mail: Christoph.Zeiler@mathematik.uni-stuttgart.de [Institut für Angewandte Analysis und Numerische Simulation, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)

    2017-05-01

    The numerical approximation of non-isothermal liquid–vapor flow within the compressible regime is a difficult task because complex physical effects at the phase interfaces can govern the global flow behavior. We present a sharp interface approach which treats the interface as a shock-wave like discontinuity. Any mixing of fluid phases is avoided by using the flow solver in the bulk regions only, and a ghost-fluid approach close to the interface. The coupling states for the numerical solution in the bulk regions are determined by the solution of local two-phase Riemann problems across the interface. The Riemann solution accounts for the relevant physics by enforcing appropriate jump conditions at the phase boundary. A wide variety of interface effects can be handled in a thermodynamically consistent way. This includes surface tension or mass/energy transfer by phase transition. Moreover, the local normal speed of the interface, which is needed to calculate the time evolution of the interface, is given by the Riemann solution. The interface tracking itself is based on a level-set method. The focus in this paper is the description of the two-phase Riemann solver and its usage within the sharp interface approach. One-dimensional problems are selected to validate the approach. Finally, the three-dimensional simulation of a wobbling droplet and a shock droplet interaction in two dimensions are shown. In both problems phase transition and surface tension determine the global bulk behavior.

  17. Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces.

    Science.gov (United States)

    Kuhl, Kendra P; Hatsukade, Toru; Cave, Etosha R; Abram, David N; Kibsgaard, Jakob; Jaramillo, Thomas F

    2014-10-08

    Fuels and industrial chemicals that are conventionally derived from fossil resources could potentially be produced in a renewable, sustainable manner by an electrochemical process that operates at room temperature and atmospheric pressure, using only water, CO2, and electricity as inputs. To enable this technology, improved catalysts must be developed. Herein, we report trends in the electrocatalytic conversion of CO2 on a broad group of seven transition metal surfaces: Au, Ag, Zn, Cu, Ni, Pt, and Fe. Contrary to conventional knowledge in the field, all metals studied are capable of producing methane or methanol. We quantify reaction rates for these two products and describe catalyst activity and selectivity in the framework of CO binding energies for the different metals. While selectivity toward methane or methanol is low for most of these metals, the fact that they are all capable of producing these products, even at a low rate, is important new knowledge. This study reveals a richer surface chemistry for transition metals than previously known and provides new insights to guide the development of improved CO2 conversion catalysts.

  18. Scaling properties of adsorption energies for hydrogen-containing molecules on transition-metal surfaces

    DEFF Research Database (Denmark)

    Abild-Pedersen, Frank; Greeley, Jeffrey Philip; Studt, Felix

    2007-01-01

    Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately with the adsorp......Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately...... with the adsorption energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions....

  19. Transition process leading to microbubble emission boiling on horizontal circular heated surface in subcooled pool

    Science.gov (United States)

    Ueno, Ichiro; Ando, Jun; Horiuchi, Kazuna; Saiki, Takahito; Kaneko, Toshihiro

    2016-11-01

    Microbubble emission boiling (MEB) produces a higher heat flux than critical heat flux (CHF) and therefore has been investigated in terms of its heat transfer characteristics as well as the conditions under which MEB occurs. Its physical mechanism, however, is not yet clearly understood. We carried out a series of experiments to examine boiling on horizontal circular heated surfaces of 5 mm and of 10 mm in diameter, in a subcooled pool, paying close attention to the transition process to MEB. High-speed observation results show that, in the MEB regime, the growth, condensation, and collapse of the vapor bubbles occur within a very short time. In addition, a number of fine bubbles are emitted from the collapse of the vapor bubbles. By tracking these tiny bubbles, we clearly visualize that the collapse of the vapor bubbles drives the liquid near the bubbles towards the heated surface, such that the convection field around the vapor bubbles under MEB significantly differs from that under nucleate boiling. Moreover, the axial temperature gradient in a heated block (quasi-heat flux) indicates a clear difference between nucleate boiling and MEB. A combination of quasi-heat flux and the measurement of the behavior of the vapor bubbles allows us to discuss the transition to MEB. This work was financially supported by the 45th Research Grant in Natural Sciences from The Mitsubishi Foundation (2014 - 2015), and by Research Grant for Boiler and Pressurized Vessels from The Japan Boiler Association (2016).

  20. Experimental and theoretical study on transition boiling concerning downward-facing horizontal surface in confined space

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, D.W. [State Key Laboratory of Multiphase Flow in Power Engineering, Department of Nuclear Science and Technology, Xi' an Jiaotong University 710049 (China); Su, G.H. [State Key Laboratory of Multiphase Flow in Power Engineering, Department of Nuclear Science and Technology, Xi' an Jiaotong University 710049 (China)], E-mail: ghsu@mail.xjtu.edu.cn; Tian, W.X. [State Key Laboratory of Multiphase Flow in Power Engineering, Department of Nuclear Science and Technology, Xi' an Jiaotong University 710049 (China); Sugiyama, K. [Faculty of Engineering, Hokkaido University Kita 13 Jo, Nishi 8 Chome, Kita-Ku, Sapporo 060-8628 (Japan); Qiu, S.Z. [State Key Laboratory of Multiphase Flow in Power Engineering, Department of Nuclear Science and Technology, Xi' an Jiaotong University 710049 (China)

    2008-09-15

    Experimental study has been conducted to examine the pool boiling occurs on a relative large downward-facing round surface with a diameter of 300 mm in confined water pool at atmospheric pressure. An artificial neural network (ANN) has been trained successfully based on the experimental data for predicting Nusselt number of transition boiling in the present study. The input parameters of the ANN are wall superheat, {delta}T{sub w}, the ratio of the gap size to the diameter of the heated surface, {delta}/D, Prandtl number and Rayleigh number. The output is Nusselt number, Nu. The results show that: Nu decreases with increasing {delta}T{sub w}, and increases generally with an increase of {delta}/D. Nu increases with increasing Pr when gap size is smaller than 4.0 mm. And Nu decreases initially and then increases with increasing Pr as gap size bigger than 5.0 mm. The results also indicate that the influence of Grashof number, Gr, could be negligible. Finally, a new correlation was proposed to predict the transition boiling heat transfer under the present condition. The comparisons between the prediction of the new correlation and experimental data show a reasonable agreement.

  1. Freezing for love: enacting 'responsible' reproductive citizenship through egg freezing.

    Science.gov (United States)

    Carroll, Katherine; Kroløkke, Charlotte

    2017-11-29

    The promise of egg freezing for women's fertility preservation entered feminist debate in connection with medical and commercial control over, and emancipation from, biological reproduction restrictions. In this paper we explore how women negotiate and make sense of the decision to freeze their eggs. Our analysis draws on semi-structured interviews with 16 women from the Midwest and East Coast regions of the USA who froze their eggs. Rather than freezing to balance career choices and 'have it all', the women in this cohort were largely 'freezing for love' and in the hope of having their 'own healthy baby'. This finding extends existing feminist scholarship and challenges bioethical concerns about egg freezing by drawing on the voices of women who freeze their eggs. By viewing egg freezing as neither exclusively liberation nor oppression or financial exploitation, this study casts egg freezing as an enactment of 'responsible' reproductive citizenship that 'anticipates coupledom' and reinforces the genetic relatedness of offspring.

  2. Freeze for action: Neurobiological mechanisms in animal and human freezing

    NARCIS (Netherlands)

    Roelofs, K.

    2017-01-01

    Upon increasing levels of threat, animals activate qualitatively different defensive modes, including freezing and active fight-or-flight reactions. Whereas freezing is a form of behavioural inhibition accompanied by parasympathetically dominated heart rate deceleration, fight-or-flight reactions

  3. Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films.

    Science.gov (United States)

    Pesquera, D; Herranz, G; Barla, A; Pellegrin, E; Bondino, F; Magnano, E; Sánchez, F; Fontcuberta, J

    2012-01-01

    The electron occupancy of 3d-orbitals determines the properties of transition metal oxides. This can be achieved, for example, through thin-film heterostructure engineering of ABO(3) oxides, enabling emerging properties at interfaces. Interestingly, epitaxial strain may break the degeneracy of 3d-e(g) and t(2g) orbitals, thus favoring a particular orbital filling with consequences for functional properties. Here we disclose the effects of symmetry breaking at free surfaces of ABO(3) perovskite epitaxial films and show that it can be combined with substrate-induced epitaxial strain to tailor at will the electron occupancy of in-plane and out-of-plane surface electronic orbitals. We use X-ray linear dichroism to monitor the relative contributions of surface, strain and atomic terminations to the occupancy of 3z(2)-r(2) and x(2)-y(2) orbitals in La(2/3)Sr(1/3)MnO(3) films. These findings open the possibility of an active tuning of surface electronic and magnetic properties as well as chemical properties (catalytic reactivity, wettability and so on).

  4. Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides

    Science.gov (United States)

    White, A.F.; Peterson, M.L.

    1996-01-01

    Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1-7 at 25??C. For an aqueous transition metal m, such reactions are 3[Fe2+Fe3+2]O4(magnetite) + 2/nmz ??? 4[Fe3+2]O3(maghemite) + Fe2+ + 2/nmz-n and 3[Fe2+Ti]O3(ilmenite) + 2/nmz ??? Fe3+2Ti3O9(pseudorutile) + Fe2+ + 2/nmz-n, where z is the valance state and n is the charge transfer number. The half cell potential range for solid state oxidation [Fe(II)] ??? [Fe(III)] is -0.34 to -0.65 V, making structural Fe(II) a stronger reducing agent than aqueous Fe2+ (-0.77 V). Reduction rates for aqueous metal species are linear with time (up to 36 h), decrease with pH, and have rate constants between 0.1 and 3.3 ?? 10-10 mol m-2 s-1. Iron is released to solution both from the above reactions and from dissolution of the oxide surface. In the presence of chromate, Fe2+ is oxidized homogeneously in solution to Fe3+. X-ray photoelectron spectroscopy (XPS) denotes a Fe(III) oxide surface containing reduced Cr(III) and V(IV) species. Magnetite and ilmenite electrode potentials are insensitive to increases in divalent transition metals including Zn(II), Co(II), Mn(II), and Ni(II) and reduced V(IV) and Cr(III) but exhibit a log-linear concentration-potential response to Fe(III) and Cu(II). Complex positive electrode responses occur with increasing Cr(VI) and V(V) concentrations. Potential dynamic scans indicate that the high oxidation potential of dichromate is capable of suppressing the cathodic reductive dissolution of magnetite. Oxide electrode potentials are determined by the Fe(II)/Fe(III) composition of the oxide surface and respond to aqueous ion potentials which accelerate this oxidation process. Natural magnetite sands weathered under anoxic conditions are electrochemically reactive as demonstrated by rapid chromate reduction and the release of aqueous Fe(III) to experimental

  5. Development of the Soil Moisture Active Passive (SMAP) radiometer derived landscape freeze/thaw product

    Science.gov (United States)

    Colliander, A.; Xu, X.; Dunbar, R. S.; Derksen, C.; Kim, Y.; Kimball, J. S.

    2016-12-01

    A baseline SMAP mission objective was to determine the land surface binary freeze/thaw (FT) state for northern (>45°N) regions with 80% spatial classification accuracy at 3 km resolution and 2-day average intervals. These requirements were initially achieved from the SMAP radar until the sensor failed in July 2015. The FT algorithm is now transitioning to using SMAP radiometer inputs. The main compromises of this change are a coarse (36 km) radiometer footprint, enhanced noise and potential FT signal degradation from seasonal vegetation biomass, soil moisture and surface inundation changes. The new daily passive FT product (L3_FT_P) is based on the same seasonal threshold algorithm as the radar derived product (L3_FT_A): instantaneous SMAP measurements are compared to reference signatures acquired during seasonal frozen and thawed states. Instead of radar inputs, the normalized polarization ratio (NPR) is calculated from SMAP radiometer measurements. The L3_FT_P algorithm is applied using NPR inputs, whereby NPR decreases and increases are associated with respective landscape freezing and thawing. A lower NPR under frozen conditions is due to smaller V-pol brightness temperature increases and larger H-pol increases. Using in situ measurements from core validation sites, the temporal behavior of backscatter and NPR measurements were evaluated during the spring 2015 radar and radiometer overlap period. The transition from frozen to thawed states produced a NPR response similar in timing and magnitude to the radar response, resulting in similar freeze to thaw seasonal transition dates. While the post-thaw radar backscatter consistently remained at elevated values relative to the frozen state, the NPR drifted downwards following the main thaw transition (due to de-polarization of the scene), which may introduce false freeze classification errors. Both radar and radiometer results tended to lead observed soil thawing due to strong sensitivity of the microwave

  6. Characterization of a laboratory-scale container for freezing protein solutions with detailed evaluation of a freezing process simulation.

    Science.gov (United States)

    Roessl, Ulrich; Jajcevic, Dalibor; Leitgeb, Stefan; Khinast, Johannes G; Nidetzky, Bernd

    2014-02-01

    A 300-mL stainless steel freeze container was constructed to enable QbD (Quality by Design)-compliant investigations and the optimization of freezing and thawing (F/T) processes of protein pharmaceuticals at moderate volumes. A characterization of the freezing performance was conducted with respect to freezing kinetics, temperature profiling, cryoconcentration, and stability of the frozen protein. Computational fluid dynamic (CFD) simulations of temperature and phase transition were established to facilitate process scaling and process analytics as well as customization of future freeze containers. Protein cryoconcentration was determined from ice-core samples using bovine serum albumin. Activity, aggregation, and structural perturbation were studied in frozen rabbit muscle l-lactic dehydrogenase (LDH) solution. CFD simulations provided good qualitative and quantitative agreement with highly resolved experimental measurements of temperature and phase transition, allowing also the estimation of spatial cryoconcentration patterns. LDH exhibited stability against freezing in the laboratory-scale system, suggesting a protective effect of cryoconcentration at certain conditions. The combination of the laboratory-scale freeze container with accurate CFD modeling will allow deeper investigations of F/T processes at advanced scale and thus represents an important step towards a better process understanding. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  7. Freezing-induced uptake of disaccharides for preservation of chromatin in freeze-dried stallion sperm during accelerated aging.

    Science.gov (United States)

    Oldenhof, Harriëtte; Zhang, Miao; Narten, Katharina; Bigalk, Judith; Sydykov, Bulat; Wolkers, Willem F; Sieme, Harald

    2017-11-07

    Non-viable freeze-dried sperm have intact chromatin and can be used for fertilization via intracytoplasmic sperm injection. Freeze-dried sperm preferably should be stored at 4°C or lower, because DNA damage accumulates during storage at room temperature. Disaccharides are known to protect biomolecules both during freezing and drying, by forming a highly viscous glassy state. Their use for intracellular protection is challenging because cellular membranes are normally impermeable for disaccharides. In the current study, we demonstrate that membrane impermeable compounds, including lucifer yellow and trehalose, are taken up by stallion sperm when exposed to freezing. Trehalose uptake likely occurs during freezing-induced membrane phase transitions, but does not allow sperm to survive drying. Stallion sperm was freeze-dried in various formulations consisting of reducing or non-reducing sugars combined with albumin as bulking agent. Chromatin stability was studied during storage at 37°C, using the flow cytometric sperm chromatin structure assay and microscopic assessment of chromatin dispersion and DNA fragmentation after electrophoresis. Freeze-drying did not affect sperm chromatin, irrespective of the formulation that was used. DNA fragmentation index (DFI) values ranged from 5 - 8%. If sperm was freeze-dried without protectants or in a combination of glucose and proteins, DNA damage rapidly accumulated during storage at 37°C, reaching DFI values of respectively 95 ± 4 and 64 ± 42% after 1 month. DFI values of sperm freeze-dried with sucrose or trehalose ranged between 9 - 11% and 33 - 52% after 1 and 3 months storage, respectively. In conclusion, freeze-drying sperm with disaccharides results in uptake during freezing, which greatly reduces chromatin degradation during dried storage. © The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e

  8. Administrative Freezing of Capital Construction

    Directory of Open Access Journals (Sweden)

    Kropacheva A. V.

    2015-07-01

    Full Text Available The author estimates administrative freezing of capital construction as a type of punishment for violating laws in this sphere. The article provides the mechanism of freezing of capital construction as a serious alternative for fine sanctions

  9. Response of seasonal soil freeze depth to climate change across China

    Science.gov (United States)

    Peng, Xiaoqing; Zhang, Tingjun; Frauenfeld, Oliver W.; Wang, Kang; Cao, Bin; Zhong, Xinyue; Su, Hang; Mu, Cuicui

    2017-05-01

    The response of seasonal soil freeze depth to climate change has repercussions for the surface energy and water balance, ecosystems, the carbon cycle, and soil nutrient exchange. Despite its importance, the response of soil freeze depth to climate change is largely unknown. This study employs the Stefan solution and observations from 845 meteorological stations to investigate the response of variations in soil freeze depth to climate change across China. Observations include daily air temperatures, daily soil temperatures at various depths, mean monthly gridded air temperatures, and the normalized difference vegetation index. Results show that soil freeze depth decreased significantly at a rate of -0.18 ± 0.03 cm yr-1, resulting in a net decrease of 8.05 ± 1.5 cm over 1967-2012 across China. On the regional scale, soil freeze depth decreases varied between 0.0 and 0.4 cm yr-1 in most parts of China during 1950-2009. By investigating potential climatic and environmental driving factors of soil freeze depth variability, we find that mean annual air temperature and ground surface temperature, air thawing index, ground surface thawing index, and vegetation growth are all negatively associated with soil freeze depth. Changes in snow depth are not correlated with soil freeze depth. Air and ground surface freezing indices are positively correlated with soil freeze depth. Comparing these potential driving factors of soil freeze depth, we find that freezing index and vegetation growth are more strongly correlated with soil freeze depth, while snow depth is not significant. We conclude that air temperature increases are responsible for the decrease in seasonal freeze depth. These results are important for understanding the soil freeze-thaw dynamics and the impacts of soil freeze depth on ecosystem and hydrological process.

  10. Transitioning Enhanced Land Surface Initialization and Model Verification Capabilities to the Kenya Meteorological Department (KMD)

    Science.gov (United States)

    Case, Jonathan L.; Mungai, John; Sakwa, Vincent; Zavodsky, Bradley T.; Srikishen, Jayanthi; Limaye, Ashutosh; Blankenship, Clay B.

    2016-01-01

    Flooding, severe weather, and drought are key forecasting challenges for the Kenya Meteorological Department (KMD), based in Nairobi, Kenya. Atmospheric processes leading to convection, excessive precipitation and/or prolonged drought can be strongly influenced by land cover, vegetation, and soil moisture content, especially during anomalous conditions and dry/wet seasonal transitions. It is thus important to represent accurately land surface state variables (green vegetation fraction, soil moisture, and soil temperature) in Numerical Weather Prediction (NWP) models. The NASA SERVIR and the Short-term Prediction Research and Transition (SPoRT) programs in Huntsville, AL have established a working partnership with KMD to enhance its regional modeling capabilities. SPoRT and SERVIR are providing experimental land surface initialization datasets and model verification capabilities for capacity building at KMD. To support its forecasting operations, KMD is running experimental configurations of the Weather Research and Forecasting (WRF; Skamarock et al. 2008) model on a 12-km/4-km nested regional domain over eastern Africa, incorporating the land surface datasets provided by NASA SPoRT and SERVIR. SPoRT, SERVIR, and KMD participated in two training sessions in March 2014 and June 2015 to foster the collaboration and use of unique land surface datasets and model verification capabilities. Enhanced regional modeling capabilities have the potential to improve guidance in support of daily operations and high-impact weather and climate outlooks over Eastern Africa. For enhanced land-surface initialization, the NASA Land Information System (LIS) is run over Eastern Africa at 3-km resolution, providing real-time land surface initialization data in place of interpolated global model soil moisture and temperature data available at coarser resolutions. Additionally, real-time green vegetation fraction (GVF) composites from the Suomi-NPP VIIRS instrument is being incorporated

  11. Near-surface dynamics of a separated jet in the coastal transition zone off Oregon

    Science.gov (United States)

    Koch, A. O.; Kurapov, A. L.; Allen, J. S.

    2010-08-01

    Three-dimensional circulation in the coastal transition zone (CTZ) off Oregon is studied using a 3 km resolution model based on the Regional Ocean Modeling System. The study period is spring and summer 2002, when extensive observations were available from the northeastern Pacific component of the Global Ocean Ecosystems Dynamics project. Our main focus is on near-surface transports, particularly in an area off Cape Blanco where an energetic coastal current is separated in the CTZ. Comparisons with available observations (velocities from midshelf moorings, surface velocities from high-frequency radars, satellite sea surface temperature maps, along-track sea surface height altimetry, and SeaSoar hydrography) show that the model reproduces qualitatively correctly the flow structure and variability in the study area. The near-surface flow behavior during 26 July to 21 August, a late-summer time period of strong, time-variable southward winds, is examined. During that period the coastal jet separates from the continental shelf around Cape Blanco (43°N). The energetic separated jet continues to flow southward in a near-coastal region between 42.2°N and 43°N. It subsequently turns around 42°N to flow westward offshore past 127°W. Relatively vigorous up- and downwelling is found concentrated in the region of the separated jet. Frontogenesis secondary circulation, nonlinear effects of the relative vorticity on the ageostrophic Ekman transport, and submesoscale instabilities contribute to the vertical circulation within the jet. Vertical velocities are found to reach 50 m d-1 in the offshore part of the jet and 100 m d-1 in the near-coastal part, where the jet is aligned with the wind direction.

  12. DPPC Monolayers Exhibit an Additional Phase Transition at High Surface Pressure

    DEFF Research Database (Denmark)

    Shen, Chen; de la Serna, Jorge B.; Struth, Bernd

    2015-01-01

    Pulmonary surfactant forms a monolayer at the air/aqueous interface within the lung. During the breath process, the surface pressure (Π) periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. Pulmonary surfactant consists of ~90......% of lipid with 10% integrated proteins. Among its lipid compounds, di-palmitoyl-phosphatidylcholine (DPPC) dominates (~45wt%). DPPC is the only known lipid that can be compressed to very high surface pressure (~70mN/m) before its monolayer collapses. Most probably, this feature contributes to the mechanical....... Here, we report a second phase transition at elevated surface pressure (~50mN/m). The lateral structure of the monolayer at selected states (8mN/m, 20mN/m, 30mN/m, 40mN/m, 50mN/m, 60mN/m, 70mN/m; covering the whole pressure range of the isotherm) was investigated by grazing incidence X-ray diffraction...

  13. Analogy between the quantum phase transition and the polarization switching of vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Yen, Tsu-Chiang; Wu, Yu-Heng; Li, Yueh-Chen; Kuo, Wang-Chuang

    2014-05-01

    The phase transition in the polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs) was recently reported to be a second-order phase transition (SOPT). However, some features of this phase transition indicate that the VCSEL's PS (VPS) is different from the traditional SOPTs. Most of the phase transition investigations of the laser employ the laser's intensity as the order parameter. In Landau's paradigm, that parameter evolutes from zero to non-zero values, or vice versa, during SOPTs, corresponding to a transition between a disordered phase and an ordered phase. Nevertheless, in the VPS, the laser's intensity remains constant before and after the PS, revealing an order-to-order transition. Furthermore, the laser's transverse modes cannot transfer to each other through continuous deformations in geometry. That feature attributes a topological characteristic to the laser's transverse modes. The spatial coherence of the laser also implements a globally geometric characteristic to the laser's output. Accordingly, there are two similarities between the VPS and quantum phase transitions (QPTs) with topological order. First, both of them belong to the orderto- order phase transitions. Second, in both transitions, two ground states are orthogonal, and are degenerate at the critical point. This paper investigated the analogy between the QPT with topological order and the VPS, exploring that the VPS has a potential to simulate the QPTs of other physical systems.

  14. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

    Science.gov (United States)

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-05-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ~80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg~1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity.

  15. Study of the individual contributions of ice formation and freeze-concentration on isothermal stability of lactate dehydrogenase during freezing.

    Science.gov (United States)

    Bhatnagar, Bakul S; Pikal, Michael J; Bogner, Robin H

    2008-02-01

    The objective of this study was to determine the individual contributions of ice formation, solute concentration, temperature, and time, to irreversible protein denaturation during freezing. A temperature-step approach was used to study isothermal degradation of frozen lactate dehydrogenase (LDH). The freeze-concentrate composition was determined using differential scanning calorimetry to enable preparation of solutions, without ice, of the same concentration as the freeze-concentrate, and thereby determine the role of the freeze-concentrate composition on LDH degradation. Both stabilizers employed in the study, hydroxyethyl starch and sucrose, conferred cryoprotection on LDH. While LDH stability was lower at 1.50-3.25% w/v sucrose than in the absence of sucrose, cryoprotection was restored at higher sucrose concentrations. pH shift during freezing, degree of supercooling, and excipient impurities were ruled out as causes for unusual LDH stability behavior at lower sucrose concentrations. Specific surface area measurements of the freeze-dried cakes showed that the ice surface area increased with an increase in sucrose concentration. No LDH degradation occurred in concentrated solutions, without ice, at the same composition as the freeze-concentrate in frozen systems where massive degradation was documented. Thus, ice formation is the critical destabilizing factor during freezing of LDH in sucrose:citrate buffer systems.

  16. Surface chemistry. Probing the transition state region in catalytic CO oxidation on Ru.

    Science.gov (United States)

    Öström, H; Öberg, H; Xin, H; LaRue, J; Beye, M; Dell'Angela, M; Gladh, J; Ng, M L; Sellberg, J A; Kaya, S; Mercurio, G; Nordlund, D; Hantschmann, M; Hieke, F; Kühn, D; Schlotter, W F; Dakovski, G L; Turner, J J; Minitti, M P; Mitra, A; Moeller, S P; Föhlisch, A; Wolf, M; Wurth, W; Persson, M; Nørskov, J K; Abild-Pedersen, F; Ogasawara, H; Pettersson, L G M; Nilsson, A

    2015-02-27

    Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the O K-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model. Copyright © 2015, American Association for the Advancement of Science.

  17. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    Directory of Open Access Journals (Sweden)

    Wei Xun

    2017-07-01

    Full Text Available Based on first-principles calculations, the BaTiO3(BTO film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

  18. Nanoscale capillary freezing of ionic liquids confined between metallic interfaces and the role of electronic screening

    Science.gov (United States)

    Comtet, Jean; Niguès, Antoine; Kaiser, Vojtech; Coasne, Benoit; Bocquet, Lydéric; Siria, Alessandro

    2017-06-01

    Room-temperature ionic liquids (RTILs) are new materials with fundamental importance for energy storage and active lubrication. They are unusual liquids, which challenge the classical frameworks of electrolytes, whose behaviour at electrified interfaces remains elusive, with exotic responses relevant to their electrochemical activity. Using tuning-fork-based atomic force microscope nanorheological measurements, we explore here the properties of confined RTILs, unveiling a dramatic change of the RTIL towards a solid-like phase below a threshold thickness, pointing to capillary freezing in confinement. This threshold is related to the metallic nature of the confining materials, with more metallic surfaces facilitating freezing. This behaviour is interpreted in terms of the shift of the freezing transition, taking into account the influence of the electronic screening on RTIL wetting of the confining surfaces. Our findings provide fresh views on the properties of confined RTIL with implications for their properties inside nanoporous metallic structures, and suggests applications to tune nanoscale lubrication with phase-changing RTILs, by varying the nature and patterning of the substrate, and application of active polarization.

  19. Nanoscale capillary freezing of ionic liquids confined between metallic interfaces and the role of electronic screening.

    Science.gov (United States)

    Comtet, Jean; Niguès, Antoine; Kaiser, Vojtech; Coasne, Benoit; Bocquet, Lydéric; Siria, Alessandro

    2017-06-01

    Room-temperature ionic liquids (RTILs) are new materials with fundamental importance for energy storage and active lubrication. They are unusual liquids, which challenge the classical frameworks of electrolytes, whose behaviour at electrified interfaces remains elusive, with exotic responses relevant to their electrochemical activity. Using tuning-fork-based atomic force microscope nanorheological measurements, we explore here the properties of confined RTILs, unveiling a dramatic change of the RTIL towards a solid-like phase below a threshold thickness, pointing to capillary freezing in confinement. This threshold is related to the metallic nature of the confining materials, with more metallic surfaces facilitating freezing. This behaviour is interpreted in terms of the shift of the freezing transition, taking into account the influence of the electronic screening on RTIL wetting of the confining surfaces. Our findings provide fresh views on the properties of confined RTIL with implications for their properties inside nanoporous metallic structures, and suggests applications to tune nanoscale lubrication with phase-changing RTILs, by varying the nature and patterning of the substrate, and application of active polarization.

  20. Initiation of urinary bladder carcinogenesis in rats by freeze ulceration with sodium saccharin promotion.

    Science.gov (United States)

    Hasegawa, R; Greenfield, R E; Murasaki, G; Suzuki, T; Cohen, S M

    1985-04-01

    Sodium saccharin was previously shown to induce a significant incidence of transitional cell carcinoma of the bladder when administered to rats either immediately or beginning 2 weeks after ulceration of the bladder epithelium induced by freezing or cyclophosphamide injection. However, the marked regenerative hyperplasia following ulceration by either of these methods is not completely repaired until 3 to 4 weeks after ulceration. To determine whether initiation in this model was due to the ulceration and regenerative hyperplasia alone or if it was due to the administration of sodium saccharin acting on the hyperplastic epithelium, the effect of administering sodium saccharin at various times after ulceration was examined. Five-week-old F344 male rats were given sodium saccharin as 5% of the diet beginning either immediately (Group 1) or 2, 4, 6, or 18 weeks (Groups 2, 3, 4, or 5, respectively) after freezing of the bladder, and sacrificed 2 years after the start of the experiment. The incidences of rats with transitional cell carcinoma of the bladder were 11 of 36 rats (31%) in Group 1, 6 of 36 (17%) in Group 2, 12 of 40 (30%) in Group 3, 7 of 36 (19%) in Group 4, and 9 of 39 (23%) in Group 5. Sodium saccharin without prior ulceration induced a transitional cell papilloma in one rat, and freeze ulceration without subsequent sodium saccharin induced a transitional cell carcinoma in one rat. No bladder lesions were seen in the untreated control rats. Scanning electron microscopic examination of rats fed sodium saccharin after ulceration showed evidence of multifocal hyperplasia and significant surface changes either at Week 18 of the experiment (Groups 1 to 3) or 18 weeks after beginning sodium saccharin administration (Groups 4 and 5). These results indicate that freeze ulceration of the bladder induced irreversible changes in the epithelial cells related to bladder cancer initiation even though the regenerative hyperplasia is morphologically reversible, and that

  1. Transition metal oxides deposited on rhodium and platinum: Surface chemistry and catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Boffa, Alexander Bowman [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1994-07-01

    The surface chemistry and catalytic reactivity of transition metal oxides deposited on Rh and Pt substrates has been examined in order to establish the role of oxide-metal interactions in influencing catalytic activity. The oxides investigated included titanium oxide (TiOx), vanadium oxide (VOx), iron oxide (FeOx), zirconium oxide (ZrOx), niobium oxide (NbOx), tantalum oxide (TaOx), and tungsten oxide (WOx). The techniques used to characterize the sample included AES, XPS, LEED, TPD, ISS, and STM. After characterization of the surface in UHV, the sample was enclosed in an atmospheric reaction cell to measure the influence of the oxide deposits on the catalytic activity of the pure metal for CO and CO2 hydrogenation. The oxide deposits were found to strongly enhance the reactivity of the Rh foil. The rates of methane formation were promoted by up to 15 fold with the maximum in rate enhancement occurring at oxide coverages of approximately 0.5 ML. TiOx TaOx, and NbOx were the most effective promoters and were stable in the highest oxidation states during both reactions (compared to VOx, WOx, and FeOx). The trend in promoter effectiveness was attributed to the direct relationship between oxidation state and Lewis acidity. Bonding at the metal oxide/metal interface between the oxygen end of adsorbed CO and the Lewis acidic oxide was postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 192 refs.

  2. An X-ray diffraction investigation of the charge density wave transition at the NbSe2 surface

    OpenAIRE

    Murphy, Bridget M.

    2004-01-01

    Niobium diselenide 2H-NbSe2 is a van der Waals bonded layered structure, which undergoes a charge density wave transition (CDW). We have investigated the CDW transition in NbSe2 using grazing incidence X-ray diffraction. The evolution of a satellite reflection associated with the CDW has been observed above and below the critical angle of total external reflection in order to carry out a direct comparison between the surface and bulk behaviour. We successfully isolated the surface CDW structu...

  3. Stability and structural phase transitions of cobalt porphyrin adlayers on Au(100) surfaces.

    Science.gov (United States)

    Yoshimoto, Soichiro

    2013-08-14

    The stability and phase transitions of adlayers of two cobalt(II) porphyrins, 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (CoTPP) and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine cobalt(II) (CoOEP), formed on Au(100) were investigated under electrochemical conditions. In situ scanning tunneling microscopy (STM) was employed to investigate the structure of CoTPP and CoOEP adlayers in 0.1 M HClO4. The CoTPP and CoOEP adlayer structures were varied with the modification time and the concentration. The in situ STM observations showed that the underlying reconstructed atomic structure was lifted to a (1 × 1) atomic arrangement by either the adsorption of CoTPP/CoOEP during modification in a benzene solution or positive potential manipulation in 0.1 M HClO4. Ordered CoTPP arrays with two different hexagonal and square packing arrangements were found on an Au(100)-(1 × 1) surface, along with characteristic Au islands. The CoOEP molecules also formed a close-packed hexagonal structure on an Au(100)-(hex) surface; CoOEP molecules were arranged in a semi-square structure on the Au(100)-(1 × 1) surface by the lifting of reconstruction. The results of this study showed that the interaction between the cobalt porphyrins and the Au(100) substrate depended on the modification conditions and the electrochemical potential.

  4. The influence of freezing rates on bovine pericardium tissue Freeze-drying

    Directory of Open Access Journals (Sweden)

    Camila Figueiredo Borgognoni

    2009-12-01

    Full Text Available The bovine pericardium has been used as biomaterial in developing bioprostheses. Freeze-drying is a drying process that could be used for heart valve's preservation. The maintenance of the characteristics of the biomaterial is important for a good heart valve performance. This paper describes the initial step in the development of a bovine pericardium tissue freeze-drying to be used in heart valves. Freeze-drying involves three steps: freezing, primary drying and secondary drying. The freezing step influences the ice crystal size and, consequently, the primary and secondary drying stages. The aim of this work was to investigate the influence of freezing rates on the bovine pericardium tissue freeze-drying parameters. The glass transition temperature and the structural behaviour of the lyophilized tissues were determined as also primary and secondary drying time. The slow freezing with thermal treatment presented better results than the other freeze-drying protocols.O pericárdio bovino é um material utilizado na fabricação de biopróteses. A liofilização é um método de secagem que vem sendo estudado para a conservação de válvulas cardíacas. A preservação das características do biomaterial é de fundamental importância no bom funcionamento das válvulas. Este artigo é a primeira etapa do desenvolvimento do ciclo de liofilização do pericárdio bovino. Liofilização é o processo de secagem no qual a água é removida do material congelado por sublimação e desorção da água incongelável, sob pressão reduzida. O congelamento influencia o tamanho do cristal de gelo e, consequentemente, a secagem primária e secundária. O objetivo deste estudo foi verificar a influência das taxas de congelamento nos parâmetros de liofilização do pericárdio bovino. Determinou-se a temperatura de transição vítrea e o comportamento estrutural do pericárdio bovino liofilizado. Determinou-se o tempo da secagem primária e secundária. O

  5. Surface tension effects on the phase transition of a DPPC bilayer with and without protein: a molecular dynamics simulation.

    Science.gov (United States)

    Kong, Xian; Qin, Shanshan; Lu, Diannan; Liu, Zheng

    2014-05-14

    While the surface tension of a cell membrane, or a plasma membrane, regulates cell functions, little is known about its effect on the conformational changes of the lipid bilayer and hence the resulting changes in the cell membrane. To obtain some insights into the phase transition of the lipid bilayer as a function of surface tension, we used a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer as a model lipid bilayer and aquaporin (AqpZ), a transmembrane channel protein for water, as a model embedded protein. A coarse-grained molecular dynamics simulation was applied to illustrate the phase transition behavior of the pure DPPC bilayer and aquaporin-embedded DPPC bilayer under different surface tensions. It was shown that an increased surface tension reduced the phase transition temperature of the DPPC bilayer. As for the DPPC bilayer in gel form, no significant changes occurred in the structure of the bilayer in response to the surface tension. Once in a liquid crystal state, both the structure and properties of the DPPC bilayer, such as area per lipid, lipid order parameters, bilayer thickness and lateral diffusion coefficients, were responsive to the magnitude of surface tension in a linear way. The presence of aquaporin attenuated the compact alignment of the lipid bilayer, hindered the parallel movement, and thus made the DPPC bilayer less sensitive to the surface tension.

  6. Cell surface glycan alterations in epithelial mesenchymal transition process of Huh7 hepatocellular carcinoma cell.

    Directory of Open Access Journals (Sweden)

    Shan Li

    Full Text Available BACKGROUND AND OBJECTIVE: Due to recurrence and metastasis, the mortality of Hepatocellular carcinoma (HCC is high. It is well known that the epithelial mesenchymal transition (EMT and glycan of cell surface glycoproteins play pivotal roles in tumor metastasis. The goal of this study was to identify HCC metastasis related differential glycan pattern and their enzymatic basis using a HGF induced EMT model. METHODOLOGY: HGF was used to induce HCC EMT model. Lectin microarray was used to detect the expression of cell surface glycan and the difference was validated by lectin blot and fluorescence cell lectin-immunochemistry. The mRNA expression levels of glycotransferases were determined by qRT-PCR. RESULTS: After HGF treatment, the Huh7 cell lost epithelial characteristics and obtained mesenchymal markers. These changes demonstrated that HGF could induce a typical cell model of EMT. Lectin microarray analysis identified a decreased affinity in seven lectins ACL, BPL, JAC, MPL, PHA-E, SNA, and SBA to the glycan of cell surface glycoproteins. This implied that glycan containing T/Tn-antigen, NA2 and bisecting GlcNAc, Siaα2-6Gal/GalNAc, terminal α or βGalNAc structures were reduced. The binding ability of thirteen lectins, AAL, LCA, LTL, ConA, NML, NPL, DBA, HAL, PTL II, WFL, ECL, GSL II and PHA-L to glycan were elevated, and a definite indication that glycan containing terminal αFuc and ± Sia-Le, core fucose, α-man, gal-β(α GalNAc, β1,6 GlcNAc branching and tetraantennary complex oligosaccharides structures were increased. These results were further validated by lectin blot and fluorescence cell lectin-immunochemistry. Furthermore, the mRNA expression level of Mgat3 decreased while that of Mgat5, FucT8 and β3GalT5 increased. Therefore, cell surface glycan alterations in the EMT process may coincide with the expression of glycosyltransferase. CONCLUSIONS: The findings of this study systematically clarify the alterations of cell surface

  7. Adsorbate-Induced Anchoring Transitions of Liquid Crystals on Surfaces Presenting Metal Salts with Mixed Anions

    Science.gov (United States)

    Hunter, Jacob T.; Abbott, Nicholas L.

    2014-01-01

    We report that metal salts composed of mixtures of anions of differing coordination strength can be used to increase the sensitivity and selectivity of adsorbate-induced anchoring transitions of liquid crystals (LCs) supported on surfaces decorated with the metal salts. Specifically, the dynamics of anchoring transitions triggered by the adsorbate dimethyl methylphosphonate (DMMP) on surfaces of aluminum (III) salts were analyzed within the framework of a model for mass transport to reveal that the sensitivity of a nitrile-containing nematic LC to DMMP increased from 250 parts-per- billion (ppb) to 25 ppb when the composition of the (counter) anion was changed from 100% perchlorate to 90% nitrate and 10% perchlorate (by mole percent). To provide insight into these observations, Polarization-Modulation Infrared Reflectance-Absorbance Spectroscopy (PM-IRRAS) was used to show that the intensity of the absorption band in the IR spectrum corresponding to the coordinated state of the nitrile group (but not the position of the peak) decreased with increase in mole fraction of the strongly coordinating anion (nitrate) in the anion mixture, thus suggesting that the addition of the strongly coordinating anion decreased the number of coordination interactions (per unit area of the interface) but not the strength of the individual coordination interactions between the metal cation and the LC. We also measured the incorporation of the nitrate anion into the metal salt to decrease the effect of humidity on the dynamic response of the LC to DMMP, a result that is consistent with weaker interactions between the nitrate anion and water as compared to the perchlorate anion and water. Finally, the bidentate anion acetylacetonate was measured to cause a similar increase in sensitivity to DMMP when mixed with perchlorate in a 1:1 ratio (the resulting sensitivity of the system to DMMP was 100 ppb). Overall, these results suggest that tailoring the identity of the anion represents a

  8. Investigation of Seasonal Landscape Freeze/Thaw Cycles in Relation to Cloud Structure in the High Northern Latitudes

    Science.gov (United States)

    Smith, Cosmo

    2011-01-01

    The seasonal freezing and thawing of Earth's cryosphere (the portion of Earth's surface permanently or seasonally frozen) has an immense impact on Earth's climate as well as on its water, carbon and energy cycles. During the spring, snowmelt and the transition between frozen and non-frozen states lowers Earth's surface albedo. This change in albedo causes more solar radiation to be absorbed by the land surface, raising surface soil and air temperatures as much as 5 C within a few days. The transition of ice into liquid water not only raises the surface humidity, but also greatly affects the energy exchange between the land surface and the atmosphere as the phase change creates a latent energy dominated system. There is strong evidence to suggest that the thawing of the cryosphere during spring and refreezing during autumn is correlated to local atmospheric conditions such as cloud structure and frequency. Understanding the influence of land surface freeze/thaw cycles on atmospheric structure can help improve our understanding of links between seasonal land surface state and weather and climate, providing insight into associated changes in Earth's water, carbon, and energy cycles that are driven by climate change.Information on both the freeze/thaw states of Earth's land surface and cloud characteristics is derived from data sets collected by NOAA's Special Sensor Microwave/Imager (SSM/I), the Advanced Microwave Scanning Radiometer on NASA's Earth Observing System(AMSR-E), NASA's CloudSat, and NASA's SeaWinds-on-QuickSCAT Earth remote sensing satellite instruments. These instruments take advantage of the microwave spectrum to collect an ensemble of atmospheric and land surface data. Our analysis uses data from radars (active instruments which transmit a microwave signal toward Earth and measure the resultant backscatter) and radiometers (passive devices which measure Earth's natural microwave emission) to accurately characterize salient details on Earth's surface

  9. Freeze-Tolerant Condensers

    Science.gov (United States)

    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.

  10. Synthesis, structure, surface photovoltage spectra and photocatalytic activity of transition metal with triazine-pyrazole derivatives

    Science.gov (United States)

    Wang, Ying; Xu, Fen; Zhang, Li-Jing; Shi, Zhan; Xing, Yong-Heng; Bai, Feng-Ying

    2017-11-01

    Four new complexes, [Cd(L1)(NO3)2(H2O)] (1), [Co(L1)Cl2]·(CH3)2CO (2), {[Cu(L1)(μ-Cl)2CuCl2]·H2O·CH3CN}n (3) and [Ni(L1∗)2(H2O)2]·4H2O (4), were synthesized at room temperature or hydrothermal conditions based on triazine-pyrazole ligand L1 and L1* and transition metal Co (II), Ni (II), Cu (II) and Cd (II) salts. (L1: 2,4,6-tri(3,5-dimethyl-pyrazol-1-yl)-1,3,5-triazine; L1*: 6-(3,5-Dimethyl-2,5-dihydro-pyrazol-1-yl)-2,4-dione-1,3,5-triazine) The structures of all complexes were determined by elemental analysis, IR spectra, UV spectra and TG analysis. Through the X-ray single crystal diffraction showed that complexes 1 and 2 are 1D chain structures, complex 3 is a 3D network structure and complex 4 is a 2D network structure. In addition, the surface photovoltage spectroscopy (SPS) and electric-field-induced surface photovoltage spectroscopy (EFISPS) results indicate that all complexes can be used as p-type semiconductor. Furthermore, we investigated also the performance of the some complexes in the degradation of organic dyes RhB under UV irradiation. According to observe the experimental phenomenon, it is found that the tested complexes have different certain degree of photodegradation performances. Its photocatalytic effect is better than that of only hydrogen peroxide being involved in the reaction system under the same conditions.

  11. Hotspots in ground and surface water carbon fluxes through a freshwater to marine (mangrove) transition zone

    Science.gov (United States)

    Larsen, J.; Welti, N.; Hayes, M.; Lockington, D. A.

    2014-12-01

    The transfer of carbon and water from coastal freshwater wetlands to intertidal and marine zones is significant for sustaining ecosystem processes, particularly within mangroves environments. Large increases in carbon and nutrient fluxes within spatially confined zones (hotspots) are significant as drivers for broader cycling. How these processes relate to the transfers between surface and groundwater systems, as well as the transition from freshwater to marine environments, remains poorly understood. We investigated the flux of carbon and water from a freshwater wetland, to a saltmarsh and then mangroves, both within the main surface channel and within a comprehensive shallow groundwater bore network. We were able to characterise the main spatial trends in water gradients and mixing (using salinity, hydraulic gradients, stable water isotopes, and temperature) over seasonal cycles. In addition, at the same time we investigated the changes in dissolved organic carbon concentration and quality (fluorescence, UV), as well as nutrients (NO3, NH4). This revealed the river and tidal channel to be a significant export pathway for organic carbon, which was generally highly aromatic and recalcitrant. However, we also found that isolated sections of the brackish groundwater mixing zone between freshwater and marine provided a consistently high DOC 'hotspot' of very high quality carbon. This hotspot has high lateral groundwater gradients and therefore likely transports this carbon to the rest of the mangrove subsurface, where it is rapidly assimilated. These results imply large spatial heterogeneity in the carbon cycling between freshwater and marine environments, and have significant implications for the processing of the organic matter, and therefore also the respiration of greenhouse gases such as CO2 and CH4.

  12. On deriving flux freezing in magnetohydrodynamics by direct differentiation

    Science.gov (United States)

    Blackman, Eric G.

    2013-03-01

    The magnetic flux freezing theorem is a basic principle of ideal magnetohydrodynamics (MHD), a commonly used approximation to describe the aspects of astrophysical and laboratory plasmas. The theorem states that the magnetic flux—the integral of magnetic field penetrating a surface—is conserved in time as that surface is distorted in time by fluid motions. Pedagogues of MHD commonly derive flux freezing without showing how to take the material derivative of a general flux integral and/or assuming a vanishing field divergence from the outset. Here I avoid these shortcomings and derive flux freezing by direct differentiation, explicitly using a Jacobian to transform between the evolving field-penetrating surface at different times. The approach is instructive for its generality and helps elucidate the role of magnetic monopoles in breaking flux freezing. The paucity of appearances of this derivation in standard MHD texts suggests that its pedagogic value is underappreciated.

  13. Freeze Prediction Model

    Science.gov (United States)

    Morrow, C. T. (Principal Investigator)

    1981-01-01

    Measurements of wind speed, net irradiation, and of air, soil, and dew point temperatures in an orchard at the Rock Springs Agricultural Research Center, as well as topographical and climatological data and a description of the major apple growing regions of Pennsylvania were supplied to the University of Florida for use in running the P-model, freeze prediction program. Results show that the P-model appears to have considerable applicability to conditions in Pennsylvania. Even though modifications may have to be made for use in the fruit growing regions, there are advantages for fruit growers with the model in its present form.

  14. Surface geophysical methods for characterising frozen ground in transitional permafrost landscapes

    Science.gov (United States)

    Briggs, Martin; Campbell, Seth; Nolan, Jay; Walvoord, Michelle Ann; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D.; Lane, John W.

    2017-01-01

    The distribution of shallow frozen ground is paramount to research in cold regions, and is subject to temporal and spatial changes influenced by climate, landscape disturbance and ecosystem succession. Remote sensing from airborne and satellite platforms is increasing our understanding of landscape-scale permafrost distribution, but typically lacks the resolution to characterise finer-scale processes and phenomena, which are better captured by integrated surface geophysical methods. Here, we demonstrate the use of electrical resistivity imaging (ERI), electromagnetic induction (EMI), ground penetrating radar (GPR) and infrared imaging over multiple summer field seasons around the highly dynamic Twelvemile Lake, Yukon Flats, central Alaska, USA. Twelvemile Lake has generally receded in the past 30 yr, allowing permafrost aggradation in the receded margins, resulting in a mosaic of transient frozen ground adjacent to thick, older permafrost outside the original lakebed. ERI and EMI best evaluated the thickness of shallow, thin permafrost aggradation, which was not clear from frost probing or GPR surveys. GPR most precisely estimated the depth of the active layer, which forward electrical resistivity modelling indicated to be a difficult target for electrical methods, but could be more tractable in time-lapse mode. Infrared imaging of freshly dug soil pit walls captured active-layer thermal gradients at unprecedented resolution, which may be useful in calibrating emerging numerical models. GPR and EMI were able to cover landscape scales (several kilometres) efficiently, and new analysis software showcased here yields calibrated EMI data that reveal the complicated distribution of shallow permafrost in a transitional landscape.

  15. Evaluation of Spaceborne L-band Radiometer Measurements for Terrestrial Freeze/Thaw Retrievals in Canada

    Science.gov (United States)

    Roy, A.; Royer, A.; Derksen, C.; Brucker, L.; Langlois, A.; Mailon, A.; Kerr, Y.

    2015-01-01

    The landscape freeze/thaw (FT) state has an important impact on the surface energy balance, carbon fluxes, and hydrologic processes; the timing of spring melt is linked to active layer dynamics in permafrost areas. L-band (1.4 GHz) microwave emission could allow the monitoring of surface state dynamics due to its sensitivity to the pronounced permittivity difference between frozen and thawed soil. The aim of this paper is to evaluate the performance of both Aquarius and Soil Moisture and Ocean Salinity (SMOS) L-band passive microwave measurements using a polarization ratio-based algorithm for landscape FT monitoring. Weekly L-band satellite observations are compared with a large set of reference data at 48 sites across Canada spanning three environments: tundra, boreal forest, and prairies. The reference data include in situ measurements of soil temperature (Tsoil) and air temperature (Tair), and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) and snow cover area (SCA) products. Results show generally good agreement between Lband FT detection and the surface state estimated from four reference datasets. The best apparent accuracies for all seasons are obtained using Tair as the reference. Aquarius radiometer 2 (incidence angle of 39.6) data gives the best accuracies (90.8), while for SMOS the best results (87.8 of accuracy) are obtained at higher incidence angles (55- 60). The FT algorithm identifies both freeze onset and end with a delay of about one week in tundra and two weeks in forest and prairies, when compared to Tair. The analysis shows a stronger FT signal at tundra sites due to the typically clean transitions between consistently frozen and thawed conditions (and vice versa) and the absence of surface vegetation. Results in the prairies were poorer because of the influence of vegetation growth in summer (which decreases the polarization ratio) and the high frequency of ephemeral thaw events during winter. Freeze onset

  16. 9 CFR 590.534 - Freezing facilities.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 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 requirements...

  17. Performance Characteristics of an Isothermal Freeze Valve

    Energy Technology Data Exchange (ETDEWEB)

    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. Freeze for action: neurobiological mechanisms in animal and human freezing

    Science.gov (United States)

    2017-01-01

    Upon increasing levels of threat, animals activate qualitatively different defensive modes, including freezing and active fight-or-flight reactions. Whereas freezing is a form of behavioural inhibition accompanied by parasympathetically dominated heart rate deceleration, fight-or-flight reactions are associated with sympathetically driven heart rate acceleration. Despite the potential relevance of freezing for human stress-coping, its phenomenology and neurobiological underpinnings remain largely unexplored in humans. Studies in rodents have shown that freezing depends on amygdala projections to the brainstem (periaqueductal grey). Recent neuroimaging studies in humans have indicated that similar brain regions may be involved in human freezing. In addition, flexibly shifting between freezing and active defensive modes is critical for adequate stress-coping and relies on fronto-amygdala connections. This review paper presents a model detailing these neural mechanisms involved in freezing and the shift to fight-or-flight action. Freezing is not a passive state but rather a parasympathetic brake on the motor system, relevant to perception and action preparation. Study of these defensive responses in humans may advance insights into human stress-related psychopathologies characterized by rigidity in behavioural stress reactions. The paper therefore concludes with a research agenda to stimulate translational animal–human research in this emerging field of human defensive stress responses. This article is part of the themed issue ‘Movement suppression: brain mechanisms for stopping and stillness’. PMID:28242739

  19. Freeze for action: neurobiological mechanisms in animal and human freezing.

    Science.gov (United States)

    Roelofs, Karin

    2017-04-19

    Upon increasing levels of threat, animals activate qualitatively different defensive modes, including freezing and active fight-or-flight reactions. Whereas freezing is a form of behavioural inhibition accompanied by parasympathetically dominated heart rate deceleration, fight-or-flight reactions are associated with sympathetically driven heart rate acceleration. Despite the potential relevance of freezing for human stress-coping, its phenomenology and neurobiological underpinnings remain largely unexplored in humans. Studies in rodents have shown that freezing depends on amygdala projections to the brainstem (periaqueductal grey). Recent neuroimaging studies in humans have indicated that similar brain regions may be involved in human freezing. In addition, flexibly shifting between freezing and active defensive modes is critical for adequate stress-coping and relies on fronto-amygdala connections. This review paper presents a model detailing these neural mechanisms involved in freezing and the shift to fight-or-flight action. Freezing is not a passive state but rather a parasympathetic brake on the motor system, relevant to perception and action preparation. Study of these defensive responses in humans may advance insights into human stress-related psychopathologies characterized by rigidity in behavioural stress reactions. The paper therefore concludes with a research agenda to stimulate translational animal-human research in this emerging field of human defensive stress responses.This article is part of the themed issue 'Movement suppression: brain mechanisms for stopping and stillness'. © 2017 The Authors.

  20. Annealing to optimize the primary drying rate, reduce freezing-induced drying rate heterogeneity, and determine T(g)' in pharmaceutical lyophilization.

    Science.gov (United States)

    Searles, J A; Carpenter, J F; Randolph, T W

    2001-07-01

    In a companion paper we show that the freezing of samples in vials by shelf-ramp freezing results in significant primary drying rate heterogeneity because of a dependence of the ice crystal size on the nucleation temperature during freezing.1 The purpose of this study was to test the hypothesis that post-freezing annealing, in which the product is held at a predetermined temperature for a specified duration, can reduce freezing-induced heterogeneity in sublimation rates. In addition, we test the impact of annealing on primary drying rates. Finally, we use the kinetics of relaxations during annealing to provide a simple measurement of T(g)', the glass transition temperature of the maximally freeze-concentrated amorphous phase, under conditions and time scales most appropriate for industrial lyophilization cycles. Aqueous solutions of hydroxyethyl starch (HES), sucrose, and HES:sucrose were either frozen by placement on a shelf while the temperature was reduced ("shelf-ramp frozen") or by immersion into liquid nitrogen. Samples were then annealed for various durations over a range of temperatures and partially lyophilized to determine the primary drying rate. The morphology of fully dried liquid nitrogen-frozen samples was examined using scanning electron microscopy. Annealing reduced primary drying rate heterogeneity for shelf-ramp frozen samples, and resulted in up to 3.5-fold increases in the primary drying rate. These effects were due to increased ice crystal sizes, simplified amorphous structures, and larger and more numerous holes on the cake surface of annealed samples. Annealed HES samples dissolved slightly faster than their unannealed counterparts. Annealing below T(g)' did not result in increased drying rates. We present a simple new annealing-lyophilization method of T(g)' determination that exploits this phenomenon. It can be carried out with a balance and a freeze-dryer, and has the additional advantage that a large number of candidate formulations can

  1. Iinvestigation by electrocontact method of interaction of water with hot surface in film and transition boiling regimes

    Science.gov (United States)

    Ivochkin, Y. P.; Kubrikov, K. G.; Sinkevich, O. A.; Zeigarnik, Y. A.

    2017-11-01

    Using the conductometric technique, the process of contact of subcooled distilled water with a hot surface was studied. The results of measurements of the parameters of the contact made in the range of the temperature change of the heated surface 170 ± 620 ° C are given. An experimental fact has been revealed, which indicates that a transition from film to bubble boiling is preceded by a short (several millisecond) hydrodynamic process that is characterized by intense interaction of waves at the vapour - liquid interface with the heated surface. With the help of wavelet analysis, the amplitude-frequency characteristics of this process are investigated and a qualitative physical model of its flow

  2. Inelastic transitions of atoms and molecules induced by van der Waals interaction with a surface

    Science.gov (United States)

    Baudon, J.; Hamamda, M.; Boustimi, M.; Bocvarski, V.; Taillandier-Loize, T.; Dutier, G.; Perales, F.; Ducloy, M.

    2012-05-01

    Inelastic processes occuring in thermal-velocity metastable atoms and molecules passing at a mean distance (1-100 nm) are investigated. These processes are caused by the quadrupolar part of the van der Waals interaction: fine-structure transitions in atoms (Ar∗, Kr∗), rovibrational transitions in N2∗(3Σu+), transitions among magnetic sub-levels in the presence of a magnetic field.

  3. Antimicrobial activity of transition metal acid MoO{sub 3} prevents microbial growth on material surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zollfrank, Cordt, E-mail: cordt.zollfrank@ww.uni-erlangen.de [University of Erlangen-Nuremberg, Department of Materials Science and Engineering 3-Glass and Ceramics, Martensstr. 5, D-91058 Erlangen (Germany); Gutbrod, Kai [University of Erlangen-Nuremberg, Department of Materials Science and Engineering 3-Glass and Ceramics, Martensstr. 5, D-91058 Erlangen (Germany); Wechsler, Peter [LEONI Kabel GmbH, Stieberstrasse 5, D-91154 Roth (Germany); Guggenbichler, Josef Peter [Laboratory for the Development of Healthcare Products, Leitweg 23, A-6345 Koessen (Austria)

    2012-01-01

    Serious infectious complications of patients in healthcare settings are often transmitted by materials and devices colonised by microorganisms (nosocomial infections). Current strategies to generate material surfaces with an antimicrobial activity suffer from the consumption of the antimicrobial agent and emerging multidrug-resistant pathogens amongst others. Consequently, materials surfaces exhibiting a permanent antimicrobial activity without the risk of generating resistant microorganisms are desirable. This publication reports on the extraordinary efficient antimicrobial properties of transition metal acids such as molybdic acid (H{sub 2}MoO{sub 4}), which is based on molybdenum trioxide (MoO{sub 3}). The modification of various materials (e.g. polymers, metals) with MoO{sub 3} particles or sol-gel derived coatings showed that the modified materials surfaces were practically free of microorganisms six hours after contamination with infectious agents. The antimicrobial activity is based on the formation of an acidic surface deteriorating cell growth and proliferation. The application of transition metal acids as antimicrobial surface agents is an innovative approach to prevent the dissemination of microorganisms in healthcare units and public environments. Highlights: Black-Right-Pointing-Pointer The presented modifications of materials surfaces with MoO{sub 3} are non-cytotoxic and decrease biofilm growth and bacteria transmission. Black-Right-Pointing-Pointer The material is insensitive towards emerging resistances of bacteria. Black-Right-Pointing-Pointer Strong potential to reduce spreading of infectious agents on inanimate surfaces.

  4. Atom-surface interaction at the nanometre scale: van der Waals-Zeeman transitions in a magnetic field

    Science.gov (United States)

    Hamamda, M.; Boustimi, M.; Bocvarski, V.; Taillandier-Loize, T.; Dutier, G.; Perales, F.; Baudon, J.; Ducloy, M.

    2012-04-01

    van der Waals-Zeeman transitions between magnetic states of metastable rare-gas atoms Ar*, Kr* and Xe* (3P2) induced by a solid surface in the presence of a magnetic field, are investigated theoretically and experimentally. By use of a Zeeman slower, metastable argon atoms with various velocities ranging from 170 to 560 m/s allow us to investigate the small impact parameter range (3-7 nm) within which these transitions occur, as well as the effect of atom polarisation on the sharing out of the M states.

  5. ARTICLES: Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskiĭ, V. V.

    1984-04-01

    The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO2 laser radiation at a phase transition in VO2. A three-wave interaction on a VO2 surface was achieved using low-power cw and pulsed CO2 lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm2 and in the second case, it was 42% for a threshold reference wave energy density of 0.6-0.8 mJ/cm2.

  6. Density functional theory study of elemental mercury adsorption on boron doped graphene surface decorated by transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Wongnongwa, Yutthana [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210 (Thailand); Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand)

    2016-01-30

    Graphical abstract: Decoration of Pd{sub 4}-A (square planar) on B-doped graphene significantly promotes Hg{sup 0} adsorption, a single site of Pd{sub 4} cluster on BDG could strongly adsorb up to six Hg atoms. - Highlights: • Transition metal atom and cluster binds strongly on B-doped graphene surface. • Decoration of transition metal on B-doped graphene significantly promotes Hg{sup 0} adsorption. • Adsorption strength of Hg{sup 0} atom on metal decorated B-doped graphene: Pd > Pt > Ru > W > Cu. • One site decorated Pd4 cluster adsorbed Hg{sup 0} strongly up to six atoms.

  7. Mannitol/l-Arginine-Based Formulation Systems for Freeze Drying of Protein Pharmaceuticals: Effect of the l-Arginine Counter Ion and Formulation Composition on the Formulation Properties and the Physical State of Mannitol.

    Science.gov (United States)

    Stärtzel, Peter; Gieseler, Henning; Gieseler, Margit; Abdul-Fattah, Ahmad M; Adler, Michael; Mahler, Hanns-Christian; Goldbach, Pierre

    2016-10-01

    Previous studies have shown that protein storage stability in freeze-dried l-arginine-based systems improved in the presence of chloride ions. However, chloride ions reduced the glass transition temperature of the freeze concentrate (Tg') and made freeze drying more challenging. In this study, l-arginine was freeze dried with mannitol to obtain partially crystalline solids that can be freeze dried in a fast process and result in elegant cakes. We characterized the effect of different l-arginine counter ions on physicochemical properties of mannitol compared with mannitol/sucrose systems. Thermal properties of formulations with different compositions were correlated to thermal history during freeze drying and to physicochemical properties (cake appearance, residual moisture, reconstitution time, crystallinity). Partially crystalline solids were obtained even at the highest l-arginine level (mannitol:l-arginine of 2:1) used in this study. All l-arginine-containing formulations yielded elegant cakes. Only cakes containing l-arginine chloride and succinate showed a surface "crust" formed by phase separation. X-ray powder diffraction showed that inhibition of mannitol crystallization was stronger for l-arginine compared with sucrose and varied with the type of l-arginine counter ion. The counter ion affected mannitol polymorphism and higher levels of mannitol hemi-hydrate were obtained at high levels of l-arginine chloride. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  8. Freeze-Thaw Durability of Air-Entrained Concrete

    Directory of Open Access Journals (Sweden)

    Huai-Shuai Shang

    2013-01-01

    Full Text Available 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.

  9. Quality of hot air dried and freeze-dried of garlic (Allium sativum L.)

    National Research Council Canada - National Science Library

    Fante, Luciane; Noreña, Caciano Pelayo Zapata

    2015-01-01

    ... min, was studied, as also the colour changes, inulin, glucose and fructose contents, particle size and glass transition temperatures of garlic powders obtained by air drying and by freeze-drying...

  10. Freeze Protection in Gas Holders

    DEFF Research Database (Denmark)

    Hjorth, Poul G.; Duursma, Gail

    In cold weather, the water seals of gasholders need protection from freez- ing to avoid compromising the seal. These holders have a large reservoir of “tank water” at the base which is below ground. At present freeze- protection is achieved by external heating of the seal water which is in a slot...

  11. Medical and social egg freezing

    DEFF Research Database (Denmark)

    Lallemant, Camille; Vassard, Ditte; Andersen, Anders Nyboe

    2016-01-01

    with intention to freeze eggs were being single, age under 35 years, childlessness, and a history of infertility. In this group, risk and cost were less important considerations. CONCLUSIONS: This study indicates that there is widespread awareness and support of the availability of eggs freezing for reproductive...

  12. The sensitivity of new laboratory-based heterogeneous freezing schemes for dust and biological particles to time and temperature

    Science.gov (United States)

    Niedermeier, D.; Ervens, B.; Hartmann, S.; Wex, H.; Stratmann, F.

    2012-12-01

    Heterogeneous ice nucleation has been recently described by means of the Soccer ball model that takes into account multiple nucleation sites on individual particles [Niedermeier et al., 2011]. In order to study sensitivities of the implied contact angle distributions, a modified version of the Soccer ball model is implemented into a parcel model that describes in detail heterogeneous ice formation and ice /liquid water partitioning [Ervens and Feingold, 2012]. Soccer ball model parameters (number of surface sites, mean and width of the contact angle distribution) are determined from immersion freezing measurements of mineral dust particles and bacteria performed with the Leipzig Aerosol Cloud Interaction Simulator [LACIS, Hartmann et al., 2011]. While biological particles (e.g., bacteria) are much less frequent in the atmosphere, they can induce droplet freezing already at about -5°C as opposed to dust that shows efficient freezing only at lower temperatures (below -15°C). We will identify updraft regimes, temperature and IN concentration ranges where dust or biological particles, respectively, might dominate the number concentration of frozen droplets in mixed phase clouds. Additional model studies will focus on the importance of time versus temperature dependence and explore the usefulness of alternative descriptions of the freezing behavior that can be derived based on the respective laboratory studies using LACIS. These descriptions include the choice of a single contact angle as opposed to contact angle distributions or time-independent expressions. These results reveal that under selected conditions, it might be a satisfactory approximation to assume singular freezing behavior. Our sensitivity studies will help to refine time-independent freezing parameterizations using laboratory data and help bridging the current divergence between deterministic approaches [e.g., Hoose and Möhler, 2012] and physically-based approaches (classical nucleation theory) that

  13. Intrinsic air stability mechanisms of two-dimensional transition metal dichalcogenide surfaces: basal versus edge oxidation

    Science.gov (United States)

    Longo, Roberto C.; Addou, Rafik; KC, Santosh; Noh, Ji-Young; Smyth, Christopher M.; Barrera, Diego; Zhang, Chenxi; Hsu, Julia W. P.; Wallace, Robert M.; Cho, Kyeongjae

    2017-06-01

    Layered transition metal dichalcogenides (TMDs) are being considered as a promising alternative channel material in ultra-thin and low power nanoelectronics, due to the significant tunability of their electronic properties via mechanisms such as mechanical strain, control of the material thickness, application of an external field, impurities, doping, alloying, or altering the substrate nature. Initially, monolayer TMDs as counterparts to graphene captured the attention of the scientific community owing to their semiconductor nature with sizable band gaps. However, certain physical and chemical properties of TMDs, such as their oxygen reactivity and stability in air need to be more completely understood in order to crystallize the promising superior performance of TMD-based electronic devices. Here, a comparative analysis of the stability of various TMDs (MX2: \\text{M}=\\text{Mo} , W; \\text{X}=\\text{S} , Se) in air is performed using density-functional theory (DFT) as well as x-ray photoelectron spectroscopy (XPS). We find that the surface chemistry of the basal plane of sulfides and selenides is relatively stable in air although for completely different reasons, which can be explained by investigating oxygen dissociative adsorption kinetics and thermodynamics. On the contrary, the edge of MX2 nanoribbons shows strong driving forces towards O2 dissociation and chemisorption. Our combined theoretical and experimental investigation reveals that the air stability of TMDs should not be placed in the same footing that other 2D materials, like graphene. Thus, this work highlights the importance of having controlled oxygen environment during crystal exfoliation/growth and defect passivation in order to provide high quality uniform materials for TMD-based device fabrication.

  14. Evolution of karst conduit networks in transition from pressurised flow to free surface flow

    Science.gov (United States)

    Perne, M.; Covington, M. D.; Gabrovšek, F.

    2014-06-01

    We present a novel modelling approach to study the evolution of conduit networks in soluble rocks. Unlike the models presented so far, the model allows a transition from pressurised (pipe) flow to a free surface (open channel) flow in evolving discrete conduit networks. It calculates flow, solute transport and dissolutional enlargement within each time step and steps through time until a stable flow pattern establishes. The flow in each time step is calculated by calling the EPA Storm Water Management Model (EPA SWMM), which efficiently solves the 1-D Saint Venant equations in a network of conduits. We present several cases with low dip and sub-vertical networks to demonstrate mechanisms of flow pathway selection. In low dip models the inputs were randomly distributed to several junctions. The evolution of pathways progresses upstream: initially pathways linking outlets to the closest inputs evolve fastest because the gradient along these pathways is largest. When a pathway efficiently drains the available recharge, the head drop along the pathway attracts flow from the neighbouring upstream junctions and new connecting pathways evolve. The mechanism progresses from the output boundary inwards until all inputs are connected to the stable flow system. In the pressurised phase, each junction is drained by at least one conduit, but only one conduit remains active in the vadose phase. The selection depends on the initial geometry of a junction, initial distribution of diameters, the evolution in a pressurised regime, and on the dip of the conduits, which plays an important role in vadose entrenchment. In high dip networks, the vadose zone propagates downwards and inwards from the rim of the massif. When a network with randomly distributed initial diameters is supplied with concentrated recharge from the adjacent area, the sink point regresses up upstream along junctions connected to the prominent pathways. Large conductive structures provide deep penetration of high

  15. Anhydrobiosis and Freezing-Tolerance

    DEFF Research Database (Denmark)

    McGill, Lorraine; Shannon, Adam; Pisani, Davide

    2015-01-01

    isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24......Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. Panagrolaimus davidi, a bacterial feeding anhydrobiotic nematode...... Panagrolaimus strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other Panagrolaimus isolates can also survive freezing when fully hydrated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth...

  16. Mechanism of bullet-to-streamer transition in water surface incident helium atmospheric pressure plasma jet (APPJ)

    Science.gov (United States)

    Yoon, Sung-Young; Kim, Gon-Ho; Kim, Su-Jeong; Bae, Byeongjun; Kim, Seong Bong; Ryu, Seungmin; Yoo, Suk Jae

    2016-09-01

    The mechanism of bullet to streamer transition of helium-APPJ bullet on the electrolyte surface was investigated. The APPJ was discharged in pin-to-ring DBD reactor system with helium gas by applying the ac-driven voltage at a frequency of 10 kHz. The water evaporation was controlled via saline temperature. The temporal- and 2-dimensional spatially- resolved plasma properties are monitored by optical diagnostics. During the APPJ bullet propagation from reactor to electrolyte surface, the transition of bullet from streamer was recognized from the high speed image, hydrogen beta emission line, and bullet propagation speed. The He metastable species density profiles from the tunable diode laser absorption spectroscopy (TDLAS) showed the metastable lost the energy near electrolyte surface. It is found that the bullet transited to streamer when the water fraction reached to 29%. This can be fascinating result to study the plasma physics liquid surface, non-fixed boundary. Acknowledgements: This work was partly supported by R&D Program of `Plasma Advanced Technology for Agriculture and Food (Plasma Farming)' through the National Fusion Research Institute of Korea (NFRI) funded by the Government fund was carried out as part.

  17. Numerical study of the effects of surface topography and chemistry on the wetting transition using the string method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yanan, E-mail: ynzhang@suda.edu.cn [School of Mathematical Sciences, Soochow University, Suzhou 215006 (China); Ren, Weiqing, E-mail: matrw@nus.edu.sg [Department of Mathematics, National University of Singapore, Singapore 119076 (Singapore); Institute of High Performance Computing, Singapore 138632 (Singapore)

    2014-12-28

    Droplets on a solid surface patterned with microstructures can exhibit the composite Cassie-Baxter (CB) state or the wetted Wenzel state. The stability of the CB state is determined by the energy barrier separating it from the wetted state. In this work, we study the CB to Wenzel transition using the string method [E et al., J. Chem. Phys. 126, 164103 (2007); W. Ren and E. Vanden-Eijnden, J. Chem. Phys. 138, 134105 (2013)]. We compute the transition states and energy barriers for a three-dimensional droplet on patterned surfaces. The liquid-vapor coexistence is modeled using the mean field theory. Numerical results are obtained for surfaces patterned with straight pillars and nails, respectively. It is found that on both type of surfaces, wetting occurs via infiltration of the liquid in a single groove. The reentrant geometry of nails creates large energy barrier for the wetting of the solid surface compared to straight pillars. We also study the effect of surface chemistry, pillar height, and inter-pillar spacing on the energy barrier and compare it with nails.

  18. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors.

    Science.gov (United States)

    Vojvodic, A; Ruberto, C; Lundqvist, B I

    2010-09-22

    This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different types of surface resonances (SRs) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, δ-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH(2), and NH(3). Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption-energy values with the calculated surface electronic structures. The results are rationalized by use of a concerted-coupling model (CCM), which has previously been applied successfully to the description of adsorption on TiC(111) and TiN(111) surfaces (Ruberto et al 2007 Solid State Commun. 141 48). First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOSs). Detailed comparisons between surface and bulk DOSs reveal the existence of transition-metal localized SRs (TMSRs) in the pseudogap and of several C-localized SRs (CSRs) in the upper valence band on all considered TMC(111) surfaces. The spatial extent and the dangling bond nature of these SRs are supported by real-space analyses of the calculated Kohn-Sham wavefunctions. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOSs reveals a presence of both adsorbate-TMSR and adsorbate-CSRs interactions, of varying strengths depending on the surface and the adsorbate. These variations are

  19. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  20. Ionic Strength-Mediated Phase Transitions of Surface-Adsorbed DNA on Single-Walled Carbon Nanotubes.

    Science.gov (United States)

    Salem, Daniel P; Gong, Xun; Liu, Albert Tianxiang; Koman, Volodymyr B; Dong, Juyao; Strano, Michael S

    2017-11-22

    Single-stranded DNA oligonucleotides have unique, and in some cases sequence-specific molecular interactions with the surface of carbon nanotubes that remain the subject of fundamental study. In this work, we observe and analyze a generic, ionic strength-mediated phase transition exhibited by over 25 distinct oligonucleotides adsorbed to single-walled carbon nanotubes (SWCNTs) in colloidal suspension. The phase transition occurs as monovalent salts are used to modify the ionic strength from 500 mM to 1 mM, causing a reversible reduction in the fluorescence quantum yield by as much as 90%. The phase transition is only observable by fluorescence quenching within a window of pH and in the presence of dissolved O2, but occurs independently of this optical quenching. The negatively charged phosphate backbone increases (decreases) the DNA surface coverage on an areal basis at high (low) ionic strength, and is well described by a two-state equilibrium model. The resulting quantitative model is able to describe and link, for the first time, the observed changes in optical properties of DNA-wrapped SWCNTs with ionic strength, pH, adsorbed O2, and ascorbic acid. Cytosine nucleobases are shown to alter the adhesion of the DNA to SWCNTs through direct protonation from solution, decreasing the driving force for this phase transition. We show that the phase transition also changes the observed SWCNT corona phase, modulating the recognition of riboflavin. These results provide insight into the unique molecular interactions between DNA and the SWCNT surface, and have implications for molecular sensing, assembly, and nanoparticle separations.

  1. Inelastic transitions of atoms and molecules induced by van der Waals interaction with a surface

    Energy Technology Data Exchange (ETDEWEB)

    Baudon, J., E-mail: jacques.baudon@univ-paris13.fr [Laboratoire de Physique des Lasers, CNRS-UMR 7538, Universite Paris 13, Villetaneuse (France); Hamamda, M. [Laboratoire de Physique des Lasers, CNRS-UMR 7538, Universite Paris 13, Villetaneuse (France); Boustimi, M. [Umm Al-Qura University, Makkah (Saudi Arabia); Bocvarski, V. [Institute of Physics, University of Belgrade (Serbia); Taillandier-Loize, T.; Dutier, G.; Perales, F.; Ducloy, M. [Laboratoire de Physique des Lasers, CNRS-UMR 7538, Universite Paris 13, Villetaneuse (France)

    2012-05-15

    Inelastic processes occuring in thermal-velocity metastable atoms and molecules passing at a mean distance (1-100 nm) are investigated. These processes are caused by the quadrupolar part of the van der Waals interaction: fine-structure transitions in atoms (Ar{sup Asterisk-Operator }, Kr{sup Asterisk-Operator }), rovibrational transitions in N{sub 2}{sup Asterisk-Operator }({sup 3}{Sigma}{sub u}{sup +}), transitions among magnetic sub-levels in the presence of a magnetic field.

  2. RESEARCH OF MOISTURE MIGRATION DURING PARTIAL FREEZING OF GROUND BEEF

    Directory of Open Access Journals (Sweden)

    V. M. Stefanovskiy

    2016-01-01

    Full Text Available The concept of «ideal product» is proposed for the study of mass transfer during partial freezing of food products by freezing plate. The ideal product is a product, in which number of factors affecting the «real product» (meat are excluded. These factors include chemical composition of meat, quality grade of raw material (NOR, DFD, PSE, cryoscopic temperature that determines the degree of water transformation into ice, the phenomenon of osmosis, rate of freezing, etc. By using the concept of «ideal product» and its implementation in a physical experiment, it is proved that the “piston effect” causing the migration of moisture is due to frozen crust formation during partial freezing of the body. During partial freezing of the product by freezing plate, «ideal» and «real» food environment is transformed from closed system into open one with inflow of moisture to unfrozen part of the body. In the «ideal product», there is an expulsion of unfrozen moisture from freezing front, so the water appears on the body surface. Thus, the displacement of moisture increases by the same law, according to which the thickness (weight of frozen layer increases. During partial freezing of ground meat, moisture does not appear on the surface of the product, but hydrates the unfrozen part of meat. The reason of this phenomenon is the expulsion of water during formation of frozen crust and water-binding capacity of meat.

  3. Thermal and chemical freeze-out in spectator fragmentation

    Science.gov (United States)

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

    2007-12-01

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

  4. Magnetic surface domain imaging of uncapped epitaxial FeRh(001 thin films across the temperature-induced metamagnetic transition

    Directory of Open Access Journals (Sweden)

    Xianzhong Zhou

    2016-01-01

    Full Text Available The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001 thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001 surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  5. Investigating the link between molecular subtypes of glioblastoma, epithelial-mesenchymal transition, and CD133 cell surface protein.

    Directory of Open Access Journals (Sweden)

    Hadi Zarkoob

    Full Text Available In this manuscript, we use genetic data to provide a three-faceted analysis on the links between molecular subclasses of glioblastoma, epithelial-to-mesenchymal transition (EMT and CD133 cell surface protein. The contribution of this paper is three-fold: First, we use a newly identified signature for epithelial-to-mesenchymal transition in human mammary epithelial cells, and demonstrate that genes in this signature have significant overlap with genes differentially expressed in all known GBM subtypes. However, the overlap between genes up regulated in the mesenchymal subtype of GBM and in the EMT signature was more significant than other GBM subtypes. Second, we provide evidence that there is a negative correlation between the genetic signature of EMT and that of CD133 cell surface protein, a putative marker for neural stem cells. Third, we study the correlation between GBM molecular subtypes and the genetic signature of CD133 cell surface protein. We demonstrate that the mesenchymal and neural subtypes of GBM have the strongest correlations with the CD133 genetic signature. While the mesenchymal subtype of GBM displays similarity with the signatures of both EMT and CD133, it also exhibits some differences with each of these signatures that are partly due to the fact that the signatures of EMT and CD133 are inversely related to each other. Taken together these data shed light on the role of the mesenchymal transition and neural stem cells, and their mutual interaction, in molecular subtypes of glioblastoma multiforme.

  6. Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition

    Science.gov (United States)

    Zhou, Xianzhong; Matthes, Frank; Bürgler, Daniel E.; Schneider, Claus M.

    2016-01-01

    The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  7. Process Analytical Technology in Freeze-Drying: Detection of the Secondary Solute + Water Crystallization with Heat Flux Sensors.

    Science.gov (United States)

    Wang, Qiming; Shalaev, Evgenyi

    2017-11-03

    In situ and non-invasive detection of solute crystallization during freeze-drying would facilitate cycle optimization and scale-up from the laboratory to commercial manufacturing scale. The objective of the study is to evaluate heat flux sensor (HFS) as a tool for monitoring solute crystallization and other first-order phase transitions (e.g., onset of freezing). HFS is a thin-film differential thermopile, which acts as a transducer to generate an electrical signal proportional to the total heat applied to its surface. In this study, HFS is used to detect both primary (ice formation) and secondary (also known as eutectic) solute + water crystallization during cooling and heating of solutions in a freeze-dryer. Binary water-solute mixtures with typical excipients concentrations (e.g., 0.9% of NaCl and 5% mannitol) and fill volumes (1 to 3 ml/vial) are studied. Secondary crystallization is detected by the HFS during cooling in all experiments with NaCl solutions, whereas timing of mannitol crystallization depends on the cooling conditions. In particular, mannitol crystallization takes place during cooling, if the cooling rate is lower than the critical value. On the other hand, if the cooling rate exceeds the critical cooling rate, mannitol crystallization during cooling is prevented, and crystallization occurs during subsequent warming or annealing. It is also observed that, while controlled ice nucleation allows initiation of the primary freezing event in different vials simultaneously, there is a noticeable vial-to-vial difference in the timing of secondary crystallization. The HFS could be a valuable process monitoring tool for non-invasive detection of various crystallization events during freeze-drying manufacturing.

  8. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors

    DEFF Research Database (Denmark)

    Vojvodic, Aleksandra; Ruberto, C.; Lundqvist, Bengt

    2010-01-01

    This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different typ...... CCM to this larger class of substrates and adsorbates. Implications for other classes of materials, for catalysis, and for other surface processes are discussed....... of surface resonances (SRs) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, Nb...

  9. Freeze concentration of dairy products

    Energy Technology Data Exchange (ETDEWEB)

    Amarnath, K.R. [Electric Power Research Inst., Palo Alto, CA (United States). Systems and Materials Dept.; Swinkels, W. [Holland Energy Technology BV (Netherlands)

    1992-12-31

    Freeze concentration as a separation process was discussed. It separates mixed liquids by converting one or more of them to a solid. The process is more energy efficient in many applications than either evaporation or distillation, the most common industrial separation methods today. An EPRI report has shown that annual heat energy consumption would decrease an estimated 1.4 quads if industry replaced evaporation and distillation in every feasible case where freezing can be used. The freeze concentration process was employed to replace thermal evaporation in the dairy industry. The goals of the project were to save energy by converting concentration processes to an efficient electrically powered refrigeration system, and to create higher quality dairy products. Tests showed equal or superior quality from freeze concentrates. 2 tabs.

  10. Dynamic Behaviors and Energy Transition Mechanism of Droplets Impacting on Hydrophobic Surfaces

    OpenAIRE

    Qiaogao Huang; Ya Zhang; Guang Pan

    2016-01-01

    The wettability of hydrophobic surfaces and the dynamic behaviors of droplets impacting on hydrophobic surfaces are simulated using a lattice Boltzmann method, and the condition for the rebound phenomenon of droplets impacting on solid surfaces is analyzed. The results show that there is a linear relationship between the intrinsic contact angle and the interaction strength of fluid-wall particles. For hydrophobic surfaces with the same intrinsic contact angle, the micromorphology can increase...

  11. 9 CFR 590.536 - Freezing operations.

    Science.gov (United States)

    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 human...

  12. 7 CFR 58.621 - Freezing tunnels.

    Science.gov (United States)

    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 be...

  13. Spatially resolved surface valence gradient and structural transformation of lithium transition metal oxides in lithium-ion batteries.

    Science.gov (United States)

    Liu, Hanshuo; Bugnet, Matthieu; Tessaro, Matteo Z; Harris, Kristopher J; Dunham, Mark J R; Jiang, Meng; Goward, Gillian R; Botton, Gianluigi A

    2016-10-26

    Layered lithium transition metal oxides are one of the most important types of cathode materials in lithium-ion batteries (LIBs) that possess high capacity and relatively low cost. Nevertheless, these layered cathode materials suffer structural changes during electrochemical cycling that could adversely affect the battery performance. Clear explanations of the cathode degradation process and its initiation, however, are still under debate and not yet fully understood. We herein systematically investigate the chemical evolution and structural transformation of the LiNixMnyCo1-x-yO2 (NMC) cathode material in order to understand the battery performance deterioration driven by the cathode degradation upon cycling. Using high-resolution electron energy loss spectroscopy (HR-EELS) we clarify the role of transition metals in the charge compensation mechanism, particularly the controversial Ni2+ (active) and Co3+ (stable) ions, at different states-of-charge (SOC) under 4.6 V operation voltage. The cathode evolution is studied in detail from the first-charge to long-term cycling using complementary diagnostic tools. With the bulk sensitive 7Li nuclear magnetic resonance (NMR) measurements, we show that the local ordering of transition metal and Li layers (R3[combining macron]m structure) is well retained in the bulk material upon cycling. In complement to the bulk measurements, we locally probe the valence state distribution of cations and the surface structure of NMC particles using EELS and scanning transmission electron microscopy (STEM). The results reveal that the surface evolution of NMC is initiated in the first-charging step with a surface reduction layer formed at the particle surface. The NMC surface undergoes phase transformation from the layered structure to a poor electronic and ionic conducting transition-metal oxide rock-salt phase (R3[combining macron]m → Fm3[combining macron]m), accompanied by irreversible lithium and oxygen loss. In addition to the

  14. Hypersonic Transition Along Curved Surfaces in the Presence of Vortices and Their Control by Using Microtextured Surfaces

    Science.gov (United States)

    2015-05-13

    goniometry to measure the angle directly from video images of sessile drops. Fig. 3.4(a) shows a side view of a water droplet in air on the textured surface...2011). [89] Liwen Zhu, Chiara Neto, and Phil Attard, “ Reliable measurements of interfacial slip by colloid probe atomic force microscopy. iii. shear

  15. First-Principles Study on the Adsorption Properties of Transition-Metal Atoms on CaO(001) Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Byung Deok [University of Seoul, Seoul (Korea, Republic of); Jang, Young-Rok [Incheon National University, Incheon (Korea, Republic of)

    2017-03-15

    By using first-principles electronic-structure calculations based on the density functional theory, we systematically investigated the adsorption properties of transition-metal (TM) adatoms on CaO(001) surfaces. Optimized adsorption structures and energetics of TM adatoms on CaO(001) are reported for various adsorption structures. The results are different from those of TM adatoms on MgO(001). Concomitantly, this suggests different dynamical properties of TM adatoms on CaO(001) surfaces as compared with TM adatoms on MgO(001) surfaces. Also performed was an analysis of the electronic structures of the TM adatoms on CaO(001) by using the energy positions of the adsorbate states with respect to the valence band maximum of CaO. The results are discussed in connection with the charge states of the TM adatoms on doped CaO(001).

  16. Biogeochemicl and surface elevation controls over tidally influenced freshwater forested wetlands as they transition to marsh

    Science.gov (United States)

    William Conner; Ken W. Krauss; Gregory B. Noe; Jamie A. Duberstein; Nicole Cormier; Camille L. Stagg

    2016-01-01

    Many coastal ecosystems along the south Atlantic are transitioning from forested wetlands to marsh due to increasing tidal inundation and saltwater intrusion primarily attributed to global climate change processes. In 2004, we established long-term research sites in Georgia, South Carolina, and Louisiana to understand how climate factors (temperature, precipitation, ...

  17. A theoretical extension of the soil freezing curve paradigm

    Science.gov (United States)

    Amiri, Erfan A.; Craig, James R.; Kurylyk, Barret L.

    2018-01-01

    Numerical models of permafrost evolution in porous media typically rely upon a smooth continuous relation between pore ice saturation and sub-freezing temperature, rather than the abrupt phase change that occurs in pure media. Soil scientists have known for decades that this function, known as the soil freezing curve (SFC), is related to the soil water characteristic curve (SWCC) for unfrozen soils due to the analogous capillary and sorptive effects experienced during both soil freezing and drying. Herein we demonstrate that other factors beyond the SFC-SWCC relationship can influence the potential range over which pore water phase change occurs. In particular, we provide a theoretical extension for the functional form of the SFC based upon the presence of spatial heterogeneity in both soil thermal conductivity and the freezing point depression of water. We infer the functional form of the SFC from many abrupt-interface 1-D numerical simulations of heterogeneous systems with prescribed statistical distributions of water and soil properties. The proposed SFC paradigm extension has the appealing features that it (1) is determinable from measurable soil and water properties, (2) collapses into an abrupt phase transition for homogeneous media, (3) describes a wide range of heterogeneity within a single functional expression, and (4) replicates the observed hysteretic behavior of freeze-thaw cycles in soils.

  18. Dynamic Linkages Between the Transition Zone & Surface Plate Motion in 2D Models of Subduction

    Science.gov (United States)

    Arredondo, K.; Billen, M. I.

    2014-12-01

    Subduction zones exhibit a wide range of behavior, from slab stagnation at 660 km to direct penetration into the lower mantle. Due to uncertainties in the tectonic history of individual subduction zones, such as trench velocities, potential mechanisms for controlling slab behavior in the transition zone are explored using numerical models. Numerical simulations have utilized a range of assumptions to improve computational efficiency, such as ignoring latent heat, ignoring compositional effects or fixing the trench location: the net effect of these assumptions resulting modeled dynamics remains unclear. Additionally the eight major, composition-dependent, phase transitions for pyrolite, harzburgite and eclogite may be an important influence on subducting slab dynamics due to the additional forces that are dependent on depth and compositional layering within the slab (e.g., Ricard et al., 2005). With the goal of developing more complete, self-consistent, and less idealized simulations, we test the importance of various factors on slab behavior: the presence of shear, adiabatic and latent heating, compositional layering, composition-dependent phase transitions and explicit plate speeds versus dynamically evolving plate and trench velocities. Preliminary results indicate that individual components have a relatively minor effect, but produce large changes when combined together. The extent of slab folding and stagnation is overestimated by only modeling the 410 and 660 km phase transitions. Dynamic models with all seven composition-dependent phase transitions are very sensitive to the plate strength and weak zone viscosity, causing large changes in plate speed and slab detachment. Changes to the overriding plate buoyance and strength investigate the origin and influence of trench movement on slab deformation. These feedbacks and parameter-sensitive behavior indicate that the wide range of observed slab behavior may result from subtle differences in plate and plate

  19. Fermi Surface and Order Parameter Driven Vortex Lattice Structure Transitions in Twin-Free YBa2Cu3O7

    DEFF Research Database (Denmark)

    White, J.S.; Hinkov, V.; Heslop, R.W.

    2009-01-01

    fields. It is separated from a low-field hexagonal phase of different orientation and distortion by a first-order transition at 2.0(2) T that is probably driven by Fermi surface effects. We argue that another first-order transition at 6.7(2) T, into a rhombic structure with a distortion of opposite sign......We report on small-angle neutron scattering studies of the intrinsic vortex lattice (VL) structure in detwinned YBa2Cu3O7 at 2 K, and in fields up to 10.8 T. Because of the suppressed pinning to twin-domain boundaries, a new distorted hexagonal VL structure phase is stabilized at intermediate...

  20. L-Band Emission of Soil Freeze-Thaw State in a Tibetan Meadow Ecosystem

    Science.gov (United States)

    Zheng, Donghai; Wang, Xin; van der Velde, Rogier; Su, Zhongbo; Zeng, Yijian; Wen, Jun; Wang, Zuoliang; Schwank, Mike; Ferrazzoli, Paolo

    2017-04-01

    Soil freeze-thaw transition monitoring is essential for quantifying climate change and hydrologic dynamics over cold regions, for instance, the Tibetan Plateau. We investigate the L-band (1.4 GHz) microwave emission characteristics of soil freeze-thaw cycle via analysis of tower-based brightness temperature (TB) measurements using the ELBARA III radiometer in combination with simulations performed by a model of soil emission considering vertical variations of permittivity and soil temperature. Vegetation effects are modelled using the Tor Vergata discrete model. As part of Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) calibration and validation activities, the ELBARA III radiometer is installed on a 4.8 m high tower located in a seasonally frozen Tibetan meadow ecosystem to measure diurnal cycles of L-band TB. The daily measurements include elevation scanning sequences toward the ground and zenith (sky) measurements. The angular range considered for the elevation scans is performed every 30 min between 40°-70° (relative to nadir) in steps of 5°. The sky measurement is performed at 23:55 every day with an observation angle of 155°. Supporting micro-meteorological (e.g. solar radiation, air temperature and humidity) as well as soil moisture and temperature profile measurements are also conducted near the radiometer. Analyses of the measurements reveal that the impact on TB caused by diurnal changes of ground permittivity is generally stronger than the effect of changing ground temperature. Moreover, the simulations performed with the integrated Tor Vergata model and Noah land surface model indicate that the TB signatures of diurnal soil freeze-thaw cycle is most sensitive to the liquid water content of the soil surface layer, and the measurements taken at 5 cm depth are less representative for the L-band emission.

  1. Long-term stability of sterically stabilized liposomes by freezing and freeze-drying: Effects of cryoprotectants on structure.

    Science.gov (United States)

    Stark, Brigitte; Pabst, Georg; Prassl, Ruth

    2010-11-20

    Liposomes are widely investigated for their use as drug delivery systems, where they have to meet strict stability criteria. Hence, it is of common interest to establish appropriate storage conditions to improve the shelf life of liposomes. In general, long-term stability can be achieved by freezing as well as freeze-drying, and different carbohydrates or polyalcohols, such as mannitol or glycerol are considered as cryoprotective agents to inhibit liposomal fusion or degradation during freezing procedures. Here, we determined the impact of different cryoprotectants on physicochemical parameters of sterically stabilized PEGylated liposomes, which become increasingly important for pharmaceutical applications. We investigated particle stability in terms of size, lamellarity and thickness of the lipid bilayer using photon correlation spectroscopy and small angle X-ray scattering. Besides, we evaluated the impact of cryoprotectants on the thermal lipid phase behavior of either frozen/thawn or lyophilised/rehydrated PEGylated liposome formulations by differential scanning calorimetry. Optimal results for the preservation of the average size of the extruded unilamellar liposomes during freezing were achieved using a mixture of glycerol and carbohydrate concentrations of about 1% (w/v), irrespective of the carbohydrate used. We found no significant changes in the bilayer organisation, and the transition behavior of lipids was almost uneffected by freezing. In case of freeze-drying, similar carbohydrate concentrations as used for freezing were sufficient to maintain the size of PEGylated liposomes after reconstitution of the dried lyophilised cakes, but our small angle X-ray scattering data provide strong evidence that the lyophilisation/rehydration process affects lipid membrane reorganisation on a molecular level such that a swelling of the bilayer might occur. These internal structural changes, which are not detected by standard particle size analysis, might well

  2. On the onset of surface condensation: formation and transition mechanisms of condensation mode

    OpenAIRE

    Qiang Sheng; Jie Sun; Qian Wang; Wen Wang; Hua Sheng Wang

    2016-01-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of ...

  3. Sticky water surfaces: helix-coil transitions suppressed in a cell-penetrating peptide at the air-water interface.

    Science.gov (United States)

    Schach, Denise; Globisch, Christoph; Roeters, Steven J; Woutersen, Sander; Fuchs, Adrian; Weiss, Clemens K; Backus, Ellen H G; Landfester, Katharina; Bonn, Mischa; Peter, Christine; Weidner, Tobias

    2014-12-14

    GALA is a 30 amino acid synthetic peptide consisting of a Glu-Ala-Leu-Ala repeat and is known to undergo a reversible structural transition from a disordered to an α-helical structure when changing the pH from basic to acidic values. In its helical state GALA can insert into and disintegrate lipid membranes. This effect has generated much interest in GALA as a candidate for pH triggered, targeted drug delivery. GALA also serves as a well-defined model system to understand cell penetration mechanisms and protein folding triggered by external stimuli. Structural transitions of GALA in solution have been studied extensively. However, cell penetration is an interfacial effect and potential biomedical applications of GALA would involve a variety of surfaces, e.g., nanoparticles, lipid membranes, tubing, and liquid-gas interfaces. Despite the apparent importance of interfaces in the functioning of GALA, the effect of surfaces on the reversible folding of GALA has not yet been studied. Here, we use sum frequency generation vibrational spectroscopy (SFG) to probe the structural response of GALA at the air-water interface and IR spectroscopy to follow GALA folding in bulk solution. We combine the SFG data with molecular dynamics simulations to obtain a molecular-level picture of the interaction of GALA with the air-water interface. Surprisingly, while the fully reversible structural transition was observed in solution, at the water-air interface, a large fraction of the GALA population remained helical at high pH. This "stickiness" of the air-water interface can be explained by the stabilizing interactions of hydrophobic leucine and alanine side chains with the water surface.

  4. Hot Electron Photoemission from Plasmonic Nanostructures: The Role of Surface Photoemission and Transition Absorption

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Zhukovsky, Sergei; Ikhsanov, Renat Sh

    2015-01-01

    for the enhancement of photoemission in the surface scenario. We calculate the ratio of photoemission cross-section for a gold nanosphere embedded in different materials such as silicon, zinc oxide, and titanium dioxide. For the calculations, we include both surface and bulk mechanisms of photoemission, using quantum...

  5. Effect of metallic and hyperbolic metamaterial surfaces on electric and magnetic dipole emission transitions

    DEFF Research Database (Denmark)

    Ni, X.; Naik, G. V.; Kildishev, A. V.

    2011-01-01

    Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular-depende......-dependent emission spectra of europium ions on top of different films. The results show the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces. The results of numerical calculations agree well with experimental data.......Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular...

  6. Discontinuous percolation transitions in epidemic processes, surface depinning in random media, and Hamiltonian random graphs

    Science.gov (United States)

    Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter

    2012-07-01

    Discontinuous percolation transitions and the associated tricritical points are manifest in a wide range of both equilibrium and nonequilibrium cooperative phenomena. To demonstrate this, we present and relate the continuous and first-order behaviors in two different classes of models: The first are generalized epidemic processes that describe in their spatially embedded version—either on or off a regular lattice—compact or fractal cluster growth in random media at zero temperature. A random graph version of these processes is mapped onto a model previously proposed for complex social contagion. We compute detailed phase diagrams and compare our numerical results at the tricritical point in d=3 with field theory predictions of Janssen [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.70.026114 70, 026114 (2004)]. The second class consists of exponential (“Hamiltonian,” i.e., formally equilibrium) random graph models and includes the Strauss and the two-star model, where “chemical potentials” control the densities of links, triangles, or two-stars. When the chemical potentials in either graph model are O(logN), the percolation transition can coincide with a first-order phase transition in the density of links, making the former also discontinuous. Hysteresis loops can then be of mixed order, with second-order behavior for decreasing link fugacity, and a jump (first order) when it increases.

  7. Exergy analysis for a freeze-drying process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongzhong; Zhao, Yanfei; Feng, Xiao [Department of Chemical Engineering, Xi' an Jiaotong University, 28, Xianning West Road, Xi' an, Shaanxi 710049 (China)

    2008-05-15

    A mathematical model for exergy loss analysis of a freeze-drying process was established to evaluate the exergy losses in the individual operations and the distribution of exergy losses in a freeze-dryer. The exergy losses of five operations, namely, freezing, primary drying, secondary drying and vapor condensation as well as vacuum pumping were included in the model. The unique feature of the model is the incorporation of dynamics into the expressions of the exergy loss analyses for freezing, primary drying and secondary drying stages. The distribution of exergy losses at various operating parameters of freeze-drying was investigated using this model. Take freeze dying beef for an example. The effects of various operation conditions on the exergy losses in the three stages were investigated. The results show that the exergy consumption in the primary drying reaches 35.69% of the total exergy input, while exergy consumption in vapor condensing is 31.76% of the total exergy input. In the vacuum pumping 23.29% of the total exergy input is consumed. In contrast the exergy consumption in the freezing and the secondary drying is only 3.56% and 5.71% of the total exergy input, respectively. The exergy analyses based on various operating parameters show that the exergy losses of the drying process can be remarkably reduced by increasing the temperature of the cooling source in the vapor condenser. In this study, when the temperature of the cooling source in the vapor condenser increases from -70 C to -25 C, it leads to the total exergy losses reducing from 1409 kJ/kg(moist basis) to 604 kJ/kg(moist basis). It indicates that increasing the temperature of vapor condensation is an effective way to reduce the total exergy losses of the system, as long as the conditions of drying dynamics are satisfied during drying. Moreover, there is an optimal surface temperature corresponding to the minimum total exergy losses during the primary and secondary drying stages. If the surface

  8. Liquid gallium-lead mixture phase diagram, surface tension near the critical mixing point, and prewetting transition.

    Science.gov (United States)

    Osman, S M; Grosdidier, B; Ali, I; Abdellah, A Ben

    2013-06-01

    Quite recently, we reported a semianalytical equation of state (EOS) for the Ga-Pb alloy [Phys. Rev. B 78, 024205 (2008)], which was based on the first-order perturbation theory of fluid mixtures, within the simplified random phase approximation, in conjunction with the Grosdidier et al. model pair potentials for Ga-Ga and Pb-Pb with a suitable nonadditive pair potential between Ga-Pb unlike pairs. In the present work, we employ the present EOS to calculate the Ga-Pb phase diagram along the immiscibility gap region. The accuracy of the EOS is tested by consulting the empirical binodal curve. A statistical-mechanical-based theory for the surface tension is employed to obtain an analytical expression for the alloy surface tension. We calculated the surface tension along the bimodal curve and at extreme conditions of temperatures and pressures. The surface tension exhibits reasonably well the prewetting transition of Pb atoms at the surface of the Ga-rich liquid alloy and could qualitatively explain the prewetting phenomena occurring in the Ga-rich side of the phase diagram. The predicted prewetting line and wetting temperature qualitatively agree with the empirical measurements.

  9. Establishing Antibacterial Multilayer Films on the Surface of Direct Metal Laser Sintered Titanium Primed with Phase-Transited Lysozyme

    Science.gov (United States)

    Guan, Binbin; Wang, Haorong; Xu, Ruiqing; Zheng, Guoying; Yang, Jie; Liu, Zihao; Cao, Man; Wu, Mingyao; Song, Jinhua; Li, Neng; Li, Ting; Cai, Qing; Yang, Xiaoping; Li, Yanqiu; Zhang, Xu

    2016-11-01

    Direct metal laser sintering is a technology that allows the fabrication of titanium (Ti) implants with a functional gradation of porosity and surface roughness according to three-dimensional (3D) computer data. The surface roughness of direct metal laser sintered titanium (DMLS-Ti) implants may provide abundant binding sites for bacteria. Bacterial colonization and subsequent biofilm formation can cause unsatisfactory cell adhesion and implant-related infections. To prevent such infections, a novel phase-transited lysozyme (PTL) was utilized as an initial functional layer to simply and effectively prime DMLS-Ti surfaces for subsequent coating with antibacterial multilayers. The purpose of the present study was to establish a surface with dual biological functionality. The minocycline-loaded polyelectrolyte multilayers of hyaluronic acid (HA) and chitosan (CS) formed via a layer-by-layer (LbL) self-assembly technique on PTL-functionalized DMLS-Ti were designed to inhibit pathogenic microbial infections while allowing the DMLS-Ti itself and the modified coatings to retain acceptable biocompatibility. The experimental results indicate that the DMLS-Ti and the hydrogel treated surfaces can inhibit early bacterial adhesion while completely preserving osteoblast functions. This design is expected to gain considerable interest in the medical field and to have good potential for applications in multifunctional DMLS-Ti implants.

  10. Determining the Catalytic Activity of Transition Metal-Doped TiO2 Nanoparticles Using Surface Spectroscopic Analysis

    Science.gov (United States)

    Yang, Sena; Lee, Hangil

    2017-11-01

    The modified TiO2 nanoparticles (NPs) to enhance their catalytic activities by doping them with the five transition metals (Cr, Mn, Fe, Co, and Ni) have been investigated using various surface analysis techniques such as scanning electron microscopy (SEM), Raman spectroscopy, scanning transmission X-ray microscopy (STXM), and high-resolution photoemission spectroscopy (HRPES). To compare catalytic activities of these transition metal-doped TiO2 nanoparticles (TM-TiO2) with those of TiO2 NPs, we monitored their performances in the catalytic oxidation of 2-aminothiophenol (2-ATP) by using HRPES and on the oxidation of 2-ATP in aqueous solution by taking electrochemistry (EC) measurements. As a result, we clearly investigate that the increased defect structures induced by the doped transition metal are closely correlated with the enhancement of catalytic activities of TiO2 NPs and confirm that Fe- and Co-doped TiO2 NPs can act as efficient catalysts.

  11. Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

    Science.gov (United States)

    Ngo, Chi-Vinh; Chun, Doo-Man

    2017-07-01

    Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100 °C was applied. The effect of 100-500 μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500 μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.

  12. On ultrahigh-vacuum preparation of monocrystalline transition metal surfaces by heat treatment

    CERN Document Server

    Krakhmalev, V A; Nimatov, S J; Garafutdinova, I A; Boltaev, N N

    2002-01-01

    The composition and substructure changes in monocrystalline singular W, Mo, Nb surfaces under heat treatment have been studied in the range 30-1900 sup d egC and vacuum approx 5 centre dot 10 sup - sup 8 Pa by electronic Auger spectroscopy, optical microscopy, and X-ray methods. Under multiple thermal-cycled treatment the large carbide inclusions have been found to become the places of local surface polygonization with block disordering >=3 sup d eg. In the case of Nb annealing the carbide in the O sub 2 atmosphere has led to solving O sub 2 in sample volume. In what follows, the solute O sub 2 is found to diffuse to on the surface under heating up to maximal temperatures of the above range. Under 30 min annealing of Nb(110) at approx 550 sup d egC, sulphur (S sub 1 sub 5 sub 2) segregation on surface appears that increases with temperature. (author)

  13. Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni.

    Science.gov (United States)

    López-Moreno, S; Romero, A H

    2015-04-21

    Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O2 molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

  14. Laser-Induced Phase Transition in the Surface of SmS Crystals.

    Science.gov (United States)

    Pohl, D W; Badertscher, R; Müller, K A; Wachter, P

    1974-01-01

    Localized annihilation and generation of the metallic surface phase of SmS was obtained with short laser pulses. Small spot sizes and a large difference in reflectivity suggest an application for optical data storage.

  15. Diffusion of adatoms on face-centered cubic transition metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, Leslie [Iowa State Univ., Ames, IA (United States)

    1994-05-10

    Mechanisms and associated energetics for adatom diffusion on the (100) and (110) surfaces of Ni, Cu, Rh, Pd, and Ag are investigated. Self-diffusion was studied on (100) and (I 10) surfaces of Ni, Cu, Pd and Ag using corrected effective medium method (CEM) and approximation to CEM used for molecular dynamics and Monte Carlo studies (MD/MC-CEM). Self-diffusion on Pd(100), Ag(100), Ni(110), Cu(110), Pd(110), and Ag(110) is accomplished by classical diffusion: the adatom hops from its equilibrium adsorption site over an intervening bridge site to an adjacent equilibrium site. Self-diffusion on Ni(100) and Cu(100) proceeds by atomic-exchange diffusion: the adatom on the surface displaces an atom in the first surface layer. Aside from explicit inclusion of the kinetic-exchange-correlation energy, it is critical to include enough movable atoms in the calculation to insure correct energetics. Distortions induced by these diffusion mechanisms, especially atomic exchange, are long ranged in surface plane, owing to small distortions of many atoms being energetically favored over large distortions of few atoms. Energetics and rates of heterogeneous adatom diffusion on the (100) surfaces of Ni, Cu, Rh, Pd, and Ag show that the final state energies differ due to variation of metallic bonding with coordination for different types of metal atoms. The surface energies of the 2 metals can be used to correlate the amount of energy gained or released when the adatom displaces a surface atom. This difference in energetic stability of final configurations determines whether bridge hopping diffusion or atomic displacement is the dominant kinetic process in these heterogeneous systems.

  16. Investigation of spin-reorientation phase transitions at surface and in volume of alpha-Fe sub 2 O sub 3 monocrystals

    CERN Document Server

    Kamzin, A S

    2002-01-01

    The magnetic structure of the surface layer and volume and the processes, observed by the spin-reorientation phase transition (SRPT), are studied in the direct comparison of the properties of the thin surface layer and the volume of the hematite (alpha-Fe sub 2 O sub 3) macroscopic crystals. The method of simultaneous gamma, X-ray and electron Moessbauer spectroscopy was used in the studies. The direct data on the existence of the transition layer on the hematite crystals surface are obtained. It is established, that the Morin-type SRPT in the sample volume occurs by a jump (the first-order phase transition). The SRPT in the surface layer as well as in the crystal volume is accompanied by formation of the intermediate state, wherein the low- and high-temperature phases coexist. The obtained experimental data on the SRPT mechanism in the surface layer agree well with the conclusions of the phenomenological theory

  17. Transition in discharge plasma of Hall thruster type in presence of secondary electron emissive surface

    Science.gov (United States)

    Schweigert, I. V.; Yadrenkin, M. A.; Fomichev, V. P.

    2017-11-01

    Modification of the sheath structure near the emissive plate placed in magnetized DC discharge plasma of Hall thruster type was studied in the experiment and in kinetic simulations. The plate is made from Al2O3 which has enhanced secondary electron emission yield. The energetic electrons emitted by heated cathode provide the volume ionization and the secondary electron emission from the plate. An increase of the electron beam energy leads to an increase of the secondary electron generation, which initiates the transition in sheath structure over the emissive plate.

  18. Plunge freezing for electron cryomicroscopy.

    Science.gov (United States)

    Dobro, Megan J; Melanson, Linda A; Jensen, Grant J; McDowall, Alasdair W

    2010-01-01

    Aqueous biological samples must be "preserved" (stabilized) before they can be placed in the high vacuum of an electron microscope. Among the various approaches that have been developed, plunge freezing maintains the sample in the most native state and is therefore the method of choice when possible. Plunge freezing for standard electron cryomicroscopy applications proceeds by spreading the sample into a thin film across an EM grid and then rapidly submerging it in a cryogen (usually liquid ethane), but success depends critically on the properties of the grid and sample, the production of a uniformly thin film, the temperature and nature of the cryogen, and the plunging conditions. This chapter reviews plunge-freezing principles, techniques, instrumentation, common problems, and safety considerations. Copyright © 2010 Elsevier Inc. All rights reserved.

  19. Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides

    Science.gov (United States)

    Bahramy, M. S.; Clark, O. J.; Yang, B.-J.; Feng, J.; Bawden, L.; Riley, J. M.; Marković, I.; Mazzola, F.; Sunko, V.; Biswas, D.; Cooil, S. P.; Jorge, M.; Wells, J. W.; Leandersson, M.; Balasubramanian, T.; Fujii, J.; Vobornik, I.; Rault, J. E.; Kim, T. K.; Hoesch, M.; Okawa, K.; Asakawa, M.; Sasagawa, T.; Eknapakul, T.; Meevasana, W.; King, P. D. C.

    2018-01-01

    Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.

  20. Freeze Tolerant Radiator for an Advanced EMU

    Science.gov (United States)

    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

  1. Facing Freeze: Social Threat Induces Bodily Freeze in Humans

    NARCIS (Netherlands)

    Roelofs, K.; Hagenaars, M.A.; Stins, J.F.

    2010-01-01

    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

  2. Visualization data on the freezing process of micrometer-scaled aqueous citric acid drops

    Directory of Open Access Journals (Sweden)

    Anatoli Bogdan

    2017-02-01

    Full Text Available The visualization data (8 movies presented in this article are related to the research article entitled “Freezing and glass transitions upon cooling and warming and ice/freeze-concentration-solution morphology of emulsified aqueous citric acid” (A. Bogdan, M.J. Molina, H. Tenhu, 2016 [1]. The movies recorded in-situ with optical cryo-miscroscopy (OC-M demonstrate for the first time freezing processes that occur during the cooling and subsequent warming of emulsified micrometer-scaled aqueous citric acid (CA drops. The movies are made publicly available to enable critical or extended analyzes.

  3. Nanocrystals in compression: unexpected structural phase transition and amorphization due to surface impurities

    Science.gov (United States)

    Liu, Gang; Kong, Lingping; Yan, Jinyuan; Liu, Zhenxian; Zhang, Hengzhong; Lei, Pei; Xu, Tao; Mao, Ho-Kwang; Chen, Bin

    2016-06-01

    We report an unprecedented surface doping-driven anomaly in the compression behaviors of nanocrystals demonstrating that the change of surface chemistry can lead to an interior bulk structure change in nanoparticles. In the synchrotron-based X-ray diffraction experiments, titania nanocrystals with low concentration yttrium dopants at the surface are found to be less compressible than undoped titania nanocrystals. More surprisingly, an unexpected TiO2(ii) phase (α-PbO2 type) is induced and obvious anisotropy is observed in the compression of yttrium-doped TiO2, in sharp contrast to the compression behavior of undoped TiO2. In addition, the undoped brookite nanocrystals remain with the same structure up to 30 GPa, whereas the yttrium-doped brookite amorphizes above 20 GPa. The abnormal structural evolution observed in yttrium-doped TiO2 does not agree with the reported phase stability of nano titania polymorphs, thus suggesting that the physical properties of the interior of nanocrystals can be controlled by the surface, providing an unconventional and new degree of freedom in search for nanocrystals with novel tunable properties that can trigger applications in multiple areas of industry and provoke more related basic science research.We report an unprecedented surface doping-driven anomaly in the compression behaviors of nanocrystals demonstrating that the change of surface chemistry can lead to an interior bulk structure change in nanoparticles. In the synchrotron-based X-ray diffraction experiments, titania nanocrystals with low concentration yttrium dopants at the surface are found to be less compressible than undoped titania nanocrystals. More surprisingly, an unexpected TiO2(ii) phase (α-PbO2 type) is induced and obvious anisotropy is observed in the compression of yttrium-doped TiO2, in sharp contrast to the compression behavior of undoped TiO2. In addition, the undoped brookite nanocrystals remain with the same structure up to 30 GPa, whereas the yttrium

  4. Freeze and Thaw States Detection in High Latitude Inundated Areas Using High Resolution ALOS PALSAR Observations

    Science.gov (United States)

    Azarderakhsh, M.; McDonald, K. C.; Prakash, S.

    2016-12-01

    Inundated surfaces in Northern latitudes experience freeze and thaw (FT) cycles seasonally. These surfaces are among the important sources of positive carbon and methane (CH4) feedback to the atmosphere as well as their crucial role in biogeochemical transitions, hydrology and prediction of boreal-arctic ecosystem. Wetlands, in particular, are the regions that contribute mostly as a CH4 source. In the past, remote sensing observations from satellites have shown a great potential capability in detecting freeze and thaw states of the surfaces especially in remote areas. Active and passive microwave observations are shown to be more sensitive to the change of surface state and are more promissing than other observations because they are less affected by the atmosphere. Active microwave measurements such as the Advanced Land Observing Satellite Phased Array L-Band SAR (ALOS PALSAR) can provide a viable higher resolution estimates of the inundated surfaces and their states than those from passive microwave brightness temperatures with coarser and higher temporal observations. Therefore, the link between active and passive estimates may potentially enhance our understanding with the advantages of higher spatial and temporal predictions. In this study, we utilize PALSAR ScanSAR mode data with more frequent temporal coverage of up to 40 days along with the static map dervied from Fine Beam Data to study the timing of the inundation for wetland classes as well as their FT states using data from year 2007 to 2010 period. A pixel-based and object oriented-based classification methods to derive freeze/thaw maps is applied. The dynamic inundation maps then are developed at 100 m resolution. JERS and PALSAR Fine Beam mode based static wetlands map and Landsat Based land cover data (NLCD) are used to train and assess the classification at high resolution along with other ancillary data sets. The developed thresholds are employed for the FT detection. Comparison of the results

  5. Influence of step morphology on the structural phase transition of the α-Al{sub 2}O{sub 3}(0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Tosaka, Aki, E-mail: a-tosaka@yokohama-cu.ac.jp; Kitamura, Tatsuya; Sugiyama, Takuhiro; Shigeta, Yukichi [Nanosystem Science, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Koyama, Koji [Namiki Precision Jewel Co., Ltd., 3-8-22 Shinden, Adachi-ku, Tokyo 123-8511 (Japan)

    2014-06-02

    The structural phase transition from the 1 × 1 to the √31 × √31 ± R9° structure of two types of α-Al{sub 2}O{sub 3}(0001) surfaces has been investigated using reflection high-energy electron diffraction. One of the α-Al{sub 2}O{sub 3}(0001) surfaces was composed of regularly arranged monolayer steps (M-surface), and the other surface was composed of multiples of bilayer high steps (B-surface). The surface transition from the 1 × 1 to the √31 × √31 ± R9° structure starts at 1200 °C on the M-surface, but the transition occurs at 1600 °C on the B-surface. We discuss the difference in the stability of these surfaces at high temperature from the viewpoint of the stoichiometry near the step edge and conclude that the B-surface is more stable than the M-surface.

  6. Surface Shear Viscosity and Phase Transitions of Monolayers at the Air-Water Interface

    Science.gov (United States)

    Relini, A.; Ciuchi, F.; Rolandi, R.

    1995-08-01

    The canal method has been employed to measure the in-plane steady shear viscosity of monolayers of bolaform lipids extracted from the membrane of the thermophilic microorganism Sulfolobus solfataricus. Monolayers were formed with the polar lipid extract (PLE), which is a mixture of several bolaform lipids, each one endowed with two nonequivalent polar headgroups. Viscosities were obtained from the measured flows by using the equation introduced by Joly; this equation contains a semiempirical parameter A, which takes into account the monolayer-subphase mechanical coupling. Measuring the flows for two different substances (PLE and oleic acid) and channel widths, the monolayer viscosities and the parameter A were determined at the same time. The analysis of the viscosity data according to the free area model shows evidences of the molecular conformational changes matching monolayer phase transitions.

  7. Transitions in the surface energy balance during the life cycle of a ...

    Indian Academy of Sciences (India)

    Computations are all illustrated for a box over central India where the coastal effects were small,data coverage was not sparse and where the semi-arid land mass changes drastically to a lush green area.This region exhibited large changes in the components of surface energy balance.The principal results pertain to what ...

  8. Experimental analysis and modeling of ultrasound assisted freezing of potato spheres.

    Science.gov (United States)

    Kiani, Hossein; Zhang, Zhihang; Sun, Da-Wen

    2015-09-01

    In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol-water solution at 253.15K) of potato spheres (0.02 m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25 kHz, 890 W m(-2)) was irradiated for different duty cycles (DCs=0-100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30-70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. A tissue snap-freezing apparatus without sacrificial cryogens

    Science.gov (United States)

    Vanapalli, Srinivas; Jagga, Sahil; Holland, Harry; ter Brake, Marcel

    2017-12-01

    Molecular technologies in cancer diagnosis require a fresh and frozen tissue, which is obtained by means of snap-freezing. Currently, coolants such as solid carbon dioxide and liquid nitrogen are used to preserve good morphology of the tissue. Using these coolants, snap freezing of tissues for diagnostic and research purposes is often time consuming, laborious, even hazardous and not user friendly. For that reason snap-freezing is not routinely applied at the location of biopsy acquisition. Furthermore, the influence of optimal cooling rate and cold sink temperature on the viability of the cells is not well known. In this paper, a snap-freezing apparatus powered by a small cryocooler is presented that will allow bio-medical research of tissue freezing methods and is safe to use in a hospital. To benchmark this apparatus, cooldown of a standard aluminum cryo-vial in liquid nitrogen is measured and the cooling rate is about -25 K/s between 295 K and 120 K. Sufficient cooling rate is obtained by a forced convective helium gas flow through a gap formed between the cryo-vial and a cold surface and is therefore chosen as the preferred cooling method. A conceptual design of the snap-apparatus with forced flow is discussed in this paper.

  10. Cryoprotection mechanisms of polyethylene glycols on lactate dehydrogenase during freeze-thawing.

    Science.gov (United States)

    Mi, Yanli; Wood, George; Thoma, Laura

    2004-09-07

    The purpose of this study was to explore the cryoprotection mechanisms of high molecular weight polyethylene glycols (PEGs) (eg, PEG 4000 and PEG 8000) on lactate dehydrogenase (LDH). Ultraviolet activity assays, circular dichroism (CD) spectroscopy, gel filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), (14)C-PEG 4000 labeling and binding, and cryostage microscopic study were conducted. Different molecular weights and concentrations of PEGs in LDH formulations were treated by freeze-thawing. Higher molecular weights and concentrations of PEGs in LDH-PEG formulations obtained better activity and secondary structure recoveries of LDH after freeze-thawing. Insoluble aggregation of LDH was not observed in gel filtration studies. SDS-PAGE results suggested surface characteristic modifications of LDH by the larger molecular weight PEGs. The 14C-PEG 4000 labeling and binding study showed extensive nonspecific interactions between the PEG 4000 and LDH molecules in a concentration-dependent manner. The bound LDH-PEG 4000/free PEG 4000 ratio increased when LDH or PEG 4000 concentrations increased. Cryostage microscopic study showed that PEG 8000 delayed the ice crystallization and eutectic transition of LDH formulation. It appeared that multiple mechanisms were at work during PEGs' cryoprotection of LDH. It was unclear whether the delayed eutectic characteristics of PEGs contributed to LDH cryoprotection. The favorable interaction, rather than preferential exclusion, between LDH and PEGs (eg, 4000) cryoprotected LDH.

  11. Impact of surface impurity on phase transitions in amorphous micro silica

    DEFF Research Database (Denmark)

    Haastrup, Sonja; Yu, Donghong; Yue, Yuanzheng

    2016-01-01

    In this work we study three types of spherically shaped micron and submicron sized amorphous micro silica (MS) as common raw material for production of porous calcium silicate products used for insulation, which are selected on basis of chemical composition and production method. Two of them have...... silica content of 96% (from silicon production) and one has that of 92% (from ferro-silicon production). In order to achieve high quality calcium silicate products, which strongly depends on the characteristics of the raw MS, it is crucial to study the chemical and physical properties of the raw MS...... obtained from different sources. We find that the surface impurities of raw MS lower its crystallization temperature determined from differential scanning calorimetry (DSC). The thermodynamic origin of this correlation is discussed. From the surface crystallization behaviour of raw silica, it is inferred...

  12. Transitioning MODIS to VIIRS observations for Land: Surface Reflectance results, Status and Long-term Prospective

    Science.gov (United States)

    Vermote, E.

    2015-12-01

    Surface reflectance is one of the key products from VIIRS and as with MODIS, is used in developing several higher-order land products. The VIIRS Surface Reflectance (SR) IP is based on the heritage MODIS Collection 5 product (Vermote et al. 2002). The quality and character of surface reflectance depends on the accuracy of the VIIRS Cloud Mask (VCM) and aerosol algorithms and of course on the adequate calibration of the sensor. Early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system known as the Interface Data Processing System (IDPS), has been a major focus of work to-date, but is now evolving into the development of a VIIRS suite of Climate Data Records produced by the NASA Land Science Investigator Processing System (SIPS). We will present the calibration performance and the role of the surface reflectance in calibration monitoring, the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions), the performance of the aerosol input used in the atmospheric correction with quantitative results of the performance of the SR product over AERONET sites. Based on those elements and further assessment, we will address the readiness of the SR product for the production of higher-order land products such as Vegetation Indices, Albedo and LAI/FPAR, the its application to agricultural monitoring and in particular the integration of VIIRS data into the global agricultural monitoring (GLAM) system developed at UMd. Finally from the lessons learned, we will articulate a set of critical recommendations to ensure consistency and continuity of the JPSS mission with the MODIS data record.

  13. 23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

    Science.gov (United States)

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false LCV freeze; cargo-carrying unit freeze. 658.23 Section... OPERATIONS TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS-LENGTH, WIDTH AND WEIGHT LIMITATIONS § 658.23 LCV freeze; cargo-carrying unit freeze. (a)(1) Except as otherwise provided in this section and except for tow...

  14. Defining the design space for freeze-dried orodispersible tablets with meloxicam.

    Science.gov (United States)

    Iurian, Sonia; Tomuta, Ioan; Bogdan, Cătălina; Rus, Lucia; Tokes, Timea; Barbu-Tudoran, Lucian; Achim, Marcela; Moldovan, Mirela; Leucuta, Sorin

    2016-12-01

    This work focused on simultaneously investigating formulation variables and freeze-drying parameters when preparing orodispersible tablets with meloxicam (Mel), by a Quality by Design (QbD) approach. Methylcellulose (MC) was selected as a matrix forming agent and mannitol (Man) as cryoprotectant, both at two concentration levels. The freezing regime was also varied between fast and shelf-ramped, to find out how it affects the final products. The tablet formulations were characterized for their disintegration time, wetting properties, mechanical properties, morphology and in vitro dissolution. Response Surface Modeling completed the statistical analysis that assessed the effects of independent variables on the responses. All the responses showed good fitting to the chosen model. The increase in MC content determined a positive effect on disintegration time, wetting time, mechanical strength and a negative effect on Mel dissolution. High levels of Man-determined brittle products with low-absorption capacity and fast Mel dissolution. The freezing rate had an important effect on the structure of tablets: fast freezing determined slightly thicker pore walls with smooth surfaces, while shelf-ramped freezing led to a multiple-layer structure with increased hardness. Still, shelf-ramped freezing yielded higher Mel release, due to physical changes of the active substance during the freeze-drying process. From the generated design space, an optimal formulation was obtained and the results validated the experimental design. The QbD approach was an efficient manner of understanding formulation and process parameters at the freeze-dried orodispersible tablets preparation.

  15. 7 CFR 51.1562 - Freezing.

    Science.gov (United States)

    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 frozen...

  16. Electrochemical Characteristics of Layered Transition Metal Oxide Cathode Materials for Lithium Ion Batteries: Surface, Bulk Behavior, and Thermal Properties.

    Science.gov (United States)

    Tian, Chixia; Lin, Feng; Doeff, Marca M

    2018-01-16

    Layered lithium transition metal oxides, in particular, NMCs (LiNi x Co y Mn z O 2 ) represent a family of prominent lithium ion battery cathode materials with the potential to increase energy densities and lifetime, reduce costs, and improve safety for electric vehicles and grid storage. Our work has focused on various strategies to improve performance and to understand the limitations to these strategies, which include altering compositions, utilizing cation substitutions, and charging to higher than usual potentials in cells. Understanding the effects of these strategies on surface and bulk behavior and correlating structure-performance relationships advance our understanding of NMC materials. This also provides information relevant to the efficacy of various approaches toward ensuring reliable operation of these materials in batteries intended for demanding traction and grid storage applications. In this Account, we start by comparing NMCs to the isostructural LiCoO 2 cathode, which is widely used in consumer batteries. Effects of changing the metal content (Ni, Mn, Co) upon structure and performance of NMCs are briefly discussed. Our early work on the effects of partial substitution of Al, Fe, and Ti for Co on the electrochemical and bulk structural properties is then covered. The original aim of this work was to reduce the Co content (and thus the raw materials cost) and to determine the effect of the substitutions on the electrochemical and bulk structural properties. More recently, we have turned to the application of synchrotron and advanced microscopy techniques to understand both bulk and surface characteristics of the NMCs. Via nanoscale-to-macroscale spectroscopy and atomically resolved imaging techniques, we were able to determine that the surfaces of NMC undergo heterogeneous reconstruction from a layered structure to rock salt under a variety of conditions. Interestingly, formation of rock salt also occurs under abuse conditions. The surface

  17. Polycation Induced Potential Dependent Structural Transitions of Oligonucleotide Monolayers on Au(111)-Surfaces

    DEFF Research Database (Denmark)

    Salvatore, Princia; Karlsen, Kasper Kannegård; Hansen, Allan Glargaard

    2012-01-01

    We have studied self-assembled molecular monolayers (SAMs) of several 3′-C3-SH conjugated single-strand (ss) and double-strand (ds) 20-base oligonucleotides (ONs) immobilized on single-crystal, atomically planar Au(111)-electrode surfaces in the presence of the triply positively charged base...... electrochemical potential control was used. Spd binding was found to increase notably the ds-ON melting temperature. CV displays capacitive features associated with ss- and ds-ON. A robust capacitive peak around −0.35 V versus saturated calomel electrode (SCE), specific to ds-ON and highly sensitive to base pair...

  18. Investigation of the boundary layer during the transition from volume to surface dominated H⁻ production at the BATMAN test facility.

    Science.gov (United States)

    Wimmer, C; Schiesko, L; Fantz, U

    2016-02-01

    BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 18 scale H(-) source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H(-) production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H(-) density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H(-) density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (j(H(-)), j(e)) exists with the Cs emission.

  19. Investigation of the boundary layer during the transition from volume to surface dominated H- production at the BATMAN test facility

    Science.gov (United States)

    Wimmer, C.; Schiesko, L.; Fantz, U.

    2016-02-01

    BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 1/8 scale H- source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H- production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H- density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H- density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (jH-, je) exists with the Cs emission.

  20. Cathepsin D serum and urine concentration in superficial and invasive transitional bladder cancer as determined by surface plasmon resonance imaging.

    Science.gov (United States)

    Gorodkiewicz, Ewa; Guszcz, Tomasz; Roszkowska-Jakimiec, Wieslawa; Kozłowski, Robert

    2014-09-01

    Determination of cathepsin D (Cat D) concentration in serum and urine may be useful in the diagnosis of bladder cancer. The present study included 54 healthy patients and 68 patients with bladder cancer, confirmed by transurethral resection or cystectomy. Cat D concentration was determined using a surface plasmon resonance imaging biosensor. Cat D concentration in the serum of bladder cancer patients was within the range of 1.3-5.59 ng/ml, while for healthy donors it was within the range of 0.28-0.52 ng/ml. In urine, the Cat D concentration of bladder cancer patients was within the range of 1.35-7.14 ng/ml, while for healthy donors it was within the range of 0.32-0.68 ng/ml. Cat D concentration may represent an efficient tumor marker, as its concentration in the serum and urine of transitional cell carcinoma patients is extremely high when compared with healthy subjects.

  1. Surface energy budget of landfast sea ice during the transitions from winter to snowmelt and melt pond onset

    DEFF Research Database (Denmark)

    Else, B.G.T.; Papakyriakou, T.N.; Raddatz, R.

    2014-01-01

    Relatively few sea ice energy balance studies have successfully captured the transition season of warming, snowmelt, and melt pond formation. In this paper, we report a surface energy budget for landfast sea ice that captures this important period. The study was conducted in the Canadian Arctic......, but it delivered enough energy to significantly hasten melt onset had it occurred earlier in the season. Changes in the frequency, duration, and timing of synoptic-scale weather events that deliver clouds and/or strong turbulent heat fluxes may be important in explaining observed changes in sea ice melt onset......) combined with the seasonal increase in incoming shortwave radiation then triggered snowmelt onset. Melt progressed with a rapid reduction in albedo and attendant increases in shortwave energy absorption, resulting in melt pond formation 8 days later. The key role of longwave radiation in initiating melt...

  2. Dynamical freezing, magnetic ordering, and the magnetocaloric effect in nanostructured Fe/Cu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Desautels, R. D.; Lierop, J. van [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Shueh, C.; Lin, K.-W. [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan (China); Freeland, J. W. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2016-04-25

    Dynamical freezing of Fe nanocrystallites in a Cu matrix with magnetic ordering of an FeCu interfacial phase provides a unique window into the magnetocaloric effect. The FeCu alloy altered the Fe nanocrystallite surface atoms, and with a magnetic ordering temperature comparable to the dynamical freezing temperature of the nanocrystallites enabled Fe surface atoms to contribute to the overall magnetization. Tuning the amount of interfacial alloy resulted in the control of the magnetic ordering temperature and the magnetocaloric properties.

  3. The study of transition metal surfaces and thin films with inverse photoemission and scanning tunnelling microscopy

    CERN Document Server

    Wilson, L K

    1997-01-01

    clean Cr(001) and the thick films. This suggests that hybridisation between the substrate bands and the film bands and interface induced states are significant. The spectra taken from sub-monolayer coverages of Fe show marked intensity increase at the Fermi energy, this is a feature of LDOS calculations on Fe atoms at the Fe/Cr interface. Fe growth on surfaces of Cu(100) precovered with c(2x2)N has been studied with scanning tunnelling microscopy. The images show that the Fe does not grow on areas covered with nitrogen. Two different c(2x2)N templates have been used and the shape and size of the Fe islands is seen to be altered. The unoccupied electronic states at the surface of Cr(001) have been observed using k-resolved inverse photoemission. Normal incidence IPE spectra have been taken over a range of incident electron energies (14-24 eV). The spectra show only small variation with incident energy, this is attributed to densities of states effects due to the absence of symmetry allowed initial states at th...

  4. Non-uniqueness of quantum transition state theory and general dividing surfaces in the path integral space.

    Science.gov (United States)

    Jang, Seogjoo; Voth, Gregory A

    2017-05-07

    Despite the fact that quantum mechanical principles do not allow the establishment of an exact quantum analogue of the classical transition state theory (TST), the development of a quantum TST (QTST) with a proper dynamical justification, while recovering the TST in the classical limit, has been a long standing theoretical challenge in chemical physics. One of the most recent efforts of this kind was put forth by Hele and Althorpe (HA) [J. Chem. Phys. 138, 084108 (2013)], which can be specified for any cyclically invariant dividing surface defined in the space of the imaginary time path integral. The present work revisits the issue of the non-uniqueness of QTST and provides a detailed theoretical analysis of HA-QTST for a general class of such path integral dividing surfaces. While we confirm that HA-QTST reproduces the result based on the ring polymer molecular dynamics (RPMD) rate theory for dividing surfaces containing only a quadratic form of low frequency Fourier modes, we find that it produces different results for those containing higher frequency imaginary time paths which accommodate greater quantum fluctuations. This result confirms the assessment made in our previous work [Jang and Voth, J. Chem. Phys. 144, 084110 (2016)] that HA-QTST does not provide a derivation of RPMD-TST in general and points to a new ambiguity of HA-QTST with respect to its justification for general cyclically invariant dividing surfaces defined in the space of imaginary time path integrals. Our analysis also offers new insights into similar path integral based QTST approaches.

  5. Feasibility of Freeze-Dried Sera for Serological and Molecular Biological Detection of Hepatitis B and C Viruses▿

    OpenAIRE

    Ohishi, Waka; FUJIWARA, Saeko; Suzuki, Gen; Kishi, Takeshi; Sora, Misae; Matsuura, Shinsuke; Hakoda, Masayuki; Tatsukawa, Yoshimi; Yamada, Michiko; Chayama, Kazuaki

    2006-01-01

    We compared hepatitis B virus (HBV) surface antigen, anti-hepatitis C virus (HCV) antibody, and HCV RNA quantification in frozen and freeze-dried serum samples to assess the usefulness of freeze-dried sera for detection of HBV and HCV. The results indicated that freeze-dried sera as well as frozen sera can be useful for serological and molecular biological analyses of HBV and HCV.

  6. Freeze Technology for Nuclear Applications - 13590

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

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

  7. Freeze-Thaw Resistance of Normal and High Strength Concretes Produced with Fly Ash and Silica Fume

    Directory of Open Access Journals (Sweden)

    Cenk Karakurt

    2015-01-01

    Full Text Available This study is based on determination of the freeze-thaw resistance of air-entrained and non-air-entrained normal strength concrete (NC and high strength concrete (HSC produced with fly ash and silica fume according to surface scaling. The procedure allows us to measure the amount of scaling per unit surface area due to a number of well defined freezing and thawing cycles in the presence of deicing salt. The weight loss, surface scaling, moisture uptake, and internal damage were measured after 0 and after every 4th freeze-thaw cycle. The test results showed that the freeze-thaw resistance is influenced directly by the compressive strength property of the concrete. Silica fume significantly reduced the resistance of normal strength concrete against freeze-thaw effect without plasticizing agent. The surface scaling of silica fume concrete without admixture was 22% higher than reference normal concrete.

  8. Freezing-induced uptake of trehalose into mammalian cells facilitates cryopreservation.

    Science.gov (United States)

    Zhang, Miao; Oldenhof, Harriëtte; Sieme, Harald; Wolkers, Willem F

    2016-06-01

    The aim of this study was to investigate if membrane-impermeable molecules are taken up by fibroblasts when exposing the cells to membrane phase transitions and/or freezing-induced osmotic forces. The membrane-impermeable fluorescent dye lucifer yellow (LY) was used to visualize and quantify uptake during endocytosis, and after freezing-thawing. In addition, trehalose uptake after freezing and thawing was studied. Fourier transform infrared spectroscopic studies showed that fibroblasts display a minor non-cooperative phase transition during cooling at suprazero temperatures, whereas cells display strong highly cooperative fluid-to-gel membrane phase transitions during freezing, both in the absence and presence of protectants. Cells do not show uptake of LY upon passing the suprazero membrane phase transition at 30-10°C, whereas after freezing and thawing cells show intracellular LY equally distributed within the cell. Both, LY and trehalose are taken up by fibroblasts after freezing and thawing with loading efficiencies approaching 50%. When using 250 mM extracellular trehalose during cryopreservation, intracellular concentrations greater than 100 mM were determined after thawing. A plot of cryosurvival versus the cooling rate showed a narrow inverted-'U'-shaped curve with an optimal cooling rate of 40°C min(-1). Diluting cells cryopreserved with trehalose in isotonic cell culture medium resulted in a loss of cell viability, which was attributed to intracellular trehalose causing an osmotic imbalance. Taken together, mammalian cells can be loaded with membrane-impermeable compounds, including the protective agent trehalose, by subjecting the cells to freezing-induced osmotic stress. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Thermodynamics of freezing and melting

    OpenAIRE

    Pedersen, Ulf Rørbæk; Costigliola, Lorenzo; Bailey, Nicholas; Schrøder, Thomas; Dyre, Jeppe C.

    2016-01-01

    Although the freezing of liquids and melting of crystals are fundamental for many areas of the sciences, even simple properties like the temperature?pressure relation along the melting line cannot be predicted today. Here we present a theory in which properties of the coexisting crystal and liquid phases at a single thermodynamic state point provide the basis for calculating the pressure, density and entropy of fusion as functions of temperature along the melting line, as well as the variatio...

  10. Alkali metal and simple gas atom adsorption and coadsorption on transition metal surfaces

    CERN Document Server

    Norris, A G

    2000-01-01

    system is formed by adsorption of potassium or cesium on the Ni(100)c(2x2)-O overlayer. The difficulty of the structural fit is compounded' by the size of the unit cell. In this study, Anomalous Scattering was used to investigate whether there is a contribution from the nickel substrate to the reconstruction. Measurements of the fractional order rods at 10 eV and 200 eV below the nickel K edge (8333 eV) showed no discernible differences and involvement of the nickel substrate in the reconstruction can be eliminated. Alkali metal coadsorption systems represent a step along the pathway from simple model adsorbate overlayers to more technologically relevant real systems. Such is their complexity, however, that very few systems have been solved structurally. Presented here are SXRD and STM investigations of two such systems. The first study involves potassium adsorption on the Ni(100)(2x2)p4g-N surface, where a clock reconstruction is present with the nickel substrate atoms rotated in alternate clockwise and anti...

  11. Potential-induced structural transitions of DL-homocysteine monolayers on Au(111) electrode surfaces

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Demetriou, Anna; Welinder, Anne Christina

    2005-01-01

    Monolayers of homocysteine on Au(111)-surfaces have been investigated by voltammetry, in situ scanning tunnelling microscopy (STM) and subtractively normalised interfacial Fourier transform spectroscopy (SNIFTIRS). A pair of sharp voltammetric peaks build up in the potential range 0 to -0.1 V (vs....... SCE) in phosphate buffer pH 7.7. The peak half-widths are about 25 mV at a scan rate of 10 mV s(-1). This is much smaller than for a one-electron Faradaic process (90.6 mV) under similar conditions. The coverage of homocysteine is 6.1 (+/- 0.2) x 10(-10) Mol cm(-2), or 5.9 x 10(-5) C cm(-2), from Au...... and lower pH. The midpoint potential shows biphasic behaviour, decreasing linearly with increasing pH until pH 10.4 towards a constant value at higher pH. The cathodic and anodic peak charges decay at pH both higher and lower than 7.7. The homocysteine monolayer was investigated by in situ STM at different...

  12. Strain-induced insulator-metal transition in ferroelectric BaTiO3 (001) surface: First-principles study

    Science.gov (United States)

    Lin, Yang; Chang-An, Wang; Cong, Liu; Ming-Hui, Qin; Xu-Bing, Lu; Xing-Sen, Gao; Min, Zeng; Jun-Ming, Liu

    2016-07-01

    The electronic properties of TiO2-terminated BaTiO3 (001) surface subjected to biaxial strain have been studied using first-principles calculations based on density functional theory. The Ti ions are always inward shifted either at compressive or tension strains, while the inward shift of the Ba ions occurs only for high compressive strain, implying an enhanced electric dipole moment in the case of high compressive strain. In particular, an insulator-metal transition is predicted at a compressive biaxial strain of 0.0475. These changes present a very interesting possibility for engineering the electronic properties of ferroelectric BaTiO3 (001) surface. Project supported by the National Natural Science Foundation of China (Grant Nos. 1574091, 51272078, and 51431006), the Natural Science Foundation of Guangdong Province of China (Grant No. 2015A030313375), the Science and Technology Planning Project of Guangdong Province of China (Grant No. 2015B090927006), and the Program for International Innovation Cooperation Platform of Guangzhou City, China (Grant No. 2014J4500016).

  13. Extracellular ice phase transitions in insects.

    Science.gov (United States)

    Hawes, T C

    2014-01-01

    At temperatures below their temperature of crystallization (Tc), the extracellular body fluids of insects undergo a phase transition from liquid to solid. Insects that survive the transition to equilibrium (complete freezing of the body fluids) are designated as freeze tolerant. Although this phenomenon has been reported and described in many Insecta, current nomenclature and theory does not clearly delineate between the process of transition (freezing) and the final solid phase itself (the frozen state). Thus freeze tolerant insects are currently, by convention, described in terms of the temperature at which the crystallization of their body fluids is initiated, Tc. In fact, the correct descriptor for insects that tolerate freezing is the temperature of equilibrium freezing, Tef. The process of freezing is itself a separate physical event with unique physiological stresses that are associated with ice growth. Correspondingly there are a number of insects whose physiological cryo-limits are very specifically delineated by this transitional envelope. The distinction also has considerable significance for our understanding of insect cryobiology: firstly, because the ability to manage endogenous ice growth is a fundamental segregator of cryotype; and secondly, because our understanding of internal ice management is still largely nascent.

  14. Heat and Mass Transfer of Droplet Vacuum Freezing Process Based on Dynamic Mesh

    Directory of Open Access Journals (Sweden)

    Lili Zhao

    2014-01-01

    Full Text Available A numerical simulation using dynamic mesh method by COMSOL has been developed to model heat and mass transfer during vacuum freezing by evaporation of a single droplet. The initial droplet diameter, initial droplet temperature, and vacuum chamber pressure effect are studied. The surface and center temperature curve was predicted to show the effect. The mass transfer rate and radius displacement were also calculated. The results show the dynamic mesh shows well the freezing process with the radius reduction of droplet. The initial droplet diameter, initial droplet temperature, and vacuum pressure have obvious effect on freezing process. The total freezing time is about 200 s, 300 s, and 400 s for droplet diameter 7.5 mm, 10.5 mm, and 12.5 mm, respectively. The vacuum pressure less than 200 Pa is enough for the less time to freezing the droplet, that is, the key point in freezing time. The initial droplet temperature has obvious effect on freezing but little effect on freezing temperature.

  15. Freezing induces a loss of freeze tolerance in an overwintering insect.

    Science.gov (United States)

    Brown, C L; Bale, J S; Walters, K F A

    2004-07-22

    Cold-hardy insects overwinter by one of two main strategies: freeze tolerance and freeze avoidance by supercooling. As a general model, many freeze-tolerant species overwinter in extreme climates, freeze above -10 degrees C via induction by ice-nucleating agents, and once frozen, can survive at temperatures of up to 40 degrees C or more below the initial freezing temperature or supercooling point (SCP). It has been assumed that the SCP of freeze-tolerant insects is unaffected by the freezing process and that the freeze-tolerant state is therefore retained in winter though successive freeze-thaw cycles of the body tissues and fluids. Studies on the freeze-tolerant larva of the hoverfly Syrphus ribesii reveal this assumption to be untrue. When a sample with a mean 'first freeze' SCP of -7.6 degrees C (range of -5 degrees C to -9.5 degrees C) were cooled, either to -10 degrees C or to their individual SCP, on five occasions, the mean SCP was significantly depressed, with some larvae subsequently freezing as low as -28 degrees C. Only larvae that froze at the same consistently high temperature above -10 degrees C were alive after being frozen five times. The wider occurrence of this phenomenon would require a fundamental reassessment of the dynamics and distinctions of the freeze-tolerant and freeze-avoiding strategies of insect overwintering. Copyright 2004 The Royal Society

  16. Transcriptomic analysis reveals metabolic switches and surface remodeling as key processes for stage transition in Trypanosoma cruzi

    Directory of Open Access Journals (Sweden)

    Luisa Berná

    2017-03-01

    Full Text Available American trypanosomiasis is a chronic and endemic disease which affects millions of people. Trypanosoma cruzi, its causative agent, has a life cycle that involves complex morphological and functional transitions, as well as a variety of environmental conditions. This requires a tight regulation of gene expression, which is achieved mainly by post-transcriptional regulation. In this work we conducted an RNAseq analysis of the three major life cycle stages of T. cruzi: amastigotes, epimastigotes and trypomastigotes. This analysis allowed us to delineate specific transcriptomic profiling for each stage, and also to identify those biological processes of major relevance in each state. Stage specific expression profiling evidenced the plasticity of T. cruzi to adapt quickly to different conditions, with particular focus on membrane remodeling and metabolic shifts along the life cycle. Epimastigotes, which replicate in the gut of insect vectors, showed higher expression of genes related to energy metabolism, mainly Krebs cycle, respiratory chain and oxidative phosphorylation related genes, and anabolism related genes associated to nucleotide and steroid biosynthesis; also, a general down-regulation of surface glycoprotein coding genes was seen at this stage. Trypomastigotes, living extracellularly in the bloodstream of mammals, express a plethora of surface proteins and signaling genes involved in invasion and evasion of immune response. Amastigotes mostly express membrane transporters and genes involved in regulation of cell cycle, and also express a specific subset of surface glycoprotein coding genes. In addition, these results allowed us to improve the annotation of the Dm28c genome, identifying new ORFs and set the stage for construction of networks of co-expression, which can give clues about coded proteins of unknown functions.

  17. Phenotypic plasticity of the ovarian surface epithelium: TGF-beta 1 induction of epithelial to mesenchymal transition (EMT) in vitro.

    Science.gov (United States)

    Zhu, Yihong; Nilsson, Mikael; Sundfeldt, Karin

    2010-11-01

    Ovarian surface epithelium (OSE) is the most conceivable cell origin of epithelial ovarian carcinomas. Unlike many other epithelial tumors, the precancerous lesion acquires expression of epithelial markers, e.g. E-cadherin and claudins, suggesting that OSE cells undergo mesenchymal to epithelial transition (MET) during transformation. Recent findings indicate that TGF-β1, a prototypic stimulus of epithelial to mesenchymal transition (EMT), i.e. reverse to MET, is produced at significant amounts in the intact ovary. In the present study, we therefore investigated whether TGF-β1 changes the OSE phenotype accordingly, focusing on epithelial junction proteins and transcriptional EMT regulators quantified by real-time RT-PCR and Western blotting in cultured normal human OSE. Early OSE passages were found to paradoxically express de novo E-cadherin and also establish tight junctions exhibiting claudin-1 (but not claudin-3 and -4) and occludin. Stimulation with TGF-β1 (100 ng/ml) for 3-5 d down-regulated all these epithelial markers including Crumbs3 and also prevented the formation of an epithelial barrier This was accompanied by sustained expression of Snail and N-cadherin and transient expression of Slug, whereas Zeb1 (zinc finger E-box binding homeobox 1) and Twist mRNA levels were not significantly changed. In conclusion, TGF-β1 enforces the mesenchymal phenotype of OSE cells in vitro by an EMT-like process, leading to an altered molecular composition of the epithelial junction complex that partly coincides with the expression pattern of the native OSE. This suggests a potential role of TGF-β1-induced EMT in OSE under physiological conditions and possibly also in epithelial ovarian tumorigenesis.

  18. Freezing tolerance versus freezing susceptibility in the land snail Helix aspersa (Gastropoda: Helicidae).

    Science.gov (United States)

    Ansart, A; Vernon, P; Daguzan, J

    2001-01-01

    Freezing hardiness in ectotherms has often been separated into two categories, freezing tolerance and freezing susceptibility. But more complex classifications have also been proposed. Helix aspersa hibernates in Brittany during winter. It has a high temperature of crystallisation (between -1.2( and -7.4 degrees C) and survives only few hours at freezing temperatures. Helix aspersa is a large snail, which needs a long time to freeze and can bear some ice formation in its tissues up to 60% of its total body water. It may be provisionally considered as a partially freezing tolerant species.

  19. Unconventional Surface Critical Behavior Induced by a Quantum Phase Transition from the Two-Dimensional Affleck-Kennedy-Lieb-Tasaki Phase to a Néel-Ordered Phase.

    Science.gov (United States)

    Zhang, Long; Wang, Fa

    2017-02-24

    A symmetry-protected topological phase has nontrivial surface states in the presence of certain symmetries, which can either be gapless or be degenerate. In this work, we study the physical consequence of such gapless surface states at the bulk quantum phase transition (QPT) that spontaneously breaks these symmetries. The two-dimensional Affleck-Kennedy-Lieb-Tasaki phase on a square lattice and its QPTs to Néel ordered phases are realized with the spin-1/2 Heisenberg model on a decorated square lattice. With large-scale quantum Monte Carlo simulations, we show that even though the bulk QPTs are governed by the conventional Landau phase transition theory, the gapless surface states induce unconventional universality classes of the surface critical behavior.

  20. Effect of baking and steaming on physicochemical and thermal properties of sweet potato puree preserved by freezing and freeze-drying

    Directory of Open Access Journals (Sweden)

    Bernarda Svrakačić

    2016-01-01

    Full Text Available Thermal treatments could be one of the hurdles in applications of sweet potato purees for food different products formulation. Sweet potato purees (SPP were prepared from raw, baked and steamed roots and they were preserved by freezing and freeze-drying. The effects of baking and steaming on thermal properties (melting temperature-Tm, melting transition energy - ΔH, and glass transition temperatures - Tg of sweet potato (cultivar Beauregard, were measured by means of a Differential scanning calorimetry (DSC. The SPP made from baked roots had higher total and soluble solids (20.32 and 18.95%, respectively than SPP made from raw and steamed roots. It can be also noticed that starch content was reduced by steaming and baking which reflected on amount of total and reducing sugars. The increase of reducing sugars level in baked SPP for 3.78% and steamed for 0.86% SPP was the result of yielding the maltose. The chemical changes of SPP also influenced the thermal behavior such that SPP prepared from baked sweet potato roots had the lowest initial freezing point (-2.80 °C followed by SPP prepared from steamed (-2.63 °C and raw (-0.71 °C roots. The highest energy for melting (transition was needed for SPP prepared from raw potato roots followed by steamed and baked roots, -103.79, -103.63, and -102.90 J/g, respectively. The glass transition in freeze-dried SPP prepared from raw roots was not detected. However, in the freeze-dried SPP prepared from baked and steamed roots the glass transition was detected in the range of 39 and 42 °C but with no significant difference (p > 0.05.

  1. Characteristics of sugar surfactants in stabilizing proteins during freeze-thawing and freeze-drying.

    Science.gov (United States)

    Imamura, Koreyoshi; Murai, Katsuyuki; Korehisa, Tamayo; Shimizu, Noriyuki; Yamahira, Ryo; Matsuura, Tsutashi; Tada, Hiroko; Imanaka, Hiroyuki; Ishida, Naoyuki; Nakanishi, Kazuhiro

    2014-06-01

    Sugar surfactants with different alkyl chain lengths and sugar head groups were compared for their protein-stabilizing effect during freeze-thawing and freeze-drying. Six enzymes, different in terms of tolerance against inactivation because of freeze-thawing and freeze-drying, were used as model proteins. The enzyme activities that remained after freeze-thawing and freeze-drying in the presence of a sugar surfactant were measured for different types and concentrations of sugar surfactants. Sugar surfactants stabilized all of the tested enzymes both during freeze-thawing and freeze-drying, and a one or two order higher amount of added sugar surfactant was required for achieving protein stabilization during freeze-drying than for the cryoprotection. The comprehensive comparison showed that the C10-C12 esters of sucrose or trehalose were the most effective through the freeze-drying process: the remaining enzyme activities after freeze-thawing and freeze-drying increased at the sugar ester concentrations of 1-10 and 10-100 μM, respectively, and increased to a greater extent than for the other surfactants at higher concentrations. Results also indicate that, when a decent amount of sugar was also added, the protein-stabilizing effect of a small amount of sugar ester through the freeze-drying process could be enhanced. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  2. Boundary-Layer-Transition Measurements on Hemispheres of Various Surface Roughness in a Wind Tunnel at Mach Numbers from 2.48 to 3.55

    Science.gov (United States)

    Bandettini, Angelo; Isler, Walter E.

    1959-01-01

    Wind-tunnel tests have been made to determine the location of the boundary-layer transition on three hemispheres having surface roughness (absolute) values of 50, 580, and 2760 microinches. After the initial test run of the smoothest (50 microinch) hemisphere, holes ranging in depth from 1500 to 2500 microinches were noticed in the meridian where transition was observed. The holes were believed to be caused by particles in the air stream. Shadowgraph pictures were obtained of all hemispheres and surface temperature measurements were made on one hemisphere (580 microinches). Tests at high Reynolds numbers (6.4 to 7.5 x 10(exp 6) and a Mach number of 2.48 did not indicate any transition on the 50-microinch surface hemisphere before the holes appeared. However, after the holes were noticed, transition locations as low as 50 deg(measured from the stagnation point) were observed at similar Reynolds numbers and Mach numbers. It is felt the transition resulted from the holes. Similar transition locations of approximately 500 were also observed in the tests of hemispheres with surface roughness values of 580 and 2760 microinches at high Reynolds numbers (6.4 x 10(exp 6) to 7.5 x 10(exp 6)) and at a Mach number of 2.48. The results at a Mach number of 2.48 indicate that an absolute surface roughness value of 50 microinches was not critical in causing boundary-layer tran sition at Reynolds numbers of 6.4 to 7.5 x 10(exp 6) whereas roughness values of 580 and 2760 microinches were greater than critical. Transition Reynolds numbers based on momentum thickness, R(sub phi T) varied over a range of approximately 480 to 300 for transition locations, alpha, on the hemisphere from 880 to 410 (measured from the stagnation point). A maximum value of R(phi) of 660 (based on alpha = 90 deg) was obtained with the 50-microinch surface hemisphere at a Mach number of 2.48.

  3. Contact Freezing of Water by Salts.

    Science.gov (United States)

    Niehaus, Joseph; Cantrell, Will

    2015-09-03

    Water is unlikely to crystallize homogeneously at temperatures greater than -34 °C. Freezing at higher temperatures is heterogeneous-catalyzed by the presence of a second substance. If that substance is at an air-water interface, then the mode is called contact freezing, and it typically will trigger nucleation at a higher temperature than if the substance were wholly immersed within the liquid. We find that the impact of salt particles initiates freezing in experiments using water droplets at supercoolings of 9 to 16 °C. These results show that contact freezing nuclei need not be effective as immersion mode nuclei. We discuss our results in the context of proposed mechanisms of contact freezing. Finally, we use the time scales for diffusion of heat and of ions and the propagation of a sound wave through the droplet to estimate that contact freezing occurs within 10 ns of impact.

  4. [Cryobiology and pathologic lesions induced by freezing-thawing processes in prostatic tissue. Second part].

    Science.gov (United States)

    Escudero Barrilero, Angel; Arias Fúnez, Fernando; Patrón Rodríguez, Rafael Rodríguez; García González, Ricardo; Cuesta Roca, Carmen

    2004-12-01

    Cryosurgery is an emerging technology consisting on controlled freezing of tissues. Good results, maintained in the long-term, have been referred in the treatment of prostate adenocarcinoma. A role as possible substitute of partial nephrectomy in the treatment of renal adenocarcinomas smaller than 4-5 cm is under research. There is no discussion that freezing destroys cellular machinery and triggers several events the final result of which is cell death by necrosis and apoptosis. The decrease of temperature makes extracellular liquid crystallize and creates a hyperosmotic environment, which induces water to go out of the cell producing intracellular dehydration. Intracellular ice is created with fast freezing speeds being attributed the most destructive effect on biological tissues with irreparable damage. In blood vessels, it directly induces endothelial cell death and mechanical lesions of the endothelium; the consequence is the formation of thrombi that obstruct the lumen of the vessel. In the post-thawing phase there is an increase in free radicals formation and neutrophil activity, which induces cellular membrane lipids peroxidation and new endothelium lesions. Tissue destruction is determined by: minimal temperature achieved, freezing speeds, freezing phase duration, number of freezing-thawing cycles provided, and distance to the freezing focus. As we move away from the freezing focus cells are affected in different ways, and there are several mechanisms proposed to explain the lethal action induced by temperatures higher than--40 degrees C. In our series pathologic findings were: necrosis, hemorrhagic areas either developed or not, fibrosis, hyalinization and increases in the relative number of hematic capillaries, microscopic calcifications, basal cells hyperplasia, and transitional or squamous metaplasia. Residual cancer is localized in the areas less affected by freezing. It should be emphasize the scarce morbimortality associated with the procedure. It

  5. Search for 2νββ excited state transitions and HPGe characterization for surface events in GERDA phase II

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, Bjoern

    2016-03-01

    } transitions, respectively. These limits are more than two orders of magnitude larger than previous ones and could exclude many old matrix element calculations. In addition to the excited state searches, important measurements and improvements for GERDA Phase II upgrades are performed within this dissertation. 30 new BEGe detectors are characterized for their surface and active volume properties which is an essential ingredient for all future physics analyses in GERDA. These precision measurements reduce the systematic uncertainty of the active volume to a subdominant level. In extension to this, a new model for simulating pulse shapes of n{sup +} electrode surface events is developed. With this model it is demonstrated that the dominant background of {sup 42}K on the detector surfaces can be suppressed by a factor of 145 with an A/E pulse shape cut in Phase II. A further suppression of background is obtained by a liquid argon scintillation light veto. With newly developed Monte Carlo simulations, including the optical scintillation photons, it is demonstrated that {sup 208}Tl in the detectors holders can be suppressed by a factor of 134. {sup 42}K homogeneously distributed in the LAr can be suppressed with this veto in combination with pulse shape cuts by a factor of 170 for BEGe detectors. The characterization measurements and the developed simulation tools presented within this dissertation will help to enhance the sensitivity for all 0/2νββ decay modes and will allow to construct an improved background model in GERDA Phase II.

  6. Butterfly magnetoresistance, quasi-2D Dirac Fermi surface and topological phase transition in ZrSiS.

    Science.gov (United States)

    Ali, Mazhar N; Schoop, Leslie M; Garg, Chirag; Lippmann, Judith M; Lara, Erik; Lotsch, Bettina; Parkin, Stuart S P

    2016-12-01

    Magnetoresistance (MR), the change of a material's electrical resistance in response to an applied magnetic field, is a technologically important property that has been the topic of intense study for more than a quarter century. We report the observation of an unusual "butterfly"-shaped titanic angular magnetoresistance (AMR) in the nonmagnetic Dirac material, ZrSiS, which we find to be the most conducting sulfide known, with a 2-K resistivity as low as 48(4) nΩ⋅cm. The MR in ZrSiS is large and positive, reaching nearly 1.8 × 105 percent at 9 T and 2 K at a 45° angle between the applied current (I || a) and the applied field (90° is H || c). Approaching 90°, a "dip" is seen in the AMR, which, by analyzing Shubnikov de Haas oscillations at different angles, we find to coincide with a very sharp topological phase transition unlike any seen in other known Dirac/Weyl materials. We find that ZrSiS has a combination of two-dimensional (2D) and 3D Dirac pockets comprising its Fermi surface and that the combination of high-mobility carriers and multiple pockets in ZrSiS allows for large property changes to occur as a function of angle between applied fields. This makes it a promising platform to study the physics stemming from the coexistence of 2D and 3D Dirac electrons as well as opens the door to creating devices focused on switching between different parts of the Fermi surface and different topological states.

  7. Freeze injury to southern pine seedlings

    Science.gov (United States)

    David B. South

    2006-01-01

    Freeze injury to roots and shoots of pines is affected by genotype and nursery practices. Local sources of shortleaf pine and Virginia pine that are grown in nurseries in USDA hardiness Zones 6 and 7a are relatively freeze tolerant. However, loblolly pine, slash pine, and longleaf pine seedlings have been injured by a number of freeze events (0 to 24 °F) in hardiness...

  8. 31P Nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. II. Lipopolysaccharide and lipopolysaccharide-phospholipid complexes

    NARCIS (Netherlands)

    Alphen, Loek van; Verkleij, A.; Burnell, E.; Lugtenberg, B.

    1980-01-01

    1. 1. Freeze-fracture electron microscopy and 31P-NMR spectroscopy on native and electrodialyzed lipopolysaccharide from Escherichia coli K12 cells, both above and below the phase transition temperature, are described. 2. 2. Freeze-fracture electron microscopy of native lipopolysaccharide shows

  9. Induction of DREB2A pathway with repression of E2F, Jasmonic acid biosynthetic and photosynthesis pathways in cold acclimation specific freeze resistant wheat crown

    Science.gov (United States)

    Winter wheat lines can achieve cold acclimation (development of tolerance to freezing temperatures) and vernalization (delay in transition from vegetative to reproductive phase) in response to low non-freezing temperatures. To describe cold acclimation specific processes and pathways, we utilized co...

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

    Science.gov (United States)

    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...

  11. Thermodynamics of freezing and melting

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Costigliola, Lorenzo; Bailey, Nicholas

    2016-01-01

    Although the freezing of liquids and melting of crystals are fundamental for many areas of the sciences, even simple properties like the temperature–pressure relation along the melting line cannot be predicted today. Here we present a theory in which properties of the coexisting crystal and liquid...... phases at a single thermodynamic state point provide the basis for calculating the pressure, density and entropy of fusion as functions of temperature along the melting line, as well as the variation along this line of the reduced crystalline vibrational mean-square displacement (the Lindemann ratio...

  12. Freeze concentration of lime juice

    OpenAIRE

    Ampawan Tansakul

    2008-01-01

    The main objective of this research was to study the effects of processing conditions, i.e. cooling medium temperature (-6, -12 and -18C) and scraper blade rotational speed (50, 100 and 150 rpm) on the freeze concentration of lime juice. The initial soluble solid content of lime juice was 7.6 Brix. Results showed that soluble solid content of lime juice increased as cooling medium temperature decreased while scraper blade rotational speed increased. It was also found that the processing con...

  13. Electric Double Layer Composed of an Antagonistic Salt in an Aqueous Mixture: Local Charge Separation and Surface Phase Transition

    Science.gov (United States)

    Yabunaka, Shunsuke; Onuki, Akira

    2017-09-01

    We examine an electric double layer containing an antagonistic salt in an aqueous mixture, where the cations are small and hydrophilic but the anions are large and hydrophobic. In this situation, a strong coupling arises between the charge density and the solvent composition. As a result, the anions are trapped in an oil-rich adsorption layer on a hydrophobic wall. We then vary the surface charge density σ on the wall. For σ >0 the anions remain accumulated, but for σ cations are attracted to the wall with increasing |σ |. Furthermore, the electric potential drop Ψ (σ ) is nonmonotonic when the solvent interaction parameter χ (T ) exceeds a critical value χc determined by the composition and the ion density in the bulk. This leads to a first-order phase transition between two kinds of electric double layers with different σ and common Ψ . In equilibrium such two-layer regions can coexist. The steric effect due to finite ion sizes is crucial in these phenomena.

  14. Probing the electronic structure of early transition metal oxide clusters: Molecular models towards mechanistic insights into oxide surfaces and catalysis

    Science.gov (United States)

    Zhai, Hua-Jin; Wang, Lai-Sheng

    2010-11-01

    Selected recent works from the authors' laboratory on the intrinsic electronic and structural properties of early transition metal oxide clusters are reviewed. These clusters provide well-defined molecular models pertinent to mechanistic understandings of complex oxide surface chemistry and catalysis. The energy gap evolution with cluster size was probed for the stoichiometric (TiO 2) n-, (V 2O 5) n-, and (CrO 3) n- clusters, and each system was shown to approach the band gap of bulk oxides in a unique way. A variety of other model clusters have been characterized, such as the oxygen radical or diradical on a single W 6+ site in WO 4-/WO 4, the superoxide (WO 3) n(O 2-) complexes for dioxygen activation, and terminal versus bridging oxygen in M 3O 2- (M = Nb, Ta) clusters. Novel chemical bonding has been observed in a number of oxide clusters. The W 3O 9- and W 3O 92- clusters were found to possess d-orbital aromaticity, whereas δ-aromaticity was discovered in the Ta 3O 3- cluster.

  15. Freezing and thawing of processed meat in an industrial freezing tunnel

    OpenAIRE

    Glaucio Antonio Marini; Eduarda Molardi Bainy; Marcelo Kaminski Lenzi; Marcos Lúcio Corazza

    2014-01-01

    Freezing is a commonly used preservation method in the meat industry. The understanding of the product behavior during the freezing process can assist in a better process management and quality control. This work reports the study of freezing and thawing of three types of processed meat in order to determine process parameters in an industrial forced‑air freezing tunnel at ‑30oC. Chicken sausages (frankfurter type), mortadela (bologna type) and mechanically deboned chicken meat (MDCM) were st...

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

    Science.gov (United States)

    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.

  17. Shock freezing berries. Effective freezing with liquid nitrogen; Beeren unter Frostschock. Tiefgefrieren mit Fluessigstickstoff

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2011-07-01

    Sensitive foods such as fruit do not freeze well at regular sub-zero temperatures. Quick freezing at extremely low temperatures is the only way of ensuring that high-value foodstuffs retain their shape and taste. Linde supplies cryogenic gases for deep freezing and also a broad portfolio of dedicated freezers. (orig.)

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

    NARCIS (Netherlands)

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

    2006-01-01

    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

  19. Boundary-Layer Transition on Hollow Cylinders in Supersonic Free Flight as Affected by Mach Number and a Screwthread Type of Surface Roughness

    Science.gov (United States)

    James, Carlton S.

    1959-01-01

    The effects of Mach number and surface-roughness variation on boundary-layer transition were studied using fin-stabilized hollow-tube models in free flight. The tests were conducted over the Mach number range from 2.8 to 7 at a nominally constant unit Reynolds number of 3 million per inch, and with heat transfer to the model surface. A screwthread type of distributed two-dimensional roughness was used. Nominal thread heights varied from 100 microinches to 2100 microinches. Transition Reynolds number was found to increase with increasing Mach number at a rate depending simultaneously on Mach number and roughness height. The laminar boundary layer was found to tolerate increasing amounts of roughness as Mach number increased. For a given Mach number an optimum roughness height was found which gave a maximum laminar run greater than was obtained with a smooth surface.

  20. [Social freezing - the male perspective].

    Science.gov (United States)

    Gromoll, J; Tüttelmann, F; Kliesch, S

    2016-01-01

    In Germany there is an emerging trend for postponing parenthood due to non-medical, sociocultural reasons. This clearly impacts on the reproductive success due to an age-dependent decrease in fertility. Thus, strategies and techniques are currently discussed which could preserve the female fertility status, among which social freezing (cryopreservation of oocytes) for later fertilization is the most realistic one; however, while there is an intensive discussion on the procedure and timing of oocyte cryopreservation, virtually no attention has been paid to the male side and the aging effects on the male germ cells. To evaluate the risk paternal age poses for the integrity of germ cells. For this review a literature search using PubMed, data from the Federal Statistical Office of Germany, the German in vitro fertilization (IVF) register as well as own data were used. Sperm cell integrity is clearly affected by age both at the genetic as well as at the epigenetic levels. The estimated mutation rate for spermatozoa doubles every 16.5 years. Monogenic and multifactorial diseases are strongly associated with paternal age. Men aged >40 years have an increased risk of passing age-related mutations to their children. Cryopreservation of spermatozoa is an option for men who postpone planning a family. Genetic counseling is recommended for couples undertaking social freezing and a male age of >40 years.

  1. A study of slag freezing in metallurgical furnaces

    Science.gov (United States)

    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

  2. Fall Freeze-up of Sea Ice in the Beaufort-Chukchi Seas Using ERS-1 SAR and Buoy Data

    Science.gov (United States)

    Holt, B.; Winebrenner, B.; D., Nelson E.

    1993-01-01

    The lowering of air temperatures below freezing in the fall indicates the end of summer melt and the onset of steady sea ice growth. The thickness and condition of ice that remains at the end of summer has ramifications for the thickness that that ice will attain at the end of the following winter. This period also designates a shifting of key fluxes from upper ocean freshening from ice melt to increased salinity from brine extraction during ice growth. This transitional period has been examined in the Beaufort and Chukchi Seas using ERS-1 SAR imagery and air temperatures from drifting buoys during 1991 and 1992. The SAR imagery is used to examine the condition and types of ice present in this period. Much of the surface melt water has drained off at this time. Air temperatures from drifting buoys coincident in time and within 100 km radius of the SAR imagery have been obtained...

  3. Monitoring of Freezing Dynamics in Trees: A Simple Phase Shift Causes Complexity.

    Science.gov (United States)

    Charrier, Guillaume; Nolf, Markus; Leitinger, Georg; Charra-Vaskou, Katline; Losso, Adriano; Tappeiner, Ulrike; Améglio, Thierry; Mayr, Stefan

    2017-04-01

    During winter, trees have to cope with harsh conditions, including extreme freeze-thaw stress. This study focused on ice nucleation and propagation, related water shifts and xylem cavitation, as well as cell damage and was based on in situ monitoring of xylem (thermocouples) and surface temperatures (infrared imaging), ultrasonic emissions, and dendrometer analysis. Field experiments during late winter on Picea abies growing at the alpine timberline revealed three distinct freezing patterns: (1) from the top of the tree toward the base, (2) from thin branches toward the main stem's top and base, and (3) from the base toward the top. Infrared imaging showed freezing within branches from their base toward distal parts. Such complex freezing causes dynamic and heterogenous patterns in water potential and probably in cavitation. This study highlights the interaction between environmental conditions upon freezing and thawing and demonstrates the enormous complexity of freezing processes in trees. Diameter shrinkage, which indicated water fluxes within the stem, and acoustic emission analysis, which indicated cavitation events near the ice front upon freezing, were both related to minimum temperature and, upon thawing, related to vapor pressure deficit and soil temperature. These complex patterns, emphasizing the common mechanisms between frost and drought stress, shed new light on winter tree physiology. © 2017 American Society of Plant Biologists. All Rights Reserved.

  4. Estimation of the freezing point of concentrated fruit juices for application in freeze concentration

    OpenAIRE

    Auleda Amorós, Josep Maria; Raventós Santamaria, Mercè; Sánchez Machado, José; Hernández Yáñez, Eduard

    2011-01-01

    In freeze concentration operations the fluids remain at temperatures below 0 °C. For a good study of this concentration operation is very important to know the values of freezing point. The aim of this work was to establish a model that predicts the freezing point of fruit juices at various concentrations within the range of interest for freeze concentration (10–40 °Brix). The model proposed relates the freezing point of a juice with the concentrations of main sugars present in the juice: suc...

  5. Applicable technical method for lower temperature freeze ...

    African Journals Online (AJOL)

    Cryo-fixation and freeze substitution followed by microscopy are commonly used sample preparation methods for visualizing the morphology of intracellular organelles. Freeze substitution is an especially important preparative step because it enables the preservation of intracellular structures in cryo-fixed cells close to the ...

  6. Freeze tolerance and avoidance in plants

    Science.gov (United States)

    Cold acclimation is a multigenic, quantitative trait that involves biochemical and structural changes that effect the physiology of a plant. Mechanisms associated with freeze tolerance or freeze avoidance develop and are lost on an annual cycle. When conducting studies to characterize and determin...

  7. Quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Sachdev, S. [Yale University, New Haven, CT (United States)

    1999-04-01

    Phase transitions are normally associated with changes of temperature but a new type of transition - caused by quantum fluctuations near absolute zero - is possible, and can tell us more about the properties of a wide range of systems in condensed-matter physics. Nature abounds with phase transitions. The boiling and freezing of water are everyday examples of phase transitions, as are more exotic processes such as superconductivity and superfluidity. The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today. Phase transitions are traditionally classified as first or second order. In first-order transitions the two phases co-exist at the transition temperature - e.g. ice and water at 0 deg., or water and steam at 100 deg. In second-order transitions the two phases do not co-exist. In the last decade, attention has focused on phase transitions that are qualitatively different from the examples noted above: these are quantum phase transitions and they occur only at the absolute zero of temperature. The transition takes place atthe ''quantum critical'' value of some other parameter such as pressure, composition or magnetic field strength. A quantum phase transition takes place when co-operative ordering of the system disappears, but this loss of order is driven solely by the quantum fluctuations demanded by Heisenberg's uncertainty principle. The physical properties of these quantum fluctuations are quite distinct from those of the thermal fluctuations responsible for traditional, finite-temperature phase transitions. In particular, the quantum system is described by a complex-valued wavefunction, and the dynamics of its phase near the quantum critical point requires novel theories that have no analogue in the traditional framework of phase transitions. In this article the author describes the history of quantum phase

  8. Effects of high pressure freezing (HPF) on denaturation of natural actomyosin extracted from prawn (Metapenaeus ensis).

    Science.gov (United States)

    Cheng, Lina; Sun, Da-Wen; Zhu, Zhiwei; Zhang, Zhihang

    2017-08-15

    Effects of protein denaturation caused by high pressure freezing, involving Pressure-Factors (pressure, time) and Freezing-Factors (temperature, phase transition, recrystallization, ice crystal types), are complicated. In the current study, the conformation and functional changes of natural actomyosin (NAM) under pressure assisted freezing (PAF, 100,150,300,400,500MPa P -20°C/25min ), pressure shift freezing (PSF, 200MPa P -20°C/25min ), and immersion freezing ( 0.1MPa P -20°C/5min ) after pressure was released to 0.1MPa, as compared to normal immersion freezing process (IF, 0.1MPa P -20°C/30min ). Results indicated that PSF ( 200MPa P -20°C/30min ) could reduce the denaturation of frozen NAM and a pressure of 300MPa was the critical point to induce such a denaturation. During the periods of B→D in PSF or B→C→D in PAF, the generation and growth of ice crystals played an important role on changing the secondary and tertiary structure of the treated NAM. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Techniques for Surface-Temperature Measurements and Transition Detection on Projectiles at Hypersonic Velocities--Status Report No. 2

    Science.gov (United States)

    Bogdanoff, D. W.; Wilder, M. C.

    2006-01-01

    The latest developments in a research effort to advance techniques for measuring surface temperatures and heat fluxes and determining transition locations on projectiles in hypersonic free flight in a ballistic range are described. Spherical and hemispherical titanium projectiles were launched at muzzle velocities of 4.6-5.8 km/sec into air and nitrogen at pressures of 95-380 Torr. Hemisphere models with diameters of 2.22 cm had maximum pitch and yaw angles of 5.5-8 degrees and 4.7-7 degrees, depending on whether they were launched using an evacuated launch tube or not. Hemisphere models with diameters of 2.86 cm had maximum pitch and yaw angles of 2.0-2.5 degrees. Three intensified-charge-coupled-device (ICCD) cameras with wavelength sensitivity ranges of 480-870 nm (as well as one infrared camera with a wavelength sensitivity range of 3 to 5 microns), were used to obtain images of the projectiles in flight. Helium plumes were used to remove the radiating gas cap around the projectiles at the locations where ICCD camera images were taken. ICCD and infrared (IR) camera images of titanium hemisphere projectiles at velocities of 4.0-4.4 km/sec are presented as well as preliminary temperature data for these projectiles. Comparisons were made of normalized temperature data for shots at approx.190 Torr in air and nitrogen and with and without the launch tube evacuated. Shots into nitrogen had temperatures 6% lower than those into air. Evacuation of the launch tube was also found to lower the projectile temperatures by approx.6%.

  10. Fuel Pellets from Wheat Straw: The Effect of Lignin Glass Transition and Surface Waxes on Pelletizing Properties

    DEFF Research Database (Denmark)

    Stelte, Wolfgang; Clemons, Craig; Holm, Jens K.

    2012-01-01

    are investigated by comparing wheat straw before and after organic solvent extraction. The lignin glass transition temperature for wheat straw and extracted wheat straw is determined by dynamic mechanical thermal analysis. At a moisture content of 8%, transitions are identified at 53°C and 63°C, respectively...

  11. Characteristics of High-Impact Long-Duration Freezing Rain Events over North America

    Science.gov (United States)

    McCray, Christopher; Gyakum, John; Atallah, Eyad

    2017-04-01

    While even short periods of freezing rain can be hazardous, the most severe economic and public health impacts tend to occur when it persists for many hours. Predicting the precise and often fragile temperature stratification necessary for freezing rain to persist remains an important forecast challenge. To better elucidate the conditions responsible for the most severe impacts, we concentrate on surface observations of long-duration (6 or more hours) freezing rain events over North America from 1979-2015. Furthermore, we analyze cases in which multiple stations observe long-duration events simultaneously. Following these cases over successive days allows us to generate maps of freezing rain "tracks" which are then categorized by their geographic distributions. We then analyze the conditions that lead to the occurrence of freezing rain for each of these categories. The climatology of long-duration freezing rain events is largely controlled by a combination of synoptic patterns and local terrain effects, which help to maintain or replenish cold air at the surface. As with freezing rain in general, long-duration events occur most frequently from southeastern Canada into the northeastern United States, with a maximum in the St. Lawrence River Valley of Quebec. An examination of the longest-duration events at each station shows a broader geographic distribution, with local maxima in the frequency of 18+ h events over Oklahoma and surrounding states in the South Central United States (SCUS) - a region with relatively low annual freezing rain frequencies. Classification of individual events shows us that in many instances, the SCUS and northeastern North America are impacted by long-duration freezing rain during the same cases. Indeed, the category responsible for the greatest number of freezing rain observations over the largest area is one which begins in the SCUS (often Texas or Oklahoma), with freezing rain occurring over a broad southwest-northeast swath (2-3000 km

  12. Interdependence of measures in pavlovian conditioned freezing.

    Science.gov (United States)

    Wood, Suzanne C; Anagnostaras, Stephan G

    2011-11-14

    Pavlovian conditioned freezing is an intensively utilized paradigm that has become a standard model of memory and cognition. Despite its widespread use, the interdependence among each measure commonly reported in fear conditioning studies has not been described. Using mice, we examine the relationship of each common freezing measure (Training Baseline, Post-Shock freezing, Contextual Fear, Tone Baseline, and Tone Fear), as well as baseline locomotor activity measures, to better understand the significance of each. Of particular interest, Post-Shock freezing appears to be a good measure of immediate contextual memory. In contrast, Tone Baseline freezing, as typically measured in a novel context, appears to be contaminated with multiple sources of fear. Finally, Contextual and Tone Fear show a weak interdependence. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  13. Interdependence of Measures in Pavlovian Conditoned Freezing

    Science.gov (United States)

    Wood, Suzanne C.; Anagnostaras, Stephan G.

    2011-01-01

    Pavlovian conditioned freezing is an intensively utilized paradigm that has become a standard model of memory and cognition. Despite its widespread use, the interdependence among each measure commonly reported in fear conditioning studies has not been described. Using mice, we examine the relationship of each common freezing measure (Training Baseline, Post-Shock freezing, Contextual Fear, Tone Baseline, and Tone Fear), as well as baseline locomotor activity measures, to better understand the significance of each. Of particular interest, Post-Shock freezing appears to be a good measure of immediate contextual memory. In contrast, Tone Baseline freezing, as typically measured in a novel context, appears to be contaminated with multiple sources of fear. Finally, Contextual and Tone Fear show a weak interdependence. PMID:22005576

  14. Monitoring the Freezing Point of Buffalo Milk.

    Science.gov (United States)

    Pesce, Antonella; Salzano, Caterina; De Felice, Anna; Garofalo, Francesca; Liguori, Salvatore; De Santo, Annunziata; Palermo, Pierpaolo; Guarino, Achille

    2016-04-19

    The aim of this study was to evaluate the basic freezing point of buffalo milk. Bulk milk samples were collected from buffalo and cattle farms in Caserta area from 2008 to 2014. The analysis involved a total of 1886 buffalo milk samples and 1711 bovine milk samples. These were also tested for fat, protein and lactose contents by means of infrared spectrometry. The freezing point was determined by means of a thermistor cryoscope. Data underwent statistical analysis. Our research showed an average freezing point of -0.528°C for buffalo milk and -0.522°C for bovine milk. Given the lack of data on the freezing point of buffalo milk, our study provides the first indication of a basic freezing point of the milk of this species in Italy.

  15. Impregnation of leather during "freeze-drying"

    DEFF Research Database (Denmark)

    Storch, Mikkel; Vestergaard Poulsen Sommer, Dorte; Hovmand, Ida

    2016-01-01

    Freeze-drying is a recognized method for the preservation of waterlogged objects. Naturally, freeze-drying has also been used for waterlogged archaeological leather often after treatment with Na2.EDTA and impregnation with PEG; but the treated leather sometimes suffers from “excessive drying......” becoming too stiff and brittle. The aim of this study was to examine the effect of a conventional freeze-drying method against an alternative freeze-drying method that preserves the natural moisture content of the leather. Both new and archaeological waterlogged leather were included in the study...... and the leather samples were treated in one of four ways: pre-treatment with Na2EDTA, impregnation with PEG 400, pre-treatment with Na2EDTA followed by impregnation with PEG 400 as well as no treatment. After the treatments, the leather samples were freeze-dried either by the conventional or by the alternative...

  16. Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger with Bypass Setpoint Temperature Control

    Science.gov (United States)

    Ungar, Eugene K.

    2008-01-01

    Spacecraft radiators are sized for their maximum heat load in their warmest thermal environment, but must operate at reduced heat loads and in colder environments. For systems where the radiator environment can be colder than the working fluid freezing temperature, radiator freezing becomes an issue. Radiator freezing has not been a major issue for the Space Shuttle and the International Space Station (ISS) active thermal control systems (ATCSs) because they operate in environments that are warm relative to the freezing point of their external coolants (Freon-21 and ammonia, respectively). For a vehicle that lands at the Lunar South Pole, the design thermal environment is 215K, but the radiator working fluid must also be kept from freezing during the 0 K sink of transit. A radiator bypass flow control design such as those used on the Space Shuttle and ISS requires more than 30% of the design heat load to avoid radiator freezing during transit - even with a very low freezing point working fluid. By changing the traditional ATCS architecture to include a regenerating heat exchanger inboard of the radiator and by using a regenerator bypass flow control valve to maintain system setpoint, the required minimum heat load can be reduced by more than half. This gives the spacecraft much more flexibility in design and operation. The present work describes the regenerator bypass ATCS setpoint control methodology. It includes analytical results comparing the performance of this system to the traditional radiator bypass system. Finally, a summary of the advantages of the regenerator bypass system are presented.

  17. Freeze concentration of lime juice

    Directory of Open Access Journals (Sweden)

    Ampawan Tansakul

    2008-11-01

    Full Text Available The main objective of this research was to study the effects of processing conditions, i.e. cooling medium temperature (-6, -12 and -18C and scraper blade rotational speed (50, 100 and 150 rpm on the freeze concentration of lime juice. The initial soluble solid content of lime juice was 7.6 Brix. Results showed that soluble solid content of lime juice increased as cooling medium temperature decreased while scraper blade rotational speed increased. It was also found that the processing condition with -18˚C cooling medium temperature and 150 rpm rotational speed of the scraper blade was the best among all studied conditions, although the loss of the soluble solids with ice crystals during ice separation was relatively high at 35%.

  18. Assessing winter oilseed rape freeze injury based on Chinese HJ remote sensing data*

    Science.gov (United States)

    She, Bao; Huang, Jing-feng; Guo, Rui-fang; Wang, Hong-bin; Wang, Jing

    2015-01-01

    The winter oilseed rape (Brassica napus L.) accounts for about 90% of the total acreage of oilseed rape in China. However, it suffers the risk of freeze injury during the winter. In this study, we used Chinese HJ-1A/1B CCD sensors, which have a revisit frequency of 2 d as well as 30 m spatial resolution, to monitor the freeze injury of oilseed rape. Mahalanobis distance-derived growing regions in a normal year were taken as the benchmark, and a mask method was applied to obtain the growing regions in the 2010–2011 growing season. The normalized difference vegetation index (NDVI) was chosen as the indicator of the degree of damage. The amount of crop damage was determined from the difference in the NDVI before and after the freeze. There was spatial variability in the amount of crop damage, so we examined three factors that may affect the degree of freeze injury: terrain, soil moisture, and crop growth before the freeze. The results showed that all these factors were significantly correlated with freeze injury degree (P<0.01, two-tailed). The damage was generally more serious in low-lying and drought-prone areas; in addition, oilseed rape planted on south- and west-oriented facing slopes and those with luxuriant growth status tended to be more susceptible to freeze injury. Furthermore, land surface temperature (LST) of the coldest day, soil moisture, pre-freeze growth and altitude were in descending order of importance in determining the degree of damage. The findings proposed in this paper would be helpful in understanding the occurrence and severity distribution of oilseed rape freeze injury under certain natural or vegetation conditions, and thus help in mitigation of this kind of meteorological disaster in southern China. PMID:25644468

  19. Assessing winter oilseed rape freeze injury based on Chinese HJ remote sensing data.

    Science.gov (United States)

    She, Bao; Huang, Jing-feng; Guo, Rui-fang; Wang, Hong-bin; Wang, Jing

    2015-02-01

    The winter oilseed rape (Brassica napus L.) accounts for about 90% of the total acreage of oilseed rape in China. However, it suffers the risk of freeze injury during the winter. In this study, we used Chinese HJ-1A/1B CCD sensors, which have a revisit frequency of 2 d as well as 30 m spatial resolution, to monitor the freeze injury of oilseed rape. Mahalanobis distance-derived growing regions in a normal year were taken as the benchmark, and a mask method was applied to obtain the growing regions in the 2010-2011 growing season. The normalized difference vegetation index (NDVI) was chosen as the indicator of the degree of damage. The amount of crop damage was determined from the difference in the NDVI before and after the freeze. There was spatial variability in the amount of crop damage, so we examined three factors that may affect the degree of freeze injury: terrain, soil moisture, and crop growth before the freeze. The results showed that all these factors were significantly correlated with freeze injury degree (P<0.01, two-tailed). The damage was generally more serious in low-lying and drought-prone areas; in addition, oilseed rape planted on south- and west-oriented facing slopes and those with luxuriant growth status tended to be more susceptible to freeze injury. Furthermore, land surface temperature (LST) of the coldest day, soil moisture, pre-freeze growth and altitude were in descending order of importance in determining the degree of damage. The findings proposed in this paper would be helpful in understanding the occurrence and severity distribution of oilseed rape freeze injury under certain natural or vegetation conditions, and thus help in mitigation of this kind of meteorological disaster in southern China.

  20. Percolation Phase Transition of Surface Air Temperature Networks under Attacks of El Niño/La Niña.

    Science.gov (United States)

    Lu, Zhenghui; Yuan, Naiming; Fu, Zuntao

    2016-05-26

    In this study, sea surface air temperature over the Pacific is constructed as a network, and the influences of sea surface temperature anomaly in the tropical central eastern Pacific (El Niño/La Niña) are regarded as a kind of natural attack on the network. The results show that El Niño/La Niña leads an abrupt percolation phase transition on the climate networks from stable to unstable or metastable phase state, corresponding to the fact that the climate condition changes from normal to abnormal significantly during El Niño/La Niña. By simulating three different forms of attacks on an idealized network, including Most connected Attack (MA), Localized Attack (LA) and Random Attack (RA), we found that both MA and LA lead to stepwise phase transitions, while RA leads to a second-order phase transition. It is found that most attacks due to El Niño/La Niña are close to the combination of MA and LA, and a percolation critical threshold Pc can be estimated to determine whether the percolation phase transition happens. Therefore, the findings in this study may renew our understandings of the influence of El Niño/La Niña on climate, and further help us in better predicting the subsequent events triggered by El Niño/La Niña.

  1. Preparation of chitosan nanocomposites with a macroporous structure by unidirectional freezing and subsequent freeze-drying.

    Science.gov (United States)

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

    2014-11-24

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

  2. The metal-insulator transition in vanadium dioxide: A view at bulk and surface contributions for thin films and the effect of annealing

    Science.gov (United States)

    Yin, W.; West, K. G.; Lu, J. W.; Pei, Y.; Wolf, S. A.; Reinke, P.; Sun, Y.

    2009-06-01

    Vanadium dioxide is investigated as potential oxide barrier in spin switches, and in order to incorporate VO2 layers in complex multilayer devices, it is necessary to understand the relation between bulk and surface/interface properties. Highly oriented VO2 thin films were grown on (0001) sapphire single crystal substrates with reactive bias target ion beam deposition. In the analysis of the VO2 films, bulk-sensitive methods [x-ray diffraction (XRD) and transport measurements] and surface sensitive techniques [photoelectron spectroscopy (PES) and scanning tunneling microscopy and spectroscopy] were employed. The samples were subjected to heating cycles with annealing temperatures of up to 425 and 525K. Prior to annealing the VO2 films exhibit the transition from the monoclinic to the tetragonal phase with the concurrent change in conductivity by more than a factor of 103 and their phase purity is confirmed by XRD. Annealing to 425K and thus cycling across the metal-insulator transition (MIT) temperature has no impact on the bulk properties of the VO2 film but the surface undergoes irreversible electronic changes. The observation of the valence band with PES during the annealing illustrates that the surface adopts a partially metallic character, which is retained after cooling. Annealing to a higher temperature (525K ) triggers a modification of the bulk, which is evidenced by a considerable reduction in the MIT characteristics, and a degradation in crystallite morphology. The local measurement of the conductivity with scanning tunneling spectroscopy shows the transition of the surface from predominantly semiconducting surface prior to annealing to a surface with an overwhelming contribution from metallic sections afterward. The spatial distribution of metallic regions cannot be linked in a unique manner to the crystallite size or location within the crystallites. The onset of oxygen depletion at the surface is held responsible for this behavior. The onset of bulk

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

    Science.gov (United States)

    Grayson, A L; King, D A; Shackelford, S D; Koohmaraie, M; Wheeler, T L

    2014-06-01

    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) were obtained from U.S. Select carcasses classified at the grading stand by the U.S. Meat Animal Research Center visible and near-infrared spectroscopy tenderness system to have predicted slice shear force greater than 16.5 kg at 14 d postmortem. At 2 d postmortem, 2.54 cm thick steaks were cut from each muscle and assigned to 1 of the following treatments: 2 d fresh (2FRESH), 2 d freeze + thaw (2FREEZE), 2 d freeze + thaw + 12 d age (2FREEZE+12AGE), 14 d fresh (14FRESH), 14 d freeze + thaw (14FREEZE), 14 d freeze + thaw + 14 d age (14FREEZE+14AGE), and 28 d fresh (28FRESH). Steaks assigned to a freezing treatment were frozen at -26°C for 30 d before thawing/cooking or thawing with an additional aging period at 2°C. Slice shear force for LL and ST was lower (P FREEZE (27.4 and 24.5 kg) and 14FREEZE (22.4 and 22.4 kg) compared to 2FRESH (33.0 and 29.2 kg) and 14FRESH (25.3 and 25.5 kg), respectively. Slice shear force for LL and ST was lower (P FREEZE+12AGE (17.8 and 20.8 kg) and 14FREEZE+14AGE (14.6 and 19.0 kg) compared to 14FRESH (25.3 and 25.5 kg) and 28FRESH (18.7 and 21.7 kg), respectively. Desmin degradation for LL was not different (P > 0.05) between 2FREEZE (21.0%) and 2FRESH (14.6%) or between 14FREEZE (40.4%) and 14FRESH (38.4%); however, desmin degradation was higher (P FREEZE+12AGE (46.7%) and 14FREEZE+14AGE (71.1%) when compared to 14FRESH (38.4%) and 28FRESH (60.5%), respectively. Cooking loss for LL was higher (P FREEZE+12AGE (15.2%) compared to 14FRESH (14.0%) but was not different (P > 0.05) between 14FREEZE+14AGE (15.0%) and 28FRESH (14.3%). Freezing and thawing or a combination of freezing, thawing, and aging resulted in increased tenderness for LL

  4. Observations of a metal-insulator transition and strong surface states in Bi2-x SbxSe3 thin films.

    Science.gov (United States)

    Zhang, Cheng; Yuan, Xiang; Wang, Kai; Chen, Zhi-Gang; Cao, Baobao; Wang, Weiyi; Liu, Yanwen; Zou, Jin; Xiu, Faxian

    2014-11-05

    High-quality thin films of the topological insulator Bi2-xSbxSe3 are grown by molecular beam epitaxy. A metal-insulator transition along with strong surface states - revealed by Shubnikov-de Haas oscillations - is observed as the Sb concentration is increased. This system represents a widely tunable platform for achieving high surface conduction, suppressing the bulk influence, and manipulating the band structure of topological insulators. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Freezing during tapping tasks in patients with advanced Parkinson’s disease and freezing of gait

    Science.gov (United States)

    Defebvre, Luc; Tard, Céline

    2017-01-01

    Introduction Parkinson’s disease patients with freezing of gait also experience sudden motor blocks (freezing) during other repetitive motor tasks. We assessed the proportion of patients with advanced PD and freezing of gait who also displayed segmental “freezing” in tapping tasks. Methods Fifteen Parkinson’s disease patients with freezing of gait were assessed. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients performed repetitive tapping movements (as described in the MDS-UPDRS task) with the hands or the feet in the presence or absence of a metronome set to 4 Hz. Movements were recorded with a video motion system. The primary endpoint was the occurrence of segmental freezing in these tapping tasks. The secondary endpoints were (i) the relationship between segmental episodic phenomena and FoG severity, and (ii) the reliability of the measurements. Results For the upper limbs, freezing was observed more frequently with a metronome (21% of trials) than without a metronome (5%). For the lower limbs, the incidence of freezing was higher than for the upper limbs, and was again observed more frequently in the presence of an auditory cue (47%) than in its absence (14%). Conclusion Although freezing of the lower limbs was easily assessed during an MDS-UPDRS task with a metronome, it was not correlated with the severity of freezing of gait (as evaluated during a standardized gait trajectory). Only this latter was a reliable measurement in patients with advanced Parkinson’s disease. PMID:28886015

  6. Transmission electron microscopy of thin sections of Drosophila: high-pressure freezing and freeze-substitution.

    Science.gov (United States)

    McDonald, Kent L; Sharp, David J; Rickoll, Wayne

    2012-04-01

    The state of the art in fine-structure preservation for thin sectioning can be achieved by using fast-freezing technology followed by freeze substitution and embedding in resin. Samples prepared by high-pressure freezing are estimated to be "fixed" in 20-50 msec. Fast freezing also freezes every cell component regardless of its chemistry. Once frozen, tissues can be processed in a variety of ways before viewing in the electron microscope; here we describe only freeze substitution. In freeze substitution, cells are dehydrated at very low temperatures and cell water is replaced with organic solvent at -80°C to -90°C. At this temperature, large molecules such as proteins are immobilized, yet smaller molecules such as water (ice) can be dissolved and replaced with organic solvents, e.g., acetone. The ideal way to do freeze substitution is with a dedicated freeze-substitution device such as the Leica AFS2 system. These devices allow programming of the times and temperatures needed. Alternatively, if this equipment is not available, freeze substitution can still be performed using items commonly found around the laboratory, as is described here. This protocol is useful for preparing thin sections of Drosophila when the best possible preservation of ultrastructure and antigenicity is required.

  7. Direct molecular-level characterization of different heterogeneous freezing modes on mica - Part 1

    Science.gov (United States)

    Abdelmonem, Ahmed

    2017-09-01

    The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface-water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real-time molecular-level comparison of different freezing modes on the surface of an atmospherically relevant mineral surface (mica) under varying supersaturation conditions using second-harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one- and two-stage freezing). The nonlinear signal at the water-mica interface was found to drop following the formation of a thin film on the surface regardless of (1) the formed phase (liquid or ice) and (2) the freezing path (one or two step), indicating similar molecular structuring. The results also revealed a transient phase of ice at water-mica interfaces during freezing, which has a lifetime of around 1 min. Such information will have a significant impact on climate change, weather modification, and the tracing of water in hydrosphere studies.

  8. Spaceborne microwave remote sensing of seasonal freeze-thaw processes in theterrestrial high l atitudes : relationships with land-atmosphere CO2 exchange

    Science.gov (United States)

    McDonald, Kyle C.; Kimball, John S.; Zhao, Maosheng; Njoku, Eni; Zimmermann, Reiner; Running, Steven W.

    2004-01-01

    Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These relatively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing measurements from the Special Sensor Microwave Imager (SSM/I) to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw timing are derived using daily brightness temperature measurements from the 19 GHz, horizontally polarized channel, separately for overpasses with 6 AM and 6 PM equatorial crossing times. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North America and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to seasonal atmospheric CO2 concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Classification differences between AM and PM overpass data average approximately 5 days for the region, though both appear to be effective surrogates for monitoring annual growing seasons at high latitudes.

  9. Spaceborne microwave remote sensing of seasonal freeze-thaw processes in the terrestrial high latitudes: relationships with land-atmosphere CO2 exchange

    Science.gov (United States)

    McDonald, Kyle C.; Kimball, John S.; Zhao, Maosheng; Njoku, Eni; Zimmermann, Reiner; Running, Steven W.

    2004-12-01

    Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These realtively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing measurements from the Special Sensor Microwave Imager (SSM/I) to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw timing are derived using daily brightness temperature measurements from the 19 GHz, horizontally polarized channel, spearately for overpasses with 6 AM and 6 PM equatorial crossing times. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North Americ and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to seasonal atmospheric CO2 concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Classification differences between AM and PM overpass data average approximately 5 days for the region, through both appear to be effective surrogates for monitoring annual growing seasons at high latitudes.

  10. Chemical freeze-out in heavy ion collisions at large baryon densities

    CERN Document Server

    Floerchinger, Stefan

    2012-01-01

    We argue that the chemical freeze-out in heavy ion collisions at high baryon density is not associated to a phase transition or rapid crossover. We employ the linear nucleon-meson model with parameters fixed by the zero-temperature properties of nuclear matter close to the liquid-gas quantum phase transition. For the parameter region of interest this yields a reliable picture of the thermodynamic and chiral properties at non-zero temperature. The chemical freeze-out observed in low-energy experiments occurs when baryon densities fall below a critical value of about 15 percent of nuclear density. This region in the phase diagram is far away from any phase transition or rapid crossover.

  11. Fluid Line Evacuation and Freezing Experiments for Digital Radiator Concept

    Science.gov (United States)

    Berisford, Daniel F.; Birur, Gajanana C.; Miller, Jennifer R.; Sunada, Eric T.; Ganapathi, Gani B.; Stephan, Ryan; Johnson, Mark

    2011-01-01

    The digital radiator technology is one of three variable heat rejection technologies being investigated for future human-rated NASA missions. The digital radiator concept is based on a mechanically pumped fluid loop with parallel tubes carrying coolant to reject heat from the radiator surface. A series of valves actuate to start and stop fluid flow to di erent combinations of tubes, in order to vary the heat rejection capability of the radiator by a factor of 10 or more. When the flow in a particular leg is stopped, the fluid temperature drops and the fluid can freeze, causing damage or preventing flow from restarting. For this reason, the liquid in a stopped leg must be partially or fully evacuated upon shutdown. One of the challenges facing fluid evacuation from closed tubes arises from the vapor generated during pumping to low pressure, which can cause pump cavitation and incomplete evacuation. Here we present a series of laboratory experiments demonstrating fluid evacuation techniques to overcome these challenges by applying heat and pumping to partial vacuum. Also presented are results from qualitative testing of the freezing characteristics of several different candidate fluids, which demonstrate significant di erences in freezing properties, and give insight to the evacuation process.

  12. Freeze concentration beats the heat

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. Freezing at sea: a Canadian opportunity

    National Research Council Canada - National Science Library

    Bollivar, D.R; Cadegan, E; Demone, E.H; Matthew, P; Nicholson, P.J; Shannon, C.P; Stirling, R.C

    This report was prepared for the Nova Scotia Fish Packers Association in an effort to set out as clearly as possible the issues relating to introduction of freezing at sea technology to the Canadian...

  14. Global Annual Freezing and Thawing Indices

    Data.gov (United States)

    National Aeronautics and Space Administration — The total annual freezing and thawing indices are defined as the cumulative number of degree-days when air temperatures are below and above zero degrees Celsius. The...

  15. Microcanonical transition state theory for activated gas-surface reaction dynamics: application to H2/CU(111) with rotation as a spectator.

    Science.gov (United States)

    Abbott, Heather L; Harrison, Ian

    2007-10-04

    A microcanonical unimolecular rate theory (MURT) model incorporating quantized surface vibrations and Rice-Ramsperger-Kassel-Marcus rate constants is applied to a benchmark system for gas-surface reaction dynamics, the activated dissociative chemisorption and associative desorption of hydrogen on Cu(111). Both molecular translation parallel to the surface and rotation are treated as spectator degrees of freedom. MURT analysis of diverse experiments indicates that one surface oscillator participates in the dissociative transition state and that the threshold energy for H2 dissociation on Cu(111) is E0 = 62 kJ/mol. The spectator approximation for rotation holds well at thermally accessible rotational energies (i.e., for Er less than approximately 40 kJ/mol). Over the temperature range from 300 to 1000 K, the calculated thermal dissociative sticking coefficient is ST = S0 exp(-Ea/kBT) where S0 = 1.57 and Ea = 62.9 kJ/mol. The sigmoid shape of rovibrational eigenstate-resolved dissociative sticking coefficients as a function of normal translational energy is shown to derive from an averaging of the microcanonical sticking coefficient, with threshold energy E0, over the thermal surface oscillator distribution of the gas-surface collision complexes. Given that H2/Cu(111) is one of the most dynamically biased of gas-surface reactive systems, the simple statistical MURT model simulates and broadly rationalizes the H2/Cu(111) reactive behavior with remarkable fidelity.

  16. A comparison of freezing-damage during isochoric and isobaric freezing of the potato

    Directory of Open Access Journals (Sweden)

    Chenang Lyu

    2017-05-01

    Full Text Available Background Freezing is commonly used for food preservation. It is usually done under constant atmospheric pressure (isobaric. While extending the life of the produce, isobaric freezing has detrimental effects. It causes loss of food weight and changes in food quality. Using thermodynamic analysis, we have developed a theoretical model of the process of freezing in a constant volume system (isochoric. The mathematical model suggests that the detrimental effects associated with isobaric freezing may be reduced in an isochoric freezing system. To explore this hypothesis, we performed a preliminary study on the isochoric freezing of a produce with which our group has experience, the potato. Method Experiments were performed in an isochoric freezing device we designed. The device is robust and has no moving parts. For comparison, we used a geometrically identical isobaric freezing device. Following freezing and thawing, the samples were weighed, examined with colorimetry, and examined with microscopy. Results It was found that potatoes frozen to −5 °C in an isochoric system experienced no weight loss and limited enzymatic browning. In contrast the −5 °C isobaric frozen potato experienced substantial weight loss and substantial enzymatic browning. Microscopic analysis shows that the structural integrity of the potato is maintained after freezing in the isochoric system and impaired after freezing in the isobaric system. Discussion Tissue damage during isobaric freezing is caused by the increase in extracellular osmolality and the mechanical damage by ice crystals. Our thermodynamic analysis predicts that during isochoric freezing the intracellular osmolality remains comparable to the extracellular osmolality and that isochoric systems can be designed to eliminate the mechanical damage by ice. The results of this preliminary study seem to confirm the theoretical predictions. Conclusion This is a preliminary exploratory study on isochoric freezing

  17. Flash freezing of Mohs micrographic surgery tissue can minimize freeze artifact and speed slide preparation.

    Science.gov (United States)

    Erickson, Quenby L; Clark, Trishina; Larson, Kassandra; Minsue Chen, T

    2011-04-01

    In Mohs micrographic surgery, excised tissue is traditionally prepared for cryotomy by freezing in the cryostat's refrigerated chamber. Any delay may cause drying artifact and tissue autolysis and affect slide turn around time (TAT). Flash freezing is used in frozen section processing of general pathology specimens to expedite TAT and enhance tissue histology by minimizing ice crystal formation (freeze artifact). This was a pilot quality improvement study to compare flash freezing of Mohs sections with the traditional method of freezing in the cryostat. Mohs layers divided into at least two sections (one set) were enrolled. One half was flash frozen in an isopentane histobath (-56 to -62°C); the other half was frozen in the cryostat (-27 to -30°C). Forty-one sets were enrolled. Average cryostat and histobath freeze times (range) were 144 seconds (90-240 seconds) and 22 seconds (15-40 seconds), respectively. Laboratory technicians felt that it was easier to achieve smooth, wrinkle-free sections in histobath frozen tissue in 90% of tissue sets. Physicians favored histology from flash frozen specimens (range 65-85%) over the traditional method of cryostat freezing. Flash freezing in a histobath produced a more rapidly opacified (frozen) specimen ready for cryotomy, expediting slide TAT. Tissue histology also demonstrated better quality and minimized freeze artifact. © 2011 by the American Society for Dermatologic Surgery, Inc.

  18. Monitoring the Freezing Point of Buffalo Milk

    OpenAIRE

    Pesce, Antonella; Salzano, Caterina; De Felice, Anna; Garofalo, Francesca; Liguori, Salvatore; De Santo, Annunziata; Palermo, Pierpaolo; Guarino, Achille

    2016-01-01

    The aim of this study was to evaluate the basic freezing point of buffalo milk. Bulk milk samples were collected from buffalo and cattle farms in Caserta area from 2008 to 2014. The analysis involved a total of 1886 buffalo milk samples and 1711 bovine milk samples. These were also tested for fat, protein and lactose contents by means of infrared spectrometry. The freezing point was determined by means of a thermistor cryoscope. Data underwent statistical analysis. Our research showed an aver...

  19. Direct molecular-level characterization of different heterogeneous freezing modes on mica – Part 1

    Directory of Open Access Journals (Sweden)

    A. Abdelmonem

    2017-09-01

    Full Text Available The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface–water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real-time molecular-level comparison of different freezing modes on the surface of an atmospherically relevant mineral surface (mica under varying supersaturation conditions using second-harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one- and two-stage freezing. The nonlinear signal at the water–mica interface was found to drop following the formation of a thin film on the surface regardless of (1 the formed phase (liquid or ice and (2 the freezing path (one or two step, indicating similar molecular structuring. The results also revealed a transient phase of ice at water–mica interfaces during freezing, which has a lifetime of around 1 min. Such information will have a significant impact on climate change, weather modification, and the tracing of water in hydrosphere studies.

  20. Flash-and-Freeze: Coordinating Optogenetic Stimulation with Rapid Freezing to Visualize Membrane Dynamics at Synapses with Millisecond Resolution.

    Science.gov (United States)

    Watanabe, Shigeki

    2016-01-01

    Electron microscopy depicts subcellular structures at synapses exquisitely but only captures static images. To visualize membrane dynamics, we have developed a novel technique, called flash-and-freeze, which induces neuronal activity with a flash of light and captures the membrane dynamics by rapid freezing. For characterizing membrane movements during synaptic transmission, a light-sensitive cation channel, channelrhodopsin, is heterologously expressed in mouse hippocampal neurons or in Caenorhabditis elegans motor neurons. A brief pulse of blue light activates channelrhodopsin and induces an action potential, leading to synaptic transmission. Following the light stimulation, neurons are frozen at different time intervals ranging from 10 ms to 20 s. Electron micrographs are then acquired from each time point to visualize the morphological changes. Using this approach, we have characterized a novel form of endocytosis, ultrafast endocytosis, which rapidly removes excess membrane added to the surface during neurotransmission. The flash-and-freeze approach can be adapted to study other cellular phenomena that can be induced by light-sensitive genetic or pharmacological tools.

  1. Effect of Freezing on Lyophilization Process Performance and Drug Product Cake Appearance.

    Science.gov (United States)

    Esfandiary, Reza; Gattu, Shravan K; Stewart, John M; Patel, Sajal M

    2016-04-01

    This study highlights the significance of the freezing step and the critical role it can play in modulating process performance and product quality during freeze-drying. For the model protein formulation evaluated, the mechanism of freezing had a significant impact on cake appearance, a potential critical product quality attribute for a lyophilized drug product. Contrary to common knowledge, a freezing step with annealing resulted in 20% increase in primary drying time compared to without annealing. In addition, annealing resulted in poor cake appearance with shrinkage, cracks, and formation of a distinct skin at the top surface of the cake. Finally, higher product resistance (7.5 cm(2).Torr.hr/g) was observed in the case of annealing compared to when annealing was not included (5 cm(2).Torr.hr/g), which explains the longer primary drying time due to reduced sublimation rates. An alternative freezing option using controlled ice nucleation resulted in reduced primary drying time (i.e., 30% reduction compared to annealing) and a more homogenous batch with elegant uniform (i.e., significantly improved) cake appearance. Here, a mechanistic understanding of the distinct differences in cake appearance as a function of freezing mechanism is proposed within the context of ice nucleation temperature, ice crystal growth, and presumed solute distribution within the frozen matrix. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  2. Analysis of PEMFC freeze degradation at -20{sup o}C after gas purging

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Junbo; Yu, Hongmei; Zhang, Shengsheng; Sun, Shucheng; Wang, Hongwei; Yi, Baolian; Ming, Pingwen [Fuel Cell R and D Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China)

    2006-11-08

    Proton exchange membrane fuel cell (PEMFC) freeze degradation was investigated using 20 freeze/thaw cycles of two cells with gases purged immediately after operation. The cell purged by gas with an RH 58.0% at 25{sup o}C was found to have no performance loss after the 20 freeze/thaw cycles. From the cell resistances and the electrochemical impedance spectra (EIS), the electrolyte conductivity and interfacial charge transfer resistance were unchanged. The electrochemical active surface area (ECSA) from the cyclic voltammetry (CV) measurements indicated that the amount of water in the catalyst layer of the cell was reduced to an extent that the damage in the freeze/thaw cycles was avoided. Another cell was purged by RH 64.9% gas in the first cycle, and then was purged with RH 45.0% gas in 19 freeze/thaw cycles. Although the cell easily became flooded at high current densities after the first cycle, no further performance loss was found. The pore size distribution data from mercury intrusion porosimetry measurements suggested that the gas diffusion layer was changed by the first freeze cycles. The micrographs (SEM) further proved no membrane electrode assembly (MEA) delamination. These results shed some light on the relationship of the water amount in the cell to subzero temperature exposure. (author)

  3. Laminated adsorbents with very rapid CO2 uptake by freeze-casting of zeolites.

    Science.gov (United States)

    Ojuva, Arto; Akhtar, Farid; Tomsia, Antoni P; Bergström, Lennart

    2013-04-10

    Structured zeolite 13X monoliths with a laminated structure and hierarchical macro-/microporosity were prepared by freeze-casting aqueous suspensions of zeolite 13X powder, bentonite, and polyethylene glycol. Colloidally stable suspensions with a low viscosity at both room temperature and near freezing could be prepared at alkaline conditions where both the zeolite 13X powder and bentonite carry a negative surface charge. Slow directional freezing of the suspensions led to the formation of well-defined and thin lamellar pores and pore walls while fast freezing resulted in more cylindrical pores. The wall thickness, which varied between 8 and 35 μm, increased with increasing solids loading of the suspension. Thermal treatment at 1053 K of the freeze-cast bodies containing between 9 and 17 wt % bentonite resulted in mechanically stable zeolite 13X monoliths. The monoliths displayed a carbon dioxide uptake capacity of 4-5 mmol/g and an uptake kinetics characterized by a very fast initial uptake where more than 50% of the maximum uptake was reached within 15 s. Freeze-cast laminated zeolite monoliths could be used to improve the volumetric efficiency and reduce the cycle time, of importance in, for example, biogas upgrading and CO2 separation from flue gas.

  4. Investigation of fundamental and high order optical transitions in α-Fe2O3 thin films using surface barrier electroreflectance

    Science.gov (United States)

    Qayyum, H. A.; Al-Kuhaili, M. F.; Durrani, S. M. A.

    2017-10-01

    In this paper, we use surface barrier electroreflectance technique to probe the optical transitions in hematite (α-Fe2O3) thin film. An electric field was induced normal to the surface of α-Fe2O3 thin film in an Ag/α-Fe2O3/Ag based capacitor type structure and the corresponding electroreflectance analysis was performed. Based on the electroreflectance analysis, we observed the fundamental as well as two high order critical points associated with α-Fe2O3. Standard critical point model was used to find the exact energy locations and the broadening parameters associated with these critical points. The existence of the fundamental critical point was further confirmed by the spectrophotometric analysis. The quantitative analysis based on the electro-optic energy confirmed that the obtained electroreflectance spectrum was within the low field regime, and the obtained critical points above the fundamental transition were attributed to the high order transitions of electrons from the valence band to the deep in the conduction band.

  5. Half-Metallic Ferromagnetism and Surface Functionalization-Induced Metal-Insulator Transition in Graphene-like Two-Dimensional Cr2C Crystals.

    Science.gov (United States)

    Si, Chen; Zhou, Jian; Sun, Zhimei

    2015-08-12

    Graphene-like two-dimensional materials have garnered tremendous interest as emerging device materials for nanoelectronics due to their remarkable properties. However, their applications in spintronics have been limited by the lack of intrinsic magnetism. Here, using hybrid density functional theory, we predict ferromagnetic behavior in a graphene-like two-dimensional Cr2C crystal that belongs to the MXenes family. The ferromagnetism, arising from the itinerant Cr d electrons, introduces intrinsic half-metallicity in Cr2C MXene, with the half-metallic gap as large as 2.85 eV. We also demonstrate a ferromagnetic-antiferromagnetic transition accompanied by a metal to insulator transition in Cr2C, caused by surface functionalization with F, OH, H, or Cl groups. Moreover, the energy gap of the antiferromagnetic insulating state is controllable by changing the type of functional groups. We further point out that the localization of Cr d electrons induced by the surface functionalization is responsible for the ferromagnetic-antiferromagnetic and metal to insulator transitions. Our results highlight a new promising material with tunable magnetic and electronic properties toward nanoscale spintronics and electronics applications.

  6. Isochoric and isobaric freezing of fish muscle.

    Science.gov (United States)

    Năstase, Gabriel; Lyu, Chenang; Ukpai, Gideon; Şerban, Alexandru; Rubinsky, Boris

    2017-04-01

    We have recently shown that, a living organism, which succumbs to freezing to -4 °C in an isobaric thermodynamic system (constant atmospheric pressure), can survive freezing to -4 °C in an isochoric thermodynamic system (constant volume). It is known that the mechanism of cell damage in an isobaric system is the freezing caused increase in extracellular osmolality, and, the consequent cell dehydration. An explanation for the observed survival during isochoric freezing is the thermodynamic modeling supported hypothesis that, in the isochoric frozen solution the extracellular osmolality is comparable to the cell intracellular osmolality. Therefore, cells in the isochoric frozen organism do not dehydrate, and the tissue maintains its morphological integrity. Comparing the histology of: a) fresh fish white muscle, b) fresh muscle frozen to -5 °C in an isobaric system and c) fresh muscle frozen to -5 °C I in an isochoric system, we find convincing evidence of the mechanism of cell dehydration during isobaric freezing. In contrast, the muscle tissue frozen to -5 °C in an isochoric system appears morphologically identical to fresh tissue, with no evidence of dehydration. This is the first experimental evidence in support of the hypothesis that in isochoric freezing there is no cellular dehydration and therefore the morphology of the frozen tissue remains intact. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

    2015-09-14

    Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co3O4 or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

  8. Structure, Mobility, and Composition of Transition Metal Catalyst Surfaces. High-Pressure Scanning Tunneling Microscopy and Ambient-Pressure X-ray Photoelectron Spectroscopy Studies

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhongwei [Univ. of California, Berkeley, CA (United States)

    2013-12-06

    Surface structure, mobility, and composition of transition metal catalysts were studied by high-pressure scanning tunneling microscopy (HP-STM) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at high gas pressures. HP-STM makes it possible to determine the atomic or molecular rearrangement at catalyst surfaces, particularly at the low-coordinated active surface sites. AP-XPS monitors changes in elemental composition and chemical states of catalysts in response to variations in gas environments. Stepped Pt and Cu single crystals, the hexagonally reconstructed Pt(100) single crystal, and Pt-based bimetallic nanoparticles with controlled size, shape and composition, were employed as the model catalysts for experiments in this thesis.

  9. High pressure freezing/freeze substitution fixation improves the ultrastructural assessment of Wolbachia endosymbiont-filarial nematode host interaction.

    Science.gov (United States)

    Fischer, Kerstin; Beatty, Wandy L; Weil, Gary J; Fischer, Peter U

    2014-01-01

    Wolbachia α-proteobacteria are essential for growth, reproduction and survival for many filarial nematode parasites of medical and veterinary importance. Endobacteria were discovered in filarial parasites by transmission electron microscopy in the 1970's using chemically fixed specimens. Despite improvements of fixation and electron microscopy techniques during the last decades, methods to study the Wolbachia/filaria interaction on the ultrastructural level remained unchanged and the mechanisms for exchange of materials and for motility of endobacteria are not known. We used high pressure freezing/freeze substitution to improve fixation of Brugia malayi and its endosymbiont, and this led to improved visualization of different morphological forms of Wolbachia. The three concentric, bilayer membranes that surround the endobacterial cytoplasm were well preserved. Vesicles with identical membrane structures were identified close to the endobacteria, and multiple bacteria were sometimes enclosed within a single outer membrane. Immunogold electron microscopy using a monoclonal antibody directed against Wolbachia surface protein-1 labeled the membranes that enclose Wolbachia and Wolbachia-associated vesicles. High densities of Wolbachia were observed in the lateral chords of L4 larvae, immature, and mature adult worms. Extracellular Wolbachia were sometimes present in the pseudocoelomic cavity near the developing female reproductive organs. Wolbachia-associated actin tails were not observed. Wolbachia motility may be explained by their residence within vacuoles, as they may co-opt the host cell's secretory pathway to move within and between cells. High pressure freezing/freeze substitution significantly improved the preservation of filarial tissues for electron microscopy to reveal membranes and sub cellular structures that could be crucial for exchange of materials between Wolbachia and its host.

  10. Multiproxy record of abrupt sea-surface cooling across the Eocene-Oligocene transition in the Gulf of Mexico

    NARCIS (Netherlands)

    Wade, B.S.; Houben, A.J.P.; Quaijtaal, W.; Schouten, S.; Rosenthal, Y.; Miller, K.G.; Katz, M.E.; Wright, J.D.; Brinkhuis, H.

    2012-01-01

    The Eocene-Oligocene transition (EOT; ca. 33–34 Ma) was a time of pronounced climatic change, marked by the establishment of continental-scale Antarctic ice sheets. The timing and extent of temperature change associated with the EOT is controversial. Here we present multiproxy EOT climate records

  11. Climatic variation and seed persistence: freeze-thaw cycles lower survival via the joint action of abiotic stress and fungal pathogens.

    Science.gov (United States)

    Connolly, Brian M; Orrock, John L

    2015-10-01

    Global climate change is altering thermal cycles in soils during late winter, a transition that may directly threaten seed survival via abiotic stress, facilitate infection by soil-borne pathogens, or both. Using field-collected soil and seeds of the perennial bunchgrass Elymus canadensis, we tested the hypothesis that soil freeze-thaw events limit survival within the soil through direct effects on seed persistence and amplification of soil pathogen attack using a factorial experiment that manipulated freeze-thaw cycles (constant freeze vs. freeze-thaw) and fungicide addition. Freeze-thaw treatment resulted in lower seedling emergence and delayed emergence time relative to constant-freeze controls. Fungicide-treated soils had greater emergence relative to untreated soils; the lowest seedling emergence was observed in no-fungicide, freeze-thaw-treated soils (fungi on seeds were mitigated through interactions at the seed-soil interface, as subsequent experiments showed that fungicide and freeze-thaw treatments alone do not influence dormancy. Our work demonstrates that changes in freeze-thaw events directly limit seedling emergence, delay seedling phenology, and provide opportunities for fungal pathogens to limit seed persistence. As recruitment from seeds is a key determinant of plant population dynamics, these results suggest that climatic variation may generate unique consequences for populations under changing climate regimes.

  12. Cell growth and resistance of Lactococcus lactis subsp. lactis TOMSC161 following freezing, drying and freeze-dried storage are differentially affected by fermentation conditions.

    Science.gov (United States)

    Velly, H; Fonseca, F; Passot, S; Delacroix-Buchet, A; Bouix, M

    2014-09-01

    To investigate the effects of fermentation parameters on the cell growth and on the resistance to each step of the freeze-drying process of Lactococcus lactis subsp. lactis TOMSC161, a natural cheese isolate, using a response surface methodology. Cells were cultivated at different temperatures (22, 30 and 38°C) and pH (5·6, 6·2 and 6·8) and were harvested at different growth phases (0, 3 and 6 h of stationary phase). Cultivability and acidification activity losses of Lc. lactis were quantified after freezing, drying, 1 and 3 months of storage at 4 and 25°C. Lactococcus lactis was not damaged by freezing but was sensitive to drying and to ambient temperature storage. Moreover, the fermentation temperature and the harvesting time influenced the drying resistance of Lc. lactis. Lactococcus lactis cells grown in a whey-based medium at 32°C, pH 6·2 and harvested at late stationary phase exhibited both an optimal growth and the highest resistance to freeze-drying and storage. A better insight on the individual and interaction effects of fermentation parameters made it possible the freeze-drying and storage preservation of a sensitive strain of technological interest. Evidence on the particularly damaging effect of the drying step and the high-temperature storage is presented. © 2014 The Society for Applied Microbiology.

  13. Freeze Drying Technology and Its Stages (Turkish with English Abstract)

    OpenAIRE

    Sadıkoğlu, Hasan; Özdemir, Murat

    2015-01-01

    Many pharmaceutical and food products when they are in solution are susceptible to deactivation over a period of time. Such materials are freeze dried soon after their production in order to stabilize them and; therefore, they keep their bioactivity for a long time. In this study, first of all, the principle of freeze drying process was described. Next, the importance of freezing in the freeze drying was emphasized and the key points in a freeze drying operation were presented. Finally, first...

  14. Effect of transition metal Fe adsorption on CeO2 (110) surface in the methane activation and oxygen vacancy formation: A density functional theory study

    Science.gov (United States)

    Tian, Dong; Zeng, Chunhua; Wang, Hua; Cheng, Xianming; Zheng, Yane; Xiang, Chao; Wei, Yonggang; Li, Kongzhai; Zhu, Xing

    2017-09-01

    Methane activation and oxygen vacancy formation over transition metal Fe adsorption on CeO2 (110) are studied by using the method of density functional theory (DFT) + U method. A set of model configurations are generated by placing Fe at five surface sites, viz., O-top site, O-bridge site, Ce-bridge site, Ce-top and double oxygen-bridge sites. The study shows that the energetically most favorable configuration is Fe adsorption at the double oxygen-bridge site. Based on the calculated surface, subsurface and the second oxygen vacancies formation energy with (or without) Fe adsorption, it shows that the Fe adsorption is in favor of the surface, subsurface and second oxygen vacancies formation. For the surface and subsurface oxygen vacancy on the Fe/CeO2 (110) surface, the main factor responsible for lowering of Evac is that the adsorption induces structural distortions, whereas, for the second oxygen vacancy, half can be attributed to the large structural relaxation, half can be attributed to the electronic effects. After calculating and discussing about the CH4 activation on CeO2 (110) and Fe/CeO2 (110) surface with (or without) the surface or subsurface oxygen vacancies at the possible adsorption sites, the results show that when the CH4 adsorbed on the Fe/CeO2 (110) with the surface oxygen vacancy at the Ce1 and Ce2 sites, the CH4 decomposed into the CH(ads) and H(ads), its belongs to the chemical absorption, whereas, when the CH4 adsorbed on the other possible sites, the mentioned phenomenon is not occurred, its belongs to the physical absorption. This study reveals the correlation between surface reducibility and catalytic activity for methane oxidation on cerium-based materials, which might be beneficial in developing improved catalysts for methane combustion.

  15. Effects of Periodic Unsteady Wake Flow and Pressure Gradient on Boundary Layer Transition Along the Concave Surface of a Curved Plate. Part 3

    Science.gov (United States)

    Schobeiri, M. T.; Radke, R. E.

    1996-01-01

    Boundary layer transition and development on a turbomachinery blade is subjected to highly periodic unsteady turbulent flow, pressure gradient in longitudinal as well as lateral direction, and surface curvature. To study the effects of periodic unsteady wakes on the concave surface of a turbine blade, a curved plate was utilized. On the concave surface of this plate, detailed experimental investigations were carried out under zero and negative pressure gradient. The measurements were performed in an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate. Boundary layer measurements using a hot-wire probe were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. As the results show, the turbulent patches generated by the wakes have different leading and trailing edge velocities and merge with the boundary layer resulting in a strong deformation and generation of a high turbulence intensity core. After the turbulent patch has totally penetrated into the boundary layer, pronounced becalmed regions were formed behind the turbulent patch and were extended far beyond the point they would occur in the corresponding undisturbed steady boundary layer.

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

    Science.gov (United States)

    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...

  17. Cryoprotectants for freeze drying of drug nano-suspensions: effect of freezing rate.

    Science.gov (United States)

    Lee, Min Kyung; Kim, Min Young; Kim, Sujung; Lee, Jonghwi

    2009-12-01

    Drug nanoparticles are often prepared in a liquid medium, and a drying method such as freeze drying is used to convert them to an oral solid dosage form. When the dried form is reconstituted in an aqueous system, it may be redispersed to achieve its original particle size. The redispersibility of dried nanoparticles depends on the parameters of the freeze drying process. In this study, an apparatus with a freezing rate gradient was used to systematically investigate the effect of cryoprotectants on the redispersibility of nanoparticles as a function of freezing rate. Sucrose, lactose, mannitol, and polyethylene glycol were used as cryoprotectants for a naproxen nano-suspension. A fast freezing rate and a high cryoprotectant concentration were generally favored. However, under certain conditions, a slower freezing rate resulted in better redispersibility. This is probably because slow freezing can produce a more cryo-concentrated liquid phase, and the concentrated cryoprotectant in the liquid phase can more effectively protect the nanoparticles. An irreversible aggregation map was constructed as a function of the freezing rate and the cryoprotectant concentration, and shows both the favorable and unfavorable effects of cryoprotectants. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

  18. Immersion freezing of biological particles at LACIS

    Science.gov (United States)

    Clauss, T.; Hartmann, S.; Temkiv, T. S.; Augustin, S.; Gosewinkel Karlson, U.; Sahyoun, M. M.; Niedermeier, D.; Wex, H.; Voigtländer, J.; Raddatz, M.; Stratmann, F.

    2012-04-01

    Biological particles, especially bacteria being ubiquitous in the atmosphere, belong to the most efficient ice nuclei (IN) (Möhler, 2008) and hence might have a large impact on weather and climate. In this study, the immersion freezing behavior of different size segregated biological particles is investigated at the laminar flow tube LACIS (Leipzig Aerosol Cloud Interaction Simulator, Hartmann et al., 2011). For these experiments, SNOMAX and outer membrane vesicles (OMV) are used as IN. SNOMAX industrially produced from Pseudomonas-syringae bacteria, which are very ice nucleation active, can be seen as a proxy for ice nucleating bacteria in general. On the surface of these bacteria, ice nucleating proteins that initiate the freezing are situated (Maki et al., 1974). Additionally, it has been found that some ice nucleating bacteria strains have the ability to produce OMV, i.e., strangulated parts of the bacterial cell consisting of the same membrane material (Phelps et al., 1986). These OMV might contain the same ice nucleating proteins on their surface and thus might be able to nucleate ice as well. The OMV used in our experiments were extracted from bacteria cultivated from rain samples collected in Denmark from 30 m height. In our experiments, the biological particles are suspended in air via atomization, size selected by means of a Differential Mobility Particle Sizer, and then fed into LACIS. In LACIS, well defined droplets are produced by activating the biological particles to cloud droplets, so that each droplet contains only one biological particle. By decreasing the temperature in LACIS, these droplets are frozen. To determine the ice fraction, i.e., the fraction of frozen droplets to all particles, the liquid and frozen droplets are distinguished by means of a newly self-built optical device, which is positioned under LACIS, using the depolarization of light scattered by a single particle. The ice fractions are measured as a function of temperature and

  19. Analysis of Different Freezing/Thawing Parameterizations using the UTOPIA Model

    Directory of Open Access Journals (Sweden)

    Claudio Cassardo

    2010-08-01

    Full Text Available Soil moisture changes are generally due to external factors (precipitation, evaporation, etc. and internal forces (gravitational force, capillarity, transpiration, etc.. When soil temperatures remain below 0 °C for a long time (hours or even entire consecutive days, part of the liquid water content of the soil can freeze, thus freezing/thawing effects must be taken into account in those conditions. The present work is devoted to the numerical modeling of the water phase change in the soil. The model used in this study for the land surface processes is UTOPIA (University of TOrino land Process Interaction in Atmosphere model, which is the updated version of LSPM (Land Surface Process Model. Scientific literature proposes some formulations to account for freezing/thawing processes. Three different parameterizations have been compared using a synthetic dataset in order to assess which one performs best from a physical point of view. Parameterizing freezing/thawing processes creates numerical instability and water overproduction in the UTOPIA model. These problems have been solved and described in the paper by means of synthetic data created to test the new parameterizations. The results show that UTOPIA is able to capture the freezing/thawing physical processes.

  20. First-principles Study of Charge Density Waves and Electron-phonon Coupling in Transition Metal Dichalcogenides, and Magnetism of Surface Adatoms

    Science.gov (United States)

    Albertini, Oliver Ruben

    Recently, low-dimensional materials have attracted great attention, not only because of novel physics, but also because of potential applications in electronic devices, where performance drives innovation. This thesis presents theoretical and computational studies of magnetic adatoms on surfaces and of charge density wave (CDW) phases in two-dimensional materials. We investigate the structural, electronic, and magnetic properties of Ni adatoms on an MgO/Ag(100) surface. Using density functional theory, we find that strong bonding is detrimental to the magnetic moment of an atom adsorbed on a surface. Previously, it was shown that Co retains its full gas-phase magnetic moment on the MgO/Ag(100) surface. For Ni we find the total value of spin depends strongly on the binding site, and there are two sites close in energy. Next, we study the 1T polymorph of the transition metal dichalcogenide TaS2. Bulk 1T-TaS2 is metallic at high temperatures, but adopts an insulating commensurate CDW below 180 K. The nature of the transition is under debate, and it is unclear whether the transition persists down to a monolayer. Transport and Raman measurements suggest that the commensurate CDW is absent in samples thinner than 10 layers. Our theoretical and experimental study of the vibrational properties of 1 T-TaS2 demonstrates that the commensurate CDW is robust upon thinning -- even down to a single layer. Bulk 2H-TaS2 also has a CDW instability at low temperatures. A recent study of a single layer of 1H-TaS 2 grown on Au(111) revealed that the CDW phase is suppressed down to temperatures well below the bulk transition temperature (75 K), possibly due to electron doping from the substrate. We present a first-principles study of the effects of electron doping on the CDW instability in monolayer 1 H-TaS2, finding that electron doping: 1) shifts the electronic bands by 0.1 eV; 2) impacts the strength and wave vector dependence of electron-phonon coupling in the system, suppressing

  1. SENSITIVE TO FREEZING2 Aides in Resilience to Salt and Drought in Freezing-Sensitive Tomato.

    Science.gov (United States)

    Wang, Kun; Hersh, Hope Lynn; Benning, Christoph

    2016-11-01

    SENSITIVE TO FREEZING2 (SFR2) is crucial for protecting chloroplast membranes following freezing in Arabidopsis (Arabidopsis thaliana). It has been shown that SFR2 homologs are present in all land plants, including freezing-sensitive species, raising the question of SFR2 function beyond freezing tolerance. Similar to freezing, salt and drought can cause dehydration. Thus, it is hypothesized that in freezing-sensitive plants SFR2 may play roles in their resilience to salt or drought. To test this hypothesis, SlSFR2 RNAi lines were generated in the cold/freezing-sensitive species tomato (Solanum lycopersicum [M82 cv]). Hypersensitivity to salt and drought of SlSFR2-RNAi lines was observed. Higher tolerance of wild-type tomatoes was correlated with the production of trigalactosyldiacylglycerol, a product of SFR2 activity. Tomato SFR2 in vitro activity is Mg 2+ -dependent and its optimal pH is 7.5, similar to that of Arabidopsis SFR2, but the specific activity of tomato SFR2 in vitro is almost double that of Arabidopsis SFR2. When salt and drought stress were applied to Arabidopsis, no conditions could be identified at which SFR2 was induced prior to irreversibly impacting plant growth, suggesting that SFR2 protects Arabidopsis primarily against freezing. Discovery of tomato SFR2 function in drought and salt resilience provides further insights into general membrane lipid remodeling-based stress tolerance mechanisms and together with protection against freezing in freezing-resistant plants such as Arabidopsis, it adds lipid remodeling as a possible target for the engineering of abiotic stress-resilient crops. © 2016 American Society of Plant Biologists. All Rights Reserved.

  2. Freeze-drying of lactic acid bacteria.

    Science.gov (United States)

    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.

  3. The Transition of High-Resolution NASA MODIS Sea Surface Temperatures into the WRF Environmental Modeling System

    Science.gov (United States)

    Case, Jonathan L.; Jedlove, Gary J.; Santos, Pablo; Medlin, Jeffrey M.; Rozumalski, Robert A.

    2009-01-01

    The NASA Short-term Prediction Research and Transition (SPoRT) Center has developed a Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) composite at 2-km resolution that has been implemented in version 3 of the National Weather Service (NWS) Weather Research and Forecasting (WRF) Environmental Modeling System (EMS). The WRF EMS is a complete, full physics numerical weather prediction package that incorporates dynamical cores from both the Advanced Research WRF (ARW) and the Non-hydrostatic Mesoscale Model (NMM). The installation, configuration, and execution of either the ARW or NMM models is greatly simplified by the WRF EMS to encourage its use by NWS Weather Forecast Offices (WFOs) and the university community. The WRF EMS is easy to run on most Linux workstations and clusters without the need for compilers. Version 3 of the WRF EMS contains the most recent public release of the WRF-NMM and ARW modeling system (version 3 of the ARW is described in Skamarock et al. 2008), the WRF Pre-processing System (WPS) utilities, and the WRF Post-Processing program. The system is developed and maintained by the NWS National Science Operations Officer Science and Training Resource Coordinator. To initialize the WRF EMS with high-resolution MODIS SSTs, SPoRT developed the composite product consisting of MODIS SSTs over oceans and large lakes with the NCEP Real-Time Global (RTG) filling data over land points. Filling the land points is required due to minor inconsistencies between the WRF land-sea mask and that used to generate the MODIS SST composites. This methodology ensures a continuous field that adequately initializes all appropriate arrays in WRF. MODIS composites covering the Gulf of Mexico, western Atlantic Ocean and the Caribbean are generated daily at 0400, 0700, 1600, and 1900 UTC corresponding to overpass times of the NASA Aqua and Terra polar orbiting satellites. The MODIS SST product is output in gridded binary-1 (GRIB-1) data

  4. Turbulence kinetic energy budget during the afternoon transition - Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days

    Science.gov (United States)

    Nilsson, Erik; Lohou, Fabienne; Lothon, Marie; Pardyjak, Eric; Mahrt, Larry; Darbieu, Clara

    2016-07-01

    The decay of turbulence kinetic energy (TKE) and its budget in the afternoon period from midday until zero-buoyancy flux at the surface is studied in a two-part paper by means of measurements from the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign for 10 intensive observation period days. Here, in Part 1, near-surface measurements from a small tower are used to estimate a TKE budget. The overall boundary layer characteristics and mesoscale situation at the site are also described based upon taller tower measurements, radiosoundings and remote sensing instrumentation. Analysis of the TKE budget during the afternoon transition reveals a variety of different surface layer dynamics in terms of TKE and TKE decay. This is largely attributed to variations in the 8 m wind speed, which is responsible for different amounts of near-surface shear production on different afternoons and variations within some of the afternoon periods. The partitioning of near-surface production into local dissipation and transport in neutral and unstably stratified conditions was investigated. Although variations exist both between and within afternoons, as a rule of thumb, our results suggest that about 50 % of the near-surface production of TKE is compensated for by local dissipation near the surface, leaving about 50 % available for transport. This result indicates that it is important to also consider TKE transport as a factor influencing the near-surface TKE decay rate, which in many earlier studies has mainly been linked with the production terms of TKE by buoyancy and wind shear. We also conclude that the TKE tendency is smaller than the other budget terms, indicating a quasi-stationary evolution of TKE in the afternoon transition. Even though the TKE tendency was observed to be small, a strong correlation to mean buoyancy production of -0.69 was found for the afternoon period. For comparison with previous results, the TKE budget terms are normalized with

  5. Percolation Phase Transition of Surface Air Temperature Networks: A new test bed for El Niño/La Niña simulations.

    Science.gov (United States)

    Hua, Lijuan; Lu, Zhenghui; Yuan, Naiming; Chen, Lin; Yu, Yongqiang; Wang, Lu

    2017-08-16

    In this work, we studied the air-sea interaction over the tropical central eastern Pacific from a new perspective, climate network. The surface air temperatures over the tropical Pacific were constructed as a network, and the nodes within this network were linked if they have a similar temporal varying pattern. Using three different reanalysis datasets, we verified the percolation phase transition. That is, when the influences of El Niño/La Niña are strong enough to isolate more than 48% of the nodes, the network may abruptly be divided into many small pieces, indicating a change of the network state. This phenomenon was reproduced successfully by a coupled general circulation model, Flexible Global Ocean-Atmosphere-Land System Model Spectral Version 2, but another model, Flexible Global Ocean-Atmosphere-Land System Model Grid-point Version 2, failed. As both models have the same oceanic component, but are with different atmospheric components, the improperly used atmospheric component should be responsible for the missing of the percolation phase transition. Considering that this new phenomenon is only recently noticed, current state-of-the-art models may ignore this process and induce unrealistic simulations. Accordingly, percolation phase transition is proposed as a new test bed, which deserves more attention in the future.

  6. Transitions for fipronil quant in surface water, Summary of Current Fipronil Water Data and Water Data for WWTPs

    Data.gov (United States)

    U.S. Environmental Protection Agency — Comparison of fipronil sources in North Carolina surface water and identification of a novel fipronil transformation product in recycled wastewater. This dataset is...

  7. Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces

    Science.gov (United States)

    de Aguiar, Kelen R.; Rischka, Klaus; Gätjen, Linda; Noeske, Paul-Ludwig Michael; Cavalcanti, Welchy Leite; Rodrigues-Filho, Ubirajara P.

    2018-01-01

    The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strongly attach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane (CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobic PDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2 surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile

  8. Reversible and irreversible changes of surface morphology by order-disorder transition in CuAu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sachl, Jindrich; Sima, Vladimir; Pfeiler, Wolfgang

    2004-09-22

    The change of symmetry from the disordered fcc structure to tetragonal or orthorhombic structure is accompanied in CuAu alloy by anisotropy of lattice parameters and also by local generation of c-variants of structural antiphase domains. Macroscopic results of these processes can be observed as a dynamic change of the surface morphology. Some surface changes are reversible, on the other hand the internal stresses connected with the order-disorder transformation are also responsible for irreversible surface deformation effects. The domain structure formation can be influenced by external load and a shape memory effect can be observed at special conditions in CuAu. A combination of in-situ microscopic video cinematography and post-mortem 3-D atomic force microscopy (AFM) has been used for the surface study. The AFM images have enabled a detailed analysis of the surface morphology and the cinematography has given an in-situ information dealing with conditions and kinetics of observed surface changes. Measurements on CuAu single- and poly-crystalline samples have been made for a wide variety of experimental conditions (heating/cooling rates, external load, thermal history of the sample)

  9. Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskii, V. V.

    1984-04-01

    Nonlinear interactions (including wavefront reversal) of light from CW or pulsed 10.6-micron CO2 lasers at the semiconductor-metal phase transition in a VO2 film are investigated experimentally. The results are presented in graphs and characterized in detail. The intensity reflection coefficients of the three-wave interactions are found to be 0.5 percent for a CW reference wave of intensity 900 mW/sq cm and 42 percent for a pulsed reference wave of threshold density 600-800 microjoule/sq cm.

  10. Dry deposition of pollutant and marker particles onto live mouse airway surfaces enhances monitoring of individual particle mucociliary transit behaviour.

    Science.gov (United States)

    Donnelley, Martin; Morgan, Kaye S; Siu, Karen K W; Parsons, David W

    2012-07-01

    Particles suspended in the air are inhaled during normal respiration and unless cleared by airway defences, such as the mucociliary transit (MCT) system, they can remain and affect lung and airway health. Synchrotron phase-contrast X-ray imaging (PCXI) methods have been developed to non-invasively monitor the behaviour of individual particles in live mouse airways and in previous studies the MCT behaviour of particles and fibres in the airways of live mice after deposition in a saline carrier fluid have been examined. In this study a range of common respirable pollutant particles (lead dust, quarry dust and fibreglass fibres) as well as marker particles (hollow glass micro-spheres) were delivered into the trachea of live mice using a dry powder insufflator to more accurately mimic normal environmental particulate exposure and deposition via inhalation. The behaviour of the particles once delivered onto the airway surface was tracked over a five minute period via PCXI. All particles were visible after deposition. Fibreglass fibres remained stationary throughout while all other particle types transited the tracheal surface throughout the imaging period. In all cases the majority of the particle deposition and any airway surface activity was located close to the dorsal tracheal wall. Both the individual and bulk motions of the glass bead marker particles were visible and their behaviour enabled otherwise hidden MCT patterns to be revealed. This study verified the value of PCXI for examining the post-deposition particulate MCT behaviour in the mouse trachea and highlighted that MCT is not a uniform process as suggested by radiolabel studies. It also directly revealed the advantages of dry particle delivery for establishing adequate particulate presence for visualizing MCT behaviour. The MCT behaviour and rate seen after dry particle delivery was different from that in previous carrier-fluid studies. It is proposed that dry particle delivery is essential for producing

  11. Heat transfer coefficient of cryotop during freezing.

    Science.gov (United States)

    Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

    2013-01-01

    Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

  12. Immersion freezing of ice nucleation active protein complexes

    Directory of Open Access Journals (Sweden)

    S. Hartmann

    2013-06-01

    nucleation are attached to the outer membrane of intact bacteria or membrane fragments, (c the temperature range in which heterogeneous droplet freezing occurs, and the fraction of droplets being able to freeze, both depend on the actual number of INA protein complexes present in the droplet ensemble, and (d possible artifacts suspected to occur in connection with the drop freezing method, i.e., the method frequently used by biologist for quantifying ice nucleation behaviour, are of minor importance, at least for substances such as P. syringae, which induce freezing at comparably high temperatures. The last statement implies that for single ice nucleation entities such as INA protein complexes, it is the number of entities present in the droplet population, and the entities' nucleation rate, which control the freezing behaviour of the droplet population. Quantities such as ice active surface site density are not suitable in this context. The results obtained in this study allow a different perspective on the quantification of the immersion freezing behaviour of bacterial ice nucleation.

  13. Measuring thermal conductivity in freezing and thawing soil using the soil temperature response to heating

    NARCIS (Netherlands)

    Overduin, P.; Kane, D.L.; Loon, van W.K.P.

    2006-01-01

    The thermal conductivity of the thin seasonally freezing and thawing soil layer in permafrost landscapes exerts considerable control over the sensitivity of the permafrost to energy and mass exchanges at the surface. At the same time, the thermal conductivity is sensitive to the state of the soil,

  14. Microstructure Changes in Hardened Cement Paste after Freezing – Thawing Cycles

    Directory of Open Access Journals (Sweden)

    Gintautas SKRIPKIŪNAS

    2013-03-01

    Full Text Available This article analyses the results of the freezing – thawing with deicing salt test where changes in the microstructure of the surface layer in contact with aggressive environment of hardened cement paste produced with and without sodium silicate (hereinafter NTS admixture were observed after freeze-thaw cycles in the presence of calcium chloride. After 56 cycles of freezing – thawing with deicing salt test micro-cracks and cavities were observed in the microstructure of the surface layer of hardened cement paste with and without NTS admixture. In the case of hardened cement paste with NTS admixture changes in the microstructure of the surface layer are less prominent: the number and size of cavities and micro-cracks are smaller. The test revealed that compressive stress, which before freezing – thawing with deicing salt test was very similar in hardened cement paste with and without NTS admixture (85.4 MPa and 82.8 MPa respectively, changed after 56 cycles of freezing – thawing with deicing salt test as follows: reduced by 39.5 % in concrete without NTS admixture and increased slightly (2.5 % in hardened cement paste with NTS admixture. Based on the test results the authors arrived at the conclusion that sodium silicate solution can be effectively used to extend the useful life of hardened cement paste exposed to freeze-thaw cycles and affected by CaCl2.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3835

  15. Toward quantitative STM: Scanning tunneling microscopy study of structure and dynamics of adsorbates on transition metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dunphy, James Christopher [Univ. of California, Berkeley, CA (United States)

    1995-05-01

    STM was applied to chemisorbed S layers on Re(000l) and Mo(100) surfaces. As function of coverage on both these surfaces, S orders into several different overlayer structures, which have been studied by dynamic LEED. STM images of all these structures were obtained. Approximate location of S atoms in the structures was determined by inspecting the images, especially the regions containing defects. Results are in agreement with LEED except for the p(2xl) overlayer of sulfur on Mo(100). The STM images were compared to calculations made with Electron Scattering Quantum Chemistry (ESQC) theory. Variation of contrast in experimental images is explained as a result of changes in STM tip termination structure. STM image contrast is a result of changes in the interference between different paths for the tunneling electrons. The simplest structure on the Mo(100) surface was used as a model for developing and testing a method of quantitative structure determination with the STM. Experimental STM images acquired under a range of tunneling conditions were compared to theoretical calculations of the images as a function of surface structure to determine the structure which best fit. Results matched within approximately 0.1 Angstroms a LEED structural determination. At lower S coverage, diffusion of S atoms over the Re(0001) surface and the lateral interaction between these atoms were investigated by application of a new image analysis technique. The interaction between the S and a coadsorbed CO layer was also studied, and CO was found to induce compression of the S overlayer. A similar result was found for Au deposited on the sulfur covered Mo(100) surface. The interaction between steps on the Mo surface was found to be influenced by S adsorption and this observation was interpreted with the theory of equilibrium crystal shape. Design of an STM instrument which operates at cryogenic and variable sample temperatures, and its future applications, are described.

  16. Substrate Dependence of the Freezing Dynamics of Supercooled Water Films: A High-Speed Optical Microscope Study.

    Science.gov (United States)

    Pach, E; Rodriguez, L; Verdaguer, A

    2018-01-18

    The freezing of supercooled water films on different substrates was investigated using a high-speed camera coupled to an optical microscope, obtaining details of the freezing process not described in the literature before. We observed the two well known freezing stages (fast dendritic growth and slow freezing of the water liquid left after the dendritic growth), but we separated the process into different phenomena that were studied separately: two-dimensional dendrite growth on the substrate interface, vertical dendrite growth, formation and evolution of ice domains, trapping of air bubbles and freezing of the water film surface. We found all of these processes to be dependent on both the supercooling temperature and the substrate used. Ice dendrite (or ice front) growth during the first stage was found to be dependent on thermal properties of the substrate but could not be unequivocally related to them. Finally, for low supercooling, a direct relationship was observed between the morphology of the dendrites formed in the first stage, which depends on the substrate, and the roughness and the shape of the surface of the ice, when freezing of the film was completed. This opens the possibility of using surfaces and coatings to control ice morphology beyond anti-icing properties.

  17. Novel ultra-rapid freezing particle engineering process for enhancement of dissolution rates of poorly water-soluble drugs.

    Science.gov (United States)

    Overhoff, Kirk A; Engstrom, Josh D; Chen, Bo; Scherzer, Brian D; Milner, Thomas E; Johnston, Keith P; Williams, Robert O

    2007-01-01

    An ultra-rapid freezing (URF) technology has been developed to produce high surface area powders composed of solid solutions of an active pharmaceutical ingredient (API) and a polymer stabilizer. A solution of API and polymer excipient(s) is spread on a cold solid surface to form a thin film that freezes in 50 ms to 1s. This study provides an understanding of how the solvent's physical properties and the thin film geometry influence the freezing rate and consequently the final physico-chemical properties of URF-processed powders. Theoretical calculations of heat transfer rates are shown to be in agreement with infrared images with 10ms resolution. Danazol (DAN)/polyvinylpyrrolidone (PVP) powders, produced from both acetonitrile (ACN) and tert-butanol (T-BUT) as the solvent, were amorphous with high surface areas (approximately 28-30 m2/g) and enhanced dissolution rates. However, differences in surface morphology were observed and attributed to the cooling rate (film thickness) as predicted by the model. Relative to spray-freezing processes that use liquid nitrogen, URF also offers fast heat transfer rates as a result of the intimate contact between the solution and cold solid surface, but without the complexity of cryogen evaporation (Leidenfrost effect). The ability to produce amorphous high surface area powders with submicron primary particles with a simple ultra-rapid freezing process is of practical interest in particle engineering to increase dissolution rates, and ultimately bioavailability.

  18. Cryoprotectant Production in Freeze-Tolerant Wood Frogs Is Augmented by Multiple Freeze-Thaw Cycles.

    Science.gov (United States)

    Larson, Don J; Barnes, Brian M

    2016-01-01

    Ice nucleation across the skin of wood frogs (Lithobates sylvaticus) rapidly induces endogenous production of glucose, a cryoprotectant necessary for freeze tolerance. In laboratory studies of freeze tolerance, wood frogs are cooled slowly, often at -0.05°C h(-1), to facilitate high cryoprotectant production and survival. Under natural conditions in Alaska, however, wood frogs accumulate maximal tissue glucose concentrations while cooling at much faster rates, -0.35° to -1.6°C h(-1), and in addition undergo multiple successive freeze-thaw cycles before remaining frozen for the winter. We examined whether simulating these ecologically relevant cooling rates and repeated freeze-thaw events in captive wood frogs results in the high glucose concentrations found in naturally frozen wood frogs. We found that over successive freezing and thawing events, glucose concentrations increased stepwise in all measured tissues. Short thawing periods did not result in a statistically significant decline of glucose concentrations. Wood frogs that experienced three freeze-thaw events had fresh weight glucose concentrations that approached values found in tissues of wood frogs frozen in natural conditions. Laboratory wood frogs survive frozen for 2 mo, while wood frogs frozen under natural conditions survive frozen for up to 7 mo at temperatures below -18°C. We hypothesize that repeated freeze-thaw cycles with rapid cooling and warming rates allow for greater survival in Alaskan wood frogs through enhanced cryoprotectant production.

  19. Effect of freeze-thawing on aggregate stability in a calcareous Mediterranean soil

    Science.gov (United States)

    Lozano, Elena; Temporal, Beatriz; Oltra, Ángel; Mataix-Solera, Jorge; Arcenegui, Victoria; García-Orenes, Fuensanta

    2013-04-01

    Soil freezing has been reported as both beneficial and detrimental for soil structure depending on various factors (Dagesse, 2011), but the subsequent thawing process has not been adequately investigated as a factor in determining the net effect of freezing and thawing. In this study changes in soil aggregate stability (AS) were studied under different moisture and speed of thawing conditions in a laboratory experiment. Conditions favoring sublimation and commonly experienced during the winter include bare soil surfaces and synoptic meteorological conditions of clear skies, low humidity, and moderate winds. Aggregate stability measured may therefore reflect the effects of drying of the soil aggregates via the freezing process and the resulting water content distribution following thawing. The soil used is from an agricultural area located in Sierra de Enguera (Valencia, E Spain). Soil samples were collected in February 2012 from the first 2.5 cm depth of A horizon. We also studied the effect of a mulch cover in buffering soil temperature during 2 months under field conditions using thermocouples and data-loggers. Soil samples at two initial water contents (10% and 40%) were subjected to different treatments, including not frozen (control), freeze-thaw (freezing at -4 °C for 3 h and thawing at room temperature for 24 h) and freeze-drying (freezing at -4 for 3h and thawing at 60 °C for 3 h in a forced air oven). We measured the possible soil disruption of soil aggregates quantifying the soil mass in the fractions 2-0.25 mm and

  20. Experimental evaluation of freezing preparation for the macroscopic inspection in putrefied brain.

    Science.gov (United States)

    Hyodoh, Hideki; Matoba, Kotaro; Murakami, Manabu; Matoba, Tomoko; Saito, Atsuko; Feng, Fei; Jin, Shigeki

    2017-01-01

    To evaluate the usefulness of freezing preparation for macroscopic investigation in advanced putrefied brain. After sealing in individual plastic bags, 10 pig heads were stored at 20°C for 5days allow postmortem change (putrefaction) to progress. After an observation period, they were divided into 2 groups to evaluate the usefulness of the freezing effect in macroscopic investigation. The process over the postmortem period and the freezing process were examined. At day-5, the presence of air density was detected between the inner surface of the cranium and the brain parenchyma. Intra-cranial air accumulation presented on CT in all heads. In the control group, the brain parenchyma leaked out from the hole in the meninges, and the gray-white matter difference was clear in 3/72 (4.2%), moderate in 7/72 (9.7%), ambiguous in 17/72 (23.6%), and poor in 45/72 (62.5%). In the freezing group, the brain parenchyma presented homogeneous low density after more than 14h freezing. On opening the cranium, the entire brains were frozen, and the gray-white matter difference was clear in 33/72 (46.0%), moderate in 17/72 (24.0%), ambiguous in 15/72 (21.0%), and poor in 7/72 (10.0%). The freezing group afforded greater clarity in the gray-white matter inspection (pFreezing preparation was useful for the macroscopic investigation of putrefied brain compared with the ordinary autopsy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  1. [Optimization of the freezing process by load].

    Science.gov (United States)

    Barreiro Méndez, J A; Antunes, S A; Saíz, E; Irazábal de Guariguata, C

    1981-09-01

    A model was developed for the optimization of batch freezing to maximize the daily production of a plate freezer. An equation for the prediction of the optimal product thickness was found. The model was evaluated experimentally in a one-plate freezer with a food model consisting of a 9% bentonite mixture. The model demonstrated it predicted adequately the freezing times and optimal product thickness. Under the experimental conditions used by the authors, an optimal thickness of 0.0142 m was found, with five batches per day. The maximum daily production was 3.152 kg.

  2. Activation of antioxidant defenses in response to freezing in freeze-tolerant painted turtle hatchlings.

    Science.gov (United States)

    Krivoruchko, Anastasia; Storey, Kenneth B

    2010-07-01

    Hatchlings of the painted turtle, Chrysemys picta marginata can endure long-term freezing of their extracellular body fluids. We hypothesized that freezing survival would include adaptive up-regulation of antioxidant defenses to deal with ischemia-reperfusion injuries associated with the freeze-thaw cycle. A number of antioxidant enzymes are under the control of the NF-E2 related factor 2 (Nrf2) transcription factor including members of the glutathione S-transferase (GST) and aldo-keto reductase (AKR) families. RT-PCR and Western immunoblotting were used to measure changes in transcript and protein levels in response to 5-h freezing exposure of hatchlings. Transcript levels of Nrf2 increased in turtle brain, liver, and muscle by 1.5- to 2-fold, and protein levels increased in the brain and muscle by 1.6- to 2.3-fold in response to freezing. GSTs responded strongly to freezing in turtle brain with amounts of GSTP1, M1, K1, and A3 elevated by 1.5- to 2.4-fold. GSTM3 and T1 rose by 1.8- to 2.3-fold in gut, whereas reduced levels of GSTP1, M1, M3, and K1 were found in livers of frozen animals. Levels of the AKR1B4 isozyme rose 2.1-fold during freezing in brain. Freezing triggered tissue-specific changes in the antioxidant defenses in C.pictamarginata organs. These data indicate that activation of an antioxidant response is an important aspect of natural freeze tolerance in turtles. Copyright 2010 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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

  4. Rheological behaviour, freezing curve, and density of coffee solutions at temperatures close to freezing

    OpenAIRE

    Hernández Yáñez, Eduard; Moreno, Fabian Leonardo; Raventós Santamaria, Mercè; Santamaría, N.; Acosta, J.; Pirachican, Oscar; Torres, L.; Ruiz Pardo, Yolanda

    2015-01-01

    The physical properties of coffee solutions were determined for temperatures close to the freezing point. Rheological behaviour, freezing curve, density, and their relationship between coffee mass fraction and Brix degrees were determined for coffee mass fractions between 5 and 50% (wet basis) in the -6 to 20 degrees C temperature interval. Values of viscosity varied from 1.99 to 1037 mPa center dot s and values of density from 1000 to 1236 kg center dot m(-3). The freezing curve was generate...

  5. Possible impacts of climate change on freezing rain in south-central Canada using downscaled future climate scenarios

    Directory of Open Access Journals (Sweden)

    C. S. Cheng

    2007-01-01

    Full Text Available Freezing rain is a major atmospheric hazard in mid-latitude nations of the globe. Among all Canadian hydrometeorological hazards, freezing rain is associated with the highest damage costs per event. Using synoptic weather typing to identify the occurrence of freezing rain events, this study estimates changes in future freezing rain events under future climate scenarios for south-central Canada. Synoptic weather typing consists of principal components analysis, an average linkage clustering procedure (i.e., a hierarchical agglomerative cluster method, and discriminant function analysis (a nonhierarchical method. Meteorological data used in the analysis included hourly surface observations from 15 selected weather stations and six atmospheric levels of six-hourly National Centers for Environmental Prediction (NCEP upper-air reanalysis weather variables for the winter months (November–April of 1958/59–2000/01. A statistical downscaling method was used to downscale four general circulation model (GCM scenarios to the selected weather stations. Using downscaled scenarios, discriminant function analysis was used to project the occurrence of future weather types. The within-type frequency of future freezing rain events is assumed to be directly proportional to the change in frequency of future freezing rain-related weather types The results showed that with warming temperatures in a future climate, percentage increases in the occurrence of freezing rain events in the north of the study area are likely to be greater than those in the south. By the 2050s, freezing rain events for the three colder months (December–February could increase by about 85% (95% confidence interval – CI: ±13%, 60% (95% CI: ±9%, and 40% (95% CI: ±6% in northern Ontario, eastern Ontario (including Montreal, Quebec, and southern Ontario, respectively. The increase by the 2080s could be even greater: about 135% (95% CI: ±20%, 95% (95% CI: ±13%, and 45% (95% CI: ±9

  6. Effects of drying-wetting and freezing-thawing cycle on leachability of metallic elements in mine soils

    Science.gov (United States)

    Bang, H.; Kim, J.; Hyun, S.

    2016-12-01

    Mine leachate derived from contaminated mine sites with metallic elements can pose serious risks on human society and environment. Only labile fraction of metallic elements in mine soils is subject to leaching and movement by rainfall. Lability of metallic element in soil is a function of bond strengths between metal and soil surfaces, which is influenced by environmental condition (e.g., rainfall intensity, duration, temperature, etc.) The purpose of this study was to elucidate the effects of various climate conditions on the leaching patterns and lability of metallic elements in mine soils. To do this, two mine soils were sampled from two abandoned mine sites located in Korea. Leaching test were conducted using batch decant-refill method. Various climatic conditions were employed in leaching test such as (1) oven drying (40oC) - wetting cycles, (2) air drying (20oC) - wetting cycle, and (3) freezing (-40oC) - thawing cycles. Duration of drying and freezing were varied from 4 days to 2 weeks. Concentration of metallic elements, pH, Eh and concentration of dissolved iron and sulfate in leachate from each leaching process was measured. To identify the changes of labile fraction in mine soils after each of drying or freezing period, sequential extraction procedure (five fraction) was used to compare labile fraction (i.e., F1 + F2) of metallic elements. The concentration of metallic elements in mine leachate was increased after drying and freezing procedure. The amounts of released metallic element from mine soils was changed depending on their drying or freezing period. In addition, labile fraction of metallic elements in soil was also changed after drying and freezing. The changes in labile fraction after drying and freezing might be due to the increased soil surface area by pore water volume expansion. Further study is therefore needed to evaluate the impact of altered physical properties of soils such as hydration of soil surface area and shrinking by drying and

  7. An atomic force microscopy study on the transition from mushrooms to octopus surface ''micelles'' by changing the solvent quality

    NARCIS (Netherlands)

    Stamouli, A.; Pelletier, E.; Koutsos, V; van der Vegte, E.W.; Hadziioannou, G

    1996-01-01

    Atomic force microscopy (AFM) is used to study the behavior of a diblock copolymer onto a solid surface while the solvent quality is changed. In a first step, the copolymer poly(2-vinylpyridine)/polystyrene (P2VP/PS) is adsorbed onto mica from a selective solvent (the PS block is well solvated and

  8. Fuel Pellets from Wheat Straw: The Effect of Lignin Glass Transition and Surface Waxes on Pelletizing Properties

    Science.gov (United States)

    Wolfgang Stelte; Craig Clemons; Jens K. Holm; Jesper Ahrenfeldt; Ulrik B. Henriksen; Anand R. Sanadi

    2012-01-01

    The utilization of wheat straw as a renewable energy resource is limited due to its low bulk density. Pelletizing wheat straw into fuel pellets of high density increases its handling properties but is more challenging compared to pelletizing wood biomass. Straw has a lower lignin content and a high concentration of hydrophobic waxes on its outer surface that may limit...

  9. ECO Update / Groundwater Foum Issue Paper: Evaluating Ground-Water/Surface-Water Transition Zones in Ecological Risk Assessments

    Science.gov (United States)

    This ECO Update builds on the standard approach to ERA (U.S. EPA 1997), by providing a framework for incorporating groundwater/surface-water (GW/SW) interactions into existing ERAs (see U.S. EPA 1997 and 2001a for an introduction to ecological risk....

  10. Surface mobility and structural transitions of poly(n-alkyl methacrylates) probed by dynamic contact angle measurements

    NARCIS (Netherlands)

    van Damme, H.S.; Hogt, A.H.; Feijen, Jan

    1986-01-01

    Dynamic contact angles and contact-angle hysteresis of a series of poly(n-alkyl methacrylates) (PAMA) were investigated using the Wilhelmy plate technique. The mobility of polymer surface chains, segments, and side groups affected the measured contact angles and their hysteresis. A model is

  11. Farinose flavonoids are associated with high freezing tolerance in fairy primrose (Primula malacoides) plants.

    Science.gov (United States)

    Isshiki, Ryutaro; Galis, Ivan; Tanakamaru, Shigemi

    2014-02-01

    The deposition of surface (farinose) flavonoids on aerial parts of some Primula species is a well-documented but poorly understood phenomenon. Here, we show that flavonoid deposition on the leaves and winter buds may contribute strongly to preventing freezing damage in these plants. The ice nucleation temperature of fairy primrose (Primula malacoides) leaves covered with natural flavone was approximately 6 °C lower compared to those that had their flavone artificially removed. Additionally, farinose flavonoids on the leaves reduced subsequent electrolyte leakage (EL) from the cells exposed to freezing temperatures. Interestingly, exogenous application of flavone at 4 mg/g fresh weight to P. malacoides leaves, which had the original flavone mechanically removed, restored freezing tolerance, and diminished EL from the cells to pretreatment values. Our results suggest that farinose flavonoids may function as mediators of freezing tolerance in P. malacoides, and exogenous application of flavone could be used to reduce freezing damage during sudden but predictable frost events in other plant species. © 2013 Institute of Botany, Chinese Academy of Sciences.

  12. Effect of Controlled Ice Nucleation on Stability of Lactate Dehydrogenase During Freeze-Drying.

    Science.gov (United States)

    Fang, Rui; Tanaka, Kazunari; Mudhivarthi, Vamsi; Bogner, Robin H; Pikal, Michael J

    2017-10-23

    Several controlled ice nucleation techniques have been developed to increase the efficiency of the freeze-drying process as well as to improve the quality of pharmaceutical products. Owing to the reduction in ice surface area, these techniques have the potential to reduce the degradation of proteins labile during freezing. The objective of this study was to evaluate the effect of ice nucleation temperature on the in-process stability of lactate dehydrogenase (LDH). LDH in potassium phosphate buffer was nucleated at -4°C, -8°C, and -12°C using ControLyo™ or allowed to nucleate spontaneously. Both the enzymatic activity and tetramer recovery after freeze-thawing linearly correlated with product ice nucleation temperature (n = 24). Controlled nucleation also significantly improved batch homogeneity as reflected by reduced inter-vial variation in activity and tetramer recovery. With the correlation established in the laboratory, the degradation of protein in manufacturing arising from ice nucleation temperature differences can be quantitatively predicted. The results show that controlled nucleation reduced the degradation of LDH during the freezing process, but this does not necessarily translate to vastly superior stability during the entire freeze-drying process. The capability of improving batch homogeneity provides potential advantages in scaling-up from lab to manufacturing scale. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  13. An improved model for nucleation-limited ice formation in living cells during freezing.

    Directory of Open Access Journals (Sweden)

    Jingru Yi

    Full Text Available Ice formation in living cells is a lethal event during freezing and its characterization is important to the development of optimal protocols for not only cryopreservation but also cryotherapy applications. Although the model for probability of ice formation (PIF in cells developed by Toner et al. has been widely used to predict nucleation-limited intracellular ice formation (IIF, our data of freezing Hela cells suggest that this model could give misleading prediction of PIF when the maximum PIF in cells during freezing is less than 1 (PIF ranges from 0 to 1. We introduce a new model to overcome this problem by incorporating a critical cell volume to modify the Toner's original model. We further reveal that this critical cell volume is dependent on the mechanisms of ice nucleation in cells during freezing, i.e., surface-catalyzed nucleation (SCN and volume-catalyzed nucleation (VCN. Taken together, the improved PIF model may be valuable for better understanding of the mechanisms of ice nucleation in cells during freezing and more accurate prediction of PIF for cryopreservation and cryotherapy applications.

  14. Effect of cation species on surface-induced phase transition observed for platinum complex anions in platinum electrodeposition using nanoporous silicon.

    Science.gov (United States)

    Koda, Ryo; Koyama, Akira; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Abe, Takeshi; Kitada, Atsushi; Murase, Kuniaki; Kinoshita, Masahiro

    2014-08-21

    In an earlier work [K. Fukami et al., J. Chem. Phys. 138, 094702 (2013)], we reported a transition phenomenon observed for platinum complex anions in our platinum electrodeposition experiment using nanoporous silicon. The pore wall surface of the silicon electrode was made hydrophobic by covering it with organic molecules. The anions are only weakly hydrated due to their large size and excluded from the bulk aqueous solution to the hydrophobic surface. When the anion concentration in the bulk was gradually increased, at a threshold the deposition behavior exhibited a sudden change, leading to drastic acceleration of the electrochemical deposition. It was shown that this change originates from a surface-induced phase transition: The space within a nanopore is abruptly filled with the second phase in which the anion concentration is orders of magnitude higher than that in the bulk. Here we examine how the platinum electrodeposition behavior is affected by the cation species coexisting with the anions. We compare the experimental results obtained using three different cation species: K(+), (CH3)4N(+), and (C2H5)4N(+). One of the cation species coexists with platinum complex anions [PtCl4](2-). It is shown that the threshold concentration, beyond which the electrochemical deposition within nanopores is drastically accelerated, is considerably dependent on the cation species. The threshold concentration becomes lower as the cation size increases. Our theoretical analysis suggests that not only the anions but also the cations are remarkably enriched in the second phase. The remarkable enrichment of the anions alone would give rise to the energetic instability due to electrostatic repulsive interactions among the anions. We argue that the result obtained cannot be elucidated by the prevailing view based on classical electrochemistry. It is necessitated to consult a statistical-mechanical theory of confined aqueous solutions using a molecular model for water.

  15. Fission Surface Power Systems (FSPS) Project Final Report for the Exploration Technology Development Program (ETDP): Fission Surface Power, Transition Face to Face

    Science.gov (United States)

    Palac, Donald T.

    2011-01-01

    The Fission Surface Power Systems Project became part of the ETDP on October 1, 2008. Its goal was to demonstrate fission power system technology readiness in an operationally relevant environment, while providing data on fission system characteristics pertinent to the use of a fission power system on planetary surfaces. During fiscal years 08 to 10, the FSPS project activities were dominated by hardware demonstrations of component technologies, to verify their readiness for inclusion in the fission surface power system. These Pathfinders demonstrated multi-kWe Stirling power conversion operating with heat delivered via liquid metal NaK, composite Ti/H2O heat pipe radiator panel operations at 400 K input water temperature, no-moving-part electromagnetic liquid metal pump operation with NaK at flight-like temperatures, and subscale performance of an electric resistance reactor simulator capable of reproducing characteristics of a nuclear reactor for the purpose of system-level testing, and a longer list of component technologies included in the attached report. Based on the successful conclusion of Pathfinder testing, work began in 2010 on design and development of the Technology Demonstration Unit (TDU), a full-scale 1/4 power system-level non-nuclear assembly of a reactor simulator, power conversion, heat rejection, instrumentation and controls, and power management and distribution. The TDU will be developed and fabricated during fiscal years 11 and 12, culminating in initial testing with water cooling replacing the heat rejection system in 2012, and complete testing of the full TDU by the end of 2014. Due to its importance for Mars exploration, potential applicability to missions preceding Mars missions, and readiness for an early system-level demonstration, the Enabling Technology Development and Demonstration program is currently planning to continue the project as the Fission Power Systems project, including emphasis on the TDU completion and testing.

  16. Leaf Area Influence on Surface Layer in a Deciduous Forest. Part 2; Detecting Leaf Area and Surface Resistance During Transition Seasons

    Science.gov (United States)

    Sakai, Ricardo K.; Fitzjarrald, David R.; Moore, Kathleen E.; Sicker, John W.; Munger, Willian J.; Goulden, Michael L.; Wofsy, Steven C.

    1996-01-01

    Temperate deciduous forest exhibit dramatic seasonal changes in surface exchange properties following on the seasonal changes in leaf area index. The canopy resistance to water vapor transport r(sub c) decreased abruptly at leaf emergence in each year but then also continued to decrease slowly during the remaining growing season due to slowly increasing LAI. Canopy resistance and PAR-albedo (albedo from photosynthetically active radiation) began to increase about one month before leaf fall with the diminishment of CO2 gradient above the canopy as well. At this time evaporation begun to be controlled as if the canopy were leafless.

  17. Nucleation Pathways For Freezing Of Two Grades Of Zirconium

    Science.gov (United States)

    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.

  18. Adaptive Control of Freeze-Form Extrusion Fabrication Processes (Preprint)

    National Research Council Canada - National Science Library

    Zhao, Xiyue; Landers, Robert G; Leu, Ming C

    2008-01-01

    Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication...

  19. Water vapor movement in freezing aggregate base materials.

    Science.gov (United States)

    2014-06-01

    The objectives of this research were to 1) measure the extent to which water vapor movement results in : water accumulation in freezing base materials; 2) evaluate the effect of soil stabilization on water vapor movement : in freezing base materials;...

  20. Canalization of freeze tolerance in an alpine grasshopper.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Influence of freezing temperatures prior to freeze-drying on viability of yeasts and lactic acid bacteria isolated from wine.

    Science.gov (United States)

    Polo, L; Mañes-Lázaro, R; Olmeda, I; Cruz-Pio, L E; Medina, Á; Ferrer, S; Pardo, I

    2017-06-01

    To determine the effect of three different freezing temperatures on post-freeze-drying survival rates of wine yeasts and lactic acid bacteria (LAB). To know if a similar freeze-drying protocol can be used for both micro-organisms. Cells from liquid culture media were recovered and concentrated in appropriate lyoprotectants. Aliquots of each strain were frozen at -20, -80 and -196°C before vacuum drying. Viable cell counts were done before freezing and after freeze-drying. Survival rates were calculated. Freezing temperatures differently affected yeast and bacteria survival. The highest survival rates were obtained at -20 and -80°C for yeasts, but at -196°C for LAB. Major differences in survival rates were recorded among freeze-dried yeasts, but were less drastic for LAB. Yeasts Pichia membranifaciens, Starmerella bacillaris and Metschnikowia pulcherrima, and LAB Lactobacillus paracasei, Pediococcus parvulus and Lactobacillus mali, were the most tolerant species to freeze-drying, regardless of freezing temperature. Yeast and LAB survival rates differed for each tested freezing temperature. For yeasts, -20°C ensured the highest post-freeze-drying viability and -196°C for LAB. Freezing temperature to freeze-dry cells is a crucial factor for ensuring good wine yeast and LAB survival. These results are important for appropriately preserving micro-organisms and for improving starter production processes. © 2017 The Society for Applied Microbiology.

  2. Improvement of dissolution property of poorly water-soluble drug by supercritical freeze granulation.

    Science.gov (United States)

    Sonoda, Ryoichi; Hara, Yuko; Iwasaki, Tomohiro; Watano, Satoru

    2009-10-01

    The dissolution property of the poorly water-soluble drug, flurbiprofen (FP) was improved by a novel supercritical freeze granulation using supercritical carbon dioxide. Supercritical freeze granulation was defined as a production method of the granulated substances by using the dry ice to generate intentionally for the rapid atomization of the supercritical carbon dioxide to the atmospheric pressure. This process utilized a rapid expansion of supercritical solutions (RESS) process with the mixture of the drug and lactose. In the supercritical freeze granulation, needle-like FP fine particles were obtained which adhered to the surface of lactose particles, which did not dissolve in supercritical carbon dioxide. The number of FP particles that adhered to the surface of particles decreased with an increase in the ratio of lactose added, leading to markedly improve the dissolution rate. This improvement was caused not only by the increase in the specific surface area but also the improvement of the dispersibility of FP in water. It is thus concluded that the supercritical freeze granulation is a useful technique to improve the dissolution property of the poorly water-soluble flurbiprofen.

  3. Aversive Life Events Enhance Human Freezing Responses

    NARCIS (Netherlands)

    Hagenaars, M.A.; Stins, J.F.; Roelofs, K.

    2012-01-01

    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

  4. Aversive life events enhance human freezing responses

    NARCIS (Netherlands)

    Hagenaars, M.A.; Stins, J.F.; Roelofs, K.

    2012-01-01

    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

  5. Anomalous freezing behavior of nanoscale liposomes

    DEFF Research Database (Denmark)

    Spangler, E. J.; Kumar, P. B. S.; Laradji, M.

    2012-01-01

    The effect of the finite size of one-component liposomes on their phase behavior is investigated via simulations of an implicit-solvent model of self-assembled lipid bilayers. We found that the high curvature of nanoscale liposomes has a significant effect on their freezing behavior. While...

  6. Device and method for determining freezing points

    Science.gov (United States)

    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).

  7. Liquid carbon: structure near the freezing line

    NARCIS (Netherlands)

    Ghiringhelli, L.M.; Los, J.H.; Meijer, E.J.; Fasolino, A.; Frenkel, D.

    2005-01-01

    We present a detailed analysis of the structure of liquid carbon near the freezing line. The results are obtained by molecular simulation using a recently developed state-of-the-art bond order potential. We find that along the melting line the liquid is predominantly threefold coordinated up to

  8. Theoretical prediction of 'optimal' freezing programmes

    NARCIS (Netherlands)

    Woelders, H.; Chaveiro, A.

    2004-01-01

    We have developed a quantitative description of the osmotic behaviour of cells during freezing without a presupposed value of the cooling rate. Instead, at all times the intracellular supercooling is maximised provided that it does not exceed a predetermined value 'p' (e.g., 2°C). This should

  9. Rehydration kinetics of freeze-dried carrots

    NARCIS (Netherlands)

    Vergeldt, F.J.; Dalen, van G.; Duijster, A.J.; Voda, A.; Khalloufi, S.; Vliet, van L.J.; As, van H.; Duynhoven, van J.P.M.; Sman, van der R.G.M.

    2014-01-01

    Rehydration kinetics by two modes of imbibition is studied in pieces of freeze-dried winter carrot, after different thermal pre-treatments. Water ingress at room temperature is measured in real time by in situ MRI and NMR relaxometry. Blanched samples rehydrate substantially faster compared to

  10. Susceptibility of blackberry flowers to freezing temperatures

    Science.gov (United States)

    Injury of tight buds, open flowers and green fruit often occur in fruit crops during spring frost events. In this study, freezing tolerance of ‘Triple Crown’ blackberry flowers at different reproductive stages of development (tight bud to green drupe) was determined using two methods. One method i...

  11. Scaling-Up Eutectic Freeze Crystallization

    NARCIS (Netherlands)

    Genceli, F.E.

    2008-01-01

    A novel crystallization technology, Eutectic Freeze Crystallization (EFC) has been investigated and further developed in this thesis work. EFC operates around the eutectic temperature and composition of aqueous solutions and can be used for recovery of (valuable) dissolved salts (and/or or acids)

  12. Managing damaging freeze events in Louisiana sugarcane

    Science.gov (United States)

    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...

  13. Analysis and Application of the Amorphous Properties in Freeze-Dried Foods

    Science.gov (United States)

    Kawai, Kiyoshi

    The dynamic properties of amorphous materials drastically change by the phase transition between glassy state and rubber state. Furthermore, the dynamic properties of amorphous materials in glassy state are affected by the thermal history such as processing and/or storage conditions. In this paper, effect of the glass transition of freeze-dried food systems on the storage stability was summarized. Moreover, analytical approaches of the amorphous properties for glassy products with enthalpy relaxation measurements by using differential scanning calorimetry were presented and its application to food industry was proposed.

  14. Formation of stable submicron peptide or protein particles by thin film freezing

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Keith P.; Engstrom, Joshua; Williams, III, Robert O.

    2017-04-18

    The present invention includes compositions and methods for preparing micron-sized or submicron-sized particles by dissolving a water soluble effective ingredient in one or more solvents; spraying or dripping droplets solvent such that the effective ingredient is exposed to a vapor-liquid interface of less than 50, 100, 150, 200, 250, 200, 400 or 500 cm.sup.-1 area/volume to, e.g., increase protein stability; and contacting the droplet with a freezing surface that has a temperature differential of at least 30.degree. C. between the droplet and the surface, wherein the surface freezes the droplet into a thin film with a thickness of less than 500 micrometers and a surface area to volume between 25 to 500 cm.sup.-1.

  15. Antifreeze proteins enable plants to survive in freezing conditions

    Indian Academy of Sciences (India)

    2014-10-20

    Oct 20, 2014 ... ence in freezing and melting points, which is known as thermal hysteresis. Pure water freezes at 0°C at 1 atm; however, due to the presence of various solutes, cell sap freezes at −3°C to −4°C. In the presence of AFPs, the freezing point of cell sap is further decreased, thus avoiding ice formation in plants to ...

  16. Freezing and thawing of aqueous solutions in emulsions

    Science.gov (United States)

    Hauptmann, Astrid; Handle, Karl; Hölzl, Georg; Loerting, Thomas

    2016-04-01

    The freezing behaviour of aqueous solutions in different emulsions is investigated by analytical methods such as differential scanning calorimetry and optical cryomicroscopy. We show that freezing temperature, freeze concentration and correspondingly cold-crystallization and melting change depending on the properties of the surrounding oil and emulsifier, size distribution of emulsified droplets and the parameters of emulsification. Relevance to freezing of cloud droplets is discussed.

  17. Computational Fluid Dynamics Analysis of Freeze Drying Process and Equipment

    OpenAIRE

    Varma, Nikhil P.

    2014-01-01

    Freeze drying is an important, but expensive, inefficient and time consuming process in the pharmaceutical, chemical and food processing industries. Computational techniques could be a very effective tool in predictive design and analysis of both freeze drying process and equipment. This work is an attempt at using Computational Fluid Dynamics(CFD) and numerical simulations as a tool for freeze drying process and equipment design. Pressure control is critical in freeze dryers, keeping in v...

  18. Catalysis in the Diels-Alder Cycloaddition of Biomass-Derived Furan and Methyl Acrylate by Transition Metal Oxide Surfaces.

    Science.gov (United States)

    Salavati-Fard, Taha; Jenness, Glen; Caratzoulas, Stavros; Doren, Douglas

    Using computational methods, the catalytic effects of oxide surfaces on the Diels-Alder reaction between biomass-derived furan and methyl acrylate are investigated. The cycloadduct can be dehydrated later to produce methyl benzoic which is an important step toward benzoic acid production. Different systems such as clean, partially hydroxylated and fully hydroxylated ZrO2 are considered. The Langmuir and Eley-Rideal mechanisms are studied, as well. Our calculations show that the oxide surfaces catalyze the reaction significantly through the interaction of metal sites with the electron-poor reactant. The calculations are interpreted by making use of the total and projected electronic density of states and band structure of the catalyst. This material is based on work supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001004.

  19. Nanomaterials for efficiently lowering the freezing point of anti-freeze coolants.

    Science.gov (United States)

    Hong, Haiping; Zheng, Yingsong; Roy, Walter

    2007-09-01

    In this paper, we report, for the first time, the effect of the lowered freezing point in a 50% water/50% anti-freeze coolant (PAC) or 50% water/50% ethylene glycol (EG) solution by the addition of carbon nanotubes and other particles. The experimental results indicated that the nano materials are much more efficient (hundreds fold) in lowering the freezing point than the regular ionic materials (e.g., NaCl). The possible explanation for this interesting phenomenon is the colligative property of fluid and relative small size of nano material. It is quite certain that the carbon nanotubes and metal oxide nano particles could be a wonderful candidate for the nano coolant application because they could not only increase the thermal conductivity, but also efficiently lower the freezing point of traditional coolants.

  20. Freeze-drying process design by manometric temperature measurement: design of a smart freeze-dryer.

    Science.gov (United States)

    Tang, Xiaolin Charlie; Nail, Steven L; Pikal, Michael J

    2005-04-01

    To develop a procedure based on manometric temperature measurement (MTM) and an expert system for good practices in freeze drying that will allow development of an optimized freeze-drying process during a single laboratory freeze-drying experiment. Freeze drying was performed with a FTS Dura-Stop/Dura-Top freeze dryer with the manometric temperature measurement software installed. Five percent solutions of glycine, sucrose, or mannitol with 2 ml to 4 ml fill in 5 ml vials were used, with all vials loaded on one shelf. Details of freezing, optimization of chamber pressure, target product temperature, and some aspects of secondary drying are determined by the expert system algorithms. MTM measurements were used to select the optimum shelf temperature, to determine drying end points, and to evaluate residual moisture content in real-time. MTM measurements were made at 1 hour or half-hour intervals during primary drying and secondary drying, with a data collection frequency of 4 points per second. The improved MTM equations were fit to pressure-time data generated by the MTM procedure using Microcal Origin software to obtain product temperature and dry layer resistance. Using heat and mass transfer theory, the MTM results were used to evaluate mass and heat transfer rates and to estimate the shelf temperature required to maintain the target product temperature. MTM product dry layer resistance is accurate until about two-thirds of total primary drying time is over, and the MTM product temperature is normally accurate almost to the end of primary drying provided that effective thermal shielding is used in the freeze-drying process. The primary drying times can be accurately estimated from mass transfer rates calculated very early in the run, and we find the target product temperature can be achieved and maintained with only a few adjustments of shelf temperature. The freeze-dryer overload conditions can be estimated by calculation of heat/mass flow at the target product

  1. Potential weathering by freeze-thaw action in alpine rocks in the European Alps during a nine year monitoring period

    Science.gov (United States)

    Kellerer-Pirklbauer, Andreas

    2017-11-01

    A quantification of rock weathering by freeze-thaw processes in alpine rocks requires at least rock temperature data in high temporal resolution, in high quality, and over a sufficient period of time. In this study up to nine years of rock temperature data (2006-2015) from eleven rock monitoring sites in two of the highest mountain ranges of Austria were analyzed. Data were recorded at a half-hourly or hourly logging interval and at rock depths of 3, 10, and 30-40 cm. These data have been used to quantify mean conditions, ranges, and relationships of the potential near-surface weathering by freeze-thaw action considering volumetric-expansion of ice and ice segregation. For the former, freeze-thaw cycles and effective freeze-thaw cycles for frost shattering have been considered. For the latter, the intensity and duration of freezing events as well as time within the 'frost cracking window' have been analyzed. Results show that the eleven sites are in rather extreme topoclimatic positions and hence represent some of the highest and coolest parts of Austria and therefore the Eastern Alps. Only four sites are presumably affected by permafrost. Most sites are influenced by a long-lasting seasonal snow cover. Freeze-thaw cycles and effective freeze-thaw cycles for frost shattering are mainly affecting the near-surface and are unimportant at few tens of centimeters below the rock surface. The lowest temperatures during freezing events and the shortest freezing events have been quantified at all eleven monitoring sites very close to the surface. The time within the frost cracking window decreases in most cases from the rock surface inwards apart from very cold years/sites with very low temperatures close to the surface. As shown by this study and predicted climate change scenarios, assumed warmer rock temperature conditions in the future at alpine rock walls in Austria will lead to less severe freezing events and to shorter time periods within the frost-cracking window

  2. Tandem high-pressure freezing and quick freeze substitution of plant tissues for transmission electron microscopy.

    Science.gov (United States)

    Bobik, Krzysztof; Dunlap, John R; Burch-Smith, Tessa M

    2014-10-13

    Since the 1940s transmission electron microscopy (TEM) has been providing biologists with ultra-high resolution images of biological materials. Yet, because of laborious and time-consuming protocols that also demand experience in preparation of artifact-free samples, TEM is not considered a user-friendly technique. Traditional sample preparation for TEM used chemical fixatives to preserve cellular structures. High-pressure freezing is the cryofixation of biological samples under high pressures to produce very fast cooling rates, thereby restricting ice formation, which is detrimental to the integrity of cellular ultrastructure. High-pressure freezing and freeze substitution are currently the methods of choice for producing the highest quality morphology in resin sections for TEM. These methods minimize the artifacts normally associated with conventional processing for TEM of thin sections. After cryofixation the frozen water in the sample is replaced with liquid organic solvent at low temperatures, a process called freeze substitution. Freeze substitution is typically carried out over several days in dedicated, costly equipment. A recent innovation allows the process to be completed in three hours, instead of the usual two days. This is typically followed by several more days of sample preparation that includes infiltration and embedding in epoxy resins before sectioning. Here we present a protocol combining high-pressure freezing and quick freeze substitution that enables plant sample fixation to be accomplished within hours. The protocol can readily be adapted for working with other tissues or organisms. Plant tissues are of special concern because of the presence of aerated spaces and water-filled vacuoles that impede ice-free freezing of water. In addition, the process of chemical fixation is especially long in plants due to cell walls impeding the penetration of the chemicals to deep within the tissues. Plant tissues are therefore particularly challenging, but

  3. Characterization and endocytic internalization of Epith-2 cell surface glycoprotein during the epithelial-to-mesenchymal transition in sea urchin embryos

    Directory of Open Access Journals (Sweden)

    Norio eWakayama

    2013-08-01

    Full Text Available The epithelial cells of the sea urchin Hemicentrotus pulcherrimus embryo express an Epith-2, uncharacterized glycoprotein, on the lateral surface. Here, we describe internalization of Epith-2 during mesenchyme formation through the epithelial-to-mesenchymal transition (EMT. Epith-2 was first expressed on the entire egg surface soon after fertilization and on the blastomeres until the 4-cell stage, but was localized to the lateral surface of epithelial cells at and after the 16-cell stage throughout the later developmental period. However, primary (PMC and secondary mesenchyme cells (SMC that ingress by EMT lost Epith-2 from their cell surface by endocytosis during dissociation from the epithelium, which was associated with the appearance of cytoplasmic Epith-2 dots. The cytoplasmic Epith-2 retained a similar relative molecular mass to that of the cell surface immediately after ingression through the early period of the spreading to single cells. Then, Epith-2 was completely lost from the cytoplasm. Tyrosine residues of Epith-2 were phosphorylated. The endocytic retraction of Epith-2 was inhibited by herbimycin A (HA, a protein tyrosine kinase (PTK inhibitor, and suramin, a growth factor receptor (GFR inhibitor, suggesting the involvement of the GFR/PTK (GP signaling pathway. These two GP inhibitors also inhibited PMC and SMC spreading to individual cells after ingression, but the dissociation of PMC and SMC from the epithelium was not inhibited. In suramin-treated embryos, dissociated mesenchyme cells migrated partially by retaining their epithelial morphology. In HA-treated embryos, no mesenchyme cells migrated. Thus, the EMT occurs in relation to internalization of Epith-2 from presumptive PMC and SMC.

  4. Early Bone Formation around Immediately Loaded Transitional Implants Inserted in the Human Posterior Maxilla: The Effects of Fixture Design and Surface

    Directory of Open Access Journals (Sweden)

    Carlo Mangano

    2017-01-01

    Full Text Available Aim. To evaluate the effects of fixture design and surface on the early bone formation around immediately loaded implants inserted in the human posterior maxilla. Materials and Methods. Ten totally edentulous subjects received two transitional implants: one tapered implant with knife-edge threads/nanostructured calcium-incorporated surface (test: Anyridge®, Megagen, Gyeongbuk, South Korea and one cylindrical implant with self-tapping threads/sandblasted surface (control: EZPlus®, Megagen. The implants were placed according to a split-mouth design and immediately loaded to support an interim complete denture; after 8 weeks, they were removed for histologic/histomorphometric analysis. The bone-to-implant contact (BIC% and the bone density (BD% were calculated. The Wilcoxon test was used to evaluate the differences. Results. With test implants, a mean BIC% and BD% of 35.9 (±9.1 and 31.8 (±7.5 were found. With control implants, a mean BIC% and BD% of 29.9 (±7.6 and 32.5 (±3.9 were found. The mean BIC% was higher with test implants, but this difference was not significant (p=0.16. Similar BD% were found in the two groups (p=0.9. Conclusions. In the posterior maxilla, under immediate loading conditions, implants with a knife-edge thread design/nanostructured calcium-incorporated surface seem to increase the peri-implant endosseous healing properties, when compared to implants with self-tapping thread design/sandblasted surface.

  5. Early Bone Formation around Immediately Loaded Transitional Implants Inserted in the Human Posterior Maxilla: The Effects of Fixture Design and Surface

    Science.gov (United States)

    Pires, Jefferson Trabach; Luongo, Giuseppe; Piattelli, Adriano

    2017-01-01

    Aim. To evaluate the effects of fixture design and surface on the early bone formation around immediately loaded implants inserted in the human posterior maxilla. Materials and Methods. Ten totally edentulous subjects received two transitional implants: one tapered implant with knife-edge threads/nanostructured calcium-incorporated surface (test: Anyridge®, Megagen, Gyeongbuk, South Korea) and one cylindrical implant with self-tapping threads/sandblasted surface (control: EZPlus®, Megagen). The implants were placed according to a split-mouth design and immediately loaded to support an interim complete denture; after 8 weeks, they were removed for histologic/histomorphometric analysis. The bone-to-implant contact (BIC%) and the bone density (BD%) were calculated. The Wilcoxon test was used to evaluate the differences. Results. With test implants, a mean BIC% and BD% of 35.9 (±9.1) and 31.8 (±7.5) were found. With control implants, a mean BIC% and BD% of 29.9 (±7.6) and 32.5 (±3.9) were found. The mean BIC% was higher with test implants, but this difference was not significant (p = 0.16). Similar BD% were found in the two groups (p = 0.9). Conclusions. In the posterior maxilla, under immediate loading conditions, implants with a knife-edge thread design/nanostructured calcium-incorporated surface seem to increase the peri-implant endosseous healing properties, when compared to implants with self-tapping thread design/sandblasted surface. PMID:28280731

  6. Physical Stability of Freeze-Dried Isomalt Diastereomer Mixtures

    DEFF Research Database (Denmark)

    Koskinen, Anna-Kaisa; Fraser-Miller, Sara J.; Bøtker, Johan P.

    2016-01-01

    Purpose Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried. Methods Isomalt was freeze-dried in...

  7. 7 CFR 58.620 - Freezing and packaging rooms.

    Science.gov (United States)

    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 be...

  8. 7 CFR 929.11 - To can, freeze, or dehydrate.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false To can, freeze, or dehydrate. 929.11 Section 929.11... LONG ISLAND IN THE STATE OF NEW YORK Order Regulating Handling Definitions § 929.11 To can, freeze, or dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated...

  9. 40 CFR 52.1135 - Regulation for parking freeze.

    Science.gov (United States)

    2010-07-01

    ... 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 a...) parking on public streets. (6) Freeze means to maintain at all times after October 15, 1973, the total...

  10. 7 CFR 305.18 - Quick freeze treatment schedule.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 5 2010-01-01 2010-01-01 false Quick freeze treatment schedule. 305.18 Section 305.18 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS Quick Freeze Treatments § 305.18 Quick freeze...

  11. JSC Mars-1 Soil Moisture Characteristic and Soil Freezing Characteristic Curves for Modeling Bulk Vapor Flow and Soil Freezing

    Science.gov (United States)

    Dinwiddie, C. L.; Sizemore, H. G.

    2008-03-01

    A new JSC Mars-1 particle size distribution is used to establish soil moisture characteristic and soil freezing characteristic curves that are needed for modeling bulk (Darcy) vapor flow and soil freezing in the variably saturated subsurface of Mars.

  12. Transition between bulk and surface refractive index sensitivity of micro-cavity in-line Mach-Zehnder interferometer induced by thin film deposition.

    Science.gov (United States)

    Śmietana, Mateusz; Janik, Monika; Koba, Marcin; Bock, Wojtek J

    2017-10-16

    In this work we discuss the refractive index (RI) sensitivity of a micro-cavity in-line Mach-Zehnder interferometer in the form of a cylindrical hole (40-50 μm in diameter) fabricated in a standard single-mode optical fiber using a femtosecond laser. The surface of the micro-cavity was coated with up to 400 nm aluminum oxide thin film using the atomic layer deposition method. Next, the film was progressively chemically etched and the influence on changes in the RI of liquid in the micro-cavity was determined at different stages of the experiment, i.e., at different thicknesses of the film. An effect of transition between sensitivity to the film thickness (surface) and the RI of liquid in the cavity (bulk) is demonstrated for the first time. We have found that depending on the interferometer working conditions determined by thin film properties, the device can be used for investigation of phenomena taking place at the surface, such as in case of specific label-free biosensing applications, or for small-volume RI analysis as required in analytical chemistry.

  13. SLAPex Freeze/Thaw 2015: The First Dedicated Soil Freeze/Thaw Airborne Campaign

    Science.gov (United States)

    Kim, Edward; Wu, Albert; DeMarco, Eugenia; Powers, Jarrett; Berg, Aaron; Rowlandson, Tracy; Freeman, Jacqueline; Gottfried, Kurt; Toose, Peter; Roy, Alexandre; hide

    2016-01-01

    Soil freezing and thawing is an important process in the terrestrial water, energy, and carbon cycles, marking the change between two very different hydraulic, thermal, and biological regimes. NASA's Soil Moisture Active/Passive (SMAP) mission includes a binary freeze/thaw data product. While there have been ground-based remote sensing field measurements observing soil freeze/thaw at the point scale, and airborne campaigns that observed some frozen soil areas (e.g., BOREAS), the recently-completed SLAPex Freeze/Thaw (F/T) campaign is the first airborne campaign dedicated solely to observing frozen/thawed soil with both passive and active microwave sensors and dedicated ground truth, in order to enable detailed process-level exploration of the remote sensing signatures and in situ soil conditions. SLAPex F/T utilized the Scanning L-band Active/Passive (SLAP) instrument, an airborne simulator of SMAP developed at NASA's Goddard Space Flight Center, and was conducted near Winnipeg, Manitoba, Canada, in October/November, 2015. Future soil moisture missions are also expected to include soil freeze/thaw products, and the loss of the radar on SMAP means that airborne radar-radiometer observations like those that SLAP provides are unique assets for freeze/thaw algorithm development. This paper will present an overview of SLAPex F/T, including descriptions of the site, airborne and ground-based remote sensing, ground truth, as well as preliminary results.

  14. Stabilization of protein structure in freeze-dried amorphous organic acid buffer salts.

    Science.gov (United States)

    Izutsu, Ken-ichi; Kadoya, Saori; Yomota, Chikako; Kawanishi, Toru; Yonemochi, Etsuo; Terada, Katsuhide

    2009-11-01

    The purpose of this study was to elucidate the physical properties and protein-stabilizing effects of some pH-adjusting excipients (carboxylic acids and their sodium salts) in frozen solutions and in freeze-dried solids. Thermal and powder X-ray diffraction (XRD) analysis indicated a high propensity of sodium citrates to form glass-state amorphous solids upon freeze-drying. Some salts (e.g., sodium succinate) crystallized in the single-solute frozen solutions. FT-IR analysis of bovine serum albumin (BSA) and bovine immunoglobulin G (IgG) in the aqueous solutions and the freeze-dried solids showed that some glass-forming salts (e.g., monosodium citrate) protected the secondary structure from lyophilization-induced perturbation. Freeze-drying of BSA at different concentrations indicated retention of the secondary structure at similar monosodium citrate/protein concentration ratios, suggesting stabilization through direct interaction that substitute water molecules inevitable for the conformation integrity. The carboxylic acid salts should provide rigid hydrogen bonds and electrostatic interactions that raise the glass transition temperature of the amorphous solids and stabilize protein structure. The relevance of the structural stabilization to the protein formulation design was discussed.

  15. Foam-Mat Freeze-Drying of Bifidobacterium longum RO175: Viability and Refrigerated Storage Stability.

    Science.gov (United States)

    Izquierdo-López, Danilo; Goulet, Jacques; Ratti, Cristina

    2017-01-01

    Foaming as a pretreatment was used prior to freeze-drying of Bifidobacterium longum RO175 to investigate the potential acceleration of the drying rate and increase in microorganism viability after the process. A study on storage of foamed and nonfoamed freeze-dried products at 4 °C completed this study. B. longum RO175 in foamed medium could be freeze-dried in 1/7 to 1/4 of the time required for nonfoamed suspensions. In addition, foamed suspensions presented higher viability immediately after freeze-drying (13.6% compared to 12.81 % or 11.46%, depending on the cryoprotective media). Refrigerated storage led to a reduction in B. longum RO175 viability for all tested protective agents (foamed and nonfoamed). No correlation between glass transition temperature and stability of probiotic powders was observed during storage. In addition, lower viability after 56 d of storage was observed for foamed materials, probably due to foam porous structure and higher hygroscopicity, and oxygen presence and moisture pickup during storage. © 2016 Institute of Food Technologists®.

  16. The effects of freeze drying and freeze drying additives on the prothrombin time and the international sensitivity index.

    OpenAIRE

    Poller, L.; Keown, M; Shepherd, S A; Shiach, C R; Tabeart, S

    1999-01-01

    AIM: To determine whether freezing, freeze drying protective additives, or freeze drying of plasma samples from patients on coumarin treatment and from normal individuals affects prothrombin times or the international sensitivity index (ISI) calibration. METHODS: The effect of the addition of the protective additives singly and combined on the prothrombin time of coumarin samples and normal samples before and after freeze drying was observed using high and low ISI reference thromboplastins. I...

  17. Potential of satellite-based land emissivity estimates for the detection of high-latitude freeze and thaw states

    Science.gov (United States)

    Prakash, Satya; Norouzi, Hamid; Azarderakhsh, Marzi; Blake, Reginald; Khanbilvardi, Reza

    2017-03-01

    Reliable detection of freeze and thaw (FT) states is crucial for the terrestrial water cycle, biogeochemical transitions, carbon and methane feedback to the atmosphere, and for the surface energy budget and its associated impacts on the global climate system. This paper is novel in that for the first time a unique approach to examine the potential of passive microwave remotely sensed land emissivity and its added values of being free from the atmospheric effects and being sensitive to surface characteristics is being applied to the detection of FT states for latitudes north of 35°N. Since accurate characterizations of the soil state are highly dependent on land cover types, a novel threshold-based approach specific to different land cover types is proposed for daily FT detection from the use of 3 years (August 2012 to July 2015) of the Advanced Microwave Scanning Radiometer-2 land emissivity estimates. Ground-based soil temperature observations are used as reference to develop threshold values for FT states. Preliminary evaluation of the proposed approach with independent ground observations over Alaska for the year 2015 shows that the use of land emissivity estimates for high-latitude FT detection is promising.

  18. Cathepsin D serum and urine concentration in superficial and invasive transitional bladder cancer as determined by surface plasmon resonance imaging

    OpenAIRE

    GORODKIEWICZ, EWA; GUSZCZ, TOMASZ; ROSZKOWSKA-JAKIMIEC, WIESLAWA; KOZŁOWSKI, ROBERT

    2014-01-01

    Determination of cathepsin D (Cat D) concentration in serum and urine may be useful in the diagnosis of bladder cancer. The present study included 54 healthy patients and 68 patients with bladder cancer, confirmed by transurethral resection or cystectomy. Cat D concentration was determined using a surface plasmon resonance imaging biosensor. Cat D concentration in the serum of bladder cancer patients was within the range of 1.3–5.59 ng/ml, while for healthy donors it was within the range of 0...

  19. Formation of transition metal cluster adducts on the surface of single-walled carbon nanotubes: HRTEM studies

    KAUST Repository

    Kalinina, Irina V.

    2014-01-01

    We report the formation of chromium clusters on the outer walls of single-walled carbon nanotubes (SWNTs). The clusters were obtained by reacting purified SWNTs with chromium hexacarbonyl in dibutyl ether at 100°C. The functionalized SWNTs were characterized by thermogravimetic analysis, XPS, and high-resolution TEM. The curvature of the SWNTs and the high mobility of the chromium moieties on graphitic surfaces allow the growth of the metal clusters and we propose a mechanism for their formation. © 2014 Taylor and Francis Group, LLC.

  20. Freeze-drying of HESylated IFNα-2b: Effect of HESylation on storage stability in comparison to PEGylation.

    Science.gov (United States)

    Liebner, Robert; Bergmann, Sarah; Hey, Thomas; Winter, Gerhard; Besheer, Ahmed

    2015-11-10

    A comparison of lyophilized PEGylated and HESylated IFNα was carried out to investigate the influence of protein conjugation, lyoprotectants as well as storage temperature on protein stability. Results show that PEG tends to crystallize during freeze-drying, reducing protein stability upon storage. In contrast, HESylation(®) drastically improved the stability over PEGylation by remaining totally amorphous during lyophilization, with and without lyoprotectants while providing a high glass transition temperature of the freeze-dried cakes. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Surface sediments in the marsh-sandy land transitional area: sandification in the western Songnen Plain, China.

    Science.gov (United States)

    Yu, Xiaofei; Grace, Michael; Zou, Yuanchun; Yu, Xuefeng; Lu, Xianguo; Wang, Guoping

    2014-01-01

    The development of sandification process was studied, by monitoring the changes of sediment characteristics, at marsh-sandy land intersections in China's Songnen region. A series of sediment collection plates were deployed in the region; after one year, sediments in these plates were analyzed for changes of mass and chemical characteristics. The sediment flux and the sand content of the sediments decreased with the increasing longitudinal distance between the sampling site and the centre line of a sand dune. The mean sediment flux was 29 ± 14 kg m(-2) yr(-1) and 0.6 ± 0.3 kg m(-2) yr(-1) in the sandy land and marsh, respectively. Strong, positive correlations were found between the concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr, all of which were also negatively correlated with the sand content. The concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr in the marsh sediment samples were all significantly greater than the corresponding concentrations of the sandy land (pmarsh could be divided into three distinct zones. Sand expansion extended about 88 m into the marsh. The mean sand content in the sediments of the sandy land was 91% and then 64% in the marsh, which in turn was higher than that of marshes outside the influence of sandification, suggesting that the marsh in the marsh-sandy land transitional area has already undergone extensive sandification in the past. The study results provide information on the wetland's function of indicating and buffering the sandification process.

  2. Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

    Science.gov (United States)

    As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain, then progressively lose freezing tolerance. Exposing the plants to freeze-thaw cycles of -3/3°C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This stu...

  3. Freezing Tolerance of Bulb Scales of Lily Cultivars : Effects of Freezing and Storage Duration and Partial Dehydration

    NARCIS (Netherlands)

    Bonnier, Frans J.M.; Jansen, Ritsert C.; Tuyl, Jaap M. van

    1997-01-01

    Effects of freezing duration, previous storage duration of bulbs at -2 °C, and partial dehydration of scales on freezing tolerance of lily (Lilium hybrids) scales were studied for a series of cultivars. Freezing tolerance of scales was estimated by measuring ion leakage and recording scale bulblet

  4. The freezing and supercooling of garlic (Allium sativum L.)

    Energy Technology Data Exchange (ETDEWEB)

    James, Christian; Seignemartin, Violaine; James, Stephen J. [Food Refrigeration and Process Engineering Research Centre (FRPERC), University of Bristol, Churchill Building, Langford, Bristol BS40 5DU (United Kingdom)

    2009-03-15

    This work shows that peeled garlic cloves demonstrate significant supercooling during freezing under standard conditions and can be stored at temperatures well below their freezing point (-2.7 C) without freezing. The nucleation point or 'metastable limit temperature' (the point at which ice crystal nucleation is initiated) of peeled garlic cloves was found to be between -7.7 and -14.6 C. Peeled garlic cloves were stored under static air conditions at temperatures between -6 and -9 C for up to 69 h without freezing, and unpeeled whole garlic bulbs and cloves were stored for 1 week at -6 C without freezing. (author)

  5. Heat treatment induced phase transition and microstructural evolution in electron beam surface melted Nb-Si based alloys

    Science.gov (United States)

    Guo, Yueling; Jia, Lina; Kong, Bin; Peng, Hui; Zhang, Hu

    2017-11-01

    The hardness, phase and microstructural development of Nb-18Si-24Ti-2Cr-2Al (at.%) alloys processed by electron beam surface melting (EBSM) and subsequent heat treatments were investigated. The EBSM experiments were performed using an electron beam based 3D printing system. Results showed that Nbss and Nb3Si phases were obtained via EBSM with a significantly refined microstructure. The eutectoid reaction of Nb3Si → Nbss + αNb5Si3 was triggered by heat treatments (HT) at 1200 °C or 1450 °C for 5 h. The growth and the coarsening of αNb5Si3 grains were promoted with a higher HT temperature. The hardness of the EBSM alloy was remarkably reduced by HT.

  6. Insight into the description of van der Waals forces for benzene adsorption on transition metal (111) surfaces.

    Science.gov (United States)

    Carrasco, Javier; Liu, Wei; Michaelides, Angelos; Tkatchenko, Alexandre

    2014-02-28

    Exploring the role of van der Waals (vdW) forces on the adsorption of molecules on extended metal surfaces has become possible in recent years thanks to exciting developments in density functional theory (DFT). Among these newly developed vdW-inclusive methods, interatomic vdW approaches that account for the nonlocal screening within the bulk [V. G. Ruiz, W. Liu, E. Zojer, M. Scheffler, and A. Tkatchenko, Phys. Rev. Lett. 108, 146103 (2012)] and improved nonlocal functionals [J. Klimeš, D. R. Bowler, and A. Michaelides, J. Phys.: Condens. Matter 22, 022201 (2010)] have emerged as promising candidates to account efficiently and accurately for the lack of long-range vdW forces in most popular DFT exchange-correlation functionals. Here we have used these two approaches to compute benzene adsorption on a range of close-packed (111) surfaces upon which it either physisorbs (Cu, Ag, and Au) or chemisorbs (Rh, Pd, Ir, and Pt). We have thoroughly compared the performance between the two classes of vdW-inclusive methods and when available compared the results obtained with experimental data. By examining the computed adsorption energies, equilibrium distances, and binding curves we conclude that both methods allow for an accurate treatment of adsorption at equilibrium adsorbate-substrate distances. To this end, explicit inclusion of electrodynamic screening in the interatomic vdW scheme and optimized exchange functionals in the case of nonlocal vdW density functionals is mandatory. Nevertheless, some discrepancies are found between these two classes of methods at large adsorbate-substrate separations.

  7. Behaviour of polycyclic aromatic hydrocarbons (PAH) in soils under freeze-thaw cycles

    Science.gov (United States)

    Zschocke, Anne; Schönborn, Maike; Eschenbach, Annette

    2010-05-01

    The arctic region will be one of the most affected regions by climate change due to the predicted temperature rise. As a result of anthropogenic actions as mining, exploration and refining as well as atmospheric transport pollutions can be found in arctic soils. Therefore questions on the behaviour of organic contaminants in permafrost influenced soils are of high relevance. First investigations showed that permafrost can act as a semi-permeable layer for PAH (Curtosi et al., 2007). Therefore it can be assumed that global warming could result in a mobilization of PAH in these permafrost influenced soils. On the other hand a low but detectable mineralization of organic hydrocarbons by microorganisms under repeated freeze-thaw cycles was analysed (Börresen et al. 2007, Eschenbach et al. 2000). In this study the behaviour and distribution of PAH under freezing and periodically freezing and thawing were investigated in laboratory column experiments with spiked soil materials. Two soil materials which are typical for artic regions, a organic matter containing melt water sand and a well decomposed peat, were homogeneously spiked with a composite of a crude oil and the PAH anthracene and benzo(a)pyrene. After 14days preincubation time the soil material was filled in the laboratory columns (40cm high and 10 cm in diameter). Based on studies by Chuvilin et al. (2001) the impact of freezing of the upper third of the column from the surface downwards was examined. The impact of freezing was tested in two different approaches the first one with a single freezing step and the second one with a fourfold repeated cycle of freezing and thawing which takes about 6 or 7 days each. The experimental design and very first results will be shown and discussed. In some experiments with the peat a higher concentration of anthracene and benzo(a)pyrene could be detected below the freezing front in the unfrozen part of the column. Whereas the concentration of PAH had slightly decreased in

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

    Science.gov (United States)

    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.

  9. The effect of undissolved air on isochoric freezing.

    Science.gov (United States)

    Perez, Pedro A; Preciado, Jessica; Carlson, Gary; DeLonzor, Russ; Rubinsky, Boris

    2016-06-01

    This study evaluates the effect of undissolved air on isochoric freezing of aqueous solutions. Isochoric freezing is concerned with freezing in a constant volume thermodynamic system. A possible advantage of the process is that it substantially reduces the percentage of ice in the system at every subzero temperature, relative to atmospheric freezing. At the pressures generated by isochoric freezing, or high pressure isobaric freezing, air cannot be considered an incompressible substance and the presence of undissolved air substantially increases the amount of ice that forms at any subfreezing temperature. This effect is measurable at air volumes as low as 1%. Therefore eliminating the undissolved air, or any separate gaseous phase, from the system is essential for retaining the properties of isochoric freezing. Copyright © 2016. Published by Elsevier Inc.

  10. Rheological properties and bread quality of frozen sweet dough with added xanthan and different freezing rate.

    Science.gov (United States)

    Akbarian, Mina; Koocheki, Arash; Mohebbi, Mohebbat; Milani, Elnaz

    2016-10-01

    In this paper the effects of frozen storage time, xanthan gum and rate of freezing on frozen sweet dough properties and unfermented bread quality was investigated. Results revealed that the water holding capacity, WHC, K1 (stress decay rate) and K2 (residual stress at the end of the stress relaxation experiment) values of frozen dough decreased with increasing frozen storage time and decreasing freezing rate; while the lowest values for these parameters were obtained for samples without xanthan gum. The amount of unfreezable water increased and freezable water decreased with addition of xanthan gum. Glass transition temperature for fresh or frozen sweet were around -37 and -39 °C, respectively. Addition of xanthan gum increased the glass transition temperature of fresh and fozen sweet dough. Firmness and gumminess of sweet bread increased during frozen storage which led to lower specific volume of frozen sweet bread. Increasing freezing rate and addition of xanthan gum to dough formulation improved the texture and specific volume of the final bread.

  11. Solution of the problem of pipes freezing with account for external heat exchange

    Directory of Open Access Journals (Sweden)

    Samarin Oleg Dmitrievich

    2015-01-01

    Full Text Available The author considered the problem statement on the pipes freezing in emergency regimes of building engineering systems and external pipe nets using liquid water as working fluid under boundary conditions of the 3rd type. This problem is a high-priority task now because of actualization of building standards in Russian Federation and because of the increasing requirements to safety and security of heat supply. That’s why it is very important to find a simple but accurate enough dependence for the freezing time in pipe nets. The system of differential and algebraic equations of external heat exchange and internal heat transfer with account for heat ingress from hydraulic friction at water flow and Stephan’s condition on the freezing front is presented. The analytical solution of the given system is obtained as a quadrature for the dependence of the current coordinate of the freezing front. The results of numerical calculation of the corresponding integral are shown and their comparison with the former author’s researches concerning the solution of the considered problem at the boundary conditions of the 1st type is conducted. It is shown that the account of intensity of external heat exchange causes retarding of freezing because of adding thermal resistance on the external surface of the pipe. The former author’s conclusion on the existence of the ultimate water velocity, when freezing doesn’t take place, is verified. The area of use of the presented dependence is found. The obtained model contains is easy to use in engineering practice, especially during preliminary calculations. The presentation is illustrated with numerical and graphical examples.

  12. Investigation of Freeze and Thaw Cycles of a Gas-Charged Heat Pipe

    Science.gov (United States)

    Ku, Jentung; Ottenstein, Laura; Krimchansky, Alexander

    2012-01-01

    The traditional constant conductance heat pipes (CCHPs) currently used on most spacecraft run the risk of bursting the pipe when the working fluid is frozen and later thawed. One method to avoid pipe bursting is to use a gas-charged heat pipe (GCHP) that can sustain repeated freeze/thaw cycles. The construction of the GCHP is similar to that of the traditional CCHP except that a small amount of non-condensable gas (NCG) is introduced and a small length is added to the CCHP condenser to serve as the NCG reservoir. During the normal operation, the NCG is mostly confined to the reservoir, and the GCHP functions as a passive variable conductance heat pipe (VCHP). When the liquid begins to freeze in the condenser section, the NCG will expand to fill the central core of the heat pipe, and ice will be formed only in the grooves located on the inner surface of the heat pipe in a controlled fashion. The ice will not bridge the diameter of the heat pipe, thus avoiding the risk of pipe bursting during freeze/thaw cycles. A GCHP using ammonia as the working fluid was fabricated and then tested inside a thermal vacuum chamber. The GCHP demonstrated a heat transport capability of more than 200W at 298K as designed. Twenty-seven freeze/thaw cycles were conducted under various conditions where the evaporator temperature ranged from 163K to 253K and the condenser/reservoir temperatures ranged from 123K to 173K. In all tests, the GCHP restarted without any problem with heat loads between 10W and 100W. No performance degradation was noticed after 27 freeze/thaw cycles. The ability of the GCHP to sustain repeated freeze/thaw cycles was thus successfully demonstrated.

  13. High ice nucleation activity located in blueberry stem bark is linked to primary freeze initiation and adaptive freezing behaviour of the bark

    Science.gov (United States)

    Kishimoto, Tadashi; Yamazaki, Hideyuki; Saruwatari, Atsushi; Murakawa, Hiroki; Sekozawa, Yoshihiko; Kuchitsu, Kazuyuki; Price, William S.; Ishikawa, Masaya

    2014-01-01

    Controlled ice nucleation is an important mechanism in cold-hardy plant tissues for avoiding excessive supercooling of the protoplasm, for inducing extracellular freezing and/or for accommodating ice crystals in specific tissues. To understand its nature, it is necessary to characterize the ice nucleation activity (INA), defined as the ability of a tissue to induce heterogeneous ice nucleation. Few studies have addressed the precise localization of INA in wintering plant tissues in respect of its function. For this purpose, we recently revised a test tube INA assay and examined INA in various tissues of over 600 species. Extremely high levels of INA (−1 to −4 °C) in two wintering blueberry cultivars of contrasting freezing tolerance were found. Their INA was much greater than in other cold-hardy species and was found to be evenly distributed along the stems of the current year's growth. Concentrations of active ice nuclei in the stem were estimated from quantitative analyses. Stem INA was localized mainly in the bark while the xylem and pith had much lower INA. Bark INA was located mostly in the cell wall fraction (cell walls and intercellular structural components). Intracellular fractions had much less INA. Some cultivar differences were identified. The results corresponded closely with the intrinsic freezing behaviour (extracellular freezing) of the bark, icicle accumulation in the bark and initial ice nucleation in the stem under dry surface conditions. Stem INA was resistant to various antimicrobial treatments. These properties and specific localization imply that high INA in blueberry stems is of intrinsic origin and contributes to the spontaneous initiation of freezing in extracellular spaces of the bark by acting as a subfreezing temperature sensor. PMID:25082142

  14. High ice nucleation activity located in blueberry stem bark is linked to primary freeze initiation and adaptive freezing behaviour of the bark.

    Science.gov (United States)

    Kishimoto, Tadashi; Yamazaki, Hideyuki; Saruwatari, Atsushi; Murakawa, Hiroki; Sekozawa, Yoshihiko; Kuchitsu, Kazuyuki; Price, William S; Ishikawa, Masaya

    2014-07-31

    Controlled ice nucleation is an important mechanism in cold-hardy plant tissues for avoiding excessive supercooling of the protoplasm, for inducing extracellular freezing and/or for accommodating ice crystals in specific tissues. To understand its nature, it is necessary to characterize the ice nucleation activity (INA), defined as the ability of a tissue to induce heterogeneous ice nucleation. Few studies have addressed the precise localization of INA in wintering plant tissues in respect of its function. For this purpose, we recently revised a test tube INA assay and examined INA in various tissues of over 600 species. Extremely high levels of INA (-1 to -4 °C) in two wintering blueberry cultivars of contrasting freezing tolerance were found. Their INA was much greater than in other cold-hardy species and was found to be evenly distributed along the stems of the current year's growth. Concentrations of active ice nuclei in the stem were estimated from quantitative analyses. Stem INA was localized mainly in the bark while the xylem and pith had much lower INA. Bark INA was located mostly in the cell wall fraction (cell walls and intercellular structural components). Intracellular fractions had much less INA. Some cultivar differences were identified. The results corresponded closely with the intrinsic freezing behaviour (extracellular freezing) of the bark, icicle accumulation in the bark and initial ice nucleation in the stem under dry surface conditions. Stem INA was resistant to various antimicrobial treatments. These properties and specific localization imply that high INA in blueberry stems is of intrinsic origin and contributes to the spontaneous initiation of freezing in extracellular spaces of the bark by acting as a subfreezing temperature sensor. Published by Oxford University Press on behalf of the Annals of Botany Company.

  15. Formulation and stability of freeze-dried proteins: effects of moisture and oxygen on the stability of freeze-dried formulations of human growth hormone.

    Science.gov (United States)

    Pikal, M J; Dellerman, K; Roy, M L

    1992-01-01

    This research presents the results of a series of stability studies on freeze-dried formulations of human growth hormone (hGH). Chemical decomposition via methionine oxidation and asparagine deamidation as well as irreversible aggregation are characterized by HPLC. Water sorption isotherms, DSC thermograms, and pulsed proton NMR data are also obtained. No glass transition temperatures are observed in the temperature range of the stability studies. The pulsed NMR data suggest onset of greater mobility in the solid at a water content slightly higher than BET "monolayer" level. Stability of freeze-dried solids at 25 degrees C and 40 degrees C is studied as a function of residual moisture and exposure to oxygen. Formulations with and without a glycine/mannitol excipient system are studied. Significant levels of chemical decomposition and irreversible aggregation occur under most conditions with the effects of residual water content and "headspace oxygen" strongly dependent on the formulation. At low water content with minimal oxygen in the vial headspace, the glycine/mannitol formulation yields optimum stability. However, for either high water content or high oxygen content in the vial, stability of hGH without excipients is superior. The qualitative effect of residual moisture on stability depends on the temperature of the stability study. Generally, the stability of a sample adjusted to a given water content by desorption (during freeze-drying) is identical to the stability of a sample prepared by sorption of water on to a previously highly dried sample.

  16. Fermi-Surface Topological Phase Transition and Horizontal Order-Parameter Nodes in CaFe2As2 Under Pressure

    Science.gov (United States)

    Gonnelli, R. S.; Daghero, D.; Tortello, M.; Ummarino, G. A.; Bukowski, Z.; Karpinski, J.; Reuvekamp, P. G.; Kremer, R. K.; Profeta, G.; Suzuki, K.; Kuroki, K.

    2016-05-01

    Iron-based compounds (IBS) display a surprising variety of superconducting properties that seems to arise from the strong sensitivity of these systems to tiny details of the lattice structure. In this respect, systems that become superconducting under pressure, like CaFe2As2, are of particular interest. Here we report on the first directional point-contact Andreev-reflection spectroscopy (PCARS) measurements on CaFe2As2 crystals under quasi-hydrostatic pressure, and on the interpretation of the results using a 3D model for Andreev reflection combined with ab-initio calculations of the Fermi surface (within the density functional theory) and of the order parameter symmetry (within a random-phase-approximation approach in a ten-orbital model). The almost perfect agreement between PCARS results at different pressures and theoretical predictions highlights the intimate connection between the changes in the lattice structure, a topological transition in the holelike Fermi surface sheet, and the emergence on the same sheet of an order parameter with a horizontal node line.

  17. Microwave Augmented Freeze-Drying - Four Studies

    Science.gov (United States)

    1994-04-01

    F.J. 1G76. Pigments in "Principles of Food Science". O.R. Fennema, ed., Marcel Dekkar, Inc., New York. Datta, A.K. and Hu, W. 1992. Optimization of...and Wilke, C.R 1967. The relationship between transport properties and rates of freeze-drying of poultry meat. AIChE J. 13:428. Slater, L.E. 1975

  18. Effective freezing rate for semen cryopreservation in endangered Mediterranean brown trout (Salmo trutta macrostigma) inhabiting the Biferno river (South Italy).

    Science.gov (United States)

    Iaffaldano, Nicolaia; Di Iorio, Michele; Manchisi, Angelo; Esposito, Stefano; Gibertoni, Pier Paolo

    2016-10-01

    This study was designed to determine: (i) the in vitro effects of different freezing rates on post-thaw semen quality of Mediterranean brown trout (Salmo trutta macrostigma) from the Biferno river; and (ii) the in vivo fertilization and hatching percentage of freezing rate giving rise to the best post-thaw semen quality. Pooled semen samples were diluted 1:3 (v:v) in a freezing extender composed of 300 mM glucose, 10% egg yolk and 10% dimethyl sulfoxide (DMSO). The extended semen was packaged in 0.25 ml plastic straws and frozen at different heights above the liquid nitrogen surface (1, 5 or 10 cm) for 10 min to give three different freezing rates. Semen samples were thawed at 30°C for 10 s. The variables assessed after thawing were sperm motility, duration of motility and viability. Our results clearly indicate a significant effect of freezing rate on post-thaw semen quality. Semen frozen 5 cm above the liquid nitrogen surface showed the best quality after freezing/thawing. Based on these in vitro data, 2 groups of 200 eggs were fertilized with fresh semen or semen frozen 5 cm above the liquid nitrogen surface. Fertilization and hatching rates recorded for eggs fertilized with frozen semen were significantly lower (25.4% and 22.5%, respectively) than the ones obtained using fresh semen (87.8% and 75.5%, respectively). An effective freezing protocol will allow for the creation of a sperm cryobank to recover the original population of Mediterranean brown trout in the Biferno river.

  19. Detecting phase separation of freeze-dried binary amorphous systems using pair-wise distribution function and multivariate data analysis

    DEFF Research Database (Denmark)

    Chieng, Norman; Trnka, Hjalte; Boetker, Johan

    2013-01-01

    The purpose of this study is to investigate the use of multivariate data analysis for powder X-ray diffraction-pair-wise distribution function (PXRD-PDF) data to detect phase separation in freeze-dried binary amorphous systems. Polymer-polymer and polymer-sugar binary systems at various ratios were...... freeze-dried. All samples were analyzed by PXRD, transformed to PDF and analyzed by principal component analysis (PCA). These results were validated by differential scanning calorimetry (DSC) through characterization of glass transition of the maximally freeze-concentrate solute (Tg'). Analysis of PXRD......-PDF data using PCA provides a more clear 'miscible' or 'phase separated' interpretation through the distribution pattern of samples on a score plot presentation compared to residual plot method. In a phase separated system, samples were found to be evenly distributed around the theoretical PDF profile...

  20. De-freezing frozen patient management.

    Science.gov (United States)

    Kobo-Greenhut, Ayala; Shnifi, Amin; Tal-Or, Eran; Magnezi, Racheli; Notea, Amos; Ruach, Meir; Onn, Erez; Cohen, Ayala; Doveh, Etti; Ben Shlomo, Izhar

    2017-04-01

    To compare the effectiveness of two methods in encouraging the consideration of a leap from one patient management routine to another: (i) real-time review of the facts by an external medical team (ii) implementation of the 're-thinking-protocol' ('de-Freezing') by both treating and external medical teams. Students accompanied doctors, nurses and patients as non-interrupting observers. When an obvious gap between the expected and actual findings occurred, it was discussed four times: by two teams (treating team, external medical team) in two discussion modes (real-time review, de-Freezing-questionnaire). The students then recorded if a leap was considered for each discussion. The study was conducted in the emergency department of the Baruch Padeh Medical Centre, Poriya, Israel. All patients were included during times when both medical teams (treating, external) were present. During 14 periods of 5-7 h each, 459 patients were sampled. In 183 patients, 200 gaps were discovered. The external team considered a leap 76 times, compared with 47 by the treating team (P management routine to another is emphasized in the training of physicians, medical teams too often fail to do so. The de-Freezing-protocol inexpensively encourages the consideration of a leap beyond what is evoked by the involvement of an external team. The protocol is applicable to all medical processes and should be incorporated into medical practice and education.

  1. Analysis for Difficulty during Freeze-Drying Feizixiao Lychees

    Directory of Open Access Journals (Sweden)

    L. L. Huang

    2017-01-01

    Full Text Available Compared to other cultivar lychees, volume density of Feizixiao lychee was higher due to serious shrinkage during freeze-drying (FD. Guiwei lychee and Nuomici lychee were used for comparison in order to illuminate the reason of the aforementioned phenomenon. Lower prefreezing temperature could not improve the volume density of Feizixiao lychee. Microstructure results show that pulp cell of Feizixiao lychee (tail was smaller and more compact than Guiwei and Nuomici lychee pulp cell. In addition, there is a membrane around the surface of Feizixiao lychee pulp. And the microstructure of Feizixiao lychee tip pulp cell is different from tail pulp cell. Membrane and tip pulp cell are both smaller and more compact than tail pulp cell. These structure differences hinder the moisture removing of Feizixiao lychee during FD. Removing the membrane and tip pulp could not improve the volume density of Feizixiao lychee. Ultrasound treatment for 30 min could significantly enhance the volume density of Feizixiao lychee.

  2. Superoxide dismutase enhances tolerance of freezing stress in transgenic alfalfa (Medicago sativa L.).

    Science.gov (United States)

    McKersie, B D; Chen, Y; de Beus, M; Bowley, S R; Bowler, C; Inzé, D; D'Halluin, K; Botterman, J

    1993-01-01

    Activated oxygen or oxygen free radicals have been implicated in a number of physiological disorders in plants including freezing injury. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide into O2 and H2O2 and thereby reduces the titer of activated oxygen molecules in the cell. To further examine the relationship between oxidative and freezing stresses, the expression of SOD was modified in transgenic alfalfa (Medicago sativa L.). The Mn-SOD cDNA from Nicotiana plumbaginifolia under the control of the cauliflower mosaic virus 35S promoter was introduced into alfalfa using Agrobacterium tumefaciens-mediated transformation. Two plasmid vectors, pMitSOD and pChlSOD, contained a chimeric Mn-SOD construct with a transit peptide for targeting to the mitochondria or one for targeting to the chloroplast, respectively. The putatively transgenic plants were selected for resistance to kanamycin and screened for neomycin phosphotransferase activity and the presence of an additional Mn-SOD isozyme. Detailed analysis of a set of four selected transformants indicated that some had enhanced SOD activity, increased tolerance to the diphenyl ether herbicide, acifluorfen, and increased regrowth after freezing stress. The F1 progeny of one line, RA3-ChlSOD-30, were analyzed by SOD isozyme activity, by polymerase chain reaction for the Mn-SOD gene, and by polymerase chain reaction for the neo gene. RA3-ChlSOD-30 had three sites of insertion of pChlSOD, but only one gave a functional Mn-SOD isozyme; the other two were apparently partial insertions. The progeny with a functional Mn-SOD transgene had more rapid regrowth following freezing stress than those progeny lacking the functional Mn-SOD transgene, suggesting that Mn-SOD serves a protective role by minimizing oxygen free radical production after freezing stress. PMID:8290627

  3. Numerical Simulation of the Freeze-Thaw Behavior of Mortar Containing Deicing Salt Solution.

    Science.gov (United States)

    Esmaeeli, Hadi S; Farnam, Yaghoob; Bentz, Dale P; Zavattieri, Pablo D; Weiss, Jason

    2017-02-01

    This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.

  4. Out of the dark: Transitional subsurface-to-surface microbial diversity in a terrestrial serpentinizing seep (Manleluag, Pangasinan, the Philippines

    Directory of Open Access Journals (Sweden)

    Kristin eWoycheese

    2015-02-01

    Full Text Available In the Zambales ophiolite range terrestrial serpentinizing fluid seeps host diverse microbial assemblages. The fluids fall within the profile of Ca2+-OH--type waters, indicative of active serpentinization, and are low in dissolved inorganic carbon (<0.5 ppm. Influx of atmospheric carbon dioxide affects the solubility of calcium carbonate as distance from the source increases, triggering the formation of meter-scale travertine terraces. Samples were collected at the source and along the outflow channel to determine subsurface microbial community response to surface exposure. DNA was extracted and submitted for high-throughput 16S rRNA gene sequencing on the Illumina MiSeq platform. Taxonomic assignment of the sequence data indicates that 8.1% of the total sequence reads at the source of the seep affiliate with the genus Methanobacterium. Other major classes detected at the source include anaerobic taxa such as Bacteroidetes (40.7% of total sequence reads and Firmicutes (19.1% of total reads. Hydrogenophaga spp. increase in relative abundance as redox potential increases. At the carbonate terrace, 45% of sequence reads affiliate with Meiothermus spp. Taxonomic observations and geochemical data suggest that several putative metabolisms may be favorable, including hydrogen oxidation, H2-associated sulfur cycling, methanogenesis, methanotrophy, nitrogen fixation, ammonia oxidation, denitrification, nitrate respiration, methylotrophy, carbon monoxide respiration, and ferrous iron oxidation, based on capabilities of nearest known neighbors. Scanning electron microscopy and energy dispersive X-ray spectroscopy suggest that microbial activity produces chemical and physical traces in the precipitated carbonates forming downstream of the seep’s source. These data provide context for future serpentinizing seep ecosystem studies, particularly with regards to tropical biomes.

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

    Science.gov (United States)

    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. Freezing and non-freezing cold weather injuries: a systematic review.

    Science.gov (United States)

    Heil, Kieran; Thomas, Rachel; Robertson, Greg; Porter, Anna; Milner, Robert; Wood, Alexander

    2016-03-01

    The debilitating impact of cold weather on the human body is one of the world's oldest recorded injuries. The severe and life-changing damage which can be caused is now more commonly seen recreationally in extreme outdoor sports rather than in occupational settings such as the military. The diagnosis and treatment of these injuries need to be completed carefully but quickly to reduce the risk of loss of limb and possibly life. Therefore, we have conducted a systematic review of the literature surrounding cold weather injuries (CWIs) to ascertain the epidemiology and current management strategies. Medline (PubMED), EMBASE, CINHAL, Cochrane Collaboration Database, Web of Science, Scopus and Google Scholar. The risk of freeze thaw freeze injuries. Delayed surgical intervention when possible. Different epidemiology of freezing and non-freezing injuries. Prophylatic use of antibiotics; the use of vasodilators surgical and medical. The use of ilioprost and PFG2a for the treatment of deep frostbite. The treatment of non-freezing CWIs with their long-term follow-up. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. Optimization of a protective medium for freeze-dried Pichia membranifaciens and application of this biocontrol agent on citrus fruit.

    Science.gov (United States)

    Niu, X; Deng, L; Zhou, Y; Wang, W; Yao, S; Zeng, K

    2016-07-01

    To optimize a protective medium for freeze-dried Pichia membranifaciens and to evaluate biocontrol efficacies of agents against blue and green mould and anthracnose in citrus fruit. Based on the screening assays of saccharides and antioxidants, response surface methodology was used to optimize sucrose, sodium glutamate and skim milk to improve viability of freeze-dried Pi. membranifaciens. Biocontrol assays were conducted between fresh and freeze-dried Pi. membranifaciens against Penicillium italicum, Penicillium digitatum and Colletotrichum gloeosporioides in citrus fruit. Solving the regression equation indicated that the optimal protective medium was 6·06% (w/v) sucrose combined with 3·40% (w/v) sodium glutamate and 5·43% (w/v) skim milk. Pi. membranifaciens freeze-dried in the optimal protective medium showed 76·80% viability, and retained biocontrol efficacy against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. The optimal protective medium showed more effective protective properties than each of the three protectants used alone. The viability of freeze-dried Pi. membranifaciens finally reached 76·80%. Meanwhile, the biocontrol efficacies showed no significant difference between fresh and freeze-dried yeast against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. The results showed the potential value of Pi. membranifaciens CICC 32259 for commercialization. © 2016 The Society for Applied Microbiology.

  8. Characteristics of Vacuum Freeze Drying with Utilization of Internal Cooling and Condenser Waste Heat for Sublimation

    Directory of Open Access Journals (Sweden)

    Muhammad Alhamid

    2013-09-01

    Full Text Available Vacuum freeze drying is an excellent drying method, but it is very energy-intensive because a relatively long drying time is required. This research investigates the utilization of condenser waste heat for sublimation as a way of accelerating the drying rate. In addition, it also investigates the effect of internal cooling combined with vacuum cooling in the pressure reduction process. Jelly fish tentacles were used as the specimen, with different configurations for condenser heat waste and internal cooling valve opening. The results show that heating with condenser heat waste can accelerate the drying rate up to 0.0035 kg/m2.s. In addition, pre-freezing by internal cooling prevents evaporation until the mass of the specimen is 0.47 g and promotes transition of the specimen into the solid phase.

  9. Mathematical prediction of freezing times of bovine semen in straws placed in static vapor over liquid nitrogen.

    Science.gov (United States)

    Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

    2013-02-01

    A widespread practice in cryopreservation is to freeze spermatozoa by suspending the straws in stagnant nitrogen vapor over liquid nitrogen (N(2)V/LN(2)) for variable periods of time before plunging into liquid nitrogen (-196°C) for indefinite storage. A mathematical heat transfer model was developed to predict freezing times (phase change was considered) required for bull semen and extender packaged in 0.5ml plastic straws and suspended in static liquid nitrogen vapor. Thermophysical properties (i.e. thermal conductivity, specific heat, density, initial freezing temperature) of bovine semen and extender as a function of temperature were determined considering the water change of phase. The non-stationary heat transfer partial differential equations with variable properties (nonlinear mathematical problem) were numerically solved considering in series thermal resistances (semen suspension-straw) and the temperature profiles were obtained for both semen suspension and plastic straw. It was observed both the external heat transfer coefficient in stagnant nitrogen vapor and its temperature (controlled by the distance from the surface of liquid nitrogen to the straw) affected freezing times. The accuracy of the model to estimate freezing times of the straws was further confirmed by comparing with experimental literature data. Results of this study will be useful to select "safe" holding times of bull semen in plastic straws placed N(2)V/LN(2) to ensure that complete freezing of the sample has occurred in the nitrogen vapor and avoid cryodamage when plunging in LN(2). Freezing times predicted by the numerical model can be applied to optimize freezing protocols of bull semen in straws. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. Lyoprotective Effect of Alkyl Sulfobetaines for Freeze-drying 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine Liposomes.

    Science.gov (United States)

    Aikawa, Tatsuo; Sato, Kanta; Okado, Hiroki; Takahashi, Yukako; Kondo, Takeshi; Yuasa, Makoto

    2017-11-01

    A liposome is a molecular assembly in the form of a vesicle comprised of a phospholipid bilayer. Liposomes can be used as molecular containers in various fields such as pharmaceutical, cosmetic, and food industries. It is difficult to maintain the original structure of liposomes in an aqueous medium. Phospholipids, which are components of liposomes, are susceptible to hydrolysis, which causes disruption of the liposomal structure and dysfunction of the molecular container. In this context, freeze-drying liposomes is a preferable method to improve the shelf life of liposomes. However, when freeze-drying liposomes, a lyoprotective agent is required to preserve their original structure. In this study, we investigate whether alkyl sulfobetaines (SBn, n: number of carbons in the alkyl chain, n = 1-18) can be used as lyoprotectants for 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes. The results indicated that the length of the alkyl chain of the SBn was an important factor to prevent liposome disruption during the freeze-drying and subsequent rehydration processes. The use of SBn with an alkyl chain of intermediate length (n = 6-10) could prevent liposome disruption and remarkably reduce the gel-to-liquid crystal phase transition temperature (Tm) of the freeze-dried liposomes. This indicates that these SBn could intercalate in the dried bilayer and reduce intermolecular interaction between DPPC in the bilayer. The Tm reduction of the freeze-dried liposomes should contribute to prevention of the gel-to-liquid phase transition of the liposomes during the rehydration process, which has been known to be a main cause of liposome disruption. We expect that the results from this study will provide an insight into the influence of zwitterionic additives on freeze-dried lipid bilayers and the lyoprotective effect, which should be useful in many biochemical and biomedical fields.

  11. Cooling Mediterranean Sea surface temperatures during the Late Miocene provide a climate context for evolutionary transitions in Africa and Eurasia

    Science.gov (United States)

    Tzanova, Alexandrina; Herbert, Timothy D.; Peterson, Laura

    2015-06-01

    In the Late Miocene, grasslands proliferated, succulent plants diversified in the mid-latitudes, and the desert-like conditions appeared in the Sahara. Despite this major environmental change on land, the coeval deep-sea oxygen isotope record does not provide evidence for significant high latitude cooling or continental ice growth, making it difficult to relate widespread terrestrial environmental change to global climatic changes. A U37K‧ -derived sea surface temperature (SST) reconstruction spanning 13 to 6 Ma from uplifted hemipelagic sediments in Northern Italy provides the first continuous mid-latitude temperature record with which to compare the evolution of aridity and biotic events at similar latitudes in Northern Africa and Pakistan. Between 13 and 8.8 Ma, Mediterranean SST lay near the upper limit of the alkenone temperature proxy (∼28 °C), exceeding modern SST at the site by as much as 10 °C. Throughout the record, sapropel layers correspond to local SST maxima, suggesting that Late Miocene hydrological conditions in the Mediterranean responded to insolation forcing via mechanisms similar to those documented for the Plio-Pleistocene. Mediterranean SST cooled rapidly beginning at ∼8 Ma, with an episode of intense cooling to ∼19 °C between 7.2 Ma and 6.6 Ma, followed by a rebound to ∼25 °C preceding the Messinian Salinity Crisis at 5.9 Ma. These observations establish, for the first time, a direct relationship between increasing aridity in the Northern hemisphere mid-latitudes and significant cooling. Evidently, this cooling was not accompanied by significant growth in continental ice volume. The extreme warmth and subsequent cooling of the Mediterranean Sea are not well-represented in current Late Miocene climate models, which our results suggest underestimate regional warmth prior to the Late Miocene cooling. Evidence of secular cooling during the Late Miocene gives new support to the much-debated link between a possible decline in

  12. Optimization of surface enhanced Raman scattering (SERS) assay for the transition from benchtop to handheld Raman systems

    Science.gov (United States)

    Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Coté, Gerard

    2017-02-01

    Human biomarkers are indicative of the body's relative state prior to the onset of disease, and sometimes before symptoms present. While blood biomarker detection has achieved considerable success in laboratory settings, its clinical application is lagging and commercial point-of-care devices are rare. A physician's ability to detect biomarkers such as microRNA-17, a potential epigenetic indicator of preeclampsia in pregnant woman, could enable early diagnosis and preventive intervention as early as the 1st trimester. One detection approach employing DNA-functionalized nanoparticles to detect microRNA-17, in conjunction with surface-enhanced Raman spectroscopy (SERS), has shown promise but is hindered, in part, by the use of large and expensive benchtop Raman microscopes. However, recent strides have been made in developing portable Raman systems for field applications. Characteristics of the SERS assay responsible for strengthening the assay's plasmonic response were explored, whilst comparing the results from both benchtop and portable Raman systems. The Raman spectra and intensity of three different types of photoactive molecules were compared as potential Raman reporter molecules: chromophores, fluorophores, and highly polarizable small molecules. Furthermore, the plasmonic characteristics governing the formation of SERS colloidal nanoparticle assemblies in response to DNA/miRNA hybridization were investigated. There were significant variations in the SERS enhancement in response to microRNA-17 using our assay depending on the excitation lasers at wavelengths of 532 nm and 785 nm, depending on which of the three different Raman systems were used (benchtop, portable, and handheld), and depending on which of the three different Raman reporters (chromophore, fluorophore, or Raman active molecule) were used. Analysis of data obtained did indicate that signal enhancement was better for the chromophore (MGITC) and Raman active molecule (DTNB) than it was for the

  13. The Interdependence of Lake Ice and Climate in Central North America. [correlation between freeze/than cycles of lakes and regional weather variations

    Science.gov (United States)

    Jelacic, A. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A comparison of lake freeze transition zone migration with the movement of large pressure centers reveals the following consistencies: (1) polar continental cyclones originate within and/or travel along the trend of the transition zone; (2) polar continental anticyclones fail to cross the transition zone; (3) polar outbreak anticyclones pass through the transition zone, apparently unaffected. In addition, storm centers associated with the transition zone undergo significant intensification manifest by a deepening of the pressure through and increased precipitation outside the zone.

  14. Transition of the Slab Geometry at the Eastern End of the Trans-Mexican Volcanic Belt from Ambient Noise and Earthquake Surface Waves

    Science.gov (United States)

    Castillo, J.; Clayton, R. W.; Spica, Z.; Perez-Campos, X.

    2016-12-01

    The Trans-Mexican Volcanic Belt (TMVB) is one of the largest continental volcanic arcs on the North America plate, spanning 1200 km in central Mexico. Its diversity in volcanic style and non-parallel orientation with the trench are explained by along-strike variations in the subduction parameters of the Rivera and Cocos plates. However, the abrupt termination of the TMVB on its eastern end with the Pico de Orizaba volcano is puzzling as the transition of the Cocos flat-slab geometry to normal subduction appears to be smooth through this region. There is evidence that a tear in the slab is developing, but it is unclear how this feature can support the unusually large topographic gradient. Here, we use 6-70 s surface waves from ambient-noise cross-correlations, correlations of coda of cross-correlations, and earthquake data, to image the shear wave velocity structure to a depth of 150 km. The structures observed in the proposed velocity model are in agreement with the major tectonic features of the region. Low velocities correlate well with the active volcanos of the TMVB and the Veracruz Basin whereas high velocities coincide with the southern end of the Sierra Madre Oriental mountain range. Large velocity contrasts for the upper crust also show strong correspondence with the tectonostratigraphic terrane boundaries. A strong negative velocity perturbation that transitions to positive at 30 km depth and continues with a NE-SW orientation beneath Los Tuxtlas volcanic field is imaged and suggested to be related to the anomalous south-west dipping structure that has been evidenced by previous receiver function studies.

  15. Recent developments in smart freezing technology applied to fresh foods.

    Science.gov (United States)

    Xu, Ji-Cheng; Zhang, Min; Mujumdar, Arun S; Adhikari, Benu

    2017-09-02

    Due to the increased awareness of consumers in sensorial and nutritional quality of frozen foods, the freezing technology has to seek new and innovative technologies for better retaining the fresh like quality of foods. In this article, we review the recent developments in smart freezing technology applied to fresh foods. The application of these intelligent technologies and the associated underpinning concepts have greatly improved the quality of frozen foods and the freezing efficiency. These technologies are able to automatically collect the information in-line during freezing and help control the freezing process better. Smart freezing technology includes new and intelligent technologies and concepts applied to the pretreatment of the frozen product, freezing processes, cold chain logistics as well as warehouse management. These technologies enable real-time monitoring of quality during the freezing process and help improve product quality and freezing efficiency. We also provide a brief overview of several sensing technologies used to achieve automatic control of individual steps of freezing process. These sensing technologies include computer vision, electronic nose, electronic tongue, digital simulation, confocal laser, near infrared spectroscopy, nuclear magnetic resonance technology and ultrasound. Understanding of the mechanism of these new technologies will be helpful for applying them to improve the quality of frozen foods.

  16. High-pressure freezing, chemical fixation and freeze-substitution for immuno-electron microscopy.

    Science.gov (United States)

    Mühlfeld, Christian

    2010-01-01

    This chapter deals with tissue preparation for subsequent detection of molecules in biological samples using immunocytochemistry and transmission electron microscopy. The aim of these methods is to localize specific molecules at high resolution in order to identify their subcellular (or exact extracellular) localization. The methods are based on the use of antibodies or other affinity markers that bind specifically to a molecule of interest and a suitable detection system, e.g. a secondary antibody coupled to a gold particle of 5-15 nm size. Two different ways of sample preparation are described: (1) high-pressure freezing followed by freeze-substitution and immunogold labeling and (2) chemical fixation followed by freeze-substitution and immunogold labeling. Both methods have advantages and disadvantages that influence their utility in a given study design.

  17. Does deposition freezing really exist? At least different as we thought

    Science.gov (United States)

    Abdelmonem, Ahmed

    2017-04-01

    The structural and chemical properties of the surface of an IN-particle (INP) play a major role in its IN ability. This role is not well explored in terms of water/INP-surface molecular-level interactions. Recent MD simulations on deposition freezing showed that water first deposits as liquid clusters and then crystallize isothermally from there [1]. We probe freezing of water on INPs of different structural and chemical properties under varying supersaturation conditions using non-linear optical spectroscopy, mainly second harmonic generation (SHG) and sum frequency generation (SFG) [2, 3]. This presentation will show very recent preliminary experimental results comparing deposition, condensation and immersion freezing (DF, CF and IF respectively) on an atmospheric relevant metal oxide surface (mica) using supercooled SHG measurements. It is found that the signal drops upon the formation of a thin film regardless of 1) the freezing path (DF or CF), 2) the formed phase (ice or liquid), indicating a similar molecular structuring. The observed structuring similarity between DF, CF and LC films is a kick-off experimental confirmation of those computational results. References 1. Lupi, L., N. Kastelowitz, and V. Molinero, Vapor deposition of water on graphitic surfaces: Formation of amorphous ice, bilayer ice, ice I, and liquid water. The Journal of Chemical Physics, 2014. 141(18): p. 18C508. 2. Abdelmonem, A., J. Lützenkirchen, and T. Leisner, Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy. Atmospheric Measurement Techniques, 2015. 8(8): p. 3519-3526. 3. Abdelmonem, A., et al., Surface charge-induced orientation of interfacial water suppresses heterogeneous ice nucleation on α-alumina (0001). Angewandte Chemie (Submitted), 2017.

  18. A sample-freezing drive shoe for a wire line piston core sampler

    Science.gov (United States)

    Murphy, F.; Herkelrath, W.N.

    1996-01-01

    Loss of fluids and samples during retrieval of cores of saturated, noncohesive sediments results in incorrect measures of fluid distributions and an inaccurate measure of the stratigraphic position of the sample. To reduce these errors, we developed a hollow drive shoe that freezes in place the lowest 3 inches (75 mm) of a 1.88-inch-diameter (48 mm), 5-foot-long (1.5 m) sediment sample taken using a commercial wire line piston core sampler. The end of the core is frozen by piping liquid carbon dioxide at ambient temperature through a steel tube from a bottle at the land surface to the drive shoe where it evaporates and expands, cooling the interior surface of the shoe to about -109??F (-78??C). Freezing a core end takes about 10 minutes. The device was used to collect samples for a study of oil-water-air distributions, and for studies of water chemistry and microbial activity in unconsolidated sediments at the site of an oil spill near Bemidji, Minnesota. Before freezing was employed, samples of sandy sediments from near the water table sometimes flowed out of the core barrel as the sampler was withdrawn. Freezing the bottom of the core allowed for the retention of all material that entered the core barrel and lessened the redistribution of fluids within the core. The device is useful in the unsaturated and shallow saturated zones, but does not freeze cores well at depths greater than about 20 feet (6 m) below water, possibly because the feed tube plugs with dry ice with increased exhaust back-pressure, or because sediment enters the annulus between the core barrel and the core barrel liner and blocks the exhaust.

  19. Impact of the global SST gradients changes on the Antarctic ice sheet surface mass balance through the Plio/Pliocene transition

    Science.gov (United States)

    Colleoni, Florence; Florindo, Fabio; McKay, Robert; Golledge, Nicholas; Sangiorgi, Francesca; Montoli, Enea; Masina, Simona; Cherchi, Annalisa; De Santis, Laura

    2017-04-01

    Sea Surface Temperatures (SST) reconstructions have shown that the Pliocene global zonal and meridional temperature gradients were different from today, implying changes of atmospheric and oceanic circulations, and thus of the main teleconnections. The impact of the main atmospheric teleconnections on the surface mass balance (SMB) of the Antarctic ice sheet (AIS) in the past has been seldom investigated. The ANDRILL marine record have shown that at the end of the Pliocene, the ice sheet expanded in the Ross Sea concomitantly with the expansion of the sea ice cover. This would have enhanced the formation of bottom waters that in turn, would have fostered upwelling along the West African coast and along the coast of Peru. The impact of Antarctica on the tropical climate dynamics has been shown by previous studies. To close the loop, this work investigates the impact of the tropical and high-latitude SST cooling on the main atmospheric teleconnections and then on the Antarctic SMB through the Plio/Pleistocene transition. Idealized Atmospheric General Circulation Model simulations are performed, in which high-latitude and tropical SST cooling are prescribed starting from the Pliocene SST. The atmospheric conditions obtained are then used to force an ice sheet model and a stand-alone energy balance model to investigate the impact on the SMB of the two main atmospheric teleconnections active in the Southern Hemisphere, namely the Southern Annular Mode (SAM) and the Pacific-South-American oscillation (PSA. In agreement with ANDRILL marine records, results show that the Easterlies strengthen along the Antarctic coasts during the Plio/Pleistocene transition. This, however, occurs only after cooling the tropical SSTs in the AGCM simulations. More importantly, the cooling of the tropical SST, through the strengthening of the PSA, has the largest influence on the spatial distribution of the climatic anomalies over Antarctica. This explains most of the SMB patterns simulated

  20. Protective effect of sucrose on the membrane properties of Lactobacillus casei Zhang subjected to freeze-drying.

    Science.gov (United States)

    Li, Haiping; Lu, Meijun; Guo, Hongfang; Li, Wei; Zhang, Heping

    2010-04-01

    The purpose of this research was to investigate the influence of sucrose at 2.0, 4.0, and 8.0% as a protectant during freeze-drying on the viability and membrane properties of Lactobacillus casei Zhang. Membrane properties were determined using zeta potential, hydrophobicity, fluidity, and integrity before and after freeze-drying. Exposing L. casei Zhang to sucrose protected it from drastic changes in cell surface electrophoretic mobility and hydrophobicity in contrast with the untreated condition, and the effect was dose related. Sucrose caused an increase in membrane fluidity compared with the control sample. Moreover, 2.0% sucrose decreased the general polarization values less than 4.0 or 8.0% sucrose, while 4.0% sucrose and 8.0% sucrose had no significant difference in decreasing general polarization values (P freeze-dried in the presence of 2.0% sucrose retained up to 23.7% membrane integrity, whereas cells freeze-dried with 4.0 and 8.0% sucrose had 32.4 and 37.6% membrane integrity compared with that of L. casei Zhang before freeze-drying. Correspondingly, the number of survivors of L. casei Zhang, determined by the plate count method, decreased from 8.02 to 0.63 log CFU/ml after freeze-drying in the absence of sucrose. However, in the presence of 2.0, 4.0, and 8.0% sucrose, the numbers of survivors were 2.01, 2.87, and 3.20 log CFU/ml after freeze-drying, respectively. The present work suggested that sucrose was an effective membrane protectant at 2.0, 4.0, or 8.0% on the surface zeta potential, hydrophobicity, fluidity, and integrity of L. casei Zhang.