WorldWideScience

Sample records for temperature gradient analyzers

  1. Superconductors in a temperature gradient

    CERN Document Server

    Huebener, Rudolf Peter

    1995-01-01

    In the mixed state of a type II superconductor quasiparticles and magnetic flux quanta respond to a temperature gradient by thermal diffusion, in this way generating the Seebeck and Nernst effects, respectively. Our understanding of the Seebeck effect originates from an extension of the two-fluid counterflow concept, originally introduced by Ginzburg, to the situation where vortices (with a normal core) are imbedded in the superconducting phase. This mechanism results in an intimate connection between the Seebeck coefficient and the electric resistivity due to vortex motion. In all thermal diffusion processes it is the transport entropy of the diffusing species that determines the driving force, and the physics of this quantity is illustrated. Our discussion of the experimental side concentrates on the recent work performed with the cuprate superconductors. The characteristic broadening of the resistive transition in the mixed state, found in these materials due to their high anisotropy and the peculiar vorte...

  2. Sound beam manipulation based on temperature gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-28

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.

  3. Air temperature gradient in large industrial hall

    Science.gov (United States)

    Karpuk, Michał; Pełech, Aleksander; Przydróżny, Edward; Walaszczyk, Juliusz; Szczęśniak, Sylwia

    2017-11-01

    In the rooms with dominant sensible heat load, volume airflow depends on many factors incl. pre-established temperature difference between exhaust and supply airflow. As the temperature difference is getting higher, airflow volume drops down, consequently, the cost of AHU is reduced. In high industrial halls with air exhaust grids located under the ceiling additional temperature gradient above working zone should be taken into consideration. In this regard, experimental research of the vertical air temperature gradient in high industrial halls were carried out for the case of mixing ventilation system The paper presents the results of air temperature distribution measurements in high technological hall (mechanically ventilated) under significant sensible heat load conditions. The supply airflow was delivered to the hall with the help of the swirl diffusers while exhaust grids were located under the hall ceiling. Basing on the air temperature distribution measurements performed on the seven pre-established levels, air temperature gradient in the area between 2.0 and 7.0 m above the floor was calculated and analysed.

  4. Weakening of lower tropospheric temperature gradient between ...

    Indian Academy of Sciences (India)

    e-mail: bawiskar@hotmail.com bawiskar@tropmet.res.in. The study shows that in the scenario of global warming temperature gradient (TG) between Indian landmass and Arabian Sea/Bay of Bengal is significantly decreasing in the lower troposphere with maxima around 850hPa. TG during pre-monsoon (March to May) is ...

  5. Temperature gradients assist carbohydrate allocation within trees.

    Science.gov (United States)

    Sperling, Or; Silva, Lucas C R; Tixier, Aude; Théroux-Rancourt, Guillaume; Zwieniecki, Maciej A

    2017-06-12

    Trees experience two distinct environments: thermally-variable air and thermally-buffered soil. This generates intra-tree temperature gradients, which can affect carbon metabolism and water transport. In this study, we investigated whether carbohydrate allocation within trees is assisted by temperature gradients. We studied pistachio (Pistacia integerrima) to determine: (1) temperature-induced variation in xylem sugar concentration in excised branches; (2) changes in carbon allocation in young trees under simulated spring and fall conditions; and (3) seasonal variability of starch levels in mature orchard trees under field conditions. We found that warm branches had less sugar in perfused sap than cold branches due to increasing parenchyma storage. Simulated spring conditions promoted allocation of carbohydrates from cold roots to warm canopy and explained why starch levels surged in canopies of orchard trees during early spring. This driving force of sugar transport is interrupted in fall when canopies are colder than roots and carbohydrate redistribution is compartmentalized. On the basis of these findings, we propose a new mechanistic model of temperature-assisted carbohydrate allocation that links environmental cues and tree phenology. This data-enabled model provides insights into thermal "fine-tuning" of carbohydrate metabolism and a warning that the physiological performance of trees might be impaired by climatic changes.

  6. Damping of toroidal ion temperature gradient modes

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, H. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    1999-04-01

    The temporal evolution of linear toroidal ion temperature gradient (ITG) modes is studied based on a kinetic integral equation including an initial condition. It is shown how to evaluate the analytic continuation of the integral kernel as a function of a complex-valued frequency, which is useful for analytical and numerical calculations of the asymptotic damping behavior of the ITG mode. In the presence of the toroidal {nabla}B-curvature drift, the temporal dependence of the density and potential perturbations consists of normal modes and a continuum mode, which correspond to contributions from poles and from an integral along a branch cut, respectively, of the Laplace-transformed potential function of the complex-valued frequency. The normal modes have exponential time dependence with frequencies and growth rates determined by the dispersion relation while the continuum mode, which has a ballooning structure, shows a power law decay {proportional_to} t{sup -2} in the asymptotic limit, where t is the time variable. Therefore, the continuum mode dominantly describes the long-time asymptotic behavior of the density and potential perturbations for the stable system where all normal modes have negative growth rates. By performing proper analytic continuation for the homogeneous version of the kinetic integral equation, dependences of the normal modes` growth rate, real frequency, and eigenfunction on {eta}{sub i} (the ratio of the ion temperature gradient to the density gradient), k{sub {theta}} (the poloidal wavenumber), s (the magnetic shear parameter), and {theta}{sub k} (the ballooning angle corresponding to the minimum radial wavenumber) are numerically obtained for both stable and unstable cases. (author)

  7. Emergence of a Detonation due to an Initial Temperature Gradient

    Science.gov (United States)

    Hawa, Takumi; Schwendeman, Donald; Kapila, Ashwani

    2000-11-01

    Emergence of a detonation in a homogeneous, exothermically reacting medium can be deemed to occur in two phases. The first phase processes the medium so as to create conditions ripe for the onset of detonation. The actual events leading up to preconditioning may vary from one experiment to the next, but typically, at the end of this stage the medium is hot and in a state of nonuniformity. The second phase consists of the actual formation of the detonation wave via chemico-gasdynamic interactions. This phase is analyzed in detail, for an idealized medium with simple, state-sensitive kinetics and a prescribed initial temperature gradient. Depending upon the size of the gradient, there are two distinct pathways to a ZND detonation. For shallow gradients the event begins with a nearly constant-volume localized explosion, followed by the emergence of a supersonic, shockless reaction wave that decelerates to the CJ speed and then rapidly transforms into the ZND structure. For sharp gradients the localized explosion occurs at nearly constant pressure, and the detonation is then formed as a result of an accelerating reaction wave catching up to a shock. Within the second scenario there are further variations. The manner in which the above processes are affected by flow divergence (cylindrical and spherical symmetric cases) is examined as well. The analysis is based on a combination of asymptotics and finely resolved numerics.

  8. Thermoacoustic mixture separation with an axial temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Geller, Drew W [Los Alamos National Laboratory; Swift, Gregory A [Los Alamos National Laboratory

    2008-01-01

    The theory of thermoacoustic mixture separation is extended to include the effect of a nonzero axial temperature gradient. The analysis yields a new term in the second-order mole flux that is proportional to the temperature gradient and to the square of the volumetric velocity and is independent of the phasing of the wave. Because of this new term, thermoacoustic separation stops at a critical temperature gradient and changes direction above that gradient. For a traveling wave, this gradient is somewhat higher than that predicted by a simple four-step model. An experiment tests the theory for temperature gradients from 0 to 416 K/m in 50-50 He-Ar mixtures.

  9. Variability in estuarine water temperature gradients and influence on ...

    African Journals Online (AJOL)

    Variability in estuarine water temperature gradients and influence on the distribution of zooplankton: a biogeographical perspective. TH Wooldridge, SHP Deyzel. Abstract. Structure and variability of water temperature gradients and potential influence on distribution of two tropical zooplankters (the mysid Mesopodopsis ...

  10. Temperature gradient-induced magnetization reversal of single ferromagnetic nanowires

    Science.gov (United States)

    Michel, Ann-Kathrin; Corinna Niemann, Anna; Boehnert, Tim; Martens, Stephan; Montero Moreno, Josep M.; Goerlitz, Detlef; Zierold, Robert; Reith, Heiko; Vega, Victor; Prida, Victor M.; Thomas, Andy; Gooth, Johannes; Nielsch, Kornelius

    2017-12-01

    In this study, we investigate the temperature- and temperature gradient-dependent magnetization reversal process of individual, single-domain Co39Ni61 and Fe15Ni85 ferromagnetic nanowires via the magneto-optical Kerr effect and magnetoresistance measurements. While the coercive fields (H C) and therefore the magnetic switching fields (H SW) generally decrease under isothermal conditions at elevated base temperatures (T base), temperature gradients (ΔT) along the nanowires lead to an increased switching field of up to 15% for ΔT  = 300 K in Co39Ni61 nanowires. This enhancement is attributed to a stress-induced, magneto-elastic anisotropy term due to an applied temperature gradient along the nanowire that counteracts the thermally assisted magnetization reversal process. Our results demonstrate that a careful distinction between locally elevated temperatures and temperature gradients has to be made in future heat-assisted magnetic recording devices.

  11. Calculation of Vertical Temperature Gradients in Heated Rooms

    DEFF Research Database (Denmark)

    Overby, H.; Steen-Thøde, Mogens

    This paper deals with a simple model which predicts the vertical temperature gradient in a heated room. The gradient is calculated from a dimensionless temperature profile which is determined by two room air temperatures only, the mean temperature in the occupied zone and the mean temperature...... in the zone above the occupied zone. A model to calculate the two air temperatures has been developed and implemented in Suncode- PC, a thermal analysis programme for residential and small commercial buildings. The dimensionless temperature profile based on measurements in a laboratory test room is presented...

  12. Near-surface temperature gradient in a coastal upwelling regime

    Science.gov (United States)

    Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

    2014-08-01

    In oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

  13. Influence of pouring temperature on a thermal gradient

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-01-01

    Full Text Available In the thesis there are presented results of computer simulation of casting solidification process, characteristics of solidification rate in several points as well as course of gradient change between these points. Based on the obtained results, an influence of initial conditions on temperature gradient during the solidification process was determined.

  14. Surface Tension Gradients Induced by Temperature: The Thermal Marangoni Effect

    Science.gov (United States)

    Gugliotti, Marcos; Baptisto, Mauricio S.; Politi, Mario J.

    2004-01-01

    Surface tensions gradients were generated in a thin liquid film because of the local increase in temperature, for demonstration purposes. This is performed using a simple experiment and allows different alternatives for heat generation to be used.

  15. Vacuum membrane distillation by microchip with temperature gradient.

    Science.gov (United States)

    Zhang, Yaopeng; Kato, Shinji; Anazawa, Takanori

    2010-04-07

    A multilayered microchip (25 x 95 mm) used for vacuum distillation is designed, fabricated and tested by rectification of a water-methanol mixture. The polymer chip employs a cooling channel to generate a temperature gradient along a distillation channel below, which is separated into a channel (72 microm deep) for liquid phase and a channel (72 microm deep) for vapor phase by an incorporated microporous poly(tetrafluoroethylene) (PTFE) membrane. The temperature gradient is controlled by adjusting hotplate temperature and flow rate of cooling water to make the temperatures in the stripping section higher than the increasing boiling points of the water-enriched liquids and the temperatures in the rectifying section lower than the decreasing dew points of the methanol-enriched vapors. The effects of temperature gradient, feed composition, feed flow rate and membrane pore size on the micro distillation are also investigated. A theoretical plate number up to 1.8 is achieved at the optimum conditions.

  16. Presence and significance of temperature gradients among different ovarian tissues

    DEFF Research Database (Denmark)

    Hunter, Ronald H.; Einer-Jensen, Niels; Greve, Torben

    2006-01-01

    also be involved. Temperature gradients would be maintained locally by counter-current heat exchange mechanisms and, in this context, the microvasculature and lymphatic flow of individual follicles were found to be appropriate. Observations on the temperature of preovulatory follicles appear relevant...

  17. The ion temperature gradient: An intrinsic property of Earth's magnetotail

    Science.gov (United States)

    Lu, San; Artemyev, A. V.; Angelopoulos, V.; Lin, Y.; Wang, X. Y.

    2017-08-01

    Although the ion temperature gradient along (XGSM) and across (ZGSM) the Earth's magnetotail, which plays a key role in generating the cross-tail current and establishing pressure balance with the lobes, has been extensively observed by spacecraft, the mechanism responsible for its formation is still unknown. We use multispacecraft observations and three-dimensional (3-D) global hybrid simulations to reveal this mechanism. Using THEMIS (Time History of Events and Macroscale Interactions during Substorms), Geotail, and ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun) observations during individual, near-simultaneous plasma sheet crossings from 10 to 60 RE, we demonstrate that the ion temperature ZGSM profile is bell-shaped at different geocentric distances. This ZGSM profile is also prevalent in statistics of 200 THEMIS current sheet crossings in the near-Earth region. Using 3-D global hybrid simulations, we show that mapping of the XGSM gradient of ion temperature along magnetic field lines produces such a bell-shaped profile. The ion temperature mapping along magnetic field lines in the magnetotail enables construction of two-dimensional distributions of these quantities from vertical (north-south) spacecraft crossings. Our findings suggest that the ion temperature gradient is an intrinsic property of the magnetotail that should be considered in kinetic descriptions of the magnetotail current sheet. Toward this goal, we use theoretical approaches to incorporate the temperature gradient into kinetic current sheet models, making them more realistic.

  18. Bandwidth control of a Ti:PPLN Solc filter by a temperature-gradient-control technique.

    Science.gov (United States)

    Lee, Yeung Lak; Noh, Young-Chul; Kee, Chul-Sik; Yu, Nan Ei; Shin, Woojin; Jung, Changsoo; Ko, Do-Kyeong; Lee, Jongmin

    2008-09-01

    We have demonstrated the bandwidth control of a Ti-diffused periodically poled LiNbO(3) (Ti:PPLN) Solc filter by a temperature-gradient-control technique. Up to 2.8 nm of filtering bandwidth was achieved with a simple temperature-gradient-control technique in a 78-mm-long of Ti:PPLN waveguide, which has a 0.2 nm filtering bandwidth at an uniform temperature. We have also analyzed the experimental results with the theoretical calculation which is derived from the codirectional coupled mode equations.

  19. Light Ray Displacements due to Air Temperature Gradient

    CERN Document Server

    Teymurazyan, A; CERN. Geneva

    2000-01-01

    Abstract In the optical monitoring systems suggested to control the geometry of tracking spectrometers, light beams serve as reference frames for the measurement of the tracking chamber displacements and deformations. It is shown that air temperature gradients can induce systematic errors which considerably exceed the intrinsic resolution of the monitoring system.

  20. Ion temperature gradient driven mode in presence of transverse velocity shear in magnetized plasmas

    DEFF Research Database (Denmark)

    Chakrabarti, N.; Juul Rasmussen, J.; Michelsen, Poul

    2005-01-01

    The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel "nonmodal" calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth...

  1. Dynamics of an insulating Skyrmion under a temperature gradient.

    Science.gov (United States)

    Kong, Lingyao; Zang, Jiadong

    2013-08-09

    We study the Skyrmion dynamics in thin films under a temperature gradient. Our numerical simulations show that both single and multiple Skyrmions in a crystal move towards the high temperature region, which is contrary to particle diffusion. Noticing a similar effect in the domain wall motion, we employ a theory based on magnon dynamics to explain this counterintuitive phenomenon. Unlike the temperature driven domain wall motion, the Skyrmion's topological charge plays an important role, and a transverse Skyrmion motion is observed. Our theory turns out to be in agreement with numerical simulations, both qualitatively and quantitatively. Our calculation indicates that a very promising Skyrmion dynamic phenomenon can be observed in experiments.

  2. Pattern formation in snow during temperature gradient metamorphism

    Science.gov (United States)

    Pinzer, B.; Schneebeli, M.

    2008-12-01

    Temperature gradient metamorphism causes sublimation and growth of crystals. This process causes a dramatic change in thermal and geometrical properties. Using a time-series of snow evolution, we simulated the evolution of the thermal conductivity parallel and perpendicular to the temperature gradient direction. Thermal conductivity changed within a few days from an isotropic property to a strongly anisotropic property. Surprisingly, these changes are only marginally reflected in the geometrical anisotropy of the full snow microstructure. We also observed that the heat flux in the microstructure is concentrated in a small part of the ice matrix, which causes a high tortuosity. The percentage of the ice matrix involved in high heat fluxes was almost constant over time. However, the connectivity of these heat-conducting ice structures increased. The formation of an anisotropic temperature conductivity could have important consequences in terrain where temperature gradients are not perpendicular to the surface, as in shallow snowpacks over hummocky terrain or in boulder areas, or where the snowpack has a strong surface topography, e.g. due to sastrugi formation.

  3. Changing Temperature Gradients Linked to Holocene Moisture Trends in the Northern Hemisphere

    Science.gov (United States)

    Routson, C.; McKay, N.; Kaufman, D. S.; Ault, T.; Rodysill, J. R.

    2016-12-01

    We hypothesize that latitudinal differences in Northern Hemisphere radiative energy balance led to both enhanced hemispheric monsoon strength and mid-latitude aridity during the early-to-mid-Holocene. The width of the Hadley cell and mean position of the subtropical jet stream are influenced by the temperature gradient between the equator and the pole. Climate change is expected to strengthen Hadley circulation while weakening the equator-to-pole temperature gradient, thus shifting the mean position of the subtropical jet northward and causing the sub-tropics to become drier. We analyzed the evolution of Northern Hemisphere latitudinal temperature gradients with moisture in a new compilation of Holocene-length paleoclimate records spanning from 10°S to 90°N latitude. The primary trends in the paleoclimate records agree with future projections showing that weaker early-to-mid Holocene Northern Hemisphere latitudinal temperature gradients (increased warming of the Arctic relative to the equator) are linked to substantial increases in zonally averaged mid-latitude (30°N-55°N) aridity, and simultaneous increases in Northern Hemisphere monsoon strength. These results are significant for current warming, as northern high latitudes are warming faster than the equator, decreasing the equator-to-pole temperature gradient to values comparable with the early Holocene. Our results support model-based projections of increased drought risk in the Northern Hemisphere mid-latitudes in the coming decades.

  4. Migration of liquid phase from the primary/peritectic interface in a temperature gradient

    Science.gov (United States)

    Peng, Peng; Li, XinZhong; Su, YanQing; Guo, JingJie

    2016-07-01

    The migration of the liquid droplets from the primary α/peritectic β interface at the peritectic temperature TP has been observed and analyzed in a Sn-Ni peritectic alloy. During the isothermal annealing stage of the interrupted directional solidification, a concentration gradient is established across the liquid droplets along the direction of the temperature gradient due to the temperature gradient zone melting. Simultaneous remelting/resolidification at the top/bottom of the liquid droplets by this concentration gradient have been confirmed to lead to migration of these droplets towards higher temperatures. The dependence of the migration distance of the liquid droplets on isothermal annealing time has been well predicted. Furthermore, since the lengths of the liquid droplet are not uniform along the direction of the temperature gradient, the remelting/resolidification rates which are dependent on the local morphology of liquid droplet are different at different local positions of the liquid droplets. It has been demonstrated that the morphology of the liquid droplet was also influenced by the morphologies of the liquid phase themselves. Therefore, the morphology of the liquid droplet itself changes from spherical to some kinds of irregular shapes during its migration.

  5. Ultrasonic flowmeters: temperature gradients and transducer geometry effects.

    Science.gov (United States)

    Willatzen, M

    2003-03-01

    Ultrasonic flowmeter performance is addressed for the case of cylindrically shaped flowmeters employing two reciprocal ultrasonic transducers A and B so as to measure time-of-flight differences between signals transmitted from transducer A towards B followed by an equivalent signal transmitted from transducer B towards A. In the case where a liquid flows through the flowmeter's measuring section ("spoolpiece"), the arrival times of the two signals differ by an amount related to the flow passing between the two transducers. Firstly, a detailed study of flow measurement errors with mean flow in the laminar flow regime is carried out as a function of the mode index and the transducer diameter/cylinder diameter ratio in the case where no temperature gradients are present in the flowmeter sensor. It is shown that all modes except the fundamental mode overestimate the mean flow by a factor of 33.33% while excitation of the fundamental mode solely give error-free measurements. The immediate consequences are that the flowmeter error decreases as the transducer diameter/cylinder diameter ratio approaches 1 from 0 reflecting the fact that the excitation level of the fundamental mode increases from almost 0 to 1 as this ratio approaches 1 from 0. Secondly, the effect on flowmeter performance due to flow-induced temperature gradients is examined. It is shown that the presence of temperature gradients leads to flowmeter errors at the higher-flow values even in the case where the fundamental mode is the only mode excited. It is also deduced that flowmeter errors in general depend on the distance between transducers A and B whether temperature gradients exist or not. This conclusion is not reflected in the usual definition of flowmeter errors given by the so-called mode-dependent deviation of measurement introduced in earlier works. Copyright 2002 Elsevier Science B.V.

  6. Estimates of the temperature flux-temperature gradient relation above a sea floor

    NARCIS (Netherlands)

    Cimatoribus, A.; van Haren, H.

    2016-01-01

    The relation between the ux of temperature (or buoyancy), the verti-cal temperature gradient and the height above the bottom, is investigatedin an oceanographic context, using high-resolution temperature measure-ments. The model for the evolution of a strati?ed layer by Balmforthet al. (1998) is

  7. Analyzing community-weighted trait means across environmental gradients: should phylogeny stay or should it go?

    Science.gov (United States)

    Duarte, Leandro D S; Debastiani, Vanderlei Julio; Carlucci, Marcos Bergmann; Diniz-Filho, José Alexandre Felizola

    2017-11-09

    Functional traits mediate ecological responses of organisms to the environment, determining community structure. Community-weighted trait means (CWM) are often used to characterize communities by combining information on species traits and distribution. Relating CWM variation to environmental gradients allows for evaluating species sorting across the metacommunity, either based on correlation tests or ordinary least squares (OLS) models. Yet, it is not clear if phylogenetic signal in both traits and species distribution affect those analyses. On one hand, phylogenetic signal might indicate niche conservatism along clade evolution, reinforcing the environmental signal in trait assembly patterns. On the other hand, it might introduce phylogenetic autocorrelation to mean trait variation among communities. Under this latter scenario, phylogenetic signal might inflate type I error in analysis relating CWM variation to environmental gradients. We explore multiple ways phylogenetic history may influence analysis relating CWM to environmental gradients. We propose the concept of neutral trait diffusion, which predicts that for a functional trait x, CWM variation among local communities does not deviate from the expectation that x evolved according to a neutral evolutionary process. Based on this framework we introduce a graphical tool called neutral trait diffusion representation (NTDR) that allows for the evaluation of whether it is necessary to carry out phylogenetic correction in the trait prior to analyzing the association between CWM and environmental gradients. We illustrate the NTDR approach using simulated traits, phylogenies and metacommunities. We show that even under moderate phylogenetic signal in both the trait used to define CWM and species distribution across communities, OLS models relating CWM variation to environmental gradients lead to inflated type I error when testing the null hypothesis of no association between CWM and environmental gradient. To

  8. Computational analysis of frp composite under different temperature gradient

    Science.gov (United States)

    Gunasekar, P.; Manigandan, S.

    2017-05-01

    Composite material strength depends on the stiffness of fiber and the resin which is used for reinforcement. The strength of the laminate can be increased by applying good manufacturing practices. The strength is directly depending on the property of resin. The property of the any compound subjected to changed when they exposed to the temperature. This paper investigates the strength of laminate when they subjected to different temperature gradient of resin while manufacturing. The resin is preheated before adding hardener with them. These types of laminate reinforced with resin at different levels of temperature 20c, 40c, and 60c. These different temperature resin are used for reinforcement and the specimen tested. The comparative results are made to find how the stiffness of laminate changes with respect to the thermal property of resin. The results are helpful to obtain high strength laminate.

  9. ESTIMATION OF THE CONCRETE PAVEMENT TEMPERATURE FIELDS AND THEIR GRADIENTS

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2015-01-01

    Full Text Available The heat fluxes impact on the road-dressing concrete surfacing under different regions climatic conditions of the construction and maintenance dramatically degrades their solidity, corroding-, shiftingand frost-resistance, and ultimately – the service durability. The source of deformation processes is the character of the gradient temperature fields in the road dressing materials developing with both protracted (static and short run (dynamic heat-and-mass impacts that forward destruction of the pavement surface layers being in contact with free air. In addition, pulsating hydrodynamic pressures appear in the pores of moisture-laden pavement as a result of the vehicular traffic that foster material structure disruption of the surface layers leading to irreversible deformation incipiency (cracks etc.. The authors report of developing a С++ computer program for temperature and gradient fields engineering evaluations of the road dressings made of materials with various surfacing and free-air thermophysical characteristics in line with boundary conditions of the 3rd kind for semi-bounded body. The paper presents the evaluation results in form of graphical curves of the temperature allocation along the surfacing thickness as function of its initial temperature and thermophysical characteristics of the concrete. 

  10. Decoupling of a neutron interferometer from temperature gradients.

    Science.gov (United States)

    Saggu, P; Mineeva, T; Arif, M; Cory, D G; Haun, R; Heacock, B; Huber, M G; Li, K; Nsofini, J; Sarenac, D; Shahi, C B; Skavysh, V; Snow, W M; Werner, S A; Young, A R; Pushin, D A

    2016-12-01

    Neutron interferometry enables precision measurements that are typically operated within elaborate, multi-layered facilities which provide substantial shielding from environmental noise. These facilities are necessary to maintain the coherence requirements in a perfect crystal neutron interferometer which is extremely sensitive to local environmental conditions such as temperature gradients across the interferometer, external vibrations, and acoustic waves. The ease of operation and breadth of applications of perfect crystal neutron interferometry would greatly benefit from a mode of operation which relaxes these stringent isolation requirements. Here, the INDEX Collaboration and National Institute of Standards and Technology demonstrates the functionality of a neutron interferometer in vacuum and characterize the use of a compact vacuum chamber enclosure as a means to isolate the interferometer from spatial temperature gradients and time-dependent temperature fluctuations. The vacuum chamber is found to have no depreciable effect on the performance of the interferometer (contrast) while improving system stability, thereby showing that it is feasible to replace large temperature isolation and control systems with a compact vacuum enclosure for perfect crystal neutron interferometry.

  11. Intrinsic parallel rotation drive by electromagnetic ion temperature gradient turbulence

    CERN Document Server

    Peng, Shuitao; Pan, Yuan

    2016-01-01

    The quasilinear intrinsic parallel flow drive including parallel residual stress, kinetic stress, cross Maxwell stress and parallel turbulent acceleration by electromagnetic ion temperature gradient (ITG) turbulence is calculated analytically using electromagnetic gyrokinetic theory. Both the kinetic stress and cross Maxwell stress also enter the mean parallel flow velocity equation via their divergence, as for the usual residual stress. The turbulent acceleration driven by ion pressure gradient along the total magnetic field (including equilibrium magnetic field and fluctuating radial magnetic field) cannot be written as a divergence of stress, and so should be treated as a local source/sink. All these terms can provide intrinsic parallel rotation drive. Electromagnetic effects reduce the non-resonant electrostatic stress force and even reverse it, but enhance the resonant stress force. Both the non-resonant and resonant turbulent acceleration terms are also enhanced by electromagnetic effects. The possible ...

  12. CO2-gradient measurements using a parallel multi-analyzer setup

    Directory of Open Access Journals (Sweden)

    T. Foken

    2011-03-01

    Full Text Available Accurate CO2 concentration gradient measurements are needed for the computation of advective flux terms, which are part of the full Net Ecosystem Exchange (NEE budget equation. A typical draw back of current gradient measurement designs in advection research is the inadequate sampling of complex flow phenomena using too few observation points in space and time. To overcome this draw back, a new measurement design is presented which allows the parallel measurement of several sampling points at a high frequency. Due to the multi-analyzer nature of the design, inter-instrument bias becomes more of a concern compared to conventional setups. Therefore a statistical approach is presented which allows for accurate observations of concentration gradients, which are typically small in relation to analyzer accuracy, to be obtained. This bias correction approach applies a conditional, time dependent signal correction. The correction depends on a mixing index based on cross correlation analysis, which characterizes the degree of mixing of the atmosphere between individual sample points. The approach assumes statistical properties of probability density functions (pdf of concentration differences between a sample point and the field average which are common to the pdf's from several sample points. The applicability of the assumptions made was tested by Large Eddy Simulation (LES using the model PALM and could be verified for a test case of well mixed conditions. The study presents concentration time series before and after correction, measured at a 2 m height in the sub-canopy at the FLUXNET spruce forest site Waldstein-Weiden-brunnen (DE-Bay, analyzes the dependence of statistical parameters of pdf's from atmospheric parameters such as stratification, quantifies the errors and evaluates the performance of the bias correction approach. The improvements that are achieved by applying the bias correction approach are one order of magnitude larger than possible

  13. Ion temperature gradient modes in toroidal helical systems

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, T. [Graduate University for Advanced Studies, Toki, Gifu (Japan); Sugama, H.; Kanno, R.; Okamoto, M.

    2000-04-01

    Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of {nabla}B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

  14. Cryogenic Temperature-Gradient Foam/Substrate Tensile Tester

    Science.gov (United States)

    Vailhe, Christophe

    2003-01-01

    The figure shows a fixture for measuring the tensile strength of the bond between an aluminum substrate and a thermally insulating polymeric foam. The specimen is meant to be representative of insulating foam on an aluminum tank that holds a cryogenic liquid. Prior to the development of this fixture, tensile tests of this type were performed on foam/substrate specimens immersed in cryogenic fluids. Because the specimens were cooled to cryogenic temperatures throughout their thicknesses, they tended to become brittle and to fracture at loads below true bond tensile strengths. The present fixture is equipped to provide a thermal gradient from cryogenic temperature at the foam/substrate interface to room temperature on the opposite foam surface. The fixture includes an upper aluminum block at room temperature and a lower aluminum block cooled to -423 F (approx. -253 C) by use of liquid helium. In preparation for a test, the metal outer surface (the lower surface) of a foam/substrate specimen is bonded to the lower block and the foam outer surface (the upper surface) of the specimen is bonded to the upper block. In comparison with the through-the-thickness cooling of immersion testing, the cryogenic-to-room-temperature thermal gradient that exists during testing on this fixture is a more realistic approximation of the operational thermal condition of sprayed insulating foam on a tank of cryogenic liquid. Hence, tensile tests performed on this fixture provide more accurate indications of operational bond tensile strengths. In addition, the introduction of the present fixture reduces the cost of testing by reducing the amount of cryogenic liquid consumed and the time needed to cool a specimen.

  15. Temperature dependence of topological susceptibility using gradient flow

    CERN Document Server

    Taniguchi, Yusuke; Kanaya, Kazuyuki; Kitazawa, Masakiyo; Suzuki, Hiroshi; Umeda, Takashi; Iwami, Ryo; Wakabayashi, Naoki

    2016-01-01

    We study temperature dependence of the topological susceptibility with the $N_{f}=2+1$ flavors Wilson fermion. We have two major interests in this paper. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Two definitions are related by the chiral Ward-Takahashi identity but their coincidence is highly non-trivial for the Wilson fermion. By applying the gradient flow both for the gauge and quark fields we find a good agreement of these two measurements. The other is a verification of a prediction of the dilute instanton gas approximation at low temperature region $T_{pc}< T<1.5T_{pc}$, for which we confirm the prediction that the topological susceptibility decays with power $\\chi_{t}\\propto(T/T_{pc})^{-8}$ for three flavors QCD.

  16. The Influence Of Temperature Gradient On Stereological Parameters Of Carbide Phase On Cross-Section Of Abrasive Wear Resistant Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    Studnicki A.

    2015-09-01

    Full Text Available In the paper analysis of temperature gradient and parameters of structure on casting cross-section of abrasive wear resistant chromium cast iron at carbon content of 2,5%wt. and chromium 17%wt. with nickel and molybdenum additives are presented. The castings were made with use of special tester ϕ100mm (method of temperature gradient and derivative analysis with temperature recording in many points from thermal centre to surface (to mould of casting. Registered cooling curves were used to describe the temperature gradient on cross-section of analyzed casting. On the basis of determined curves of temperature gradient measurement fields were selected to make the quantitative studies of structure. The results of studies show significant influence of temperature gradient on quantitative parameters of chromium cast iron structure. Moreover was affirmed that exists a critical temperature gradient for which is present rapid change of quantitative parameters of chromium cast iron structure.

  17. Initial value problem of the toroidal ion temperature gradient mode

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, T.; Sugama, H.; Kanno, R.; Okamoto, M. [National Inst. for Fusion Science, Toki, Gifu (Japan); Horton, W.

    1998-06-01

    The initial value problem of the toroidal ion temperature gradient mode is studied based on the Laplace transform of the ion gyrokinetic equation and the electron Boltzmann relation with the charge neutrality condition. Due to the toroidal magnetic drift, the Laplace-transformed density and potential perturbations have a branch cut as well as poles on the complex-frequency plane. The inverse Laplace transform shows that the temporal evolution of the density and potential perturbations consists of the normal modes and the continuum mode, which correspond to contributions from the poles and the branch cut, respectively. The normal modes have exponential time dependence with the eigenfrequencies determined by the dispersion relation while the continuum mode shows power-law decay oscillation. For the stable case, the long-time asymptotic behavior of the potential and density perturbations is dominated by the continuum mode which decays slower than the normal modes. (author)

  18. Demonstration of capabilities of high temperature composites analyzer code HITCAN

    Science.gov (United States)

    Singhal, Surendra N.; Lackney, Joseph J.; Chamis, Christos C.; Murthy, Pappu L. N.

    1990-01-01

    The capabilities a high temperature composites analyzer code, HITCAN which predicts global structural and local stress-strain response of multilayered metal matrix composite structures, are demonstrated. The response can be determined both at the constituent (fiber, matrix, and interphase) and the structure level and includes the fabrication process effects. The thermo-mechanical properties of the constituents are considered to be nonlinearly dependent on several parameters including temperature, stress, and stress rate. The computational procedure employs an incremental iterative nonlinear approach utilizing a multifactor-interactive constituent material behavior model. Various features of the code are demonstrated through example problems for typical structures.

  19. Dust Eruptions on Mars by Temperature Gradient Induced Forces

    Science.gov (United States)

    Kelling, Thorben; Wurm, G.; Reiss, D.; Kocifaj, M.; Klacka, J.; Teiser, J.

    2009-09-01

    Dust lifting processes on Mars are an active field of investigation. Explanations for dust phenomena even on high elevations on Mars have to be found. In general, wind stress is supposed to be the main lifting process but on average wind velocities are too low. We found, that temperature induced forces are capable of procuring dust ejections and even massive dust eruptions from a dust bed. A Mars soil simulant (JSC Mars 1A) was placed within a vacuum chamber which was evacuated to typical martian pressures of some mbar and particle ejections and eruptions were observed. Several different temperature gradient dependend lifting processes are at work. While e.g. photophoretic and thermophoretic forces only result in minor particle ejections, Knudsen Compressor effects cause continuous and major eruptions. These eruptions are even enhanced if a transition from illumination to no illumination occurs. We argue that the massive transition eruptions may be the dominant dust lifting process for e.g. dust devils. Moving dust devils, which are optically thick, induce a fast transition from light to shadow for the underlying dust bed. Even for lower initial radiation intensities, this will result in particle eruptions. As long as the wind eddy exists, dust devils on Mars may be self sustained even at low pressures or high altitudes. This work recieved support by the DFG and DAAD.

  20. Low temperature magnetic behaviour of glass-covered magnetic microwires with gradient nanocrystalline microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, I. G.; Hernando, A.; Marín, P. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, P.O. Box 155 las Rozas, Madrid 28230 (Spain)

    2014-01-21

    Slow nanocrystallization driving dynamics can be affected by the combination of two factors: sample residual stresses and sample geometry. This effect is evidenced at the initial stages of nanocrystallization of amorphous CoFeSiBCuNb magnetic microwires. Transmission electron microscopy observations indicate how crystallization at temperatures between 730 and 780 K results in a graded microstructure where the crystallization at the surface skin of the microwire, which remains almost amorphous, differs from that of the middle, where elongated grains are observed, and inner regions. However, samples annealed at higher temperatures present a homogeneous microstructure. The effect of gradient microstructure on magnetic properties has been also analyzed and a loss of bistable magnetic behaviour at low temperatures, from that obtained in the amorphous and fully nanocrystallized sample, has been observed and ascribed to changes in sign of magnetostriction for measuring temperatures below 100 K.

  1. An assessment of skin temperature gradients in a tropical primate using infrared thermography and subcutaneous implants.

    Science.gov (United States)

    Thompson, Cynthia L; Scheidel, Caleb; Glander, Kenneth E; Williams, Susan H; Vinyard, Christopher J

    2017-01-01

    Infrared thermography has become a useful tool to assess surface temperatures of animals for thermoregulatory research. However, surface temperatures are an endpoint along the body's core-shell temperature gradient. Skin and fur are the peripheral tissues most exposed to ambient thermal conditions and are known to serve as thermosensors that initiate thermoregulatory responses. Yet relatively little is known about how surface temperatures of wild mammals measured by infrared thermography relate to subcutaneous temperatures. Moreover, this relationship may differ with the degree that fur covers the body. To assess the relationship between temperatures and temperature gradients in peripheral tissues between furred and bare areas, we collected data from wild mantled howling monkeys (Alouatta palliata) in Costa Rica. We used infrared thermography to measure surface temperatures of the furred dorsum and bare facial areas of the body, recorded concurrent subcutaneous temperatures in the dorsum, and measured ambient thermal conditions via a weather station. Temperature gradients through cutaneous tissues (subcutaneous-surface temperature) and surface temperature gradients (surface-ambient temperature) were calculated. Our results indicate that there are differences in temperatures and temperature gradients in furred versus bare areas of mantled howlers. Under natural thermal conditions experienced by wild animals, the bare facial areas were warmer than temperatures in the furred dorsum, and cutaneous temperature gradients in the face were more variable than the dorsum, consistent with these bare areas acting as thermal windows. Cutaneous temperature gradients in the dorsum were more closely linked to subcutaneous temperatures, while facial temperature gradients were more heavily influenced by ambient conditions. These findings indicate that despite the insulative properties of fur, for mantled howling monkeys surface temperatures of furred areas still demonstrate a

  2. Investigation on multilayer failure mechanism of RPV with a high temperature gradient from core meltdown scenario

    Energy Technology Data Exchange (ETDEWEB)

    Jianfeng, Mao, E-mail: jianfeng-mao@163.com [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Xiangqing, Li [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Shiyi, Bao, E-mail: bsy@zjut.edu.cn [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Lijia, Luo [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Zengliang, Gao [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China)

    2016-12-15

    Highlights: • The multilayer failure mechanism is investigated for RPV under CHF. • Failure time and location of RPV are predicted under various SA scenarios. • The structural behaviors are analyzed in depth for creep and plasticity. • The effect of internal pressure and temperature gradient is considered. • The structural integrity of RPV is secured within the required 72 creep hours. - Abstract: The Fukushima accident shows that in-vessel retention (IVR) of molten core debris has not been appropriately assessed, and a certain pressure (up to 8.0 MPa) still exists inside the reactor pressure vessel (RPV). In the traditional concept of IVR, the pressure is supposed to successfully be released, and the temperature distributed among the wall thickness is assumed to be uniform. However, this concept is seriously challenged by reality of Fukushima accident with regard to the existence of both internal pressure and high temperature gradient. Therefore, in order to make the IVR mitigation strategy succeed, the numerical investigation of the lower head behavior and its failure has been performed for several internal pressures under high temperature gradient. According to some requirements in severe accident (SA) management of RPV, it should be ensured that the IVR mitigation takes effect in preventing the failure of the structure within a period of 72 h. Subsequently, the failure time and location have to be predicted under the critical heat flux (CHF) loading condition for lower head, since the CHF is limit thermal boundary before the melt-through of RPV. In illustrating the so called ‘multilayer failure mechanism’, the structural behaviors of RPV are analyzed in terms of the stress, creep strain, deformation, damage on selected paths.

  3. The change of temperature gradient in solidification of hypereutectic chromium cast iron casting

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2010-01-01

    Full Text Available In article the analysis of temperature gradient of solidification in section of hypereutectic chromium cast iron model casting was introduced. On this example was presented the method (DTGA – derivative and thermal gradient analysis, which was worked out in Department of Foundry Silesian University of Technology enabling the record of indispensable data to execution of analysis the temperature gradient and its derivative after time on section of model casting. It multichanneled apparatus to registration of data was used Crystaldigraph - PC.

  4. Parallelism between gradient temperature raman spectroscopy and differential scanning calorimetry results

    Science.gov (United States)

    Temperature dependent Raman spectroscopy (TDR) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur just prior to phase transitions. Herein we apply TDR and D...

  5. The temperature gradient on section of casting in process of primary crystallization of chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2008-08-01

    Full Text Available The methodology of defining in article was introduced the temperature gradient in process of primary crystallization during cooling the casting from chromium cast iron on basis of measurements of thermal field in test DTA-K3. Insert also the preliminary results of investigations of influence temperature gradient on structure of studied wear resistance chromium cast iron.

  6. Temperature Versus Salinity Gradients Below the Ocean Mixed Layer

    Science.gov (United States)

    2012-05-03

    13] The effects of density compensated gradients below the mixed layer are not limited to ocean circulation and cli- mate. Since sound speed and...The Impact of Spice on Ocean circulation . The second is the 6.2 program element 62435N Full Column Mixing for Numerical Ocean Models. The authors would...and F. Paparella (2003), Compensation and alignment of thermohaline gradients in the ocean mixed layer, J. Phys. Oceanogr., 33, 2214–2223, doi

  7. MHD thermosolutal marangoni convection heat and mass transport of power law fluid driven by temperature and concentration gradient

    Directory of Open Access Journals (Sweden)

    Chengru Jiao

    2015-08-01

    Full Text Available This paper studies the magnetohydrodynamic (MHD thermosolutal Marangoni convection heat and mass transfer of power-law fluids driven by a power law temperature and a power law concentration which is assumed that the surface tension varies linearly with both the temperature and concentration. Heat and mass transfer constitutive equation is proposed based on N-diffusion proposed by Philip and the abnormal convection-diffusion model proposed by Pascal in which we assume that the heat diffusion depends non-linearly on both the temperature and the temperature gradient and the mass diffusion depends non-linearly on both the concentration and the concentration gradient with modified Fourier heat conduction for power law fluid. The governing equations are reduced to nonlinear ordinary differential equations by using suitable similarity transformations. Approximate analytical solution is obtained using homotopy analytical method (HAM. The transport characteristics of velocity, temperature and concentration fields are analyzed in detail.

  8. Measurement of water transfer and swelling stress in the buffer material due to temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, H. [ITC, Tokai, Ibaraki (Japan); Chijimatsu, M.; Fujita, A.

    1999-03-01

    Coefficients concerning the water transfer in the buffer material was obtained by empirically giving a temperature gradient, and the swelling stress was measured when water was soaked in the sample under the uniform temperature and temperature gradient conditions. The distributions of temperature and water in the buffer material empirically given a temperature gradient were measured to deduce water diffusion constant due to the temperature gradient. The diffusion constant was the order of 10{sup -8} cm{sup 2}/s/degC. As a result of a equitemperature soaking test, it was found that the swelling stress of the part where soaktion was slow was greater than that of the part with fast soaking at a stage of non-uniform water distribution. The water soaking quantity to the sample and swelling stress reached a stationary state after 7000 hours and the water distribution in the whole sample was found saturated. (H. Baba)

  9. Idealized modeling of convective organization with changing sea surface temperatures using multiple equilibria in weak temperature gradient simulations

    Science.gov (United States)

    Sentić, Stipo; Sessions, Sharon L.

    2017-06-01

    The weak temperature gradient (WTG) approximation is a method of parameterizing the influences of the large scale on local convection in limited domain simulations. WTG simulations exhibit multiple equilibria in precipitation; depending on the initial moisture content, simulations can precipitate or remain dry for otherwise identical boundary conditions. We use a hypothesized analogy between multiple equilibria in precipitation in WTG simulations, and dry and moist regions of organized convection to study tropical convective organization. We find that the range of wind speeds that support multiple equilibria depends on sea surface temperature (SST). Compared to the present SST, low SSTs support a narrower range of multiple equilibria at higher wind speeds. In contrast, high SSTs exhibit a narrower range of multiple equilibria at low wind speeds. This suggests that at high SSTs, organized convection might occur with lower surface forcing. To characterize convection at different SSTs, we analyze the change in relationships between precipitation rate, atmospheric stability, moisture content, and the large-scale transport of moist entropy and moisture with increasing SSTs. We find an increase in large-scale export of moisture and moist entropy from dry simulations with increasing SST, which is consistent with a strengthening of the up-gradient transport of moisture from dry regions to moist regions in organized convection. Furthermore, the changes in diagnostic relationships with SST are consistent with more intense convection in precipitating regions of organized convection for higher SSTs.

  10. Analyze the optimal solutions of optimization problems by means of fractional gradient based system using VIM

    Directory of Open Access Journals (Sweden)

    Firat Evirgen

    2016-04-01

    Full Text Available In this paper, a class of Nonlinear Programming problem is modeled with gradient based system of fractional order differential equations in Caputo's sense. To see the overlap between the equilibrium point of the fractional order dynamic system and theoptimal solution of the NLP problem in a longer timespan the Multistage Variational İteration Method isapplied. The comparisons among the multistage variational iteration method, the variationaliteration method and the fourth order Runge-Kutta method in fractional and integer order showthat fractional order model and techniques can be seen as an effective and reliable tool for finding optimal solutions of Nonlinear Programming problems.

  11. Response of Soft Continuous Structures and Topological Defects to a Temperature Gradient

    Science.gov (United States)

    Kurita, Rei; Mitsui, Shun; Tanaka, Hajime

    2017-09-01

    Thermophoresis, which is mass transport induced by a temperature gradient, has recently attracted considerable attention as a new way to transport materials. So far the study has been focused on the transport of discrete structures such as colloidal particles, proteins, and polymers in solutions. However, the response of soft continuous structures such as membranes and gels to a temperature gradient has been largely unexplored. Here we study the behavior of a lamellar phase made of stacked surfactant bilayer membranes under a temperature gradient. We find the migration of membranes towards a low-temperature region, causing the increase in the degree of membrane undulation fluctuations towards that direction. This is contrary to our intuition that the fluctuations are weaker at a lower temperature. We show that this can be explained by temperature-gradient-induced migration of membranes under the topological constraint coming from the connectivity of each membrane. We also reveal that the pattern of an edge dislocation array formed in a wedge-shaped cell can be controlled by a temperature gradient. These findings suggest that application of a temperature gradient provides a novel way to control the organization of soft continuous structures such as membranes, gels, and foams, in a manner essentially different from the other types of fields, and to manipulate topological defects.

  12. Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, A. G.; Rath, F.; Buchholz, R.; Grosshauser, S. R.; Strintzi, D.; Weikl, A. [Physics Department, University of Bayreuth, Universitätsstrasse 30, Bayreuth (Germany); Camenen, Y. [Aix Marseille Univ, CNRS, PIIM, UMR 7345, Marseille (France); Candy, J. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Casson, F. J. [CCFE, Culham Science Centre, Abingdon OX14 3DB, Oxon (United Kingdom); Hornsby, W. A. [Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching (Germany)

    2016-08-15

    It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.

  13. Nonlinear gyrokinetic simulations of ion-temperature-gradient turbulence for the optimized Wendelstein 7-X stellarator.

    Science.gov (United States)

    Xanthopoulos, P; Merz, F; Görler, T; Jenko, F

    2007-07-20

    Ion-temperature-gradient turbulence constitutes a possibly dominant transport mechanism for optimized stellarators, in view of the effective suppression of neoclassical losses characterizing these devices. Nonlinear gyrokinetic simulation results for the Wendelstein 7-X stellarator [G. Grieger, in (IAEA, Vienna, 1991) Vol. 3, p. 525]-assuming an adiabatic electron response-are presented. Several fundamental features are discussed, including the role of zonal flows for turbulence saturation, the resulting flux-gradient relationship, and the coexistence of ion-temperature-gradient modes with trapped ion modes in the saturated state.

  14. Bifurcation Theory of the Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, R.A.; Krommes, J.A.

    2005-09-22

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  15. Influence of temperature gradients on charge transport in asymmetric nanochannels

    NARCIS (Netherlands)

    Benneker, Anne M.; Wendt, Hans David; Lammertink, Rob G.H.; Wood, Jeffery A.

    2017-01-01

    Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge

  16. Selective entrainment of the Drosophila circadian clock to daily gradients in environmental temperature

    Directory of Open Access Journals (Sweden)

    Goda Tadahiro

    2009-08-01

    Full Text Available Abstract Background Circadian clocks are internal daily time keeping mechanisms that allow organisms to anticipate daily changes in their environment and to organize their behavior and physiology in a coherent schedule. Although circadian clocks use temperature compensation mechanisms to maintain the same pace over a range of temperatures, they are also capable of synchronizing to daily temperature cycles. This study identifies key properties of this process. Results Gradually ramping daily temperature cycles are shown here to synchronize behavioral and molecular daily rhythms in Drosophila with a remarkable efficiency. Entrainment to daily temperature gradients of amplitudes as low as 4°C persisted even in the context of environmental profiles that also included continuous gradual increases or decreases in absolute temperature. To determine which elements of daily temperature gradients acted as the key determinants of circadian activity phase, comparative analyses of daily temperature gradients with different wave forms were performed. The phases of ascending and descending temperature acted together as key determinants of entrained circadian phase. In addition, circadian phase was found to be modulated by the relative temperature of release into free running conditions. Release at or close to the trough temperature of entrainment consistently resulted in phase advances. Re-entrainment to daily temperature gradients after large phase shifts occurred relatively slowly and required several cycles, allowing flies to selectively respond to periodic rather than anecdotal signals. The temperature-entrained phase relationship between clock gene expression rhythms and locomotor activity rhythms strongly resembled that previously observed for light entrainment. Moreover, daily temperature gradient and light/dark entrainment reinforced each other if the phases of ascending and descending temperature were in their natural alignment with the light and

  17. Dynamic microscale temperature gradient in a gold nanorod solution measured by diffraction-limited nanothermometry

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengmingyue; Gan, Xiaosong; Li, Xiangping; Gu, Min, E-mail: mgu@swin.edu.au [Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)

    2015-09-21

    We quantify the dynamic microscale temperature gradient in a gold nanorod solution using quantum-dot-based microscopic fluorescence nanothermometry. By incorporating CdSe quantum dots into the solution as a nanothermometer, precise temperature mapping with diffraction-limited spatial resolution and sub-degree temperature resolution is achieved. The acquired data on heat generation and dissipation show an excellent agreement with theoretical simulations. This work reveals an effective approach for noninvasive temperature regulation with localized nanoheaters in microfluidic environment.

  18. Physical-chemical quality of onion analyzed under drying temperature

    Science.gov (United States)

    Djaeni, M.; Arifin, U. F.; Sasongko, S. B.

    2017-03-01

    Drying is one of conventional processes to enhance shelf life of onion. However, the active compounds such as vitamin and anthocyanin (represented in red color), degraded due to the introduction of heat during the process. The objective of this research was to evaluate thiamine content as well as color in onion drying under different temperature. As an indicator, the thiamine and color was observed every 30 minutes for 2 hours. Results showed that thiamine content and color were sensitvely influenced by the temperature change. For example, at 50°C for 2 hours drying process, the thiamine degradation was 55.37 %, whereas, at 60°C with same drying time, the degradation was 74.01%. The quality degradation also increased by prolonging drying time.

  19. Multiple-Point Temperature Gradient Algorithm for Ring Laser Gyroscope Bias Compensation.

    Science.gov (United States)

    Li, Geng; Zhang, Pengfei; Wei, Guo; Xie, Yuanping; Yu, Xudong; Long, Xingwu

    2015-11-30

    To further improve ring laser gyroscope (RLG) bias stability, a multiple-point temperature gradient algorithm is proposed for RLG bias compensation in this paper. Based on the multiple-point temperature measurement system, a complete thermo-image of the RLG block is developed. Combined with the multiple-point temperature gradients between different points of the RLG block, the particle swarm optimization algorithm is used to tune the support vector machine (SVM) parameters, and an optimized design for selecting the thermometer locations is also discussed. The experimental results validate the superiority of the introduced method and enhance the precision and generalizability in the RLG bias compensation model.

  20. The relation between temperature and concentration gradients in superfluid sup 3 He- sup 4 He solutions

    CERN Document Server

    Zadorozhko, A A; Rudavskij, E Y; Chagovets, V K; Sheshin, G A

    2003-01-01

    The temperature and concentration gradients nabla T and nabla x in a superfluid sup 3 He- sup 4 He mixture with an initial concentration 9,8 % of sup 3 He are measured in a temperature range 70-500 mK. The gradients are produced by a steady thermal flow with heating from below. It is shown that the value of nabla x/nabla T observed in the experiment is in good agreement with the theoretical model derived from the temperature and concentration dependences of osmotic pressure. The experimental data permitted us to obtain a thermal diffusion ratio of the solution responsible for the thermal diffusion coefficient.

  1. TEMPERATURE SELECTION BY HATCHLING AND YEARLING FLORIDA RED-BELLIED TURTLES (PSEUDEMYS NELSONI) IN THERMAL GRADIENTS

    Science.gov (United States)

    We tested hatchling and yearling Florida red-bellied turtles (Pseudemys nelsoni) in laboratory thermal gradient chambers to determine if they would prefer particular temperatures. Most 1995 hatchlings selected the highest temperature zone of 27degrees C (Test 1) and 30 degrees ...

  2. Parametric analysis of temperature gradient across thermoelectric power generators

    Directory of Open Access Journals (Sweden)

    Khaled Chahine

    2016-06-01

    Full Text Available This paper presents a parametric analysis of power generation from thermoelectric generators (TEGs. The aim of the parametric analysis is to provide recommendations with respect to the applications of TEGs. To proceed, the one-dimensional steady-state solution of the heat diffusion equation is considered with various boundary conditions representing real encountered cases. Four configurations are tested. The first configuration corresponds to the TEG heated with constant temperature at its lower surface and cooled with a fluid at its upper surface. The second configuration corresponds to the TEG heated with constant heat flux at its lower surface and cooled with a fluid at its upper surface. The third configuration corresponds to the TEG heated with constant heat flux at its lower surface and cooled by a constant temperature at its upper surface. The fourth configuration corresponds to the TEG heated by a fluid at its lower surface and cooled by a fluid at its upper surface. It was shown that the most promising configuration is the fourth one and temperature differences up to 70˚C can be achieved at 150˚C heat source. Finally, a new concept is implemented based on configuration four and tested experimentally.

  3. Formation and texture of Bi-2223 phase during sintering in a temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X.Y.; Nagata, A.; Watanabe, K.; Nojima, T.; Sugawara, K.; Hanada, S.; Kamada, S

    2004-10-01

    The formation and texture of Bi-2223 phase during sintering in a temperature gradient were investigated. Co-precipitated powders with the composition of Bi:Pb:Sr:Ca:Cu=1.85:0.35:1.90:2.05:3.05 were used. Samples set on a silver holder were sintered at 850 deg. C for 120 h in a vertical tube furnace with a temperature gradient of 15 deg. C/cm installed in a solenoid-type superconducting magnet. A vertical magnetic field can be applied parallel to the long axis of the furnace. It has been found that the Bi-2223 grains with their c-axis parallel to the axial direction of the vertical tube furnace are formed not only on the surface, but also in the center of the sample sintered at 850 deg. C for 120 h in 15 deg. C/cm temperature gradient without magnetic field. Moreover, the sample sintered in the temperature gradient and in a 10 T magnetic field have a stronger c-axis alignment of Bi-2223 phase. It is suggested that both the temperature gradient and magnetic field during sintering are favorable for the c-axis alignment of Bi-2223 phase.

  4. Seasonal evolution of snow permeability under equi-temperature and temperature-gradient conditions

    Directory of Open Access Journals (Sweden)

    F. Domine

    2013-12-01

    Full Text Available The permeability (K of snow to air flow affects the transfer of energy, water vapor and chemical species between the snow and the atmosphere. Yet today little is known about the temporal evolution of snow permeability as a function of metamorphic regime. Furthermore, our ability to simulate snow permeability over the seasonal evolution of a snowpack has not been tested. Here we have measured the evolution of snow permeability in a subarctic snowpack subject to high temperature-gradient (TG metamorphism. We have also measured the evolution of the same snowpack deposited over tables so that it evolved in the equi-temperature (ET regime. Permeability varies in the range 31 × 10−10 (ET regime to 650 × 10−10 m2 (TG regime. Permeability increases over time in TG conditions and decreases under ET conditions. Using measurements of density ρ and of specific surface area (SSA, from which the equivalent sphere radius r is determined, we show that the equation linking SSA, density ρ and permeability, K = 3.0 r2 e(−0.013 ρ (with K in m2, r in m and ρ in kg m−3 obtained in a previous study adequately predicts permeability values. The detailed snowpack model Crocus is used to simulate the physical properties of the TG and ET snowpacks. For the most part, all variables are well reproduced. Simulated permeabilities are up to a factor of two greater than measurements for depth hoar layers, which we attribute to snow microstructure and its aerodynamic properties. Finally, the large difference in permeabilities between ET and TG metamorphic regimes will impact atmosphere-snow energy and mass exchanges. These effects deserve consideration in predicting the effect of climate change on snow properties and snow–atmosphere interactions.

  5. Temperature gradient measurements by using thermoelectric effect in CNTs-silicone adhesive composite.

    Directory of Open Access Journals (Sweden)

    Muhammad Tariq Saeed Chani

    Full Text Available This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT and silicone adhesive. The composite contains CNT and silicon adhesive 1∶1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results.

  6. Germination responses to current and future temperatures of four seeder shrubs across a latitudinal gradient in western Iberia.

    Science.gov (United States)

    Chamorro, Daniel; Luna, Belén; Moreno, José M

    2017-01-01

    Species differ in their temperature germination niche. Populations of a species may similarly differ across the distribution range of the species. Anticipating the impacts of climate variability and change requires understanding the differential sensitivity to germination temperature among and within species. Here we studied the germination responses of four hard-seeded Cistaceae seeders to a range of current and future temperatures. Seeds were collected at sites across the Iberian Peninsula and exposed or not exposed to a heat shock to break dormancy, then set to germinate under four temperature regimes. Temperatures were varied daily and seasonally, simulating the temperature range across the gradient, plus an increased temperature simulating future climate. Time to germination onset and cumulative germination at the end of each season were analyzed for the effects of temperature treatments, seasons, and local climate (temperature of the germination period, Tgp) at each site. Tgp was a significant covariate of germination in all species but Cistus populifolius. Temperature treatments significantly affected Cistus ladanifer, C. salviifolius, and Halimium ocymoides. Germination occurred in simulated autumn conditions, with little germination occurring at later seasons, except in unheated seeds of H. ocymoides. Exposure to a heat shock changed the sensitivity to temperature treatments and the relationships with Tgp. Germination responses to temperature differ not only among species but also within species across their latitudinal range. The responses were idiosyncratic and related to the local climate of the population. This germination variability complicates generalizing the impacts of climate variability and climate change. © 2017 Botanical Society of America.

  7. Customised spatiotemporal temperature gradients created by a liquid metal enabled vortex generator.

    Science.gov (United States)

    Zhu, Jiu Yang; Thurgood, Peter; Nguyen, Ngan; Ghorbani, Kamran; Khoshmanesh, Khashayar

    2017-11-07

    Generating customised temperature gradients in miniaturised flow-free liquid chambers is challenging due to the dominance of diffusion. Inducing internal flows in the form of vortices is an effective strategy for overcoming the limitations of diffusion in such environments. Vortices can be produced by applying pressure, temperature and electric potential gradients via miniaturised actuators. However, the difficulties associated with the fabrication, integration, maintenance and operation of such actuators hinder their utility. Here, we utilise liquid metal enabled pumps to induce vortices inside a miniaturised liquid chamber. The configuration and rotational velocity of these vortices can be controlled by tuning the polarity and frequency of the energising electrical signal. This allows creation of customised spatial temperature gradients inside the chamber. The absence of conventional moving elements in the pumps facilitates the rapid reconfiguration of vortices. This enables quick transition from one temperature profile to another, and creates customised spatiotemporal temperature gradients. This allows temperature oscillation from 35 to 62 °C at the hot spot, and from 25 to 27 °C at the centre of the vortex within 15 seconds. Our liquid metal enabled vortex generator can be fabricated, integrated and operated easily, and offers opportunities for studying thermo-responsive materials and biological samples.

  8. Large concentration changes due to thermal diffusion effects in gas flow microsystems with temperature gradients

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Johannessen, Tue; Jensen, Søren

    Thermal diffusion, or Sorét diffusion, is shown to cause significant concentration changes and transients in gas flow microsystems with temperature gradients. In a silicon microsystem, a temperature gradient of about 100 oC/mm is measured to produce concentration transients of up to 13.......7 % in an argon/helium mixture, when the flow is abruptly changed from a high value to a low value. Finite element simulations of the thermal diffusion in a geometry similar to the experimental setup reproduce the measurements....

  9. Glass-transition temperature gradient in nanocomposites: evidence from nuclear magnetic resonance and differential scanning calorimetry.

    Science.gov (United States)

    Papon, Aurélie; Montes, Hélène; Hanafi, Mohamed; Lequeux, François; Guy, Laurent; Saalwächter, Kay

    2012-02-10

    The slowing-down of the dynamics of a polymer chain near a surface has been observed for many years now. Here we show that the behavior of model nanocomposites can be quantitatively described with a gradient of glass-transition temperature. We describe with a single parameter-the range of this gradient-the temperature and solvent effect on the spin relaxation dynamics. Moreover, this parameter allows a quantitative description of the nanocomposite calorimetric response from the one of the bulk polymer.

  10. Comparison of the temperature accuracy between smart phone based and high-end thermal cameras using a temperature gradient phantom

    Science.gov (United States)

    Klaessens, John H.; van der Veen, Albert; Verdaasdonk, Rudolf M.

    2017-03-01

    Recently, low cost smart phone based thermal cameras are being considered to be used in a clinical setting for monitoring physiological temperature responses such as: body temperature change, local inflammations, perfusion changes or (burn) wound healing. These thermal cameras contain uncooled micro-bolometers with an internal calibration check and have a temperature resolution of 0.1 degree. For clinical applications a fast quality measurement before use is required (absolute temperature check) and quality control (stability, repeatability, absolute temperature, absolute temperature differences) should be performed regularly. Therefore, a calibrated temperature phantom has been developed based on thermistor heating on both ends of a black coated metal strip to create a controllable temperature gradient from room temperature 26 °C up to 100 °C. The absolute temperatures on the strip are determined with software controlled 5 PT-1000 sensors using lookup tables. In this study 3 FLIR-ONE cameras and one high end camera were checked with this temperature phantom. The results show a relative good agreement between both low-cost and high-end camera's and the phantom temperature gradient, with temperature differences of 1 degree up to 6 degrees between the camera's and the phantom. The measurements were repeated as to absolute temperature and temperature stability over the sensor area. Both low-cost and high-end thermal cameras measured relative temperature changes with high accuracy and absolute temperatures with constant deviations. Low-cost smart phone based thermal cameras can be a good alternative to high-end thermal cameras for routine clinical measurements, appropriate to the research question, providing regular calibration checks for quality control.

  11. Eocene high-latitude temperature gradients over time and space based on d18O values of fossil shark teeth

    Science.gov (United States)

    Zeichner, S. S.; Kim, S.; Colman, A. S.

    2015-12-01

    Early-Mid Eocene (56.0-33.9Mya) is characterized by a temperate Antarctic climate and shallower latitudinal temperature gradients than those in present day. The warmer waters off the coast of the Antarctic Peninsula provided suitable habitats for taxa (i.e., sharks) that live today at lower latitudes. Stable isotope analysis of Eocene shark teeth provides a proxy to understand high latitude temperature gradients. However, shark ecology, in particular migration and occupation of tidal versus pelagic habitats, must be considered in the interpretation of stable isotope data. In this study, we analyze d18OPO4 values from the enameloid of Striatolamia (synonymized with Carcharias) shark teeth from the La Meseta formation (Seymour Island, Antarctica) to estimate paleotemperature in Early-Mid Eocene Antarctica, and assess the impact of ecology versus environmental signals on d18OPO4 values. We compare the ranges and offsets between our measured shark tooth d18OPO4 and published bivalve d18OCO3 values to test whether shark teeth record signals of migration across latitudinal temperature gradients, or instead reflect seasonal and long-term temporal variation across La Meseta stratigraphic units.

  12. Prediction of Pressure and Temperature Gradients in the Tokamak Plasma Edge

    Science.gov (United States)

    Stacey, W. M.

    2017-10-01

    An extended plasma fluid theory that takes into account kinetic ion orbit loss and electromagnetic forces in the continuity, momentum and energy balances, as well as atomic physics and radiation, has been used to reveal the explicit dependence of the temperature and pressure gradients in the tokamak edge plasma on these various factors. Combining the ion radial momentum balance and the Ohm's Law expression for Er reveals the dependence of the radial ion pressure gradient on VxB forces driven by radial particle fluxes, which depend on ion orbit loss, and other factors. The strong temperature gradients measured in the H-mode edge pedestal could certainly be associated with radiative and atomic physics edge cooling effects and the strong reduction in ion and energy fluxes due to ion orbit loss, as well as to the possible reductions in thermal diffusivities that is usually assumed to be the cause. Work supported by USDOE under DE-FC02-04ER54698.

  13. Effects of temperature-gradient-induced damage of zirconia metering nozzles

    Science.gov (United States)

    Zhao, Liang; Xue, Qun-hu

    2017-09-01

    The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ray diffraction and scanning electron microscopy after the samples were subjected to a heat treatment based on the temperatures of the affected, transition, and original layers of zirconia metering nozzles during the continuous casting of steel. The results showed that, after heat treatment at 1540, 1410, or 1300°C for a dwell time of 5 h, the monoclinic zirconia phase was gradually stabilized with increasing heat-treatment temperature. Moreover, a transformation to the cubic zirconia phase occurred, accompanied by grain growth, which illustrates that the temperature gradient in zirconia metering nozzles affects the mineral composition and microstructure of the nozzles and accelerates damage, thereby deteriorating the quality and service life of the nozzles.

  14. PHYSIOLOGICAL RESPONSES OF ECKLONIA RADIATA (LAMINARIALES) TO A LATITUDINAL GRADIENT IN OCEAN TEMPERATURE

    DEFF Research Database (Denmark)

    Stæhr, Peter Anton; Wernberg, Thomas

    2009-01-01

    and nutrients decreased with increasing ocean temperature. Concurrently, a number of gradual changes in the metabolic balance of E. radiata took place along the latitudinal gradient. Warm-acclimatized kelps had 50% lower photosynthetic rates and 90% lower respiration rates at the optimum temperature than did......We tested the ability of sporophytes of a small kelp, Ecklonia radiata (C. Agardh) J. Agardh, to adjust their photosynthesis, respiration, and cellular processes to increasingly warm ocean climates along a latitudinal gradient in ocean temperature (~4°C). Tissue concentrations of pigment...... cool-acclimatized kelps. A reduction in temperature sensitivity was also observed as a reduction in Q10-values from cool- to warm-acclimatized kelps for gross photosynthesis (Q10: 3.35 to 1.45) and respiration (Q10: 3.82 to 1.65). Respiration rates were more sensitive to increasing experimental...

  15. Measurement and Calculation of Vertical Temperature Gradients in Rooms with Convective Flows

    DEFF Research Database (Denmark)

    Overby, H.

    The paper deals with experimental and theoretical examinations of the vertical temperature gradient in rooms with convective flows under transient conditions. The measurements are carried out in a laboratory test room of three different sizes. A small room (7.25 m2) with a normal room height of 2...

  16. Convective cells of internal gravity waves in the earth's atmosphere with finite temperature gradient

    Directory of Open Access Journals (Sweden)

    O. Onishchenko

    2013-03-01

    Full Text Available In this paper, we have investigated vortex structures (e.g. convective cells of internal gravity waves (IGWs in the earth's atmosphere with a finite vertical temperature gradient. A closed system of nonlinear equations for these waves and the condition for existence of solitary convective cells are obtained. In the atmosphere layers where the temperature decreases with height, the presence of IGW convective cells is shown. The typical parameters of such structures in the earth's atmosphere are discussed.

  17. Plasma membrane temperature gradients and multiple cell permeabilization induced by low peak power density femtosecond lasers

    Directory of Open Access Journals (Sweden)

    Allen L. Garner

    2016-03-01

    Full Text Available Calculations indicate that selectively heating the extracellular media induces membrane temperature gradients that combine with electric fields and a temperature-induced reduction in the electropermeabilization threshold to potentially facilitate exogenous molecular delivery. Experiments by a wide-field, pulsed femtosecond laser with peak power density far below typical single cell optical delivery systems confirmed this hypothesis. Operating this laser in continuous wave mode at the same average power permeabilized many fewer cells, suggesting that bulk heating alone is insufficient and temperature gradients are crucial for permeabilization. This work suggests promising opportunities for a high throughput, low cost, contactless method for laser mediated exogenous molecule delivery without the complex optics of typical single cell optoinjection, for potential integration into microscope imaging and microfluidic systems.

  18. Space charge build-up in XLPE-cable with temperature gradient

    DEFF Research Database (Denmark)

    Holbøll, Joachim; Henriksen, Mogens; Hjerrild, Jesper

    2000-01-01

    and temperatures were applied in the 20 - 80°C range with gradients across the insulation of up to 15°C. In this paper, the observed charge phenomena in the bulk and at the interfaces are related to the external conditions, in particular to the temperature gradient. The measured space charge distributions......Space charge build-up in standard XLPE insulated AC cables has been studied under varying temperature and field conditions. The cables were triple-extruded with the inner semicon on a solid aluminum conductor, 5.5mm XLPE-insulation and an outer semicon. The cables were stressed up to 15kV/mm DC...

  19. Flow regimes in a shallow rotating cylindrical annulus with temperature gradients imposed on the horizontal boundaries

    Science.gov (United States)

    Hathaway, D. H.; Fowlis, W. W.

    1986-01-01

    Experimental flow regime diagrams are determined for a new rotating cylindrical annulus configuration which permits a measure of control over the internal vertical temperature gradient. The new annulus has radial temperature gradients imposed on plane horizontal thermally conducting endwalls (with the cylindrical sidewalls as insulators) and is considered to be more relevant to atmospheric dynamics studies than the classical cylindrical annulus. Observations have revealed that, in addition to the axisymmetric flow and nonaxisymmetric baroclinic wave flow which occur in the classical annulus, two additional nonaxisymmetric flow types occur in the new annulus: boundary-layer thermal convection and deep thermal convection. Flow regime diagrams for three different values of the imposed vertical temperature difference are presented, and explanations for the flow transitions are offered. The new annulus provides scientific backup for the proposed Atmospheric General Circulation Experiment for Spacelab. The apparatus diagram is included.

  20. Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient

    Science.gov (United States)

    Zinke, J.; Hoell, A.; Lough, J. M.; Feng, M.; Kuret, A. J.; Clarke, H.; Ricca, V.; Rankenburg, K.; McCulloch, M. T.

    2015-10-01

    Increasing intensity of marine heatwaves has caused widespread mass coral bleaching events, threatening the integrity and functional diversity of coral reefs. Here we demonstrate the role of inter-ocean coupling in amplifying thermal stress on reefs in the poorly studied southeast Indian Ocean (SEIO), through a robust 215-year (1795-2010) geochemical coral proxy sea surface temperature (SST) record. We show that marine heatwaves affecting the SEIO are linked to the behaviour of the Western Pacific Warm Pool on decadal to centennial timescales, and are most pronounced when an anomalously strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña's. This SST gradient forces large-scale changes in heat flux that exacerbate SEIO heatwaves. Better understanding of the zonal SST gradient in the Western Pacific is expected to improve projections of the frequency of extreme SEIO heatwaves and their ecological impacts on the important coral reef ecosystems off Western Australia.

  1. Interplay between temperature gradients field and C - E transformation in solidifying rolls

    Directory of Open Access Journals (Sweden)

    W. Wołczyński

    2009-07-01

    Full Text Available At first step of simulation a temperature field for solidifying cast steel and cast iron roll has been performed. The calculation does not take into account the convection in the liquid since convection has no influence on the proposed model for the localization of the C-E (columnar to equiaxed grains transformation. However, it allows to study the dynamics of temperature field temporal behavior in the middle of a mould. It is postulated that for the C-E transition a full accumulation of the heat in the mould has been observed (plateau at the T(t curve. The temporal range of plateau existence corresponds to the incubation time for the full equiaxed grains formation. At the second step of simulation temporal behavior of the temperature gradient field has been studied. Three ranges within temperature gradients field have been distinguished for the operating point situated at the middle of mould: a/ for the formation of columnar grains zone, ( and high temperature gradient 0>>T&0//>>∂∂−∂∂∂∂−∂∂>EttEtrTrT. T - temperature, r - roll radius. It is evident that the heat transfer across the mould decides on the temporal appearance of incubation during which the solidification is significantly arrested and competition between columnar and equiaxed growth occurs. Moreover solidification with positive temperature gradient transforms into solidification with negative temperature gradient (locally after the incubation. A simulation has been performed for the cast steel and cast iron rolls solidifying as in industry condition. Since the incubation divides the roll into to parts (first with columnar structure, second with equiaxed structure some experiments dealing with solidification have been made in laboratory scale. Finally, observations of the macrosegregation or microsegregation and phase or structure appearance in the cast iron ingot / roll (made in laboratory has also been done in order to confront them with theoretical predictions

  2. The effects of sea surface temperature gradients on surface turbulent fluxes

    Science.gov (United States)

    Steffen, John

    A positive correlation between sea surface temperature (SST) and wind stress perturbation near strong SST gradients (DeltaSST) has been observed in different parts of the world ocean, such as the Gulf Stream in the North Atlantic and the Kuroshio Extension east of Japan. These changes in winds and SSTs can modify near-surface stability, surface stress, and latent and sensible heat fluxes. In general, these small scale processes are poorly modeled in Numerical Weather Prediction (NWP) and climate models. Failure to account for these air--sea interactions produces inaccurate values of turbulent fluxes, and therefore a misrepresentation of the energy, moisture, and momentum budgets. Our goal is to determine the change in these surface turbulent fluxes due to overlooking the correlated variability in winds, SSTs, and related variables. To model these air--sea interactions, a flux model was forced with and without SST--induced changes to the surface wind fields. The SST modification to the wind fields is based on a baroclinic argument as implemented by the University of Washington Planetary Boundary-Layer (UWPBL) model. Other input parameters include 2-m air temperature, 2-m dew point temperature, surface pressure (all from ERA--interim), and Reynolds Daily Optimum Interpolation Sea Surface Temperature (OISST). Flux model runs are performed every 6 hours starting in December 2002 and ending in November 2003. From these model outputs, seasonal, monthly, and daily means of the difference between DeltaSST and no DeltaSST effects on sensible heat flux (SHF), latent heat flux (LHF), and surface stress are calculated. Since the greatest impacts occur during the winter season, six additional December-January-February (DJF) seasons were analyzed for 1987--1990 and 1999--2002. The greatest differences in surface turbulent fluxes are concentrated near strong SST fronts associated with the Gulf Stream and Kuroshio Extension. On average, 2002---2003 DJF seasonal differences in SHF

  3. [The temperature and temperature gradients distribution in the rabbit body thermophysical model with evaporation of moisture from its surface].

    Science.gov (United States)

    Rumiantsev, G V

    2004-04-01

    On created in laboratory heat-physical model of a rabbit body reflecting basic heat-physical parameters of the body such as: weight, size of a relative surface, heat absorption and heat conduction, heat capacity etc., a change of radial distribution of temperature and size was found across a superficial layer of evaporation of water from its surface, that simulates sweating, with various ratio of environmental temperature and capacity of electrical heater simulating heat production in animal. The experiments have shown that with evaporation of moisture from a surface of model in all investigated cases, there is an increase of superficial layer of body of a temperature gradient and simultaneous decrease of temperature of a model inside and on the surface. It seems that, with evaporation of a moisture from a surface of a body, the size of a temperature gradient in a thin superficial layer dependent in our experiments on capacity for heat production and environmental temperature, is increased and can be used in a live organism for definition of change in general heat content of the body with the purpose of maintenance of its thermal balance with environment.

  4. Threshold for the destabilisation of the ion-temperature-gradient mode in magnetically confined toroidal plasmas

    Science.gov (United States)

    Zocco, A.; Xanthopoulos, P.; Doerk, H.; Connor, J. W.; Helander, P.

    2018-02-01

    The threshold for the resonant destabilisation of ion-temperature-gradient (ITG) driven instabilities that render the modes ubiquitous in both tokamaks and stellarators is investigated. We discover remarkably similar results for both confinement concepts if care is taken in the analysis of the effect of the global shear . We revisit, analytically and by means of gyrokinetic simulations, accepted tokamak results and discover inadequacies of some aspects of their theoretical interpretation. In particular, for standard tokamak configurations, we find that global shear effects on the critical gradient cannot be attributed to the wave-particle resonance destabilising mechanism of Hahm & Tang (Phys. Plasmas, vol. 1, 1989, pp. 1185-1192), but are consistent with a stabilising contribution predicted by Biglari et al. (Phys. Plasmas, vol. 1, 1989, pp. 109-118). Extensive analytical and numerical investigations show that virtually no previous tokamak theoretical predictions capture the temperature dependence of the mode frequency at marginality, thus leading to incorrect instability thresholds. In the asymptotic limit , where is the rotational transform, and such a threshold should be solely determined by the resonant toroidal branch of the ITG mode, we discover a family of unstable solutions below the previously known threshold of instability. This is true for a tokamak case described by a local local equilibrium, and for the stellarator Wendelstein 7-X, where these unstable solutions are present even for configurations with a small trapped-particle population. We conjecture they are of the Floquet type and derive their properties from the Fourier analysis of toroidal drift modes of Connor & Taylor (Phys. Fluids, vol. 30, 1987, pp. 3180-3185), and to Hill's theory of the motion of the lunar perigee (Acta Math., vol. 8, 1886, pp. 1-36). The temperature dependence of the newly determined threshold is given for both confinement concepts. In the first case, the new temperature-gradient

  5. Experimental observation of electron-temperature-gradient turbulence in a laboratory plasma.

    Science.gov (United States)

    Mattoo, S K; Singh, S K; Awasthi, L M; Singh, R; Kaw, P K

    2012-06-22

    We report the observation of electron-temperature-gradient (ETG) driven turbulence in the laboratory plasma of a large volume plasma device. The removal of unutilized primary ionizing and nonthermal electrons from uniform density plasma and the imposition and control of the gradient in the electron temperature (T[Symbol: see text] T(e)) are all achieved by placing a large (2 m diameter) magnetic electron energy filter in the middle of the device. In the dressed plasma, the observed ETG turbulence in the lower hybrid range of frequencies ν = (1-80 kHz) is characterized by a broadband with a power law. The mean wave number k perpendicular ρ(e) = (0.1-0.2) satisfies the condition k perpendicular ρ(e) ≤ 1, where ρ(e) is the electron Larmor radius.

  6. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

    DEFF Research Database (Denmark)

    Rinnan, Riikka; Rousk, Johannes; Yergeau, Etienne

    2009-01-01

    Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short-term temperature dependencies of Antarctic soil bacterial community growth rates, using...... the leucine incorporation technique, in order to predict future changes in temperature sensitivity of resident soil bacterial communities. Soil samples were collected along a climate gradient consisting of locations on the Antarctic Peninsula (Anchorage Island, 67 °34'S, 68 °08'W), Signy Island (60 °43'S, 45......) over 3 years had no effects on temperature relationship of the soil bacterial community. We estimate that the predicted temperature increase of 2.6 °C for the Antarctic Peninsula would increase Tmin by 0.6-1 °C and Q10 (0-10 °C) by 0.5 units....

  7. Measurement of water vapour transport through a porous non-hygroscopic material in a temperature gradient

    DEFF Research Database (Denmark)

    Hansen, Thor; Padfield, Tim; Hansen, Kurt Kielsgaard

    2014-01-01

    This was an experiment to identify the driving potential for water vapour diffusion through porous materials in a temperature gradient. The specimen of mineral fibre insulation was placed between a space with controlled temperature and relative humidity and a space with a controlled, higher...... temperature, and a measured but not controlled relative humidity (RH). This assembly was allowed to reach equilibrium with no vapour movement between the spaces, as tested by a constant RH on each side and by zero flux of water vapour measured in the cold side chamber. The RH and temperature values were...... be tested experimentally in this way, but it is reasonable to assume that concentration is the driving potential. The close equality of the concentrations makes it unnecessary to invoke temperature difference as a third possible potential for driving diffusion....

  8. Time-domain Brillouin scattering for the determination of laser-induced temperature gradients in liquids

    Science.gov (United States)

    Chaban, Ievgeniia; Shin, Hyun D.; Klieber, Christoph; Busselez, Rémi; Gusev, Vitalyi E.; Nelson, Keith A.; Pezeril, Thomas

    2017-07-01

    We present an optical technique based on ultrafast photoacoustics to determine the local temperature distribution profile in liquid samples in contact with a laser heated optical transducer. This ultrafast pump-probe experiment uses time-domain Brillouin scattering (TDBS) to locally determine the light scattering frequency shift. As the temperature influences the Brillouin scattering frequency, the TDBS signal probes the local laser-induced temperature distribution in the liquid. We demonstrate the relevance and the sensitivity of this technique for the measurement of the absolute laser-induced temperature gradient of a glass forming liquid prototype, glycerol, at different laser pump powers—i.e., different steady state background temperatures. Complementarily, our experiments illustrate how this TDBS technique can be applied to measure thermal diffusion in complex multilayer systems in contact with a surrounding liquid.

  9. Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field

    DEFF Research Database (Denmark)

    Chakrabarti, N.; Juul Rasmussen, J.

    1999-01-01

    The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions...... and ultimately lead to a dominating monopolar form. The effects of magnetic shear indicate it may destroy these structures. (C) 1999 American Institute of Physics....

  10. A study of self organized criticality in ion temperature gradient mode driven gyrokinetic turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Mavridis, M.; Isliker, H.; Vlahos, L. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Görler, T.; Jenko, F.; Told, D. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)

    2014-10-15

    An investigation on the characteristics of self organized criticality (Soc) in ITG mode driven turbulence is made, with the use of various statistical tools (histograms, power spectra, Hurst exponents estimated with the rescaled range analysis, and the structure function method). For this purpose, local non-linear gyrokinetic simulations of the cyclone base case scenario are performed with the GENE software package. Although most authors concentrate on global simulations, which seem to be a better choice for such an investigation, we use local simulations in an attempt to study the locally underlying mechanisms of Soc. We also study the structural properties of radially extended structures, with several tools (fractal dimension estimate, cluster analysis, and two dimensional autocorrelation function), in order to explore whether they can be characterized as avalanches. We find that, for large enough driving temperature gradients, the local simulations exhibit most of the features of Soc, with the exception of the probability distribution of observables, which show a tail, yet they are not of power-law form. The radial structures have the same radial extent at all temperature gradients examined; radial motion (transport) though appears only at large temperature gradients, in which case the radial structures can be interpreted as avalanches.

  11. An elastic-plastic iceberg material model considering temperature gradient effects and its application to numerical study

    Science.gov (United States)

    Shi, Chu; Hu, Zhiqiang; Luo, Yu

    2016-12-01

    To simulate the FPSO-iceberg collision process more accurately, an elastic-plastic iceberg material model considering temperature gradient effects is proposed and applied. The model behaves linearly elastic until it reaches the `Tsai-Wu' yield surfaces, which are a series of concentric elliptical curves of different sizes. Decreasing temperature results in a large yield surface. Failure criteria, based on the influence of accumulated plastic strain and hydrostatic pressure, are built into the model. Based on published experimental data on the relationship between depth and temperature in icebergs, three typical iceberg temperature profiles are proposed. According to these, ice elements located at different depths have different temperatures. The model is incorporated into LS-DYNA using a user-defined subroutine and applied to a simulation of FPSO collisions with different types of iceberg. Simulated area-pressure curves are compared with design codes to validate the iceberg model. The influence of iceberg shape and temperature on the collision process is analyzed. It is indicated that FPSO structural damage not only depends on the relative strength between the iceberg and the structure, but also depends on the local shape of the iceberg.

  12. Surface temperatures and temperature gradient features of the US Gulf Coast waters

    Science.gov (United States)

    Huh, O. K.; Rouse, L. J., Jr.; Smith, G. W.

    1977-01-01

    Satellite thermal infrared data on the Gulf of Mexico show that a seasonal cycle exists in the horizontal surface temperature structure. In the fall, the surface temperatures of both coastal and deep waters are nearly uniform. With the onset of winter, atmospheric cold fronts, which are accompanied by dry, low temperature air and strong winds, draw heat from the sea. A band of cooler water forming on the inner shelf expands, until a thermal front develops seaward along the shelf break between the cold shelf waters and the warmer deep waters of the Gulf. Digital analysis of the satellite data was carried out in an interactive mode using a minicomputer and software. A time series of temperature profiles illustrates the temporal and spatial changes in the sea-surface temperature field.

  13. Circulatory osmotic desalination driven by a mild temperature gradient based on lower critical solution temperature (LCST) phase transition materials.

    Science.gov (United States)

    Mok, Yeongbong; Nakayama, Daichi; Noh, Minwoo; Jang, Sangmok; Kim, Taeho; Lee, Yan

    2013-11-28

    Abrupt changes in effective concentration and osmotic pressure of lower critical solution temperature (LCST) mixtures facilitate the design of a continuous desalination method driven by a mild temperature gradient. We propose a prototype desalination system by circulating LCST mixtures between low and high temperature (low T and high T) units. Water molecules could be drawn from a high-salt solution to the LCST mixture through a semipermeable membrane at a temperature lower than the phase transition temperature, at which the effective osmotic pressure of the LCST mixture is higher than the high-salt solution. After transfer of water to the high T unit where the LCST mixture is phase-separated, the water-rich phase could release the drawn water into a well-diluted solution through the second membrane due to the significant decrease in effective concentration. The solute-rich phase could be recovered in the low T unit via a circulation process. The molar mass, phase transition temperature, and aqueous solubility of the LCST solute could be tuneable for the circulatory osmotic desalination system in which drawing, transfer, release of water, and the separation and recovery of the solutes could proceed simultaneously. Development of a practical desalination system that draws water molecules directly from seawater and produces low-salt water with high purity by mild temperature gradients, possibly induced by sunlight or waste heat, could be attainable by a careful design of the molecular structure and combination of the circulatory desalination systems based on low- and high-molar-mass LCST draw solutes.

  14. Application of high temperature superconductors to high-gradient magnetic separation

    Energy Technology Data Exchange (ETDEWEB)

    Daugherty, M.A.; Prenger, F.C.; Hill, D.D.; Daney, D.E.; Worl, L.W.; Schake, A.R.; Padilla, D.D.

    1994-06-01

    High Gradient Magnetic Separation (HGMS) is a powerful technique which can be used to separate widely dispersed contaminants from a host material, This technology can separate magnetic solids from other solids, liquids or gases. As the name implies HGMS uses large magnetic field gradients to separate ferromagnetic and paramagnetic particles. HGMS separators usually consist of a high-field solenoid magnet, the bore of which contains a fine-structured, ferromagnetic matrix material. The matrix material locally distorts the magnetic field and creates large field gradients in the vicinity of the matrix elements. These elements then become trapping sites for magnetic particles and are the basis for the magnetic separation. In this paper we discuss the design and construction of a prototype HGMS unit using a magnet made with high temperature superconductors (HTS). The prototype consists of an outer vacuum vessel which contains the HTS solenoid magnet The magnet is surrounded by a thermal radiation shield and multilayer insulation (MLI) blankets. The magnet, thermal shield and current leads all operate in a vacuum and are cooled by a cryocooler. High temperature superconducting current leads are used to reduce the heat leak from the ambient environment to the HTS magnet.

  15. Gradient corrections to the kinetic energy density functional of a two-dimensional Fermi gas at finite temperature

    Science.gov (United States)

    van Zyl, B. P.; Berkane, K.; Bencheikh, K.; Farrell, A.

    2011-05-01

    We examine the leading-order semiclassical gradient corrections to the noninteracting kinetic-energy density functional of a two-dimensional Fermi gas by applying the extended Thomas-Fermi theory at finite temperature. We find a nonzero von Weizsäcker-like gradient correction, which in the high-temperature limit goes over to the functional form (ℏ2/24m)(∇ρ)2/ρ. Our work provides a theoretical justification for the inclusion of gradient corrections in applications of density-functional theory to inhomogeneous two-dimensional Fermi systems at any finite temperature.

  16. Directional solidification of C8-BTBT films induced by temperature gradients and its application for transistors

    Science.gov (United States)

    Fujieda, Ichiro; Iizuka, Naoki; Onishi, Yosuke

    2015-03-01

    Because charge transport in a single crystal is anisotropic in nature, directional growth of single crystals would enhance device performance and reduce its variation among devices. For an organic thin film, a method based on a temperature gradient would offer advantages in throughput and cleanliness. In experiments, a temperature gradient was established in a spin-coated film of 2,7-dioctyl [1]benzothieno[3,2-b]benzothiophene (C8-BTBT) by two methods. First, a sample was placed on a metal plate bridging two heat stages. When one of the heat stages was cooled, the material started to solidify from the colder region. The melt-solid interface proceeded along the temperature gradient. Cracks were formed perpendicular to the solidification direction. Second, a line-shaped region on the film was continuously exposed to the light from a halogen lamp. After the heat stage was cooled, cracks similar to the first experiment were observed, indicating that the melt-solid interface moved laterally. We fabricated top-contact, bottom-gate transistors with these films. Despite the cracks, field-effect mobility of the transistors fabricated with these films was close to 6 cm2 /Vs and 4 cm2 /Vs in the first and second experiment, respectively. Elimination of cracks would improve charge transport and reduce performance variation among devices. It should be noted that the intense light from the halogen lamp did not damage the C8-BTBT films. The vast knowledge on laser annealing is now available for directional growth of this type of materials. The associated cost would be much smaller because an organic thin film melts at a low temperature.

  17. Extraction of espresso coffee by using gradient of temperature. Effect on physicochemical and sensorial characteristics of espresso.

    Science.gov (United States)

    Salamanca, C Alejandra; Fiol, Núria; González, Carlos; Saez, Marc; Villaescusa, Isabel

    2017-01-01

    Espresso extraction is generally carried out at a fixed temperature within the range 85-95°C. In this work the extraction of the espressos was made in a new generation coffee machine that enables temperature profiling of the brewing water. The effect of using gradient of temperature to brew espressos on physicochemical and sensorial characteristics of the beverage has been investigated. Three different extraction temperature profiles were tested: updrawn gradient (88-93°C), downdrawn gradient (93-88°C) and fixed temperature (90°C). The coffee species investigated were Robusta, Arabica natural and Washed Arabica. Results proved that the use of gradient temperature for brewing espressos allows increasing or decreasing the extraction of some chemical compounds from coffee grounds. Moreover an appropriate gradient of temperature can highlight or hide some sensorial attributes. In conclusion, the possibility of programming gradient of temperature in the coffee machines recently introduced in the market opens new expectations in the field of espresso brewing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Tomography-based characterization of ice-air interface dynamics of temperature gradient snow metamorphism under advective conditions

    Science.gov (United States)

    Ebner, Pirmin Philipp; Andreoli, Christian; Schneebeli, Martin; Steinfeld, Aldo

    2015-12-01

    Snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow, which alters its microstructure and physical properties. A functional understanding of this process is essential for many disciplines, from modeling the effects of snow on regional and global climate to assessing avalanche formation. Time-lapse X-ray microtomography was applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions. Experiments specifically analyzed sublimation and deposition of water vapor on the ice structure. In addition, an analysis of the ice-air interface dynamics was carried out using a macroscopic equivalent model of heat and water vapor transport through a snow layer. The results indicate that sublimation of the ice matrix dominated for flow rates deposition supplied by the advective flow counteracted sublimation. A flow rate dependence of water vapor deposition at the ice interface was observed, asymptotically approaching an average estimated maximum deposition rate on the whole sample of 1.05 · 10-4 kg m-3 s-1. The growth of microsized whisker-like crystals on larger ice crystals was detected on microscope photographs, leading to an increase of the specific surface area and thus suggest a change of the physical and optical properties of the snow. The estimated values of the curvature effect of the ice crystals and the interface kinetic coefficient are in good agreement with previously published values.

  19. Effect of fast mold surface temperature evolution on iPP part morphology gradients

    Science.gov (United States)

    Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo; Cakmak, Mukerrem; Titomanlio, Giuseppe

    2016-03-01

    The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micro structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.

  20. Effect of fast mold surface temperature evolution on iPP part morphology gradients

    Energy Technology Data Exchange (ETDEWEB)

    Liparoti, Sara [Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II, 132, 84084 Fisciano (Italy); Sorrentino, Andrea [Institute for Polymers, Composites and Biomaterials (IPCB), National Research Council (CNR), P. Enrico Fermi 1, 80055 Portici (Italy); Guzman, Gustavo; Cakmak, Mukerrem; Titomanlio, Giuseppe, E-mail: gtitomanlio@unisa.it [Department of Polymer Engineering, The University of Akron, Akron, OH 44325 (United States)

    2016-03-09

    The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micro structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.

  1. A reduced core to skin temperature gradient, not a critical core temperature, affects aerobic capacity in the heat.

    Science.gov (United States)

    Cuddy, John S; Hailes, Walter S; Ruby, Brent C

    2014-07-01

    The purpose of this study was to determine the impact of the core to skin temperature gradient during incremental running to volitional fatigue across varying environmental conditions. A secondary aim was to determine if a "critical" core temperature would dictate volitional fatigue during running in the heat. 60 participants (n=49 male, n=11 female; 24±5 yrs, 177±11 cm, 75±13 kg) completed the study. Participants were uniformly stratified into a specific exercise temperature group (18 °C, 26 °C, 34 °C, or 42 °C) based on a 3-mile run performance. Participants were equipped with core and chest skin temperature sensors and a heart rate monitor, entered an environmental chamber (18 °C, 26 °C, 34 °C, or 42 °C), and rested in the seated position for 10 min before performing a walk/run to volitional exhaustion. Initial treadmill speed was 3.2 km h(-1) with a 0% grade. Every 3 min, starting with speed, speed and grade increased in an alternating pattern (speed increased by 0.805 km h(-1), grade increased by 0.5%). Time to volitional fatigue was longer for the 18 °C and 26 °C group compared to the 42 °C group, (58.1±9.3 and 62.6±6.5 min vs. 51.3±8.3 min, respectively, pskin gradient for the 18 °C and 26 °C groups was larger compared to 42 °C group (halfway: 2.6±0.7 and 2.0±0.6 vs. 1.3±0.5 for the 18 °C, 26 °C and 42 °C groups, respectively; finish: 3.3±0.7 and 3.5±1.1 vs. 2.1±0.9 for the 26 °C, 34 °C, and 42 °C groups, respectively, ptemperature and heart rate response during the exercise trials. The current data demonstrate a 13% and 22% longer run time to exhaustion for the 18 °C and 26 °C group, respectively, compared to the 42 °C group despite no differences in beginning and ending core temperatures or baseline 3-mile run time. This capacity difference appears to result from a magnified core to skin gradient via an environmental temperature advantageous to convective heat loss, and in part from an increased sweat rate. Copyright

  2. A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses

    DEFF Research Database (Denmark)

    Elsgaard, Lars; Jørgensen, Leif Wagner

    2002-01-01

    of 28-ml test tubes. An electric plate heats one end of the TGI end and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA...

  3. Nature of Transport across Sheared Zonal Flows in Electrostatic Ion-Temperature-Gradient Gyrokinetic Plasma Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Raul [ORNL; Newman, David E [University of Alaska; Leboeuf, Jean-Noel [JNL Scientific, Inc., Casa Grande, AZ; Decyk, Viktor [University of California, Los Angeles; Carreras, Benjamin A [BACV Solutions, Inc., Oak Ridge

    2008-01-01

    It is shown that the usual picture for the suppression of turbulent transport across a stable sheared flow based on a reduction of diffusive transport coefficients is, by itself, incomplete. By means of toroidal gyrokinetic simulations of electrostatic, collisionless ion-temperature-gradient turbulence, it is found that the nature of the transport is altered fundamentally, changing from diffusive to anticorrelated and subdiffusive. Additionally, whenever the flows are self-consistently driven by turbulence, the transport gains an additional non-Gaussian character. These results suggest that a description of transport across sheared flows using effective diffusivities is oversimplified.

  4. Effects of multiple-helicity fields on ion temperature gradient modes

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, T. [National Inst. for Fusion Science, Toki, Gifu (Japan); Sugama, H. [Graduate Univ. for Advanced Studies, Toki, Gigu (Japan)

    2001-04-01

    Effects of multiple-helicity magnetic fields on ion temperature gradient (ITG) modes in toroidal helical systems like the Large Helical Device (LHD) are studied by means of the linear gyrokinetic theory. Especially, dependence of the real frequency, growth rate, and the eigenfunction of the ITG mode on sideband-helicity fields added to the main helical component is investigated. Comparison between multiple-helicity effects on the ITG mode with those on the neoclassical ripple transport is presented, and optimization of the magnetic configuration for better plasma confinement is discussed. (author)

  5. Assimilation of temperature and hydraulic gradients for quantifying the spatial variability of streambed hydraulics

    Science.gov (United States)

    Huang, Xiang; Andrews, Charles B.; Liu, Jie; Yao, Yingying; Liu, Chuankun; Tyler, Scott W.; Selker, John S.; Zheng, Chunmiao

    2016-08-01

    Understanding the spatial and temporal characteristics of water flux into or out of shallow aquifers is imperative for water resources management and eco-environmental conservation. In this study, the spatial variability in the vertical specific fluxes and hydraulic conductivities in a streambed were evaluated by integrating distributed temperature sensing (DTS) data and vertical hydraulic gradients into an ensemble Kalman filter (EnKF) and smoother (EnKS) and an empirical thermal-mixing model. The formulation of the EnKF/EnKS assimilation scheme is based on a discretized 1D advection-conduction equation of heat transfer in the streambed. We first systematically tested a synthetic case and performed quantitative and statistical analyses to evaluate the performance of the assimilation schemes. Then a real-world case was evaluated to calculate assimilated specific flux. An initial estimate of the spatial distributions of the vertical hydraulic gradients was obtained from an empirical thermal-mixing model under steady-state conditions using a constant vertical hydraulic conductivity. Then, this initial estimate was updated by repeatedly dividing the assimilated specific flux by estimates of the vertical hydraulic gradients to obtain a refined spatial distribution of vertical hydraulic gradients and vertical hydraulic conductivities. Our results indicate that optimal parameters can be derived with fewer iterations but greater simulation effort using the EnKS compared with the EnKF. For the field application in a stream segment of the Heihe River Basin in northwest China, the average vertical hydraulic conductivities in the streambed varied over three orders of magnitude (5 × 10-1 to 5 × 102 m/d). The specific fluxes ranged from near zero (qz fish spawning and other wildlife incubation, regional flow and hyporheic solute transport models in the Heihe River Basin, as well as in other similar hydrologic settings.

  6. The effects of temperature gradient and growth rate on the morphology and fatigue properties of MAR-M246(Hf)

    Science.gov (United States)

    Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.

    1989-01-01

    MAR-M246(Hf) is a nickel based superalloy used in the turbopump blades of the Space Shuttle main engines. The effects are considered of temperature gradient (G) and growth rate (R) on the microstructure and fatigue properties of this superalloy. The primary dendrite arm spacings were found to be inversely proportional to both temperature gradient and growth rate. Carbide and gamma - gamma prime morphology trends were related to G/R ratios. Weibull analysis of fatigue results shows the characteristic life to be larger by a factor of 10 for the low gradient/fast rate pairing of G and R, while the reliability (beta) was lower.

  7. Welding deformation analysis based on improved equivalent strain method considering the effect of temperature gradients

    Directory of Open Access Journals (Sweden)

    Tae-Jun Kim

    2015-01-01

    Full Text Available In the present study, the existing equivalent stain method is improved to make up for its weaknesses. The improved inherent strain model is built considering more sophisticated three dimensional constraints which are embodied by six cubic elements attached on three sides of a core cubic element. From a few case studies, it is found that the inherent strain is mainly affected by the changes in restraints induced by changes of temperature-dependent material properties of the restraining elements. On the other hand, the degree of restraints is identified to be little influential to the inherent strain. Thus, the effect of temperature gradients over plate thickness and plate transverse direction normal to welding is reflected in the calculation of the inherent strain chart. The welding deformation can be calculated by an elastic FE analysis using the inherent strain values taken from the inherent strain chart.

  8. Evaluating the coefficient of thermal expansion using time periods of minimal thermal gradient for a temperature driven structural health monitoring

    Science.gov (United States)

    Reilly, J.; Abdel-Jaber, H.; Yarnold, M.; Glisic, B.

    2017-04-01

    Structural Health Monitoring aims to characterize the performance of a structure from a combination of recorded sensor data and analytic techniques. Many methods are concerned with quantifying the elastic response of the structure, treating temperature changes as noise in the analysis. While these elastic profiles do demonstrate a portion of structural behavior, thermal loads on a structure can induce comparable strains to elastic loads. Understanding this relationship between the temperature of the structure and the resultant strain and displacement can provide in depth knowledge of the structural condition. A necessary parameter for this form of analysis is the Coefficient of Thermal Expansion (CTE). The CTE of a material relates the amount of expansion or contraction a material undergoes per degree change in temperature, and can be determined from temperature-strain relationship given that the thermal strain can be isolated. Many times with concrete, the actual amount of expansion with temperature in situ varies from the given values for the CTE due to thermally generated elastic strain, which complicates evaluation of the CTE. To accurately characterize the relationship between temperature and strain on a structure, the actual thermal behavior of the structure needs to be analyzed. This rate can vary for different parts of a structure, depending on boundary conditions. In a case of unrestrained structures, the strain in the structure should be linearly related to the temperature change. Thermal gradients in a structure can affect this relationship, as they induce curvature and deplanations in the cross section. This paper proposes a method that addresses these challenges in evaluating the CTE.

  9. Direct temperature mass spectrometric study on the depth-dependent compositional gradients of aged triterpenoid varnishes

    Science.gov (United States)

    Theodorakopoulos, Charis; Boon, Jaap J.; Zafiropulos, Vassilis

    2009-07-01

    The depth profiles of aged dammar and mastic films, which were uncovered by optimized KrF excimer laser ablation (248 nm, 25 ns), were examined by direct temperature-resolved mass spectrometry (DTMS). The results establish the generation of depth-dependent compositional gradients in triterpenoid resins as a consequence of aging, for the first time on the molecular level. Electron ionization DTMS total ion currents show that the required temperature to volatilize the polar compounds and the relative amount of pyrolysis products of the high molecular weight condensed fraction is reduced when the upper layer of varying thickness of the films had been removed by the laser. The relative abundance of characteristic ion fragments of known oxidized triterpenoid compounds gradually decreased with depth. In contrast, the ion fragments of original resin molecules became more abundant with depth. The mass spectra of the bulk of the films resembled that of the control samples, which were not subjected to aging. Multivariant factor discriminant analysis quantified the oxidative gradients and showed that a depth of 15 [mu]m from the surface of the aged films is the threshold between highly and much less deteriorated material.

  10. Topological susceptibility in finite temperature (2+1)-flavor QCD using gradient flow

    CERN Document Server

    Taniguchi, Yusuke; Suzuki, Hiroshi; Umeda, Takashi

    2016-01-01

    We compute the topological charge and its susceptibility in finite temperature (2+1)-flavor QCD on the lattice applying a gradient flow method. With the Iwasaki gauge action and non-perturbatively $O(a)$-improved Wilson quarks, we perform simulations on a fine lattice with~$a\\simeq0.07\\,\\mathrm{fm}$ at a heavy $u$, $d$ quark mass with $m_\\pi/m_\\rho\\simeq0.63$ but approximately physical $s$ quark mass of $m_{\\eta_{ss}}/m_\\phi\\simeq0.74$. In a temperature range from~$T\\simeq174\\,\\mathrm{MeV}$ ($N_t=16$) to $697\\,\\mathrm{MeV}$ ($N_t=4$), we study two topics on the topological susceptibility. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Because the two definitions are related by chiral Ward-Takahashi identities, their equivalence is not trivial for lattice quarks which violate the chiral symmetry explicitly at finite lattice spacings. The gradient flow method enables us to compute them without being bothered by the chiral violation. We find a good agreement between t...

  11. Can temperature explain the latitudinal gradient of ulcerative colitis? Cohort of Norway

    Science.gov (United States)

    2013-01-01

    Background Incidence and prevalence of ulcerative colitis follow a north–south (latitudinal) gradient and increases northwards at the northern hemisphere or southwards at the southern hemisphere. The disease has increased during the last decades. The temporal trend has been explained by the hygiene hypothesis, but few parallel explanations exist for the spatial variability. Many factors are linked to latitude such as climate. Our purpose was to investigate the association between variables governing the climate and prospectively identified patients. Methods In this study, we used a subset of the population-based Cohort of Norway (n = 80412) where 370 prevalent cases of ulcerative colitis were identified through self-reported medication. The meteorological and climatic variables temperature, precipitation, and altitude were recorded from weather stations of the Norwegian Meteorological Institute. Summer temperature was used to capture environmental temperature. Results Summer temperature was significantly related to the prevalence of ulcerative colitis. For each one-degree increase in temperature the odds for ulcerative colitis decreased with about 9% (95% CI: 3%-15%). None of the other climatic factors were significantly associated to the risk of ulcerative colitis. Contextual variables did not change the association to the prevalence of ulcerative colitis. Conclusions The present results show that the prevalence of ulcerative colitis is associated to summer temperature. Our speculation is that summer temperature works as an instrumental variable for the effect of microbial species richness on the development of ulcerative colitis. Environmental temperature is one of the main forces governing microbial species richness and the microbial composition of the commensal gut flora is known to be an important part in the process leading to ulcerative colitis. PMID:23724802

  12. Can temperature explain the latitudinal gradient of ulcerative colitis? Cohort of Norway.

    Science.gov (United States)

    Aamodt, Geir; Bengtson, May-Bente; Vatn, Morten H

    2013-05-31

    Incidence and prevalence of ulcerative colitis follow a north-south (latitudinal) gradient and increases northwards at the northern hemisphere or southwards at the southern hemisphere. The disease has increased during the last decades. The temporal trend has been explained by the hygiene hypothesis, but few parallel explanations exist for the spatial variability. Many factors are linked to latitude such as climate. Our purpose was to investigate the association between variables governing the climate and prospectively identified patients. In this study, we used a subset of the population-based Cohort of Norway (n = 80412) where 370 prevalent cases of ulcerative colitis were identified through self-reported medication. The meteorological and climatic variables temperature, precipitation, and altitude were recorded from weather stations of the Norwegian Meteorological Institute. Summer temperature was used to capture environmental temperature. Summer temperature was significantly related to the prevalence of ulcerative colitis. For each one-degree increase in temperature the odds for ulcerative colitis decreased with about 9% (95% CI: 3%-15%). None of the other climatic factors were significantly associated to the risk of ulcerative colitis. Contextual variables did not change the association to the prevalence of ulcerative colitis. The present results show that the prevalence of ulcerative colitis is associated to summer temperature. Our speculation is that summer temperature works as an instrumental variable for the effect of microbial species richness on the development of ulcerative colitis. Environmental temperature is one of the main forces governing microbial species richness and the microbial composition of the commensal gut flora is known to be an important part in the process leading to ulcerative colitis.

  13. UTILITY OF THE WEAK TEMPERATURE GRADIENT APPROXIMATION FOR EARTH-LIKE TIDALLY LOCKED EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Sean M. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Abbot, Dorian S., E-mail: smills@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

    2013-09-10

    Planets in M dwarf stars' habitable zones are likely to be tidally locked with orbital periods of the order of tens of days. This means that the effects of rotation on atmospheric dynamics will be relatively weak, which requires small horizontal temperature gradients above the boundary layer of terrestrial atmospheres. An analytically solvable and dynamically consistent model for planetary climate with only three free parameters can be constructed by making the weak temperature gradient (WTG) approximation, which assumes temperatures are horizontally uniform aloft. The extreme numerical efficiency of a WTG model compared to a three-dimensional general circulation model (GCM) makes it an optimal tool for Monte Carlo fits to observables over parameter space. Additionally, such low-order models are critical for developing physical intuition and coupling atmospheric dynamics to models of other components of planetary climate. The objective of this paper is to determine whether a WTG model provides an adequate approximation of the effect of atmospheric dynamics on quantities likely to be observed over the next decade. To do this, we first tune a WTG model to GCM output for an Earth-like tidally locked planet with a dry, 1 bar atmosphere, then generate and compare the expected phase curves of both models. We find that differences between the two models would be extremely difficult to detect from phase curves using the James Webb Space Telescope. This result demonstrates the usefulness of the WTG approximation when used in conjunction with GCMs as part of a modeling hierarchy to understand the climate of remote planets.

  14. Elevational ranges of birds on a tropical montane gradient lag behind warming temperatures.

    Directory of Open Access Journals (Sweden)

    German Forero-Medina

    Full Text Available BACKGROUND: Species may respond to a warming climate by moving to higher latitudes or elevations. Shifts in geographic ranges are common responses in temperate regions. For the tropics, latitudinal temperature gradients are shallow; the only escape for species may be to move to higher elevations. There are few data to suggest that they do. Yet, the greatest loss of species from climate disruption may be for tropical montane species. METHODOLOGY/PRINCIPAL FINDINGS: We repeat a historical transect in Peru and find an average upward shift of 49 m for 55 bird species over a 41 year interval. This shift is significantly upward, but also significantly smaller than the 152 m one expects from warming in the region. To estimate the expected shift in elevation we first determined the magnitude of warming in the locality from historical data. Then we used the temperature lapse rate to infer the required shift in altitude to compensate for warming. The range shifts in elevation were similar across different trophic guilds. CONCLUSIONS: Endothermy may provide birds with some flexibility to temperature changes and allow them to move less than expected. Instead of being directly dependent on temperature, birds may be responding to gradual changes in the nature of the habitat or availability of food resources, and presence of competitors. If so, this has important implications for estimates of mountaintop extinctions from climate change.

  15. Development of a temperature gradient focusing method for in situ extraterrestrial biomarker analysis.

    Science.gov (United States)

    Danger, Grégoire; Ross, David

    2008-08-01

    Scanning temperature gradient focusing (TGF) is a recently described technique for the simultaneous concentration and separation of charged analytes. It allows for high analyte peak capacities and low LODs in microcolumn electrophoretic separations. In this paper, we present the application of scanning TGF for chiral separations of amino acids. Using a mixture of seven carboxyfluorescein succinimidyl ester-labeled amino acids (including five chiral amino acids) which constitute the Mars7 standard, we show that scanning TGF is a very simple and efficient method for chiral separations. The modulation of TGF separation parameters (temperature window, pressure scan rate, temperature range, and chiral selector concentration) allows optimization of peak efficiencies and analyte resolutions. The use of hydroxypropyl-beta-CD at low concentration (1-5 mmol/L) as a chiral selector, with an appropriate pressure scan rate ( -0.25 Pa/s) and with a low temperature range (3-25 degrees C over 1 cm) provided high resolution between enantiomers (Rs >1.5 for each pair of enantiomers) using a short, 4 cm long capillary. With these new results, the scanning TGF method appears to be a viable method for in situ trace biomarker analysis for future missions to Mars or other solar system bodies.

  16. Effects of population density and chemical environment on the behavior of Escherichia coli in shallow temperature gradients.

    Science.gov (United States)

    Demir, Mahmut; Douarche, Carine; Yoney, Anna; Libchaber, Albert; Salman, Hanna

    2011-12-01

    In shallow temperature gradients, changes in temperature that bacteria experience occur over long time scales. Therefore, slow processes such as adaptation, metabolism, chemical secretion and even gene expression become important. Since these are cellular processes, the cell density is an important parameter that affects the bacteria's response. We find that there are four density regimes with distinct behaviors. At low cell density, bacteria do not cause changes in their chemical environment; however, their response to the temperature gradient is strongly influenced by it. In the intermediate cell-density regime, the consumption of nutrients becomes significant and induces a gradient of nutrients opposing the temperature gradient due to higher consumption rate at the high temperature. This causes the bacteria to drift toward low temperature. In the high cell-density regime, interactions among bacteria due to secretion of an attractant lead to a strong local accumulation of bacteria. This together with the gradient of nutrients, resulted from the differential consumption rate, creates a fast propagating pulse of bacterial density. These observations are a result of classical nonlinear population dynamics. At extremely high cell density, a change in the physiological state of the bacteria is observed. The bacteria, at the individual level, become cold seeking. This appears initially as a result of a change in the methylation level of the two most abundant sensing receptors, Tsr and Tar. It is further enforced at an even higher cell density by a change in the expression level of these receptors.

  17. Method for analyzing passive silicon carbide thermometry with a continuous dilatometer to determine irradiation temperature

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Anne A., E-mail: campbellaa@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Porter, Wallace D.; Katoh, Yutai [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Snead, Lance L. [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2016-03-01

    Highlights: • Annealing of SiC via continuous dilatometry to determine irradiation temperature. • Wrote a program to analyze dilatometry results to determine irradiation temperature. • Dilatometry results are consistent with results from a historical technique. • Computer program was written in an open-source language and is available for others. - Abstract: Silicon carbide is used as a passive post-irradiation temperature monitor because the irradiation defects will anneal out above the irradiation temperature. The irradiation temperature is determined by measuring a property change after isochronal annealing, i.e., lattice spacing, dimensions, electrical resistivity, thermal diffusivity, or bulk density. However, such methods are time-consuming since the steps involved must be performed in a serial manner. This work presents the use of thermal expansion from continuous dilatometry to calculate the SiC irradiation temperature, which is an automated process requiring minimal setup time. Analysis software was written that performs the calculations to obtain the irradiation temperature and removes possible user-introduced error while standardizing the analysis. This method has been compared to an electrical resistivity and isochronal annealing investigation, and the results revealed agreement of the calculated temperatures. These results show that dilatometry is a reliable and less time-intensive process for determining irradiation temperature from passive SiC thermometry.

  18. Molecular Fingerprinting of Dairy Microbial Ecosystems by Use of Temporal Temperature and Denaturing Gradient Gel Electrophoresis

    Science.gov (United States)

    Ogier, J.-C.; Lafarge, V.; Girard, V.; Rault, A.; Maladen, V.; Gruss, A.; Leveau, J.-Y.; Delacroix-Buchet, A.

    2004-01-01

    Numerous microorganisms, including bacteria, yeasts, and molds, constitute the complex ecosystem present in milk and fermented dairy products. Our aim was to describe the bacterial ecosystem of various cheeses that differ by production technology and therefore by their bacterial content. For this purpose, we developed a rapid, semisystematic approach based on genetic profiling by temporal temperature gradient electrophoresis (TTGE) for bacteria with low-G+C-content genomes and denaturing gradient gel electrophoresis (DGGE) for those with medium- and high-G+C-content genomes. Bacteria in the unknown ecosystems were assigned an identity by comparison with a comprehensive bacterial reference database of ∼150 species that included useful dairy microorganisms (lactic acid bacteria), spoilage bacteria (e.g., Pseudomonas and Enterobacteriaceae), and pathogenic bacteria (e.g., Listeria monocytogenes and Staphylococcus aureus). Our analyses provide a high resolution of bacteria comprising the ecosystems of different commercial cheeses and identify species that could not be discerned by conventional methods; at least two species, belonging to the Halomonas and Pseudoalteromonas genera, are identified for the first time in a dairy ecosystem. Our analyses also reveal a surprising difference in ecosystems of the cheese surface versus those of the interior; the aerobic surface bacteria are generally G+C rich and represent diverse species, while the cheese interior comprises fewer species that are generally low in G+C content. TTGE and DGGE have proven here to be powerful methods to rapidly identify a broad range of bacterial species within dairy products. PMID:15345452

  19. Low Dimensional L-H-ELM Dynamical Model for Ion Temperature Gradient Driven Turbulence

    Science.gov (United States)

    Horton, W.; Hu, G.

    1996-11-01

    The role of self-generated shear flow in pressure gradient driven turbulence is widely reported in simulations, and also manifest itself in toroidal confinement experiments in the L mode, H mode and ELM mode transitions universaly seen at higher auxiliary heating power levels. We present a new d=11 dimensional nonlinear dynamics model derived from the well known two-component FLR fluid equations for the torodial ion temperature gradient (ITG) driven turbulence(W. Horton, D. I. Choi and W. M. Tang, Phys. Fluids 24),1077(1981).. The L mode corresponds to the Lorenz manifold which has d=5 and for which exact solutions are given. The bifurcation for the onset of sheared flows is reported and an example shows a 30% drop in the turbulent thermal flux. As the auxiliary heating power is increased, the steady tilted-cell convection with shear flows is destablized to the ELM-like oscillations. In contrast to the resistive-g mode(W. Horton, G. Hu and G. Laval, Phys. Plasmas 3), (1996)., the ITG model has a well defined finite amplitude oscillation (pump depletion) in the dissipationless limit due to the nonlinear frequency shifts and the linear wave dispersion. We ask the question as to whether there is a closure scheme for reducing the system to yield a thermodynamic model involving the physical energy components as is usually assumed in L-H- ELM modeling.

  20. Temperature Regimes Impact Coral Assemblages along Environmental Gradients on Lagoonal Reefs in Belize.

    Directory of Open Access Journals (Sweden)

    Justin H Baumann

    Full Text Available Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS. A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST to classify reefs as exposed to low (lowTP, moderate (modTP, or high (highTP temperature parameters over 10 years (2003 to 2012. Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a were obtained for 13-years (2003-2015 as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals

  1. Temperature Regimes Impact Coral Assemblages along Environmental Gradients on Lagoonal Reefs in Belize.

    Science.gov (United States)

    Baumann, Justin H; Townsend, Joseph E; Courtney, Travis A; Aichelman, Hannah E; Davies, Sarah W; Lima, Fernando P; Castillo, Karl D

    2016-01-01

    Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS). A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST) to classify reefs as exposed to low (lowTP), moderate (modTP), or high (highTP) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a) were obtained for 13-years (2003-2015) as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold) played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals utilizing

  2. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    Science.gov (United States)

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  3. Development and evaluation of a workpiece temperature analyzer for industrial furnaces

    Energy Technology Data Exchange (ETDEWEB)

    1990-05-01

    An instrument capable of measuring the bulk temperature of a workpiece while it is being heated could have a variety of applications. If such an instrument were reasonably priced, it would have a tremendous impact upon national energy usage. The Department of Energy has realized the importance of this type of instrument and has sponsored three concurrent programs to evaluate three different technologies for this type of instrument. In one of these programs, Surface Combustion is the prime contractor to develop a pulsed laser, polarizing interferometer based sensor to be used as a workpiece temperature analyzer (WPTA). The overall goal of the program is to develop a workpiece temperature analyzer for industrial furnaces to significantly improve product quality, productivity and energy efficiency. The workpiece temperature analyzer concept in this program uses a pulsed laser polarizing interferometer (PLPI) for measuring sound velocity through a workpiece. This type of instrument has a high resolution and could detect surface motion of as small as 10 picometer. The sound velocity measurement can be converted to an average workpiece temperature through a mathematical equation programmed into the microprocessor used for control. 76 refs., 12 figs., 14 tabs.

  4. Regulation of electron temperature gradient turbulence by zonal flows driven by trapped electron modes

    Energy Technology Data Exchange (ETDEWEB)

    Asahi, Y., E-mail: y.asahi@nr.titech.ac.jp; Tsutsui, H.; Tsuji-Iio, S. [Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Ishizawa, A.; Watanabe, T.-H. [National Institute for Fusion Science, Gifu 509-5292 (Japan)

    2014-05-15

    Turbulent transport caused by electron temperature gradient (ETG) modes was investigated by means of gyrokinetic simulations. It was found that the ETG turbulence can be regulated by meso-scale zonal flows driven by trapped electron modes (TEMs), which are excited with much smaller growth rates than those of ETG modes. The zonal flows of which radial wavelengths are in between the ion and the electron banana widths are not shielded by trapped ions nor electrons, and hence they are effectively driven by the TEMs. It was also shown that an E × B shearing rate of the TEM-driven zonal flows is larger than or comparable to the growth rates of long-wavelength ETG modes and TEMs, which make a main contribution to the turbulent transport before excitation of the zonal flows.

  5. GTC simulations of ion temperature gradient driven instabilities in W7-X and LHD stellarators

    Science.gov (United States)

    Wang, Hongyu

    2017-10-01

    We report GTC linear simulations of ion temperature gradient (ITG) instabilities in Wendelstein 7-X (W7-X) and Large Helical Device (LHD) stellarators. GTC has recently been updated to treat 3D equilibria by interfacing with MHD equilibrium code VMEC. GTC simulations of ITG have been carried out in both full torus and partial torus taking into account the toroidal periodicity of the stellarators. The effects of toroidal mode coupling on linear dispersions and mode structures in W7-X and LHD are studied. The mode structure in W7-X is more localized in the toroidal direction, and LHD is more extended in the toroidal direction and tokamak-like. Linear growth rates, real frequencies, and mode structures agree reasonably with results of EUTERPE simulations. In collaboration with I. Holod, J. Riemann, Z. Lin, J. Bao, L. Shi, S. Taimourzadeh, R. Kleiber, and M. Borchardt.

  6. Relationship of the cross phase and the zonal flow in electrostatic ion-temperature-gradient turbulence

    Science.gov (United States)

    Min, Byunghoon; An, Chan-Yong; Kim, Chang-Bae

    2017-10-01

    The cross phase δ, that is the phase difference between the electric potential and the ion pressure, is examined in the electrostatic ion-temperature-gradient fluid turbulence. It is important to study the cross phase because the thermal transport Γ is roughly proportional to sin δ. Three-dimensional numerical simulations are performed in the BOUT + + platform with the shifted metric coordinate system. The cross phase seems to show an interesting feature such that it is almost constant when the zonal flow Vis in the direction of the electron diamagnetic drift and the time evolution of the cross phase oscillates near zero at low poloidal wave number and Γ is small. These phenomena are closely correlated with the fluctuation level and depend closely on the curvature V'' of the zonal flow.

  7. Isotopic dependence of impurity transport driven by ion temperature gradient turbulence

    CERN Document Server

    Guo, Weixin; Zhuang, Ge

    2016-01-01

    Hydrogenic ion mass effects, namely the isotopic effects on impurity transport driven by ion temperature gradient (ITG) turbulence are investigated using gyrokinetic theory. For non-trace impurities, changing from hydrogen (H) to deuterium (D), and to tritium (T) plasmas, the outward flux for lower (higher) ionized impurities or for lighter (heavier) impurities is found to decrease (increase), although isotopic dependence of ITG linear growth rate is weak. This is mainly due to the decrease of outward (inward) convection, while the isotopic dependence of diffusion is relatively weak. In addition, the isotopic effects reduce (enhance) the impurity flux of fully ionized carbon (C6+) for weaker (stronger) magnetic shear. In trace impurity limit, the isotopic effects are found to reduce the accumulation of high-Z tungsten (W). Moreover, the isotopic effects on the peaking factor (PF) of trace high-Z W get stronger with stronger magnetic shear.

  8. Near-field radiative heat transfer under temperature gradients and conductive transfer

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Weiliang; Rodriguez, Alejandro W. [Princeton Univ., NJ (United States). Dept. of Electrical Engineering; Messina, Riccardo [CNRS-Univ. de Montpellier (France). Lab. Charles Coulomb

    2017-05-01

    We describe a recently developed formulation of coupled conductive and radiative heat transfer (RHT) between objects separated by nanometric, vacuum gaps. Our results rely on analytical formulas of RHT between planar slabs (based on the scattering-matrix method) as well as a general formulation of RHT between arbitrarily shaped bodies (based on the fluctuating-volume current method), which fully captures the existence of temperature inhomogeneities. In particular, the impact of RHT on conduction, and vice versa, is obtained via self-consistent solutions of the Fourier heat equation and Maxwell's equations. We show that in materials with low thermal conductivities (e.g. zinc oxides and glasses), the interplay of conduction and RHT can strongly modify heat exchange, exemplified for instance by the presence of large temperature gradients and saturating flux rates at short (nanometric) distances. More generally, we show that the ability to tailor the temperature distribution of an object can modify the behaviour of RHT with respect to gap separations, e.g. qualitatively changing the asymptotic scaling at short separations from quadratic to linear or logarithmic. Our results could be relevant to the interpretation of both past and future experimental measurements of RHT at nanometric distances.

  9. Solitary states in the Taylo-Couette system with a radial temperature gradient

    Science.gov (United States)

    Savaro, Clément; Prigent, Arnaud; Mutabazi, Innocent

    2014-11-01

    The vertical Taylor-Couette system with a radial temperature gradient exhibits a rich variety of states since the base flow state is a combination of the circular Couette flow and an axial baroclinic flow. Two main control parameters characterize the flow: the Taylor number (Ta) for the rotation and the Grashof number (Gr) for the temperature difference. For small values of Gr , the critical state is the Taylor vortices, and for large values of Gr , the critical states appear either in form of helicoidal vortices or modulated waves. For a fixed value of Gr , increasing Ta leads to the appearance of higher instability modes where helicoidal vortices or traveling waves bifurcate into contrarotating vortices. A special attention will be focused on the states observed for | Gr | > 1500 and Ta ~= 12 when the base state bifurcates to a state of modulated wave. A small increase of Ta leads to the appearance of a solitary wave which is superimposed to the modulated wave state. Using visualization technique and particle image velocimetry (PIV) coupled with liquid crystal thermography (TLC), we have measured the amplitude of the solitary structure from velocity and temperature fields. The spatial and temporal localizations give the signature of the solitary wave. Supported by the French National Research Agency (ANR) through the program Investissements d'Avenir (ANR-10 LABX-09-01), LABEX EMC3.

  10. Increased temperatures negatively affect Juniperus communis seeds: evidence from transplant experiments along a latitudinal gradient.

    Science.gov (United States)

    Gruwez, R; De Frenne, P; Vander Mijnsbrugge, K; Vangansbeke, P; Verheyen, K

    2016-05-01

    With a distribution range that covers most of the Northern hemisphere, common juniper (Juniperus communis) has one of the largest ranges of all vascular plant species. In several regions in Europe, however, populations are decreasing in size and number due to failing recruitment. One of the main causes for this failure is low seed viability. Observational evidence suggests that this is partly induced by climate warming, but our mechanistic understanding of this effect remains incomplete. Here, we experimentally assess the influence of temperature on two key developmental phases during sexual reproduction, i.e. gametogenesis and fertilisation (seed phase two, SP2) and embryo development (seed phase three, SP3). Along a latitudinal gradient from southern France to central Sweden, we installed a transplant experiment with shrubs originating from Belgium, a region with unusually low juniper seed viability. Seeds of both seed phases were sampled during three consecutive years, and seed viability assessed. Warming temperatures negatively affected the seed viability of both SP2 and SP3 seeds along the latitudinal gradient. Interestingly, the effect on embryo development (SP3) only occurred in the third year, i.e. when the gametogenesis and fertilisation also took place in warmer conditions. We found strong indications that this negative influence mostly acts via disrupting growth of the pollen tube, the development of the female gametophyte and fertilisation (SP2). This, in turn, can lead to failing embryo development, for example, due to nutritional problems. Our results confirm that climate warming can negatively affect seed viability of juniper. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

  11. Analyzing the effect of tool edge radius on cutting temperature in micro-milling process

    Science.gov (United States)

    Liang, Y. C.; Yang, K.; Zheng, K. N.; Bai, Q. S.; Chen, W. Q.; Sun, G. Y.

    2010-10-01

    Cutting heat is one of the important physical subjects in the cutting process. Cutting heat together with cutting temperature produced by the cutting process will directly have effects on the tool wear and the life as well as on the workpiece processing precision and surface quality. The feature size of the workpiece is usually several microns. Thus, the tiny changes of cutting temperature will affect the workpiece on the surface quality and accuracy. Therefore, cutting heat and temperature generated in micro-milling will have significantly different effect than the one in the traditional tools cutting. In this paper, a two-dimensional coupled thermal-mechanical finite element model is adopted to determine thermal fields and cutting temperature during the Micro-milling process, by using software Deform-2D. The effect of tool edge radius on effective stress, effective strain, velocity field and cutting temperature distribution in micro-milling of aluminum alloy Al2024-T6 were investigated and analyzed. Also, the transient cutting temperature distribution was simulated dynamically. The simulation results show that the cutting temperature in Micro-milling is lower than those occurring in conventional milling processes due to the small loads and low cutting velocity. With increase of tool edge radius, the maximum temperature region gradually occurs on the contact region between finished surfaced and flank face of micro-cutter, instead of the rake face or the corner of micro-cutter. And this phenomenon shows an obvious size effect.

  12. The effect of ambient temperature on the anti-D assay using the Auto Analyzer

    Science.gov (United States)

    Gunson, H. H.; Phillips, P. K.; Stratton, F.

    1974-01-01

    Using the AutoAnalyzer, the percentage agglutination effected by the anti-D antisera studied showed a varied dependence on the ambient temperature over the manifold subsequent to the incubation period at 37°C. This leads to assays which are a function of the ambient temperature. It is suggested that the entry of a relatively large volume of rouleaux-dispersing agent results in an elution of bound antibody to a new position of equilibrium, the shift being dependent on the particular equilibrium constant of the antibody and the rate of its attainment on the ambient temperature. A constant ambient temperature will lead to greater accuracy of anti-D assay. PMID:4212401

  13. Study of a Liquid Plug-Flow Thermal Cycling Technique Using a Temperature Gradient-Based Actuator

    Directory of Open Access Journals (Sweden)

    Yusuke Fuchiwaki

    2014-10-01

    Full Text Available Easy-to-use thermal cycling for performing rapid and small-volume DNA amplification on a single chip has attracted great interest in the area of rapid field detection of biological agents. For this purpose, as a more practical alternative to conventional continuous flow thermal cycling, liquid plug-flow thermal cycling utilizes a thermal gradient generated in a serpentine rectangular flow microchannel as an actuator. The transit time and flow speed of the plug flow varied drastically in each temperature zone due to the difference in the tension at the interface between temperature gradients. According to thermal distribution analyses in microfluidics, the plug flow allowed for a slow heating process, but a fast cooling process. The thermal cycle of the microfluid was consistent with the recommended temperature gradient for PCR. Indeed, amplification efficiency of the plug flow was superior to continuous flow PCR, and provided an impressive improvement over previously-reported flow microchannel thermal cycling techniques.

  14. Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro.

    Science.gov (United States)

    Blagodatskaya, Еvgenia; Blagodatsky, Sergey; Khomyakov, Nikita; Myachina, Olga; Kuzyakov, Yakov

    2016-02-29

    Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers ((14)C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.

  15. Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

    Directory of Open Access Journals (Sweden)

    Liu Shang-Bin

    2010-01-01

    Full Text Available Abstract To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of ΔT, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that ΔT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of ΔT > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary ΔT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications.

  16. Temperature Gradient Effect on Gas Discrimination Power of a Metal-Oxide Thin-Film Sensor Microarray

    Directory of Open Access Journals (Sweden)

    Joachim Goschnick

    2004-05-01

    Full Text Available Abstract: The paper presents results concerning the effect of spatial inhomogeneous operating temperature on the gas discrimination power of a gas-sensor microarray, with the latter based on a thin SnO2 film employed in the KAMINA electronic nose. Three different temperature distributions over the substrate are discussed: a nearly homogeneous one and two temperature gradients, equal to approx. 3.3 oC/mm and 6.7 oC/mm, applied across the sensor elements (segments of the array. The gas discrimination power of the microarray is judged by using the Mahalanobis distance in the LDA (Linear Discrimination Analysis coordinate system between the data clusters obtained by the response of the microarray to four target vapors: ethanol, acetone, propanol and ammonia. It is shown that the application of a temperature gradient increases the gas discrimination power of the microarray by up to 35 %.

  17. Sea surface temperature control of taxon specific phytoplankton production along an oligotrophic gradient in the Mediterranean Sea

    NARCIS (Netherlands)

    van de Poll, W.H.V.; Boute, P.G.; Rozema, P.D.; Buma, A.; Kulk, G.; Rijkenberg, M.J.

    2015-01-01

    The current study aimed to assess changes in phytoplankton composition and productivity along an oligotrophic gradient in relation to changes in sea surface temperature (SST). Phytoplankton pigments, nutrients, and physical water column properties were studied along a longitudinal transect in the

  18. Photosynthetic response to temperature of marine phytoplankton along a latitudinal gradient (16°N to 74°N)

    Science.gov (United States)

    Li, W. K. W.

    1985-11-01

    Photosynthesis-temperature relationships for natural phytoplankton assemblages were established by measuring the uptake of H 14CO 3 in freshly collected seawater samples incubated for 2 h across a shipboard laboratory temperature gradient. The minimum, optimum and maximum temperatures for photosynthesis, as well as the extent of photosynthetic change per unit temperature change in the suboptimal range, all decreased from low to high latitude. The empirical mathematical model of RATKOWSKYet al. (1983, Journal of Bacteriology, 154, 1222-1226) provided a good fit to the data.

  19. The two-dimensional kinetic ballooning theory for ion temperature gradient mode in tokamak

    Science.gov (United States)

    Xie, T.; Zhang, Y. Z.; Mahajan, S. M.; Hu, S. L.; He, Hongda; Liu, Z. Y.

    2017-10-01

    The two-dimensional (2D) kinetic ballooning theory is developed for the ion temperature gradient mode in an up-down symmetric equilibrium (illustrated via concentric circular magnetic surfaces). The ballooning transform converts the basic 2D linear gyro-kinetic equation into two equations: (1) the lowest order equation (ballooning equation) is an integral equation essentially the same as that reported by Dong et al., [Phys. Fluids B 4, 1867 (1992)] but has an undetermined Floquet phase variable, (2) the higher order equation for the rapid phase envelope is an ordinary differential equation in the same form as the 2D ballooning theory in a fluid model [Xie et al., Phys. Plasmas 23, 042514 (2016)]. The system is numerically solved by an iterative approach to obtain the (phase independent) eigen-value. The new results are compared to the two earlier theories. We find a strongly modified up-down asymmetric mode structure, and non-trivial modifications to the eigen-value.

  20. Return current instability driven by a temperature gradient in ICF plasmas

    Science.gov (United States)

    Rozmus, W.; Brantov, A. V.; Sherlock, M.; Bychenkov, V. Yu

    2018-01-01

    Hot plasmas with strong temperature gradients in inertial confinement fusion experiments are examined for ion acoustic instabilities produced by electron heat flow. The return current instability (RCI) due to a neutralizing current of cold electrons arising in response to a large electron heat flux has been considered. First, the linear threshold and growth rates are derived in the non-local regime of thermal transport. They are compared with the results of Vlasov–Fokker–Planck (VFP) simulations in one spatial dimension. Very good agreement has been found between kinetic VFP simulations and the linear theory of the RCI. A quasi-stationary state of ion acoustic turbulence (IAT) produced by the RCI is achieved in the VFP simulations. Saturation of the RCI involves heating of ions in the tail of the ion distribution function and convection of the enhanced ion acoustic fluctuations from the unstable region of the plasma. Further evolution of the IAT and its effects on absorption and transport are also discussed.

  1. Molecular dynamics simulation of Cu/Au thin films under temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qibin, E-mail: qibinli@cqu.edu.cn [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400030 (China); Peng, Xianghe [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Peng, Tiefeng, E-mail: pengtiefeng@cqu.edu.cn [State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Tang, Qizhong [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Zhang, Xiaomin [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400030 (China); Huang, Cheng [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China)

    2015-12-01

    Graphical abstract: Heat transportation in the thin films. - Highlights: • The coherent lattice interface is found at thin films after annealing. • The vacancies are observed clearly in the deposit thin films. • The defect and component will influence the energy transportation in the coatings. • The vacancies and lattice mismatch can enlarge the mobility of atoms. • The phonon transportation in thin films has no apparent rule. - Abstract: Three modulation period thin films, 1.8 nm Cu/3.6 nm Au, 2.7 nm Cu/2.7 nm Au and 3.6 nm Cu/1.8 nm Au, are obtained from deposition method and ideal modeling based on lattice constant, to examine their structures and thermophysical characteristics under temperature gradient. The coherent lattice interface is found both at deposit and ideal thin films after annealing. Also, the vacancies are observed clearly in the deposit thin films. The defect and component of thin films will influence the energy transportation in the coatings. The vacancies and lattice mismatch can enlarge the mobility of atoms and result in the failure of coating under the thermal stress. The power spectrum of atoms’ movement has no apparent rule for phonon transportation in thin films. The results are helpful to reveal the micro-mechanism and provide reasonable basis for the failure of metallic coatings.

  2. Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

    Science.gov (United States)

    Lakeman-Fraser, Poppy; Ewers, Robert M

    2014-07-22

    Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  3. Anomalous ion thermal transport in hot ion plasmas by the ion temperature gradient mode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.Y.; Horton, W. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies); Coppi, B. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Research Lab. of Electronics)

    1992-01-01

    Experiments show that the observed radial profiles of the ion thermal conductivity {chi}{sub i} have the opposite shapes with those obtained from the ion temperature gradient mode ({eta}{sub i} mode) turbulence model by the traditional mixing length estimate. In this work, this radial profile problem is reconsidered with an electromagnetic study of the linear stability of the toroidal {eta}{sub i} mode and a new rule for choosing the mixing length. It is first shown that the electromagnetic effect gives a significant stabilizing effect on the toroidal {eta}{sub i} mode, and that the observed reduction of {chi}{sub i}(r) in the core region can be explained by this electromagnetic effect. Secondly, in view of earlier numerical simulations showing the transfer of fluctuation energy to larger scales that those for the fastest growth rate, as well as fluctuation measurements indicating longer radial correlation lengths, a new mixing length formula is proposed to explain the radial increase of the {chi}{sub i}. It is shown the new formula fits well the observed {chi}{sub i}(r) profiles in two TFTR supershot discharges and also gives the scaling law in the current and the magnetic field which agrees better with experiment than the conventional formula.

  4. Anomalous ion thermal transport in hot ion plasmas by the ion temperature gradient mode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.Y.; Horton, W. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Coppi, B. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Research Lab. of Electronics

    1992-08-01

    Experiments show that the observed radial profiles of the ion thermal conductivity {chi}{sub i} have the opposite shapes with those obtained from the ion temperature gradient mode ({eta}{sub i} mode) turbulence model by the traditional mixing length estimate. In this work, this radial profile problem is reconsidered with an electromagnetic study of the linear stability of the toroidal {eta}{sub i} mode and a new rule for choosing the mixing length. It is first shown that the electromagnetic effect gives a significant stabilizing effect on the toroidal {eta}{sub i} mode, and that the observed reduction of {chi}{sub i}(r) in the core region can be explained by this electromagnetic effect. Secondly, in view of earlier numerical simulations showing the transfer of fluctuation energy to larger scales that those for the fastest growth rate, as well as fluctuation measurements indicating longer radial correlation lengths, a new mixing length formula is proposed to explain the radial increase of the {chi}{sub i}. It is shown the new formula fits well the observed {chi}{sub i}(r) profiles in two TFTR supershot discharges and also gives the scaling law in the current and the magnetic field which agrees better with experiment than the conventional formula.

  5. Ion scale nonlinear interaction triggered by disparate scale electron temperature gradient mode

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Chanho, E-mail: moon@nifs.ac.jp [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Kobayashi, Tatsuya; Itoh, Kimitaka [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Hatakeyama, Rikizo; Kaneko, Toshiro [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2015-05-15

    We have observed that the disparate scale nonlinear interactions between the high-frequency (∼0.4 MHz) electron temperature gradient (ETG) mode and the ion-scale low-frequency fluctuations (∼kHz) were enhanced when the amplitude of the ETG mode exceeded a certain threshold. The dynamics of nonlinear coupling between the ETG mode and the drift wave (DW) mode has already been reported [C. Moon, T. Kaneko, and R. Hatakeyama, Phys. Rev. Lett. (2013)]. Here, we have newly observed that another low-frequency fluctuation with f ≃ 3.6 kHz, i.e., the flute mode, was enhanced, corresponding to the saturation of the DW mode growth. Specifically, the bicoherence between the flute mode and the DW mode reaches a significant level when the ∇T{sub e}/T{sub e} strength exceeded 0.54 cm{sup −1}. Thus, it is shown that the ETG mode energy was transferred to the DW mode, and then the energy was ultimately transferred to the flute mode, which was triggered by the disparate scale nonlinear interactions between the ETG and ion-scale low-frequency modes.

  6. Biogeography of pelagic bacterioplankton across an antagonistic temperature-salinity gradient in the Red Sea

    KAUST Repository

    Ngugi, David

    2011-12-01

    The Red Sea is a unique marine ecosystem with contrasting gradients of temperature and salinity along its north-to-south axis. It is an extremely oligotrophic environment that is characterized by perpetual year-round water column stratification, high annual solar irradiation, and negligible riverine and precipitation inputs. In this study, we investigated whether the contemporary environmental conditions shape community assemblages by pyrosequencing 16S rRNA genes of bacteria in surface water samples collected from the northeastern half of this water body. A combined total of 1855 operational taxonomic units (OTUs) were recovered from the \\'small-cell\\' and \\'large-cell\\' fractions. Here, a few major OTUs affiliated with Cyanobacteria and Proteobacteria accounted for â93% of all sequences, whereas a tail of \\'rare\\' OTUs represented most of the diversity. OTUs allied to Surface 1a/b SAR11 clades and Prochlorococcus related to the high-light-adapted (HL2) ecotype were the most widespread and predominant sequence types. Interestingly, the frequency of taxa that are typically found in the upper mesopelagic zone was significantly elevated in the northern transects compared with those in the central, presumably as a direct effect of deep convective mixing in the Gulf of Aqaba and water exchange with the northern Red Sea. Although temperature was the best predictor of species richness across all major lineages, both spatial and environmental distances correlated strongly with phylogenetic distances. Our results suggest that the bacterial diversity of the Red Sea is as high as in other tropical seas and provide evidence for fundamental differences in the biogeography of pelagic communities between the northern and central regions. © 2011 Blackwell Publishing Ltd.

  7. The impact of distance and a shifting temperature gradient on genetic connectivity across a heterogeneous landscape.

    Science.gov (United States)

    Rossetto, Maurizio; Thurlby, Katie Ag; Offord, Catherine A; Allen, Chris B; Weston, Peter H

    2011-05-18

    Inter-population distance and differences in breeding times are barriers to reproduction that can contribute to genotypic differentiation between populations. Temporal changes in environmental conditions and local selective processes can further contribute to the establishment of reproductive barriers. Telopea speciosissima (Proteaceae) is an excellent subject for studying the effect of geographic, edaphic and phenological heterogeneity on genotypic differentiation because previous studies show that these factors are correlated with morphological variation. Molecular, morphological and environmental datasets were combined to characterise the relative influence of these factors on inter-population differentiation, and Bayesian analyses were used to investigate current levels of admixture between differentiated genomes. A landscape genetic approach involving molecular and morphological analyses identified three endpoints of differentiated population groups: coastal, upland and southern. The southern populations, isolated from the other populations by an edaphic barrier, show low migration and no evidence of admixture with other populations. Amongst the northern populations, coastal and upland populations are connected along a skewed altitudinal gradient by genetically intermediate populations. The strong association between temperature and flowering time in Telopea speciosissima was shown to maintain a temporally unstable reproductive barrier between coastal and upland populations. Substrate-mediated allopatry appears to be responsible for long-term genetic isolation of the southern populations. However, the temperature-dependent reproductive barrier between upland and coastal populations bears the genetic signature of temporal adjustments. The extreme climatic events of the last glacial maximum are likely to have caused more complete allochronic isolation between upland and coastal populations, as well as exerting increased selective pressure upon local genomes

  8. Impacts of light and temperature on shoot branching gradient and expression of strigolactone synthesis and signalling genes in rose.

    Science.gov (United States)

    Djennane, Samia; Hibrand-Saint Oyant, Laurence; Kawamura, Koji; Lalanne, David; Laffaire, Michel; Thouroude, Tatiana; Chalain, Séverine; Sakr, Soulaiman; Boumaza, Rachid; Foucher, Fabrice; Leduc, Nathalie

    2014-03-01

    Light and temperature are two environmental factors that deeply affect bud outgrowth. However, little is known about their impact on the bud burst gradient along a stem and their interactions with the molecular mechanisms of bud burst control. We investigated this question in two acrotonic rose cultivars. We demonstrated that the darkening of distal buds or exposure to cold (5 °C) prior to transfer to mild temperatures (20 °C) both repress acrotony, allowing the burst of quiescent medial and proximal buds. We sequenced the strigolactone pathway MAX-homologous genes in rose and studied their expression in buds and internodes along the stem. Only expressions of RwMAX1, RwMAX2 and RwMAX4 were detected. Darkening of the distal part of the shoot triggered a strong increase of RwMAX2 expression in darkened buds and bark-phloem samples, whereas it suppressed the acropetal gradient of the expression of RwMAX1 observed in stems fully exposed to light. Cold treatment induced an acropetal gradient of expression of RwMAX1 in internodes and of RwMAX2 in buds along the stem. Our results suggest that the bud burst gradient along the stem cannot be explained by a gradient of expression of RwMAX genes but rather by their local level of expression at each individual position. © 2013 John Wiley & Sons Ltd.

  9. Analyzing the impact of ambient temperature indicators on transformer life in different regions of Chinese mainland.

    Science.gov (United States)

    Bai, Cui-fen; Gao, Wen-Sheng; Liu, Tong

    2013-01-01

    Regression analysis is applied to quantitatively analyze the impact of different ambient temperature characteristics on the transformer life at different locations of Chinese mainland. 200 typical locations in Chinese mainland are selected for the study. They are specially divided into six regions so that the subsequent analysis can be done in a regional context. For each region, the local historical ambient temperature and load data are provided as inputs variables of the life consumption model in IEEE Std. C57.91-1995 to estimate the transformer life at every location. Five ambient temperature indicators related to the transformer life are involved into the partial least squares regression to describe their impact on the transformer life. According to a contribution measurement criterion of partial least squares regression, three indicators are conclusively found to be the most important factors influencing the transformer life, and an explicit expression is provided to describe the relationship between the indicators and the transformer life for every region. The analysis result is applicable to the area where the temperature characteristics are similar to Chinese mainland, and the expressions obtained can be applied to the other locations that are not included in this paper if these three indicators are known.

  10. Analyzing the Impact of Ambient Temperature Indicators on Transformer Life in Different Regions of Chinese Mainland

    Directory of Open Access Journals (Sweden)

    Cui-fen Bai

    2013-01-01

    Full Text Available Regression analysis is applied to quantitatively analyze the impact of different ambient temperature characteristics on the transformer life at different locations of Chinese mainland. 200 typical locations in Chinese mainland are selected for the study. They are specially divided into six regions so that the subsequent analysis can be done in a regional context. For each region, the local historical ambient temperature and load data are provided as inputs variables of the life consumption model in IEEE Std. C57.91-1995 to estimate the transformer life at every location. Five ambient temperature indicators related to the transformer life are involved into the partial least squares regression to describe their impact on the transformer life. According to a contribution measurement criterion of partial least squares regression, three indicators are conclusively found to be the most important factors influencing the transformer life, and an explicit expression is provided to describe the relationship between the indicators and the transformer life for every region. The analysis result is applicable to the area where the temperature characteristics are similar to Chinese mainland, and the expressions obtained can be applied to the other locations that are not included in this paper if these three indicators are known.

  11. Analyzes of students’ higher-order thinking skills of heat and temperature concept

    Science.gov (United States)

    Slamet Budiarti, Indah; Suparmi, A.; Sarwanto; Harjana

    2017-11-01

    High order thinking skills refer to three highest domains of the revised Bloom Taxonomy. The aims of the research were to analyze the student’s higher-order thinking skills of heat and temperature concept. The samples were taken by purposive random sampling technique consisted of 85 high school students from 3 senior high schools in Jayapura city. The descriptive qualitative method was employed in this study. The data were collected by using tests and interviews regarding the subject matters of heat and temperature. Based on the results of data analysis, it was concluded that 68.24% of the students have a high order thinking skills in the analysis, 3.53% of the students have a high order thinking skills in evaluating, and 0% of the students have a high order thinking skills in creation.

  12. Subduction factory in an ampoule: Experiments on sediment-peridotite interaction under temperature gradient conditions

    Science.gov (United States)

    Woodland, A. B.; Bulatov, V. K.; Brey, G. P.; Girnis, A. V.; Höfer, H. E.; Gerdes, A.

    2018-02-01

    To better understand processes above subducted oceanic slabs, we have undertaken experiments with juxtaposed sediment and peridotite layers at pressures of 7.5 and 10.5 GPa at a controlled temperature gradient from ∼100 to ∼500 °C per a sample length of ∼3 mm. The sediment starting material contains H2O (6.9 wt%) and CO2 (5.9 wt%) and has a major-element composition similar to GLOSS (Plank and Langmuir, 1998) doped with trace elements at 10-100 ppm levels. Several experiments were conducted with ∼0.5 wt% Cl or F. The peridotite layer is composed of natural olivine (66 wt%), orthopyroxene (27 wt%) and garnet (7 wt%) mixed with ∼15 wt% graphite. Several experimental configurations were investigated, but the "basic" setup has the sediment layer at the bottom in the cold zone (400-1200 °C) overlain by peridotite at 900-1500 °C. The temperature distribution was determined by two thermocouples and orthopyroxene-garnet thermometry. Features common to many experiments are (1) the development of multiple layers of various lithologies and a pool of hydrous silicate or carbonate-silicate melt in the hottest part of the capsule; (2) replacement of olivine by orthopyroxene in the metaperidotite; (3) preservation and growth of garnet and local development of magnesite in the metaperidotite layer; (4) enrichment in garnet within the metasediment layer at the contact with the metaperidotite; (5) formation of a clinopyroxene-garnet assemblage at the bottom (the coldest part); (6) presence of K-bearing phases (phlogopite or phengite) and carbonates in the metasediment layer only at temperatures <700 °C; and (7) occurrence of accessory zircon, rutile and phosphates in the coldest regions. In terms of element redistribution, the peridotite becomes strongly enriched in SiO2 compared to the starting composition, and the sediment gains MgO, FeO and Cr2O3. Potassium is fully extracted into the melt, while Na and Ca are largely retained in the coldest part of the metasediment

  13. Both experimental study and numerical modelling of the effect of temperature gradient on CO2 injection

    Science.gov (United States)

    Corvisier, J.; Lagneau, V.; Jobard, E.; Sterpenich, J.; Pironon, J.

    2010-12-01

    to a more important carbonates dissolution, thus to increases of CO2 fugacity and consequently of the global pressure. Furthermore, the calcium content tends to be greater in this cold-dissolution zone then Ca diffuses towards the hotter zone locally and it implies calcite precipitation. As evidence of this phenomenon, plugs, related to massive calcite precipitation, are observed in these regions and newly crystallized calcite can be seen on SEM images. In order to clearly understand the reasons of the observed behaviour, numerical computations performed with the reaction-transport code HYTEC have to be run. Several scenarios can thus be simulated to check various assumptions. Firstly, different initial repartitions of the CO2 can be tested: in some kind of reservoir in the cold/injection zone or everywhere in the autoclave (due to high initial pressure gradient). Secondly, the competition between the implied processes, their respective kinetics and their temperature dependance can be assessed too: thermodynamics and/or kinetics of chemical reactions and transport kinetics (diffusion). Modeling becomes then of great help to interpret the experimental results and even to better design the evolution of the experimental set-up.

  14. Crustal temperature structure derived from a ground temperature gradient chart of Hokkaido; Hokkaido no chion kobaizu kara motometa chikakunai ondo kozo

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, Y. [Geological Survey of Japan, Tsukuba (Japan); Akita, F. [Hokkaido Geological Survey, Sapporo (Japan); Nagumo, S. [Oyo Corp., Tokyo (Japan)

    1997-05-27

    The Hokkaido Underground Resources Investigation Institute has prepared in 1995 a detailed temperature gradient chart that shows local anomalies around volcanoes. This paper describes an attempt to derive crustal temperature structure of Hokkaido from the above data. The model was hypothesized as a primary model in which no thermal convection exists. In volcanic and geothermal areas which show a temperature gradient of more than 100 {degree}C km {sup -1}, a solidus temperature is reached at a depth shallower than 10 km. Below the volcanic chain forming the Chishima arc, a partially melted region exists in a width of about 100 km. Most of the areas in the southern Hokkaido have the temperature reached the solidus temperature in the crust. On the other hand, in most of the areas of the forefront side, no solidus temperature is reached in the crust. In the temperature structure of a cross section crossing almost orthogonally with the volcanic front passing through Mt. Daisetsu, a high temperature area reaches to a shallow portion beneath Mt. Daisetsu, where the depth at which the solidus temperature is reached is 10 km or shallower. The range of area where the solidus depth is shallower than 10 km has a south-west width of about 40 km. This means that a partially melted area with a size of 40 km in the horizontal direction exists at a depth of several kilometers. 20 refs., 3 figs.

  15. Influence of vertical temperature gradients on wafer quality and cell efficiency of Seed-assisted high-performance multi-crystalline silicon

    Science.gov (United States)

    Chen, Wei; Wang, Quanzhi; Yang, Deren; Li, Lin Dong; Yu, Xue Gong; Wang, Lei; Jin, Hao

    2017-06-01

    The effect of vertical temperature gradients on the performance of Seed-assisted high-performance (HP) multi-crystalline silicon (mc-Si) is investigated by numerical simulations and contrast experiments. The vertical temperature gradients are designed by keeping the temperatures at the top and lowering the temperatures at the bottom. Two Seed-assisted HP mc-Si ingots were grown by means of a larger and a conventional vertical temperature gradient. It is found that the larger vertical temperature gradients result in the more parallel growth direction of grains and the longer crystal growth length, increases the percentages of grain orientation and random grain boundaries, which are benefit for crystal quality. The experimental results also confirm that the wafer of ingot grown with a larger vertical gradient has the better quality, and their cell efficiency can increase.

  16. Investigation of the effects of pressure gradient, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes

    Science.gov (United States)

    Nagamatsu, H. T.; Duffy, R. E.

    1984-01-01

    Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without pressure gradient. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse pressure gradient over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without pressure gradients for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.

  17. Development and evaluation of a workpiece temperature analyzer (WPTA) for industrial furances (Phase 1)

    Energy Technology Data Exchange (ETDEWEB)

    1991-10-01

    This project is directed toward the research, development, and evaluation of a viable commercial product-a workpiece temperature measurement analyzer (WPTA) for fired furnaces based on unique radiation properties of surfaces. This WPTA will provide for more uniform, higher quality products and reduce product rejects as well as permit the optimum use of energy. The WPTA may also be utilized in control system applications including metal heat treating, forging furnaces, and ceramic firing furnaces. A large market also exists in the chemical process and refining industry. WPTA applications include the verification of product temperature/time cycles, and use as a front-end sensor for automatic feedback control systems. This report summarizes the work performed in Phase 1 of this three-phase project. The work Phase 1 included the application evaluation; the evaluation of present technologies and limitations; and the development of a preliminary conceptual WPTA design, including identification of technical and economic benefits. Recommendations based on the findings of this report include near-term enhancement of the capabilities of the Pyrolaser, and long-term development of an instrument based on Raman Spectroscopy. Development of the Pyrofiber, fiberoptics version of the Pyrolaser, will be a key to solving present problems involving specularity, measurement angle, and costs of multipoint measurement. Extending the instrument's measurement range to include temperatures below 600{degrees}C will make the product useful for a wider range of applications. The development of Raman Spectroscopy would result in an instrument that could easily be adapted to incorporate a wealth of additional nondestructive analytical capabilities, including stress/stain indication, crystallography, species concentrations, corrosion studies, and catalysis studies, in addition to temperature measurement. 9 refs., 20 figs., 16 tabs.

  18. Sea-surface temperature gradients across blue whale and sea turtle foraging trajectories off the Baja California Peninsula, Mexico

    Science.gov (United States)

    Etnoyer, Peter; Canny, David; Mate, Bruce R.; Morgan, Lance E.; Ortega-Ortiz, Joel G.; Nichols, Wallace J.

    2006-02-01

    Sea-surface temperature (SST) fronts are integral to pelagic ecology in the North Pacific Ocean, so it is necessary to understand their character and distribution, and the way these features influence the behavior of endangered and highly migratory species. Here, telemetry data from sixteen satellite-tagged blue whales ( Balaenoptera musculus) and sea turtles ( Caretta caretta, Chelonia mydas, and Lepidochelys olivacea) are employed to characterize 'biologically relevant' SST fronts off Baja California Sur. High residence times are used to identify presumed foraging areas, and SST gradients are calculated across advanced very high resolution radiometer (AVHRR) images of these regions. The resulting values are compared to classic definitions of SST fronts in the oceanographic literature. We find subtle changes in surface temperature (between 0.01 and 0.10 °C/km) across the foraging trajectories, near the lowest end of the oceanographic scale (between 0.03 and 0.3 °C/km), suggesting that edge-detection algorithms using gradient thresholds >0.10 °C/km may overlook pelagic habitats in tropical waters. We use this information to sensitize our edge-detection algorithm, and to identify persistent concentrations of subtle SST fronts in the Northeast Pacific Ocean between 2002 and 2004. The lower-gradient threshold increases the number of fronts detected, revealing more potential habitats in different places than we find with a higher-gradient threshold. This is the expected result, but it confirms that pelagic habitat can be overlooked, and that the temperature gradient parameter is an important one.

  19. Experimental and Computational Studies of Temperature Gradient Driven Molecular Transport in Gas Flows through Nano/Micro-Scale Channels

    OpenAIRE

    Han, Yen-Lin; Alexeenko, Alina A; Young, Marcus; Muntz, Eric Phillip

    2007-01-01

    Studies at the University of Southern California have shown that an unconventional solid-state device, the Knudsen Compressor, can be operated as a micro-scale pump or compressor. The critical components of Knudsen Compressors are gas transport membranes, which can be formed from porous materials or densely packed parallel arrays of channels. An applied temperature gradient across a transport membrane creates a thermal creep pumping action. Experimental and computational techniques that have ...

  20. Population dynamics of two antilisterial cheese surface consortia revealed by temporal temperature gradient gel electrophoresis

    Directory of Open Access Journals (Sweden)

    Hasler Madlen

    2010-03-01

    Full Text Available Abstract Background Surface contamination of smear cheese by Listeria spp. is of major concern for the industry. Complex smear ecosystems have been shown to harbor antilisterial potential but the microorganisms and mechanisms involved in the inhibition mostly remain unclear, and are likely related to complex interactions than to production of single antimicrobial compounds. Bacterial biodiversity and population dynamics of complex smear ecosystems exhibiting antilisterial properties in situ were investigated by Temporal temperature gradient gel electrophoresis (TTGE, a culture independent technique, for two microbial consortia isolated from commercial Raclette type cheeses inoculated with defined commercial ripening cultures (F or produced with an old-young smearing process (M. Results TTGE revealed nine bacterial species common to both F and M consortia, but consortium F exhibited a higher diversity than consortium M, with thirteen and ten species, respectively. Population dynamics were studied after application of the consortia on fresh-produced Raclette cheeses. TTGE analyses revealed a similar sequential development of the nine species common to both consortia. Beside common cheese surface bacteria (Staphylococcus equorum, Corynebacterium spp., Brevibacterium linens, Microbacterium gubbeenense, Agrococcus casei, the two consortia contained marine lactic acid bacteria (Alkalibacterium kapii, Marinilactibacillus psychrotolerans that developed early in ripening (day 14 to 20, shortly after the growth of staphylococci (day 7. A decrease of Listeria counts was observed on cheese surface inoculated at day 7 with 0.1-1 × 102 CFU cm-2, when cheeses were smeared with consortium F or M. Listeria counts went below the detection limit of the method between day 14 and 28 and no subsequent regrowth was detected over 60 to 80 ripening days. In contrast, Listeria grew to high counts (105 CFU cm-2 on cheeses smeared with a defined surface culture

  1. How important are internal temperature gradients in french straws during freezing of bovine sperm in nitrogen vapor?

    Science.gov (United States)

    Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

    2013-01-01

    The subject of present work was to predict internal temperature gradients developed during freezing of bovine sperm diluted in extender, packaged in 0.5 ml French plastic straws and suspended in static liquid nitrogen vapor at -100 degree C. For this purpose, a mathematical heat transfer model previously developed to predict freezing times (phase change was considered) of semen/extender packaged in straw was extended to predict internal temperature gradients during the cooling/freezing process. Results showed maximum temperature differences between the centre and the periphery of semen/extender "liquid" column was 1.5 degree C for an external heat transfer coefficient, h = 15 W per (m(2) K), and only 0.5 degree C for h = 5 W per (m(2) K). It is concluded that if a thermocouple wire were inserted in a 0.5 ml plastic straw to monitor the freezing process in nitrogen vapor, its radial position would have little importance since expected internal gradients may be safely neglected. This finding facilitates the interpretation of freezing rates in 0.5 ml plastic straws immersed in nitrogen vapor over liquid nitrogen, a widely used method for cryopreservation of bovine spermatozoa.

  2. Optical performance of the SO/PHI full disk telescope due to temperature gradients effect on the heat rejection entrance window

    Science.gov (United States)

    Garranzo, D.; Núñez, A.; Zuluaga-Ramírez, P.; Barandiarán, J.; Fernández-Medina, A.; Belenguer, T.; Álvarez-Herrero, A.

    2017-11-01

    The Polarimetric Helioseismic Imager for Solar Orbiter (SO/PHI) is an instrument on board in the Solar Orbiter mission. The Full Disk Telescope (FDT) will have the capability of providing images of the solar disk in all orbital faces with an image quality diffraction-limited. The Heat Rejection Entrance Window (HREW) is the first optical element of the instrument. Its function is to protect the instrument by filtering most of the Solar Spectrum radiation. The HREW consists of two parallel-plane plates made from Suprasil and each surface has a coating with a different function: an UV shield coating, a low pass band filter coating, a high pass band filter coating and an IR shield coating, respectively. The temperature gradient on the HREW during the mission produces a distortion of the transmitted wave-front due to the dependence of the refractive index with the temperature (thermo-optic effect) mainly. The purpose of this work is to determine the capability of the PHI/FDT refocusing system to compensate this distortion. A thermal gradient profile has been considered for each surface of the plates and a thermal-elastic analysis has been done by Finite Element Analysis to determine the deformation of the optical elements. The Optical Path Difference (OPD) between the incident and transmitted wavefronts has been calculated as a function of the ray tracing and the thermo-optic effect on the optical properties of Suprasil (at the work wavelength of PHI) by means of mathematical algorithms based on the 3D Snell Law. The resultant wavefronts have been introduced in the optical design of the FDT to evaluate the performance degradation of the image at the scientific focal plane and to estimate the capability of the PHI refocusing system for maintaining the image quality diffraction-limited. The analysis has been carried out considering two different situations: thermal gradients due to on axis attitude of the instrument and thermal gradients due to 1° off pointing attitude

  3. Characterization of an urban-rural CO 2 /temperature gradient and associated changes in initial plant productivity during secondary succession

    Energy Technology Data Exchange (ETDEWEB)

    Ziska, L. H.; Bunce, J. A.; Goins, E. W.

    2004-05-01

    To examine the impact of climate change on vegetative productivity, we exposed fallow agricultural soil to an in situ temperature and CO2 gradient between urban, suburban and rural areas in 2002. Along the gradient, average daytime CO2 concentration increased by 21% and maximum (daytime) and minimum (nighttime) daily temperatures increased by 1.6 and 3.3°C, respectively in an urban relative to a rural location. Consistent location differences in soil temperature were also ascertained. No other consistent differences in meteorological variables (e.g. wind speed, humidity, PAR, tropospheric ozone) as a function of urbanization were documented. The urban-induced environmental changes that were observed were consistent with most short-term (~50 year) global change scenarios regarding CO2 concentration and air temperature. Productivity, determined as final above-ground biomass, and maximum plant height were positively affected by daytime and soil temperatures as well as enhanced [CO2], increasing 60 and 115% for the suburban and urban sites, respectively, relative to the rural site. While long-term data are needed, these initial results suggest that urban environments may act as a reasonable surrogate for investigating future climatic change in vegetative communities.

  4. Mangrove expansion and contraction at a poleward range limit: Climate extremes and land-ocean temperature gradients

    Science.gov (United States)

    Osland, Michael J.; Day, Richard H.; Hall, Courtney T.; Brumfield, Marisa D; Dugas, Jason; Jones, William R.

    2017-01-01

    Within the context of climate change, there is a pressing need to better understand the ecological implications of changes in the frequency and intensity of climate extremes. Along subtropical coasts, less frequent and warmer freeze events are expected to permit freeze-sensitive mangrove forests to expand poleward and displace freeze-tolerant salt marshes. Here, our aim was to better understand the drivers of poleward mangrove migration by quantifying spatiotemporal patterns in mangrove range expansion and contraction across land-ocean temperature gradients. Our work was conducted in a freeze-sensitive mangrove-marsh transition zone that spans a land-ocean temperature gradient in one of the world's most wetland-rich regions (Mississippi River Deltaic Plain; Louisiana, USA). We used historical air temperature data (1893-2014), alternative future climate scenarios, and coastal wetland coverage data (1978-2011) to investigate spatiotemporal fluctuations and climate-wetland linkages. Our analyses indicate that changes in mangrove coverage have been controlled primarily by extreme freeze events (i.e., air temperatures below a threshold zone of -6.3 to -7.6 °C). We expect that in the past 121 years, mangrove range expansion and contraction has occurred across land-ocean temperature gradients. Mangrove resistance, resilience, and dominance were all highest in areas closer to the ocean where temperature extremes were buffered by large expanses of water and saturated soil. Under climate change, these areas will likely serve as local hotspots for mangrove dispersal, growth, range expansion, and displacement of salt marsh. Collectively, our results show that the frequency and intensity of freeze events across land-ocean temperature gradients greatly influences spatiotemporal patterns of range expansion and contraction of freeze-sensitive mangroves. We expect that, along subtropical coasts, similar processes govern the distribution and abundance of other freeze

  5. Base flow-driven shifts in tropical stream temperature regimes across a mean annual rainfall gradient

    Science.gov (United States)

    Ayron M. Strauch; Richard A. MacKenzie; Ralph W. Tingley

    2017-01-01

    Climate change is expected to affect air temperature and watershed hydrology, but the degree to which these concurrent changes affect stream temperature is not well documented in the tropics. How stream temperature varies over time under changing hydrologic conditions is difficult to isolate from seasonal changes in air temperature. Groundwater and bank storage...

  6. Growth and Demography of the Solitary Scleractinian Coral Leptopsammia pruvoti along a Sea Surface Temperature Gradient in the Mediterranean Sea

    Science.gov (United States)

    Caroselli, Erik; Zaccanti, Francesco; Mattioli, Guido; Falini, Giuseppe; Levy, Oren; Dubinsky, Zvy; Goffredo, Stefano

    2012-01-01

    The demographic traits of the solitary azooxanthellate scleractinian Leptopsammia pruvoti were determined in six populations on a sea surface temperature (SST) gradient along the western Italian coasts. This is the first investigation of the growth and demography characteristics of an azooxanthellate scleractinian along a natural SST gradient. Growth rate was homogeneous across all populations, which spanned 7 degrees of latitude. Population age structures differed between populations, but none of the considered demographic parameters correlated with SST, indicating possible effects of local environmental conditions. Compared to another Mediterranean solitary scleractinian, Balanophyllia europaea, zooxanthellate and whose growth, demography and calcification have been studied in the same sites, L. pruvoti seems more tolerant to temperature increase. The higher tolerance of L. pruvoti, relative to B. europaea, may rely on the absence of symbionts, and thus the lack of an inhibition of host physiological processes by the heat-stressed zooxanthellae. However, the comparison between the two species must be taken cautiously, due to the likely temperature differences between the two sampling depths. Increasing research effort on determining the effects of temperature on the poorly studied azooxanthellate scleractinians may shed light on the possible species assemblage shifts that are likely to occur during the current century as a consequence of global climatic change. PMID:22675495

  7. Characterization of Temperature Profiles in Skin and Transdermal Delivery System When Exposed to Temperature Gradients In Vivo and In Vitro.

    Science.gov (United States)

    Zhang, Qian; Murawsky, Michael; LaCount, Terri; Hao, Jinsong; Kasting, Gerald B; Newman, Bryan; Ghosh, Priyanka; Raney, Sam G; Li, S Kevin

    2017-07-01

    Performance of a transdermal delivery system (TDS) can be affected by exposure to elevated temperature, which can lead to unintended safety issues. This study investigated TDS and skin temperatures and their relationship in vivo, characterized the effective thermal resistance of skin, and identified the in vitro diffusion cell conditions that would correlate with in vivo observations. Experiments were performed in humans and in Franz diffusion cells with human cadaver skin to record skin and TDS temperatures at room temperature and with exposure to a heat flux. Skin temperatures were regulated with two methods: a heating lamp in vivo and in vitro, or thermostatic control of the receiver chamber in vitro. In vivo basal skin temperatures beneath TDS at different anatomical sites were not statistically different. The maximum tolerable skin surface temperature was approximately 42-43°C in vivo. The temperature difference between skin surface and TDS surface increased with increasing temperature, or with increasing TDS thermal resistance in vivo and in vitro. Based on the effective thermal resistance of skin in vivo and in vitro, the heating lamp method is an adequate in vitro method. However, the in vitro-in vivo correlation of temperature could be affected by the thermal boundary layer in the receiver chamber.

  8. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming.

    NARCIS (Netherlands)

    Rinnan, R.; Rousk, J.; Yergeau, E.; Kowalchuk, G.A.; Baath, E.

    2009-01-01

    Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short-term temperature dependencies of Antarctic soil bacterial community growth rates, using

  9. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

    NARCIS (Netherlands)

    Rinnan, R.; Rousk, J.; Yergeau, E.; Kowalchuk, G.A.; Baath, E.

    2009-01-01

    Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short-term temperature dependencies of Antarctic soil bacterial community growth rates, using

  10. Effect of a temperature gradient on Sphagnum fallax and its associated living microbial communities: a study under controlled conditions.

    Science.gov (United States)

    Jassey, Vincent E J; Gilbert, Daniel; Binet, Philippe; Toussaint, Marie-Laure; Chiapusio, Geneviève

    2011-03-01

    Microbial communities living in Sphagnum are known to constitute early indicators of ecosystem disturbances, but little is known about their response (including their trophic relationships) to climate change. A microcosm experiment was designed to test the effects of a temperature gradient (15, 20, and 25°C) on microbial communities including different trophic groups (primary producers, decomposers, and unicellular predators) in Sphagnum segments (0-3 cm and 3-6 cm of the capitulum). Relationships between microbial communities and abiotic factors (pH, conductivity, temperature, and polyphenols) were also studied. The density and the biomass of testate amoebae in Sphagnum upper segments increased and their community structure changed in heated treatments. The biomass of testate amoebae was linked to the biomass of bacteria and to the total biomass of other groups added and, thus, suggests that indirect effects on the food web structure occurred. Redundancy analysis revealed that microbial assemblages differed strongly in Sphagnum upper segments along a temperature gradient in relation to abiotic factors. The sensitivity of these assemblages made them interesting indicators of climate change. Phenolic compounds represented an important explicative factor in microbial assemblages and outlined the potential direct and (or) indirect effects of phenolics on microbial communities.

  11. Calcification, photosynthesis and mucus production of the coral Pocillopora verrucosa along the nutrient and temperature gradient of the Red Sea

    Science.gov (United States)

    Sawall, Yvonne; Al-Sofyani, Abdulmohsin

    2013-04-01

    The Red Sea is characterized by a large latitudinal gradient, most important an increase in nutrients and in temperature (21-33°C) from N to S, featuring challenging conditions during summer in the S. The metabolism of the widely distributed coral species Pocillopora verrucosa was investigated in situ along the gradient in summer and in winter to evaluate its acclimatization mechanisms to these variable and partly extreme environmental conditions. Calcification rates revealed clear seasonal pattern with more than 2-fold increased rates in the Northern reefs during summer and more than 1.5-fold increased rates in the Southern reefs during winter. This pattern strongly relates with temperature, where maximum calcification rates occurred at ~29°C independent of latitude and nutrients in the water. Furthermore, diel calcification rates decreased with light intensity during summer in the S, indicating energy allocation towards stress mitigation, possibly caused by co-occurring high SST and high light intensity. Photosynthesis, as the main energy supply, followed the gradient stronger during winter with a 3-fold increase from N to S and was generally higher in winter than in summer, except at the most Northern site. Hence, energy consuming calcification could only partly be related to photosynthesis with a higher correlation during winter than in summer. Mucus release increased >5-fold from N to S during winter and summer, while mucus release was generally higher during summer. This indicates that a substantial amount of energy in Southern corals was allocated towards protection from sedimentation in nutrient enriched waters and possibly towards the protection from heat-related stressors, e.g. enhanced bacterial pressure. These acclimatization mechanisms of P. verrucosa to varying temperature and nutrient regimes explain its success and wide physiological niche in the Red Sea, although conditions may be rather marginal for coral growth in some areas.

  12. Limited tolerance by insects to high temperatures across tropical elevational gradients and the implications of global warming for extinction.

    Science.gov (United States)

    García-Robledo, Carlos; Kuprewicz, Erin K; Staines, Charles L; Erwin, Terry L; Kress, W John

    2016-01-19

    The critical thermal maximum (CTmax), the temperature at which motor control is lost in animals, has the potential to determine if species will tolerate global warming. For insects, tolerance to high temperatures decreases with latitude, suggesting that similar patterns may exist along elevational gradients as well. This study explored how CTmax varies among species and populations of a group of diverse tropical insect herbivores, the rolled-leaf beetles, across both broad and narrow elevational gradients. Data from 6,948 field observations and 8,700 museum specimens were used to map the elevational distributions of rolled-leaf beetles on two mountains in Costa Rica. CTmax was determined for 1,252 individual beetles representing all populations across the gradients. Initial morphological identifications suggested a total of 26 species with populations at different elevations displaying contrasting upper thermal limits. However, compared with morphological identifications, DNA barcodes (cytochrome oxidase I) revealed significant cryptic species diversity. DNA barcodes identified 42 species and haplotypes across 11 species complexes. These 42 species displayed much narrower elevational distributions and values of CTmax than the 26 morphologically defined species. In general, species found at middle elevations and on mountaintops are less tolerant to high temperatures than species restricted to lowland habitats. Species with broad elevational distributions display high CTmax throughout their ranges. We found no significant phylogenetic signal in CTmax, geography, or elevational range. The narrow variance in CTmax values for most rolled-leaf beetles, especially high-elevation species, suggests that the risk of extinction of insects may be substantial under some projected rates of global warming.

  13. Link between convection and meridional gradient of sea surface temperature in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; Shetye, S.R.; Joseph, P.V.

    of SST in the bay. We show that convection sets in within a week of the SST difference between the northern and southern bay exceeding 0.75openbullet C. We begin by presenting the data and definitions (Section 2) and the re- sultant relationship between... SST gradient and rainfall (Section 3). Sensitivity of the results to the definitions is discussed in Section 4, followed by a discussion (Section 5) and the conclusions (Section 6). 2 Data and definitions The data we used are listed in Table 1; all...

  14. Tensile Adhesion Strength of Biomass Ash Deposits: Effect of the Temperature Gradient and Ash Chemistry

    DEFF Research Database (Denmark)

    Laxminarayan, Yashasvi; Nair, Akhilesh Balachandran; Jensen, Peter Arendt

    2018-01-01

    Replacing coal with biomass in power plants is a viable option for reducing net CO2 emissions and combating climate change. However, biomass combustion in boilers may exacerbate problems related to ash deposition and corrosion, demanding effective deposit removal. The tensile adhesion strength...... the deposits. After sintering, the deposits were removed using an electrically controlled arm and the corresponding tensile adhesion strength was measured.The influence of the flue gas temperature (500–700 °C), steel surface temperature (500–650 °C), and deposit composition were investigated. The results...... revealed that increasing the flue gas temperature as well as the steel surface temperature led to a sharp increase in the tensile adhesion strength of the model deposits. The sharp increase was typically observed near the melting temperature (or deformation temperature) of the investigated model deposits...

  15. Responses of Microbial Community Composition to Temperature Gradient and Carbon Steel Corrosion in Production Water of Petroleum Reservoir

    Directory of Open Access Journals (Sweden)

    Xiao-Xiao Li

    2017-12-01

    Full Text Available Oil reservoir production systems are usually associated with a temperature gradient and oil production facilities frequently suffer from pipeline corrosion failures. Both bacteria and archaea potentially contribute to biocorrosion of the oil production equipment. Here the response of microbial populations from the petroleum reservoir to temperature gradient and corrosion of carbon steel coupons were investigated under laboratory condition. Carbon steel coupons were exposed to production water from a depth of 1809 m of Jiangsu petroleum reservoir (China and incubated for periods of 160 and 300 days. The incubation temperatures were set at 37, 55, and 65°C to monitoring mesophilic, thermophilic and hyperthermophilic microorganisms associated with anaerobic carbon steel corrosion. The results showed that corrosion rate at 55°C (0.162 ± 0.013 mm year-1 and 37°C (0.138 ± 0.008 mm year-1 were higher than that at 65°C (0.105 ± 0.007 mm year-1, and a dense biofilm was observed on the surface of coupons under all biotic incubations. The microbial community analysis suggests a high frequency of bacterial taxa associated with families Porphyromonadaceae, Enterobacteriaceae, and Spirochaetaceae at all three temperatures. While the majority of known sulfate-reducing bacteria, in particular Desulfotignum, Desulfobulbus and Desulfovibrio spp., were predominantly observed at 37°C; Desulfotomaculum spp., Thermotoga spp. and Thermanaeromonas spp. as well as archaeal members closely related to Thermococcus and Archaeoglobus spp. were substantially enriched at 65°C. Hydrogenotrophic methanogens of the family Methanobacteriaceae were dominant at both 37 and 55°C; acetoclastic Methanosaeta spp. and methyltrophic Methanolobus spp. were enriched at 37°C. These observations show that temperature changes significantly alter the microbial community structure in production fluids and also affected the biocorrosion of carbon steel under anaerobic conditions.

  16. Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments.

    Science.gov (United States)

    Wang, Jing; Zhang, Zhengfeng; Zhao, Weijing; Wang, Liying; Yang, Jun

    2016-05-09

    The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using (1) H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical (1) H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l(-1) of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of (1) H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  17. Extracting and Analyzing the Warming Trend in Global and Hemispheric Temperatures

    NARCIS (Netherlands)

    Estrada, Francisco; Perron, Pierre

    2017-01-01

    This article offers an updated and extended attribution analysis based on recently published versions of temperature and forcing datasets. It shows that both temperature and radiative forcing variables can be best represented as trend stationary processes with structural changes occurring in the

  18. Analyzing of chromaticity temperature of novel bulb composed of PDMS and phosphor

    Science.gov (United States)

    Novak, M.; Fajkus, M.; Jargus, J.; Bednarek, L.; Cubik, J.; Cvejn, D.; Vasinek, V.

    2017-10-01

    The authors of this article focused on the issue of measurement of the chromaticity temperature of proposed bulbs made from polydimethylsiloxane, depending on the temperature of proposed bulbs. The advantage of this solution is the immunity to electromagnetic interference (EMI) and the ability to use, for example in dangerous environments (such as mines, factories, etc.). For the realization of incandescent bulbs was used transparent two-component elastomer Sylgard 184. A mixture of polydimethylsiloxane (PDMS) and a curing agent in a defined ratio (10:1) and admixture with garnet phosphor YAG: Ce was cured in the temperature box at temperature 90°C +/- 3°C in the shape of the bulbs. All experiments were realized with eight different weight ratios of phosphor and Sylgard 184. Optical power (5 W) from a laser with a wavelength of 455 nm was fed to the proposed bulbs using the cylindrical waveguide of polydimethylsiloxane with a diameter of 5 mm. Chromaticity temperature was measured by two temperature sensors for 12h. The outcome of this study is the evaluation of the chromaticity temperature of output light depending on temperature variations of proposed bulbs due to the conversion of optical power into heat.

  19. Crossed, Small-Deflection Energy Analyzer for Wind/Temperature Spectrometer

    Science.gov (United States)

    Herrero, Federico A.; Finne, Theodore T.

    2010-01-01

    Determination of neutral winds and ion drifts in low-Earth-orbit missions requires measurements of the angular and energy distributions of the flux of neutrals and ions entering the satellite from the ram direction. The magnitude and direction of the neutral-wind (or ion-drift) determine the location of the maximum in the angular distribution of the flux. Knowledge of the angle of maximum flux with respect to satellite coordinates (pointing) is essential to determine the wind (or ion-drift) vector. The crossed Small-Deflection Energy Analyzer (SDEA) spectrometer (see Figure 1) occupies minimal volume and consumes minimal power. Designed for upper atmosphere/ionosphere investigations at Earth altitudes above 100 km, the spectrometer operates by detecting the angular and energy distributions of neutral atoms/molecules and ions in two mutually perpendicular planes. In this configuration, the two detection planes actually cross at the spectrometer center. It is possible to merge two SDEAs so they share a common optical axis and alternate measurements between two perpendicular planes, and reduce the number of ion sources from two to one. This minimizes the volume and footprint significantly and reduces the ion source power by a factor of two. The area of the entrance aperture affects the number of ions detected/second and also determines the energy resolution. Thermionic emitters require heater power of about 100 mW to produce 1 mA of electron beam current. Typically, electron energy is about 100 eV and requires a 100-V supply for electron acceleration to supply an additional 100 mW of power. Thus, ion source power is at most 200 mW. If two ion sources were to be used, the ion source power would be, at most, 400 mW. Detector power, deflection voltage power, and microcontroller and other functions require less than 150 mW. A WTS (wind/ temperature spectrometer) with two separate optical axes would consume about 650 mW, while the crossed SDEA described here consumes about

  20. Numerical simulation of bubble behavior in subcooled flow boiling under velocity and temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Bahreini, Mohammad, E-mail: m.bahreini1990@gmail.com; Ramiar, Abas, E-mail: aramiar@nit.ac.ir; Ranjbar, Ali Akbar, E-mail: ranjbar@nit.ac.ir

    2015-11-15

    Highlights: • Condensing bubble is numerically investigated using VOF model in OpenFOAM package. • Bubble mass reduces as it goes through condensation and achieves higher velocities. • At a certain time the slope of changing bubble diameter with time, varies suddenly. • Larger bubbles experience more lateral migration to higher velocity regions. • Bubbles migrate back to a lower velocity region for higher liquid subcooling rates. - Abstract: In this paper, numerical simulation of the bubble condensation in the subcooled boiling flow is performed. The interface between two-phase is tracked via the volume of fluid (VOF) method with continuous surface force (CSF) model, implemented in the open source OpenFOAM CFD package. In order to simulate the condensing bubble with the OpenFOAM code, the original energy equation and mass transfer model for phase change have been modified and a new solver is developed. The Newtonian flow is solved using the finite volume scheme based on the pressure implicit with splitting of operators (PISO) algorithm. Comparison of the simulation results with previous experimental data revealed that the model predicted well the behavior of the actual condensing bubble. The bubble lifetime is almost proportional to bubble initial size and is prolonged by increasing the system pressure. In addition, the initial bubble size, subcooling of liquid and velocity gradient play an important role in the bubble deformation behavior. Velocity gradient makes the bubble move to the higher velocity region and the subcooling rate makes it to move back to the lower velocity region.

  1. Layout-Driven Post-Placement Techniques for Temperature Reduction and Thermal Gradient Minimization

    DEFF Research Database (Denmark)

    Liu, Wei; Calimera, Andrea; Macii, Alberto

    2013-01-01

    With the continuing scaling of CMOS technology, on-chip temperature and thermal-induced variations have become a major design concern. To effectively limit the high temperature in a chip equipped with a cost-effective cooling system, thermal specific approaches, besides low power techniques...

  2. Firsthand in situ observation of active fine laser tuning by combining a temperature gradient and a CLC wedge cell structure.

    Science.gov (United States)

    Jeong, Mi-Yun; Cha, Jihun

    2015-08-10

    In situ direct observation of the lasing process in a cholesteric liquid crystal (CLC) laser array using a CMOS camera was used to investigate discontinuous laser tuning in a parallel CLC cell. In accordance with the discontinuous pitch change by thermal energy transfer, at the same time the laser wavelength undergoes an immediate and discontinuous shift. And we found out the reason why the CLC phase has domain textures. And this work develops a simple active tunable laser array by forming a spatial temperature gradient along a wedge CLC cell. With this new strategy, only just about 7 nm laser tuning range at room temperature is extremely widened over the 105 nm wavelength range with about 0.2 nm tuning resolution. Furthermore, there is no aging effect because the employed CLC array has only one chiral molecular concentration. This strategy could be used in a practical CLC laser device application.

  3. Insect temperature-body size trends common to laboratory, latitudinal and seasonal gradients are not found across altitudes

    DEFF Research Database (Denmark)

    Horne, Curtis R.; Hirst, Andrew G.; Atkinson, David

    2018-01-01

    altitude. Although the general direction of body size clines along altitudinal gradients has been examined previously, to our knowledge altitude-body size (A-S) clines have never been synthesised quantitatively, nor compared with temperature-size (T-S) responses measured under controlled laboratory...... conditions. Here we quantitatively examine variation in intraspecific A-S clines among 121 insect species from 50 different global locations, representing 12 taxonomic orders. While some taxa were better represented in the literature than others, our analysis reveals extensive variation in the magnitude...... and direction of A-S clines. Following the assumption that temperature on average declines by 1°C per 150 m increase in altitude, order-specific A-S clines in the field appear to deviate from laboratory T-S responses. Specifically, the magnitude of A-S clines and T-S responses are more closely matched in some...

  4. Preparation of Ultrahigh Potential Gradient of ZnO Varistors by Rare-Earth Doping and Low-Temperature Sintering

    Directory of Open Access Journals (Sweden)

    Lei Ke

    2013-01-01

    Full Text Available The effects of rare-earth doping and low-temperature sintering on electrical properties of ZnO varistors were investigated. The potential gradient (E1mA of the ZnO varistors increased significantly to 2247.2 V/mm after doping 0.08 mol% of Y2O3 and sintering at 800°C for 2 h. The notable decrease of the grain size with the given experimental conditions was the origin for the increase in E1mA. During the process of high-temperature sintering, both the oxygen at the grain boundary interface and the neutralisation of the ions on the depletion layer were directly reduced, which caused the weight loss and the internal derangement of double Schottky barriers.

  5. Effects of charge non-neutrality and finite beta on the electron temperature gradient modes in Tokamaks

    Science.gov (United States)

    Hirose, A.; Liu, D. Z.; Livingstone, S.

    2004-03-01

    Local kinetic analysis of the electron temperature gradient (ETG) mode in Tokamaks indicates that the effects of charge non-neutrality are significant in the parameter regime of Tokamaks. The maximum growth rate occurs at (k/k(De))(2) 0.5 when the electron temperature and density are varied over a wide range. The growth rate becomes dependent on the beta factor even though the ETG mode is predominantly electrostatic. Finite beta stabilization of the ETG mode requires a large ballooning parameter so as to cause an effective drift reversal. Mixing length estimate yields an electron thermal diffusivity chi(e) qnu(Te) (c/omega(pe))(2) rootbeta(e) / L-n where c/omega(pe) is the electron skin depth.

  6. Latitudinal gradients in growth and spawning of sea bass, Dicentrarchus labrax, and their relationship with temperature and photoperiod

    Science.gov (United States)

    Vinagre, C.; Ferreira, T.; Matos, L.; Costa, M. J.; Cabral, H. N.

    2009-02-01

    0-group Sea bass, Dicentrarchus labrax, were captured in four estuarine nursery areas along the Portuguese coast, during the spring and summer of 2005. This coast has a North-South orientation which means that it is particularly suited for the investigation of latitudinal trends. Growth and hatch dates were estimated through otolith daily increment analysis. A clear latitudinal gradient in growth rates was detected. D. labrax mean growth rates were 0.48 mm d -1, 0.51 mm d -1, 0.56 mm d -1 and 0.61 mm d -1, from the Ria de Aveiro, the Mondego estuary, the Tagus estuary and the Mira estuary, respectively. A latitudinal gradient also existed in the spawning season of this species, particularly concerning its onset, which occurred earlier in the South. Analysis of sea surface temperature data from the adjacent coastal waters showed that spawning is not triggered by an increase in temperature, as has been argued in other coastal areas at higher latitudes. Photoperiod played a crucial role in the determination of spawning season at the Portuguese coast latitudinal range. The impact of future climate change on the observed patterns is also discussed.

  7. Development and evaluation of a workpiece temperature analyzer for industrial furnaces

    Energy Technology Data Exchange (ETDEWEB)

    Berthod, J.W.

    1993-06-01

    Tests were done to determine whether ultrasound could be generated, propagated through, and detected in typical steel specimens up to approximately 1020{degree}C. All specimens were subjected to room temperature tests by generating ultrasound via a 1.0 Joule Nd-YAG laser. Two specimens were also tested up to the higher temperature. Ultrasound detection was also performed with the Fabry-Perot interferometer. The tests and results are described. Test plans are presented.

  8. Experimental study of thermo-mechanical behavior of SiC composite tubing under high temperature gradient using solid surrogate

    Energy Technology Data Exchange (ETDEWEB)

    Alva, Luis; Shapovalov, Kirill [University of South Carolina, Mechanical Engineering Department (United States); Jacobsen, George M.; Back, Christina A. [General Atomics (United States); Huang, Xinyu, E-mail: huangxin@mailbox.sc.edu [University of South Carolina, Mechanical Engineering Department (United States)

    2015-11-15

    Nuclear grade silicon carbide fiber (SiC{sub f}) reinforced silicon carbide matrix (SiC{sub m}) composite is a promising candidate material for accident tolerance fuel (ATF) cladding. A major challenge is ensuring the mechanical robustness of the ceramic cladding under accident conditions. In this work the high temperature mechanical response of a SiC{sub f}–SiC{sub m} composite tubing is studied using a novel thermo-mechanical test method. A solid surrogate tube is placed within and bonded to the SiC{sub f}–SiC{sub m} sample tube using a ceramic adhesive. The bonded tube pair is heated from the center using a ceramic glower. During testing, the outer surface temperature of the SiC sample tube rises up to 1274 K, and a steep temperature gradient develops through the thickness of the tube pair. Due to CTE mismatch and the temperature gradient, the solid surrogate tube induces high tensile stress in the SiC sample. During testing, 3D digital image correlation (DIC) method is used to map the strains on the outer surface of the SiC-composite, and acoustic emissions (AE) are monitored to detect the onset and progress of material damage. The thermo-mechanical behavior of SiC-composite sample is compared with that of monolithic SiC samples. Finite element models are developed to estimate stress–strain distribution within the tube assembly. Model predicted surface strain matches the measured surface strain using the DIC method. AE activities indicated a progressive damage process for SiC{sub f}–SiC{sub m} composite samples. For the composites tested in this study, the threshold mechanical hoop strain for matrix micro-cracking to initiate in SiC{sub f}–SiC{sub m} sample is found to be ∼300 microstrain.

  9. Comparison of bacterial community changes in fermenting kimchi at two different temperatures using a denaturing gradient gel electrophoresis analysis.

    Science.gov (United States)

    Hong, Yeun; Yang, Hee-Seok; Chang, Hae-Choon; Kim, Hae-Yeong

    2013-01-01

    A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique followed by sequencing of the 16S rDNA fragments eluted from the bands of interest on denaturing gradient gels was used to monitor changes in the bacterial microflora of two commercial kimchi, salted cabbage, and ingredient mix samples during 30 days of fermentation at 4°C and 10°C. Leuconostoc (Lc.) was the dominant lactic acid bacteria (LAB) over Lactobacillus (Lb.) species at 4°C. Weissella confusa was detected in the ingredient mix and also in kimchi samples throughout fermentation in both samples at 4°C and 10°C. Lc. gelidum was detected as the dominant LAB at 4°C in both samples. The temperature affected the LAB profile of kimchi by varing the pH, which was primarily caused by the temperature-dependent competition among different LAB species in kimchi. At 4°C, the sample variations in pH and titratable acidity were more conspicuous owing to the delayed growth of LAB. Temperature affected only initial decreases in pH and initial increases in viable cell counts, but affected both the initial increases and final values of titratable acidity. The initial microflora in the kimchi sample was probably determined by the microflora of the ingredient mix, not by that of the salted cabbage. The microbial distributions in the samples used in this study resembled across the different kimchi samples and the different fermentation temperatures as the numbers of LAB increased and titratable acidity decreased.

  10. Reproductive efficiency of a Mediterranean endemic zooxanthellate coral decreases with increasing temperature along a wide latitudinal gradient.

    Directory of Open Access Journals (Sweden)

    Valentina Airi

    Full Text Available Investments at the organismal level towards reproduction and growth are often used as indicators of health. Understanding how such energy allocation varies with environmental conditions may, therefore, aid in predicting possible responses to global climatic change in the near future. For example, variations in seawater temperature may alter the physiological functioning, behavior, reproductive output and demographic traits (e.g., productivity of marine organisms, leading to shifts in the structure, spatial range, and abundance of populations. This study investigated variations in reproductive output associated with local seawater temperature along a wide latitudinal gradient on the western Italian coast, in the zooxanthellate Mediterranean coral, Balanophyllia europaea. Reproductive potential varied significantly among sites, where B. europaea individuals from the warmest site experienced loss of oocytes during gametogenesis. Most of the early oocytes from warmest sites did not reach maturity, possibly due to inhibition of metabolic processes at high temperatures, causing B. europaea to reabsorb the oocytes and utilize them as energy for other vital functions. In a progressively warming Mediterranean, the efficiency of the energy invested in reproduction could be considerably reduced in this species, thereby affecting vital processes. Given the projected increase in seawater temperature as a consequence of global climate change, the present study adds evidence to the threats posed by high temperatures to the survival of B. europaea in the next decades.

  11. Climate change and the Madden-Julian Oscillation: A vertically resolved weak temperature gradient analysis

    Science.gov (United States)

    Wolding, Brandon O.; Maloney, Eric D.; Henderson, Stephanie; Branson, Mark

    2017-03-01

    WTG balance is used to examine how changes in the moist thermodynamic structure of the tropics affect the MJO in two simulations of the Superparameterized Community Earth System Model (SP-CESM), one at preindustrial (PI) levels of CO2 and one where CO2 levels have been quadrupled (4×CO2). While MJO convective variability increases considerably in the 4×CO2 simulation, the dynamical response to this convective variability decreases. Increased MJO convective variability is shown to be a robust response to the steepening vertical moisture gradient, consistent with the findings of previous studies. The steepened vertical moisture gradient allows MJO convective heating to drive stronger variations in large-scale vertical moisture advection, supporting destabilization of the MJO. The decreased dynamical response to MJO convective variability is shown to be a consequence of increased static stability, which allows weaker variations in large-scale vertical velocity to produce sufficient adiabatic cooling to balance variations in MJO convective heating. This weakened dynamical response results in a considerable reduction of the MJO's ability to influence the extratropics, which is closely tied to the strength of its associated divergence. A composite lifecycle of the MJO was used to show that northern hemisphere extratropical 525 hPa geopotential height anomalies decreased by 27% in the 4×CO2 simulation, despite a 22% increase in tropical convective heating associated with the MJO. Results of this study suggest that while MJO convective variability may increase in a warming climate, the MJO's role in "bridging weather and climate" in the extratropics may not.

  12. Using basic metrics to analyze high-resolution temperature data in the subsurface

    Science.gov (United States)

    Shanafield, Margaret; McCallum, James L.; Cook, Peter G.; Noorduijn, Saskia

    2017-08-01

    Time-series temperature data can be summarized to provide valuable information on spatial variation in subsurface flow, using simple metrics. Such computationally light analysis is often discounted in favor of more complex models. However, this study demonstrates the merits of summarizing high-resolution temperature data, obtained from a fiber optic cable installation at several depths within a water delivery channel, into daily amplitudes and mean temperatures. These results are compared to fluid flux estimates from a one-dimensional (1D) advection-conduction model and to the results of a previous study that used a full three-dimensional (3D) model. At a depth of 0.1 m below the channel, plots of amplitude suggested areas of advective water movement (as confirmed by the 1D and 3D models). Due to lack of diurnal signal at depths below 0.1 m, mean temperature was better able to identify probable areas of water movement at depths of 0.25-0.5 m below the channel. The high density of measurements provided a 3D picture of temperature change over time within the study reach, and would be suitable for long-term monitoring in man-made environments such as constructed wetlands, recharge basins, and water-delivery channels, where a firm understanding of spatial and temporal variation in infiltration is imperative for optimal functioning.

  13. Spatial and temporal variations in atmospheric temperature and humidity gradients controlled by local urban land use intensity in Boston, MA

    Science.gov (United States)

    Wang, J.; Hutyra, L.; Li, D.; Friedl, M. A.

    2016-12-01

    Cities are home to the majority of humanity. Thus, understanding the mechanisms that control urban climates has substantial societal importance to a variety of sectors, including public health and energy management. While it is widely known that the surface climate of cities is modified by urban land use, relatively few studies have examined how spatial variability in urban land use intensity controls spatio-temporal variation in urban microclimates. We used data from an urban sensor network (n=25) and medium resolution remote sensing to explore the nature and magnitude of urban air temperature (Ta) and vapor pressure deficit (VPD) dependence on local land use and land cover on both diurnal and seasonal time scales in the Boston metropolitan area. We observed positive correlations between the amount of local impervious surface area (ISA) and Ta as well as strong positive correlations between local ISA and VPD. Dependence on local urbanization intensity peaked at night during the growing season, when urban Ta and VPD increased by up to 0.03 C and 0.008 kPa, respectively, for every 1% increase in ISA. In the daytime during the growing season, corresponding maximum gradients were 0.015 C and 0.006 kPa per for every 1% increase in ISA. Air temperatures and VPDs are coupled to each other, and their relationship exhibits significant diurnal hysteresis during the growing season with changes in VPD gradients generally preceding changes in Ta gradients. By removing the effect of changes in temperature on VPD, we show that 79% of the urban-rural difference in VPD was explained by differences in near surface atmospheric water content, which we attribute to lower rates of evapotranspiration arising from higher ISA, lower canopy cover, and lower leaf area in Boston relative to nearby rural areas. Combining medium resolution remote sensing data and ground measurements, we estimate spatially-explicit maps of net Ta and VPD enhancement resulting from Boston's spatially

  14. Foliar Temperature Gradients as Drivers of Budburst in Douglas-fir: New Applications of Thermal Infrared Imagery

    Science.gov (United States)

    Miller, R.; Lintz, H. E.; Thomas, C. K.; Salino-Hugg, M. J.; Niemeier, J. J.; Kruger, A.

    2014-12-01

    Budburst, the initiation of annual growth in plants, is sensitive to climate and is used to monitor physiological responses to climate change. Accurately forecasting budburst response to these changes demands an understanding of the drivers of budburst. Current research and predictive models focus on population or landscape-level drivers, yet fundamental questions regarding drivers of budburst diversity within an individual tree remain unanswered. We hypothesize that foliar temperature, an important physiological property, may be a dominant driver of differences in the timing of budburst within a single tree. Studying these differences facilitates development of high throughput phenotyping technology used to improve predictive budburst models. We present spatial and temporal variation in foliar temperature as a function of physical drivers culminating in a single-tree budburst model based on foliar temperature. We use a novel remote sensing approach, combined with on-site meteorological measurements, to demonstrate important intra-canopy differences between air and foliar temperature. We mounted a thermal infrared camera within an old-growth canopy at the H.J. Andrews LTER forest and imaged an 8m by 10.6m section of a Douglas-fir crown. Sampling one image per minute, approximately 30,000 thermal infrared images were collected over a one-month period to approximate foliar temperature before, during and after budburst. Using time-lapse photography in the visible spectrum, we documented budburst at fifteen-minute intervals with eight cameras stratified across the thermal infrared camera's field of view. Within the imaged tree's crown, we installed a pyranometer, 2D sonic anemometer and fan-aspirated thermohygrometer and collected 3,000 measurements of net shortwave radiation, wind speed, air temperature and relative humidity. We documented a difference of several days in the timing of budburst across both vertical and horizontal gradients. We also observed clear

  15. Larval connectivity across temperature gradients and its potential effect on heat tolerance in coral populations.

    Science.gov (United States)

    Kleypas, Joan A; Thompson, Diane M; Castruccio, Frederic S; Curchitser, Enrique N; Pinsky, Malin; Watson, James R

    2016-11-01

    Coral reefs are increasingly exposed to elevated temperatures that can cause coral bleaching and high levels of mortality of corals and associated organisms. The temperature threshold for coral bleaching depends on the acclimation and adaptation of corals to the local maximum temperature regime. However, because of larval dispersal, coral populations can receive larvae from corals that are adapted to very different temperature regimes. We combine an offline particle tracking routine with output from a high-resolution physical oceanographic model to investigate whether connectivity of coral larvae between reefs of different thermal regimes could alter the thermal stress threshold of corals. Our results suggest that larval transport between reefs of widely varying temperatures is likely in the Coral Triangle and that accounting for this connectivity may be important in bleaching predictions. This has important implications in conservation planning, because connectivity may allow some reefs to have an inherited heat tolerance that is higher or lower than predicted based on local conditions alone. © 2016 John Wiley & Sons Ltd.

  16. Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

    Science.gov (United States)

    Rashidnia, N.; Balasubramaniam, R.

    1991-01-01

    An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

  17. A Model for Analyzing Temperature Profiles in Pipe Walls and Fluids Using Mathematical Experimentation

    Directory of Open Access Journals (Sweden)

    Moses E. Emetere

    2014-09-01

    Full Text Available Temperature profiling in both fluid and pipe walls had not been explained theoretically. The equations of energy balance and heat conductivity were queried by introducing known parameters to solveheat transfer using virtual mathematical experimentation. This was achieved by remodelingPoiseuille's equation. Distribution of temperature profiles between pipe wall, fluid flow, and surrounding air was investigated and validated upon comparison with experimental results. A new dimensionless parameter (unified number (U was introduced with the aim of solving known errors of the Reynolds and Nusselts number.

  18. Environmental temperature affects prevalence of blood parasites of birds on an elevation gradient: implications for disease in a warming climate.

    Directory of Open Access Journals (Sweden)

    Itzel Zamora-Vilchis

    Full Text Available BACKGROUND: The rising global temperature is predicted to expand the distribution of vector-borne diseases both in latitude and altitude. Many host communities could be affected by increased prevalence of disease, heightening the risk of extinction for many already threatened species. To understand how host communities could be affected by changing parasite distributions, we need information on the distribution of parasites in relation to variables like temperature and rainfall that are predicted to be affected by climate change. METHODOLOGY/PRINCIPAL FINDINGS: We determined relations between prevalence of blood parasites, temperature, and seasonal rainfall in a bird community of the Australian Wet Tropics along an elevation gradient. We used PCR screening to investigate the prevalence and lineage diversity of four genera of blood parasites (Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma in 403 birds. The overall prevalence of the four genera of blood parasites was 32.3%, with Haemoproteus the predominant genus. A total of 48 unique lineages were detected. Independent of elevation, parasite prevalence was positively and strongly associated with annual temperature. Parasite prevalence was elevated during the dry season. CONCLUSIONS/SIGNIFICANCE: Low temperatures of the higher elevations can help to reduce both the development of avian haematozoa and the abundance of parasite vectors, and hence parasite prevalence. In contrast, high temperatures of the lowland areas provide an excellent environment for the development and transmission of haematozoa. We showed that rising temperatures are likely to lead to increased prevalence of parasites in birds, and may force shifts of bird distribution to higher elevations. We found that upland tropical areas are currently a low-disease habitat and their conservation should be given high priority in management plans under climate change.

  19. Microbial habitat connectivity across spatial scales and hydrothermal temperature gradients at Guaymas Basin

    Directory of Open Access Journals (Sweden)

    Stefanie eMeyer

    2013-07-01

    Full Text Available The Guaymas Basin (Gulf of California hydrothermal vent area is known as a dynamic and hydrothermally vented sedimentary system, where the advection and production of a variety of different metabolic substrates support a high microbial diversity and activity in the seafloor. The main objective of our study was to explore the role of temperature and other environmental factors on community diversity, such as the presence of microbial mats and seafloor bathymetry within one hydrothermally vented field of 200 × 250 m dimension. In this field, temperature increased strongly with sediment depth reaching the known limit to life within a few decimeters. Potential sulfate reduction rate as a key community activity parameter was strongly affected by in situ temperature and sediment depth, declining from high rates of 1-5 μmol ml-1 d-1 at the surface to the detection limit below 5 cm sediment depth, despite the presence of sulfate and hydrocarbons. Automated Ribosomal Intergenic Spacer Analysis yielded a high-resolution fingerprint of the dominant members of the bacterial community. Our analyses showed strong temperature and sediment depth effects on bacterial cell abundance and Operational Taxonomic Units (OTUs number, both declining by more than one order of magnitude below the top 5 cm of the sediment surface. Another fraction of the variation in diversity and community structure was explained by differences in the local bathymetry and spatial position within the vent field. Nevertheless, more than 80% of all detected OTUs were shared among the different temperature realms and sediment depths, after being classified as cold (T<10°C, medium (10°C≤T<40°C or hot (T≥40°C temperature conditions, with significant OTU overlap with the richer surface communities. Overall, this indicates a high connectivity of benthic bacterial habitats in this dynamic and heterogeneous marine ecosystem influenced by strong hydrothermalism.

  20. Change in Water-Holding Capacity in Mushroom with Temperature Analyzed by Flory-Rehner Theory

    NARCIS (Netherlands)

    Paudel, Ekaraj; Boom, R.M.; Sman, van der R.G.M.

    2015-01-01

    The change in water-holding capacity of mushroom with the temperature was interpreted using the Flory-Rehner theory for swelling of polymeric networks, extended with the Debye-Hückel theory for electrolytic interactions. The validity of these theories has been verified with independent sorption

  1. A temperature gradient may support mother-infant thermal identification and communication in the breast crawl from birth to breastfeeding.

    Science.gov (United States)

    Zanardo, Vincenzo; Volpe, Francesca; de Luca, Federico; Straface, Gianluca

    2017-10-01

    The human female's nipple-areolar complex (NAC) is the point of arrival of a natural progression from birth to breastfeeding, linked to functional, chemical and biophysical cues that promote the breast crawl soon after birth. We investigated the thermal gradient generated by the lips of the neonate and warmth of the NAC, which may drive the infant directly to the nipple. We prospectively studied 41 full-term singleton infants and their mothers at the Policlinico Abano Terme, Italy, between January 1, 2015, and February 28, 2015. NAC and breast quadrant temperatures were assessed 6 ± 2 hours prepartum and one and two days postpartum, together with the neonates' lip temperature. The temperature of the neonates' lips was significantly lower than the forehead temperature on days one and two postpartum (delta = -1.24°C, p breast crawl and in the natural progression of the continuum from birth to breastfeeding. ©2017 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  2. Heterotrophic respiration in drained tropical peat temperatures influenced by shading gradient

    Science.gov (United States)

    Jauhiainen, Jyrki; Kerojoki, Otto; Silvennoinen, Hanna; Limin, Suwido; Vasander, Harri

    2015-04-01

    Lowland peatlands in Southeast Asia constitute a highly concentrated carbon (C) pool of global significance. These peatlands have formed over periods of several millennia by forest vegetation tolerant to flooding and poor substrates. Uncontrollable drainage and reoccurring wild fires in lack of management after removal of forest cover has impaired the C-storing functions in large reclaimed areas. Intergovernmental Panel on Climate Change (IPCC) reporting sees drained tropical organic soils as one of the largest greenhouse gas emissions releasing terrestrial systems. Vast areas of deforested tropical peatlands do not receive noteworthy shading by vegetation, which increases the amount of solar radiation reaching the peat surface. We studied heterotrophic carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes in tropical peat in conditions, where; (i) peat temperatures were modified by artificial shading (no shade, 28%, 51% and 90% from the full sun exposure), (ii) root respiration was minimized, (iii) nutrient availability for peat decomposer community was changed (NPK fertilization of 0 and 313 kg ha-1). The experiment was repeated at two over 20 years ago drained fallow agricultural- and degraded sites in Central Kalimantan, Indonesia. Enhanced shading created a lasting decrease in peat temperatures, and decreased diurnal temperature fluctuations, in comparison to less shaded plots. The largest peat temperature difference was between the unshaded and 90% shaded peat surface, where the average temperatures within the topmost 50-cm peat profile differed 3 °C, and diurnal temperatures at 5 cm depth varied up to 4.2 °C in the unshaded and 0.4 °C in the 90% shaded conditions. Highest impacts on the heterotrophic CO2 fluxes caused by the treatments were on agricultural land, where 90% shading from the full exposure resulted in a 33% lower CO2 emission average on the unfertilised plots and a 66% lower emission average on the fertilised plots. Correlation

  3. Ammonia oxidizer populations vary with nitrogen cycling across a tropical montane mean annual temperature gradient

    Science.gov (United States)

    S. Pierre; I. Hewson; J. P. Sparks; C. M. Litton; C. Giardina; P. M. Groffman; T. J. Fahey

    2017-01-01

    Functional gene approaches have been used to better understand the roles of microbes in driving forest soil nitrogen (N) cycling rates and bioavailability. Ammonia oxidation is a rate limiting step in nitrification, and is a key area for understanding environmental constraints on N availability in forests. We studied how increasing temperature affects the role of...

  4. Phytoplankton biomass, composition and productivity along a temperature and stratification gradient in the Northeast Atlantic Ocean.

    NARCIS (Netherlands)

    van de Poll, W.; Kulk, G.; Timmermans, K.R.; Brussaard, C.P.D.; van der Woerd, H.J.; Kehoe, M.J.; Mojica, K.D.A.; Visser, R.J.W.; Buma, A.G.J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 N in the northeast Atlantic

  5. Microbial habitat connectivity across spatial scales and hydrothermal temperature gradients at Guaymas Basin.

    Science.gov (United States)

    Meyer, Stefanie; Wegener, Gunter; Lloyd, Karen G; Teske, Andreas; Boetius, Antje; Ramette, Alban

    2013-01-01

    The Guaymas Basin (Gulf of California) hydrothermal vent area is known as a dynamic and hydrothermally vented sedimentary system, where the advection and production of a variety of different metabolic substrates support a high microbial diversity and activity in the seafloor. The main objective of our study was to explore the role of temperature and other environmental factors on community diversity, such as the presence of microbial mats and seafloor bathymetry within one hydrothermally vented field of 200 × 250 m dimension. In this field, temperature increased strongly with sediment depth reaching the known limit of life within a few decimeters. Potential sulfate reduction rate as a key community activity parameter was strongly affected by in situ temperature and sediment depth, declining from high rates of 1-5 μmol ml(-1) d(-1) at the surface to the detection limit below 5 cm sediment depth, despite the presence of sulfate and hydrocarbons. Automated Ribosomal Intergenic Spacer Analysis yielded a high-resolution fingerprint of the dominant members of the bacterial community. Our analyses showed strong temperature and sediment depth effects on bacterial cell abundance and Operational Taxonomic Units (OTUs) number, both declining by more than one order of magnitude below the top 5 cm of the sediment surface. Another fraction of the variation in diversity and community structure was explained by differences in the local bathymetry and spatial position within the vent field. Nevertheless, more than 80% of all detected OTUs were shared among the different temperature realms and sediment depths, after being classified as cold (T bacterial habitats in this dynamic and heterogeneous marine ecosystem influenced by strong hydrothermalism.

  6. Precipitation and air temperature control the variations of dissolved organic matter along an altitudinal forest gradient, Gongga Mountains, China.

    Science.gov (United States)

    Hu, Zhaoyong; Wang, Genxu; Sun, Xiangyang

    2017-04-01

    Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contribute significantly to C and N cycling in forest ecosystems. Little information is available on the variations in the DOC and DON concentrations and depositions in bulk and stand precipitation within forests along an altitudinal gradient. To determine the temporal variations in the DOC and DON concentrations and depositions in different forests and the spatial variations along the elevation gradient, the DOC and DON concentrations and depositions were measured in bulk precipitation, throughfall, and stemflow within three forest types, i.e., broadleaf forest (BLF), broadleaf-coniferous forest (BCF), and coniferous forest (CF), during the wet season (May to October) on Gongga Mountain, China, in 2015. The concentrations of bulk precipitation in BLF, BCF, and CF were 3.92, 4.04, and 2.65 mg L(-1), respectively, for DOC and were 0.38, 0.26, and 0.29 mg L(-1), respectively, for DON. BCF had the highest DOC deposition both in bulk precipitation (45.12 kg ha(-1)) and stand precipitation (98.52 kg ha(-1)), whereas the highest DON deposition was in BLF (3.62 kg ha(-1) bulk precipitation and 4.11 kg ha(-1) stand precipitation) during the study period. The meteorological conditions of precipitation and air temperature significantly influenced the dissolved organic matter (DOM) depositions along the elevation gradient. The leaf area index did not show any correlation with DOM depositions during the growing season.

  7. Triclustering Georeferenced Time Series for Analyzing Patterns of Intra-Annual Variability in Temperature

    NARCIS (Netherlands)

    Wu, Xiaojing; Zurita-Milla, R.; Izquierdo Verdiguier, E.; Kraak, M.J.

    2017-01-01

    Clustering is often used to explore patterns in georeferenced time series (GTS). Most clustering studies, however, only analyze GTS from one or two dimension(s) and are not capable of the simultaneous analysis of the data from three dimensions: spatial, temporal, and any third (e.g., attribute)

  8. The Impact of Tree Diversity on Different Aspects of Insect Herbivory along a Global Temperature Gradient - A Meta-Analysis.

    Science.gov (United States)

    Kambach, Stephan; Kühn, Ingolf; Castagneyrol, Bastien; Bruelheide, Helge

    2016-01-01

    Forests with higher tree diversity are often assumed to be more resistant to insect herbivores but whether this effect depends on climatic conditions is so far poorly understood. In particular, a forest's resistance to herbivory may depend on mean annual temperature (MAT) as a key driver of plant and insect phenology. We carried out a global meta-analysis on regression coefficients between tree diversity and four aspects of insect herbivory, namely herbivore damage, abundance, incidence rate and species richness. To test for a potential shift of tree diversity effects along a global gradient of MAT we applied mixed-effects models and estimated grand mean effect sizes and the influence of MAT, experimental vs. observational studies and herbivores diet breadth. There was no overall effect of tree diversity on the pooled effect sizes of insect herbivore damage, abundance and incidence rate. However, when analysed separately, we found positive grand mean effect sizes for herbivore abundance and species richness. For herbivore damage and incidence rate we found a significant but opposing shift along a gradient of MAT indicating that with increasing MAT diversity effects on herbivore damage tend towards associational resistance whereas diversity effects on incidence rates tend towards associational susceptibility. Our results contradict previous meta-analyses reporting overall associational resistance to insect herbivores in mixed forests. Instead, we report that tree diversity effects on insect herbivores can follow a biogeographic pattern calling for further in-depth studies in this field.

  9. Soil nitrogen cycling and availability are linked to ammonia oxidizer abundance across a tropical mean annual temperature gradient

    Science.gov (United States)

    Pierre, S.; Litton, C. M.; Giardina, C. P.; Sparks, J. P.; Groffman, P.; Hewson, I.; Fahey, T.

    2016-12-01

    Interactions among environmental variables can obfuscate the primary drivers linking soil microbial community function to ecosystem biogeochemistry. These connections are important to understand in order to predict ecosystem responses to global climate change. In particular, the role of mean annual temperature (MAT) in regulating carbon (C) and nitrogen (N) cycling via microbial communities remains unclear. To study these dynamics in situ, we used a a natural elevation gradient of tropical wet montane forest on Mauna Kea, Hawai'i with established permanent plots. Across the gradient, environmental variables besides MAT remain constant. We studied the abundance and activity of the amoA gene, which regulates the rate-limiting step of nitrification, in ammonia oxidizing archaea (AOA) and bacteria (AOB) with relation to N availability and cycling across increasing MAT. Our results show that the abundance of amoA is positively correlated with MAT (p<0.05; r2=0.34) and that MAT and amoA abundance are the primary predictors of nitrate (NO3-) bioavailability (p<0.05). We also found that the relative expression of amoA (cDNA/DNA) is not correlated with MAT or potential net nitrification rate. Our results indicate the direct role of MAT in ammonia oxidizer community structure and demonstrate feedbacks to nutrient availability in forest systems. These findings suggest that forest primary production and carbon cycling may be affected by AOA and AOB responses to rising MAT.

  10. The Impact of Tree Diversity on Different Aspects of Insect Herbivory along a Global Temperature Gradient - A Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    Stephan Kambach

    Full Text Available Forests with higher tree diversity are often assumed to be more resistant to insect herbivores but whether this effect depends on climatic conditions is so far poorly understood. In particular, a forest's resistance to herbivory may depend on mean annual temperature (MAT as a key driver of plant and insect phenology. We carried out a global meta-analysis on regression coefficients between tree diversity and four aspects of insect herbivory, namely herbivore damage, abundance, incidence rate and species richness. To test for a potential shift of tree diversity effects along a global gradient of MAT we applied mixed-effects models and estimated grand mean effect sizes and the influence of MAT, experimental vs. observational studies and herbivores diet breadth. There was no overall effect of tree diversity on the pooled effect sizes of insect herbivore damage, abundance and incidence rate. However, when analysed separately, we found positive grand mean effect sizes for herbivore abundance and species richness. For herbivore damage and incidence rate we found a significant but opposing shift along a gradient of MAT indicating that with increasing MAT diversity effects on herbivore damage tend towards associational resistance whereas diversity effects on incidence rates tend towards associational susceptibility. Our results contradict previous meta-analyses reporting overall associational resistance to insect herbivores in mixed forests. Instead, we report that tree diversity effects on insect herbivores can follow a biogeographic pattern calling for further in-depth studies in this field.

  11. Field and Temperature Gradients from Short Conductors in a Dissipative Medium

    Directory of Open Access Journals (Sweden)

    Quirino Balzano

    2007-01-01

    Full Text Available This paper considers the specific absorption rate (SAR in tissue of radiofrequency (RF energy and temperature increases produced by RF currents on short conductors (0.03–0.1λ. We consider a cylindrical model in which a center-feeds, insulated antenna is embedded in tissue. We introduce a new method for the analytic evaluation of the fields in the cylindrical phantom taking advantage of the axial symmetry of the antenna and the tissue. Results of the analytical model are compared to results of numerical (finite difference time domain simulations; in addition, the thermal response of the exposed material is calculated by finite element solution of the heat conduction equation. For model antennas of 1 to 3 cm total length with a feedpoint current of 10mA RMS at 900MHz, the maximum SAR (in tissue next to the antenna is less than ∼2.5W/kg. SAR decays rapidly with radial distance from the antenna (∼r−4 for the 1cm antenna and creates a steady-state temperature rise less than 0.05K at the location of SARmax. Heat conduction causes the temperature to decline steeply with radius (depth into tissue.

  12. On the nature of radial transport across sheared zonal flows in electrostatic ion-temperature-gradient gyrokinetic tokamak plasma turbulencea)

    Science.gov (United States)

    Sánchez, R.; Newman, D. E.; Leboeuf, J.-N.; Carreras, B. A.; Decyk, V. K.

    2009-05-01

    It is argued that the usual understanding of the suppression of radial turbulent transport across a sheared zonal flow based on a reduction in effective transport coefficients is, by itself, incomplete. By means of toroidal gyrokinetic simulations of electrostatic, ion-temperature-gradient turbulence, it is found instead that the character of the radial transport is altered fundamentally by the presence of a sheared zonal flow, changing from diffusive to anticorrelated and subdiffusive. Furthermore, if the flows are self-consistently driven by the turbulence via the Reynolds stresses (in contrast to being induced externally), radial transport becomes non-Gaussian as well. These results warrant a reevaluation of the traditional description of radial transport across sheared flows in tokamaks via effective transport coefficients, suggesting that such description is oversimplified and poorly captures the underlying dynamics, which may in turn compromise its predictive capabilities.

  13. On the nature of radial transport across sheared zonal flows in electrostatic ion-temperature-gradient gyrokinetic tokamak turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Raul [ORNL; Newman, David E [University of Alaska; Leboeuf, Jean-Noel [JNL Scientific, Inc., Casa Grande, AZ; Carreras, Benjamin A [BACV Solutions, Inc., Oak Ridge; Decyk, Viktor [University of California, Los Angeles

    2009-01-01

    It is argued that the usual understanding of the suppression of radial turbulent transport across a sheared zonal flow based on a reduction in effective transport coefficients is, by itself, incomplete. By means of toroidal gyrokinetic simulations of electrostatic, ion-temperature-gradient turbulence, it is found instead that the character of the radial transport is altered fundamentally by the presence of a sheared zonal flow, changing from diffusive to anticorrelated and subdiffusive. Furthermore, if the flows are self-consistently driven by the turbulence via the Reynolds stresses (in contrast to being induced externally), radial transport becomes non-Gaussian as well. These results warrant a reevaluation of the traditional description of radial transport across sheared flows in tokamaks via effective transport coefficients, suggesting that such description is oversimplified and poorly captures the underlying dynamics, which may in turn compromise its predictive capabilities.

  14. Thermo-Acoustic Properties of a Burner with Axial Temperature Gradient: Theory and Experiment

    Directory of Open Access Journals (Sweden)

    Béla Kosztin

    2013-03-01

    Full Text Available This paper presents a model for thermo-acoustic effects in a gas turbine combustor. A quarter-wavelength burner with rectangular cross-section has been built and studied from an experimental and theoretical perspective. It has a premixed methane-air flame, which is held by a bluff body, and spans the width of the burner. The flame is compact, i.e. its length is much smaller than that of the burner. The fundamental mode of the burner is unstable; its frequency and pressure distribution have been measured. The complex pressure reflection coefficients at the upstream and downstream end of the burner were also measured. For the theoretical considerations, we divide the burner into three regions (the cold pre-combustion chamber, the flame region and the hot outlet region, and assume one-dimensional acoustic wave propagation in each region. The acoustic pressure and velocity are assumed continuous across the interface between the precombustion chamber and flame region, and across the interface between the flame region and outlet region. The burner ends are modelled by the measured pressure reflection coefficients. The mean temperature is assumed to have the following profile: uniformly cold and uniformly hot in the pre-combustion chamber and outlet region, respectively, and rising continuously from cold to hot in the flame region. For comparison, a discontinuous temperature profile, jumping directly from cold to hot, is also considered. The eigenfrequencies are calculated, and the pressure distribution of the fundamental mode is predicted. There is excellent agreement with the experimental results. The exact profile of the mean temperature in the flame region is found to be unimportant. This study gives us an experimentally validated Green's function, which is a very useful tool for further theoretical studies.

  15. Examination of Surface Temperature Modification by Open-Top Chambers along Moisture and Latitudinal Gradients in Arctic Alaska Using Thermal Infrared Photography

    Directory of Open Access Journals (Sweden)

    Nathan C. Healey

    2016-01-01

    Full Text Available Passive warming manipulation methodologies, such as open-top chambers (OTCs, are a meaningful approach for interpretation of impacts of climate change on the Arctic tundra biome. The magnitude of OTC warming has been studied extensively, revealing an average plot-level warming of air temperature that ranges between 1 and 3 °C as measured by shielded resistive sensors or thermocouples. Studies have also shown that the amount of OTC warming depends in part on location climate, vegetation, and soil properties. While digital infrared thermometers have been employed in a few comparisons, most of the focus of the effectiveness of OTC warming has been on air or soil temperature rather than tissue or surface temperatures, which directly translate to metabolism. Here we used thermal infrared (TIR photography to quantify tissue and surface temperatures and their spatial variability at a previously unavailable resolution (3–6 mm2. We analyzed plots at three locations that are part of the International Tundra Experiment (ITEX-Arctic Observing Network (AON-ITEX network along both moisture and latitudinal gradients spanning from the High Arctic (Barrow, AK, USA to the Low Arctic (Toolik Lake, AK, USA. Our results show a range of OTC surface warming from 2.65 to 1.27 °C (31%–10% at our three sites. The magnitude of surface warming detected by TIR imagery in this study was comparable to increases in air temperatures previously reported for these sites. However, the thermal images revealed wide ranges of surface temperatures within the OTCs, with some surfaces well above ambient unevenly distributed within the plots under sunny conditions. We note that analyzing radiometric temperature may be an alternative for future studies that examine data acquired at the same time of day from sites that are in close geographic proximity to avoid the requirement of emissivity or atmospheric correction for validation of results. We foresee future studies using TIR

  16. Thermal Investigation in the Cappadocia Region, Central Anatolia-Turkey, Analyzing Curie Point Depth, Geothermal Gradient, and Heat-Flow Maps from the Aeromagnetic Data

    Science.gov (United States)

    Bilim, Funda; Kosaroglu, Sinan; Aydemir, Attila; Buyuksarac, Aydin

    2017-12-01

    In this study, curie point depth (CPD), heat flow, geothermal gradient, and radiogenic heat production maps of the Cappadocian region in central Anatolia are presented to reveal the thermal structure from the aeromagnetic data. The large, circular pattern in these maps matches with previously determined shallow (2 km in average) depression. Estimated CPDs in this depression filled with loose volcano-clastics and ignimbrite sheets of continental Neogene units vary from 7 to 12 km, while the geothermal gradient increases from 50 to 68 °C/km. Heat flows were calculated using two different conductivity coefficients of 2.3 and 2.7 Wm-1 K-1. The radiogenic heat production was also obtained between 0.45 and 0.70 μW m-3 in this area. Heat-flow maps were compared with the previous, regional heat-flow map of Turkey and significant differences were observed. In contrast to linear heat-flow increment through the northeast in the previous map in the literature, produced maps in this study include a large, caldera-like circular depression between Nevsehir, Aksaray, Nigde, and Yesilhisar cities indicating high geothermal gradient and higher heat-flow values. In addition, active deformation is evident with young magmatism in the Neogene and Quaternary times and a large volcanic cover on the surface. Boundaries of volcanic eruption centers and buried large intrusions are surrounded with the maxspots of the horizontal gradients of magnetic anomalies. Analytic signal (AS) map pointing-out exact locations of causative bodies is also presented in this study. Circular region in the combined map of AS and maxspots apparently indicates a possible caldera.

  17. Thermal Investigation in the Cappadocia Region, Central Anatolia-Turkey, Analyzing Curie Point Depth, Geothermal Gradient, and Heat-Flow Maps from the Aeromagnetic Data

    Science.gov (United States)

    Bilim, Funda; Kosaroglu, Sinan; Aydemir, Attila; Buyuksarac, Aydin

    2017-09-01

    In this study, curie point depth (CPD), heat flow, geothermal gradient, and radiogenic heat production maps of the Cappadocian region in central Anatolia are presented to reveal the thermal structure from the aeromagnetic data. The large, circular pattern in these maps matches with previously determined shallow (2 km in average) depression. Estimated CPDs in this depression filled with loose volcano-clastics and ignimbrite sheets of continental Neogene units vary from 7 to 12 km, while the geothermal gradient increases from 50 to 68 °C/km. Heat flows were calculated using two different conductivity coefficients of 2.3 and 2.7 Wm-1 K-1. The radiogenic heat production was also obtained between 0.45 and 0.70 μW m-3 in this area. Heat-flow maps were compared with the previous, regional heat-flow map of Turkey and significant differences were observed. In contrast to linear heat-flow increment through the northeast in the previous map in the literature, produced maps in this study include a large, caldera-like circular depression between Nevsehir, Aksaray, Nigde, and Yesilhisar cities indicating high geothermal gradient and higher heat-flow values. In addition, active deformation is evident with young magmatism in the Neogene and Quaternary times and a large volcanic cover on the surface. Boundaries of volcanic eruption centers and buried large intrusions are surrounded with the maxspots of the horizontal gradients of magnetic anomalies. Analytic signal (AS) map pointing-out exact locations of causative bodies is also presented in this study. Circular region in the combined map of AS and maxspots apparently indicates a possible caldera.

  18. The use of chemical shift temperature gradients to establish the paramagnetic susceptibility tensor orientation: Implication for structure determination/refinement in paramagnetic metalloproteins

    Energy Technology Data Exchange (ETDEWEB)

    Xia Zhicheng; Nguyen, Bao D.; La Mar, Gerd N. [University of California, Department of Chemistry (United States)

    2000-06-15

    The use of dipolar shifts as important constraints in refining molecular structure of paramagnetic metalloproteins by solution NMR is now well established. A crucial initial step in this procedure is the determination of the orientation of the anisotropic paramagnetic susceptibility tensor in the molecular frame which is generated interactively with the structure refinement. The use of dipolar shifts as constraints demands knowledge of the diamagnetic shift, which, however, is very often not directly and easily accessible. We demonstrate that temperature gradients of dipolar shifts can serve as alternative constraints for determining the orientation of the magnetic axes, thereby eliminating the need to estimate the diamagnetic shifts. This approach is tested on low-spin, ferric sperm whale cyanometmyoglobin by determining the orientation, anisotropies and anisotropy temperature gradients by the alternate routes of using dipolar shifts and dipolar shift gradients as constraints. The alternate routes ultimately lead to very similar orientation of the magnetic axes, magnetic anisotropies and magnetic anisotropy temperature gradients which, by inference, would lead to an equally valid description of the molecular structure. It is expected that the use of the dipolar shift temperature gradients, rather than the dipolar shifts directly, as constraints will provide an accurate shortcut in a solution structure determination of a paramagnetic metalloprotein.

  19. High temperature gradient nanogap-Pirani micro-sensor with maximum sensitivity around atmospheric pressure

    Science.gov (United States)

    Ghouila-Houri, C.; Talbi, A.; Viard, R.; Moutaouekkil, M.; Elmazria, O.; Gallas, Q.; Garnier, E.; Merlen, A.; Pernod, P.

    2017-09-01

    This letter describes and discusses the design and testing of an efficient nanogap Pirani micro-sensor for pressure measurements in a wide range with a maximum sensitivity around atmospheric pressure. The structure combines a substrate-free heated wire and a mechanical support made of silicon oxide micro-bridges allowing both a constant nanoscale gap between the wire and the substrate and a 1 mm long and 3 μm wide wire. The high aspect ratio of the wire provides a uniform heating profile along the wire and contributes to low pressure detection. On the contrary, both the nanoscale gap and the short wire length between two micro-bridges contribute to shift the high limit of the pressure range. When tested between 10 kPa and 800 kPa, the sensor presents a wide measurement range, not fully reached by the experiments, with a maximum of sensitivity close to the atmospheric pressure and performances with up to 38%/dec sensitivity when operating in a constant temperature mode with an overheat of 20 °C.

  20. [Gradient elevation of temperature startup experiment of thermophilic ASBR treating thermal-hydrolyzed sewage sludge].

    Science.gov (United States)

    Ouyang, Er-Ming; Wang, Wei; Long, Neng; Li, Huai

    2009-04-15

    Startup experiment was conducted for thermophilic anaerobic sequencing batch reactor (ASBR) treating thermal-hydrolyzed sewage sludge using the strategy of the step-wise temperature increment: 35 degrees C-->40 degrees C-->47 degrees C-->53 degrees C. The results showed that the first step-increase (from 35 degrees C to 40 degrees C) and final step-increase (from 47 degrees C to 53 degrees C) had only a slight effect on the digestion process. The second step-increase (from 40 degrees C to 47 degrees C) resulted in a severe disturbance: the biogas production, methane content, CODeffluent and microorganism all have strong disturbance. At the steady stage of thermophilic ASBR treating thermal-hydrolyzed sewage sludge, the average daily gas production, methane content, specific methane production (CH4/CODinfluent), TCOD removal rate and SCOD removal rate were 2.038 L/d, 72.0%, 188.8 mL/g, 63.8%, 83.3% respectively. The results of SEM and DGGE indicated that the dominant species are obviously different at early stage and steady stage.

  1. Novel, cyclic heat dissipation method for the correction of natural temperature gradients in sap flow measurements. Part 2. Laboratory validation.

    Science.gov (United States)

    Reyes-Acosta, J Leonardo; Vandegehuchte, Maurits W; Steppe, Kathy; Lubczynski, Maciek W

    2012-07-01

    Sap flow measurements conducted with thermal dissipation probes (TDPs) are vulnerable to natural temperature gradient (NTG) bias. Few studies, however, attempted to explain the dynamics underlying the NTG formation and its influence on the sensors' signal. This study focused on understanding how the TDP signals are affected by negative and positive temperature influences from NTG and tested the novel cyclic heat dissipation (CHD) method to filter out the NTG bias. A series of three experiments were performed in which gravity-driven water flow was enforced on freshly cut stem segments of Fagus sylvatica L., while an artificial temperature gradient (ATG) was induced. The first experiment sought to confirm the incidence of the ATG on sensors. The second experiment established the mis-estimations caused by the biasing effect of the ATG on standard TDP measurements. The third experiment tested the accuracy of the CHD method to account for the ATG biasing effect, as compared with other cyclic correction methods. During experiments, sap flow measured by TDP was assessed against gravimetric measurements. The results show that negative and positive ATGs were comparable in pattern but substantially larger than field NTGs. Second, the ATG bias caused an overestimation of the standard TDP sap flux density of ∼17 cm(3) cm(-2) h(-1) by 76%, and the sap flux density of ∼2 cm(3) cm(-2) h(-1) by over 800%. Finally, the proposed CHD method successfully reduced the max. ATG bias to 25% at ∼11 cm(3) cm(-2) h(-1) and to 40% at ∼1 cm(3) cm(-2) h(-1). We concluded that: (i) the TDP method is susceptible to NTG especially at low flows; (ii) the CHD method successfully corrected the TDP signal and resulted in generally more accurate sap flux density estimates (mean absolute percentage error ranging between 11 and 21%) than standard constant power TDP method and other cyclic power methods; and (iii) the ATG enforcing system is a suitable way of re-creating NTG for future tests.

  2. Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming

    KAUST Repository

    Sawall, Yvonne

    2015-03-10

    Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12° latitudes featuring a steep temperature gradient between the northern (28.5°N, 21-27°C) and southern (16.5°N, 28-33°C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29°C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals.

  3. Chemical composition separation of a propylene-ethylene random copolymer by high temperature solvent gradient interaction chromatography.

    Science.gov (United States)

    Liu, Yonggang; Phiri, Mohau Justice; Ndiripo, Anthony; Pasch, Harald

    2017-11-03

    A propylene-ethylene random copolymer was fractionated by preparative temperature rising elution fractionation (TREF). The structural heterogeneity of the bulk sample and its TREF fractions was studied by high temperature liquid chromatography with a solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene. HPLC alone cannot resolve those propylene-ethylene copolymers with high ethylene content in the bulk sample, due to their low weight fractions in the bulk sample and a small response factor of these components in the ELSD detector, as well as their broad chemical composition distribution. These components can only be detected after being separated and enriched by TREF followed by HPLC analysis. Chemical composition separations were achieved for TREF fractions with average ethylene contents between 2.1 and 22.0mol%, showing that copolymers with higher ethylene contents were adsorbed stronger in the Hypercarb column and eluted later. All TREF fractions, except the 40°C fraction, were relatively homogeneous in both molar mass and chemical composition. The 40°C fraction was rather broad in both molar mass and chemical composition distributions. 2D HPLC showed that the molar masses of the components containing more ethylene units were getting lower for the 40°C fraction. HPLC revealed and confirmed that co-crystallization influences the separation in TREF of the studied propylene-ethylene copolymer. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. The Radial Temperature Gradient in the Gleeble® Hot-Torsion Test and Its Effect on the Interpretation of Plastic-Flow Behavior

    Science.gov (United States)

    Semiatin, S. L.; Mahaffey, D. W.; Levkulich, N. C.; Senkov, O. N.

    2017-11-01

    The radial temperature gradient developed via direct-resistance heating of round-bar hot-torsion specimens in a Gleeble® machine and its effect on the interpretation of plastic-flow behavior were established using a suite of experimental, analytical, and numerical-simulation tools. Observations of the microstructure variation developed within a γ'-strengthened nickel-base superalloy were used to infer the temperature gradient as well as differences between the temperature at the outer diameter and that indicated by thermocouples welded to the surface. At temperatures of the order of 1375 K (1102 °C), the radial variation of temperature was typically 20 K ( 20 °C). Such variations were in agreement with an analytical heat-conduction model based on the balance of input thermal energy and radiation heat loss at the free surface. Using a constitutive model for LSHR, the effect of the radial temperature gradient on plastic flow during hot torsion was assessed via numerical integration of the torque as a function of radial position for such cases as well as that corresponding to a uniformly-heated sample. These calculations revealed that the torque generated in the non-uniform case is almost identical to that developed in a sample uniformly preheated to a temperature corresponding to that experienced at a fractional radial location of 0.8 in the former case.

  5. Indirect effects of impoundment on migrating fish: temperature gradients in fish ladders slow dam passage by adult Chinook salmon and steelhead.

    Directory of Open Access Journals (Sweden)

    Christopher C Caudill

    Full Text Available Thermal layering in reservoirs upstream from hydroelectric dams can create temperature gradients in fishways used by upstream migrating adults. In the Snake River, Washington, federally-protected adult salmonids (Oncorhynchus spp. often encounter relatively cool water in dam tailraces and lower ladder sections and warmer water in the upstream portions of ladders. Using radiotelemetry, we examined relationships between fish passage behavior and the temperature difference between the top and bottom of ladders (∆T at four dams over four years. Some spring Chinook salmon (O. tshawytscha experienced ∆T ≥ 0.5 °C. Many summer and fall Chinook salmon and summer steelhead (O. mykiss experienced ∆T ≥ 1.0 °C, and some individuals encountered ΔT > 4.0°C. As ΔT increased, migrants were consistently more likely to move down fish ladders and exit into dam tailraces, resulting in upstream passage delays that ranged from hours to days. Fish body temperatures equilibrated to ladder temperatures and often exceeded 20°C, indicating potential negative physiological and fitness effects. Collectively, the results suggest that gradients in fishway water temperatures present a migration obstacle to many anadromous migrants. Unfavorable temperature gradients may be common at reservoir-fed fish passage facilities, especially those with seasonal thermal layering or stratification. Understanding and managing thermal heterogeneity at such sites may be important for ensuring efficient upstream passage and minimizing stress for migratory, temperature-sensitive species.

  6. Development of core ion temperature gradients and edge sheared flows in a helicon plasma device investigated by laser induced fluorescence measurements

    Science.gov (United States)

    Thakur, S. C.; Gosselin, J. J.; McKee, J.; Scime, E. E.; Sears, S. H.; Tynan, G. R.

    2016-08-01

    We report experimental observation of ion heating and subsequent development of a prominent ion temperature gradient in the core of a linear magnetized plasma device, and the controlled shear de-correlation experiment. Simultaneously, we also observe the development of strong sheared flows at the edge of the device. Both the ion temperature and the azimuthal velocity profiles are quite flat at low magnetic fields. As the magnetic field is increased, the core ion temperature increases, producing centrally peaked ion temperature profiles and therefore strong radial gradients in the ion temperature. Similarly, we observe the development of large azimuthal flows at the edge, with increasing magnetic field, leading to strong radially sheared plasma flows. The ion velocities and temperatures are derived from laser induced fluorescence measurements of Doppler resolved velocity distribution functions of argon ions. These features are consistent with the previous observations of simultaneously existing radially separated multiple plasma instabilities that exhibit complex plasma dynamics in a very simple plasma system. The ion temperature gradients in the core and the radially sheared azimuthal velocities at the edge point to mechanisms that can drive the multiple plasma instabilities, that were reported earlier.

  7. Core-ion temperature measurement of the ADITYA tokamak using passive charge exchange neutral particle energy analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Santosh P.; Ajay, Kumar; Mishra, Priyanka; Dhingra, Rajani D.; Govindarajan, J. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India)

    2013-02-15

    Core-ion temperature measurements have been carried out by the energy analysis of passive charge exchange (CX) neutrals escaping out of the ADITYA tokamak plasma (minor radius, a= 25 cm and major radius, R= 75 cm) using a 45 Degree-Sign parallel plate electrostatic energy analyzer. The neutral particle analyzer (NPA) uses a gas cell configuration for re-ionizing the CX-neutrals and channel electron multipliers (CEMs) as detectors. Energy calibration of the NPA has been carried out using ion-source and {Delta}E/E of high-energy channel has been found to be {approx}10%. Low signal to noise ratio (SNR) due to VUV reflections on the CEMs was identified during the operation of the NPA with ADITYA plasma discharges. This problem was rectified by upgrading the system by incorporating the additional components and arrangements to suppress VUV radiations and improve its VUV rejection capabilities. The noise rejection capability of the NPA was experimentally confirmed using a standard UV-source and also during the plasma discharges to get an adequate SNR (>30) at the energy channels. Core-ion temperature T{sub i}(0) during flattop of the plasma current has been measured to be up to 150 eV during ohmically heated plasma discharges which is nearly 40% of the average core-electron temperature (typically T{sub e}(0) {approx} 400 eV). The present paper describes the principle of tokamak ion temperature measurement, NPA's design, development, and calibration along with the modifications carried out for minimizing the interference of plasma radiations in the CX-spectrum. Performance of the NPA during plasma discharges and experimental results on the measurement of ion-temperature have also been reported here.

  8. Effects of Withdrawal Rate and Temperature Gradient on the Microstructure Evolution in Directionally Solidified NiAl-36Cr-6Mo Hypereutectic Alloy

    Science.gov (United States)

    Shang, Zhao; Shen, Jun; Zhang, Jian-Fei; Wang, Lei; Qin, Ling; Fu, Heng-Zhi

    2014-09-01

    The effects of withdrawal rate and temperature gradient on the microstructure and growth interface morphology in directionally solidified Ni-29Al-36Cr-6Mo(at.%) hypereutectic alloy were investigated. Under the temperature gradient of 250 K/cm, well-aligned eutectic microstructure with lamellar morphology was obtained at the withdrawal rate of 6 μm/s. When the withdrawal rate was 10 μm/s, the microstructure changed to Cr(Mo) dendrites + eutectic lamellae. With the increasing withdrawal rate, the interdendritic eutectic growth interface changed from planar to cellular, the number of primary Cr(Mo) dendrites became greater, and the microstructure was refined. When the temperature gradient increased to 600 K/cm, the coupled eutectic growth zone of NiAl-Cr(Mo) alloy was expanded; a well-aligned eutectic microstructure could be obtained at higher rate of 10 μm/s. Furthermore, the planar/cellular transition rate of the interdendritic eutectic growth interface increased. Even at the same withdrawal rate, the number of primary Cr(Mo) dendrites was less and the microstructure was finer under the temperature gradient of 600 K/cm.

  9. Effect of magnetic field on the temperature gradient in Y1Ba2Cu3O7 - δ + Eu1Ba2Cu3O7 - δ rods

    Science.gov (United States)

    Churin, S. A.

    2009-05-01

    A method for growing Y1Ba2Cu3O7 - δ + Eu1Ba2Cu3O7 - δ (YBCO-EBCO) high-temperature superconductor rods is described. The temperature dependences of the resistance of rods in a magnetic field of B = 0.6 T and in the absence of the field ( B = 0 T) are presented. The current-voltage characteristics of YBCO-EBCO rods have been measured at liquid nitrogen temperature have been measured in the absence and presence of a magnetic field. It is shown that the magnetic field significantly decreases the temperature gradient arising when the rod leaves the superconducting state.

  10. Experimental observation of transient δ18O interaction between snow and advective airflow under various temperature gradient conditions

    Directory of Open Access Journals (Sweden)

    P. P. Ebner

    2017-07-01

    Full Text Available Stable water isotopes (δ18O obtained from snow and ice samples of polar regions are used to reconstruct past climate variability, but heat and mass transport processes can affect the isotopic composition. Here we present an experimental study on the effect of airflow on the snow isotopic composition through a snow pack in controlled laboratory conditions. The influence of isothermal and controlled temperature gradient conditions on the δ18O content in the snow and interstitial water vapour is elucidated. The observed disequilibrium between snow and vapour isotopes led to the exchange of isotopes between snow and vapour under non-equilibrium processes, significantly changing the δ18O content of the snow. The type of metamorphism of the snow had a significant influence on this process. These findings are pertinent to the interpretation of the records of stable isotopes of water from ice cores. These laboratory measurements suggest that a highly resolved climate history is relevant for the interpretation of the snow isotopic composition in the field.

  11. Forest biomass density across large climate gradients in northern South America is related to water availability but not with temperature.

    Science.gov (United States)

    Álvarez-Dávila, Esteban; Cayuela, Luis; González-Caro, Sebastián; Aldana, Ana M; Stevenson, Pablo R; Phillips, Oliver; Cogollo, Álvaro; Peñuela, Maria C; von Hildebrand, Patricio; Jiménez, Eliana; Melo, Omar; Londoño-Vega, Ana Catalina; Mendoza, Irina; Velásquez, Oswaldo; Fernández, Fernando; Serna, Marcela; Velázquez-Rua, Cesar; Benítez, Doris; Rey-Benayas, José M

    2017-01-01

    Understanding and predicting the likely response of ecosystems to climate change are crucial challenges for ecology and for conservation biology. Nowhere is this challenge greater than in the tropics as these forests store more than half the total atmospheric carbon stock in their biomass. Biomass is determined by the balance between biomass inputs (i.e., growth) and outputs (mortality). We can expect therefore that conditions that favor high growth rates, such as abundant water supply, warmth, and nutrient-rich soils will tend to correlate with high biomass stocks. Our main objective is to describe the patterns of above ground biomass (AGB) stocks across major tropical forests across climatic gradients in Northwestern South America. We gathered data from 200 plots across the region, at elevations ranging between 0 to 3400 m. We estimated AGB based on allometric equations and values for stem density, basal area, and wood density weighted by basal area at the plot-level. We used two groups of climatic variables, namely mean annual temperature and actual evapotranspiration as surrogates of environmental energy, and annual precipitation, precipitation seasonality, and water availability as surrogates of water availability. We found that AGB is more closely related to water availability variables than to energy variables. In northwest South America, water availability influences carbon stocks principally by determining stand structure, i.e. basal area. When water deficits increase in tropical forests we can expect negative impact on biomass and hence carbon storage.

  12. Experimental observation of transient δ18O interaction between snow and advective airflow under various temperature gradient conditions

    Science.gov (United States)

    Ebner, Pirmin Philipp; Steen-Larsen, Hans Christian; Stenni, Barbara; Schneebeli, Martin; Steinfeld, Aldo

    2017-07-01

    Stable water isotopes (δ18O) obtained from snow and ice samples of polar regions are used to reconstruct past climate variability, but heat and mass transport processes can affect the isotopic composition. Here we present an experimental study on the effect of airflow on the snow isotopic composition through a snow pack in controlled laboratory conditions. The influence of isothermal and controlled temperature gradient conditions on the δ18O content in the snow and interstitial water vapour is elucidated. The observed disequilibrium between snow and vapour isotopes led to the exchange of isotopes between snow and vapour under non-equilibrium processes, significantly changing the δ18O content of the snow. The type of metamorphism of the snow had a significant influence on this process. These findings are pertinent to the interpretation of the records of stable isotopes of water from ice cores. These laboratory measurements suggest that a highly resolved climate history is relevant for the interpretation of the snow isotopic composition in the field.

  13. Approach to analyze the diversity of myxobacteria in soil by semi-nested PCR-denaturing gradient gel electrophoresis (DGGE based on taxon-specific gene.

    Directory of Open Access Journals (Sweden)

    Baiyuan Li

    Full Text Available The genotypic diversity of insoluble macromolecules degraded myxobacteria, provided an opportunity to discover new bacterial resources and find new ecological functions. In this study, we developed a semi-nested-PCR-denaturing gradient gel electrophoresis (DGGE strategy to determine the presence and genotypic diversity of myxobacteria in soil. After two rounds of PCR with myxobacteria-specific primers, an 194 bp fragment of mglA, a key gene involved in gliding motility, suitable for DGGE was obtained. A large number of bands were observed in DGGE patterns, indicating diverse myxobacteria inhabiting in soils. Furthermore, sequencing and BLAST revealed that most of the bands belonged to the myxobacteria-group, and only three of the twenty-eight bands belonged to other group, i.e., Deinococcus maricopensis. The results verified that myxobacterial strains with discrepant sequence compositions of gene mglA could be discriminated by DGGE with myxobacteria-specific primers. Collectively, the developed semi-nested-PCR-DGGE strategy is a useful tool for studying the diversity of myxobacteria.

  14. A practical approach for predicting retention time shifts due to pressure and temperature gradients in ultra-high-pressure liquid chromatography.

    Science.gov (United States)

    Åsberg, Dennis; Chutkowski, Marcin; Leśko, Marek; Samuelsson, Jörgen; Kaczmarski, Krzysztof; Fornstedt, Torgny

    2017-01-06

    Large pressure gradients are generated in ultra-high-pressure liquid chromatography (UHPLC) using sub-2μm particles causing significant temperature gradients over the column due to viscous heating. These pressure and temperature gradients affect retention and ultimately result in important selectivity shifts. In this study, we developed an approach for predicting the retention time shifts due to these gradients. The approach is presented as a step-by-step procedure and it is based on empirical linear relationships describing how retention varies as a function of temperature and pressure and how the average column temperature increases with the flow rate. It requires only four experiments on standard equipment, is based on straightforward calculations, and is therefore easy to use in method development. The approach was rigorously validated against experimental data obtained with a quality control method for the active pharmaceutical ingredient omeprazole. The accuracy of retention time predictions was very good with relative errors always less than 1% and in many cases around 0.5% (n=32). Selectivity shifts observed between omeprazole and the related impurities when changing the flow rate could also be accurately predicted resulting in good estimates of the resolution between critical peak pairs. The approximations which the presented approach are based on were all justified. The retention factor as a function of pressure and temperature was studied in an experimental design while the temperature distribution in the column was obtained by solving the fundamental heat and mass balance equations for the different experimental conditions. We strongly believe that this approach is sufficiently accurate and experimentally feasible for this separation to be a valuable tool when developing a UHPLC method. After further validation with other separation systems, it could become a useful approach in UHPLC method development, especially in the pharmaceutical industry where

  15. How do two Lupinus species respond to temperature along an altitudinal gradient in the Venezuelan Andes? ¿Cómo responden dos especies de Lupinus a la temperatura en un gradiente altitudinal en los Andes venezolanos?

    Directory of Open Access Journals (Sweden)

    FERMÍN RADA

    2008-09-01

    Full Text Available Temperature determines plant formations and species distribution along altitudinal gradients. Plants in the tropical high Andes, through different physiological and morphological characteristics, respond to freezing night temperatures and high daytime energy inputs which occur anytime of the year. The main objective of this study was to characterize day and night temperature related responses of two Lupinus species with different altitudinal ranges (L. meridanus, 1,800-3,600 and L. eromonomos, 3,700-4,300 m of altitude. Are there differences in night low temperature resistance mechanisms between the species along the gradient? How do these species respond, in terms of optimum temperature for photosynthesis, to increasing altitude? Lupinus meridanus shows frost avoidance, in contrast to L. eromonomos, which tolerates freezing at higher altitudes. Optimum temperature for photosynthesis decreases along the gradient for both species. Maximum C0(2 assimilation rates were higher in L. meridanus, while L. eromonomos showed decreasing C0(2 assimilation rates at the higher altitude. In most cases, measured daily leaf temperature is always within the 80 % of optimum for photosynthesis. L. meridanus7 upper distribution limit seems to be restricted by cold resistance mechanisms, while L. eromonomos7 to a combination of both cold resistance and to C0(2 assimilation responses at higher altitudes.La temperatura determina las formaciones vegetales y la distribución de especies a lo largo de gradientes altitudinales. Las plantas en los altos Andes tropicales, a través de diferentes características morfológicas y fisiológicas, responden a temperaturas congelantes nocturnas y altas entradas energéticas durante el día en cualquier momento del año. El objetivo principal de este estudio fue caracterizar las respuestas relacionadas con temperaturas diurnas y nocturnas en dos especies de Lupinus con diferente distribución altitudinal (L. meridanus, 1

  16. Development and Testing of a Model to Assess Subsurface Moisture Gradients From Diurnal Surface Temperatures and Soil Thermophysical Properties

    Science.gov (United States)

    Griggs, L. E.; Arvidson, R. E.

    2002-12-01

    A one-dimensional, finite difference coupled heat and moisture transfer model for unsaturated zone porous media flow has been developed and tested. Inputs to the model include soil surface excursions, site topography, meteorological data, and detailed information about the soil thermophysical and hydraulic properties. Assuming homogeneity or knowledge of the stratification of the soil column and steady-state conditions (i.e. no recharge), the output is a profile of moisture gradients in the subsurface extending to the depth of diurnal fluctuations of moisture. This model primarily differs from existing one-dimensional heat and transport models in its incorporation of the 3-dimensional topography and diurnal shadowing of the study site and in its ability to provide information about relatively deep moisture profiles. These profiles are produced through the assumption of a moisture source (a water table or pseudo water table) at a given depth. The model was subject to sensitivity analyses and was calibrated in August 2002 in the Kau Desert, Hawaii, in an unvegetated area with layers of high moisture content in the subsurface. Field work consisted of 24 contiguous hours of monitoring soil surface temperature, meteorological data, and moisture content at several depths of the soil profile. Thermal conductivity of the soil was determined in situ, and field saturated hydraulic conductivity was determined with a Guelph permeameter. The other thermophysical and hydraulic soil properties of interest (specific heat, moisture retention curve, bulk density, porosity, grain axes, and van Genuchten parameters) were determined through laboratory experimentation. Results from the calibration exercise will be presented.

  17. Phase-field study on geometry-dependent migration behavior of voids under temperature gradient in UO2 crystal matrix

    Science.gov (United States)

    Chen, Weijin; Peng, Yuyi; Li, Xu'an; Chen, Kelang; Ma, Jun; Wei, Lingfeng; Wang, Biao; Zheng, Yue

    2017-10-01

    In this work, a phase-field model is established to capture the void migration behavior under a temperature gradient within a crystal matrix, with an appropriate consideration of the surface diffusion mechanism and the vapor transport mechanism. The interfacial energy and the coupling between the vacancy concentration field and the crystal order parameter field are carefully modeled. Simulations are performed on UO2. The result shows that for small voids (with an area ≤ πμm2), the well-known characteristics of void migration, in consistence with the analytical model, can be recovered. The migration is manifested by a constant velocity and a minor change of the void shape. In contrast, for large voids (with an area of ˜10 μm2) initially in circular shapes, significant deformation of the void from a circular to cashew-like shape is observed. After long-time migration, the deformed void would split into smaller voids. The size-dependent behavior of void migration is due to the combined effect of the interfacial energy (which tends to keep the void in circular shape) and the surface diffusion flow (which tends to deform the void due to the nonuniform diffusion along the surface). Moreover, the initial shape of the void modifies the migration velocity and the time point when splitting occurs (for large voids) at the beginning of migration due to the shape relaxation of the void. However, it has a minor effect on the long-time migration. Our work reveals novel void migration behaviors in conditions where the surface-diffusion mechanism is dominant over the vapor transport mechanism; meanwhile, the size of the void lies at a mediate size range.

  18. Using torsional forces to explain the gradient temperature Raman spectra of endosulfan isomers and its irreversible isomerization

    Science.gov (United States)

    Schmidt, Walter F.; Hapeman, Cathleen J.; McConnell, Laura L.; Rice, Clifford P.; Broadhurst, C. Leigh; Nguyen, Julie K.; Qin, Jianwei; Chao, Kuanglin; Kim, Moon S.; Shelton, Daniel R.

    2017-07-01

    Since the 1950's, the broad-spectrum, organochlorine insecticide endosulfan (6,7,8, 9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) has been used on numerous crops. Due to its persistence, bioaccumulation, long-range transport, and adverse effects to human health and ecosystems, it was officially identified as a persistent organic pollutant (POP) in 2011. The last uses in the United States were phased out in 2016. Endosulfan consists of two diastereomers, α-endosulfan and β-endosulfan, and while the α-isomer exists as two asymmetrical, twist-chair enantiomers which interchange, the β-isomer is a symmetrical-chair conformation. In addition, the β-isomer was found to isomerize to the α-isomer. Gradient Temperature Raman Spectroscopy (GTRS) enables identification the molecular sites at which bending vibrational modes becomes twisting or wagging vibrational modes. Previous studies using GTRS and chemical calculations afforded evidence for specific bond movements and the irreversibility of the isomerization mechanism. However, not all of the vibrational modes observed in the spectra could be explained. Thus, new analyses of the GTRS data were conducted to examine the effects of torsional forces on the bond movement, which allowed for the identification of all the peaks. These newly-identified torsional forces provide further confirmation of the isomerization mechanism and its irreversibility. Finally, this isomerization explains why β-endosulfan is rarely detected in the atmosphere.

  19. Using the Weak-Temperature Gradient Approximation to Evaluate Parameterizations: An Example of the Transition From Suppressed to Active Convection

    Science.gov (United States)

    Daleu, C. L.; Plant, R. S.; Woolnough, S. J.

    2017-10-01

    Two single-column models are fully coupled via the weak-temperature gradient approach. The coupled-SCM is used to simulate the transition from suppressed to active convection under the influence of an interactive large-scale circulation. The sensitivity of this transition to the value of mixing entrainment within the convective parameterization is explored. The results from these simulations are compared with those from equivalent simulations using coupled cloud-resolving models. Coupled-column simulations over nonuniform surface forcing are used to initialize the simulations of the transition, in which the column with suppressed convection is forced to undergo a transition to active convection by changing the local and/or remote surface forcings. The direct contributions from the changes in surface forcing are to induce a weakening of the large-scale circulation which systematically modulates the transition. In the SCM, the contributions from the large-scale circulation are dominated by the heating effects, while in the CRM the heating and moistening effects are about equally divided. A transition time is defined as the time when the rain rate in the dry column is halfway to the value at equilibrium after the transition. For the control value of entrainment, the order of the transition times is identical to that obtained in the CRM, but the transition times are markedly faster. The locally forced transition is strongly delayed by a higher entrainment. A consequence is that for a 50% higher entrainment the transition times are reordered. The remotely forced transition remains fast while the locally forced transition becomes slow, compared to the CRM.

  20. Molecular composition of soil organic matter with land-use change along a bi-continental mean annual temperature gradient.

    Science.gov (United States)

    Pisani, Oliva; Haddix, Michelle L; Conant, Richard T; Paul, Eldor A; Simpson, Myrna J

    2016-12-15

    Soil organic matter (SOM) is critical for maintaining soil fertility and long-term agricultural sustainability. The molecular composition of SOM is likely altered due to global climate and land-use change; but rarely are these two aspects studied in tandem. Here we used molecular-level techniques to examine SOM composition along a bi-continental (from North to South America) mean annual temperature (MAT) gradient from seven native grassland/forest and cultivated/pasture sites. Biomarker methods included solvent extraction, base hydrolysis and cupric (II) oxide oxidation for the analysis of free lipids of plant and microbial origin, ester-bound lipids from cutin and suberin, and lignin-derived phenols, respectively. Solid-state 13C nuclear magnetic resonance (NMR) was used to examine the overall composition of SOM. Soil cultivation was found to increase the amount of microbial-derived compounds at warmer temperatures (up to 17% increase). The cultivated soils were characterized by much lower contributions of plant-derived SOM components compared to the native soils (up to 64% lower at the coldest site). In addition, cultivation caused an increase in lignin and cutin degradation (up to 68 and 15% increase, respectively), and an increase in the amount of suberin-derived inputs (up to 54% increase). Clear differences in the molecular composition of SOM due to soil cultivation were observed in soils of varying mineral composition and were attributed to disturbance, different vegetation inputs, soil aggregate destruction and MAT. A high organic allophanic tropical soil was characterized by its protection of carbohydrates and nitrogen-containing compounds. The conversion of native to cultivated land shows significant shifts in the degradation stage of SOM. In particular, cutin-derived compounds which are believed to be part of the stable SOM pool may undergo enhanced degradation with long-term cultivation and disruption of soil aggregates. On a per year basis, the total

  1. Experimental measurements of the SP response to concentration and temperature gradients in sandstones with application to subsurface geophysical monitoring

    National Research Council Canada - National Science Library

    Leinov, E; Jackson, M. D

    2014-01-01

    .... Likewise, with the exception of borehole SP logging, exclusion‐diffusion potentials arising from concentration gradients are also neglected or, at best, it is assumed that the diffusion potential dominates...

  2. Correlations of the energy-momentum tensor via gradient flow in SU(3) Yang-Mills theory at finite temperature

    Science.gov (United States)

    Kitazawa, Masakiyo; Iritani, Takumi; Asakawa, Masayuki; Hatsuda, Tetsuo

    2017-12-01

    Euclidean two-point correlators of the energy-momentum tensor (EMT) in SU(3) gauge theory on the lattice are studied on the basis of the Yang-Mills gradient flow. The entropy density and the specific heat obtained from the two-point correlators are shown to be in good agreement with those from the one-point functions of EMT. These results constitute a first step toward the first principle simulations of the transport coefficients with the gradient flow.

  3. Spatio-Temporal Analyses of Symbiodinium Physiology of the Coral Pocillopora verrucosa along Large-Scale Nutrient and Temperature Gradients in the Red Sea

    KAUST Repository

    Sawall, Yvonne

    2014-08-19

    Algal symbionts (zooxanthellae, genus Symbiodinium) of scleractinian corals respond strongly to temperature, nutrient and light changes. These factors vary greatly along the north-south gradient in the Red Sea and include conditions, which are outside of those typically considered optimal for coral growth. Nevertheless, coral communities thrive throughout the Red Sea, suggesting that zooxanthellae have successfully acclimatized or adapted to the harsh conditions they experience particularly in the south (high temperatures and high nutrient supply). As such, the Red Sea is a region, which may help to better understand how zooxanthellae and their coral hosts successfully acclimatize or adapt to environmental change (e. g. increased temperatures and localized eutrophication). To gain further insight into the physiology of coral symbionts in the Red Sea, we examined the abundance of dominant Symbiodinium types associated with the coral Pocillopora verrucosa, and measured Symbiodinium physiological characteristics (i.e. photosynthetic processes, cell density, pigmentation, and protein composition) along the latitudinal gradient of the Red Sea in summer and winter. Despite the strong environmental gradients from north to south, our results demonstrate that Symbiodinium microadriaticum (type A1) was the predominant species in P. verrucosa along the latitudinal gradient. Furthermore, measured physiological characteristics were found to vary more with prevailing seasonal environmental conditions than with region-specific differences, although the measured environmental parameters displayed much higher spatial than temporal variability. We conclude that our findings might present the result of long-term acclimatization or adaptation of S. microadriaticum to regionally specific conditions within the Red Sea. Of additional note, high nutrients in the South correlated with high zooxanthellae density indicating a compensation for a temperature-driven loss of photosynthetic

  4. Vapor flux and recrystallization during dry snow metamorphism under a steady temperature gradient as observed by time-lapse micro-tomography

    Directory of Open Access Journals (Sweden)

    B. R. Pinzer

    2012-10-01

    Full Text Available Dry snow metamorphism under an external temperature gradient is the most common type of recrystallization of snow on the ground. The changes in snow microstructure modify the physical properties of snow, and therefore an understanding of this process is essential for many disciplines, from modeling the effects of snow on climate to assessing avalanche risk. We directly imaged the microstructural changes in snow during temperature gradient metamorphism (TGM under a constant gradient of 50 K m−1, using in situ time-lapse X-ray micro-tomography. This novel and non-destructive technique directly reveals the amount of ice that sublimates and is deposited during metamorphism, in addition to the exact locations of these phase changes. We calculated the average time that an ice volume stayed in place before it sublimated and found a characteristic residence time of 2–3 days. This means that most of the ice changes its phase from solid to vapor and back many times in a seasonal snowpack where similar temperature conditions can be found. Consistent with such a short timescale, we observed a mass turnover of up to 60% of the total ice mass per day. The concept of hand-to-hand transport for the water vapor flux describes the observed changes very well. However, we did not find evidence for a macroscopic vapor diffusion enhancement. The picture of {temperature gradient metamorphism} produced by directly observing the changing microstructure sheds light on the micro-physical processes and could help to improve models that predict the physical properties of snow.

  5. The research of the cross-links effect influence in the color matrix photodetector on an error of the air tract vertical temperature gradient determination

    Science.gov (United States)

    Nekrylov, Ivan S.; Kleshchenok, Maksim A.; Timofeev, Aleksandr N.; Sycheva, Elena A.; Gusarov, Vadim F.

    2017-06-01

    The research of the cross-links effect influence in the color matrix photodetector on an error of the air tract vertical temperature gradient determination is provided. It is invited to consider the influence of the signals from matrix photodetector channels on each other. There is a method to determine the value of the cross-links effect ant its influence on the energy center coordinates determination.

  6. A Conceptual Model to Link Anomalously High Temperature Gradients in the Cerros del Rio Volcanic Field to Regional Flow in the Espanola Basin, New Mexico

    Science.gov (United States)

    Fillingham, E. J.; Keller, S. N.; McCullough, K. R.; Watters, J.; Weitering, B.; Wilce, A. M.; Folsom, M.; Kelley, S.; Pellerin, L.

    2015-12-01

    Temperature-depth well data along with electromagnetic (EM) data were collected by students of the Summer of Applied Geophysics Experience (SAGE) 2015 field season in the Espanola Basin, New Mexico. The data from this year, in addition to data acquired since 2013, were used to construct a conceptual east-west cross-section of the Espanola Basin and the adjacent highlands in order to evaluate the regional flow system. Vertical geothermal gradients from several monitoring wells were measured using a thermistor. Anomalously warm geothermal gradients were mapped in the Cerros del Rio volcanic field in the basin just east of the Rio Grande. Temperature gradients are up to 70℃/km, while the background geothermal gradients in the Rio Grande rift zone generally show 28℃-35℃/km. This anomaly extends to the Buckman well field, which supplies water to the city of Santa Fe. Overpumping of this well field has led to subsidence in the past. However, discharge temperature plots indicate that the temperature gradients of the Buckman field may be rebounding as pumping is reduced. Audiomagnetotelluric (AMT) and transient electromagnetic (TEM) data were acquired in the vicinity of three monitoring wells. TEM and AMT methods complement each other with the former having depths of investigation of less than ten to hundreds of meters and AMT having depths of investigation comparable to the wells deeper than 500m. These datasets were used collectively to image the subsurface stratigraphy and, more specifically, the hydrogeology related to shallow aquifers. The EM data collected at these wells showed a trend indicating a shallow aquifer with a shallower resistive layer of approximately 100 ohm-m at 70-100 meters depth. Beneath this resistive layer we resolved a more conductive, clay-rich layer of 10 ohm-m. These resistivity profiles compliment the electrical logs provided by Jet West, which indicate shallower sandstone interbedded with silt on top of more silt-dominant layers. Our

  7. Unprecedented quality factors at accelerating gradients up to 45 MVm-1 in niobium superconducting resonators via low temperature nitrogen infusion

    Science.gov (United States)

    Grassellino, A.; Romanenko, A.; Trenikhina, Y.; Checchin, M.; Martinello, M.; Melnychuk, O. S.; Chandrasekaran, S.; Sergatskov, D. A.; Posen, S.; Crawford, A. C.; Aderhold, S.; Bice, D.

    2017-09-01

    We report the finding of new surface treatments that permits one to manipulate the niobium resonator nitrogen content in the first few nanometers in a controlled way, and the resonator fundamental Mattis-Bardeen surface resistance and residual resistance accordingly. In particular, we find surface ‘infusion’ conditions that systematically (a) increase the quality factor of these 1.3 GHz superconducting radio frequency (SRF) bulk niobium resonators, up to very high gradients; (b) increase the achievable accelerating gradient of the cavity compared to its own baseline with state-of-the-art surface processing. Cavities subject to the new surface process have more than two times the state-of-the-art Q at 2 K for accelerating fields >35 MVm-1. Moreover, very high accelerating gradients ˜45 MVm-1 are repeatedly reached, which correspond to peak magnetic surface fields of 190 mT, among the highest measured for bulk niobium cavities. These findings open the opportunity to tailor the surface impurity content distribution to maximize performance in Q and gradients, and have therefore very important implications on future performance and cost of SRF based accelerators. They also help deepen the understanding of the physics of the RF niobium cavity surface.

  8. Chemical and isotopic fractionation of wet andesite in a temperature gradient: Experiments and models suggesting a new mechanism of magma differentiation

    Science.gov (United States)

    Huang, F.; Lundstrom, C. C.; Glessner, J.; Ianno, A.; Boudreau, A.; Li, J.; Ferré, E. C.; Marshak, S.; DeFrates, J.

    2009-02-01

    Piston-cylinder experiments were conducted to investigate the behavior of partially molten wet andesite held within an imposed temperature gradient at 0.5 GPa. In one experiment, homogenous andesite powder (USGS rock standard AGV-1) with 4 wt.% H 2O was sealed in a double capsule assembly for 66 days. The temperature at one end of this charge was held at 950 °C, and the temperature at the other end was kept at 350 °C. During the experiment, thermal migration (i.e., diffusion in a thermal gradient) took place, and the andesite underwent compositional and mineralogical differentiation. The run product can be broadly divided into three portions: (1) the top third, at the hot end, contained 100% melt; (2) the middle-third contained crystalline phases plus progressively less melt; and (3) the bottom third, at the cold end, consisted of a fine-grained, almost entirely crystalline solid of granitic composition. Bulk major- and trace-element compositions change down temperature gradient, reflecting the systematic change in modal mineralogy. These changes mimic differentiation trends produced by fractional crystallization. The change in composition throughout the run product indicates that a fully connected hydrous silicate melt existed throughout the charge, even in the crystalline, cold bottom region. Electron Backscatter Diffraction analysis of the run product indicates that no preferred crystallographic orientation of minerals developed in the run product. However, a significant anisotropy of magnetic susceptibility was observed, suggesting that new crystals of magnetite were elongated in the direction of the thermal gradient. Further, petrographic observation reveals alignment of hornblende parallel to the thermal gradient. Finally, the upper half of the run product shows large systematic variations in Fe-Mg isotopic composition reflecting thermal diffusion, with the hot end systematically enriched in light isotopes. The overall δ 56Fe IRMM-14 and δ 26Mg DSM-3

  9. Investigation of microstructure and V-defect formation inInxGa1-xN/GaN MQW grown using temperature-gradient MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, M.C.; Liliental-Weber, Z.; Zakharov, D.N.; McCready,D.E.; Jorgenson, R.J.; Wu, J.; Shan, W.; Bourret-Courchesne, E.D.

    2004-11-19

    Temperature-gradient Metalorganic Chemical Vapor Deposition was used to deposit In{sub x}Ga{sub 1-x}N/GaN multiple quantum well structures with a concentration gradient of indium across the wafer. These multiple quantum well structures were deposited on low defect density (2 x 10{sup 8} cm{sup -2}) GaN template layers for investigation of microstructural properties and V-defect (pinhole) formation. Room temperature photoluminescence and photomodulated transmission were used for optical characterization which show a systematic decrease in emission energy for a decrease in growth temperature. Triple-axis X-ray diffraction, scanning electron microscopy and cross-section transmission electron microscopy were used to obtain microstructural properties of different regions across the wafer. Results show that there is a decrease in crystal quality and an increase in V-defect formation with increasing indium concentration. A direct correlation was found between V-defect density and growth temperature due to increased strain and indium segregation for increasing indium concentration.

  10. A High-Resolution Multi-Proxy Lake Sediment Record from Torfdalsvatn Suggests an Enhanced Temperature Gradient Between North and South Iceland During the Early Holocene

    Science.gov (United States)

    Florian, Christopher; Geirsdóttir, Áslaug; Miller, Gifford; Axford, Yarrow

    2015-04-01

    Torfdalsvatn (66° 3'41.73"N, 20°23'14.26"W) is a relatively small (0.4 km2) and shallow (z=5.8 m) lake on the Skagi Peninsula of northern Iceland approximately 0.5 km from the modern coastline. This location is ideal for comparison with the many marine core records from the North Iceland Shelf that record variability in the northern extent of the warm Irminger Current, one of the primary controls on regional climate. To develop a record of north Iceland Holocene terrestrial climate, we analyzed a 8.4 m sediment core at 15-30 year resolution from approximately 12 ka to present using multiple proxies including sedimentary pigments, organic carbon flux, carbon to nitrogen ratio and stable isotopes, as well as biogenic silica measured by Fourier Transform Infrared Spectroscopy (FTIR-S). Results show gradual warming during the early Holocene, with stable soil development and peak aquatic productivity not occurring until after 8 ka. Increased aquatic productivity and a stable terrestrial environment between 6 and 2 ka indicate peak Holocene warmth in this interval. Aquatic productivity abruptly decreases at 1.8 ka associated with an increase in minerogenic material from landscape destabilization in the catchment with the onset of late Holocene cooling. At 1ka, the proportion of terrestrially-derived organic matter deposited in the lake sediment increases, indicating significant destabilization of soil horizons due to continued cooling and potential human settlement. This record is in good agreement with composite north Iceland chironomid-inferred July air temperatures from Axford et al. (2007), which show peak summer temperatures occurring between approximately 5 and 2 ka. The time of peak warmth at Torfdalsvatn is associated with peak biogenic carbonate concentration in the marine core MD99-2269, indicating an influx of warm Irminger waters. This is in contrast with Holocene climate records obtained from lakes in south and west Iceland, implying that there was an

  11. Effects of an experimental increase of temperature and drought on the photosynthetic performance of two ericaceous shrub species along a north-south European gradient

    DEFF Research Database (Denmark)

    Llorens, L.; Penuelas, J.; Beier, C.

    2004-01-01

    Plant ecophysiological changes in response to climatic change may be different in northern and southern European countries because different abiotic factors constrain plant physiological activity. We studied the effects of experimental warming and drought on the photosynthetic performance of two...... ericaceous shrubs (Erica multiflora and Calluna vulgaris) along a European gradient of temperature and precipitation (UK, Denmark, The Netherlands, and Spain). At each site, a passive warming treatment was applied during the night throughout the whole year, whereas the drought treatment excluded rain events...... with the geographical gradient in water availability. Accordingly, there was a strong correlation between net photosynthetic rates and the accumulated rainfall over the growing season. Droughted plants showed lower leaf gas exchange rates than control plants in the four sites. Interestingly, although leaf...

  12. On-Line Hydrogen-Isotope Measurements of Organic Samples Using Elemental Chromium : An Extension for High Temperature Elemental-Analyzer Techniques

    NARCIS (Netherlands)

    Gehre, Matthias; Renpenning, Julian; Gilevska, Tetyana; Qi, Haiping; Coplen, Tyler B.; Meijer, Harro A. J.; Brand, Willi A.; Schimmelmann, Arndt

    2015-01-01

    The high temperature conversion (HTC) technique using an elemental analyzer with a glassy carbon tube and filling (temperature conversion/elemental analysis, TC/EA) is a widely used method for hydrogen isotopic analysis of water and many solid and liquid organic samples with analysis by

  13. Bar-coded pyrosequencing reveals shared bacterial community properties along the temperature gradients of two alkaline hot springs in Yellowstone National Park.

    Science.gov (United States)

    Miller, Scott R; Strong, Aaron L; Jones, Kenneth L; Ungerer, Mark C

    2009-07-01

    An understanding of how communities are organized is a fundamental goal of ecology but one which has historically been elusive for microbial systems. We used a bar-coded pyrosequencing approach targeting the V3 region of the bacterial small-subunit rRNA gene to address the factors that structure communities along the thermal gradients of two alkaline hot springs in the Lower Geyser Basin of Yellowstone National Park. The filtered data set included a total of nearly 34,000 sequences from 39 environmental samples. Each was assigned to one of 391 operational taxonomic units (OTUs) identified by their unique V3 sequence signatures. Although the two hot springs differed in their OTU compositions, community resemblance and diversity changed with strikingly similar dynamics along the two outflow channels. Two lines of evidence suggest that these community properties are controlled primarily by environmental temperature. First, community resemblance decayed exponentially with increasing differences in temperature between samples but was only weakly correlated with physical distance. Second, diversity decreased with increasing temperature at the same rate along both gradients but was uncorrelated with other measured environmental variables. This study also provides novel insights into the nature of the ecological interactions among important taxa in these communities. A strong negative association was observed between cyanobacteria and the Chloroflexi, which together accounted for approximately 70% of the sequences sampled. This pattern contradicts the longstanding hypothesis that coadapted lineages of these bacteria maintain tightly cooccurring distributions along these gradients as a result of a producer-consumer relationship. We propose that they instead compete for some limiting resource(s).

  14. Gradient-index POF without dopants: how the optical properties can be controlled by sole temperature treatment

    Science.gov (United States)

    Bunge, C.-A.; Schüppert, M.; Beckers, M.; Stepniak, G.; Vad, T.; Seide, G.; Gries, T.

    2016-09-01

    In this paper we present a novel melt-spinning fabrication process for graded-index polymer optical fibers that completely avoids additional dopants for the formation of the refractive-index profile. In the presented process the meltspun fiber is rapidly cooled down so that the inner and outer parts of the fiber solidify at different speeds resulting in a density gradient. This density variation leads to a refractive-index profile without any further dopants. We present achieved results for fibers made of PMMA, and also first preliminary results for bio polymers such as TPU.

  15. An attempt to minimize the temperature gradient along a plug-flow methane/steam reforming reactor by adopting locally controlled heating zones

    Science.gov (United States)

    Mozdzierz, M.; Brus, G.; Sciazko, A.; Komatsu, Y.; Kimijima, S.; Szmyd, J. S.

    2014-08-01

    Plug flow reactors are very common in the chemical process industry, including methane/steam reforming applications. Their operation presents many challenges, such as a strong dependence of temperature and composition distribution on the inlet conditions. The strongly endothermic methane/steam reforming reaction might result in a temperature drop at the inlet of the reactor and consequently the occurrence of large temperature gradients. The strongly non-uniform temperature distribution due to endothermic chemical reaction can have tremendous consequences on the operation of the reactor, such as catalyst degradation, undesired side reactions and thermal stresses. To avoid such unfavorable conditions, thermal management of the reactor becomes an important issue. To carry out thermal management properly, detailed modeling and corresponding numerical analyses of the phenomena occurring inside the reforming system is required. This paper presents experimental and numerical studies on the methane/steam reforming process inside a plug-flow reactor. To optimize the reforming reactors, detailed data about the entire reforming process is required. In this study the kinetics of methane/steam reforming on the Ni/YSZ catalyst was experimentally investigated. Measurements including different thermal boundary conditions, the fuel flow rate and the steam- to-methane ratios were performed. The reforming rate equation derived from experimental data was used in the numerical model to predict gas composition and temperature distribution along the steam-reforming reactor. Finally, an attempt was made to control the temperature distribution by adopting locally controlled heating zones.

  16. Seasonal variations in groundwater upwelling zones in a Danish lowland stream analyzed using Distributed Temperature Sensing (DTS)

    DEFF Research Database (Denmark)

    Matheswaran, Karthikeyan; Blemmer, Morten; Rosbjerg, Dan

    2014-01-01

    The distribution of groundwater inflows in a stream reach plays a major role in controlling the stream temperature, a vital component shaping the riverine ecosystem. In this study, the Distributed Temperature Sensing (DTS) system was installed in a small Danish lowland stream, Elverdamsåen, to as...

  17. Marginal stability, characteristic frequencies, and growth rates of gradient drift modes in partially magnetized plasmas with finite electron temperature

    Science.gov (United States)

    Lakhin, V. P.; Ilgisonis, V. I.; Smolyakov, A. I.; Sorokina, E. A.; Marusov, N. A.

    2018-01-01

    The detailed analysis of stability of azimuthal oscillations in partially magnetized plasmas with crossed electric and magnetic fields is presented. The instabilities are driven by the transverse electron current which, in general, is due to a combination of E ×B and electron diamagnetic drifts. Marginal stability boundary is determined for a wide range of the equilibrium plasma parameters. It is shown that in some regimes near the instability threshold, only the low-frequency long-wavelength oscillations are unstable, while the short-wavelength high-frequency modes are stabilized by the finite Larmor radius effects. Without such stabilization, the high-frequency modes have much larger growth rates and dominate. A new regime of the instability driven exclusively by the magnetic field gradient is identified. Such instability takes place in the region of the weak electric field and for relatively large gradients of plasma density ( ρs/ln>1 , where ρs is the ion-sound Larmor radius and ln is the scale length of plasma density inhomogeneity).

  18. Local melting/solidification during peritectic solidification in a steep temperature gradient: analysis of a directionally solidified Al-25at%Ni

    Science.gov (United States)

    Liu, Dongmei; Li, Xinzhong; Su, Yanqing; Rettenmayr, Markus; Guo, Jingjie; Fu, Hengzhi

    2014-09-01

    Melting of primary Al3Ni2 phase and solidification of Al3Ni peritectic phase during directional solidification of an Al-25at%Ni peritectic alloy have been investigated. In a steep temperature gradient of up to 50 K/mm and at a pulling rate of 20 μm/s, an incomplete coverage of peritectic Al3Ni phase on the surface of the primary Al3Ni2 phase has been observed. Below the peritectic temperature in the presence of the incomplete coverage, melting of primary Al3Ni2 on the one side and solidification to the Al3Ni peritectic phase on the other side proceed swiftly via diffusion through the interphase liquid layer. Theoretical calculations based on an incomplete-coverage-related melting/solidification model are in close agreement with the experimental measurements.

  19. Performance of a high-work, low-aspect-ratio turbine stator tested with a realistic inlet radial temperature gradient

    Science.gov (United States)

    Stabe, Roy G.; Schwab, John R.

    1991-01-01

    A 0.767-scale model of a turbine stator designed for the core of a high-bypass-ratio aircraft engine was tested with uniform inlet conditions and with an inlet radial temperature profile simulating engine conditions. The principal measurements were radial and circumferential surveys of stator-exit total temperature, total pressure, and flow angle. The stator-exit flow field was also computed by using a three-dimensional Navier-Stokes solver. Other than temperature, there were no apparent differences in performance due to the inlet conditions. The computed results compared quite well with the experimental results.

  20. Temperature-assisted solute focusing with sequential trap/release zones in isocratic and gradient capillary liquid chromatography: Simulation and experiment

    Science.gov (United States)

    Groskreutz, Stephen R.; Weber, Stephen G.

    2016-01-01

    In this work we characterize the development of a method to enhance temperature-assisted on-column solute focusing (TASF) called two-stage TASF. A new instrument was built to implement two-stage TASF consisting of a linear array of three independent, electronically controlled Peltier devices (thermoelectric coolers, TECs). Samples are loaded onto the chromatographic column with the first two TECs, TEC A and TEC B, cold. In the two-stage TASF approach TECs A and B are cooled during injection. TEC A is heated following sample loading. At some time following TEC A’s temperature rise, TEC B’s temperature is increased from the focusing temperature to a temperature matching that of TEC A. Injection bands are focused twice on-column, first on the initial TEC, e.g. single-stage TASF, then refocused on the second, cold TEC. Our goal is to understand the two-stage TASF approach in detail. We have developed a simple yet powerful digital simulation procedure to model the effect of changing temperature in the two focusing zones on retention, band shape and band spreading. The simulation can predict experimental chromatograms resulting from spatial and temporal temperature programs in combination with isocratic and solvent gradient elution. To assess the two-stage TASF method and the accuracy of the simulation well characterized solutes are needed. Thus, retention factors were measured at six temperatures (25–75 °C) at each of twelve mobile phases compositions (0.05–0.60 acetonitrile/water) for homologs of n-alkyl hydroxylbenzoate esters and n-alkyl p-hydroxyphenones. Simulations accurately reflect experimental results in showing that the two-stage approach improves separation quality. For example, two-stage TASF increased sensitivity for a low retention solute by a factor of 2.2 relative to single-stage TASF and 8.8 relative to isothermal conditions using isocratic elution. Gradient elution results for two-stage TASF were more encouraging. Application of two-stage TASF

  1. Continuous gradient temperature Raman spectroscopy and differential scanning calorimetry of N-3DPA and DHA from -100 to 10°C.

    Science.gov (United States)

    Broadhurst, C Leigh; Schmidt, Walter F; Nguyen, Julie K; Qin, Jianwei; Chao, Kuanglin; Aubuchon, Steven R; Kim, Moon S

    2017-04-01

    Docosahexaenoic acid (DHA, 22:6n-3) is exclusively utilized in fast signal processing tissues such as retinal, neural and cardiac. N-3 docosapentaenoic acid (n-3DPA, 22:5n-3), with just one less double bond, is also found in the marine food chain yet cannot substitute for DHA. Gradient temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near and at phase transitions. Herein we apply GTRS and both conventional and modulated DSC to n-3DPA and DHA from -100 to 20°C. Three-dimensional data arrays with 0.2°C increments and first derivatives allowed complete assignment of solid, liquid and transition state vibrational modes. Melting temperatures n-3DPA (-45°C) and DHA (-46°C) are similar and show evidence for solid-state phase transitions not seen in n-6DPA (-27°C melt). The C6H2 site is an elastic marker for temperature perturbation of all three lipids, each of which has a distinct three dimensional structure. N-3 DPA shows the spectroscopic signature of saturated fatty acids from C1 to C6. DHA does not have three aliphatic carbons in sequence; n-6DPA does but they occur at the methyl end, and do not yield the characteristic signal. DHA appears to have uniform twisting from C6H2 to C12H2 to C18H2 whereas n-6DPA bends from C12 to C18, centered at C15H2. For n-3DPA, twisting is centered at C6H2 adjacent to the C2-C3-C4-C5 aliphatic moiety. These molecular sites are the most elastic in the solid phase and during premelting. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. [Variability of soil water soluble organic carbon content and its response to temperature change in green spaces along urban-to-rural gradient of Nanchang, China].

    Science.gov (United States)

    Li, Pei-qing; Fang, Xiang-min; Chen, Fu-sheng; Wang, Fang-chao; Yu, Jin-rong; Wan, Song-ze; Li, Zu-yao

    2015-11-01

    Topsoil of green space including typical forest, shrub and grassland were collected to measure their water soluble organic carbon ( WSOC) before and after incubation of 30 days at 5, 15, 25, 35 and, 45 °C. The results showed the average values of WSOC were higher in urban than in rural green spaces, but the percentage of WSOC to total organic carbon (TOC) showed an opposite trend. No significant changes were found among the three green space types in WSOC and WSOC/TOC. Response of WSOC in green space to incubation temperature was generally highest in urban sites, followed by suburban sites, and lowest in rural sites at the incubation temperature of 5 °C, but showed an opposite trend at the temperature of 45 °C. Response coefficient of WSOC to temperature change was lower in forest and shrub than in grassland, but increased along the urban-rural gradient. Further analysis showed that WSOC positively correlated with TOC, total nitrogen and available phosphorus, and the response coefficient of WSOC to temperature change negatively correlated with available phosphorus. In summary, exogenous substances input might lead to the accumulation of WSOC in urban green space, however, urban environment was helpful to maintain the stability of WSOC, which might be due to the enrichment of available phosphorus in urban sites.

  3. Magic angle spinning NMR below 6 K with a computational fluid dynamics analysis of fluid flow and temperature gradients.

    Science.gov (United States)

    Sesti, Erika L; Alaniva, Nicholas; Rand, Peter W; Choi, Eric J; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Barnes, Alexander B

    2017-11-11

    We report magic angle spinning (MAS) up to 8.5 kHz with a sample temperature below 6 K using liquid helium as a variable temperature fluid. Cross polarization 13C NMR spectra exhibit exquisite sensitivity with a single transient. Remarkably, 1H saturation recovery experiments show a 1H T1 of 21 s with MAS below 6 K in the presence of trityl radicals in a glassy matrix. Leveraging the thermal spin polarization available at 4.2 K versus 298 K should result in 71 times higher signal intensity. Taking the 1H longitudinal relaxation into account, signal averaging times are therefore predicted to be expedited by a factor of >500. Computer assisted design (CAD) and finite element analysis were employed in both the design and diagnostic stages of this cryogenic MAS technology development. Computational fluid dynamics (CFD) models describing temperature gradients and fluid flow are presented. The CFD models bearing and drive gas maintained at 100 K, while a colder helium variable temperature fluid stream cools the center of a zirconia rotor. Results from the CFD were used to optimize the helium exhaust path and determine the sample temperature. This novel cryogenic experimental platform will be integrated with pulsed dynamic nuclear polarization and electron decoupling to interrogate biomolecular structure within intact human cells. Copyright © 2017. Published by Elsevier Inc.

  4. The Radial Temperature Gradient in the Gleeble Hot-Torsion Test and Its Effect on the Interpretation (Postprint)

    Science.gov (United States)

    2017-08-21

    identical to that developed in a sample uniformly preheated to a temperature corresponding to that experienced at a fractional radial location of 0.8 in...partial differential equations describing the voltage drop across the specimen, current density, and heat conduction (including a heat-generation term...of c¢ volume fraction with temperature (Figure 1).[24] B. Experimental Procedures Two types of direct-resistance heating trials were performed with

  5. Metabolic cold adaptation and aerobic performance of blue mussels (Mytilus edulis) along a temperature gradient into the High Arctic region

    DEFF Research Database (Denmark)

    Thyrring, Jakob; Rysgaard, Søren; Blicher, Martin

    2015-01-01

    populations at different temperatures. Standard metabolic rates (SMR) and active metabolic rates (AMR) were measured for each population, and absolute (AMR − SMR) and factorial (AMR/SMR) scopes were calculated. Blue mussels from the temperate population had the lowest Q10 (= 1.8) and the largest thermal...... and plasticity of blue mussels across latitudes spanning from 56 to 77ºN. This indicates that low ocean temperature per se does not constrain metabolic activity of Mytilus in the Arctic; rather, we speculate that maturation of reproductive tissues, larval supply and annual energy budgets are the most relevant...

  6. HIGH-TEMPERATURE EXAFS EXPERIMENTS ON LIQUID KPB ALLOYS ANALYZED WITH THE REVERSE MONTE-CARLO METHOD

    NARCIS (Netherlands)

    BRAS, W; XU, R; WICKS, JD; VANDERHORST, F; OVERSLUIZEN, M; MCGREEVY, RL; VANDERLUGT, W

    1994-01-01

    A new sample chamber has been designed which allows high temperature Extended X-ray Absorption Fine Structure (EXAFS) experiments on metallic melts which offer a number of special experimental problems: they are highly corrosive, have high vapour pressures and strongly absorb X-rays. The EXAFS

  7. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    NARCIS (Netherlands)

    van de Poll, W.H.; Kulk, G.; Timmermans, K.R.; Brussaard, C.P.D.; van der Woerd, H.J.; Kehoe, M.J.; Mojica, K.D.A.; Visser, R.J.W.; Rozema, P.D.; Buma, A.G.J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63° N in the northeast Atlantic

  8. Phytoplankton chlorophyll a biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

    NARCIS (Netherlands)

    van de Poll, W. H.; Kulk, G.; Timmermans, K. R.; Brussaard, C. P. D.; van der Woerd, H. J.; Kehoe, M. J.; Mojica, K. D. A.; Visser, R. J. W.; Rozema, P. D.; Buma, A. G. J.

    2013-01-01

    Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63 degrees N in the northeast

  9. Plasticity in activity and latency to explore differs between juvenile Atlantic cod Gadus morhua across a temperature gradient.

    Science.gov (United States)

    Reynisson, H; Ólafsdóttir, G Á

    2018-01-01

    In the current study activity and latency to explore, as well as the correlation of these traits, were examined in individually marked juvenile Gadus morhua at 7, 10 and 13° C. It was concluded that individual rank order of both traits was maintained across temperature but that the level of change differed between individuals. © 2017 The Fisheries Society of the British Isles.

  10. A novel temperature-gradient Na±β-alumina solid electrolyte based SOx gas sensor without gaseous reference electrode

    DEFF Research Database (Denmark)

    Rao, N.; Bleek, C.M. Van den; Schoonman, J.

    1992-01-01

    An electrochemical SOx ps sensor with a tubular Na+-beta"-alumina solid electrolyte has been fabricated and tested under non-isothermal conditions. The temperature difference between the reference and working electrode of the sensor cell is about 100-degrees-C, which causes a serious deviation...

  11. Complex terrain alters temperature and moisture limitations of forest soil respiration across a semiarid to subalpine gradient

    Science.gov (United States)

    Berryman, Erin Michele; Barnard, H.R.; Adams, H.R.; Burns, M.A.; Gallo, E.; Brooks, P.D.

    2015-01-01

    Forest soil respiration is a major carbon (C) flux that is characterized by significant variability in space and time. We quantified growing season soil respiration during both a drought year and a nondrought year across a complex landscape to identify how landscape and climate interact to control soil respiration. We asked the following questions: (1) How does soil respiration vary across the catchments due to terrain-induced variability in moisture availability and temperature? (2) Does the relative importance of moisture versus temperature limitation of respiration vary across space and time? And (3) what terrain elements are important for dictating the pattern of soil respiration and its controls? Moisture superseded temperature in explaining watershed respiration patterns, with wetter yet cooler areas higher up and on north facing slopes yielding greater soil respiration than lower and south facing areas. Wetter subalpine forests had reduced moisture limitation in favor of greater seasonal temperature limitation, and the reverse was true for low-elevation semiarid forests. Coincident climate poorly predicted soil respiration in the montane transition zone; however, antecedent precipitation from the prior 10 days provided additional explanatory power. A seasonal trend in respiration remained after accounting for microclimate effects, suggesting that local climate alone may not adequately predict seasonal variability in soil respiration in montane forests. Soil respiration climate controls were more strongly related to topography during the drought year highlighting the importance of landscape complexity in ecosystem response to drought.

  12. Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

    Directory of Open Access Journals (Sweden)

    S. Krause

    2012-06-01

    Full Text Available This paper investigates the patterns and controls of aquifer–river exchange in a fast-flowing lowland river by the conjunctive use of streambed temperature anomalies identified with Fibre-optic Distributed Temperature Sensing (FO-DTS and observations of vertical hydraulic gradients (VHG.

    FO-DTS temperature traces along this lowland river reach reveal discrete patterns with "cold spots" indicating groundwater up-welling. In contrast to previous studies using FO-DTS for investigation of groundwater–surface water exchange, the fibre-optic cable in this study was buried in the streambed sediments, ensuring clear signals despite fast flow and high discharges. During the observed summer baseflow period, streambed temperatures in groundwater up-welling locations were found to be up to 1.5 °C lower than ambient streambed temperatures. Due to the high river flows, the cold spots were sharp and distinctly localized without measurable impact on down-stream surface water temperature.

    VHG patterns along the stream reach were highly variable in space, revealing strong differences even at small scales. VHG patterns alone are indicators of both, structural heterogeneity of the stream bed as well as of the spatial heterogeneity of the groundwater–surface water exchange fluxes and are thus not conclusive in their interpretation. However, in combination with the high spatial resolution FO-DTS data we were able to separate these two influences and clearly identify locations of enhanced exchange, while also obtaining information on the complex small-scale streambed transmissivity patterns responsible for the very discrete exchange patterns. The validation of the combined VHG and FO-DTS approach provides an effective strategy for analysing drivers and controls of groundwater–surface water exchange, with implications for the quantification of biogeochemical cycling and contaminant transport at aquifer–river interfaces.

  13. The influence of temperature calibration on the OC–EC results from a dual-optics thermal carbon analyzer

    Science.gov (United States)

    The Sunset Laboratory Dual-Optical Carbonaceous Analyzer that simultaneously measures transmission and reflectance signals is widely used in thermal-optical analysis of particulate matter samples. Most often this instrument is used to measure total carbon (TC), organic carbon (O...

  14. Enrichment of magnetic particles using temperature and magnetic field gradients induced by benchtop fabricated micro-electromagnets.

    Science.gov (United States)

    Hosseini, A; Philpott, D N; Soleymani, L

    2017-11-21

    The active transport of analytes inside biosensing systems is important for reducing the response time and enhancing the limit-of-detection of these systems. Due to the ease of functionalization with bio-recognition agents and manipulation with magnetic fields, magnetic particles are widely used for active and directed transport of biological analytes. On-chip active electromagnets are ideally suited for manipulating magnetic particles in an automated and miniaturized fashion inside biosensing systems. Unfortunately, the magnetic force exerted by these devices decays rapidly as we move away from the device edges, and increasing the generated force to the levels necessary for particle manipulation requires a parallel increase in the applied current and the resultant Joule heating. In this paper, we designed a study to understand the combined role of thermal and magnetic forces on the movement of magnetic particles in order to extend the interaction distance of on-chip magnetic devices beyond the device edges. For this purpose, we used a rapid prototyping method to create an active/passive on-chip electromagnet with a micro/nano-structured active layer and a patterned ferromagnetic passive layer. We demonstrated that the measured terminal velocities of particles positioned near the electromagnet edge (∼5.5 μm) closely reflect the values obtained by multi-physics modelling. Interestingly, we observed a two orders of magnitude deviation between the experimental and modelling results for the terminal velocities of particles far from the electromagnet edge (∼55.5 μm). Heat modelling of the system using experimentally-measured thermal gradients indicates that this discrepancy is related to the enhanced fluid movement caused by thermal forces. This study enables the rational design of thermo-magnetic systems for thermally driving and magnetically capturing particles that are positioned at distances tens to hundreds of microns away from the edges of on-chip magnetic

  15. Predicting the Impact of Temperature Change on the Future Distribution of Maize Stem Borers and Their Natural Enemies along East African Mountain Gradients Using Phenology Models.

    Directory of Open Access Journals (Sweden)

    Sizah Mwalusepo

    Full Text Available Lepidopteran stem borers are among the most important pests of maize in East Africa. The objective of the present study was to predict the impact of temperature change on the distribution and abundance of the crambid Chilo partellus, the noctuid Busseola fusca, and their larval parasitoids Cotesia flavipes and Cotesia sesamiae at local scale along Kilimanjaro and Taita Hills gradients in Tanzania and Kenya, respectively. Temperature-dependent phenology models of pests and parasitoids were used in a geographic information system for mapping. The three risk indices namely establishment, generation, and activity indices were computed using current temperature data record from local weather stations and future (i.e., 2055 climatic condition based on downscaled climate change data from the AFRICLIM database. The calculations were carried out using index interpolator, a sub-module of the Insect Life Cycle Modeling (ILCYM software. Thin plate algorithm was used for interpolation of the indices. Our study confirmed that temperature was a key factor explaining the distribution of stem borers and their natural enemies but other climatic factors and factors related to the top-down regulation of pests by parasitoids (host-parasitoid synchrony also played a role. Results based on temperature only indicated a worsening of stem borer impact on maize production along the two East African mountain gradients studied. This was attributed to three main changes occurring simultaneously: (1 range expansion of the lowland species C. partellus in areas above 1200 m.a.s.l.; (2 increase of the number of pest generations across all altitudes, thus by 2055 damage by both pests will increase in the most productive maize zones of both transects; (3 disruption of the geographical distribution of pests and their larval parasitoids will cause an improvement of biological control at altitude below 1200 m.a.s.l. and a deterioration above 1200 m.a.s.l. The predicted increase in

  16. Predicting the Impact of Temperature Change on the Future Distribution of Maize Stem Borers and Their Natural Enemies along East African Mountain Gradients Using Phenology Models.

    Science.gov (United States)

    Mwalusepo, Sizah; Tonnang, Henri E Z; Massawe, Estomih S; Okuku, Gerphas O; Khadioli, Nancy; Johansson, Tino; Calatayud, Paul-André; Le Ru, Bruno Pierre

    2015-01-01

    Lepidopteran stem borers are among the most important pests of maize in East Africa. The objective of the present study was to predict the impact of temperature change on the distribution and abundance of the crambid Chilo partellus, the noctuid Busseola fusca, and their larval parasitoids Cotesia flavipes and Cotesia sesamiae at local scale along Kilimanjaro and Taita Hills gradients in Tanzania and Kenya, respectively. Temperature-dependent phenology models of pests and parasitoids were used in a geographic information system for mapping. The three risk indices namely establishment, generation, and activity indices were computed using current temperature data record from local weather stations and future (i.e., 2055) climatic condition based on downscaled climate change data from the AFRICLIM database. The calculations were carried out using index interpolator, a sub-module of the Insect Life Cycle Modeling (ILCYM) software. Thin plate algorithm was used for interpolation of the indices. Our study confirmed that temperature was a key factor explaining the distribution of stem borers and their natural enemies but other climatic factors and factors related to the top-down regulation of pests by parasitoids (host-parasitoid synchrony) also played a role. Results based on temperature only indicated a worsening of stem borer impact on maize production along the two East African mountain gradients studied. This was attributed to three main changes occurring simultaneously: (1) range expansion of the lowland species C. partellus in areas above 1200 m.a.s.l.; (2) increase of the number of pest generations across all altitudes, thus by 2055 damage by both pests will increase in the most productive maize zones of both transects; (3) disruption of the geographical distribution of pests and their larval parasitoids will cause an improvement of biological control at altitude below 1200 m.a.s.l. and a deterioration above 1200 m.a.s.l. The predicted increase in pest activity

  17. Design and production of efficient current leads for 1500-A, 50-Hz service in a 77-4 K temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Balachandran, U.; Youngdahl, C.A.; Lanagan, M.T. [and others

    1994-10-01

    Two arrays of BSCCO 2223 bars were designed and produced for use in current leads for a power utility fault-current limiter operating at 4 K. Each conduction-cooled array, consisting of four parallel bars arranged within a 100-mm-diameter boundary, delivered 1,500 A peak, 50-Hz AC through a 77-4 K temperature gradient while dissipating < 0.2 W. The sinter-forged bars displayed DC critical current densities of 950--1,300 A/cm{sup 2} at 77 K and > 5,000 A/cm{sup 2} at 4 K. Magnetic field sensitivity was relatively low. Thermal conductivity tests showed values higher than literature values for polycrystalline BSCCO 2223 made by other processes.

  18. Analyzing land surface temperature variations during Fogo Island (Cape Verde) 2014-2015 eruption with Landsat 8 images

    Science.gov (United States)

    Vieira, D.; Teodoro, A.; Gomes, A.

    2016-10-01

    Land Surface Temperature (LST) is an important parameter related to land surface processes that changes continuously through time. Assessing its dynamics during a volcanic eruption has both environmental and socio-economical interest. Lava flows and other volcanic materials produced and deposited throughout an eruption transform the landscape, contributing to its heterogeneity and altering LST measurements. This paper aims to assess variations of satellite-derived LST and to detect patterns during the latest Fogo Island (Cape Verde) eruption, extending from November 2014 through February 2015. LST data was obtained through four processed Landsat 8 images, focused on the caldera where Pico do Fogo volcano sits. QGIS' plugin Semi-Automatic Classification was used in order to apply atmospheric corrections and radiometric calibrations. The algorithm used to retrieve LST values is a single-channel method, in which emissivity values are known. The absence of in situ measurements is compensated by the use of MODIS sensor-derived LST data, used to compare with Landsat retrieved measurements. LST data analysis shows as expected that the highest LST values are located inside the caldera. High temperature values were also founded on the south-facing flank of the caldera. Although spatial patterns observed on the retrieved data remained roughly the same during the time period considered, temperature values changed throughout the area and over time, as it was also expected. LST values followed the eruption dynamic experiencing a growth followed by a decline. Moreover, it seems possible to recognize areas affected by lava flows of previous eruptions, due to well-defined LST spatial patterns.

  19. Living in biological soil crust communities of African deserts—Physiological traits of green algal Klebsormidium species (Streptophyta) to cope with desiccation, light and temperature gradients

    Science.gov (United States)

    Karsten, Ulf; Herburger, Klaus; Holzinger, Andreas

    2015-01-01

    Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient. All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions. PMID:26422081

  20. Analyzing the Effects of Climate Change on Sea Surface Temperature in Monitoring Coral Reef Health in the Florida Keys Using Sea Surface Temperature Data

    Science.gov (United States)

    Jones, Jason; Burbank, Renane; Billiot, Amanda; Schultz, Logan

    2011-01-01

    This presentation discusses use of 4 kilometer satellite-based sea surface temperature (SST) data to monitor and assess coral reef areas of the Florida Keys. There are growing concerns about the impacts of climate change on coral reef systems throughout the world. Satellite remote sensing technology is being used for monitoring coral reef areas with the goal of understanding the climatic and oceanic changes that can lead to coral bleaching events. Elevated SST is a well-documented cause of coral bleaching events. Some coral monitoring studies have used 50 km data from the Advanced Very High Resolution Radiometer (AVHRR) to study the relationships of sea surface temperature anomalies to bleaching events. In partnership with NOAA's Office of National Marine Sanctuaries and the University of South Florida's Institute for Marine Remote Sensing, this project utilized higher resolution SST data from the Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) and AVHRR. SST data for 2000-2010 was employed to compute sea surface temperature anomalies within the study area. The 4 km SST anomaly products enabled visualization of SST levels for known coral bleaching events from 2000-2010.

  1. Calibration of a miniaturized retarding field analyzer for low-temperature plasmas: geometrical transparency and collisional effects

    Energy Technology Data Exchange (ETDEWEB)

    Baloniak, Tim; Reuter, Ruediger; Floetgen, Christoph; Von Keudell, Achim [Research Group Reactive Plasmas, Ruhr-Universitaet Bochum, 44780 Bochum (Germany)

    2010-02-10

    Retarding field analyzers (RFAs) are important diagnostics to measure fluxes and energies of ions impinging onto the wall of a plasma reactor. Any quantitative use of the data requires a proper calibration, which is here performed for a miniaturized RFA. The calibration accounts for the transparencies of the RFA grids as well as for collisions inside the RFA. An analytical model is derived which covers both geometrical and collisional effects. The model is calibrated and experimentally verified using a Langmuir probe. We find that the transparency of an RFA is a random variable which depends on the individual alignment of the RFA grids. Collisions inside the RFA limit the ion current transfer through the RFA at higher pressures. A simple method is presented which allows one to remove these artefacts from the RFA data and to obtain quantitative ion velocity distributions.

  2. Analyzing the temperature control of steam purging of 660mw ultra-supercritical once-through boiler with pressure-reducing method

    Science.gov (United States)

    Wu, Ying; Zhong, Yong-lu; Liu, Fa-sheng; Chen, Wen; Gui, Liang-ming; Xia, Yong-jun; Wan, Zhong-hai; Yan, Tao

    2017-11-01

    This paper generally introduced the process of steam purging of the ultra-supercritical once-through boiler of Jiangxi Xinchang 2×660MW Power Plant with the pressure-reducing method. In this paper, the key-points of steam temperature control was importantly analyzed and summarized. The success experience can provide the reference for preventing steam overtemp of the similar ultra-supercritical once-through boilers with pressure-reducing method.

  3. A selective and sensitive optical sensor for dissolved ammonia detection via agglomeration of fluorescent Ag nanoclusters and temperature gradient headspace single drop microextraction.

    Science.gov (United States)

    Dong, Jiang Xue; Gao, Zhong Feng; Zhang, Ying; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2017-05-15

    In this paper, a simple sensor platform is presented for highly selective and sensitive detection of dissolved ammonia in aqueous solutions without pretreatment based on temperature gradient headspace single drop microextraction (HS-SDME) technique, and fluorescence and UV-vis spectrophotometry are utilized with the Ag nanoclusters (Ag NCs) functioned by citrate and glutathione as the probe. The sensing mechanism is based on the volatility of ammonia gas and the active response of Ag NCs to pH change caused by the introduction of ammonia. High pH can make the Ag NCs agglomerate and lead to the obvious decrease of fluorescence intensity and absorbance of Ag NCs solution. Moreover, the presented method exhibits a remarkably high selectivity toward dissolved ammonia over most of inorganic ions and amino acid, and shows a good linear range of 10-350μM (0.14-4.9mgNL-1) with a low detection limit of 336nM (4.70μgNL-1) at a signal-to-noise ratio of 3. In addition, the practical applications of the sensor have been successfully demonstrated by detecting dissolved ammonia in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. A Reconstruction of Sea Surface Temperature Gradients and an Assessment of the Suspected Presence of Continental Ice During the Cold Mid-Paleocene (61-57 Ma)

    Science.gov (United States)

    Bijl, P.; Cramwinckel, M.; Frieling, J.; Peterse, F.

    2016-12-01

    The early Eocene `hothouse' climate experienced paratropical vegetation on high latitudes and high (>1100 ppmv) atmospheric CO2 concentrations. It is generally considered as analogous to the endmember climate state should we use up all available fossil fuels. However, we do not know exactly through which processes this long-term warm episode came to be nor do we understand what the initial climate state was at the onset of this long-term climate. Deep-sea warming towards early Eocene hothouse conditions started in the mid-Paleocene, ending a 2 Myr time interval of relatively cold deep ocean temperatures. Reconstructed pCO2 concentrations of the mid-Paleocene seem to have been close to those of present-day, although data is scarce. The mid-Paleocene is notoriously sparsely represented in shelf sedimentary records, as most records show a conspicuous hiatus between 58 and 60 Mys. This gives the suggestion of a major global low in sea level, which is inconsistent with estimates of global ocean spreading rates, which suggest a relatively high sea level on long time scales for the Cretaceous-early Paleogene. The cold deep-sea temperatures, the conspicuously low sea level and low atmospheric CO2 during the mid-Paleocene have stimulated suggestions of the presence of major ice sheets on the poles, yet the absence of any trace for continental ice, either direct ice-proximal evidence or from benthic foraminiferal oxygen isotope records, calls the presence of such ice sheets into question. I will present a number of high resolution sea surface temperature records (based mostly on organic geochemical biomarker proxies) which start to reveal a latitudinal temperature gradient for the mid-Paleocene. Reconstructions come from shelf sediments from Tasmania, Australia, Tanzania, Tropical Atlantic Ocean, New Jersey). With these new records, I put Paleogene climate evolution into context. I will further present a review of shelf sedimentary records across the mid-paleocene to assess

  5. Patterns of structural and defense investments in fine roots of Scots pine (Pinus sylvestris L.) across a strong temperature and latitudinal gradient in Europe.

    Science.gov (United States)

    Zadworny, Marcin; McCormack, M Luke; Żytkowiak, Roma; Karolewski, Piotr; Mucha, Joanna; Oleksyn, Jacek

    2017-03-01

    Plant functional traits may be altered as plants adapt to various environmental constraints. Cold, low fertility growing conditions are often associated with root adjustments to increase acquisition of limiting nutrient resources, but they may also result in construction of roots with reduced uptake potential but higher tissue persistence. It is ultimately unclear whether plants produce fine roots of different structure in response to decreasing temperatures and whether these changes represent a trade-off between root function or potential root persistence. We assessed patterns of root construction based on various root morphological, biochemical and defense traits including root diameter, specific root length (SRL), root tissue density (RTD), C:N ratio, phenolic compounds, and number of phellem layers across up to 10 root orders in diverse populations of Scots pine along a 2000-km climatic gradient in Europe. Our results showed that different root traits are related to mean annual temperature (MAT) and expressed a pattern of higher root diameter and lower SRL and RTD in northern sites with lower MAT. Among absorptive roots, we observed a gradual decline in chemical defenses (phenolic compounds) with decreasing MAT. In contrast, decreasing MAT resulted in an increase of structural protection (number of phellem layers) in transport fine roots. This indicated that absorptive roots with high capacity for nutrient uptake, and transport roots with low uptake capacity, were characterized by distinct and contrasting trade-offs. Our observations suggest that diminishing structural and chemical investments into the more distal, absorptive roots in colder climates is consistent with building roots of higher absorptive capacity. At the same time, roots that play a more prominent role in transport of nutrients and water within the root system saw an increase in structural investment, which can increase persistence and reduce long-term costs associated with their frequent

  6. Analyzing the effects of urban expansion on land surface temperature patterns by landscape metrics: a case study of Isfahan city, Iran.

    Science.gov (United States)

    Madanian, Maliheh; Soffianian, Ali Reza; Koupai, Saeid Soltani; Pourmanafi, Saeid; Momeni, Mehdi

    2018-03-03

    Urban expansion can cause extensive changes in land use and land cover (LULC), leading to changes in temperature conditions. Land surface temperature (LST) is one of the key parameters that should be considered in the study of urban temperature conditions. The purpose of this study was, therefore, to investigate the effects of changes in LULC due to the expansion of the city of Isfahan on LST using landscape metrics. To this aim, two Landsat 5 and Landsat 8 images, which had been acquired, respectively, on August 2, 1985, and July 4, 2015, were used. The support vector machine method was then used to classify the images. The results showed that Isfahan city had been encountered with an increase of impervious surfaces; in fact, this class covered 15% of the total area in 1985, while this value had been increased to 30% in 2015. Then LST zoning maps were created, indicating that the bare land and impervious surfaces categories were dominant in high temperature zones, while in the zones where water was present or NDVI was high, LST was low. Then, the landscape metrics in each of the LST zones were analyzed in relation to the LULC changes, showing that LULC changes due to urban expansion changed such landscape properties as the percentage of landscape, patch density, large patch index, and aggregation index. This information could be beneficial for urban planners to monitor and manage changes in the LULC patterns.

  7. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

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

  8. Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under temperature gradient

    Science.gov (United States)

    Zhao, N.; Zhong, Y.; Huang, M. L.; Ma, H. T.; Dong, W.

    2015-08-01

    The growth behavior of intermetallic compounds (IMCs) at the liquid-solid interfaces in Cu/Sn/Cu interconnects during reflow at 250 °C and 280 °C on a hot plate was investigated. Being different from the symmetrical growth during isothermal aging, the interfacial IMCs showed clearly asymmetrical growth during reflow, i.e., the growth of Cu6Sn5 IMC at the cold end was significantly enhanced while that of Cu3Sn IMC was hindered especially at the hot end. It was found that the temperature gradient had caused the mass migration of Cu atoms from the hot end toward the cold end, resulting in sufficient Cu atomic flux for interfacial reaction at the cold end while inadequate Cu atomic flux at the hot end. The growth mechanism was considered as reaction/thermomigration-controlled at the cold end and grain boundary diffusion/thermomigration-controlled at the hot end. A growth model was established to explain the growth kinetics of the Cu6Sn5 IMC at both cold and hot ends. The molar heat of transport of Cu atoms in molten Sn was calculated as + 11.12 kJ/mol at 250 °C and + 14.65 kJ/mol at 280 °C. The corresponding driving force of thermomigration in molten Sn was estimated as 4.82 × 10-19 N and 6.80 × 10-19 N.

  9. Novel, cyclic heat dissipation method for the correction of natural temperature gradients in sap flow measurements. Part 1. Theory and application.

    Science.gov (United States)

    Lubczynski, Maciek W; Chavarro-Rincon, Diana; Roy, Jean

    2012-07-01

    Natural temperature gradient (NTG) can be a significant problem in thermal sap flow measurements, particularly in dry environments with sparse vegetation. To resolve this problem, we propose a novel correction method called cyclic heat dissipation (CHD) in its thermal dissipation probe (TDP) application. The CHD method is based on cyclic, switching ON/OFF power schema measurements and a three-exponential model, extrapolating measured signal to steady state thermal equilibrium. The extrapolated signal OFF represents NTG, whereas the extrapolated signal ON represents standard TDP signal, biased by NTG. Therefore, subtraction of the OFF signal from the ON signal allows defining the unbiased TDP signal, finally processed according to standard Granier calibration. The in vivo Kalahari measurements were carried out in three steps on four different tree species, first as NTG, then as standard TDP and finally in CHD mode, each step for ∼1-2 days. Afterwards, each tree was separated from its stem following modified Roberts' (1977) procedure, and CHD verification was applied. The typical NTG varying from ∼0.5 °C during night-time to -1 °C during day-time, after CHD correction, resulted in significant reduction of sap flux densities (J(p)) as compared with the standard TDP, particularly distinct for low J(p). The verification of the CHD method indicated ∼20% agreement with the reference method, largely dependent on the sapwood area estimate. The proposed CHD method offers the following advantages: (i) in contrast to any other NTG correction method, it removes NTG bias from the measured signal by using in situ, extrapolated to thermal equilibrium signal; (ii) it does not need any specific calibration making use of the standard Granier calibration; (iii) it provides a physical background to the proposed NTG correction; (iv) it allows for power savings; (v) it is not tied to TDP, and so can be adapted to other thermal methods. In its current state, the CHD data

  10. Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

    Directory of Open Access Journals (Sweden)

    P. Guio

    1998-10-01

    Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

  11. Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

    Directory of Open Access Journals (Sweden)

    P. Guio

    Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.

    Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

  12. Viscosity Measurements of Dilute Poly(2-ethyl-2-oxazoline Aqueous Solutions Near Theta Temperature Analyzed within the Joint Rouse-Zimm Model

    Directory of Open Access Journals (Sweden)

    Jana Tóthová

    2015-01-01

    Full Text Available The steady-state shear viscosity of low-concentrated Poly(2-ethyl-2-oxazoline (PEOX aqueous solutions is measured near the presumed theta temperature using the falling ball viscometry technique. The experimental data are analyzed within the model that joins the Rouse and Zimm bead-spring theories of the polymer dynamics at the theta condition, which means that the polymer coils are considered to be partially permeable to the solvent. The polymer characteristics thus depend on the draining parameter h that is related to the strength of the hydrodynamic interaction between the polymer segments. The Huggins coefficient was found to be 0.418 at the temperature 20°C, as predicted by the theory. This value corresponds to h = 2.92, contrary to the usual assumption of the infinite h. This result indicates that the theta temperature for the PEOX water solutions is 20°C rather than 25°C in the previous studies. The experimental intrinsic viscosity is well described coming from the Arrhenius equation for the shear viscosity.

  13. Determining the ion temperature and energy distribution in a lithium-plasma interaction test stand with a retarding field energy analyzer

    Science.gov (United States)

    Christenson, M.; Stemmley, S.; Jung, S.; Mettler, J.; Sang, X.; Martin, D.; Kalathiparambil, K.; Ruzic, D. N.

    2017-08-01

    The ThermoElectric-driven Liquid-metal plasma-facing Structures (TELS) experiment at the University of Illinois is a gas-puff driven, theta-pinch plasma source that is used as a test stand for off-normal plasma events incident on materials in the edge and divertor regions of a tokamak. The ion temperatures and resulting energy distributions are crucial for understanding how well a TELS pulse can simulate an extreme event in a larger, magnetic confinement device. A retarding field energy analyzer (RFEA) has been constructed for use with such a transient plasma due to its inexpensive and robust nature. The innovation surrounding the use of a control analyzer in conjunction with an actively sampling analyzer is presented and the conditions of RFEA operation are discussed, with results presented demonstrating successful performance under extreme conditions. Such extreme conditions are defined by heat fluxes on the order of 0.8 GW m-2 and on time scales of nearly 200 μs. Measurements from the RFEA indicate two primary features for a typical TELS discharge, following closely with the pre-ionizing coaxial gun discharge characteristics. For the case using the pre-ionization pulse (PiP) and the theta pinch, the measured ion signal showed an ion temperature of 23.3 ± 6.6 eV for the first peak and 17.6 ± 1.9 eV for the second peak. For the case using only the PiP, the measured signal showed an ion temperature of 7.9 ± 1.1 eV for the first peak and 6.6 ± 0.8 eV for the second peak. These differences illustrate the effectiveness of the theta pinch for imparting energy on the ions. This information also highlights the importance of TELS as being one of the few linear pulsed plasma sources whereby moderately energetic ions will strike targets without the need for sample biasing.

  14. Applying Petroleum the Pressure Buildup Well Test Procedure on Thermal Response Test—A Novel Method for Analyzing Temperature Recovery Period

    Directory of Open Access Journals (Sweden)

    Tomislav Kurevija

    2018-02-01

    Full Text Available The theory of Thermal Response Testing (TRT is a well-known part of the sizing process of the geothermal exchange system. Multiple parameters influence the accuracy of effective ground thermal conductivity measurement; like testing time, variable power, climate interferences, groundwater effect, etc. To improve the accuracy of the TRT, we introduced a procedure to additionally analyze falloff temperature decline after the power test. The method is based on a premise of analogy between TRT and petroleum well testing, since the origin of both procedures lies in the diffusivity equation with solutions for heat conduction or pressure analysis during radial flow. Applying pressure build-up test interpretation techniques to borehole heat exchanger testing, greater accuracy could be achieved since ground conductivity could be obtained from this period. Analysis was conducted on a coaxial exchanger with five different power steps, and with both direct and reverse flow regimes. Each test was set with 96 h of classical TRT, followed by 96 h of temperature decline, making for almost 2000 h of cumulative borehole testing. Results showed that the ground conductivity value could vary by as much as 25%, depending on test time, seasonal period and power fluctuations, while the thermal conductivity obtained from the falloff period provided more stable values, with only a 10% value variation.

  15. High-throughput simultaneous determination of plasma water deuterium and 18-oxygen enrichment using a high-temperature conversion elemental analyzer with isotope ratio mass spectrometry.

    Science.gov (United States)

    Richelle, M; Darimont, C; Piguet-Welsch, C; Fay, L B

    2004-01-01

    This paper presents a high-throughput method for the simultaneous determination of deuterium and oxygen-18 (18O) enrichment of water samples isolated from blood. This analytical method enables rapid and simple determination of these enrichments of microgram quantities of water. Water is converted into hydrogen and carbon monoxide gases by the use of a high-temperature conversion elemental analyzer (TC-EA), that are then transferred on-line into the isotope ratio mass spectrometer. Accuracy determined with the standard light Antartic precipitation (SLAP) and Greenland ice sheet precipitation (GISP) is reliable for deuterium and 18O enrichments. The range of linearity is from 0 up to 0.09 atom percent excess (APE, i.e. -78 up to 5725 delta per mil (dpm)) for deuterium enrichment and from 0 up to 0.17 APE (-11 up to 890 dpm) for 18O enrichment. Memory effects do exist but can be avoided by analyzing the biological samples in quintuplet. This method allows the determination of 1440 samples per week, i.e. 288 biological samples per week. Copyright 2004 John Wiley & Sons, Ltd.

  16. Unprecedented quality factors at accelerating gradients up to 45 MVm -1 in niobium superconducting resonators via low temperature nitrogen infusion

    Energy Technology Data Exchange (ETDEWEB)

    Grassellino, A.; Romanenko, A.; Trenikhina, Y.; Checchin, M.; Martinello, M.; Melnychuk, O. S.; Chandrasekaran, S.; Sergatskov, D. A.; Posen, S.; Crawford, A. C.; Aderhold, S.; Bice, D.

    2017-08-14

    We report the finding of new surface treatments that permit to manipulate the niobium resonator nitrogen content in the first few nanometers in a controlled way, and the resonator fundamental Mattis-Bardeen surface resistance and residual resistance accordingly. In particular, we find surface infusion conditions that systematically a) increase the quality factor of these 1.3 GHz superconducting radio frequency (SRF) bulk niobium resonators, up to very high gradients; b) increase the achievable accelerating gradient of the cavity compared to its own baseline with state-of-the-art surface processing. Cavities subject to the new surface process have larger than two times the state of the art Q at 2K for accelerating fields > 35 MV/m. Moreover, very high accelerating gradients ~ 45 MV/m are repeatedly reached, which correspond to peak magnetic surface fields of 190 mT, among the highest measured for bulk niobium cavities. These findings open the opportunity to tailor the surface impurity content distribution to maximize performance in Q and gradients, and have therefore very important implications on future performance and cost of SRF based accelerators. They also help deepen the understanding of the physics of the RF niobium cavity surface.

  17. On-line hydrogen-isotope measurements of organic samples using elemental chromium: an extension for high temperature elemental-analyzer techniques.

    Science.gov (United States)

    Gehre, Matthias; Renpenning, Julian; Gilevska, Tetyana; Qi, Haiping; Coplen, Tyler B; Meijer, Harro A J; Brand, Willi A; Schimmelmann, Arndt

    2015-01-01

    The high temperature conversion (HTC) technique using an elemental analyzer with a glassy carbon tube and filling (temperature conversion/elemental analysis, TC/EA) is a widely used method for hydrogen isotopic analysis of water and many solid and liquid organic samples with analysis by isotope-ratio mass spectrometry (IRMS). However, the TC/EA IRMS method may produce inaccurate δ(2)H results, with values deviating by more than 20 mUr (milliurey = 0.001 = 1‰) from the true value for some materials. We show that a single-oven, chromium-filled elemental analyzer coupled to an IRMS substantially improves the measurement quality and reliability for hydrogen isotopic compositions of organic substances (Cr-EA method). Hot chromium maximizes the yield of molecular hydrogen in a helium carrier gas by irreversibly and quantitatively scavenging all reactive elements except hydrogen. In contrast, under TC/EA conditions, heteroelements like nitrogen or chlorine (and other halogens) can form hydrogen cyanide (HCN) or hydrogen chloride (HCl) and this can cause isotopic fractionation. The Cr-EA technique thus expands the analytical possibilities for on-line hydrogen-isotope measurements of organic samples significantly. This method yielded reproducibility values (1-sigma) for δ(2)H measurements on water and caffeine samples of better than 1.0 and 0.5 mUr, respectively. To overcome handling problems with water as the principal calibration anchor for hydrogen isotopic measurements, we have employed an effective and simple strategy using reference waters or other liquids sealed in silver-tube segments. These crimped silver tubes can be employed in both the Cr-EA and TC/EA techniques. They simplify considerably the normalization of hydrogen-isotope measurement data to the VSMOW-SLAP (Vienna Standard Mean Ocean Water-Standard Light Antarctic Precipitation) scale, and their use improves accuracy of the data by eliminating evaporative loss and associated isotopic fractionation while

  18. On-line hydrogen-isotope measurements of organic samples using elemental chromium: An extension for high temperature elemental-analyzer techniques

    Science.gov (United States)

    Gehre, Matthias; Renpenning, Julian; Gilevska, Tetyana; Qi, Haiping; Coplen, Tyler B.; Meijer, Harro A.J.; Brand, Willi A.; Schimmelmann, Arndt

    2015-01-01

    The high temperature conversion (HTC) technique using an elemental analyzer with a glassy carbon tube and filling (temperature conversion/elemental analysis, TC/EA) is a widely used method for hydrogen isotopic analysis of water and many solid and liquid organic samples with analysis by isotope-ratio mass spectrometry (IRMS). However, the TC/EA IRMS method may produce inaccurate δ2H results, with values deviating by more than 20 mUr (milliurey = 0.001 = 1‰) from the true value for some materials. We show that a single-oven, chromium-filled elemental analyzer coupled to an IRMS substantially improves the measurement quality and reliability for hydrogen isotopic compositions of organic substances (Cr-EA method). Hot chromium maximizes the yield of molecular hydrogen in a helium carrier gas by irreversibly and quantitatively scavenging all reactive elements except hydrogen. In contrast, under TC/EA conditions, heteroelements like nitrogen or chlorine (and other halogens) can form hydrogen cyanide (HCN) or hydrogen chloride (HCl) and this can cause isotopic fractionation. The Cr-EA technique thus expands the analytical possibilities for on-line hydrogen-isotope measurements of organic samples significantly. This method yielded reproducibility values (1-sigma) for δ2H measurements on water and caffeine samples of better than 1.0 and 0.5 mUr, respectively. To overcome handling problems with water as the principal calibration anchor for hydrogen isotopic measurements, we have employed an effective and simple strategy using reference waters or other liquids sealed in silver-tube segments. These crimped silver tubes can be employed in both the Cr-EA and TC/EA techniques. They simplify considerably the normalization of hydrogen-isotope measurement data to the VSMOW-SLAP (Vienna Standard Mean Ocean Water-Standard Light Antarctic Precipitation) scale, and their use improves accuracy of the data by eliminating evaporative loss and associated isotopic fractionation while

  19. Water/rock interactions and mass transport within a thermal gradient Application to the confinement of high level nuclear waste; Interactions solide/solution et transferts de matiere dans un gradient de temperature. Application au confinement des dechets nucleaires de haute-activite

    Energy Technology Data Exchange (ETDEWEB)

    Poinssot, Ch. [CEA Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Entreposage et de Stockage des Dechets]|[Ecole Normale Superieure, 92 - Fontenay-aux-Roses (France). Laboratoire de Geologie

    1998-12-31

    The initial stage of a high level nuclear waste disposal will be characterised by a large heat release within the near-field environment of the canisters. This heat flux caused by radioactive decay will lead to an increase of temperature and a subsequent thermal gradient between the `hot` canisters and the `cold`geological medium. In addition, this thermal gradient will decrease with time due to the heat decay although it could last hundred years. What will be the consequences of such a thermal field varying both on space and time for the alteration of the different constituents of the near field environment. In particular, what could be the effects on the radionuclides migration in the accidental case of an early breach of a canister during the thermal stage? This study brings significant answers to these questions in the light of a performance assessment study. This work is supported by a triple methodological approach involving experimental studies, modelling calculations and a natural analogues study. This complete work demonstrates that a thermal gradient leads to a large re-distribution of elements within the system: some elements are incorporated in the solid phases of the hot end (Si, Zr, Ca) whereas some others are in those of the cold end (Fe, Al, Zn). The confrontation of the results of very simple experiments with the results of a model built on equilibrium thermodynamics allow us to evidence the probable mechanisms causing this mass transport: out-of-equilibrium thermodiffusion processes coupled to irreversible precipitation. Moreover, the effects of the variation of temperatures with time is studied by the way of a natural system which underwent a similar temperature evolution as a disposal and which was initially rich in uranium: the Jurassic Alpine bauxites. In addition, part of the initial bauxite escaped this temperature transformations due to their incorporation in outer thrusting nappes. They are used as a reference. (author)

  20. Evidence of counter-gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

    Science.gov (United States)

    Snover, Melissa; Adams, Michael J.; Ashton, Donald T.; Bettaso, Jamie B.; Welsh, Hartwell H.

    2015-01-01

    Counter-gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human-altered habitats and changing climates.

  1. Analyzing the Potential Risk of Climate Change on Lyme Disease in Eastern Ontario, Canada Using Time Series Remotely Sensed Temperature Data and Tick Population Modelling

    Directory of Open Access Journals (Sweden)

    Angela Cheng

    2017-06-01

    Full Text Available The number of Lyme disease cases (Lyme borreliosis in Ontario, Canada has increased over the last decade, and that figure is projected to continue to increase. The northern limit of Lyme disease cases has also been progressing northward from the northeastern United States into southeastern Ontario. Several factors such as climate change, changes in host abundance, host and vector migration, or possibly a combination of these factors likely contribute to the emergence of Lyme disease cases in eastern Ontario. This study first determined areas of warming using time series remotely sensed temperature data within Ontario, then analyzed possible spatial-temporal changes in Lyme disease risk in eastern Ontario from 2000 to 2013 due to climate change using tick population modeling. The outputs of the model were validated by using tick surveillance data from 2002 to 2012. Our results indicated areas in Ontario where Lyme disease risk changed from unsustainable to sustainable for sustaining Ixodes scapularis (black-legged tick populations. This study provides evidence that climate change has facilitated the northward expansion of black-legged tick populations’ geographic range over the past decade. The results demonstrate that remote sensing data can be used to increase the spatial detail for Lyme disease risk mapping and provide risk maps for better awareness of possible Lyme disease cases. Further studies are required to determine the contribution of host migration and abundance on changes in eastern Ontario’s Lyme disease risk.

  2. A novel high-temperature furnace for combined in situ synchrotron X-ray diffraction and infrared thermal imaging to investigate the effects of thermal gradients upon the structure of ceramic materials.

    Science.gov (United States)

    Robinson, James B; Brown, Leon D; Jervis, Rhodri; Taiwo, Oluwadamilola O; Millichamp, Jason; Mason, Thomas J; Neville, Tobias P; Eastwood, David S; Reinhard, Christina; Lee, Peter D; Brett, Daniel J L; Shearing, Paul R

    2014-09-01

    A new technique combining in situ X-ray diffraction using synchrotron radiation and infrared thermal imaging is reported. The technique enables the application, generation and measurement of significant thermal gradients, and furthermore allows the direct spatial correlation of thermal and crystallographic measurements. The design and implementation of a novel furnace enabling the simultaneous thermal and X-ray measurements is described. The technique is expected to have wide applicability in material science and engineering; here it has been applied to the study of solid oxide fuel cells at high temperature.

  3. Analyzing the Surface Temperature Depression in Hot Stage Atomic Force Microscopy with Unheated Cantilevers: Application to the Crystallization of Poly(ethylene oxide)

    NARCIS (Netherlands)

    Schönherr, Holger; Bailey, Larry E.; Frank, Curtis W.

    2002-01-01

    The in situ study of phase transitions in polymers by real-time atomic force microscopy (AFM) has received much attention recently. In this paper we report on the accuracy of surface temperatures measured during variable-temperature AFM experiments. In AFM studies on organic and polymeric samples at

  4. Community and ecosystem responses to elevational gradients

    DEFF Research Database (Denmark)

    Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.

    2013-01-01

    Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients. There...... will provide powerful information that can improve predictions of climate change impacts within and across ecosystems.......Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients...... elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental manipulations...

  5. Permafrost and organic layer interactions over a climate gradient in a discontinuous permafrost zone

    Science.gov (United States)

    Kristofer D. Johnson; Jennifer W. Harden; A. David McGuire; Mark Clark; Fengming Yuan; Andrew O. Finley

    2013-01-01

    Permafrost is tightly coupled to the organic soil layer, an interaction that mediates permafrost degradation in response to regional warming. We analyzed changes in permafrost occurrence and organic layer thickness (OLT) using more than 3000 soil pedons across a mean annual temperature (MAT) gradient. Cause and effect relationships between permafrost probability (PF),...

  6. All-optical wavelength conversion and tuning by the cascaded sum- and difference frequency generation (cSFG/DFG) in a temperature gradient controlled Ti:PPLN channel waveguide.

    Science.gov (United States)

    Lee, Yeung Lak; Yu, Bong-Ahn; Jung, Changsoo; Noh, Young-Chul; Lee, Jongmin; Ko, Do-Kyeong

    2005-04-18

    All-optical single and multiple wavelength conversion and tuning by the cascaded sum- and difference frequency generation (cSFG/DFG) have been demonstrated in a temperature gradient controlled periodically poled Ti:LiNbO3 (Ti:PPLN) channel waveguide. Up to 4 channels of wavelength division multiplexed (WDM) signals which have 100 GHz channel spacing were simultaneously wavelength converted at a 16.8 degrees C temperature difference between both end faces in a Ti:PPLN waveguide. The 3 dB signal conversion bandwidth was measured to be as broad as 48 nm at single channel conversion. The maximum wavelength conversion efficiency and optical signal to noise ratio of wavelength converted channel were approximately -16 dB and -20 dB at a total pump power level of 810 mW.

  7. Reproductive capacity of the grey pine aphid and allocation response of Scots pine seedlings across temperature gradients: a test of hypotheses predicting outcomes of global warming

    Energy Technology Data Exchange (ETDEWEB)

    Holopainen, J. K.; Kainulainen, P. [University of Kuopio, Dept, of Ecology and Environmental Science, Kuopio (Finland)

    2004-01-01

    The research described in this paper had two objectives. The first objective was to test if Schizolachnus pineti, a pine specialist aphid and a potential defoliator of Scots pine in nursery conditions, could increase reproduction rate and reduce development time on Scots pine seedlings under the moderate increase in temperature expected by the current climatic change scenarios. The second objective was to explore two hypotheses predicting host-plant quality under elevated temperatures. Specifically, the study sought to establish whether increase in temperature will result in higher plant growth and lower concentration of carbon-based secondary metabolites, or alternatively, whether the concentration of total phenolics will remain the same with small temperature increases. Results showed that S. pineti females had the highest number of offsprings at a daytime temperature of 24 degrees C. Rate of population increase and relative growth rates were significantly higher at 26 degrees C than at 20 degrees C. Reproductive ability and the intrinsic rate of population increase were significantly affected by temperature and were negatively correlated with total phenolic concentration in needles. Concentration of some individual resin acids in needles and stems were affected by temperature. Concentration of monoterpenes, total phenolics, starch and total nitrogen in needles were not affected by temperature. Greatest biomass growth was shown to occur at 24 degrees C. Overall results supported the protein competition hypothesis, which predicts no changes in the concentration of plant phenolics with small changes in temperature. Reproductive ability of aphids was highest at 26 degree C; this was considered to be the result of the low starch/nitrogen ratio and low phenolic concentration in the host needles. 50 refs., 4 tabs., 3 figs.

  8. Increasing minimum daily temperatures are associated with enhanced pesticide use in cultivated soybean along a latitudinal gradient in the mid-western United States.

    Science.gov (United States)

    Ziska, Lewis H

    2014-01-01

    Assessments of climate change and food security often do not consider changes to crop production as a function of altered pest pressures. Evaluation of potential changes may be difficult, in part, because management practices are routinely utilized in situ to minimize pest injury. If so, then such practices, should, in theory, also change with climate, although this has never been quantified. Chemical (pesticide) applications remain the primary means of managing pests in industrialized countries. While a wide range of climate variables can influence chemical use, minimum daily temperature (lowest 24 h recorded temperature in a given year) can be associated with the distribution and thermal survival of many agricultural pests in temperate regions. The current study quantifies average pesticide applications since 1999 for commercial soybean grown over a 2100 km North-South latitudinal transect for seven states that varied in minimum daily temperature (1999-2013) from -28.6°C (Minnesota) to -5.1°C (Louisiana). Although soybean yields (per hectare) did not vary by state, total pesticide applications (kg of active ingredient, ai, per hectare) increased from 4.3 to 6.5 over this temperature range. Significant correlations were observed between minimum daily temperatures and kg of ai for all pesticide classes. This suggested that minimum daily temperature could serve as a proxy for pesticide application. Longer term temperature data (1977-2013) indicated greater relative increases in minimum daily temperatures for northern relative to southern states. Using these longer-term trends to determine short-term projections of pesticide use (to 2023) showed a greater comparative increase in herbicide use for soybean in northern; but a greater increase in insecticide and fungicide use for southern states in a warmer climate. Overall, these data suggest that increases in pesticide application rates may be a means to maintain soybean production in response to rising minimum daily

  9. Survival and behaviour of juvenile unionid mussels exposed to thermal stress and dewatering in the presence of a sediment temperature gradient

    Science.gov (United States)

    Archambault, L.; Cope, W. Gregory; Kwak, Thomas J.

    2014-01-01

    Freshwater mussels (Unionidae) are a highly imperilled faunal group. One critical threat is thermal sensitivity, because global climate change and other anthropogenic activities contribute to increasing stream temperature and altered hydrologic flow that may be detrimental to freshwater mussels.

  10. RESPONSE OF HATCHLING AND YEARLING TURTLES TO THERMAL GRADIENTS: COMPARISON OF CHELYDRA SERPENTINA AND TRACHEMYS SCRIPTA

    Science.gov (United States)

    In laboratory test, young Chelydra serpentina and Trachemys scripta altered their distribution in the presence of a temperature gradient. Selection of temperatures in the gradient for hatchlings and yearlings showed that body temperature (Tbs) of C. serpentina were lower tha...

  11. Analysis of pedestal gradient characteristic on the Experimental Advanced Superconducting Tokamak

    Science.gov (United States)

    Wang, Teng Fei; Han, Xiao Feng; Zang, Qing; Xiao, Shu Mei; Tian, Bao Gang; Hu, Ai Lan; Zhao, Jun Yu

    2016-05-01

    A pedestal database was built based on type I edge localized mode H-modes in the Experimental Advanced Superconducting Tokamak. The most common functional form hyperbolic tangent function (tanh) method is used to analyze pedestal characteristics. The pedestal gradient scales linearly with its pedestal top and the normalized pedestal pressure gradient α shows a strong correlation with electron collisionality. The connection among pedestal top value, gradient, and width is established with the normalized pedestal pressure gradient. In the core region of the plasma, the nature of the electron temperature stiffness reflects a proportionality between core and pedestal temperature while the increase proportion is lower than that expected in the high temperature region. However, temperature profile stiffness is limited or even disappears at the edge of the plasma, while the gradient length ratio ( ηe ) on the pedestal is important. The range of ηe is from 0.5 to 2, varying with the plasma parameters. The pedestal temperature brings a more significant impact on ηe than pedestal density.

  12. Vertically aligned CNT growth on a microfabricated silicon heater with integrated temperature control—determination of the activation energy from a continuous thermal gradient

    DEFF Research Database (Denmark)

    Engstrøm, Daniel Southcott; Rupesinghe, Nalin L; Teo, Kenneth B K

    2011-01-01

    Silicon microheaters for local growth of a vertically aligned carbon nanotube (VACNT) were fabricated. The microheaters had a four-point-probe structure that measured the silicon conductivity variations in the heated region which is a measure of the temperature. Through FEM simulations...

  13. Differential responses of production and respiration to temperature and moisture drive the carbon balance across a climatic gradient in New Mexico

    Science.gov (United States)

    Kristina J. Anderson-Teixeira; John P. Delong; Andrew M. Fox; Daniel A. Brese; Marcy E. Litvak

    2011-01-01

    Southwestern North America faces an imminent transition to a warmer, more arid climate, and it is critical to understand how these changes will affect the carbon balance of southwest ecosystems. In order to test our hypothesis that differential responses of production and respiration to temperature and moisture shape the carbon balance across a range of spatio-temporal...

  14. Examination of Surface Temperature Modification by Open-Top Chambers along Moisture and Latitudinal Gradients in Arctic Alaska Using Thermal Infrared Photography

    OpenAIRE

    Nathan C. Healey; Oberbauer, Steven F; Hollister, Robert D.

    2016-01-01

    Passive warming manipulation methodologies, such as open-top chambers (OTCs), are a meaningful approach for interpretation of impacts of climate change on the Arctic tundra biome. The magnitude of OTC warming has been studied extensively, revealing an average plot-level warming of air temperature that ranges between 1 and 3 °C as measured by shielded resistive sensors or thermocouples. Studies have also shown that the amount of OTC warming depends in part on location climate, vegetation, and ...

  15. Effects of light conditions and temperature gradients on vertical migration behavior of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogramma)

    Science.gov (United States)

    Flanders, K. R.; Laurel, B.

    2016-02-01

    Early life stages of marine fishes must maximize growth while minimizing vulnerability to predators. Larval stages in particular are subject to ocean currents, but encounter favorable habitats by adjusting their vertical position in the water column. The investigation of environmental cues that change larval fish behavior is therefore crucial to understanding larval drift and dispersal modeling, and subsequently population structure and connectivity. In this study, the behavioral responses of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogramma) in a vertical water column were examined. Two prominent environmental variables, light and temperature, were manipulated over 3 h during observational trials. Light intensity was studied at two levels (1.484 x 101 μE m-2 s-1 ; 2.54 x102 μE m-2 s-1), and a diel effect was studied through the removal of light after 2 h. Light intensity did not significantly impact the position of either species in a vertical water column. However, a significant difference by species was apparent when all light levels were considered: the mean position of Arctic cod was closer to the surface of the water than that of walleye pollock. The effect of temperature through the introduction of a thermocline (range 5.6°C - 1.5°C) was limited to walleye pollock given the Arctic cod larvae were surface oriented across all light treatments. However, the thermocline did not significantly impact the relative change in position from light to dark in walleye pollock, likely because they were also surface oriented in control treatments. These results could be incorporated into future larval dispersal and survival models, particularly in Alaskan and Arctic waters, to investigate changes in species distributions resulting from global warming impacts. These results also indicate population structures of Arctic cod and walleye pollock could be affected, which may be reflected in ecosystem and trophic interactions. Because Arctic cod

  16. Effect of thermal gradients on the electromigration lifetime in power electronics

    NARCIS (Netherlands)

    Nguyen, Van Hieu; Salm, Cora; Krabbenborg, B.H.; Krabbenborg, B.; Weide-Zaage, K.; Bisschop, J.; Mouthaan, A.J.; Kuper, F.G.

    2004-01-01

    The combined effects of electromigration and thermomigration are studied. Significantly shorter electromigration lifetimes are observed in the presence of a temperature gradient. This cannot be explained by thermomigration only, but is attributed to the effect of temperature gradient on

  17. Metabolic rates and tissue composition of the coral Pocillopora verrucosa over 12 latitudes in the Red Sea characterized by strong temperature and nutrient gradient, supplement to: Sawall, Yvonne; Al-Sofyani, A; Hohn, S; Banguera-Hinestroza, E; Voolstra, Christian R; Wahl, Martin (2015): Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming. Scientific Reports, 5, 8940

    KAUST Repository

    Sawall, Yvonne

    2015-01-01

    Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12 degrees latitudes featuring a steep temperature gradient between the northern (28.5 degrees N, 21-27 degrees C) and southern (16.5 degrees N, 28-33 degrees C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29 degrees C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals

  18. Universal gradient descent

    OpenAIRE

    Gasnikov, Alexander

    2017-01-01

    In this small book we collect many different and useful facts around gradient descent method. First of all we consider gradient descent with inexact oracle. We build a general model of optimized function that include composite optimization approach, level's methods, proximal methods etc. Then we investigate primal-dual properties of the gradient descent in general model set-up. At the end we generalize method to universal one.

  19. Microinstabilities in weak density gradient tokamak systems

    Energy Technology Data Exchange (ETDEWEB)

    Tang, W.M.; Rewoldt, G.; Chen, L.

    1986-04-01

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient.

  20. Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses.

    Science.gov (United States)

    Salazar-Parra, Carolina; Aranjuelo, Iker; Pascual, Inmaculada; Erice, Gorka; Sanz-Sáez, Álvaro; Aguirreolea, Jone; Sánchez-Díaz, Manuel; Irigoyen, Juan José; Araus, José Luis; Morales, Fermín

    2015-02-01

    Although plant performance under elevated CO2 has been extensively studied in the past little is known about photosynthetic performance changing simultaneously CO2, water availability and temperature conditions. Moreover, despite of its relevancy in crop responsiveness to elevated CO2 conditions, plant level C balance is a topic that, comparatively, has received little attention. In order to test responsiveness of grapevine photosynthetic apparatus to predicted climate change conditions, grapevine (Vitis vinifera L. cv. Tempranillo) fruit-bearing cuttings were exposed to different CO2 (elevated, 700ppm vs. ambient, ca. 400ppm), temperature (ambient vs. elevated, ambient +4°C) and irrigation levels (partial vs. full irrigation). Carbon balance was followed monitoring net photosynthesis (AN, C gain), respiration (RD) and photorespiration (RL) (C losses). Modification of environment (13)C isotopic composition (δ(13)C) under elevated CO2 (from -10.30 to -24.93‰) enabled the further characterization of C partitioning into roots, cuttings, shoots, petioles, leaves, rachides and berries. Irrespective of irrigation level and temperature, exposure to elevated CO2 induced photosynthetic acclimation of plants. C/N imbalance reflected the inability of plants grown at 700ppm CO2 to develop strong C sinks. Partitioning of labeled C to storage organs (main stem and roots) did not avoid accumulation of labeled photoassimilates in leaves, affecting negatively Rubisco carboxylation activity. The study also revealed that, after 20 days of treatment, no oxidative damage to chlorophylls or carotenoids was observed, suggesting a protective role of CO2 either at current or elevated temperatures against the adverse effect of water stress. Copyright © 2014 Elsevier GmbH. All rights reserved.

  1. Trace impurity analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, W.J.; Edwards, D. Jr.

    1979-01-01

    The desirability for long-term reliability of large scale helium refrigerator systems used on superconducting accelerator magnets has necessitated detection of impurities to levels of a few ppM. An analyzer that measures trace impurity levels of condensable contaminants in concentrations of less than a ppM in 15 atm of He is described. The instrument makes use of the desorption temperature at an indicated pressure of the various impurities to determine the type of contaminant. The pressure rise at that temperature yields a measure of the contaminant level of the impurity. A LN/sub 2/ cryogenic charcoal trap is also employed to measure air impurities (nitrogen and oxygen) to obtain the full range of contaminant possibilities. The results of this detector which will be in use on the research and development helium refrigerator of the ISABELLE First-Cell is described.

  2. Gradient and vorticity banding

    NARCIS (Netherlands)

    Dhont, Jan K.G.; Briels, Willem J.

    2008-01-01

    "Banded structures" of macroscopic dimensions can be induced by simple shear flow in many different types of soft matter systems. Depending on whether these bands extend along the gradient or vorticity direction, the banding transition is referred to as "gradient banding" or "vorticity banding,"

  3. Marangoni effects on a thin liquid film coating a sphere with axial or radial thermal gradients

    Science.gov (United States)

    Kang, Di; Nadim, Ali; Chugunova, Marina

    2017-07-01

    We study the time evolution of a thin liquid film coating the outer surface of a sphere in the presence of gravity, surface tension, and thermal gradients. We derive the fourth-order nonlinear partial differential equation that models the thin film dynamics, including Marangoni terms arising from the dependence of surface tension σ on temperature T. We consider two different imposed temperature distributions with axial or radial thermal gradients. We analyze the stability of a uniform coating under small perturbations and carry out numerical simulations in COMSOL for a range of parameter values. In the case of an axial temperature gradient, we find steady states either with uniform film thickness or with the fluid accumulating at the bottom or near the top of the sphere, depending on the total volume of liquid in the film, dictating whether gravity or Marangoni effects dominate. This suggests a potential method for the indirect measurement of d σ /d T by monitoring the thickness profile of the thin film. In the case of a radial temperature gradient, a stability analysis reveals the most unstable non-axisymmetric modes on an initially uniform coating film.

  4. Subsurface temperatures, geothermal gradients and hydrocarbon ...

    African Journals Online (AJOL)

    Global Journal of Geological Sciences. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 7, No 1 (2009) >. Log in or Register to get access to full text downloads.

  5. Complex surface concentration gradients by stenciled "electro click chemistry".

    Science.gov (United States)

    Hansen, Thomas S; Lind, Johan U; Daugaard, Anders E; Hvilsted, Søren; Andresen, Thomas L; Larsen, Niels B

    2010-10-19

    Complex one- or two-dimensional concentration gradients of alkynated molecules are produced on azidized conducting polymer substrates by stenciled "electro click chemistry". The latter describes the local electrochemical generation of catalytically active Cu(I) required to complete a "click reaction" between alkynes and azides at room temperature. A stencil on the counter electrode defines the shape and multiplicity of the gradient(s) on the conducting polymer substrate, while the specific reaction conditions control gradient steepness and the maximum concentration deposited. Biologically active ligands including cell binding peptides are patterned in gradients by this method without losing their biological function or the conductivity of the polymer.

  6. Geothermal gradient of Campos Basin, Rio de Janeiro State; Gradiente geotermico da Bacia de Campos

    Energy Technology Data Exchange (ETDEWEB)

    Jahnert, Ricardo J. [PETROBRAS, Campos, RJ (Brazil). Dept. de Exploracao

    1987-08-01

    Study of thermal gradient in subsurface, using drilling wells as measurer to the temperature variation, its implications at oil classification and microorganisms actuation,on the sedimentary basin of Campos (Rio de Janeiro State, Brazil) are presented. Results obtained, main factors who control temperature distribution within wells, on the basin, temperature anomalies found and the relationship between temperature and oil pattern are also discussed. 10 figs., 9 refs

  7. Second gradient poromechanics

    CERN Document Server

    Sciarra, Giulio; Coussy, Olivier

    2010-01-01

    Second gradient theories have been developed in mechanics for treating different phenomena as capillarity in fluids, plasticity and friction in granular materials or shear band deformations. Here, there is an attempt of formulating a second gradient Biot like model for porous materials. In particular the interest is focused in describing the local dilatant behaviour of a porous material induced by pore opening elastic and capillary interaction phenomena among neighbouring pores and related micro-filtration phenomena by means of a continuum microstructured model. The main idea is to extend the classical macroscopic Biot model by including in the description second gradient effects. This is done by assuming that the surface contribution to the external work rate functional depends on the normal derivative of the velocity or equivalently assuming that the strain work rate functional depends on the porosity and strain gradients. According to classical thermodynamics suitable restrictions for stresses and second g...

  8. Integral Field Spectroscopy Surveys: Oxygen Abundance Gradients

    Science.gov (United States)

    Sánchez, S. F.; Sánchez-Menguiano, L.

    2017-07-01

    We present here the recent results on our understanding of oxygen abundance gradients derived using Integral Field Spectroscopic surveys. In particular we analyzed more than 2124 datacubes corresponding to individual objects observed by the CALIFA (˜ 734 objects) and the public data by MaNGA (˜ 1390 objects), deriving the oxygen abundance gradient for each galaxy. We confirm previous results that indicate that the shape of this gradient is very similar for all galaxies with masses above 109.5M⊙, presenting in average a very similar slope of ˜ -0.04 dex within 0.5-2.0 re, with a possible drop in the inner regions (r109.5M⊙) the gradient seems to be flatter than for more massive ones. All these results agree with an inside-out growth of massive galaxies and indicate that low mass ones may still be growing in an outside in phase.

  9. High Gradient Accelerator Research

    Energy Technology Data Exchange (ETDEWEB)

    Temkin, Richard [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Physics. Plasma Science and Fusion Center

    2016-07-12

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  10. Preconditioned Stochastic Gradient Descent.

    Science.gov (United States)

    Li, Xi-Lin

    2017-03-09

    Stochastic gradient descent (SGD) still is the workhorse for many practical problems. However, it converges slow, and can be difficult to tune. It is possible to precondition SGD to accelerate its convergence remarkably. But many attempts in this direction either aim at solving specialized problems, or result in significantly more complicated methods than SGD. This paper proposes a new method to adaptively estimate a preconditioner, such that the amplitudes of perturbations of preconditioned stochastic gradient match that of the perturbations of parameters to be optimized in a way comparable to Newton method for deterministic optimization. Unlike the preconditioners based on secant equation fitting as done in deterministic quasi-Newton methods, which assume positive definite Hessian and approximate its inverse, the new preconditioner works equally well for both convex and nonconvex optimizations with exact or noisy gradients. When stochastic gradient is used, it can naturally damp the gradient noise to stabilize SGD. Efficient preconditioner estimation methods are developed, and with reasonable simplifications, they are applicable to large-scale problems. Experimental results demonstrate that equipped with the new preconditioner, without any tuning effort, preconditioned SGD can efficiently solve many challenging problems like the training of a deep neural network or a recurrent neural network requiring extremely long-term memories.

  11. Quantitative estimates of disturbances contributed by a megalopolis to the temperature field of the atmospheric boundary layer

    Science.gov (United States)

    Kadygrov, N. E.; Kruchenitskii, G. M.; Lykov, A. D.

    2007-02-01

    Seasonal and diurnal variations in the temperature of the atmospheric boundary layer (ABL) are analyzed, and the features of spatial and temporal variations in ABL temperature that are caused by the influence of a megalopolis are revealed. The gradients of air temperature for the megalopolis, its vicinity, and background conditions are compared. A multiplicative model of the seasonal diurnal variability of ABL temperature is constructed, and the relative frequencies of unstable ABL-temperature stratification are studied.

  12. Regolith Evolved Gas Analyzer

    Science.gov (United States)

    Hoffman, John H.; Hedgecock, Jud; Nienaber, Terry; Cooper, Bonnie; Allen, Carlton; Ming, Doug

    2000-01-01

    The Regolith Evolved Gas Analyzer (REGA) is a high-temperature furnace and mass spectrometer instrument for determining the mineralogical composition and reactivity of soil samples. REGA provides key mineralogical and reactivity data that is needed to understand the soil chemistry of an asteroid, which then aids in determining in-situ which materials should be selected for return to earth. REGA is capable of conducting a number of direct soil measurements that are unique to this instrument. These experimental measurements include: (1) Mass spectrum analysis of evolved gases from soil samples as they are heated from ambient temperature to 900 C; and (2) Identification of liberated chemicals, e.g., water, oxygen, sulfur, chlorine, and fluorine. REGA would be placed on the surface of a near earth asteroid. It is an autonomous instrument that is controlled from earth but does the analysis of regolith materials automatically. The REGA instrument consists of four primary components: (1) a flight-proven mass spectrometer, (2) a high-temperature furnace, (3) a soil handling system, and (4) a microcontroller. An external arm containing a scoop or drill gathers regolith samples. A sample is placed in the inlet orifice where the finest-grained particles are sifted into a metering volume and subsequently moved into a crucible. A movable arm then places the crucible in the furnace. The furnace is closed, thereby sealing the inner volume to collect the evolved gases for analysis. Owing to the very low g forces on an asteroid compared to Mars or the moon, the sample must be moved from inlet to crucible by mechanical means rather than by gravity. As the soil sample is heated through a programmed pattern, the gases evolved at each temperature are passed through a transfer tube to the mass spectrometer for analysis and identification. Return data from the instrument will lead to new insights and discoveries including: (1) Identification of the molecular masses of all of the gases

  13. Effect of neglecting geothermal gradient on calculated oil recovery

    Science.gov (United States)

    Safari, Mehdi; Mohammadi, Majid; Sedighi, Mehdi

    2017-03-01

    Reduced recovery rate with time is a common challenge for most of the oil producing reservoirs. Water flooding is one of the most common methods used for enhanced oil recovery. Simulating water-flooding process is sometimes carried out without considering the effect of geothermal gradient, and an average temperature is assumed for all the grid blocks. However, the gradient plays a significant role on the reservoir fluid properties. So neglecting its effect might result in a large error in the calculated oil recovery results, especially for the thick reservoirs, which in theory can show significant variations in temperature with depth. In this paper, first, advancing the waterfront during injection into a geothermal oil reservoir is discussed. Then, the performance of considering either an average temperature or gradient temperature, are considered and compared with each other. The results suggest that assuming a fixed average reservoir temperature with no geothermal gradient, can lead to a pronounced error for calculated oil recovery.

  14. An integrated systems calculation of a steam generator tube rupture in a modular prismatic HTGR (high-temperature gas-cooled reactor) conceptual design using ATHENA (Advanced Thermal-Hydraulic Energy Network Analyzer)

    Energy Technology Data Exchange (ETDEWEB)

    Beelman, R.J. (Idaho National Engineering Laboratory, Idaho Falls (USA))

    1989-11-01

    The capability to perform integrated systems calculations of modular high-temperature gas-cooled reactor (MHTGR) transients has been developed at the Idaho National Engineering Laboratory (INEL) using the Advanced Thermal-Hydraulic Energy Network Analyzer (ATHENA) computer code. A scoping calculation of a steam generator tube rupture (SGTR) water ingress event in a prismatic 2 {times} 350-MW(thermal) MHTGR conceptual design has been completed at INEL using ATHENA. The proposed MHTGR design incorporates dual, graphite-moderated, helium-cooled, 350-MW(thermal), annular prismatic core concept reactor plants, each configured with an individual helical once-through steam generator steaming a common 280-MW(electric) turbine generator set.

  15. Uniform gradient expansions

    Directory of Open Access Journals (Sweden)

    Massimo Giovannini

    2015-06-01

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

  16. Thermal gradients in Southwestern United States and the effect on bridge bearing loads : final report.

    Science.gov (United States)

    2017-05-01

    Thermal gradients became a component of bridge design after soffit cracking in prestressed concrete bridges was attributed to nonlinear temperature distribution through the depth of the bridge. While the effect of thermal gradient on stress distribut...

  17. Estimation of gradients in quantum metrology

    Science.gov (United States)

    Altenburg, Sanah; Oszmaniec, Michał; Wölk, Sabine; Gühne, Otfried

    2017-10-01

    We develop a general theory to estimate magnetic field gradients in quantum metrology. We consider a system of N particles distributed on a line whose internal degrees of freedom interact with a magnetic field. Usually gradient estimation is based on precise measurements of the magnetic field at two different locations, performed with two independent groups of particles. This approach, however, is sensitive to fluctuations of the offset field determining the level splitting of the particles and results in collective dephasing. In this work, we use the framework of quantum metrology to assess the maximal accuracy for gradient estimation. For arbitrary positioning of particles, we identify optimal entangled and separable states, allowing the estimation of gradients with maximal accuracy, quantified by the quantum Fisher information. We also analyze the performance of states from the decoherence-free subspace (DFS), which are insensitive to the fluctuations of the magnetic offset field. We find that these states allow us to measure a gradient directly, without the necessity of estimating the magnetic offset field. Moreover, we show that DFS states attain a precision for gradient estimation comparable to the optimal entangled states. Finally, for the above classes of states, we find simple and feasible measurements saturating the quantum Cramér-Rao bound.

  18. Effects of lithology on geothermal gradient on the southeast Nigeria ...

    African Journals Online (AJOL)

    A study of the effects of lithologic formations on geothermal gradients is carried out in the south-east Niger Delta, Nigeria, using continuous temperature and lithologic log data from closely-spaced petroleum wells. The gradient profiles obtained for the deep wells, logged to depths between 6500 ft (1981m) and 8500ft ...

  19. Thermal vibration analysis of nanoplates based on the higher-order nonlocal strain gradient theory by an analytical approach

    Science.gov (United States)

    Nematollahi, Mohammad Sadegh; Mohammadi, Hossein; Nematollahi, Mohammad Ali

    2017-11-01

    In this paper, a new formulation for analyzing free vibration of thin rectangular nanoplates under different thermal conditions is obtained based on the higher-order nonlocal strain gradient theory. Governing equations and non-classical boundary conditions of the nanoplate are derived by using the variational approach. The exact solution is obtained as a function of higher-order and lower-order nonlocal parameters, strain gradient length scale and temperature difference using Navier solution procedure. The influences of small-scale parameters on the vibrational behavior of the nanoplate are investigated for various thermal conditions. High and low temperature conditions are considered to study the effects of changes in temperature and small-scale parameters. It has been shown that increasing the nonlocal parameters decrease the natural frequency of the nanoplate, while increasing the strain gradient length scale will increase it. Also, the natural frequency of the nanoplate will increase by increasing the temperature difference in low temperature conditions, but it will decrease by increasing the temperature difference in high temperature conditions. Non-uniform behaviors are reported for some cases and softening effect and hardening effect are studied. To validate the solutions, the results are compared with previous researches.

  20. Probabilistic Multileave Gradient Descent

    NARCIS (Netherlands)

    Oosterhuis, H.; Schuth, A.; de Rijke, M.; Ferro, N.; Crestani, F.; Moens, M.-F.; Mothe, J.; Silvestri, F.; Di Nunzio, G.M.; Hauff, C.; Silvello, G.

    2016-01-01

    Online learning to rank methods aim to optimize ranking models based on user interactions. The dueling bandit gradient descent (DBGD) algorithm is able to effectively optimize linear ranking models solely from user interactions. We propose an extension of DBGD, called probabilistic multileave

  1. Conservation status affects elevational gradient in bird diversity in the Himalaya: A new perspective

    Directory of Open Access Journals (Sweden)

    Prakash Kumar Paudel

    2014-12-01

    Full Text Available Understanding diversity patterns along altitudinal gradients, and their underlying causes are important for conserving biodiversity. Previous studies have focused on climatic, energetic, and geographic variables (e.g., mid-domain effects, with less attention paid to human-induced habitat modifications. We used published data of bird distributions along an elevational gradient (0–4900 m in the Nepalese Himalaya and interpolated species presence between elevational limits. The relationship between species richness and environmental variables was analyzed using generalized linear models. A low plateau relationship between bird richness and elevation was observed, with a main peak at intermediate elevations (2800 m. Across the total gradient, interpolated bird species richness had a unimodal relationship to maximum monthly precipitation and a linear response to seasonal variation in temperature, proportion of forest cover, and proportion of protected area. In lower elevations (0–2800 m, interpolated species richness had a positive and linear response to the proportion of Ramsar sites and a unimodal response to habitat heterogeneity. At higher elevations (2900–4900 m, interpolated bird richness had a positive linear response to monthly variation in temperature and a negative linear response to proportion forest cover. We conclude that factors related to human management are important drivers of elevational gradients in bird species richness.

  2. Evaluation of porous gradient hydroxyapatite/zirconia composites for repair of lumbar vertebra defect in dogs.

    Science.gov (United States)

    Shao, Rong-Xue; Quan, Ren-Fu; Huang, Xiao-Long; Wang, Tuo; Xie, Shang-Ju; Gao, Huan-Huan; Wei, Xi-Cheng; Yang, Di-Sheng

    2016-04-01

    To evaluate the effects of porous gradient composites with hydroxyapatite/zirconia and autologous iliac in repair of lumbar vertebra body defects in dogs. (1) New porous gradient hydroxyapatite/zirconia composites were prepared using foam immersion, gradient compound and high temperature sintering; (2) A total of 18 adult beagle dogs, aged five to eight months and weighted 10-13 kg, were randomly assigned into two subgroups, which were implanted with new porous gradient hydroxyapatite/zirconia composites (subgroup A in 12) or autologous iliac bone (subgroup B in 6); (3) The post-operative data were analyzed and compared between the subgroups to repair the vertebral body defect by roentgenoscopy, morphology and biomechanics. The porosity of new porous gradient hydroxyapatite/zirconia composites is at 25 poles per inch, and the size of pores is at between 150 and 300 µm. The post-operative roentgenoscopy displayed that new-bone formation is increased gradually, and the interface between composites and host-bone becomes became blur, and the new-bone around the composites were integrated into host-bone at 24 weeks postoperatively in subgroup A. As to subgroup B, the resorption and restructure were found at six weeks after the surgery, and the graft-bone and host-bone have been integrated completely without obvious boundary at 24 weeks postoperatively. Histomorphologic study showed that the amount of bone within pores of the porous gradient hydroxyapatite/zirconia composites increased continuously with a prolonged implantation time, and that partial composites were degradated and replaced by new-bone trabeculae. There was no significant difference between subgroups (P > 0.05) in the ultimate compressive strengths. New porous gradient hydroxyapatite/zirconia composites can promote the repair of bony defect, and induce bone tissue to ingrow into the pores, which may be applied widely to the treatment of bony defect in the future. © The Author(s) 2016.

  3. Gradient augmented level set method for phase change simulations

    Science.gov (United States)

    Anumolu, Lakshman; Trujillo, Mario F.

    2018-01-01

    A numerical method for the simulation of two-phase flow with phase change based on the Gradient-Augmented-Level-set (GALS) strategy is presented. Sharp capturing of the vaporization process is enabled by: i) identification of the vapor-liquid interface, Γ (t), at the subgrid level, ii) discontinuous treatment of thermal physical properties (except for μ), and iii) enforcement of mass, momentum, and energy jump conditions, where the gradients of the dependent variables are obtained at Γ (t) and are consistent with their analytical expression, i.e. no local averaging is applied. Treatment of the jump in velocity and pressure at Γ (t) is achieved using the Ghost Fluid Method. The solution of the energy equation employs the sub-grid knowledge of Γ (t) to discretize the temperature Laplacian using second-order one-sided differences, i.e. the numerical stencil completely resides within each respective phase. To carefully evaluate the benefits or disadvantages of the GALS approach, the standard level set method is implemented and compared against the GALS predictions. The results show the expected trend that interface identification and transport are predicted noticeably better with GALS over the standard level set. This benefit carries over to the prediction of the Laplacian and temperature gradients in the neighborhood of the interface, which are directly linked to the calculation of the vaporization rate. However, when combining the calculation of interface transport and reinitialization with two-phase momentum and energy, the benefits of GALS are to some extent neutralized, and the causes for this behavior are identified and analyzed. Overall the additional computational costs associated with GALS are almost the same as those using the standard level set technique.

  4. Thermodynamic study of residual heat from a high temperature nuclear reactor to analyze its viability in cogeneration processes; Estudio termodinamico del calor residual de un reactor nuclear de alta temperatura para analizar su viabilidad en procesos de cogeneracion

    Energy Technology Data Exchange (ETDEWEB)

    Santillan R, A.; Valle H, J.; Escalante, J. A., E-mail: santillanaura@gmail.com [Universidad Politecnica Metropolitana de Hidalgo, Boulevard acceso a Tolcayuca 1009, Ex-Hacienda San Javier, 43860 Tolcayuca, Hidalgo (Mexico)

    2015-09-15

    In this paper the thermodynamic study of a nuclear power plant of high temperature at gas turbine (GTHTR300) is presented for estimating the exploitable waste heat in a process of desalination of seawater. One of the most studied and viable sustainable energy for the production of electricity, without the emission of greenhouse gases, is the nuclear energy. The fourth generation nuclear power plants have greater advantages than those currently installed plants; these advantages have to do with security, increased efficiencies and feasibility to be coupled to electrical cogeneration processes. In this paper the thermodynamic study of a nuclear power plant type GTHTR300 is realized, which is selected by greater efficiencies and have optimal conditions for use in electrical cogeneration processes due to high operating temperatures, which are between 700 and 950 degrees Celsius. The aim of the study is to determine the heat losses and the work done at each stage of the system, determining where they are the greatest losses and analyzing in that processes can be taken advantage. Based on the study was appointed that most of the energy losses are in form of heat in the coolers and usually this is emitted into the atmosphere without being used. From the results a process of desalination of seawater as electrical cogeneration process is proposed. This paper contains a brief description of the operation of the nuclear power plant, focusing on operation conditions and thermodynamic characteristics for the implementation of electrical cogeneration process, a thermodynamic analysis based on mass and energy balance was developed. The results allow quantifying the losses of thermal energy and determining the optimal section for coupling of the reactor with the desalination process, seeking to have a great overall efficiency. (Author)

  5. Increasing SLEDed Linac Gradient

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, Zoltan D

    2001-11-08

    This note will show how to increase the SLED [1] gradient by varying Q{sub e}, the external Q of the SLED cavity, by increasing its Q{sub 0} and by increasing the compression ratio. If varying the external Q is to be effective, then the copper losses should be small so that Q{sub 0} >> Q{sub e}. Methods of varying Q{sub e} will be indicated but no experimental data will be presented. If we increase the klystron pulse width from 3.5 to 5 {micro}S and increase Q{sub 0} from the present 100000 to 300000, then the gradient increases by 19% and the beam energy increases from 50 to 60 GeV. This note will also discuss SLED operation at 11424 MHz, the NLC frequency. Without Q{sub e} switching, using SLED at 11424 MHz increases the SLAC gradient from 21 MV/m to 34 MV/m, and at the same repetition rate, uses about 1/5 of rf average power. If we also double the compression ratio, we reach 47 MV/m and over 100 GeV beam energy.

  6. Project ATLANTA (Atlanta Land use Analysis: Temperature and Air Quality): Use of Remote Sensing and Modeling to Analyze How Urban Land Use Change Affects Meteorology and Air Quality Through Time

    Science.gov (United States)

    Quattrochi, Dale A.; Luvall, Jeffrey C.; Estes, Maurice G., Jr.

    1999-01-01

    This paper presents an overview of Project ATLANTA (ATlanta Land use ANalysis: Temperature and Air-quality) which is an investigation that seeks to observe, measure, model, and analyze how the rapid growth of the Atlanta, Georgia metropolitan area since the early 1970's has impacted the region's climate and air quality. The primary objectives for this research effort are: (1) To investigate and model the relationships between land cover change in the Atlanta metropolitan, and the development of the urban heat island phenomenon through time; (2) To investigate and model the temporal relationships between Atlanta urban growth and land cover change on air quality; and (3) To model the overall effects of urban development on surface energy budget characteristics across the Atlanta urban landscape through time. Our key goal is to derive a better scientific understanding of how land cover changes associated with urbanization in the Atlanta area, principally in transforming forest lands to urban land covers through time, has, and will, effect local and regional climate, surface energy flux, and air quality characteristics. Allied with this goal is the prospect that the results from this research can be applied by urban planners, environmental managers and other decision-makers, for determining how urbanization has impacted the climate and overall environment of the Atlanta area. Multiscaled remote sensing data, particularly high resolution thermal infrared data, are integral to this study for the analysis of thermal energy fluxes across the Atlanta urban landscape.

  7. Geothermal gradient and heat flow in the state of Rio de Janeiro

    OpenAIRE

    Gomes, Antonio Jorge de Lima; Hamza,Valiya Mannathal

    2005-01-01

    Results of geothermal studies carried out at 72 localities have been used in evaluation of temperature gradient and heat flow values of the upper crust in the state of Rio de Janeiro. The investigations included temperature logs in boreholes and wells, calculation of geothermal gradients, measurements of thermal conductivity and determination of heat flow density. In addition, estimates of temperature gradients and heat flow were also made for areas of thermo-mineral springs, based on the so-...

  8. Geothermal gradient map of Brazilian sedimentary basins; Gradiente geotermico das bacias sedimentares brasileiras

    Energy Technology Data Exchange (ETDEWEB)

    Zembruscki, Sylvio G.; Chang, Hung K. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    1989-07-01

    Studies in 21 Brazilian sedimentary basins applying temperature data obtained from oil well logging and drill stem tests are presented. The results permitted an characterization of geothermal gradient according the rocks formation and could be used as geothermal energy sources. The three main basins (Middle Amazonas, Barreirinhas and Parnaiba) had more complete studies and permit an evaluation of the geothermal temperature variation in function of the rocks formation on different geological periods (Paleozoic, Mesozoic and Cenozoic basins). 10 figs., 1 tab., 34 refs

  9. Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord–Alesund area, western Norway

    NARCIS (Netherlands)

    Birks, H.H.; Dinter, M. van

    2010-01-01

    Modern climate in western Norway shows a strong west–east gradient in oceanicity–continentality (coast to inner fjord) and altitudinal temperature gradients that control the regional and altitudinal zonation of vegetation. To discover if similar gradients existed during the Lateglacial and early

  10. 40 CFR 90.313 - Analyzers required.

    Science.gov (United States)

    2010-07-01

    ... of the exhaust gas at the sample probe is below 190 °C, the temperature of the valves, pipe work, and... temperature of the exhaust gas at the sample probe is above 190 °C, the temperature of the valves, pipe work... the HFID analyzer, the detector, oven, and sample-handling components within the oven must be suitable...

  11. Absence of genetic differentiation in the coral Pocillopora verrucosa along environmental gradients of the Saudi Arabian Red Sea

    KAUST Repository

    Robitzch, Vanessa S.N.

    2015-02-11

    The Red Sea is the world\\'s northernmost tropical sea. The 2000 km long, but narrow basin creates distinct environmental conditions along its latitudinal spread. The Red Sea displays a pronounced salinity gradient from 41 to 37 PSU (north to south) with an opposing temperature gradient from 21 to 27°C in the north to 27–33.8°C in the south. The Red Sea further displays a decreasing nutrient gradient from south to north that can also influence underwater light fields due to higher phytoplankton content and turbidity. Despite this strong variation in temperature, salinity, nutrients, and light conditions, the Red Sea supports large and diverse coral reef ecosystems along its nearly entire coastline. Only few studies have targeted whether these prevailing gradients affect genetic connectivity of reef organisms in the Red Sea. In this study, we sampled the abundant reef-building coral Pocillopora verrucosa from 10 reefs along a latitudinal gradient in the Red Sea covering an area of more than 850 km. We used nine Pocillopora microsatellite markers to assess the underlying population genetic structure and effective population size. To assure the exclusion of cryptic species, all analyzed specimens were chosen from a single mitochondrial lineage. Despite large distances between sampled regions covering pronounced, but smooth temperature and salinity gradients, no significant genetic population structure was found. Rather, our data indicate panmixia and considerable gene flow among regions. The absence of population subdivision driven by environmental factors and over large geographic distances suggests efficient larval dispersal and successful settlement of recruits from a wide range of reef sites. It also advocates, broadcast spawning as the main reproductive strategy of Pocillopora verrucosa in the Red Sea as reflected by the absence of clones in sampled colonies. These factors might explain the success of Pocillopora species throughout the Indo-Pacific and

  12. Absence of genetic differentiation in the coral Pocillopora verrucosa along environmental gradients of the Saudi Arabian Red Sea

    Directory of Open Access Journals (Sweden)

    Vanessa eRobitzch

    2015-02-01

    Full Text Available The Red Sea is the world’s northernmost tropical sea. The 2,000 km long, but narrow basin creates distinct environmental conditions along its latitudinal spread. The Red Sea displays a pronounced salinity gradient from 41 to 37 PSU (north to south with an opposing temperature gradient from 21-27°C in the north to 27-33.8°C in the south. The Red Sea further displays a decreasing nutrient gradient from south to north that can also influence underwater light fields due to higher phytoplankton content and turbidity. Despite this strong variation in temperature, salinity, nutrients, and light conditions, the Red Sea supports large and diverse coral reef ecosystems along its nearly entire coastline. Only few studies have targeted whether these prevailing gradients affect genetic connectivity of reef organisms in the Red Sea. In this study, we sampled the abundant reef-building coral Pocillopora verrucosa from ten reefs along a latitudinal gradient in the Red Sea covering an area of more than 850 km. We used nine Pocillopora microsatellite markers to assess the underlying population genetic structure and effective population size. To assure the exclusion of cryptic species, all analyzed specimens were chosen from a single mitochondrial lineage. Despite large distances between sampled regions covering pronounced, but smooth temperature and salinity gradients, no significant genetic population structure was found. Rather, our data indicate panmixia and considerable gene flow among regions. The absence of population subdivision driven by environmental factors and over large geographic distances suggests efficient larval dispersal and successful settlement of recruits from a wide range of reef sites. It also advocates, broadcast spawning as the main reproductive strategy of Pocillopora verrucosa in the Red Sea as reflected by the absence of clones in sampled colonies. These factors might explain the success of Pocillopora species throughout the Indo

  13. DOG optical gas analyzers

    Energy Technology Data Exchange (ETDEWEB)

    Azbukin, A.A.; Buldakov, M.A.; Korolev, B.V.; Korolo' kov, V.A.; Matrosov, I.I. [Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation). Inst. of Optical Monitoring

    2002-01-01

    Stationary gas analyzers for continuous monitoring of sulfur and nitrogen oxides in exhaust gases of electric power plants burning fossil fuels have been developed. The DOG series of gas-analyzers use non-laser UV radiation sources and the differential absorption lidar (DIAL) measurement technique. Operation of the gas-analyzers at Russian electric power plants showed their high efficiency, reliability, and easiness in operation at lower cost as compared to similar foreign devices. 8 refs., 3 figs., 1 tab.

  14. Universal MOSFET parameter analyzer

    Science.gov (United States)

    Klekachev, A. V.; Kuznetsov, S. N.; Pikulev, V. B.; Gurtov, V. A.

    2006-05-01

    MOSFET analyzer is developed to extract most important parameters of transistors. Instead of routine DC transfer and output characteristics, analyzer provides an evaluation of interface states density by applying charge pumping technique. There are two features that outperform the analyzer among similar products of other vendors. It is compact (100 × 80 × 50 mm 3 in dimensions) and lightweight (instrument with ultra low power supply (instrument was designed on the base of component parts from CYPRESS and ANALOG DEVICES (USA).

  15. Method of thermal derivative gradient analysis (TDGA

    Directory of Open Access Journals (Sweden)

    M. Cholewa

    2009-07-01

    Full Text Available In this work a concept of thermal analysis was shown, using for crystallization kinetics description the temperature derivatives after time and direction. Method of thermal derivative gradient analysis (TDGA is assigned for alloys and metals investigation as well as cast composites in range of solidification. The construction and operation characteristics were presented for the test stand including processing modules and probes together with thermocouples location. Authors presented examples of results interpretation for AlSi11 alloy castings with diversified wall thickness and at different pouring temperature.

  16. Simultaneous and Gradient IPN of Polyurethane/Vinyl Ester Resin: Morphology and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Dongyan Tang

    2009-01-01

    Full Text Available A series of polyurethane (PU and vinyl ester resin (VER simultaneous and gradient interpenetrating polymer networks (represented as s-IPN and g-IPN, resp. curing at room temperature were prepared by changing the component ratios of PU or VER in s-IPN, time intervals, and component ratio sequences of s-IPN in g-IPN. The microstructures of s-IPN and g-IPN were detected by atomic force microscope (AFM, dynamic mechanical analyzer (DMA, and surface constitution scanning of nitrogen element of energy dispersive X-ray spectrum (EDX, respectively. The mechanical properties of s-IPN and g-IPN were studied by values in strain-stress curves detected by electronic multipurpose tester. The results indicated that the morphology and mechanical properties are both affected by PU/VER component ratios in s-IPN, gradient time intervals, and gradient component ratio sequences. Furthermore, the morphology detection by EDX and mechanical properties study both proved the formation of gradient structures in transition regions of g-IPN.

  17. Analyzing Peace Pedagogies

    Science.gov (United States)

    Haavelsrud, Magnus; Stenberg, Oddbjorn

    2012-01-01

    Eleven articles on peace education published in the first volume of the Journal of Peace Education are analyzed. This selection comprises peace education programs that have been planned or carried out in different contexts. In analyzing peace pedagogies as proposed in the 11 contributions, we have chosen network analysis as our method--enabling…

  18. Gearbox vibration diagnostic analyzer

    Science.gov (United States)

    1992-01-01

    This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.

  19. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  20. Vegetation phenology gradients along the west and east coasts of Greenland from 2001 to 2015

    DEFF Research Database (Denmark)

    Karami, Mojtaba; Hansen, Birger Ulf; Westergaard-Nielsen, Andreas

    2017-01-01

    The objective of this paper is to characterize the spatiotemporal variations of vegetation phenology along latitudinal and altitudinal gradients in Greenland, and to examine local and regional climatic drivers. Time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed...... to obtain various phenological metrics for the period 2001–2015. MODIS-derived land surface temperatures were corrected for the sampling biases caused by cloud cover. Results indicate significant differences between West and East Greenland, in terms of both observed phenology during the study period...

  1. Analyzing in the present

    DEFF Research Database (Denmark)

    Revsbæk, Line; Tanggaard, Lene

    2015-01-01

    The article presents a notion of “analyzing in the present” as a source of inspiration in analyzing qualitative research materials. The term emerged from extensive listening to interview recordings during everyday commuting to university campus. Paying attention to the way different parts...... of various interviews conveyed diverse significance to the listening researcher at different times became a method of continuously opening up the empirical material in a reflexive, breakdown-oriented process of analysis. We argue that situating analysis in the present of analyzing emphasizes and acknowledges...

  2. A Fixed-Point of View on Gradient Methods for Big Data

    Directory of Open Access Journals (Sweden)

    Alexander Jung

    2017-09-01

    Full Text Available Interpreting gradient methods as fixed-point iterations, we provide a detailed analysis of those methods for minimizing convex objective functions. Due to their conceptual and algorithmic simplicity, gradient methods are widely used in machine learning for massive data sets (big data. In particular, stochastic gradient methods are considered the de-facto standard for training deep neural networks. Studying gradient methods within the realm of fixed-point theory provides us with powerful tools to analyze their convergence properties. In particular, gradient methods using inexact or noisy gradients, such as stochastic gradient descent, can be studied conveniently using well-known results on inexact fixed-point iterations. Moreover, as we demonstrate in this paper, the fixed-point approach allows an elegant derivation of accelerations for basic gradient methods. In particular, we will show how gradient descent can be accelerated by a fixed-point preserving transformation of an operator associated with the objective function.

  3. Brine migration in salt in a thermal gradient

    Science.gov (United States)

    Kang, M.; Lerche, M.; Lesher, C. E.

    2015-12-01

    Salt deposits have long been considered viable repositories for long-term storage of high-level nuclear waste. However, brine trapped in salt tends to migrate up thermal gradients, such as can develop around radioactive waste storage containers, potentially promoting corrosion of containment structures. Brine inclusions move up the temperature gradient through the three main steps: 1) the dissolution of salt at the hot side of the inclusion caused by increased salt solubility, 2) ordinary and thermal diffusion of dissolved salt ions within the inclusion, and 3) precipitation of salt at the cold side of the inclusion due to local supersaturation. This process of brine transport through salt under a thermal gradient is generally referred to as thermal migration. Here we investigated thermal migration of brine inclusion in salts for a wide range of mean temperatures (~ 50 °C to ~200 °C) and temperature gradients (~ 10 °C/cm to ~57 °C/cm). With time brine inclusions moving towards the heat source become elongated parallel to the thermal gradient. We quantified the rate of brine migration as a function of mean temperature and thermal gradient using time-lapse optical microscope. X -ray and neutron tomography were used to visualize and quantify 3D spatial distribution of brine inclusion in a salt crystal at different stages of thermal migration. Migration velocities are shown to increase with temperature, temperature gradient and size of inclusion. We find an abrupt increase in migration velocity at certain time steps of thermal migration. Migration velocities of brine inclusions ranged from 0.1 m/year to 30.7 m/year. Empirical equations at different velocity regions for brine inclusions were obtained by fitting exponential equations to the experimental data with high coefficient of determination values (R2> 0.94).The experimental results are in good agreement with the theoretical migration rates obtained using a previous analytical model.

  4. Software Design Analyzer System

    Science.gov (United States)

    Tausworthe, R. C.

    1985-01-01

    CRISP80 software design analyzer system a set of programs that supports top-down, hierarchic, modular structured design, and programing methodologies. CRISP80 allows for expression of design as picture of program.

  5. Miniature mass analyzer

    CERN Document Server

    Cuna, C; Lupsa, N; Cuna, S; Tuzson, B

    2003-01-01

    The paper presents the concept of different mass analyzers that were specifically designed as small dimension instruments able to detect with great sensitivity and accuracy the main environmental pollutants. The mass spectrometers are very suited instrument for chemical and isotopic analysis, needed in environmental surveillance. Usually, this is done by sampling the soil, air or water followed by laboratory analysis. To avoid drawbacks caused by sample alteration during the sampling process and transport, the 'in situ' analysis is preferred. Theoretically, any type of mass analyzer can be miniaturized, but some are more appropriate than others. Quadrupole mass filter and trap, magnetic sector, time-of-flight and ion cyclotron mass analyzers can be successfully shrunk, for each of them some performances being sacrificed but we must know which parameters are necessary to be kept unchanged. To satisfy the miniaturization criteria of the analyzer, it is necessary to use asymmetrical geometries, with ion beam obl...

  6. Dynamics of Chemotactic Droplets in Salt Concentration Gradients

    DEFF Research Database (Denmark)

    Cejkova, J.; Novak, M.; Stepanek, F.

    2014-01-01

    The chemotactic movement of decanol droplets in aqueous solutions of sodium decanoate in response to concentration gradients of NaCl has been investigated. Key parameters of the chemotactic response, namely the induction time and the migration velocity, have been evaluated as a function of the so...... of movement repeatedly, to carry and release a chemically reactive cargo, to select a stronger concentration gradient from two options, and to initiate chemotaxis by an external temperature stimulus have been demonstrated....

  7. Link between convection and meridional gradient of sea surface ...

    Indian Academy of Sciences (India)

    We use daily satellite estimates of sea surface temperature (SST)and rainfall during 1998 –2005 to show that onset of convection over the central Bay of Bengal (88-92°E, 14-18°N)during the core summer monsoon (mid-May to September)is linked to the meridional gradient of SST in the bay.The SST gradient was ...

  8. Natural gas production and anomalous geothermal gradients of the deep Tuscaloosa Formation

    Science.gov (United States)

    Burke, Lauri

    2011-01-01

    For the largest producing natural gas fields in the onshore Gulf of Mexico Basin, the relation between temperature versus depth was investigated. Prolific natural gas reservoirs with the highest temperatures were found in the Upper Cretaceous downdip Tuscaloosa trend in Louisiana. Temperature and production trends from the deepest field, Judge Digby field, in Pointe Coupe Parish, Louisiana, were investigated to characterize the environment of natural gas in the downdip Tuscaloosa trend. The average production depth in the Judge Digby field is approximately 22,000 ft. Temperatures as high as 400 degrees F are typically found at depth in Judge Digby field and are anomalously low when compared to temperature trends extrapolated to similar depths regionally. At 22,000 ft, the minimum and maximum temperatures for all reservoirs in Gulf Coast producing gas fields are 330 and 550 degrees F, respectively; the average temperature is 430 degrees F. The relatively depressed geothermal gradients in the Judge Digby field may be due to high rates of sediment preservation, which may have delayed the thermal equilibration of the sediment package with respect to the surrounding rock. Analyzing burial history and thermal maturation indicates that the deep Tuscaloosa trend in the Judge Digby field is currently in the gas generation window. Using temperature trends as an exploration tool may have important implications for undiscovered hydrocarbons at greater depths in currently producing reservoirs, and for settings that are geologically analogous to the Judge Digby fiel

  9. Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland

    Directory of Open Access Journals (Sweden)

    F. Bocquet

    2011-10-01

    Full Text Available A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April–August 2004 of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower measurements of (a ozone gradients measured by commercial ultraviolet absorption analyzers, (b ambient temperature gradients using aspirated thermocouple sensors, and (c wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 × 10−3μg m−2 s−1, respectively ∼0.01 cm s−1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach was on the order of 10−2 cm s−1. This uncertainty typically accounted to ~20–100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and spring-versus-summer dependencies.

  10. Strain gradients in epitaxial ferroelectrics

    NARCIS (Netherlands)

    Catalan, G; Noheda, Beatriz; McAneney, J; Sinnamon, LJ; Gregg, JM

    2005-01-01

    X-ray analysis of ferroelectric thin layers of Ba1/2Sr1/2TiO3 with different thicknesses reveals the presence of strain gradients across the films and allows us to propose a functional form for the internal strain profile. We use this to calculate the influence of strain gradient, through

  11. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...

  12. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  13. Americal options analyzed differently

    NARCIS (Netherlands)

    Nieuwenhuis, J.W.

    2003-01-01

    In this note we analyze in a discrete-time context and with a finite outcome space American options starting with the idea that every tradable should be a martingale under a certain measure. We believe that in this way American options become more understandable to people with a good working

  14. Analyzing Stereotypes in Media.

    Science.gov (United States)

    Baker, Jackie

    1996-01-01

    A high school film teacher studied how students recognized messages in film, examining how film education could help students identify and analyze racial and gender stereotypes. Comparison of students' attitudes before and after the film course found that the course was successful in raising students' consciousness. (SM)

  15. Gradient elution in capillary electrochromatography

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

  16. Gradient zone boundary control in salt gradient solar ponds

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Downers Grove, IL)

    1984-01-01

    A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.

  17. Effects of ventilation-heating control strategies for early weaning pig barns on energy consumption and 3-D temperature distributions

    Energy Technology Data Exchange (ETDEWEB)

    Choiniere, Y. [Les Consultants Yves Choiniere, St-Cesaire, PQ (Canada); Laberge, B. [Thevco Electronique Inc., St-Hubert, PQ (Canada)

    1995-07-01

    A ventilation control chamber was built for a modern livestock barn at Alfred College to measure temperature distribution, humidity, and propane and electricity consumption. Performance of the control systems on ambient temperature distribution and energy consumption was analyzed. Tests were conducted with and without recirculation ducts. Results showed that the use of recirculation ducts reduced the floor to ceiling temperature gradients. Propane consumption was reduced by 20 per cent with the use of the recirculation duct. 3 tabs., 11 figs.

  18. Ecosystem-Wide Morphological Structure of Leaf-Litter Ant Communities along a Tropical Latitudinal Gradient

    Science.gov (United States)

    Silva, Rogério R.; Brandão, Carlos Roberto F.

    2014-01-01

    General principles that shape community structure can be described based on a functional trait approach grounded on predictive models; increased attention has been paid to factors accounting for the functional diversity of species assemblages and its association with species richness along environmental gradients. We analyze here the interaction between leaf-litter ant species richness, the local communities' morphological structure and fundamental niche within the context of a northeast-southeast latitudinal gradient in one of the world's most species-rich ecosystems, the Atlantic Forest, representing 2,700 km of tropical rainforest along almost 20o of latitude in eastern Brazil. Our results are consistent with an ecosystem-wide pattern in communities' structure, with relatively high species turnover but functionally analogous leaf-litter ant communities' organization. Our results suggest directional shifts in the morphological space along the environmental gradient from overdispersed to aggregated (from North to South), suggesting that primary productivity and environmental heterogeneity (altitude, temperature and precipitation in the case) determine the distribution of traits and regulate the assembly rules, shaping local leaf-litter ant communities. Contrary to the expected and most common pattern along latitudinal gradients, the Atlantic Forest leaf litter ant communities show an inverse pattern in richness, that is, richer communities in higher than in lower latitudes. The morphological specialization of communities showed more morphologically distinct communities at low latitudes and species redundancy at high latitudes. We claim that an inverse latitudinal gradient in primary productivity and environmental heterogeneity across the Atlantic forest may affect morphological diversity and species richness, enhancing species coexistence mechanisms, and producing thus the observed patterns. We suggest that a functional framework based on flexible enough traits

  19. Ecosystem-wide morphological structure of leaf-litter ant communities along a tropical latitudinal gradient.

    Science.gov (United States)

    Silva, Rogério R; Brandão, Carlos Roberto F

    2014-01-01

    General principles that shape community structure can be described based on a functional trait approach grounded on predictive models; increased attention has been paid to factors accounting for the functional diversity of species assemblages and its association with species richness along environmental gradients. We analyze here the interaction between leaf-litter ant species richness, the local communities' morphological structure and fundamental niche within the context of a northeast-southeast latitudinal gradient in one of the world's most species-rich ecosystems, the Atlantic Forest, representing 2,700 km of tropical rainforest along almost 20° of latitude in eastern Brazil. Our results are consistent with an ecosystem-wide pattern in communities' structure, with relatively high species turnover but functionally analogous leaf-litter ant communities' organization. Our results suggest directional shifts in the morphological space along the environmental gradient from overdispersed to aggregated (from North to South), suggesting that primary productivity and environmental heterogeneity (altitude, temperature and precipitation in the case) determine the distribution of traits and regulate the assembly rules, shaping local leaf-litter ant communities. Contrary to the expected and most common pattern along latitudinal gradients, the Atlantic Forest leaf litter ant communities show an inverse pattern in richness, that is, richer communities in higher than in lower latitudes. The morphological specialization of communities showed more morphologically distinct communities at low latitudes and species redundancy at high latitudes. We claim that an inverse latitudinal gradient in primary productivity and environmental heterogeneity across the Atlantic forest may affect morphological diversity and species richness, enhancing species coexistence mechanisms, and producing thus the observed patterns. We suggest that a functional framework based on flexible enough traits

  20. Ecosystem-wide morphological structure of leaf-litter ant communities along a tropical latitudinal gradient.

    Directory of Open Access Journals (Sweden)

    Rogério R Silva

    Full Text Available General principles that shape community structure can be described based on a functional trait approach grounded on predictive models; increased attention has been paid to factors accounting for the functional diversity of species assemblages and its association with species richness along environmental gradients. We analyze here the interaction between leaf-litter ant species richness, the local communities' morphological structure and fundamental niche within the context of a northeast-southeast latitudinal gradient in one of the world's most species-rich ecosystems, the Atlantic Forest, representing 2,700 km of tropical rainforest along almost 20° of latitude in eastern Brazil. Our results are consistent with an ecosystem-wide pattern in communities' structure, with relatively high species turnover but functionally analogous leaf-litter ant communities' organization. Our results suggest directional shifts in the morphological space along the environmental gradient from overdispersed to aggregated (from North to South, suggesting that primary productivity and environmental heterogeneity (altitude, temperature and precipitation in the case determine the distribution of traits and regulate the assembly rules, shaping local leaf-litter ant communities. Contrary to the expected and most common pattern along latitudinal gradients, the Atlantic Forest leaf litter ant communities show an inverse pattern in richness, that is, richer communities in higher than in lower latitudes. The morphological specialization of communities showed more morphologically distinct communities at low latitudes and species redundancy at high latitudes. We claim that an inverse latitudinal gradient in primary productivity and environmental heterogeneity across the Atlantic forest may affect morphological diversity and species richness, enhancing species coexistence mechanisms, and producing thus the observed patterns. We suggest that a functional framework based on

  1. The temperature and precipitation reconstructions on Swiss stalagmites with a special emphasis on altitude gradient using noble-gases, δO-18 and δD of fluid inclusions

    Science.gov (United States)

    Ghadiri, Elaheh; Brennwald, Matthias; Kipfer, Rolf

    2017-04-01

    We present the results of an application of 'Combined Vacuum Crushing and Sieving (CVCS)' system (e.g., allowing to crush samples to defined grain size in vacuum) for the first time to stalagmites grown in cold climates during the last glacial-interglacial transition, but at different altitudes. Recently, concentrations of dissolved atmospheric noble gases in fluid inclusions of stalagmites were used to reconstruct past ambient cave temperatures, the annual mean temperature and hydrological conditions when the water was trapped. To reconstruct temperatures from noble gases (noble gas temperature: NGT) in water-filled inclusions, we processed samples from Swiss stalagmites M6 from Milandre cave (400 m.a.s.l) and GEF1 from Grotte aux Fées cave (895 m.a.s.l) covering the climatic transitions Allerød-Younger Dryas-Holocene. Water content. The amount of water extracted per unit mass of calcite fabric (e.g., 'water yield': WT) was shown to be a measure of the total water content. The data shows that the WT systematically changes with δ18Ocalcite of the calcite. We therefore conclude that WT records can be linked on changes in drip rates and thus can be used to track changes of past precipitation even in cold regions. Noble gases. Noble gas analysis shows that the annual mean temperatures in Milandre cave were 2.2±2.0°C during the late Allerød and dropped to 0±2°C at the Younger Dryas. Such temperatures close 0°C indicate that drip water supply stopped in response to the formation of permafrost conditions around the cave preventing further stalagmite growth. However, one late Holocene sample gave a cave temperature of 8.7±1.4°C agreeing generally with present day annual mean temperature. The annual mean temperature of 5.7±1.3°C from GEF1 was determined for the early Holocene. The observed data show systematic variations with sample elevation, e.g., higher temperature from lower altitude and vice versa. Combining the isotopic composition of water in fluid

  2. Controls on ecosystem and root respiration across a permafrost and wetland gradient in interior Alaska

    Science.gov (United States)

    McConnell, Nicole A.; Turetsky, Merritt R.; McGuire, A. David; Kane, Evan S.; Waldrop, Mark P.; Harden, Jennifer W.

    2013-01-01

    Permafrost is common to many northern wetlands given the insulation of thick organic soil layers, although soil saturation in wetlands can lead to warmer soils and increased thaw depth. We analyzed five years of soil CO2 fluxes along a wetland gradient that varied in permafrost and soil moisture conditions. We predicted that communities with permafrost would have reduced ecosystem respiration (ER) but greater temperature sensitivity than communities without permafrost. These predictions were partially supported. The colder communities underlain by shallow permafrost had lower ecosystem respiration (ER) than communities with greater active layer thickness. However, the apparent Q10 of monthly averaged ER was similar in most of the vegetation communities except the rich fen, which had smaller Q10 values. Across the gradient there was a negative relationship between water table position and apparent Q10, showing that ER was more temperature sensitive under drier soil conditions. We explored whether root respiration could account for differences in ER between two adjacent communities (sedge marsh and rich fen), which corresponded to the highest and lowest ER, respectively. Despite differences in root respiration rates, roots contributed equally (~40%) to ER in both communities. Also, despite similar plant biomass, ER in the rich fen was positively related to root biomass, while ER in the sedge marsh appeared to be related more to vascular green area. Our results suggest that ER across this wetland gradient was temperature-limited, until conditions became so wet that respiration became oxygen-limited and influenced less by temperature. But even in sites with similar hydrology and thaw depth, ER varied significantly likely based on factors such as soil redox status and vegetation composition.

  3. Ocular Response Analyzer

    OpenAIRE

    Kaushik, Sushmita; Pandav, Surinder Singh

    2012-01-01

    Until recently, corneal biomechanical properties could not be measured in vivo. The ocular response analyzer is a new, noninvasive device that analyses corneal biomechanical properties simply and rapidly. The ORA allows cornea compensated IOP measurements and can estimate corneal hysteresis (CH) and corneal resistance factor (CRF). It is designed to improve the accuracy of IOP measurement by using corneal biomechanical data to calculate a biomechanically adjusted estimate of intraocular press...

  4. Analyzing sustainable competitive advantage

    OpenAIRE

    Abdul Malek Nurul Aida; Shahzad Khuram; Takala Josu; Bojnec Stefan; Papler Drago; Liu Yang

    2016-01-01

    In today’s dynamic business environment, a key challenge for all companies is to make adaptive adjustments to their manufacturing strategy. This study demonstrates the competitive priorities of manufacturing strategy in hydro-power case company to evaluate the level of sustainable competitive advantage and also to further analyze how business strategies are aligned with manufacturing strategies. This research is based on new holistic analytical evaluation of manufacturing strategy index, sens...

  5. MODIFIED ARMIJO RULE ON GRADIENT DESCENT AND CONJUGATE GRADIENT

    Directory of Open Access Journals (Sweden)

    ZURAIDAH FITRIAH

    2017-10-01

    Full Text Available Armijo rule is an inexact line search method to determine step size in some descent method to solve unconstrained local optimization. Modified Armijo was introduced to increase the numerical performance of several descent algorithms that applying this method. The basic difference of Armijo and its modified are in existence of a parameter and estimating the parameter that is updated in every iteration. This article is comparing numerical solution and time of computation of gradient descent and conjugate gradient hybrid Gilbert-Nocedal (CGHGN that applying modified Armijo rule. From program implementation in Matlab 6, it's known that gradient descent was applying modified Armijo more effectively than CGHGN from one side: iteration needed to reach some norm of the gradient  (input by the user. The amount of iteration was representing how long the step size of each algorithm in each iteration. In another side, time of computation has the same conclusion.

  6. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination......We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...

  7. High-thermal-gradient Superalloy Crystal Growth

    Science.gov (United States)

    Pearson, D. D.; Anton, D. L.; Giamei, A. F.

    1985-01-01

    Single, (001)-oriented crystals of PWA 1480 were processed in alumina/silica shell molds in a laboratory high gradient furnace. The furnace employs a graphite resistance heated element, a radiation baffle, and a water cooled radiation trap below the baffle. All crystals were grown in vacuum (10 torr) and all heat transfer was radiative. The element is constructed with a variable cross section that is tapered just above the baffle to maximize heat input and therefore thermal gradient. A maximum alloy temperature of 1600 C was used. A thermal gradient of 130 deg C/cm was recorded at 1370 C just above the solidus of the PWA 1480 alloys. Crystal bars with 14.4 and 17.5 mm diameters were grown in alumina/silica shell molds. Each crystal was started from a 1.6 mm pencil seed at a rate of 76 mm/hr and slowly accelerated to a rate of 200 mm/hr under computer control. Volume percent porosity and average pore size were measured as functions of distance in representative bars. Low cycle fatigue behavior and stress rupture properties were determined.

  8. Inductive dielectric analyzer

    Science.gov (United States)

    Agranovich, Daniel; Polygalov, Eugene; Popov, Ivan; Ben Ishai, Paul; Feldman, Yuri

    2017-03-01

    One of the approaches to bypass the problem of electrode polarization in dielectric measurements is the free electrode method. The advantage of this technique is that, the probing electric field in the material is not supplied by contact electrodes, but rather by electromagnetic induction. We have designed an inductive dielectric analyzer based on a sensor comprising two concentric toroidal coils. In this work, we present an analytic derivation of the relationship between the impedance measured by the sensor and the complex dielectric permittivity of the sample. The obtained relationship was successfully employed to measure the dielectric permittivity and conductivity of various alcohols and aqueous salt solutions.

  9. Seismic Velocity Gradients Across the Transition Zone

    Science.gov (United States)

    Escalante, C.; Cammarano, F.; de Koker, N.; Piazzoni, A.; Wang, Y.; Marone, F.; Dalton, C.; Romanowicz, B.

    2006-12-01

    One-D elastic velocity models derived from mineral physics do a notoriously poor job at predicting the velocity gradients in the upper mantle transition zone, as well as some other features of models derived from seismological data. During the 2006 CIDER summer program, we computed Vs and Vp velocity profiles in the upper mantle based on three different mineral physics approaches: two approaches based on the minimization of Gibbs Free Energy (Stixrude and Lithgow-Bertelloni, 2005; Piazzoni et al., 2006) and one obtained by using experimentally determined phase diagrams (Weidner and Wang, 1998). The profiles were compared by assuming a vertical temperature profile and two end-member compositional models, the pyrolite model of Ringwood (1979) and the piclogite model of Anderson and Bass (1984). The predicted seismic profiles, which are significantly different from each other, primarily due to different choices of properties of single minerals and their extrapolation with temperature, are tested against a global dataset of P and S travel times and spheroidal and toroidal normal mode eigenfrequencies. All the models derived using a potential temperature of 1600K predict seismic velocities that are too slow in the upper mantle, suggesting the need to use a colder geotherm. The velocity gradient in the transition zone is somewhat better for piclogite than for pyrolite, possibly indicating the need to increase Ca content. The presence of stagnant slabs in the transition zone is a possible explanation for the need for 1) colder temperature and 2) increased Ca content. Future improvements in seismic profiles obtained from mineral physics will arise from better knowledge of elastic properties of upper mantle constituents and aggregates at high temperature and pressure, a better understanding of differences between thermodynamic models, and possibly the effect of water through and on Q. High resolution seismic constraints on velocity jumps at 400 and 660 km also need to be

  10. Field Deployable DNA analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, E; Christian, A; Marion, J; Sorensen, K; Arroyo, E; Vrankovich, G; Hara, C; Nguyen, C

    2005-02-09

    This report details the feasibility of a field deployable DNA analyzer. Steps for swabbing cells from surfaces and extracting DNA in an automatable way are presented. Since enzymatic amplification reactions are highly sensitive to environmental contamination, sample preparation is a crucial step to make an autonomous deployable instrument. We perform sample clean up and concentration in a flow through packed bed. For small initial samples, whole genome amplification is performed in the packed bed resulting in enough product for subsequent PCR amplification. In addition to DNA, which can be used to identify a subject, protein is also left behind, the analysis of which can be used to determine exposure to certain substances, such as radionuclides. Our preparative step for DNA analysis left behind the protein complement as a waste stream; we determined to learn if the proteins themselves could be analyzed in a fieldable device. We successfully developed a two-step lateral flow assay for protein analysis and demonstrate a proof of principle assay.

  11. Ring Image Analyzer

    Science.gov (United States)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  12. Geothermal gradient drilling, north-central Cascades of Oregon, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Youngquist, W.

    1980-01-01

    A geothermal gradient drilling program was conducted on the western flank of the north-central Cascade Mountains in Oregon. Six wells were drilled during this program, although in effect seven were drilled, as two wells were drilled at site 3, the second well, however, actually going to a lesser depth than the first. Three of the wells (3, 4, and 5) were drilled in areas which topographically are subject to strong throughflows of ground water. None of these wells reached the regional water table, and all showed essentially isothermal geothermal gradients. The single well which was started essentially at the water table (well 6) shows a linear temperature rise with depth essentially from the top of the well bore. Well No. 2 shows an isothermal gradient down to the level of the regional water table and then shows a linear gradient of about 70/sup 0/C/km from the regional water table to total depth.

  13. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, John William

    1997-01-01

    A Sobolev gradient of a real-valued functional is a gradient of that functional taken relative to the underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. Equal emphasis is placed on numerical and theoretical matters. Several concrete applications are made to illustrate the method. These applications include (1) Ginzburg-Landau functionals of superconductivity, (2) problems of transonic flow in which type depends locally on nonlinearities, and (3) minimal surface problems. Sobolev gradient constructions rely on a study of orthogonal projections onto graphs of closed densely defined linear transformations from one Hilbert space to another. These developments use work of Weyl, von Neumann and Beurling.

  14. Graded/Gradient Porous Biomaterials

    Directory of Open Access Journals (Sweden)

    Xigeng Miao

    2009-12-01

    Full Text Available Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

  15. Analyzing complicity in risk.

    Science.gov (United States)

    Busby, Jerry

    2008-12-01

    When risks generate anger rather than fear, there is at least someone who regards the imposition of those risks as wrongdoing; and it then makes sense to speak of the involvement in producing those risks as complicity. It is particularly relevant to examine the complicity of risk bearers, because this is likely to have a strong influence on how far other actors should go in providing them with protection. This article makes a case for analyzing complicity explicitly, in parallel with normal processes of risk assessment, and proposes a framework for this analysis. It shows how it can be applied in a case study of maritime transportation, and examines the practical and theoretical difficulties of this kind of analysis. The conclusion is that the analysis has to be formative rather than summative, but that it could provide a useful way of exposing differences in the assumptions of different actors about agency and responsibility.

  16. PhosphoSiteAnalyzer

    DEFF Research Database (Denmark)

    Bennetzen, Martin V; Cox, Jürgen; Mann, Matthias

    2012-01-01

    Phosphoproteomic experiments are routinely conducted in laboratories worldwide, and because of the fast development of mass spectrometric techniques and efficient phosphopeptide enrichment methods, researchers frequently end up having lists with tens of thousands of phosphorylation sites...... for further interrogation. To answer biologically relevant questions from these complex data sets, it becomes essential to apply computational, statistical, and predictive analytical methods. Here we provide an advanced bioinformatic platform termed "PhosphoSiteAnalyzer" to explore large phosphoproteomic data...... an algorithm to retrieve kinase predictions from the public NetworKIN webpage in a semiautomated way and applies hereafter advanced statistics to facilitate a user-tailored in-depth analysis of the phosphoproteomic data sets. The interface of the software provides a high degree of analytical flexibility...

  17. System performance analyzer

    Science.gov (United States)

    Helbig, H. R.

    1981-01-01

    The System Performance Analyzer (SPA) designed to provide accurate real time information about the operation of complex systems and developed for use on the Airborne Data Analysis/Monitor System (ADAMS), a ROLM 1666 based system is described. The system uses an external processor to operate an intelligent, simulated control panel. Also provided are functions to trace operations, determine frequency of use of memory areas, and time or count user tasks in a multitask environment. This augments the information available from the standard debugger and control panel, and reduces the time and effort needed by ROLM 1666 users in optimizing their system, as well as providing documentation of the effect of any changes. The operation and state of the system are evaluated.

  18. PDA: Pooled DNA analyzer

    Directory of Open Access Journals (Sweden)

    Lin Chin-Yu

    2006-04-01

    Full Text Available Abstract Background Association mapping using abundant single nucleotide polymorphisms is a powerful tool for identifying disease susceptibility genes for complex traits and exploring possible genetic diversity. Genotyping large numbers of SNPs individually is performed routinely but is cost prohibitive for large-scale genetic studies. DNA pooling is a reliable and cost-saving alternative genotyping method. However, no software has been developed for complete pooled-DNA analyses, including data standardization, allele frequency estimation, and single/multipoint DNA pooling association tests. This motivated the development of the software, 'PDA' (Pooled DNA Analyzer, to analyze pooled DNA data. Results We develop the software, PDA, for the analysis of pooled-DNA data. PDA is originally implemented with the MATLAB® language, but it can also be executed on a Windows system without installing the MATLAB®. PDA provides estimates of the coefficient of preferential amplification and allele frequency. PDA considers an extended single-point association test, which can compare allele frequencies between two DNA pools constructed under different experimental conditions. Moreover, PDA also provides novel chromosome-wide multipoint association tests based on p-value combinations and a sliding-window concept. This new multipoint testing procedure overcomes a computational bottleneck of conventional haplotype-oriented multipoint methods in DNA pooling analyses and can handle data sets having a large pool size and/or large numbers of polymorphic markers. All of the PDA functions are illustrated in the four bona fide examples. Conclusion PDA is simple to operate and does not require that users have a strong statistical background. The software is available at http://www.ibms.sinica.edu.tw/%7Ecsjfann/first%20flow/pda.htm.

  19. Smoothed Analysis for the Conjugate Gradient Algorithm

    Science.gov (United States)

    Menon, Govind; Trogdon, Thomas

    2016-11-01

    The purpose of this paper is to establish bounds on the rate of convergence of the conjugate gradient algorithm when the underlying matrix is a random positive definite perturbation of a deterministic positive definite matrix. We estimate all finite moments of a natural halting time when the random perturbation is drawn from the Laguerre unitary ensemble in a critical scaling regime explored in Deift et al. (2016). These estimates are used to analyze the expected iteration count in the framework of smoothed analysis, introduced by Spielman and Teng (2001). The rigorous results are compared with numerical calculations in several cases of interest.

  20. Gradient-index optics fundamentals and applications

    CERN Document Server

    Gomez-Reino, Carlos; Bao, Carmen

    2010-01-01

    Gradient-Index (GRIN) optics provides a comprehensive and thorough treatment on fundamentals and applications of light propagation through inhomogeneous media. The book can be used both as a classroom text for students in physics and engineering and as a reference for specialists. A description of the phenomena, components and technology used in GRIN Optics are presented. The relationship to lenses, waveguides, optical connections, spatial solitons and vision is demonstrated. Applications of GRIN components and hybrid structures for optical connections, optical sensing and Talbot effect are analyzed.

  1. Analysis of Gradient Waveform in Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    OU-YANG Shan-mei

    2017-12-01

    Full Text Available The accuracy of gradient pulse waveform affects image quality significantly in magnetic resonance imaging (MRI. Recording and analyzing the waveform of gradient pulse helps to make rapid and accurate diagnosis of spectrometer gradient hardware and/or pulse sequence. Using the virtual instrument software LabVIEW to control the high speed data acquisition card DAQ-2005, a multi-channel acquisition scheme was designed to collect the gradient outputs from a custom-made spectrometer. The collected waveforms were post-processed (i.e., histogram statistical analysis, data filtering and difference calculation to obtain feature points containing time and amplitude information. Experiments were carried out to validate the method, which is an auxiliary test method for the development of spectrometer and pulses sequence.

  2. Analyzing Spacecraft Telecommunication Systems

    Science.gov (United States)

    Kordon, Mark; Hanks, David; Gladden, Roy; Wood, Eric

    2004-01-01

    Multi-Mission Telecom Analysis Tool (MMTAT) is a C-language computer program for analyzing proposed spacecraft telecommunication systems. MMTAT utilizes parameterized input and computational models that can be run on standard desktop computers to perform fast and accurate analyses of telecommunication links. MMTAT is easy to use and can easily be integrated with other software applications and run as part of almost any computational simulation. It is distributed as either a stand-alone application program with a graphical user interface or a linkable library with a well-defined set of application programming interface (API) calls. As a stand-alone program, MMTAT provides both textual and graphical output. The graphs make it possible to understand, quickly and easily, how telecommunication performance varies with variations in input parameters. A delimited text file that can be read by any spreadsheet program is generated at the end of each run. The API in the linkable-library form of MMTAT enables the user to control simulation software and to change parameters during a simulation run. Results can be retrieved either at the end of a run or by use of a function call at any time step.

  3. Downhole Fluid Analyzer Development

    Energy Technology Data Exchange (ETDEWEB)

    Bill Turner

    2006-11-28

    A novel fiber optic downhole fluid analyzer has been developed for operation in production wells. This device will allow real-time determination of the oil, gas and water fractions of fluids from different zones in a multizone or multilateral completion environment. The device uses near infrared spectroscopy and induced fluorescence measurement to unambiguously determine the oil, water and gas concentrations at all but the highest water cuts. The only downhole components of the system are the fiber optic cable and windows. All of the active components--light sources, sensors, detection electronics and software--will be located at the surface, and will be able to operate multiple downhole probes. Laboratory testing has demonstrated that the sensor can accurately determine oil, water and gas fractions with a less than 5 percent standard error. Once installed in an intelligent completion, this sensor will give the operating company timely information about the fluids arising from various zones or multilaterals in a complex completion pattern, allowing informed decisions to be made on controlling production. The research and development tasks are discussed along with a market analysis.

  4. Bios data analyzer.

    Science.gov (United States)

    Sabelli, H; Sugerman, A; Kovacevic, L; Kauffman, L; Carlson-Sabelli, L; Patel, M; Konecki, J

    2005-10-01

    The Bios Data Analyzer (BDA) is a set of computer programs (CD-ROM, in Sabelli et al., Bios. A Study of Creation, 2005) for new time series analyses that detects and measures creative phenomena, namely diversification, novelty, complexes, nonrandom complexity. We define a process as creative when its time series displays these properties. They are found in heartbeat interval series, the exemplar of bios .just as turbulence is the exemplar of chaos, in many other empirical series (galactic distributions, meteorological, economic and physiological series), in biotic series generated mathematically by the bipolar feedback, and in stochastic noise, but not in chaotic attractors. Differencing, consecutive recurrence and partial autocorrelation indicate nonrandom causation, thereby distinguishing chaos and bios from random and random walk. Embedding plots distinguish causal creative processes (e.g. bios) that include both simple and complex components of variation from stochastic processes (e.g. Brownian noise) that include only complex components, and from chaotic processes that decay from order to randomness as the number of dimensions is increased. Varying bin and dimensionality show that entropy measures symmetry and variety, and that complexity is associated with asymmetry. Trigonometric transformations measure coexisting opposites in time series and demonstrate bipolar, partial, and uncorrelated opposites in empirical processes and bios, supporting the hypothesis that bios is generated by bipolar feedback, a concept which is at variance with standard concepts of polar and complementary opposites.

  5. Sensitivity of spring phenology to warming across temporal and spatial climate gradients in two independent databases

    Science.gov (United States)

    Cook, Benjamin I.; Wolkovich, Elizabeth M.; Davies, T. Jonathan; Ault, Toby R.; Betancourt, Julio L.; Allen, Jenica M.; Bolmgren, Kjell; Cleland, Elsa E.; Crimmins, Theresa M.; Kraft, Nathan J.B.; Lancaster, Lesley T.; Mazer, Susan J.; McCabe, Gregory J.; McGill, Brian J.; Parmesan, Camille; Pau, Stephanie; Regetz, James; Salamin, Nicolas; Schwartz, Mark D.; Travers, Steven E.

    2012-01-01

    Disparate ecological datasets are often organized into databases post hoc and then analyzed and interpreted in ways that may diverge from the purposes of the original data collections. Few studies, however, have attempted to quantify how biases inherent in these data (for example, species richness, replication, climate) affect their suitability for addressing broad scientific questions, especially in under-represented systems (for example, deserts, tropical forests) and wild communities. Here, we quantitatively compare the sensitivity of species first flowering and leafing dates to spring warmth in two phenological databases from the Northern Hemisphere. One—PEP725—has high replication within and across sites, but has low species diversity and spans a limited climate gradient. The other—NECTAR—includes many more species and a wider range of climates, but has fewer sites and low replication of species across sites. PEP725, despite low species diversity and relatively low seasonality, accurately captures the magnitude and seasonality of warming responses at climatically similar NECTAR sites, with most species showing earlier phenological events in response to warming. In NECTAR, the prevalence of temperature responders significantly declines with increasing mean annual temperature, a pattern that cannot be detected across the limited climate gradient spanned by the PEP725 flowering and leafing data. Our results showcase broad areas of agreement between the two databases, despite significant differences in species richness and geographic coverage, while also noting areas where including data across broader climate gradients may provide added value. Such comparisons help to identify gaps in our observations and knowledge base that can be addressed by ongoing monitoring and research efforts. Resolving these issues will be critical for improving predictions in understudied and under-sampled systems outside of the temperature seasonal mid-latitudes.

  6. Use of Ground Penetrating Radar to Study Gradient Media

    Science.gov (United States)

    Titov, A.

    2016-12-01

    Nowadays Ground Penetrating Radar (GPR) is often used to solve different problems of applied geophysics including the hydrological ones. This work was motivated by detection of weak reflections in the body of water observed during the surveys on the freshwater lakes using GPR. The same reflections were first analyzed by John Bradford in 2007. These reflections can arise from the thermal gradient layer or thermocline due to different dielectric permittivity of cold and warm water. We employed physical and mathematical modeling to identify the properties of such thermoclines. We have constructed a special GPR stand to study the gradient media in our laboratory. The stand consists of a water-filled plastic tank and plastic tubes, which gather the cold water under the warm water. Our stand allows for changing parameters of the gradient layer, such as limits of dielectric permittivity and the thickness of the gradient layer. GPR antenna was placed slightly under the water surface to remove the parasitic reflections. To visualize the thermal distribution, an infrared camera and thermal sensors were used. Analysis of the GPR traces after physical modeling, performed in the MATLAB environment, allows us to locate the weak reflection from the gradient layer. We observed that (i) the change of the gradient boundary values alters the amplitude of the signal, (ii) the arrival time of the impulse reflected from the gradient layer corresponds to the arrival time of the impulse reflected from the top boundary of this layer, and (iii) the shape of the signal reflected from the gradient layer coincides with the shape of the signal reflected from the non-gradient boundary between two bodies. The quantitative properties of thermocline can be determined using amplitude analysis of GPR signals. Finally, the developed methods were successfully applied to real field data.

  7. Digital Microfluidics Sample Analyzer

    Science.gov (United States)

    Pollack, Michael G.; Srinivasan, Vijay; Eckhardt, Allen; Paik, Philip Y.; Sudarsan, Arjun; Shenderov, Alex; Hua, Zhishan; Pamula, Vamsee K.

    2010-01-01

    Three innovations address the needs of the medical world with regard to microfluidic manipulation and testing of physiological samples in ways that can benefit point-of-care needs for patients such as premature infants, for which drawing of blood for continuous tests can be life-threatening in their own right, and for expedited results. A chip with sample injection elements, reservoirs (and waste), droplet formation structures, fluidic pathways, mixing areas, and optical detection sites, was fabricated to test the various components of the microfluidic platform, both individually and in integrated fashion. The droplet control system permits a user to control droplet microactuator system functions, such as droplet operations and detector operations. Also, the programming system allows a user to develop software routines for controlling droplet microactuator system functions, such as droplet operations and detector operations. A chip is incorporated into the system with a controller, a detector, input and output devices, and software. A novel filler fluid formulation is used for the transport of droplets with high protein concentrations. Novel assemblies for detection of photons from an on-chip droplet are present, as well as novel systems for conducting various assays, such as immunoassays and PCR (polymerase chain reaction). The lab-on-a-chip (a.k.a., lab-on-a-printed-circuit board) processes physiological samples and comprises a system for automated, multi-analyte measurements using sub-microliter samples of human serum. The invention also relates to a diagnostic chip and system including the chip that performs many of the routine operations of a central labbased chemistry analyzer, integrating, for example, colorimetric assays (e.g., for proteins), chemiluminescence/fluorescence assays (e.g., for enzymes, electrolytes, and gases), and/or conductometric assays (e.g., for hematocrit on plasma and whole blood) on a single chip platform.

  8. 98 . original article weight gradient and physiological responses

    African Journals Online (AJOL)

    User

    Goats, China) while their physical appearance, feed consumption, rectal temperature and behaviours were recorded daily. RESULTS. Weight gradient - The physiological responses of the rabbit's treatments with cation and subsequent challenge with. Salmonella enterica are shown in table 1 below. There was an.

  9. Soft Decision Analyzer

    Science.gov (United States)

    Steele, Glen; Lansdowne, Chatwin; Zucha, Joan; Schlensinger, Adam

    2013-01-01

    The Soft Decision Analyzer (SDA) is an instrument that combines hardware, firmware, and software to perform realtime closed-loop end-to-end statistical analysis of single- or dual- channel serial digital RF communications systems operating in very low signal-to-noise conditions. As an innovation, the unique SDA capabilities allow it to perform analysis of situations where the receiving communication system slips bits due to low signal-to-noise conditions or experiences constellation rotations resulting in channel polarity in versions or channel assignment swaps. SDA s closed-loop detection allows it to instrument a live system and correlate observations with frame, codeword, and packet losses, as well as Quality of Service (QoS) and Quality of Experience (QoE) events. The SDA s abilities are not confined to performing analysis in low signal-to-noise conditions. Its analysis provides in-depth insight of a communication system s receiver performance in a variety of operating conditions. The SDA incorporates two techniques for identifying slips. The first is an examination of content of the received data stream s relation to the transmitted data content and the second is a direct examination of the receiver s recovered clock signals relative to a reference. Both techniques provide benefits in different ways and allow the communication engineer evaluating test results increased confidence and understanding of receiver performance. Direct examination of data contents is performed by two different data techniques, power correlation or a modified Massey correlation, and can be applied to soft decision data widths 1 to 12 bits wide over a correlation depth ranging from 16 to 512 samples. The SDA detects receiver bit slips within a 4 bits window and can handle systems with up to four quadrants (QPSK, SQPSK, and BPSK systems). The SDA continuously monitors correlation results to characterize slips and quadrant change and is capable of performing analysis even when the

  10. Effect of Pressure Gradients on Plate Response and Radiation in a Supersonic Turbulent Boundary Layer

    Science.gov (United States)

    Frendi, Abdelkader

    1997-01-01

    Using the model developed by the author for zero-pressure gradient turbulent boundary layers, results are obtained for adverse and favorable pressure gradients. It is shown that when a flexible plate is located in an adverse pressure gradient area, it vibrates more than if it were in a favorable pressure gradient one. Therefore the noise generated by the plate in an adverse pressure gradient is much greater than that due to the plate in a favorable pressure gradient. The effects of Reynolds number and boundary layer thickness are also analyzed and found to have the same effect in both adverse and favorable pressure gradient cases. Increasing the Reynolds number is found to increase the loading on the plate and therefore acoustic radiation. An increase in boundary layer thickness is found to decrease the level of the high frequencies and therefore the response and radiation at these frequencies. The results are in good qualitative agreement with experimental measurements.

  11. Electron transfer across a thermal gradient.

    Science.gov (United States)

    Craven, Galen T; Nitzan, Abraham

    2016-08-23

    Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor-acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures.

  12. Human impact gradient on mammalian biodiversity

    Directory of Open Access Journals (Sweden)

    Mariana Munguía

    2016-04-01

    Full Text Available Drastic changes have been caused by human influence in natural landscapes, which may exert an intensive effect on species loss. However, species loss from human pressure is not random but depends on a series of environmentally associated factors. Linking species traits to environmental attributes may allow us to detect the ecological impacts of habitat so that meaningful habitat degradation gradients can be identified. The relationships between environmental factors and species traits provide the basis for identifying those biological traits that make species more sensitive to disturbance. These relationships are also helpful to detect the geographic distribution of latent risk to reveal areas where biodiversity is threatened. Here, we identify a “Human Impact Gradient for Biodiversity (HIGB” based on a three-table ordination method (RLQ analysis and fourth-corner analysis to identify key species traits that are associated with environmental gradient. Species distribution and environmental geographic data were gathered nationwide to analyze 68 localities, which represent 27% of Mexico’s surface, including 211 species of mammals. Nine environmental variables (including biophysical, geophysical and land-use impacts were analyzed by using the Geographic Information System. Three types of species’ traits were evaluated: locomotion, trophic habit and body size. We identified a human impact gradient, which was mainly determined by the percentage of the area that was covered by seedlings, the plant richness, the understory coverage percentage and the human settlement index. The most important species traits that are associated with non-human-impacted sites were carnivores, frugivores–herbivores and a body size that was greater than 17.8 kg; 25 species were selected by the decision criteria framework for species that were sensitive to degradation based on ecological function information. Conversely, granivores, fossorial and semifossorial

  13. Forest gradient response in Sierran landscapes: the physical template

    Science.gov (United States)

    Urban, Dean L.; Miller, Carol; Halpin, Patrick N.; Stephenson, Nathan L.

    2000-01-01

    Vegetation pattern on landscapes is the manifestation of physical gradients, biotic response to these gradients, and disturbances. Here we focus on the physical template as it governs the distribution of mixed-conifer forests in California's Sierra Nevada. We extended a forest simulation model to examine montane environmental gradients, emphasizing factors affecting the water balance in these summer-dry landscapes. The model simulates the soil moisture regime in terms of the interaction of water supply and demand: supply depends on precipitation and water storage, while evapotranspirational demand varies with solar radiation and temperature. The forest cover itself can affect the water balance via canopy interception and evapotranspiration. We simulated Sierran forests as slope facets, defined as gridded stands of homogeneous topographic exposure, and verified simulated gradient response against sample quadrats distributed across Sequoia National Park. We then performed a modified sensitivity analysis of abiotic factors governing the physical gradient. Importantly, the model's sensitivity to temperature, precipitation, and soil depth varies considerably over the physical template, particularly relative to elevation. The physical drivers of the water balance have characteristic spatial scales that differ by orders of magnitude. Across large spatial extents, temperature and precipitation as defined by elevation primarily govern the location of the mixed conifer zone. If the analysis is constrained to elevations within the mixed-conifer zone, local topography comes into play as it influences drainage. Soil depth varies considerably at all measured scales, and is especially dominant at fine (within-stand) scales. Physical site variables can influence soil moisture deficit either by affecting water supply or water demand; these effects have qualitatively different implications for forest response. These results have clear implications about purely inferential approaches

  14. Effects of heat load gradient occurring in moulding on characterization and ripening of Grana Padano

    NARCIS (Netherlands)

    Pellegrino, L; Battelli, G; Resmini, P; Ferranti, P; Barone, F; Addeo, F

    1997-01-01

    A centripetal temperature gradient takes place in Grana Padano (GP) during moulding because of the slow heat transfer within the cheese and the fast cooling of the outer part. This gradient, in combination with the low pH value, induces a centripetal inactivation of alkaline phosphatase (ALP).

  15. influence of pressure gradients and fracturing in oil field rocks on ...

    African Journals Online (AJOL)

    Admin

    effectiveness of hydraulic fracturing but records exist for improvement of permeabilities for values less than 0.1 md to as high as 910md. CONCLUSIONS. Pressure gradients in rock masses particularly in reservoir rocks are responsible for fracturing of rock masses to form joints and faults. Temperature gradients and tectonic ...

  16. A Global Convergence of LS-CD Hybrid Conjugate Gradient Method

    OpenAIRE

    Xiangfei Yang; Zhijun Luo; Xiaoyu Dai

    2013-01-01

    Conjugate gradient method is one of the most effective algorithms for solving unconstrained optimization problem. In this paper, a modified conjugate gradient method is presented and analyzed which is a hybridization of known LS and CD conjugate gradient algorithms. Under some mild conditions, the Wolfe-type line search can guarantee the global convergence of the LS-CD method. The numerical results show that the algorithm is efficient.

  17. A theory of gradient analysis

    NARCIS (Netherlands)

    Braak, ter C.J.F.

    1988-01-01

    The theory of gradient analysis is presented in this chapter, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified into

  18. Orderings for conjugate gradient preconditionings

    Science.gov (United States)

    Ortega, James M.

    1991-01-01

    The effect of orderings on the rate of convergence of the conjugate gradient method with SSOR or incomplete Cholesky preconditioning is examined. Some results also are presented that help to explain why red/black ordering gives an inferior rate of convergence.

  19. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  20. Modeling chemical gradients in sediments under losing and gaining flow conditions: The GRADIENT code

    Science.gov (United States)

    Boano, Fulvio; De Falco, Natalie; Arnon, Shai

    2018-02-01

    Interfaces between sediments and water bodies often represent biochemical hotspots for nutrient reactions and are characterized by steep concentration gradients of different reactive solutes. Vertical profiles of these concentrations are routinely collected to obtain information on nutrient dynamics, and simple codes have been developed to analyze these profiles and determine the magnitude and distribution of reaction rates within sediments. However, existing publicly available codes do not consider the potential contribution of water flow in the sediments to nutrient transport, and their applications to field sites with significant water-borne nutrient fluxes may lead to large errors in the estimated reaction rates. To fill this gap, the present work presents GRADIENT, a novel algorithm to evaluate distributions of reaction rates from observed concentration profiles. GRADIENT is a Matlab code that extends a previously published framework to include the role of nutrient advection, and provides robust estimates of reaction rates in sediments with significant water flow. This work discusses the theoretical basis of the method and shows its performance by comparing the results to a series of synthetic data and to laboratory experiments. The results clearly show that in systems with losing or gaining fluxes, the inclusion of such fluxes is critical for estimating local and overall reaction rates in sediments.

  1. Temperature Distribution in a Displacement Ventilated Room

    DEFF Research Database (Denmark)

    Nielsen, Peter V.

    The vertical temperature gradient is normally given as a linear temperature distribution between a minimum temperature close to the floor and a maximum temperature close to the ceiling. The minimum temperature can either be a constant fraction of a load dependent difference or it can be connected...

  2. The Signal Extraction of Gravity Gradient Disturbance on Moho

    Directory of Open Access Journals (Sweden)

    YE Zhourun

    2015-06-01

    Full Text Available Using gravity / gravity gradient data for Moho inversion, one of the key steps is how to extract the Moho information data precisely from raw measurements. Here we mainly discussed:①In order to eliminate the error of point mass model used by GEMMA Moho research team, we choose Tesseroid in space domain and harmonic analysis and synthesis method in frequency domain; ②The reasonable use of priori crustal model. Based on GOCO03S model, we provide the gravity gradient disturbing results of three main components which are for Moho inversion. Finally, all experiment results are discussed and analyzed in this paper.

  3. Strain gradient plasticity effects in whisker-reinforced metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2002-01-01

    A metal reinforced by fibers in the micron range is studied using the strain gradient plasticity theory of Fleck and Hutchinson (2001). Cell-model analyzes are used to study the influence of the material length parameters numerically. Different higher order boundary conditions are considered...... at the fiber-matrix interface. The results are presented as overall stress-strain curves for the whisker-reinforced metal, and also contour plots of effective plastic strain are shown. The strain gradient plasticity theory predicts a significant stiffening effect when compared to conventional models...

  4. Simulation of a Hyperbolic Field Energy Analyzer

    CERN Document Server

    Gonzalez-Lizardo, Angel

    2016-01-01

    Energy analyzers are important plasma diagnostic tools with applications in a broad range of disciplines including molecular spectroscopy, electron microscopy, basic plasma physics, plasma etching, plasma processing, and ion sputtering technology. The Hyperbolic Field Energy Analyzer (HFEA) is a novel device able to determine ion and electron energy spectra and temperatures. The HFEA is well suited for ion temperature and density diagnostics at those situations where ions are scarce. A simulation of the capacities of the HFEA to discriminate particles of a particular energy level, as well as to determine temperature and density is performed in this work. The electric field due the combination of the conical elements, collimator lens, and Faraday cup applied voltage was computed in a well suited three-dimensional grid. The field is later used to compute the trajectory of a set of particles with a predetermined energy distribution. The results include the observation of the particle trajectories inside the sens...

  5. Heat-conduction error of temperature sensors in a fluid flow with nonuniform and unsteady temperature distribution.

    Science.gov (United States)

    Khine, Soe Minn; Houra, Tomoya; Tagawa, Masato

    2013-04-01

    In temperature measurement of non-isothermal fluid flows by a contact-type temperature sensor, heat conduction along the sensor body can cause significant measurement error which is called "heat-conduction error." The conventional formula for estimating the heat-conduction error was derived under the condition that the fluid temperature to be measured is uniform. Thus, if we apply the conventional formula to a thermal field with temperature gradient, the heat-conduction error will be underestimated. In the present study, we have newly introduced a universal physical model of a temperature-measurement system to estimate accurately the heat-conduction error even if a temperature gradient exists in non-isothermal fluid flows. Accordingly, we have been able to successfully derive a widely applicable estimation and/or evaluation formula of the heat-conduction error. Then, we have verified experimentally the effectiveness of the proposed formula using the two non-isothermal fields-a wake flow formed behind a heated cylinder and a candle flame-whose fluid-dynamical characteristics should be quite different. As a result, it is confirmed that the proposed formula can represent accurately the experimental behaviors of the heat-conduction error which cannot be explained appropriately by the existing formula. In addition, we have analyzed theoretically the effects of the heat-conduction error on the fluctuating temperature measurement of a non-isothermal unsteady fluid flow to derive the frequency response of the temperature sensor to be used. The analysis result shows that the heat-conduction error in temperature-fluctuation measurement appears only in a low-frequency range. Therefore, if the power-spectrum distribution of temperature fluctuations to be measured is sufficiently away from the low-frequency range, the heat-conduction error has virtually no effect on the temperature-fluctuation measurements even by the temperature sensor accompanying the heat-conduction error in

  6. Vertebrate pressure-gradient receivers

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob

    2011-01-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  7. Computational strain gradient crystal plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2014-01-01

    oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale.......A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems...... of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically...

  8. Predictors of elevational biodiversity gradients change from single taxa to the multi-taxa community level

    Science.gov (United States)

    Peters, Marcell K.; Hemp, Andreas; Appelhans, Tim; Behler, Christina; Classen, Alice; Detsch, Florian; Ensslin, Andreas; Ferger, Stefan W.; Frederiksen, Sara B.; Gebert, Friederike; Haas, Michael; Helbig-Bonitz, Maria; Hemp, Claudia; Kindeketa, William J.; Mwangomo, Ephraim; Ngereza, Christine; Otte, Insa; Röder, Juliane; Rutten, Gemma; Schellenberger Costa, David; Tardanico, Joseph; Zancolli, Giulia; Deckert, Jürgen; Eardley, Connal D.; Peters, Ralph S.; Rödel, Mark-Oliver; Schleuning, Matthias; Ssymank, Axel; Kakengi, Victor; Zhang, Jie; Böhning-Gaese, Katrin; Brandl, Roland; Kalko, Elisabeth K.V.; Kleyer, Michael; Nauss, Thomas; Tschapka, Marco; Fischer, Markus; Steffan-Dewenter, Ingolf

    2016-01-01

    The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities. PMID:28004657

  9. Predictors of elevational biodiversity gradients change from single taxa to the multi-taxa community level.

    Science.gov (United States)

    Peters, Marcell K; Hemp, Andreas; Appelhans, Tim; Behler, Christina; Classen, Alice; Detsch, Florian; Ensslin, Andreas; Ferger, Stefan W; Frederiksen, Sara B; Gebert, Friederike; Haas, Michael; Helbig-Bonitz, Maria; Hemp, Claudia; Kindeketa, William J; Mwangomo, Ephraim; Ngereza, Christine; Otte, Insa; Röder, Juliane; Rutten, Gemma; Schellenberger Costa, David; Tardanico, Joseph; Zancolli, Giulia; Deckert, Jürgen; Eardley, Connal D; Peters, Ralph S; Rödel, Mark-Oliver; Schleuning, Matthias; Ssymank, Axel; Kakengi, Victor; Zhang, Jie; Böhning-Gaese, Katrin; Brandl, Roland; Kalko, Elisabeth K V; Kleyer, Michael; Nauss, Thomas; Tschapka, Marco; Fischer, Markus; Steffan-Dewenter, Ingolf

    2016-12-22

    The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities.

  10. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  11. Efficient conjugate gradient algorithms for computation of the manipulator forward dynamics

    Science.gov (United States)

    Fijany, Amir; Scheid, Robert E.

    1989-01-01

    The applicability of conjugate gradient algorithms for computation of the manipulator forward dynamics is investigated. The redundancies in the previously proposed conjugate gradient algorithm are analyzed. A new version is developed which, by avoiding these redundancies, achieves a significantly greater efficiency. A preconditioned conjugate gradient algorithm is also presented. A diagonal matrix whose elements are the diagonal elements of the inertia matrix is proposed as the preconditioner. In order to increase the computational efficiency, an algorithm is developed which exploits the synergism between the computation of the diagonal elements of the inertia matrix and that required by the conjugate gradient algorithm.

  12. Dynamic pulsed-field-gradient NMR

    CERN Document Server

    Sørland, Geir Humborstad

    2014-01-01

    Dealing with the basics, theory and applications of dynamic pulsed-field-gradient NMR NMR (PFG NMR), this book describes the essential theory behind diffusion in heterogeneous media that can be combined with NMR measurements to extract important information of the system being investigated. This information could be the surface to volume ratio, droplet size distribution in emulsions, brine profiles, fat content in food stuff, permeability/connectivity in porous materials and medical applications currently being developed. Besides theory and applications it will provide the readers with background knowledge on the experimental set-ups, and most important, deal with the pitfalls that are numerously present in work with PFG-NMR. How to analyze the NMR data and some important basic knowledge on the hardware will be explained, too.

  13. Non-uniform temperature gradients and thermal stresses produced ...

    Indian Academy of Sciences (India)

    By varying the values of geometric parameters in the provided solutions, they get the solution for various cases like unique or multiple: strip, rectangular, square, elliptic and circular MHSs. Sunar et al (2006) considered a cantilever assembly subjected to heating at its fixed end, which resembles the welding of a sheet metal.

  14. Collective effects of temperature gradients and gravity on droplet coalescence

    Science.gov (United States)

    Zhang, Xiaoguang; Wang, Hua; Davis, Robert H.

    1993-01-01

    The interaction and coalescence of small spherical drops in dilute, homogeneous dispersions are considered theoretically under conditions, where drop motion results from gravity settling and thermocapillary migration acting simultaneously. A trajectory analysis is used to predict pairwise collision rates, and population dynamics equations are solved to predict the time evolution of the droplet size distribution. The rate of droplet collisions and growth may be reduced dramatically by antiparallel alignment of the gravitational and thermocapillary velocities. For such antiparallel alignment with the gravitational relative velocity exceeding the thermocapillary relative velocity for two widely separated drops, there is a 'collision-forbidden region' in parameter space. This occurs because the gravitational relative velocity decays more rapidly with decreasing separation distance between the drops than does the thermocapillary relative velocity, and so the resultant relative velocity along the line-of-centers from these two sources combined becomes zero at a finite separation and the drops are unable to collide. As a result, small drops which initially collide and coalesce due to thermocapillary motion will only grow until they reach a critical size for which the oppositely directed gravitational motion balances the thermocapillary motion.

  15. Microfludic device for creating ionic strength gradients over DNA microarrays for efficient DNA melting studies and assay development

    DEFF Research Database (Denmark)

    Petersen, Jesper; Poulsen, Lena; Birgens, Henrik

    2009-01-01

    is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple...... microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More...

  16. Quantifying the Impacts of Environmental Factors on Vegetation Dynamics over Climatic and Management Gradients of Central Asia

    Directory of Open Access Journals (Sweden)

    Olena Dubovyk

    2016-07-01

    Full Text Available Currently there is a lack of quantitative information regarding the driving factors of vegetation dynamics in post-Soviet Central Asia. Insufficient knowledge also exists concerning vegetation variability across sub-humid to arid climatic gradients as well as vegetation response to different land uses, from natural rangelands to intensively irrigated croplands. In this study, we analyzed the environmental drivers of vegetation dynamics in five Central Asian countries by coupling key vegetation parameter “overall greenness” derived from Moderate Resolution Imaging Spectroradiometer (MODIS Normalized Difference Vegetation Index (NDVI time series data, with its possible factors across various management and climatic gradients. We developed nine generalized least-squares random effect (GLS-RE models to analyze the relative impact of environmental factors on vegetation dynamics. The obtained results quantitatively indicated the extensive control of climatic factors on managed and unmanaged vegetation cover across Central Asia. The most diverse vegetation dynamics response to climatic variables was observed for “intensively managed irrigated croplands”. Almost no differences in response to these variables were detected for managed non-irrigated vegetation and unmanaged (natural vegetation across all countries. Natural vegetation and rainfed non-irrigated crop dynamics were principally associated with temperature and precipitation parameters. Variables related to temperature had the greatest relative effect on irrigated croplands and on vegetation cover within the mountainous zone. Further research should focus on incorporating the socio-economic factors discussed here in a similar analysis.

  17. Possible role of rf melted microparticles on the operation of high-gradient accelerating structures

    Directory of Open Access Journals (Sweden)

    G. S. Nusinovich

    2009-10-01

    Full Text Available High-gradient accelerating structures should operate reliably for a long time. Therefore studies of various processes which may lead to disruption of such an operation are so important. In the present paper, the dissipation of rf electromagnetic energy in metallic microparticles is analyzed accounting for the temperature dependence of the skin depth. Such particles may appear in structures, for example, due to mechanical fracture of irises in strong rf electric fields. It is shown that such microparticles with dimensions on the order of the skin depth, being immersed in the region of strong rf magnetic field, can absorb enough energy in long-pulse operation to be melted. Then, the melted clumps can impinge on the surface of a structure and create nonuniformities leading to field enhancement and corresponding emission of dark current. Results are given for several geometries and materials of microparticles.

  18. The stability of weakly collisional plasmas with thermal and composition gradients

    DEFF Research Database (Denmark)

    Pessah, M.E.; Chakraborty, S.

    2013-01-01

    temperature and composition. This allows us to discuss for the first time the dynamics of weakly collisional environments where heat conduction, momentum transport, and ion-diffusion are anisotropic with respect to the direction of the magnetic field. We show that depending on the relative signs...... the magnetic field configurations that arise as a natural consequence of the HBI, which would be MTI stable in a homogeneous medium, could be alleviated if the mean molecular weight gradient is steep enough, i.e., (¿µ)/µ > (¿T)/T. This study constitutes a first step toward understanding the interaction between...... approximation if heavy elements are able to sediment in the inner region of the galaxy cluster. Motivated by the need to obtain a more complete picture of the dynamical properties of the ICM, we analyze the stability of a weakly collisional, magnetized plane-parallel atmosphere which is stratified in both...

  19. 40 CFR 230.25 - Salinity gradients.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230... Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity... fresh or salt water may change existing salinity gradients. For example, partial blocking of the...

  20. Gradient remediability in linear distributed parabolic systems ...

    African Journals Online (AJOL)

    The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...

  1. Pumpernickel Valley Geothermal Project Thermal Gradient Wells

    Energy Technology Data Exchange (ETDEWEB)

    Z. Adam Szybinski

    2006-01-01

    The Pumpernickel Valley geothermal project area is located near the eastern edge of the Sonoma Range and is positioned within the structurally complex Winnemucca fold and thrust belt of north-central Nevada. A series of approximately north-northeast-striking faults related to the Basin and Range tectonics are superimposed on the earlier structures within the project area, and are responsible for the final overall geometry and distribution of the pre-existing structural features on the property. Two of these faults, the Pumpernickel Valley fault and Edna Mountain fault, are range-bounding and display numerous characteristics typical of strike-slip fault systems. These characteristics, when combined with geophysical data from Shore (2005), indicate the presence of a pull-apart basin, formed within the releasing bend of the Pumpernickel Valley – Edna Mountain fault system. A substantial body of evidence exists, in the form of available geothermal, geological and geophysical information, to suggest that the property and the pull-apart basin host a structurally controlled, extensive geothermal field. The most evident manifestations of the geothermal activity in the valley are two areas with hot springs, seepages, and wet ground/vegetation anomalies near the Pumpernickel Valley fault, which indicate that the fault focuses the fluid up-flow. There has not been any geothermal production from the Pumpernickel Valley area, but it was the focus of a limited exploration effort by Magma Power Company. In 1974, the company drilled one exploration/temperature gradient borehole east of the Pumpernickel Valley fault and recorded a thermal gradient of 160oC/km. The 1982 temperature data from five unrelated mineral exploration holes to the north of the Magma well indicated geothermal gradients in a range from 66 to 249oC/km for wells west of the fault, and ~283oC/km in a well next to the fault. In 2005, Nevada Geothermal Power Company drilled four geothermal gradient wells, PVTG-1

  2. Micro-environment measurement along a climatic gradient

    Science.gov (United States)

    Szita, Renáta; Ambrus, András

    2017-04-01

    Aquatic macroinvertebrates are heavily influenced by the climatic changes even in temperate, forested habitats. The potential impacts of global climate change may be an increase in water temperatures, changes in seasonal patterns (including intensity) of precipitation and runoff which can alter hydrologic characteristics of aquatic systems. Rapid changes in hydrology caused by extreme heavy rainfalls - especially if there are clearcuts within the catchment area - may cause changes in the hydromorphology, restructure the stream bed or alter the path of the stream itself. All these affect the species composition, that is why the investigated aquatic ecosystems, the streams in forested area have limited ability to adapt to climate change. In recent study, the samples were taken from three streams which are located in similar, forested areas. The sampling sites were chosen along a climatic gradient. The first sampling site is in Mecsek mountains (South Hungary), the second one is in Kőszeg mountains (West Hungary) and the third one is in Sopron mountains (Northwest Hungary). The biological samples were taken with a specific cross-section transect arrangement, applying a new, microhabitat-based quadrat sampling method in all selected areas. Parallel with the macroinvertebrate sampling, there were taken hydraulic measures too. The velocity profile, shear velocity, shear stress, drag force and the Reynold's and Froude numbers were estimated to define the near-bed hydraulic conditions, which influence the community structure of aquatic macroinvertebrates. The main aims of the study were recognize differences along the climatic gradient in a similar habitat types of small streams in forested area if there are any, check up the ability of detection fine differences between similar communities of the new sampling methode which focuses on the microhabitat-structure of certain stream sections instead of taking and analyzing composit samples from the whole section. One more

  3. Salinity Gradients for Sustainable Energy: Primer, Progress, and Prospects.

    Science.gov (United States)

    Yip, Ngai Yin; Brogioli, Doriano; Hamelers, Hubertus V M; Nijmeijer, Kitty

    2016-11-15

    Combining two solutions of different composition releases the Gibbs free energy of mixing. By using engineered processes to control the mixing, chemical energy stored in salinity gradients can be harnessed for useful work. In this critical review, we present an overview of the current progress in salinity gradient power generation, discuss the prospects and challenges of the foremost technologies - pressure retarded osmosis (PRO), reverse electrodialysis (RED), and capacitive mixing (CapMix) and provide perspectives on the outlook of salinity gradient power generation. Momentous strides have been made in technical development of salinity gradient technologies and field demonstrations with natural and anthropogenic salinity gradients (for example, seawater-river water and desalination brine-wastewater, respectively), but fouling persists to be a pivotal operational challenge that can significantly ebb away cost-competitiveness. Natural hypersaline sources (e.g., hypersaline lakes and salt domes) can achieve greater concentration difference and, thus, offer opportunities to overcome some of the limitations inherent to seawater-river water. Technological advances needed to fully exploit the larger salinity gradients are identified. While seawater desalination brine is a seemingly attractive high salinity anthropogenic stream that is otherwise wasted, actual feasibility hinges on the appropriate pairing with a suitable low salinity stream. Engineered solutions are foulant-free and can be thermally regenerative for application in low-temperature heat utilization. Alternatively, PRO, RED, and CapMix can be coupled with their analog separation process (reverse osmosis, electrodialysis, and capacitive deionization, respectively) in salinity gradient flow batteries for energy storage in chemical potential of the engineered solutions. Rigorous techno-economic assessments can more clearly identify the prospects of low-grade heat conversion and large-scale energy storage

  4. Oxygen Gradients in the Microcirculation

    Science.gov (United States)

    Pittman, Roland N.

    2010-01-01

    Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO2 gradient and that the permeability for oxygen along the intervening pathway is sufficient. PMID:21281453

  5. Dai-Kou type conjugate gradient methods with a line search only using gradient.

    Science.gov (United States)

    Huang, Yuanyuan; Liu, Changhe

    2017-01-01

    In this paper, the Dai-Kou type conjugate gradient methods are developed to solve the optimality condition of an unconstrained optimization, they only utilize gradient information and have broader application scope. Under suitable conditions, the developed methods are globally convergent. Numerical tests and comparisons with the PRP+ conjugate gradient method only using gradient show that the methods are efficient.

  6. Stringy bounces and gradient instabilities

    CERN Document Server

    Giovannini, Massimo

    2017-01-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.

  7. The metabolic theory of ecology convincingly explains the latitudinal diversity gradient of neotropical freshwater fish.

    Science.gov (United States)

    Bailly, Dayani; Cassemiro, Fernanda A S; Agostinho, Carlos S; Marques, Elineide E; Agostinho, Angelo A

    2014-02-01

    In the context of diversity gradients, the metabolic theory of ecology (MTE) posits that the logarithm of species richness should decrease linearly with the inverse of temperature, resulting in a specific slope. However, the empirical validity of this model depends on whether the data do not violate certain assumptions. Here, we test the predictions of MTE evaluating all of its assumptions simultaneously. We used Neotropical freshwater fish and tested whether the logarithm of species richness varied negatively and linearly with temperature, resulting in the slope value specified by the MTE. As we observed that the assumption of the energetic equivalence of populations was not achieved, we also analyzed whether the energetic nonequivalence of populations could be responsible for the possible lack of fit to the MTE predictions. Our results showed that the relationship between richness and the inverse of temperature was linear, negative and significant and included the slope value predicted by the MTE. With respect to the assumptions, we observed that there was no spatial variation in the average energy flux of populations or in the body size and abundance of species. However, the energetic equivalence of populations was not achieved and the violation of this assumption did not affect the predictive power of the model. We conclude that the validity of the assumptions (spatial invariance in the average flux energy of populations and spatial invariance in the body size and abundance, especially) is required for the correct interpretation of richness patterns. Furthermore, we conclude that MTE is robust in its explanation of diversity gradients for freshwater fish, proving to be a valuable tool in describing ecological complexity from individuals to ecosystems.

  8. Ant functional responses along environmental gradients.

    Science.gov (United States)

    Arnan, Xavier; Cerdá, Xim; Retana, Javier

    2014-11-01

    Understanding species distributions and diversity gradients is a central challenge in ecology and requires prior knowledge of the functional traits mediating species' survival under particular environmental conditions. While the functional ecology of plants has been reasonably well explored, much less is known about that of animals. Ants are among the most diverse, abundant and ecologically significant organisms on earth, and they perform a great variety of ecological functions. In this study, we analyse how the functional species traits present in ant communities vary along broad gradients in climate, productivity and vegetation type in the south-western Mediterranean. To this end, we compiled one of the largest animal databases to date: it contains information on 211 local ant communities (including eight climate variables, productivity, and vegetation type) and 124 ant species, for which 10 functional traits are described. We used traits that characterize different dimensions of the ant functional niche with respect to morphology, life history and behaviour at both individual and colony level. We calculated two complementary functional trait community indices ('trait average' and 'trait dissimilarity') for each trait, and we analysed how they varied along the three different gradients using generalized least squares models that accounted for spatial autocorrelation. Our results show that productivity, vegetation type and, to a lesser extent, each climate variable per se might play an important role in shaping the occurrence of functional species traits in ant communities. Among the climate variables, temperature and precipitation seasonality had a much higher influence on functional responses than their mean values, whose effects were almost lacking. Our results suggest that strong relationships might exist between the abiotic environment and the distribution of functional traits among south-western Mediterranean ant communities. This finding indicates that

  9. Southern hospitality: a latitudinal gradient in gene flow in the marine environment.

    Science.gov (United States)

    Kelly, Ryan P; Eernisse, Douglas J

    2007-03-01

    In recent years population genetics and phylogeographic studies have become increasingly valuable tools for inferring both historical and present-day genetic patterns within marine species. Here, we take a comparative approach to population-level study, analyzing original mitochondrial DNA data from 969 individuals representing 28 chiton (Mollusca: Polyplacophora) species to uncover large-scale genetic patterns along the Pacific coast of North America. The data reveal a distinct latitudinal connectivity gradient among chitons: species that exist at lower latitudes tend to have more isolated populations. This trend appears to be a product of between-species differences; within species, no significant gradient in connectivity is observed. Lower average annual sea surface temperatures are hypothesized to contribute to longer larval duration (and by extension, greater connectivity) among lecithotrophic species, providing a mechanism for the observed positive correlation between gene flow and latitude. Because increased isolation among populations may lead to speciation, a latitudinal trend in gene flow may contribute to the increased species diversity observed at lower latitudes.

  10. Assessment of Acacia Koa Forest Health across Environmental Gradients in Hawai‘i Using Fine Resolution Remote Sensing and GIS

    Directory of Open Access Journals (Sweden)

    Rodolfo Martinez Morales

    2011-05-01

    Full Text Available Koa (Acacia koa forests are found across broad environmental gradients in the Hawai‘ian Islands. Previous studies have identified koa forest health problems and dieback at the plot level, but landscape level patterns remain unstudied. The availability of high-resolution satellite images from the new GeoEye1 satellite offers the opportunity to conduct landscape-level assessments of forest health. The goal of this study was to develop integrated remote sensing and geographic information systems (GIS methodologies to characterize the health of koa forests and model the spatial distribution and variability of koa forest dieback patterns across an elevation range of 600–1,000 m asl in the island of Kaua‘i, which correspond to gradients of temperature and rainfall ranging from 17–20 °C mean annual temperature and 750–1,500 mm mean annual precipitation. GeoEye1 satellite imagery of koa stands was analyzed using supervised classification techniques based on the analysis of 0.5-m pixel multispectral bands. There was clear differentiation of native koa forest from areas dominated by introduced tree species and differentiation of healthy koa stands from those exhibiting dieback symptoms. The area ratio of healthy koa to koa dieback corresponded linearly to changes in temperature across the environmental gradient, with koa dieback at higher relative abundance in warmer areas. A landscape-scale map of healthy koa forest and dieback distribution demonstrated both the general trend with elevation and the small-scale heterogeneity that exists within particular elevations. The application of these classification techniques with fine spatial resolution imagery can improve the accuracy of koa forest inventory and mapping across the islands of Hawai‘i. Such findings should also improve ecological restoration, conservation and silviculture of this important native tree species.

  11. Spatial Variability of Soil Characteristics along a Landscape Gradient in Bellanwila-Attidiya Area

    Directory of Open Access Journals (Sweden)

    S. Cooray

    2012-05-01

    Full Text Available Wetlands are comprised of unique components of soil, water and biodiversity which are interconnected. Although water and biodiversity components of wetlands are being somewhat investigated, a very few research have been carried out to investigate soil properties.This study focused on spatial variability of soil chemical and physical parameters in a land use gradient around the Bellanwila-Attidiya Sanctuary, This study was carried out for a period of 3 months and several random soil samples were obtained from all land use areas. Selected physical and chemical properties of soil were analyzed according to the Standard Methods and the GIS maps were developed using ArcView GIS 3.2. The results indicated that all chemical and physical parameters of soil varied across the land use gradient, except for temperature. According to the GIS maps there are apparent variations in distribution of soil properties. On the surface, the highest level of each parameter was found as follows: - NO3- – industrial area, PO4 3- - functioning paddy fields, SO4 2- - residential area, Cl- - residential area, Fe3+ - functioning paddy fields, moisture content - wetland, pH – industrial area, salinity- residential area, electrical conductivity – residential area. At a 1 m depth the pattern was different: NO3- – abandoned paddy fields, PO4 3- – functioning paddy fields, SO4 2- - wetland, Cl- - wetland, Fe3+ - residential area, moisture content - wetland, pH – industrial area, salinity - wetland, electrical conductivity - wetland. The findings clearly exhibit the increases in anthropogenic pressure have resulted in wide-scale alternation of soil properties, at least in the surface soil, across a land use gradient. Managing land use in the watershed of the wetland thus needs adequate attention to conserve this natural ecosystem.

  12. Relationships between geology and geothermal gradients in Kansas

    Energy Technology Data Exchange (ETDEWEB)

    Stavnes, S.A.; Steeples, D.W.; Ruscetta, C.A. (ed.)

    1982-07-01

    Bottom hole temperature values from existing oil and gas wells and thermal logging data from geothermal wells are used to determine the factors responsible for geographic variation in the subsurface temperature distribution in Kansas. Geothermal gradient data range from 25/sup 0/C/km to 55/sup 0/C/km in the upper 300 m. The geologic factors proposed to explain this variation are: (1) topography of the crystalline basement surface; (2) variation in rates of heat production in the crystalline basement; (3) variation in thermal conductivity in the sedimentary section; and (4) possible convection upward and eastward from the Denver-Julesberg Basin. (MJF)

  13. PM 3655 PHILIPS Logic analyzer

    CERN Multimedia

    A logic analyzer is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or may correlate assembly with source-level software. Logic Analyzers have advanced triggering capabilities, and are useful when a user needs to see the timing relationships between many signals in a digital system.

  14. Polychromatic microdiffraction characterization of defect gradients in severely deformed materials.

    Science.gov (United States)

    Barabash, Rozaliya I; Ice, Gene E; Liu, Wenjun; Barabash, Oleg M

    2009-01-01

    This paper analyzes local lattice rotations introduced in severely deformed polycrystalline titanium by friction stir welding. Nondestructive three-dimensional (3D) spatially resolved polychromatic X-ray microdiffraction, is used to resolve the local crystal structure of the restructured surface from neighboring local structures in the sample material. The measurements reveal strong gradients of strain and geometrically necessary dislocations near the surface and illustrate the potential of polychromatic microdiffraction for the study of deformation in complex materials systems.

  15. Analyzing data files in SWAN

    CERN Document Server

    Gajam, Niharika

    2016-01-01

    Traditionally analyzing data happens via batch-processing and interactive work on the terminal. The project aims to provide another way of analyzing data files: A cloud-based approach. It aims to make it a productive and interactive environment through the combination of FCC and SWAN software.

  16. Effect of Thermal Gradients Created by Electromagnetic Fields on Cell-Membrane Electroporation Probed by Molecular-Dynamics Simulations

    Science.gov (United States)

    Song, J.; Garner, A. L.; Joshi, R. P.

    2017-02-01

    The use of nanosecond-duration-pulsed voltages with high-intensity electric fields (˜100 kV /cm ) is a promising development with many biomedical applications. Electroporation occurs in this regime, and has been attributed to the high fields. However, here we focus on temperature gradients. Our numerical simulations based on molecular dynamics predict the formation of nanopores and water nanowires, but only in the presence of a temperature gradient. Our results suggest a far greater role of temperature gradients in enhancing biophysical responses, including possible neural stimulation by infrared lasers.

  17. The Effect of Temperature on Moisture Transport in Concrete.

    Science.gov (United States)

    Wang, Yao; Xi, Yunping

    2017-08-09

    Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter DHT, which can be determined by the present test data. The test results indicated that DHT is not a constant but increases linearly with the temperature variation. A material model was developed for DHT based on the experimental results obtained in this study.

  18. The Educational Gradient in Health in China

    Science.gov (United States)

    Chen, Qiulin; Eggleston, Karen; Zhang, Wei; Zhao, Jiaying; Zhou, Sen

    2017-01-01

    It has been well established that better educated individuals enjoy better health and longevity. In theory, the educational gradients in health could be flattening if diminishing returns to improved average education levels and the influence of earlier population health interventions outweigh the gradient-steepening effects of new medical and health technologies. This paper documents how the gradients are evolving in China, a rapidly developing country, about which little is known on this topic. Based on recent mortality data and nationally representative health surveys, we find large and, in some cases, steepening educational gradients. We also find that the gradients vary by cohort, gender and region. Further, we find that the gradients can only partially be accounted for by economic factors. These patterns highlight the double disadvantage of those with low education, and suggest the importance of policy interventions that foster both aspects of human capital for them. PMID:29056815

  19. Morphological instability of a confined polymer film in a thermal gradient

    NARCIS (Netherlands)

    Schaffer, E; Harkema, S; Roerdink, M; Blossey, R; Steiner, U

    2003-01-01

    We report the experimental observation of a morphological instability of a confined polymer-air double layer sandwiched between two plates set to different temperatures. The homogeneous temperature gradient across the double layer causes the breakup of the polymer film into columns or stripes

  20. Color and population gradients in globular clusters

    Science.gov (United States)

    Djorgovski, S.; Piotto, G.; Mallen-Ornelas, G.

    1991-01-01

    We present preliminary results from a survey for color and population gradients in globular cluster cores. Color gradients, in the sense of becoming bluer inwards, are always found in post-core-collapse clusters. They seem to be caused by the demise of red giants, and possibly an increased number of blue stragglers. This may be a consequence of stellar interactions during and after the core collapse. No gradients are seen in clusters with King-model morphology.

  1. Ant colony optimization and stochastic gradient descent.

    Science.gov (United States)

    Meuleau, Nicolas; Dorigo, Marco

    2002-01-01

    In this article, we study the relationship between the two techniques known as ant colony optimization (ACO) and stochastic gradient descent. More precisely, we show that some empirical ACO algorithms approximate stochastic gradient descent in the space of pheromones, and we propose an implementation of stochastic gradient descent that belongs to the family of ACO algorithms. We then use this insight to explore the mutual contributions of the two techniques.

  2. Testing the limits of gradient sensing.

    Directory of Open Access Journals (Sweden)

    Vinal Lakhani

    2017-02-01

    Full Text Available The ability to detect a chemical gradient is fundamental to many cellular processes. In multicellular organisms gradient sensing plays an important role in many physiological processes such as wound healing and development. Unicellular organisms use gradient sensing to move (chemotaxis or grow (chemotropism towards a favorable environment. Some cells are capable of detecting extremely shallow gradients, even in the presence of significant molecular-level noise. For example, yeast have been reported to detect pheromone gradients as shallow as 0.1 nM/μm. Noise reduction mechanisms, such as time-averaging and the internalization of pheromone molecules, have been proposed to explain how yeast cells filter fluctuations and detect shallow gradients. Here, we use a Particle-Based Reaction-Diffusion model of ligand-receptor dynamics to test the effectiveness of these mechanisms and to determine the limits of gradient sensing. In particular, we develop novel simulation methods for establishing chemical gradients that not only allow us to study gradient sensing under steady-state conditions, but also take into account transient effects as the gradient forms. Based on reported measurements of reaction rates, our results indicate neither time-averaging nor receptor endocytosis significantly improves the cell's accuracy in detecting gradients over time scales associated with the initiation of polarized growth. Additionally, our results demonstrate the physical barrier of the cell membrane sharpens chemical gradients across the cell. While our studies are motivated by the mating response of yeast, we believe our results and simulation methods will find applications in many different contexts.

  3. Novel pressure-gradient driven component for blood extraction

    Science.gov (United States)

    Fujioka, K.; Khumpuang, S.; Horede, M.; Sugiyama, S.

    2006-01-01

    Portable blood analysis devices are usually appreciable for applications in blood diagnostic system. We have designed and fabricated a low-cost and simple deal blood extraction device for a biomedical analysis. The device mainly composes of blood extraction tool and a functional bio-chemical analyzing element. In this work, we report the fabrication and pressure-gradient testing results of the blood extraction tool which consists of painless microneedle array and pressure-gradient tank. Microneedle array was fabricated by X-ray lithography using PCT (Plane-pattern to Cross-section Transfer) technique. The idea of our extraction device was simple but capability which is just to hold a sufficient pressure gradient between the tank and blood vessel. The device can draw the volume of blood up to 237 μl. The device was made of low-cost and disposable materials since it is expected to be used for single blood analysis system. In this work, we introduce design, fabrication and mechanism of the pressure gradient driven component including the extraction test results. The fabrication method of microneedle used in our system is also described.

  4. Learning curves for stochastic gradient descent in linear feedforward networks.

    Science.gov (United States)

    Werfel, Justin; Xie, Xiaohui; Seung, H Sebastian

    2005-12-01

    Gradient-following learning methods can encounter problems of implementation in many applications, and stochastic variants are sometimes used to overcome these difficulties. We analyze three online training methods used with a linear perceptron: direct gradient descent, node perturbation, and weight perturbation. Learning speed is defined as the rate of exponential decay in the learning curves. When the scalar parameter that controls the size of weight updates is chosen to maximize learning speed, node perturbation is slower than direct gradient descent by a factor equal to the number of output units; weight perturbation is slower still by an additional factor equal to the number of input units. Parallel perturbation allows faster learning than sequential perturbation, by a factor that does not depend on network size. We also characterize how uncertainty in quantities used in the stochastic updates affects the learning curves. This study suggests that in practice, weight perturbation may be slow for large networks, and node perturbation can have performance comparable to that of direct gradient descent when there are few output units. However, these statements depend on the specifics of the learning problem, such as the input distribution and the target function, and are not universally applicable.

  5. An elevational diversity gradient of bacteria on Tibetan Plateau

    Science.gov (United States)

    Zhang, G.; Yuan, Y.; Si, G.; Han, C.; Wang, J.; Zhao, J.; Luo, T.; Zhou, J.

    2013-12-01

    A central focus of biogeography is to determine the factors that govern spatial variation in biodiversity. Classic biogeography pattern of macroorganisms along altitudinal gradients was well observed and studied well over two centuries ago, while elevation patterns of microorganisms remains poorly understood. Using functional gene microarray (GeoChip) and pryosequencing methods, we examined the soil bacterial diversity pattern within alpine wetlands along an elevational gradient on the Tibetan Plateau. We found that observed patterns of plant and microbial diversity decreased monotonically from the lowest to the highest elevations. Our results showed the richness of genes involved in carbon and nitrogen cycling were significantly decreased with increasing elevations and the gene abundance of carbon degradation and nitrogen cycling were also decreased at high latitude which was consistent with soil enzyme activities. Further statistical tests showed that microbial functional diversities are structured primarily by environmental filtering caused by temperature. This work indicated that temperature maybe the common driving force structuring bacterial and plant communities along elevational gradients on Tibetan Plateau

  6. Role of turbulence regime on determining the local density gradient

    Science.gov (United States)

    Wang, X.; Mordijck, S.; Doyle, E. J.; Zeng, L.; Staebler, G. M.; Meneghini, O.; Smith, S. P.

    2018-01-01

    In this paper we show that the local density gradient in the plasma core depends on the calculated mode-frequency of the most unstable linear mode and reaches a maximum when this frequency is close to zero. Previous theoretical and experimental work on AUG has shown that the ratio of electron to ion temperature, and as such the frequency of the dominant linear gyrokinetic mode, affects the local density gradient close to ρ = 0.3 (Fable et al 2010 Plasma Phys. Control. Fusion 52 015007, Angioni et al 2011 Nucl. Fusion 51 023006). On DIII-D we find that by adding electron cyclotron heating, we modify the dominant unstable linear gyrokinetic mode from an ion temperature gradient (ITG) mode to a trapped electron mode (TEM), which means that the frequency of the dominant mode changes sign (from the ion to the electron direction). Local density peaking around mid-radius increases by 50% right around the cross-over between the ITG and TEM regimes. By comparing how the particle flux changes, through the derivative of the electron density, n e , with respect to time, \\partial n_e/\\partial t , we find that the particle flux also exhibits the same trend versus mode frequency. As a result, we find that the changes in local particle transport are inversely proportional to the changes in electron density, indicating that the changes are driven by a change in thermo-diffusive pinch.

  7. Convection induced by thermal gradients on thin reaction fronts

    Science.gov (United States)

    Ruelas Paredes, David R. A.; Vasquez, Desiderio A.

    2017-09-01

    We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients. If the effects of these gradients oppose each other, we observe a range of wavelengths that make the flat front unstable. Numerical solutions of the nonlinear model show curved fronts of steady shape with convection propagating faster than flat fronts. Exothermic fronts increase the temperature of the fluid as they propagate through the domain. This increment in temperature decreases with increasing speed.

  8. Surface-attached orthogonal gradient hydrogels

    Science.gov (United States)

    Chinnayan Kannan, Pandiyarajan; Genzer, Jan

    Gradient materials play a significant role in the creation of artificial implants due to their potential to reduce stress concentration when two or more structures with different mechanical properties are joined together, e . g . , tendon, a fibrous protein that connects the soft and hard muscle tissues in our body. We employ free radical polymerization to synthesize random copolymers containing 90% of N-isopropyl acrylamide (NIPAAm), 5% photo-active methacrylyloxybenzophenone (MABP) and 5% thermally-active styrenesulfonylazide (SSAz) crosslinkers. The presence of MABP and SSAz facilitates adjusting gel density on a flat support in two orthogonal directions by spatially and independently controlling UV dosage and temperature. The swelling behavior (α) of the gels in water and methanol is examined using a spectroscopic ellipsometry and the degree of swelling depends on the extent of crosslinking that ranges from α = 1-1.2 (highly crosslinked gels) to α = 4-5 (loosely crosslinked gels). We compare the network properties surface-attached gels and un-attached identical counterparts and confirm that the linear swelling ratio of surface-attached networks is higher than that of the corresponding un-attached gels.

  9. Status of a high gradient CH - cavity

    Energy Technology Data Exchange (ETDEWEB)

    Almomani, Ali; Ratzinger, Ulrich [IAP, Frankfurt Universitaet (Germany)

    2015-07-01

    This pulsed linac activity aims on compact designs and on a considerable increase of the voltage gain per meter. A high gradient CH-cavity operated at 325 MHz was developed at IAP-Frankfurt. The mean effective accelerating field for this cavity is expected well above 10 MV/m at β=0.164. This cavity is developed within a funded project. The results might influence the rebuilt of the UNILAC - Alvarez section, aiming to achieve the beam intensities specified for the GSI-FAIR project (15 mA U{sup 28+}). Another motivation is the development of an efficient pulsed ion accelerator for significantly higher energies like 60 AMeV. The new GSI 3 MW Thales klystron test stand will be used for the cavity RF power tests. Detailed studies on two different types of copper plating are performed with this cavity. Additionally, operating of normal conducting cavities at cryogenic temperatures are discussed for the case of very short RF pulses. The first measurement results for this cavity are presented.

  10. Metallicity gradients in early-type galaxies

    Science.gov (United States)

    Schombert, James M.; Hanlan, Patricia C.; Barsony, Mary; Rakos, Karl D.

    1993-01-01

    A study of medium-to-bright early-type galaxies in six bandpasses from 3500 A to 2.2 microns is presented in order to quantify their colors and color gradients and relate these to metallicity and properties of the underlying stellar population. The Stromgren filter system chosen makes it possible to introduce a new calibration to the Mg(2) system from the present narrow-band v - y indices. A comparison is presented of narrow-band colors centered on particular spectral features vs a color dominated by the mean temperature of the giant branch (i.e., J - K) to test the effects of light vs heavy element abundances on knowledge of the total system metallicity, Z, and the effects of reddening. A good correlation is found between v - y and Mg(2); it provides a connection between one light element metallicity indicator (v - y centers on the CN blend) and another, Mg. The color-magnitude relations for all five optical and near-IR colors are shown. The strongest correlation exists for the metallicity colors, v - y and J - K.

  11. CSTT Update: Fuel Quality Analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Brosha, Eric L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lujan, Roger W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mukundan, Rangachary [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rockward, Tommy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Romero, Christopher J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Williams, Stefan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wilson, Mahlon S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2018-02-06

    These are slides from a presentation. The following topics are covered: project background (scope and approach), developing the prototype (timeline), update on intellectual property, analyzer comparisons (improving humidification, stabilizing the baseline, applying clean-up strategy, impact of ionomer content and improving clean-up), proposed operating mode, considerations for testing in real-world conditions (Gen 1 analyzer electronics development, testing partner identified, field trial planning), summary, and future work.

  12. Exploring Nf=2 +1 QCD thermodynamics from the gradient flow

    Science.gov (United States)

    Taniguchi, Yusuke; Ejiri, Shinji; Iwami, Ryo; Kanaya, Kazuyuki; Kitazawa, Masakiyo; Suzuki, Hiroshi; Umeda, Takashi; Wakabayashi, Naoki; WHOT-QCD Collaboration

    2017-07-01

    The energy-momentum tensor plays an important role in QCD thermodynamics. Its expectation value contains information of the pressure and the energy density as its diagonal part. Further properties like viscosity and specific heat can be extracted from its correlation function. A nonperturbative evaluation of it on the lattice is called. Recently, a new method based on the gradient flow was introduced to calculate the energy-momentum tensor on the lattice and has been successfully applied to quenched QCD. In this paper, we apply the gradient flow method to calculate the energy-momentum tensor in (2 +1 )-flavor QCD adopting a nonperturbatively O (a )-improved Wilson quark action and the renormalization group-improved Iwasaki gauge action. As the first application of the method with dynamical quarks, we study at a single but fine lattice spacing a ≃0.07 fm with heavy u and d quarks (mπ/mρ≃0.63 ) and approximately physical s quark (mηss/mϕ≃0.74 ). With the fixed-scale approach, temperature is varied by the temporal lattice size Nt at a fixed lattice spacing. Performing simulations on lattices with Nt=16 to 4, the temperature range of T ≃174 - 697 MeV is covered. We find that the results of the pressure and the energy density by the gradient flow method are consistent with the previous results using the T -integration method at T ≲280 MeV (Nt≳10 ), while the results show disagreement at T ≳350 MeV (Nt≲8 ), presumably due to the small-Nt lattice artifact of O ((a T )2) =O (1 /Nt2) . We also apply the gradient flow method to evaluate the chiral condensate taking advantage of the gradient flow method that renormalized quantities can be directly computed avoiding the difficulty of explicit chiral violation with lattice quarks. We compute the renormalized chiral condensate in the MS ¯ scheme at renormalization scale μ =2 GeV with a high precision to study the temperature dependence of the chiral condensate and its disconnected susceptibility. Even with

  13. Measurement of diffusion coefficient of liquid metals by using Gradient Heating Furnace in ISS

    OpenAIRE

    Masaki, Tadahiko; Itami, Toshio; Watanabe, Yuki; 正木 匡彦; 伊丹 俊夫; 渡辺 勇基

    2007-01-01

    The experimental techniques for the measurements of diffusion coefficient have been studied in JAXA toward the utilization of microgravity environment in ISS (International Space Station). The experimental cartridge for the gradient heating furnace, GHF (Gradient Heating Furnace), was developed for the application of shear cell which is the advanced technique of diffusion experiments. The temperature profiles of GHF were measured for the diffusion experiments and the isothermal condition can ...

  14. Magneto-Seebeck effect in spin-valve with in-plane thermal gradient

    OpenAIRE

    S. Jain; D. D. Lam; A. Bose; H. Sharma; V. R. Palkar; C. V. Tomy; Y. Suzuki; A. A. Tulapurkar

    2014-01-01

    We present measurements of magneto-Seebeck effect on a spin valve with in-plane thermal gradient. We measured open circuit voltage and short circuit current by applying a temperature gradient across a spin valve stack, where one of the ferromagnetic layers is pinned. We found a clear hysteresis in these two quantities as a function of magnetic field. From these measurements, the magneto-Seebeck effect was found to be same as magneto-resistance effect.

  15. Magneto-Seebeck effect in spin-valve with in-plane thermal gradient

    Directory of Open Access Journals (Sweden)

    S. Jain

    2014-12-01

    Full Text Available We present measurements of magneto-Seebeck effect on a spin valve with in-plane thermal gradient. We measured open circuit voltage and short circuit current by applying a temperature gradient across a spin valve stack, where one of the ferromagnetic layers is pinned. We found a clear hysteresis in these two quantities as a function of magnetic field. From these measurements, the magneto-Seebeck effect was found to be same as magneto-resistance effect.

  16. Critical density gradients for small-scale plasma irregularity generation in the E and F regions

    Science.gov (United States)

    Makarevich, Roman A.

    2017-09-01

    Electron density gradients that can make plasma unstable in the ionospheric E and F regions are analyzed. We focus on critical gradient values required for plasma instability to become operational to produce decameter-scale plasma irregularities observed by the Super Dual Auroral Radar Network (SuperDARN) without any nonlinear wave cascade. Analytic expressions are developed for the critical gradients using a recently developed general formalism for arbitrary geometry and with the ion inertia and stabilizing thermal diffusion effects included. It is demonstrated that the problem can be analyzed using a single equation applicable in both the E and F regions that only differs in the sign of the main term related to convection strength. Analytic expressions are obtained, and results are presented for (1) critical gradient strength for arbitrary gradient and propagation directions, (2) range of propagation directions with unstable primary waves, (3) most favorable configuration and minimum critical gradient, and (4) most favorable propagation direction for arbitrary gradient direction. It is shown that the most favorable configuration is achieved for propagation along the differential drift and gradient perpendicular to it and that an unexpected exception is the F region under strong convection when propagation and gradient are both rotated by a certain angle. It is estimated that in the F region, from which most of the SuperDARN backscatter comes, primary decameter waves can be generated for gradient scales as large as 100 km for favorable orientations and strong plasma convection >500 m/s and that much smaller scales of 200-1000 m are required for unfavorable orientations.

  17. Canonical trivialization of gravitational gradients

    Science.gov (United States)

    Niedermaier, Max

    2017-06-01

    A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein-Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie-Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions.

  18. On-Demand Urine Analyzer

    Science.gov (United States)

    Farquharson, Stuart; Inscore, Frank; Shende, Chetan

    2010-01-01

    A lab-on-a-chip was developed that is capable of extracting biochemical indicators from urine samples and generating their surface-enhanced Raman spectra (SERS) so that the indicators can be quantified and identified. The development was motivated by the need to monitor and assess the effects of extended weightlessness, which include space motion sickness and loss of bone and muscle mass. The results may lead to developments of effective exercise programs and drug regimes that would maintain astronaut health. The analyzer containing the lab-on-a- chip includes materials to extract 3- methylhistidine (a muscle-loss indicator) and Risedronate (a bone-loss indicator) from the urine sample and detect them at the required concentrations using a Raman analyzer. The lab-on- a-chip has both an extractive material and a SERS-active material. The analyzer could be used to monitor the onset of diseases, such as osteoporosis.

  19. Study of thermal-gradient-induced migration of brine inclusions in salt. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Olander, D.R.

    1984-08-01

    Natural salt deposits, which are being considered for high-level waste disposal, contain a small volume fraction of water in the form of brine inclusions distributed throughout the salt. Radioactive decay heating of the nuclear wastes will impose a temperature gradient on the surrounding salt which mobilizes the brine inclusions. Inclusions filled completely with brine (the all-liquid inclusions) migrate up the temperature gradient and eventually accumulate brine near the buried waste forms. The brine may slowly corrode or degrade the waste forms, which is undesirable. Therefore it is important to consider the migration of brine inclusions in salt under imposed temperature gradients to properly evaluate the performance of a future salt repository for nuclear wastes. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is nonlinear. At high axial loads, the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. All-liquid inclusions filled with mixed brines were also studied. For gas-liquid inclusions, helium, air and argon were compared. Migration studies were also conducted on single crystallites of natural salt as well as in polycrystalline natural salt samples. The behavior of the inclusions at large-ange grain boundaries was observed.

  20. Regulation of leaf traits in canopy gradients.

    NARCIS (Netherlands)

    Pons, T.L.|info:eu-repo/dai/nl/069365822

    2016-01-01

    The gradient of leaf traits in a canopy from sunlit upper regions to shaded lower ones is regulated in response to the density of its leaf area. The gradients of environmental factors act as signals for the regulation. The result is improved resource use efficiency for carbon gain at the whole plant

  1. Preconditioning the modified conjugate gradient method ...

    African Journals Online (AJOL)

    In this paper, the convergence analysis of the conventional conjugate Gradient method was reviewed. And the convergence analysis of the modified conjugate Gradient method was analysed with our extension on preconditioning the algorithm. Convergence of the algorithm is a function of the condition number of M-1A.

  2. Gradient High Performance Liquid Chromatography Method ...

    African Journals Online (AJOL)

    Purpose: To develop a gradient high performance liquid chromatography (HPLC) method for the simultaneous determination of phenylephrine (PHE) and ibuprofen (IBU) in solid dosage form. Methods: HPLC determination was carried out on an Agilent XDB C-18 column (4.6 x 150mm, 5 μ particle size) with a gradient ...

  3. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  4. Newton's method in the context of gradients

    Directory of Open Access Journals (Sweden)

    John W. Neuberger

    2007-09-01

    Full Text Available This paper gives a common theoretical treatment for gradient and Newton type methods for general classes of problems. First, for Euler-Lagrange equations Newton's method is characterized as an (asymptotically optimal variable steepest descent method. Second, Sobolev gradient type minimization is developed for general problems using a continuous Newton method which takes into account a "boundary condition" operator.

  5. Patterns of macromycete community assemblage along an elevation gradient: options for fungal gradient and metacommunity analyse

    Science.gov (United States)

    Marko Gómez-Hernández; Guadalupe Williams-Linera; Roger Guevara; D. Jean Lodge

    2012-01-01

    Gradient analysis is rarely used in studies of fungal communities. Data on macromycetes from eight sites along an elevation gradient in central Veracruz, Mexico, were used to demonstrate methods for gradient analysis that can be applied to studies of communities of fungi. Selected sites from 100 to 3,500 m altitude represent tropical dry forest, tropical montane cloud...

  6. The effect of reactions on the formation and readout of the gradient of Bicoid

    CERN Document Server

    Ipiña, Emiliano Perez

    2016-01-01

    During early development, the establishment of gradients of transcriptional factors determines the patterning of cell fates. The case of Bicoid (Bcd) in {\\it Drosophila melanogaster} embryos is well documented and studied. There are still controversies as to whether {\\it SDD} models in which Bcd is {\\it Synthesized} at one end, then {\\it Diffuses} and is {\\it Degraded} can explain the gradient formation within the timescale observed experimentally. The Bcd gradient is observed in embryos that express a Bicoid-eGFP fusion protein (Bcd-GFP) which cannot differentiate if Bcd is freely diffusing or bound to immobile sites. In this work we analyze an {\\it SDID} model that includes the {\\it Interaction} of Bcd with binding sites. Using previously determined biophysical parameters we find that this model can explain the gradient formation within the experimentally observed time. Analyzing the differences between the free and bound Bcd distributions we observe that the latter spans over a longer lengthscale. We concl...

  7. Values Range of Tympanometric Gradient in Otitis Media With Effusion.

    Science.gov (United States)

    Duzer, Sertac; Sakallioglu, Oner; Akyigit, Abdulvahap; Polat, Cahit; Cetiner, Hasan; Susaman, Nihat

    2017-05-01

    The aim of this study was to establish how reliable a given tympanogram is in predicting the presence or absence of a middle ear effusion, and to provide new views for the diagnostic information of tympanometry. The use of tympanometric gradient in addition to static admittance is the focus of this study. The authors enrolled 146 female and 129 male patients. The participants were allocated into groups as follow: Group A1 consisted of 50 healthy children. Group A2 consisted of 86 children with otitis media with effusion. Group B1 consisted of 85 healthy adults. Group B2 consisted of 54 adults with otitis media with effusion. All diagnostic otoscopic examination and tympanometry were performed in both ears. The authors analyzed the distribution of tympanograms in patients with otitis media with effusion and healthy controls. When the right and left ear canal volume of either children or adults with otitis media with effusion compared with healthy controls, no statistically significant different was observed (P > 0.05). On the other hand, the statistically significant difference was detected for the values of compliance, pressure and gradient of either children or adults with otitis media with effusion compared with healthy controls (P < 0.05). The authors found the values range from 0.01 to 1.52 mL gradients (mean least value 0.15 mL) in adults and the values range from 0.01 to 0.93 mL gradients (mean least value 0.10 mL) in children in the presence of otitis media with effusion. The authors think that tympanometric gradient may be useful to detect the otitis media with effusion.

  8. Quantitative analysis of mRNA translation in mammalian spermatogenic cells with sucrose and Nycodenz gradients

    Directory of Open Access Journals (Sweden)

    Bagarova Jana

    2010-12-01

    Full Text Available Abstract Background Developmental and global regulation of mRNA translation plays a major role in regulating gene expression in mammalian spermatogenic cells. Sucrose gradients are widely used to analyze mRNA translation. Unfortunately, the information from sucrose gradient experiments is often compromised by the absence of quantification and absorbance tracings, and confusion about the basic properties of sucrose gradients. Methods The Additional Materials contain detailed protocols for the preparation and analysis of sucrose and Nycodenz gradients, obtaining absorbance tracings of sucrose gradients, aligning tracings and fractions, and extraction of equal proportions of RNA from all fractions. Results The techniques described here have produced consistent measurements despite changes in personnel and minor variations in RNA extraction, gradient analysis, and mRNA quantification, and describes for the first time potential problems in using gradients to analyze mRNA translation in purified spermatogenic cells. Conclusions Accurate quantification of the proportion of polysomal mRNA is useful in comparing translational activity at different developmental stages, different mRNAs, different techniques and different laboratories. The techniques described here are sufficiently accurate to elucidate the contributions of multiple regulatory elements of variable strength in regulating translation of the sperm mitochondria associated cysteine-rich protein (Smcp mRNA in transgenic mice.

  9. Thermo Scientific Ozone Analyzer Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Springston, S. R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-03-01

    The primary measurement output from the Thermo Scientific Ozone Analyzer is the concentration of the analyte (O3) reported at 1-s resolution in units of ppbv in ambient air. Note that because of internal pneumatic switching limitations the instrument only makes an independent measurement every 4 seconds. Thus, the same concentration number is repeated roughly 4 times at the uniform, monotonic 1-s time base used in the AOS systems. Accompanying instrument outputs include sample temperatures, flows, chamber pressure, lamp intensities and a multiplicity of housekeeping information. There is also a field for operator comments made at any time while data is being collected.

  10. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  11. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  12. Protein gradient films of fibroin and gelatine.

    Science.gov (United States)

    Claussen, Kai U; Lintz, Eileen S; Giesa, Reiner; Schmidt, Hans-Werner; Scheibel, Thomas

    2013-10-01

    Gradients are a natural design principle in biological systems that are used to diminish stress concentration where materials of differing mechanical properties connect. An interesting example of a natural gradient material is byssus, which anchors mussels to rocks and other hard substrata. Building upon previous work with synthetic polymers and inspired by byssal threads, protein gradient films are cast using glycerine-plasticized gelatine and fibroin exhibiting a highly reproducible and smooth mechanical gradient, which encompasses a large range of modulus from 160 to 550 MPa. The reproducible production of biocompatible gradient films represents a first step towards medical applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Daily extreme temperature multifractals in Catalonia (NE Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Burgueño, A. [Departament d' Astronomia i Meteorologia, Universitat de Barcelona, Barcelona (Spain); Lana, X., E-mail: francisco.javier.lana@upc.edu [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Barcelona (Spain); Serra, C. [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Barcelona (Spain); Martínez, M.D. [Departament de Física Aplicada, Universitat Politècnica de Catalunya, Barcelona (Spain)

    2014-02-01

    The multifractal character of the daily extreme temperatures in Catalonia (NE Spain) is analyzed by means of the multifractal detrended fluctuation analysis (MF-DFA) applied to 65 thermometric records covering years 1950–2004. Although no clear spatial patterns of the multifractal spectrum parameters appear, factor scores deduced from Principal Component analysis indicate some signs of spatial gradients. Additionally, the daily extreme temperature series are classified depending on their complex time behavior, through four multifractal parameters (Hurst exponent, Hölder exponent with maximum spectrum, spectrum asymmetry and spectrum width). As a synthesis of the three last parameters, a basic measure of complexity is proposed through a normalized Complexity Index. Its regional behavior is found to be free of geographical dependences. This index represents a new step towards the description of the daily extreme temperatures complexity.

  14. Bacteria are not too small for spatial sensing of chemical gradients: An experimental evidence

    DEFF Research Database (Denmark)

    Thar, Roland; Kühl, Michael

    2003-01-01

    By analyzing the chemotactic behavior of a recently described marine bacterial species, we provide experimental evidence that bacteria are not too small for sensing chemical gradients spatially. The bipolar flagellated vibrioid bacteria (typical size 2 × 6 µm) exhibit a unique motility pattern...... the band toward the oxic region typically return to the band within 16 s following a U-shaped track. A detailed analysis of the tracks reveals that the cells must be able to sense the oxygen gradient perpendicular to their swimming direction. Thus, they can detect oxygen gradients along a distance of ˜5 µm...

  15. On the homogenization of metal matrix composites using strain gradient plasticity

    DEFF Research Database (Denmark)

    Azizi, Reza; Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2014-01-01

    energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain......The homogenized response of metal matrix composites (MMC) is studied using strain gradient plasticity. The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free...

  16. General approach for solving the density gradient theory in the interfacial tension calculations

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Michelsen, Michael Locht

    2017-01-01

    Within the framework of the density gradient theory, the interfacial tension can be calculated by finding the density profiles that minimize an integral of two terms over the system of infinite width. It is found that the two integrands exhibit a constant difference along the interface for a finite...... property evaluations compared to other methods. The performance of the algorithm with recommended parameters is analyzed for various systems, and the efficiency is further compared with the geometric-mean density gradient theory, which only needs to solve nonlinear algebraic equations. The results show...... that the algorithm is only 5-10 times less efficient than solving the geometric-mean density gradient theory....

  17. Software-Design-Analyzer System

    Science.gov (United States)

    Tausworthe, Robert C.

    1991-01-01

    CRISP-90 software-design-analyzer system, update of CRISP-80, is set of computer programs constituting software tool for design and documentation of other software and supporting top-down, hierarchical, modular, structured methodologies for design and programming. Written in Microsoft QuickBasic.

  18. Analyzing Software Piracy in Education.

    Science.gov (United States)

    Lesisko, Lee James

    This study analyzes the controversy of software piracy in education. It begins with a real world scenario that presents the setting and context of the problem. The legalities and background of software piracy are explained and true court cases are briefly examined. Discussion then focuses on explaining why individuals and organizations pirate…

  19. Methods of analyzing crude oil

    Science.gov (United States)

    Cooks, Robert Graham; Jjunju, Fred Paul Mark; Li, Anyin; Rogan, Iman S.

    2017-08-15

    The invention generally relates to methods of analyzing crude oil. In certain embodiments, methods of the invention involve obtaining a crude oil sample, and subjecting the crude oil sample to mass spectrometry analysis. In certain embodiments, the method is performed without any sample pre-purification steps.

  20. Analyzing Student Difficulties in Reading.

    Science.gov (United States)

    Ediger, Marlow

    According to this paper, a good reading teacher is able to analyze problems faced by students in reading and remediate that which is necessary. The paper stresses that the reading teacher needs to be a good observer of student reading habits to notice where to intervene to improve the skills and attitudes of the reader. It discusses diagnosis and…