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Sample records for 15c temperature gradient

  1. Temperature Gradient in Hall Thrusters

    SciTech Connect

    D. Staack; Y. Raitses; N.J. Fisch

    2003-11-24

    Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons.

  2. Sound beam manipulation based on temperature gradients

    SciTech Connect

    Qian, Feng; Quan, Li; Liu, Xiaozhou Gong, Xiufen

    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. CARS thermometry in high temperature gradients

    NASA Astrophysics Data System (ADS)

    Zhu, J. Y.; Dunn-Rankin, D.

    1993-01-01

    CARS is an effective non-intrusive technique for measuring gas temperature in combustion environments. In regions of high temperature gradient, however, the CARS signal is complicated by contributions from gas at different temperature. This paper examines theoretically the uncertainty associated with CARS thermometry in steep temperature gradients. In addition, the work compares the temperature predicted from CARS with the adiabatic mixed temperature of the gas resident in the measurement volume. This comparison helps indicate the maximum sample volume size allowed for accurate temperature measurements.

  4. Texturing of REBCO using temperature gradient.

    SciTech Connect

    Salama, K.; Athur, S. P.; Balachandran, U.; Energy Technology; Univ. of Houston

    2001-01-01

    Isothermal melt texturing is currently a well-established technique for manufacturing superconducting materials with high trapped magnetic field and levitation forces. For conductor applications, however, a temperature gradient needs to be employed in order to align the oriented domains with the a-b planes where the current will be flowing over long lengths. Melt-textured Y-123 bars of length 100 mm with Jc values of 70,000 A/cm2 at 77 K in self-field have been routinely manufactured by directional solidification. The presence of temperature gradient also lends itself to faster texturing rates. Recently, Ag-clad Yb-123 tapes made by the powder-in-tube process were successfully melt textured in the presence of a temperature gradient and controlled oxygen partial pressure. These tapes exhibit the potential to be an alternative to BSCCO tapes, for relatively high temperature and magnetic field applications.

  5. HOT PRESSING WITH A TEMPERATURE GRADIENT

    DOEpatents

    Hausner, H.H.

    1958-05-20

    A method is described for producing powder metal compacts with a high length to width ratio, which are of substantially uniform density. The process consists in arranging a heating coil around the die and providing a temperature gradient along the length of the die with the highest temperature at the point of the compact farthest away from the ram or plunger.

  6. On-chip temperature gradient interaction chromatography.

    PubMed

    Shih, Chi-Yuan; Chen, Yang; Xie, Jun; He, Qing; Tai, Yu-Chong

    2006-04-14

    This paper reports the first integrated microelectromechanical system (MEMS) HPLC chip that consists of a parylene high-pressure LC column, an electrochemical sensor, a resistive heater and a thermal-isolation structure for on-chip temperature gradient interaction chromatography application. The separation column was 8 mm long, 100 microm wide, 25 microm high and was packed with 5 microm sized, C18-coated beads using conventional slurry-packing technique. A novel parylene-enhanced, air-gap thermal isolation technology was used to reduce heater power consumption by 58% and to reduce temperature rise in the off-column area by 67%. The fabricated chip consumed 400 mW when operated at 100 degrees C. To test the chromatography performance of the fabricated system, a mixture of derivatized amino acids was chosen for separation. A temporal temperature gradient scanning from 25 to 65 degrees C with a ramping rate of 3.6 degrees C/min was applied to the column during separation. Successful chromatographic separation of derivatized amino acids was carried out using our chip. Compared with conventional temperature gradient HPLC system which incorporates "macro oven" to generate temporal temperature gradient on the column, our chip's thermal performance, i.e., power consumption and thermal response, is greatly improved without sacrificing chromatography quality.

  7. Temperature gradient driven lasing and stimulated cooling.

    PubMed

    Sandner, K; Ritsch, H

    2012-11-09

    A laser can be understood as a thermodynamic engine converting heat to a coherent single mode field close to Carnot efficiency. To achieve lasing, spectral shaping of the excitation light is used to generate a higher effective temperature on the pump than on the gain transition. Here, using a toy model of a quantum well structure with two suitably designed tunnel-coupled wells kept at different temperatures, we predict that lasing can also occur on an actual spatial temperature gradient between the pump and gain regions. Gain and narrow band laser emission require a sufficiently large temperature gradient and resonator quality. Lasing appears concurrent with amplified heat flow between the reservoirs and points to a new form of stimulated solid state cooling. In addition, such a mechanism could reduce intrinsic heating and thus extend the operating regime of quantum cascade lasers by substituting phonon emission driven injection by a phonon absorption step.

  8. Voltammetry under a Controlled Temperature Gradient

    PubMed Central

    Krejci, Jan; Sajdlova, Zuzana; Krejci, Jan; Marvanek, Tomas

    2010-01-01

    Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nernst layer and enables more accurate control of the electrode response enhancement by a combination of diffusion and thermal diffusion. We have thus studied the effect of Soret phenomenon by cyclic voltammetry measurements in ferro/ferricyanide. The time dependence of sensor response disappears when applying the Soret phenomenon, and the complicated shape of the cyclic voltammogram is replaced by a simple exponential curve. We have derived the Cotrell-Soret equation describing the steady-state response with an applied temperature difference. PMID:22163578

  9. Temperature Gradient Field Theory of Nucleation

    NASA Astrophysics Data System (ADS)

    Das, S.; Ain, W. Q.; Azhari, A.; Prasada Rao, A. K.

    2016-02-01

    According to the proposed theory, ceramic particles present in molten metal, lose heat at a slower rate than the metallic liquid during cooling. Such condition results in the formation of a spherical thermal gradient field (TGF) around each particle. Hence, the interstitials (low temperature) of such TGFs are the regions to reach the nucleation temperature first, owing to low energy barrier than the liquid-particle interface (higher temperature). Analytics also indicate that the nucleation rate is higher at the TGF interstitials, than at the liquid-particle interface. Such TGF network results in simultaneous nucleation throughout the system, resulting in grain refinement.

  10. Geothermal temperature gradient core drill, Santiam Pass

    SciTech Connect

    Not Available

    1989-01-01

    DOE is proposing to share in the cost of drilling a 3000-ft core hole to evaluate temperature gradients, subsurface geology and the geothermal potential of an area in the Cascade Mountains. The proposed core hole will be located in the Deschutes National Forest in Oregon, near Santiam Pass. The proposed action has been described in the Environmental Assessment (EA) for Geothermal Temperature Gradient Core Drill Santiam Pass Area (No. OR-050-9-51) prepared by the US Bureau of Land Management (BLM). DOE has determined that the BLM EA adequately addresses the impacts of the proposal and is hereby adopting the EA in partial fulfillment of its NEPA responsibilities. Based upon a review of the EA and an independent analysis, DOE has concluded that the proposed corehole drilling project does not constitute a major federal action significantly affecting the quality of the human environment within the meaning of NEPA. Therefore, an environmental impact statement will not be prepared.

  11. Spatial temperature gradients guide axonal outgrowth

    PubMed Central

    Black, Bryan; Vishwakarma, Vivek; Dhakal, Kamal; Bhattarai, Samik; Pradhan, Prabhakar; Jain, Ankur; Kim, Young-tae; Mohanty, Samarendra

    2016-01-01

    Formation of neural networks during development and regeneration after injury depends on accuracy of axonal pathfinding, which is primarily believed to be influenced by chemical cues. Recently, there is growing evidence that physical cues can play crucial role in axonal guidance. However, detailed mechanism involved in such guidance cues is lacking. By using weakly-focused near-infrared continuous wave (CW) laser microbeam in the path of an advancing axon, we discovered that the beam acts as a repulsive guidance cue. Here, we report that this highly-effective at-a-distance guidance is the result of a temperature field produced by the near-infrared laser light absorption. Since light absorption by extracellular medium increases when the laser wavelength was red shifted, the threshold laser power for reliable guidance was significantly lower in the near-infrared as compared to the visible spectrum. The spatial temperature gradient caused by the near-infrared laser beam at-a-distance was found to activate temperature-sensitive membrane receptors, resulting in an influx of calcium. The repulsive guidance effect was significantly reduced when extracellular calcium was depleted or in the presence of TRPV1-antagonist. Further, direct heating using micro-heater confirmed that the axonal guidance is caused by shallow temperature-gradient, eliminating the role of any non-photothermal effects. PMID:27460512

  12. Spatial temperature gradients guide axonal outgrowth

    NASA Astrophysics Data System (ADS)

    Black, Bryan; Vishwakarma, Vivek; Dhakal, Kamal; Bhattarai, Samik; Pradhan, Prabhakar; Jain, Ankur; Kim, Young-Tae; Mohanty, Samarendra

    2016-07-01

    Formation of neural networks during development and regeneration after injury depends on accuracy of axonal pathfinding, which is primarily believed to be influenced by chemical cues. Recently, there is growing evidence that physical cues can play crucial role in axonal guidance. However, detailed mechanism involved in such guidance cues is lacking. By using weakly-focused near-infrared continuous wave (CW) laser microbeam in the path of an advancing axon, we discovered that the beam acts as a repulsive guidance cue. Here, we report that this highly-effective at-a-distance guidance is the result of a temperature field produced by the near-infrared laser light absorption. Since light absorption by extracellular medium increases when the laser wavelength was red shifted, the threshold laser power for reliable guidance was significantly lower in the near-infrared as compared to the visible spectrum. The spatial temperature gradient caused by the near-infrared laser beam at-a-distance was found to activate temperature-sensitive membrane receptors, resulting in an influx of calcium. The repulsive guidance effect was significantly reduced when extracellular calcium was depleted or in the presence of TRPV1-antagonist. Further, direct heating using micro-heater confirmed that the axonal guidance is caused by shallow temperature-gradient, eliminating the role of any non-photothermal effects.

  13. Domain wall motion by localized temperature gradients

    NASA Astrophysics Data System (ADS)

    Moretti, Simone; Raposo, Victor; Martinez, Eduardo; Lopez-Diaz, Luis

    2017-02-01

    Magnetic domain wall (DW) motion induced by a localized Gaussian temperature profile is studied in a Permalloy nanostrip within the framework of the stochastic Landau-Lifshitz-Bloch equation. The different contributions to thermally induced DW motion, entropic torque and magnonic spin transfer torque, are isolated and compared. The analysis of magnonic spin transfer torque includes a description of thermally excited magnons in the sample. A third driving force due to a thermally induced dipolar field is found and described. Finally, thermally induced DW motion is studied under realistic conditions by taking into account the edge roughness. The results give quantitative insights into the different mechanisms responsible for domain wall motion in temperature gradients and allow for comparison with experimental results.

  14. Effect of Temperature Gradient on Thick Film Selective Emitter Emittance

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Good, Brian S.; Clark, Eric B.; Chen, Zheng

    1997-01-01

    A temperature gradient across a thick (greater than or equal to .1 mm) film selective emitter will produce a significant reduction in the spectral emittance from the no temperature gradient case. Thick film selective emitters of rare earth doped host materials such as yttrium-aluminum-garnet (YAG) are examples where temperature gradient effects are important. In this paper a model is developed for the spectral emittance assuming a linear temperature gradient across the film. Results of the model indicate that temperature gradients will result in reductions the order of 20% or more in the spectral emittance.

  15. Observation of temperature-gradient-induced magnetization

    PubMed Central

    Hou, Dazhi; Qiu, Zhiyong; Iguchi, R.; Sato, K.; Vehstedt, E. K.; Uchida, K.; Bauer, G. E. W.; Saitoh, E.

    2016-01-01

    Applying magnetic fields has been the method of choice to magnetize non-magnetic materials, but they are difficult to focus. The magneto-electric effect and voltage-induced magnetization generate magnetization by applied electric fields, but only in special compounds or heterostructures. Here we demonstrate that a simple metal such as gold can be magnetized by a temperature gradient or magnetic resonance when in contact with a magnetic insulator by observing an anomalous Hall-like effect, which directly proves the breakdown of time-reversal symmetry. Such Hall measurements give experimental access to the spectral spin Hall conductance of the host metal, which is closely related to other spin caloritronics phenomena such as the spin Nernst effect and serves as a reference for theoretical calculation. PMID:27457185

  16. Thermoacoustic mixture separation with an axial temperature gradient

    SciTech Connect

    Geller, Drew W; Swift, Gregory A

    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.

  17. Moving-Gradient Furnace With Constant-Temperature Cold Zone

    NASA Technical Reports Server (NTRS)

    Gernert, Nelson J.; Shaubach, Robert M.

    1993-01-01

    Outer heat pipe helps in controlling temperature of cold zone of furnace. Part of heat-pipe furnace that includes cold zone surrounded by another heat pipe equipped with heater at one end and water cooling coil at other end. Temperature of heat pipe maintained at desired constant value by controlling water cooling. Serves as constant-temperature heat source or heat sink, as needed, for gradient of temperature as gradient region moved along furnace. Proposed moving-gradient heat-pipe furnace used in terrestrial or spaceborne experiments on directional solidification in growth of crystals.

  18. Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles.

    PubMed

    Zheng, Chao; Huang, Haiying; He, Tianbai

    2014-02-01

    In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure.

  19. Electromagnetic electron temperature gradient driven instability in toroidal plasmas

    NASA Astrophysics Data System (ADS)

    Zielinski, J.; Smolyakov, A. I.; Beyer, P.; Benkadda, S.

    2017-02-01

    The fluid theory of a new type of electron temperature gradient instability is proposed. This mode is closely related to the short wavelength Alfvén mode in the regime k⊥ 2 ρi 2 > 1 . Contrary to standard electron temperature gradient modes, which are mostly electrostatic, the considered mode is fundamentally electromagnetic and does not exist in the electrostatic limit. The mechanism of instability relies on gradients in both the electron temperature and magnetic field. It is suggested that this instability may be a destabilizing mechanism for collisionless microtearing modes, which are observed in a number of gyrokinetic simulations.

  20. Relating Paleoclimate Data and Past Temperature Gradients: Some Suggestive Rules

    NASA Technical Reports Server (NTRS)

    Rind, David

    1999-01-01

    Understanding tropical sensitivity is perhaps the major concern confronting researchers, for both past and future climate change issues. Tropical data has been beset by contradictions, and many techniques applicable to the extratropics are either unavailable or fraught with uncertainty when applied at low latitudes. Paleoclimate data, if interpreted within the context of the latitudinal temperature gradient data they imply, can be used to estimate what happened to tropical temperatures in the past, and provide a first guess for what might happen in the future. The approach is made possible by the modeling result that atmospheric dynamical changes, and the climate impacts they produce, respond primarily to temperature gradient changes. Here we review some "rules" obtained from GCM (General Circulation Model) experiments with different sea surface temperature gradients and different forcing, that can be used to relate paleoclimate reconstructions to the likely temperature gradient changes they suggest.

  1. The Electron Temperature Gradient in the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Quireza, Cintia; Rood, Robert T.; Bania, T. M.; Balser, Dana S.; Maciel, Walter J.

    2006-12-01

    We derive the electron temperature gradient in the Galactic disk, using a sample of H II regions that spans Galactocentric distances of 0-17 kpc. The electron temperature was calculated using high-precision radio recombination line and continuum observations for more than 100 H II regions. Nebular Galactocentric distances were calculated in a consistent manner, using the radial velocities measured by our radio recombination line survey. The large number of nebulae widely distributed over the Galactic disk, together with the uniformity of our data, provide a secure estimate of the present electron temperature gradient in the Milky Way. Because metals are the main coolants in the photoionized gas, the electron temperature along the Galactic disk should be directly related to the distribution of heavy elements in the Milky Way. Our best estimate of the electron temperature gradient is derived from a sample of 76 sources for which we have the highest quality data. The present gradient in electron temperature has a minimum at the Galactic center and rises at a rate of 287+/-46 K kpc-1. There are no significant variations in the value of the gradient as a function of Galactocentric radius or azimuth. The scatter we find in the H II region electron temperatures at a given Galactocentric radius is not due to observational error, but rather to intrinsic fluctuations in these temperatures, which are almost certainly due to fluctuations in the nebular heavy-element abundances. Comparing the H II region gradient with the much steeper gradient found for planetary nebulae suggests that the electron temperature gradient evolves with time, becoming flatter as a consequence of the chemical evolution of the Milky Way's disk.

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

    ERIC Educational Resources Information Center

    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.

  3. Analysis of the Critical Electron Temperature Gradient in Tore Supra

    NASA Astrophysics Data System (ADS)

    Horton, W.; Hu, B.; Zhu, P.; Hoang, G. T.; Bourdelle, C.; Ottaviani, M.; Garbet, X.; Giruzzi, G.

    2001-10-01

    The Tore Supra database of fast wave electron heating (FWEH) discharges is analyzed with respect to the role of the critical electron temperature gradient. The experimental evidence for the linear theory critical gradient is presented from both (i) power balance thermal flux versus the temperature gradient extrapolated to zero flux and (ii) the fluctuation spectra versus the gadient extrapolated to the vanishing point. Case studies with the LOCO and BALDUR transport codes are used to investigate the impact of the critical gradient in both cases close to the Ohmic discharge with 0.75 MW of rf power and strongly heated discharges with up to 7.4 MW of RF power. The interpretation of the critical gradient as a heat pinch term is also explored with thermodynamic theory and the space-time symmetries of the underlying dynamical equations. There is a relationship between the critical electron temperature gradient and the particle pinch. The evidence for the two candidates to explain the electron transport: trapped electron modes (TEM), characterized by wavenumbers much longer than the ion gyroradius, and the smaller-scale electron temperature gradient modes (ETG) with wavelengths comparable and smaller than the ion gyroradius is presented in detail.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  5. Gradient Limitations in Room Temperature and Superconducting Acceleration Structures

    SciTech Connect

    Solyak, N. A.

    2009-01-22

    Accelerating gradient is a key parameter of the accelerating structure in large linac facilities, like future Linear Collider. In room temperature accelerating structures the gradient is limited mostly by breakdown phenomena, caused by high surface electric fields or pulse surface heating. High power processing is a necessary procedure to clean surface and improve the gradient. In the best tested X-band structures the achieved gradient is exceed 100 MV/m in of {approx}200 ns pulses for breakdown rate of {approx}10{sup -7}. Gradient limit depends on number of factors and no one theory which can explain all sets of experimental results and predict gradient in new accelerating structure. In paper we briefly overview the recent experimental results of breakdown studies, progress in understanding of gradient limitations and scaling laws. Although superconducting rf technology has been adopted throughout the world for ILC, it has frequently been difficult to reach the predicted performance in these structures due to a number of factors: multipactoring, field emission, Q-slope, thermal breakdown. In paper we are discussing all these phenomena and the ways to increase accelerating gradient in SC cavity, which are a part of worldwide R and D program.

  6. Gradient limitations in room temperature and superconducting acceleration structures

    SciTech Connect

    Solyak, N.A.; /Fermilab

    2008-10-01

    Accelerating gradient is a key parameter of the accelerating structure in large linac facilities, like future Linear Collider. In room temperature accelerating structures the gradient is limited mostly by breakdown phenomena, caused by high surface electric fields or pulse surface heating. High power processing is a necessary procedure to clean surface and improve the gradient. In the best tested X-band structures the achieved gradient is exceed 100 MV/m in of {approx}200 ns pulses for breakdown rate of {approx} 10{sup -7}. Gradient limit depends on number of factors and no one theory which can explain all sets of experimental results and predict gradient in new accelerating structure. In paper we briefly overview the recent experimental results of breakdown studies, progress in understanding of gradient limitations and scaling laws. Although superconducting rf technology has been adopted throughout the world for ILC, it has frequently been difficult to reach the predicted performance in these structures due to a number of factors: multipactoring, field emission, Q-slope, thermal breakdown. In paper we are discussing all these phenomena and the ways to increase accelerating gradient in SC cavity, which are a part of worldwide R&D program.

  7. Variable-Temperature-Gradient Device for Solidification Research

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.

    1985-01-01

    Device for research in solidification and crystal growth allows crystallization of melt observed as occurs. Temperature gradient across melt specimen increased or decreased rapidly while solidification front proceeds at constant speed across sample. Device moves sample at same speed, thereby holding position of liquid/solid interface stationary within field of optical microscope. Device, variabletemperature-gradient microscope stage, used to study crystal growth at constant rate while thermal driving force is varied.

  8. An Expression for the Temperature Gradient in Chaotic Fields

    SciTech Connect

    S.R. Hudson

    2008-12-22

    A coordinate system adapted to the invariant structures of chaotic magnetic fields is constructed. The coordinates are based on a set of ghost-surfaces, defined via an action-gradient flow between the minimax and minimizing periodic orbits. The construction of the chaotic coordinates allows an expression describing the temperature gradient across a chaotic magnetic field to be derived. The results are in close agreement with a numerical calculation.

  9. Pre-ovulatory temperature gradients within mammalian ovaries: a review.

    PubMed

    Hunter, R H F; Einer-Jensen, N

    2005-08-01

    The existence of a temperature gradient between the testis and deep body temperature has been accepted for many years. It is based on two simultaneous principles: cooling of the testis through the scrotal wall and transfer of heat between the testicular blood vessels. The ovary is positioned in the abdomen; a temperature difference parallel to the male system therefore seems less likely. However, the temperature of large follicles has been found to be 0.5 to 1.5 degrees C cooler than the ovarian stroma in rabbits, pigs and, probably, women. The temperature difference seems to be based on a heat-consuming process in the expanding follicullar fluid, and a local transfer of heat between intra-ovarian blood vessels. The reason for the temperature gradient is not yet known; one may speculate of a common reason for the cooling of the gamete in male and female.

  10. Rock alteration in an experimentally imposed temperature gradient

    SciTech Connect

    Charles, R.W.

    1980-01-01

    Rock alteration in a dynamic (circulating) hydrothermal system can be applied to any geologic system with mobile fluids. Some examples are geothermal energy extraction, ore mineral extraction, and radioactive waste isolation. While isothermal systems yield important results, polythermal (i.e., temperature gradient) systems more closely model reactions of fluid moving through a rock reservoir. The above examples will generally involve temperature gradients across the rock reservoir. A controlled temperature gradient circulation system was developed to help define these rock-fluid reactions. Six fine grained prisms are placed along the axis of a 113 cm pressure vessel. The prisms are at 72, 119, 161, 209, 270, and 310{degrees}C under flow conditions of 4 cc/min. at 1/3 kbar total pressure. In this experiment a granodiorite was reacted with initially distilled water.

  11. Acoustic radiation force on a particle in a temperature gradient

    NASA Technical Reports Server (NTRS)

    Collas, P.; Barmatz, M.

    1987-01-01

    After deriving a general expression for the acoustic radiation force on a small spherical particle of radius R in a standing wave field in a temperature gradient, attention is given to the case of a particle in a long tube chamber having a temperature gradient along the axis of symmetry. A simplification of the analysis is obtained through the introduction of the mass flux density potential. A general expression is presented for the time-averaged acoustic force; results of the new sample positions and restoring forces for a plane-wave mode are compared to the homogeneous case.

  12. Antiresonant guiding photonic crystal fibers for distributed temperature gradient measurements

    NASA Astrophysics Data System (ADS)

    Biswas, R.; Zeng, J.; Kandel, M.; Fam, A. T.; Cartwright, A. N.; Litchinitser, N. M.

    2011-11-01

    We propose, design, and experimentally demonstrate a novel, simple, distributed refractometric measurement technique based on unique spectral properties of antiresonant-guiding photonic crystal fibers for measuring temperature gradients. We use a simple and accurate analytical model and numerical simulations to guide our experiments. The proposed technique may find applications for monitoring and control of chemical and biological reactions in microfluidic systems.

  13. Multiple ion temperature gradient driven modes in transport barriers

    NASA Astrophysics Data System (ADS)

    Han, M. K.; Wang, Zheng-Xiong; Dong, J. Q.; Du, Huarong

    2017-04-01

    The ion temperature gradient (ITG) modes in transport barriers (TBs) of tokamak plasmas are numerically studied with a code solving gyrokinetic integral eigenvalue equations in toroidal configurations. It is found that multiple ITG modes with conventional and unconventional ballooning mode structures can be excited simultaneously in TBs with steep gradients of ion temperature and density. The characteristics of the modes, including the dependence of the mode frequencies, growth rate and structure on plasma parameters, are systematically investigated. Unconventional modes with large mode-number l (where l denotes a certain parity and peak number in ballooning space) dominate in the large {{k}θ}{ρs} region ({{k}θ}{ρs}≥slant 1.2 ), while the conventional mode with l=0 dominates in the medium {{k}θ}{ρs} region (0.4≤slant {{k}θ}{ρs}<1.2 ), and unconventional modes with small mode-number l dominate in the small {{k}θ}{ρs} region ({{k}θ}{ρs}<0.4 ). Thus, the {{k}θ}{ρs} spectra of these conventional and unconventional modes at steep gradients are qualitatively different from those of the conventional ITG modes at small or medium gradients, in which the growth rate of the only ITG mode with l=0 reaches maximum at the medium value {{k}θ}{ρs}=0.6 . Through scanning ion temperature gradient {{\\varepsilon}T\\text{i}} and density gradient {{\\varepsilon}n} separately, it is proven that the synergetic effect of {{\\varepsilon}T\\text{i}} and {{\\varepsilon}n} , rather than {{\\varepsilon}T\\text{i}} alone, drives the unconventional ITG modes in TBs. Moreover, it is found that the critical value of {{\\varepsilon}n} for driving the unconventional ITG modes with large l number increases with increasing {{k}θ}{ρs} . In addition, the effects of magnetic shear on conventional and unconventional ITG modes in the high confinement regime (H-mode) are analyzed in detail, and compared with equivalent effects on conventional modes in the low and intermediate gradient

  14. Temperature gradient osmometer and anomalies in freezing temperatures.

    PubMed

    Arav, A; Rubinsky, B

    1994-12-01

    We have developed a new device that measures freezing and melting temperatures in nanoliter volume samples and can be used as a "freezing point osmometer" with a resolution many orders of magnitude greater than that of existing freezing point osmometers. Using this device we found anomalies in the depression of the freezing temperature and thermal hysteresis in aqueous solutions of hydrophilic amino acids, polyamino acids, and lectins. These anomalies would not have been possible to detect with currently used technology. The compounds that produce anomalies in freezing temperature were reported in the literature as having the ability to bind to cell membranes. This suggests a relation between a molecule's ability to bind to cell membranes and its anomalous freezing temperature depression. The new freezing point osmometer and our results could be important for studying and understanding organic molecules and their interaction with membranes and water.

  15. Simulation of ion-temperature-gradient turbulence in tokamaks

    SciTech Connect

    Cohen, B I; Dimits, A M; Kim, C; Mattor, N; Nevins, W M; Parker, S E; Shumaker, D E

    1998-10-14

    Results are presented from nonlinear gyrokinetic simulations of toroidal ion temperature gradient (ITG) turbulence and transport. The gyrokinetic simulations are found to yield values of the thermal diffusivity significantly lower than gyrofluid or IFS-PPPL-model predictions. A new phenomenon of nonlinear effective critical gradients larger than the linear instability threshold gradients is observed, and is associated with undamped flux-surface-averaged shear flows. The nonlinear gyrokineic codes have passed extensive validity tests which include comparison against independent linear calculations, a series of nonlinear convergence tests, and a comparison between two independent nonlinear gyrokinetic codes. Our most realistic simulations to date have actual reconstructed equilibria from experiments and a model for dilution by impurity and beam ions. These simulations highlight the need for still more physics to be included in the simulations

  16. What causes cooling water temperature gradients in forested stream reaches?

    NASA Astrophysics Data System (ADS)

    Garner, G.; Malcolm, I. A.; Sadler, J. P.; Hannah, D. M.

    2014-06-01

    Previous studies have suggested that shading by riparian vegetation may reduce maximum water temperature and provide refugia for temperature sensitive aquatic organisms. Longitudinal cooling gradients have been observed during the daytime for stream reaches shaded by coniferous trees downstream of clear cuts, or deciduous woodland downstream of open moorland. However, little is known about the energy exchange processes that drive such gradients, especially in semi-natural woodland contexts, and in the absence of potentially confounding cool groundwater inflows. To address this gap, this study quantified and modelled variability in stream temperature and heat fluxes along an upland reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) where riparian landuse transitions from open moorland to semi-natural forest. Observations were made along a 1050 m reach using a spatially-distributed network of ten water temperature micro-loggers, three automatic weather stations and >200 hemispherical photographs, which were used to estimate incoming solar radiation. These data parameterised a high-resolution energy flux model, incorporating flow-routing, which predicted spatio-temporal variability in stream temperature. Variability in stream temperature was controlled largely by energy fluxes at the water column-atmosphere interface. Predominantly net energy gains occurred along the reach during daylight hours, and heat exchange across the bed-water column interface accounted for <1% of the net energy budget. For periods when daytime net radiation gains were high (under clear skies), differences between water temperature observations decreased in the streamwise direction; a maximum difference of 2.5 °C was observed between the upstream reach boundary and 1050 m downstream. Furthermore, daily maximum water temperature at 1050 m downstream was ≤1°C cooler than at the upstream reach boundary and lagged the occurrence of daily maximum water temperature

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

    PubMed

    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.

  18. Effect of wind and temperature gradients on received acoustic energy

    NASA Technical Reports Server (NTRS)

    Brienzo, Richard K.

    1990-01-01

    The effect of refraction due to wind and temperature gradients on energy received from low flying aircraft is examined. A series of helicopter and jet flyby's were recorded with a microphone array on two separate days, each with distinctly different meteorological conditions. Energy in the 100 to 200 Hertz band is shown as a function of aircraft range from the array, and compared with the output of the Fast Field Program.

  19. Cloud Radiative Feedback and Zonal Surface Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Yang, J.; Peltier, W. R.; Hu, Y.

    2013-12-01

    Two fully coupled atmosphere--ocean general circulation models, CCSM3 and CCSM4 are employed to investigate the response of the mean climate state of the tropics to a sequence of CO2 concentrations (pCO2) from 17.5 to 4576 ppmv. Analyses based upon both of thes models demonstrate that the zonal surface temperature gradient across the equatorial Pacific is a monotonic function of pCO2, decreasing as pCO2 is increased. It is found that increased pCO2 enhances both the strength of convection and the area of the western and central Pacific over which it occurs thereby leading to increased cloudiness, an increase in shortwave reflection, and therefore a diminution of surface temperature in the region. The opposite tendencies are realized in response to deacreasing pCO2. This study demonstrates that cloud radiative feedback promotes a weakening (strengthening) of the zonal surface temperature gradient as greenhouse gas concentrations increase (decrease), which has important implications for future climate change and also for the understanding of past warm and cold climates. Long-term mean sea surface temperature and and zonal SST gradient along the equatorial Pacific in CCSM3 (a and c) and CCSM4 (b and d). The CO2 level in CCSM3 is between 35 and 4576 ppmv while in CCSM4 it is between 17.5 and 2288 ppmv. The zonal SST gradient is defined by the maximum minus the minimum (red dots), or the area-averaged value of 145E--165E minus that of 120W--100W (blue squares).

  20. Salinity gradient power: influences of temperature and nanopore size

    NASA Astrophysics Data System (ADS)

    Tseng, Shiojenn; Li, Yu-Ming; Lin, Chih-Yuan; Hsu, Jyh-Ping

    2016-01-01

    Salinity gradient power is a promising, challenging, and readily available renewable energy. Among various methods for harvesting this clean energy, nanofluidic reverse electrodialysis (NRED) is of great potential. Since ionic transport depends highly on the temperature, so is the efficiency of the associated power generated. Here, we conduct a theoretical analysis on the influences of temperature and nanopore size on NRED, focusing on the temperature and nanopore size. The results gathered reveal that the maximum power increases with increasing temperature, but the conversion efficiency depends weakly on temperature. In general, the smaller the nanopore radius or the longer the nanopore, the better the ion selectivity. These results provide desirable and necessary information for improving the performance of NRED as well as designing relevant units in renewable energy plants.

  1. Basic experimental studies of ion and electron temperature gradient instabilities

    NASA Astrophysics Data System (ADS)

    Wei, Xiao

    Important issues related to the temperature gradient driven instabilities are investigated in the Columbia Linear Machine (CLM). The main purpose of this research is to produce, definitively identify and elucidate the basic physics of these instabilities. The first part of the thesis is about the study of Zonal flows (ZF) associated with the ion temperature gradient (ITG) modes. The difficult problem of the ZF detection has been solved via a novel diagnostic using the paradigm of frequency modulation (FM) in radio transmission. Through the discrete short time Fourier transform (STFT) analysis, the most important ZF characteristics such as low frequency (˜ 2kHz), poloidal symmetry ( m = 0), toroidal symmetry (k∥ = 0) and radial structure (kr ≠ 0) have been identified directly in the experiment. Furthermore, the ZF saturation physics has been investigated through unique feedback control diagnostics. Finally, the experimental results are compared with various existing theoretical models. The second part of the thesis is about the research on the electron temperature gradient (ETG) mode. ETG modes, which are believed to be one of the strongest candidates for the anomalous electron energy transport in plasmas, is difficult to detect in experiments because of its high frequency (˜ MHz ) and short wave length (k⊥rho e ≈ 1). Using a DC bias heating scheme of the core plasma, we are able to produce a sufficiently strong electron temperature gradient for exciting ETG modes in the CLM. A high frequency mode at ˜ 2MHz, with azimuthal wave number m ˜ 14--16 and parallel wave number k∥ ≈ 0.01cm-1, has been observed. This frequency is consistent with the result of a kinetic dispersion relation of slab ETG modes with an appropriate E⃗xB⃗ Doppler shift. The scaling of its fluctuation level with the temperature gradient scale length and the radial structure are found to be roughly consistent with theoretical expectations. With all the parametric signatures

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

    NASA Astrophysics Data System (ADS)

    Peng, Shuitao; Wang, Lu; Pan, Yuan

    2017-03-01

    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 implications of our results for experimental observations are discussed.

  3. 9519 biotite granodiorite reacted in a temperature gradient

    SciTech Connect

    Charles, R.W.; Bayhurst, G.K.

    1980-10-01

    A biotite granodiorite from the Fenton Hill Hot Dry Rock (HDR) geothermal system was reacted in a controlled temperature gradient with initially distilled water for 60d. Polished rock prisms were located in the gradient at 72, 119, 161, 209, 270, and 310/sup 0/C. Scanning electron microscope and microprobe analyses show the appearance of secondary phases: Ca-montmorillonite at 72/sup 0/C and 119/sup 0/C; zeolite, either stilbite or heulandite, at 161/sup 0/C; and another zeolite, thomsonite, at higher temperatures. Solution analyses show a steady state equilibrium exists between solution and overgrowths after about 2 weeks of reaction. The chemographic relations for the system are explored in some detail indicating the divariant assemblages may be placed in a reasonable sequence in intensive variable space. These relations predict high and low temperature effects not directly observed experimentally as well as relevant univariant equilibria. Solution chemistry indicates the Na-Ca-K geothermometer more adequately predicts temperature in this system than does the silica geothermometer.

  4. Decoupling of a neutron interferometer from temperature gradients

    NASA Astrophysics Data System (ADS)

    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.

  5. Decoupling of a neutron interferometer from temperature gradients.

    PubMed

    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.

  6. Testing Method for Heat Resistance Under Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Takagi, K.; Kawasaki, A.; Itoh, Y.; Harada, Y.; Ono, F.

    2007-12-01

    “Testing Method for Heat Resistance under Temperature Gradient” is a Japanese Industrial Standard (JIS) newly established by the Minister of Economy, Trade and Industry, after deliberations by the Japanese Industrial Standards Committee, in accordance with the Industrial Standardization Law. This standard specified the testing method for heat resistance under temperature gradient of materials and coated members of equipment exposed to high temperature, such as aircraft engines, gas turbines, and so on. This paper introduces the principle and overview of the established standard. In addition, taking the heat cycle test using the burner rig for instance, we specifically illustrate the acquirable data and their analysis in the standard. Monitoring of the effective thermal conductivity and acoustic emission particularly enables to the non-destructive evaluation of failure cycle.

  7. Ion temperature gradient turbulence in helical and axisymmetric RFP plasmas

    SciTech Connect

    Predebon, I.; Xanthopoulos, P.

    2015-05-15

    Turbulence induced by the ion temperature gradient (ITG) is investigated in the helical and axisymmetric plasma states of a reversed field pinch device by means of gyrokinetic calculations. The two magnetic configurations are systematically compared, both linearly and nonlinearly, in order to evaluate the impact of the geometry on the instability and its ensuing transport, as well as on the production of zonal flows. Despite its enhanced confinement, the high-current helical state demonstrates a lower ITG stability threshold compared to the axisymmetric state, and ITG turbulence is expected to become an important contributor to the total heat transport.

  8. Ion temperature gradient instability in a dusty plasma.

    PubMed

    Vranjes, J; Saleem, H; Poedts, S

    2004-05-01

    An analysis of the temperature-gradient-driven ( eta(i) ) instability of drift waves in dusty plasma is presented. Various limits that allow for the coupling of the drift wave with the dynamics of dust grains are discussed. In particular, the cases of tiny (magnetized) and relatively heavy (unmagnetized) grains are studied. It is shown that in both limits the behavior of the eta(i) mode is considerably affected by the dust dynamics. The growth rate turns out to be higher in the presence of dust, and the instability threshold is lower, resulting in a more unstable plasma.

  9. Ultrasonic noninvasive temperature estimation using echoshift gradient maps: simulation results.

    PubMed

    Techavipoo, Udomchai; Chen, Quan; Varghese, Tomy

    2005-07-01

    Percutaneous ultrasound-image-guided radiofrequency (rf) ablation is an effective treatment for patients with hepatic malignancies that are excluded from surgical resection due to other complications. However, ablated regions are not clearly differentiated from normal untreated regions using conventional ultrasound imaging due to similar echogenic tissue properties. In this paper, we investigate the statistics that govern the relationship between temperature elevation and the corresponding temperature map obtained from the gradient of the echoshifts obtained using consecutive ultrasound radiofrequency signals. A relationship derived using experimental data on the sound speed and tissue expansion variations measured on canine liver tissue samples at different elevated temperatures is utilized to generate ultrasound radiofrequency simulated data. The simulated data set is then utilized to statistically estimate the accuracy and precision of the temperature distributions obtained. The results show that temperature increases between 37 and 67 degrees C can be estimated with standard deviations of +/- 3 degrees C. Our results also indicate that the correlation coefficient between consecutive radiofrequency signals should be greater than 0.85 to obtain accurate temperature estimates.

  10. 43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as...

  11. 43 CFR 3252.14 - How must I complete a temperature gradient well?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration...

  12. 43 CFR 3252.14 - How must I complete a temperature gradient well?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration...

  13. 43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as...

  14. 43 CFR 3252.14 - How must I complete a temperature gradient well?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration...

  15. 43 CFR 3252.14 - How must I complete a temperature gradient well?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration...

  16. 43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as...

  17. 43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as...

  18. Acoustical power amplification and damping by temperature gradients.

    PubMed

    Biwa, Tetsushi; Komatsu, Ryo; Yazaki, Taichi

    2011-01-01

    Ceperley proposed a concept of a traveling wave heat engine ["A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3.

  19. Local Glass Transition Temperature Gradients Near Polymer-Polymer Interfaces

    NASA Astrophysics Data System (ADS)

    Baglay, Roman; Roth, Connie

    2015-03-01

    For decades the glass transition in confined systems has been studied with the hopes of uncovering the governing length scales that impact these dynamics. However, understanding length scales of local gradients in glass transition temperature (Tg) near a free surface have been hampered by limitations of how to treat the enhanced mobility at the free surface theoretically. We have previously reported on the local Tg in multilayer structures made from high molecular weight polystyrene (PS) and poly(n-butyl methacrylate) (PnBMA), a weakly immiscible system with a ~ 7 nm interfacial width. Using ultrathin (10-15 nm) pyrene-labeled layers inserted into the multilayer structure at different positions (z) from the glassy-rubbery interface, we were able to map the local Tg(z) profile across this glassy-rubbery interface with temperature-dependent fluorescence intensity measurements. Our work revealed an asymmetric local mobility gradient propagating hundreds of nanometers away from the glassy-rubbery PS-PnBMA interface into the glassy PS and rubbery PnBMA sides before bulk Tgs were recovered far from the interface. Here we extend these measurements to investigate how the local Tg(z) profile in PS varies when in contact with a variety of immiscible polymers whose Tgs vary between +90 K to -80 K relative to the Tg of PS, so-called hard vs soft confinement.

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

    PubMed

    Elsgaard, Lars; Jørgensen, Leif Wagner

    2002-03-01

    A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, 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 (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced

  1. Fluid simulations of toroidal ion temperature gradient turbulence

    SciTech Connect

    Sandberg, I.; Isliker, H.; Pavlenko, V.P.; Hizanidis, K.; Vlahos, L.

    2006-02-15

    The evolution of the toroidal ion temperature gradient mode instability is numerically studied by using the equations based on the standard reactive fluid model. The long-term dynamics of the instability are investigated using random-phase, small-amplitude fluctuations for initial conditions. The main events during the evolution of the instability that lead to the formation of large-scale coherent structures are described and the role of the dominant nonlinearities is clarified. The polarization drift nonlinearity leads to the inverse energy cascade while the convective ion heat nonlinearity is responsible for the saturation of the instability. Finally, the sensitivity of the saturated state to the initial plasma conditions is examined.

  2. Coherent structures in ion temperature gradient turbulence-zonal flow

    SciTech Connect

    Singh, Rameswar; Singh, R.; Kaw, P.; Gürcan, Ö. D.; Diamond, P. H.

    2014-10-15

    Nonlinear stationary structure formation in the coupled ion temperature gradient (ITG)-zonal flow system is investigated. The ITG turbulence is described by a wave-kinetic equation for the action density of the ITG mode, and the longer scale zonal mode is described by a dynamic equation for the m = n = 0 component of the potential. Two populations of trapped and untrapped drift wave trajectories are shown to exist in a moving frame of reference. This novel effect leads to the formation of nonlinear stationary structures. It is shown that the ITG turbulence can self-consistently sustain coherent, radially propagating modulation envelope structures such as solitons, shocks, and nonlinear wave trains.

  3. Temperature effects on fish production across a natural thermal gradient.

    PubMed

    O'Gorman, Eoin J; Ólafsson, Ólafur P; Demars, Benoît O L; Friberg, Nikolai; Guðbergsson, Guðni; Hannesdóttir, Elísabet R; Jackson, Michelle C; Johansson, Liselotte S; McLaughlin, Órla B; Ólafsson, Jón S; Woodward, Guy; Gíslason, Gísli M

    2016-09-01

    Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4-25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five-month mark-recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient-replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning.

  4. Measurement of temperature and temperature gradient in millimeter samples by chlorine NQR

    NASA Astrophysics Data System (ADS)

    Lužnik, Janko; Pirnat, Janez; Trontelj, Zvonko

    2009-09-01

    A mini-thermometer based on the 35Cl nuclear quadrupole resonance (NQR) frequency temperature dependence in the chlorates KClO3 and NaClO3 was built and successfully tested by measuring temperature and temperature gradient at 77 K and higher in about 100 mm3 active volume of a mini Joule-Thomson refrigerator. In the design of the tank-circuit coil, an array of small coils connected in series enabled us (a) to achieve a suitable ratio of inductance to capacity in the NQR spectrometer input tank circuit, (b) to use a single crystal of KClO3 or NaClO3 (of 1-2 mm3 size) in one coil as a mini-thermometer with a resolution of 0.03 K and (c) to construct a system for measuring temperature gradients when the spatial coordinates of each chlorate single crystal within an individual coil are known.

  5. Davydov soliton evolution in temperature gradients driven by hyperbolic waves

    NASA Astrophysics Data System (ADS)

    Herrera, J.; Maza, M. A.; Minzoni, A. A.; Smyth, Noel F.; Worthy, Annette L.

    2004-04-01

    In the present work the evolution of a Davydov soliton in an inhomogeneous medium will be considered. The Zakharov system of equations, which describes this soliton, consists of a perturbed non-linear Schrödinger (NLS) type equation plus a forced wave equation. This system is not exactly integrable for a homogeneous medium and its Lagrangian is non-local. It has recently been shown that this type of soliton has a long enough lifetime, even for non-zero temperature, so as to be a possible mechanism for the transfer of energy along an α helix. In the present work, the effect of temperature inhomogeneities on the behaviour of this soliton will be studied. As the soliton propagates through such an inhomogeneity, both dispersive and non-dispersive waves are generated. The stability of the soliton to this radiation is studied. The evolution of the Davydov soliton solution of the Zakharov equations in an inhomogeneous medium will be studied using an approximate method based on averaged conservation laws, which results in ordinary differential equations for the pulse parameters. It is shown that the inclusion of the effect of the dispersive radiation shed by the soliton for the NLS equation and the non-dispersive (hyperbolic) radiation shed by the soliton for the forced wave equation is vital for an accurate description of the evolution of the Davydov soliton. It is found that the soliton is stable even in the presence of hyperbolic radiation and that the temperature gradients have significant effects on the propagation of the soliton, even to the extent of reversing its motion.

  6. Tightly linked zonal and meridional sea surface temperature gradients over the past five million years

    NASA Astrophysics Data System (ADS)

    Fedorov, Alexey V.; Burls, Natalie J.; Lawrence, Kira T.; Peterson, Laura C.

    2015-12-01

    The climate of the tropics and surrounding regions is defined by pronounced zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature. These gradients control zonal and meridional atmospheric circulations, and thus the Earth’s climate. Global cooling over the past five million years, since the early Pliocene epoch, was accompanied by the gradual strengthening of these temperature gradients. Here we use records from the Atlantic and Pacific oceans, including a new alkenone palaeotemperature record from the South Pacific, to reconstruct changes in zonal and meridional sea surface temperature gradients since the Pliocene, and assess their connection using a comprehensive climate model. We find that the reconstructed zonal and meridional temperature gradients vary coherently over this time frame, showing a one-to-one relationship between their changes. In our model simulations, we systematically reduce the meridional sea surface temperature gradient by modifying the latitudinal distribution of cloud albedo or atmospheric CO2 concentration. The simulated zonal temperature gradient in the equatorial Pacific adjusts proportionally. These experiments and idealized modelling indicate that the meridional temperature gradient controls upper-ocean stratification in the tropics, which in turn controls the zonal gradient along the equator, as well as heat export from the tropical oceans. We conclude that this tight linkage between the two sea surface temperature gradients posits a fundamental constraint on both past and future climates.

  7. 43 CFR 3252.12 - How deep may I drill a temperature gradient well?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your...

  8. 43 CFR 3252.12 - How deep may I drill a temperature gradient well?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your...

  9. 43 CFR 3252.12 - How deep may I drill a temperature gradient well?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your...

  10. 43 CFR 3252.12 - How deep may I drill a temperature gradient well?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your...

  11. Performing microchannel temperature cycling reactions using reciprocating reagent shuttling along a radial temperature gradient.

    PubMed

    Cheng, Ji-Yen; Hsieh, Chien-Ju; Chuang, Yung-Chuan; Hsieh, Jing-Ru

    2005-06-01

    This study develops a novel temperature cycling strategy for executing temperature cycling reactions in laser-etched poly(methylmethacrylate) (PMMA) microfluidic chips. The developed microfluidic chip is circular in shape and is clamped in contact with a circular ITO heater chip of an equivalent diameter. Both chips are fabricated using an economic and versatile laser scribing process. Using this arrangement, a self-sustained radial temperature gradient is generated within the microfluidic chip without the need to thermally isolate the different temperature zones. This study demonstrates the temperature cycling capabilities of the reported microfluidic device by a polymerase chain reaction (PCR) process using ribulose 1,5-bisphosphate carboxylase large subunit (rbcL) gene as a template. The temperature ramping rate of the sample inside the microchannel is determined from the spectral change of a thermochromic liquid crystal (TLC) solution pumped into the channel. The present results confirm that a rapid thermal cycling effect is achieved despite the low thermal conductivity of the PMMA substrate. Using IR thermometry, it is found that the radial temperature gradient of the chip is approximately 2 degrees C mm(-1). The simple system presented in this study has considerable potential for miniaturizing complex integrated reactions requiring different cycling parameters.

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

    PubMed

    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

  13. Effect of temperature gradient on zinc oxide nano particles synthesized at low reaction temperatures

    NASA Astrophysics Data System (ADS)

    Koutu, Vaibhav; Shastri, Lokesh; Malik, M. M.

    2017-03-01

    Zinc oxide samples were synthesized at different reaction temperatures (70 °C–110 °C) by surfactant-free co-precipitation method using temperature gradient. Formation of hexagonal wurtzite structure of the ZnO samples is confirmed from x-ray diffraction (XRD) studies. This study further suggests reduction in crystallite size from 33 nm to 24 nm with increase in reaction temperature which is reconfirmed by field emission scanning electron microscopy (FE-SEM). Optical spectroscopy studies of these samples show significant peak shift towards higher energy with maximum photoluminescence (PL) emissions between 390 nm to 575 nm region of the visible spectrum. This evident inverse relationship between optical properties of ZnO nano particles and reaction temperature may be attributed to the temperature gradient causing rapid nucleation during the synthesis process. With these notable properties this study suggests that, ZnO nano particles may be useful for making Nano electronic devices, Sensors, Nano medicines, GATE Dielectrics, Photovoltaic devices etc.

  14. Temperature Versus Salinity Gradients Below the Ocean Mixed Layer

    DTIC Science & Technology

    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

  15. On detonation initiation by a temperature gradient for a detailed chemical reaction models

    NASA Astrophysics Data System (ADS)

    Liberman, M. A.; Kiverin, A. D.; Ivanov, M. F.

    2011-04-01

    The evolution from a temperature gradient to a detonation is investigated for combustion mixture whose chemistry is governed by a detailed chemical kinetics. We show that a detailed chemical reaction model has a profound effect on the spontaneous wave concept for detonation initiation by a gradient of reactivity. The evolution to detonation due to a temperature gradient is considered for hydrogen-oxygen and hydrogen-air mixtures at different initial pressures. It is shown that the minimal length of the temperature gradient for which a detonation can be ignited is much larger than that predicted from a one-step chemical model.

  16. Effect of transverse velocity and temperature gradients on sound attenuation in two-dimensional ducts

    NASA Technical Reports Server (NTRS)

    Nayfeh, A. H.; Sun, J.

    1974-01-01

    An investigation is described of the effect of transverse mean-velocity and temperature gradients on sound attenuation in acoustically treated two-dimensional ducts. The results show that cooling the duct walls leads to channeling the sound toward the walls for both downstream and upstream propagation. The effect of mean-temperature gradients on the attenuation rates of the lowest three modes can be as important as the effect of mean-velocity gradients.

  17. 43 CFR 3252.15 - When must I abandon a temperature gradient well?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well?...

  18. 43 CFR 3252.16 - How must I abandon a temperature gradient well?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well?...

  19. 43 CFR 3252.16 - How must I abandon a temperature gradient well?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well?...

  20. 43 CFR 3252.16 - How must I abandon a temperature gradient well?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well?...

  1. 43 CFR 3252.15 - When must I abandon a temperature gradient well?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well?...

  2. 43 CFR 3252.15 - When must I abandon a temperature gradient well?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well?...

  3. 43 CFR 3252.16 - How must I abandon a temperature gradient well?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well?...

  4. 43 CFR 3252.15 - When must I abandon a temperature gradient well?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well?...

  5. Temperature logging of groundwater in bedrock wells for geothermal gradient characterization in New Hampshire, 2012

    USGS Publications Warehouse

    Degnan, James; Barker, Gregory; Olson, Neil; Wilder, Leland

    2012-01-01

    Maximum groundwater temperatures at the bottom of the logs were between 11.7 and 17.3 degrees Celsius. Geothermal gradients were generally higher than typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 5 of the 10 wells studied but only obscured the portion of the geothermal gradient signal where groundwater actually flowed through the well. Temperature gradients varied by mapped bedrock type but can also vary by differences in mineralogy or rock type within the wells.

  6. Acoustic response of a rectangular waveguide with a strong transverse temperature gradient

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.

    1989-01-01

    An acoustic wave equation was developed for a perfect gas with spatially-variable temperature. The strong-gradient wave equation was used to analyze the response of a rectangular wave guide containing a thermally-stratified gas. It was assumed that the temperature gradient is constant, representing one-dimensional heat transfer with a constant coefficient of conductivity. The analysis of the waveguide shows that the resonant frequencies of the waveguide are shifted away from the values that would be expected from the average temperature of the waveguide. For small gradients, the frequency shift is proportional to the square of the gradient. The factor of proportionality is a quadratic function of the natural frequency of the waveguide with uniform temperature. An experiment is designed to verify the essential features of the strong-gradient theory.

  7. Extending the nonequilibrium square-gradient model with temperature-dependent influence parameters

    NASA Astrophysics Data System (ADS)

    Magnanelli, Elisa; Wilhelmsen, Øivind; Bedeaux, Dick; Kjelstrup, Signe

    2014-09-01

    Nonequilibrium interface phenomena play a key role in crystallization, hydrate formation, pipeline depressurization, and a multitude of other examples. Square gradient theory extended to the nonequilibrium domain is a powerful tool for understanding these processes. The theory gives an accurate prediction of surface tension at equilibrium, only with temperature-dependent influence parameters. We extend in this work the nonequilibrium square gradient model to have temperature-dependent influence parameters. The extension leads to thermodynamic quantities which depend on temperature gradients. Remarkably the Gibbs relation proposed in earlier work is still valid. Also for the extended framework, the "Gibbs surface" described by excess variables is found to be in local equilibrium. The temperature-dependent influence parameters give significantly different interface resistivities (˜9%-50%), due to changed density gradients and additional terms in the enthalpy. The presented framework facilitates a more accurate description of transport across interfaces with square gradient theory.

  8. Electron temperature critical gradient and transport stiffness in DIII-D

    SciTech Connect

    Smith, Sterling P.; Petty, Clinton C.; White, Anne E.; Holland, Christopher; Bravenec, Ronald; Austin, Max E.; Zeng, Lei; Meneghini, Orso

    2015-07-06

    The electron energy flux has been probed as a function of electron temperature gradient on the DIII-D tokamak, in a continuing effort to validate turbulent transport models. In the scan of gradient, a critical electron temperature gradient has been found in the electron heat fluxes and stiffness at various radii in L-mode plasmas. The TGLF reduced turbulent transport model [G.M. Staebler et al, Phys. Plasmas 14, 055909 (2007)] and full gyrokinetic GYRO model [J. Candy and R.E. Waltz, J. Comput. Phys. 186, 545 (2003)] recover the general trend of increasing electron energy flux with increasing electron temperature gradient scale length, but they do not predict the absolute level of transport at all radii and gradients. Comparing the experimental observations of incremental (heat pulse) diffusivity and stiffness to the models’ reveals that TGLF reproduces the trends in increasing diffusivity and stiffness with increasing electron temperature gradient scale length with a critical gradient behavior. Furthermore, the critical gradient of TGLF is found to have a dependence on q95, contrary to the independence of the experimental critical gradient from q95.

  9. Electron temperature critical gradient and transport stiffness in DIII-D

    DOE PAGES

    Smith, Sterling P.; Petty, Clinton C.; White, Anne E.; ...

    2015-07-06

    The electron energy flux has been probed as a function of electron temperature gradient on the DIII-D tokamak, in a continuing effort to validate turbulent transport models. In the scan of gradient, a critical electron temperature gradient has been found in the electron heat fluxes and stiffness at various radii in L-mode plasmas. The TGLF reduced turbulent transport model [G.M. Staebler et al, Phys. Plasmas 14, 055909 (2007)] and full gyrokinetic GYRO model [J. Candy and R.E. Waltz, J. Comput. Phys. 186, 545 (2003)] recover the general trend of increasing electron energy flux with increasing electron temperature gradient scale length,more » but they do not predict the absolute level of transport at all radii and gradients. Comparing the experimental observations of incremental (heat pulse) diffusivity and stiffness to the models’ reveals that TGLF reproduces the trends in increasing diffusivity and stiffness with increasing electron temperature gradient scale length with a critical gradient behavior. Furthermore, the critical gradient of TGLF is found to have a dependence on q95, contrary to the independence of the experimental critical gradient from q95.« less

  10. Characterization of thermotropism in primary roots of maize: dependence on temperature and temperature gradient, and interaction with gravitropism

    NASA Technical Reports Server (NTRS)

    Poff, K. L.

    1991-01-01

    Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

  11. Acupuncture needles and the Seebeck effect: do temperature gradients produce electrostimulation?

    PubMed

    Cohen, M; Kwok, G; Cosic, I

    1997-01-01

    Acupuncture may act through modifying bioelectric events and this may occur through different mechanisms including the application of external currents. According to the Seebeck effect which produces a potential difference when a temperature gradient is placed across a conductor, the physical properties of acupuncture needles may produce internal currents due to the temperature gradient across the needle when placed insitu. Such currents were detected when needles were differentially heated and these currents were found to be in the range capable of producing biological effects. The traditional design of acupuncture needles and traditional needle manipulations seem to maintain a temperature gradient across the needle and thus enhance the Seebeck effect.

  12. Forced and Unforced Changes of Indian Ocean Temperature and Land-Sea Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Achutarao, K. M.; Thanigachalam, A.

    2015-12-01

    Sea surface temperature (SST) over the Indian Ocean is directly connected with circulation, winds, precipitation, humidity, etc. over India. Increased SSTs are a major consequence of climate change driven largely by anthropogenic factors. Recent literature points to weakening of the Indian Summer Monsoon possibly because of decreased land-sea temperature gradient due to faster rate of warming of the oceans compared to land regions. We examine changes in the SST over the Indian Ocean using two observational datasets; HadISST (v1.1) and ERSST (v3b). Based on trend differences between two time periods (1979-2009 and 1948-1978) we identify four regions in the Indian Ocean with different signatures of change - Bay of Bengal (BOB), Arabian Sea (AS), Southwest Indian Ocean (SWIO), and Southeast Indian Ocean (SEIO). We first quantify the extent to which the SST trends over multiple time-scales (20, 30, 50 and 100-years) are outside of the range expected from internal variability of the climate system. We make use of output data from long control run simulations from the Coupled Model Intercomparison Project Phase-5 (CMIP5) database in order to estimate the contribution of external forcings to the observed trends. Using optimal fingerprint Detection and Attribution methods we quantify the contributions of various natural and anthropogenic forcings by making use of the suite of experiments (piControl, historical, historicalNat, historicalAnt, historicalGHG, and historicalAA) from CMIP5 are used in this study. We will also address the question of what drives the observed weakening of land-ocean temperature gradients.

  13. Continuous gradient temperature Raman spectroscopy of oleic and linoleic acids from -100 to 50°C

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 DS...

  14. Integral eigenmode analysis of shear flow effects on the ion temperature gradient mode

    SciTech Connect

    Artun, M.; Reynders, J.V.M.; Tang, W.M.

    1993-07-01

    Previous numerical and analytic kinetic studies have investigated the influence of velocity shear on the ion temperature gradient (ITG) mode. These studies relied on a differential approximation to study mode structures with k[sub [perpendicular

  15. Gradient temperature Raman spectroscopy identifies flexible sites in proline and alanine peptides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous thermo dynamic Raman spectroscopy (TDRS) 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 TDRS...

  16. Thermophoresis of dissolved molecules and polymers: Consideration of the temperature-induced macroscopic pressure gradient.

    PubMed

    Semenov, Semen; Schimpf, Martin

    2004-01-01

    The movement of molecules and homopolymer chains dissolved in a nonelectrolyte solvent in response to a temperature gradient is considered a consequence of temperature-induced pressure gradients in the solvent layer surrounding the solute molecules. Local pressure gradients are produced by nonuniform London-van der Waals interactions, established by gradients in the concentration (density) of solvent molecules. The density gradient is produced by variations in solvent thermal expansion within the nonuniform temperature field. The resulting expression for the velocity of the solute contains the Hamaker constants for solute-solvent and solute-solute interactions, the radius of the solute molecule, and the viscosity and cubic coefficient of thermal expansion of the solvent. In this paper we consider an additional force that arises from directional asymmetry in the interaction between solvent molecules. In a closed cell, the resulting macroscopic pressure gradient gives rise to a volume force that affects the motion of dissolved solutes. An expression for this macroscopic pressure gradient is derived and the resulting force is incorporated into the expression for the solute velocity. The expression is used to calculate thermodiffusion coefficients for polystyrene in several organic solvents. When these values are compared to those measured in the laboratory, the consistency is better than that found in previous reports, which did not consider the macroscopic pressure gradient that arises in a closed thermodiffusion cell. The model also allows for the movement of solute in either direction, depending on the relative values of the solvent and solute Hamaker constants.

  17. Atmospheric study relating to pad lift-off and entry landing. [effects of midlatitude temperature gradients

    NASA Technical Reports Server (NTRS)

    King, R. L.

    1977-01-01

    A relationship between the atmospheric general circulation and geophysical hydrodynamic experiments was sought by attempting to find a relationship between wave number and temperature gradient at mid-latitudes at 500 mb. To this end data were gathered from four winter seasons and analyzed. The statistical analysis failed to provide convincing support for the hypothesis of a direct relationship between wave number and temperature gradient, although an indication that the transient waves may be so related was noted.

  18. Effect of temperature gradient on the optical quality of mercurous chloride crystals

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Davies, D. K.; Gottlieb, M.; Henningsen, T.; Mazelsky, R.

    1989-01-01

    Single crystals of mercurous chloride were grown at temperature gradients of 8, 11 and 17 K/cm by the physical vapor transport method. The optical quality of these crystals was evaluated by measuring bulk scattering and inhomogeneity of refractive index by birefringence interferometry. It was observed that a high temperature gradient at the solid-vapor interface induced thermal stresses and crystals showed higher scattering and irregular fringes.

  19. Movement of Rhyzopertha dominica in response to temperature gradients in stored wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The movement and temperature preference of Rhyzopertha dominica was determined in a 56 cm diameter cylinder with 9 cm high sides containing 19.9 kg of hard red winter wheat. Two temperature gradients were tested over a 24 h period: 42 to 20°C and 24 to 20°C with the cooler temperature being on the p...

  20. Effect of axial temperature gradient on chromatographic efficiency under adiabatic conditions.

    PubMed

    Horváth, Krisztián; Horváth, Szabolcs; Lukács, Diána

    2017-02-03

    The effect of axial temperature gradient on the chromatographic efficiency was studied under adiabatic conditions by a modeling approach. The equilibrium-dispersive model of chromatography was used for the calculations. The model was extended by taking into account the axial temperature gradient. The results show that due to the temperature gradient, there are retention and migration velocity gradients in the column. Since the retention factor, k, is not constant in the column, k cannot be calculated as the ratio of net retention and hold-up times. As a result of the gradual increase of migration velocity, the retention times of solutes decrease as the slope of temperature gradient increases. In addition, the band in the column have extra broadening due to larger migration velocity of the front of band. The width of bands becomes larger at larger change of temperature. In the same time, however, the release velocity of the compounds from the column is increasing as ΔT increases. Accordingly, an apparent peak compression effect makes the peaks thinner. As a result of the two counteracting effects (peak expansion, apparent peak compression) the column efficiency does not change significantly in case of axial temperature gradient under adiabatic conditions. The resolutions, however, decrease slightly due to the decrease of retention times.

  1. Detonation Initiation by a Temperature Gradient for a Detailed Chemical Reaction Models

    NASA Astrophysics Data System (ADS)

    Liberman, Michael; Kiverin, Alexey; Chukalovsky, Alexander; Ivanov, Mikhail

    2011-04-01

    The evolution from a temperature gradient to a detonation is investigated using high resolution numerical simulations for combustion mixture whose chemistry is governed by a detailed chemical kinetics. We employ a model representing an initial linear temperature gradient in the fuel. Emphasis is on comparing the results with previous studies that used simple one-step kinetics. It is shown that the evolution to detonation from temperature nonuniformities is considerably different for one-step kinetics models than for chain-branching kinetic models and it is different in different fuels for the same initial conditions. A detailed chemical model has a profound effect on the validity of Zel'dovich's spontaneous wave concept for detonation initiation by a gradient of reactivity. The evolution to detonation from a temperature gradient is considered for hydrogen-air and methane-air mixtures at different initial pressures. The analysis shows that for a detailed chemical kinetics the temperature gradients, which was thought to appear in the form of hot spots and the like, are not satisfy the criteria to initiate detonation, and the gradient mechanism can not be origin of the deflagration-to-detonation transition.

  2. Results of temperature gradient and heat flow in Santiam Pass Area, Oregon, Volume 1

    SciTech Connect

    Cox, B.L.; Gardner, M.C.; Koenig, J.B.

    1981-08-01

    The conclusions of this report are: (1) There is a weakly defined thermal anomaly within the area examined by temperature-gradient holes in the Santiam Pass area. This is a relict anomaly showing differences in permeability between the High Cascades and Western Cascades areas, more than a fundamental difference in shallow crustal temperatures. (2) The anomaly as defined by the 60 F isotherms at 400 feet follows a north-south trend immediately westward of the Cascade axis in the boundary region. It is clear that all holes spudded into High Cascades rocks result in isothermal and reversal gradients. Holes spudded in Western Cascades rocks result in positive gradients. (3) Cold groundwater flow influences and masks temperature gradients in the High Cascades to a depth of at least 700 feet, especially eastward from the major north-south trending faults. Pleistocene and Holocene rocks are very permeable aquifers. (4) Shallow gradient drilling in the lowlands westward of the faults provides more interpretable information than shallow drilling in the cold-water recharge zones. Topographic and climatological effects can be filtered out of the temperature gradient results. (5) The thermal anomaly seems to have 2 centers: one in the Belknap-Foley area, and one northward in the Sand Mountain area. The anomalies may or may not be connected along a north-south trend. (6) A geothermal effect is seen in holes downslope of the Western-High Cascade boundary. Mixing with cold waters is a powerful influence on temperature gradient data. (7) The temperature-gradient program has not yet examined and defined the geothermal resources potential of the area eastward of the Western Cascades-High Cascades boundary. Holes to 1500-2000 feet in depth are required to penetrate the high permeability-cold groundwater regime. (8) Drilling conditions are unfavorable. There are very few accessible level drill sites. Seasonal access problems and environmental restrictions together with frequent lost

  3. Interaction between neoclassical effects and ion temperature gradient turbulence in gradient- and flux-driven gyrokinetic simulations

    NASA Astrophysics Data System (ADS)

    Oberparleiter, M.; Jenko, F.; Told, D.; Doerk, H.; Görler, T.

    2016-04-01

    Neoclassical and turbulent transport in tokamaks has been studied extensively over the past decades, but their possible interaction remains largely an open question. The two are only truly independent if the length scales governing each of them are sufficiently separate, i.e., if the ratio ρ* between ion gyroradius and the pressure gradient scale length is small. This is not the case in particularly interesting regions such as transport barriers. Global simulations of a collisional ion-temperature-gradient-driven microturbulence performed with the nonlinear global gyrokinetic code Gene are presented. In particular, comparisons are made between systems with and without neoclassical effects. In fixed-gradient simulations, the modified radial electric field is shown to alter the zonal flow pattern such that a significant increase in turbulent transport is observed for ρ*≳1 /300 . Furthermore, the dependency of the flux on the collisionality changes. In simulations with fixed power input, we find that the presence of neoclassical effects decreases the frequency and amplitude of intermittent turbulent transport bursts (avalanches) and thus plays an important role for the self-organisation behaviour.

  4. Flat meridional temperature gradient in the early Eocene in the subsurface rather than surface ocean

    NASA Astrophysics Data System (ADS)

    Ho, Sze Ling; Laepple, Thomas

    2016-08-01

    The early Eocene (49-55 million years ago) is a time interval characterized by elevated surface temperatures and atmospheric CO2 (refs ,), and a flatter-than-present latitudinal surface temperature gradient. The multi-proxy-derived flat temperature gradient has been a challenge to reproduce in model simulations, especially the subtropical warmth at the high-latitude surface oceans, inferred from the archaeal lipid-based palaeothermometry, . Here we revisit the interpretation by analysing a global collection of multi-proxy temperature estimates from sediment cores spanning millennia to millions of years. Comparing the variability between proxy types, we demonstrate that the present interpretation overestimates the magnitude of past climate changes on all timescales. We attribute this to an inappropriate calibration, which reflects subsurface ocean but is calibrated to the sea surface, where the latitudinal temperature gradient is steeper. Recalibrating the proxy to the temperatures of subsurface ocean, where the signal is probably formed, yields colder -temperatures and latitudinal gradient consistent with standard climate model simulations of the Eocene climate, invalidating the apparent, extremely warm polar sea surface temperatures. We conclude that there is a need to reinterpret -inferred marine temperature records in the literature, especially for reconstructions of past warm climates that rely heavily on this proxy as reflecting subsurface ocean.

  5. Muscle temperature gradients in humans during cold water immersion hypothermia and rewarming

    SciTech Connect

    Bristow, G.K.; Giesbrecht, G.G. Univ. of Calgary, Alberta )

    1991-03-11

    Muscle temperature gradients have not been measured in hypothermic man. Thigh and calf muscle temperatures were measured by indwelling multisensor thermocouples (deep (D) 4.5 cm, and superficial (S) 1.5 cm beneath the skin) on five healthy male subjects immersed in 8C water for 70 minutes on two occasions. Measurements continued during 55 minutes of rewarming by two methods; either treadmill exercise (EX) or shivering (SH). Esophageal temperature (T{sub es}) was also measured. Prior to immersion, deep thigh and calf temperatures were 36.1 and 34.8C respectively and temperature gradients were similar in both thigh and calf. At the end of cooling deep thigh temperature fell 3.0C and the gradient increased to 8.1C. Corresponding values for the calf were 10.3 and 6.4C respectively. Both rewarming methods were terminated at a T{sub es} of 35.7C. EX and SH caused similar changes in thigh temperatures; deep temperature increased 2.1 and 1.9C and gradients decreased to 2.7 and 2.6C respectively. However, an increase in deep calf temperature during EX was absent during SH. During cooling, muscle blood flow would appear to be better maintained in the thigh than the calf. Thigh blood flow increases similarly during EX and SH. However, in calf, blood flow increases during EX but not SH.

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

    SciTech Connect

    Li, Chengmingyue; Gan, Xiaosong; Li, Xiangping; Gu, Min

    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.

  7. Band-broadening in capillary zone electrophoresis with axial temperature gradients.

    PubMed

    Xuan, Xiangchun; Li, Dongqing

    2005-01-01

    It is widely accepted that Joule heating effects yield radial temperature gradients in capillary zone electrophoresis (CZE). The resultant parabolic profile of electrophoretic velocity of analyte molecules is believed to increase the band-broadening via Taylor-Aris dispersion. This typically insignificant contribution, however, cannot explain the decrease in separation efficiency at high electric fields. We show that the additional band-broadening due to axial temperature gradients may provide the answer. These axial temperature variations result from the change of heat transfer condition along the capillary, which is often present in CZE with thermostating. In this case, the electric field becomes nonuniform due to the temperature dependence of fluid conductivity, and hence the induced pressure gradient is brought about to meet the mass continuity. This modification of the electroosmotic flow pattern can cause significant band-broadening. An analytical model is developed to predict the band-broadening in CZE with axial temperature gradients in terms of the theoretical plate height. We find that the resultant thermal plate height can be very high and even comparable to that due to molecular diffusion. This thermal plate height is much higher than that due to radial temperature gradients alone. The analytical model explains successfully the phenomena observed in previous experiments.

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

    PubMed

    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.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26633401

  10. Lower hybrid drift instability with temperature gradient in a perpendicular shock wave

    NASA Technical Reports Server (NTRS)

    Zhou, Y. M.; Wong, H. K.; Wu, C. S.

    1983-01-01

    Finite beta effects and an electron temperature gradient are included in the present study of the perpendicular bow shock geometry's lower hybrid instability, where the flute mode that is stable at the shock for constant electron temperature is destabilized in the case of a sufficiently great temperature gradient. Numerical solutions are given for cases in which the ion distribution is either drifting Maxwellian or consists of two Maxwellians, to represent the effect of reflected ions at the shock. A discussion is presented of the implications of results obtained for ion and electron heating and electron acceleration at the bow shock.

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

    EPA Science Inventory

    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 ...

  12. A Simple Temperature Gradient Apparatus To Determine Thermal Preference in "Daphnia."

    ERIC Educational Resources Information Center

    Fenske, Christiane; McCauley, Robert

    2002-01-01

    Explores the dominant factor controlling the distribution of Daphnia. Describes components of a temperature gradient apparatus that can be assembled from materials readily obtainable in the laboratory and hardware stores. Investigates whether the mean depth of Daphnia is determined by temperature. (KHR)

  13. Vertical gradient in soil temperature stimulates development and increases biomass accumulation in barley.

    PubMed

    Füllner, K; Temperton, V M; Rascher, U; Jahnke, S; Rist, R; Schurr, U; Kuhn, A J

    2012-05-01

    We have detailed knowledge from controlled environment studies on the influence of root temperature on plant performance, growth and morphology. However, in all studies root temperature was kept spatially uniform, which motivated us to test whether a vertical gradient in soil temperature affected development and biomass production. Roots of barley seedlings were exposed to three uniform temperature treatments (10, 15 or 20°C) or to a vertical gradient (20-10°C from top to bottom). Substantial differences in plant performance, biomass production and root architecture occurred in the 30-day-old plants. Shoot and root biomass of plants exposed to vertical temperature gradient increased by 144 respectively, 297%, compared with plants grown at uniform root temperature of 20°C. Additionally the root system was concentrated in the upper 10cm of the soil substrate (98% of total root biomass) in contrast to plants grown at uniform soil temperature of 20°C (86% of total root biomass). N and C concentrations in plant roots grown in the gradient were significantly lower than under uniform growth conditions. These results are important for the transferability of 'normal' greenhouse experiments where generally soil temperature is not controlled or monitored and open a new path to better understand and experimentally assess root-shoot interactions.

  14. A seismological determination of the temperature gradient in D″ beneath the western Pacific

    NASA Astrophysics Data System (ADS)

    Kuo, Ban-Yuan; Chen, Chin-Wu

    2005-05-01

    The temperature gradient of the thermal boundary layer in the D″ region is one of the basic properties of the mantle that remains difficult to evaluate. We characterize this quantity for a region in the western Pacific using gradient-sensitive seismological probes. First, both the amplitudes and travel times of the diffracted P and S phases (Pdiff, Sdiff) were analyzed to constrain the regional-scale vertical gradients of VP and VS. Acceptable models were grid-searched using synthetic waveforms for trial models that employ only one velocity gradient zone in D″. The VS models were searched over the parameter space of the thickness (H) and the gradient. Solutions show negative deviation from Preliminary Reference Earth Model and a trade-off between gradient and H from -0.00088 s-1, for190 km to -0.00049 s-1, for 240 km with a typical error of ±0.00015 s-1. Rather than pinning down the best solution, we consider two sets of solutions for VS with H = 190 and 240 km. For these two H values, the gradients of VP were determined solely by amplitude to be -0.00032 s-1 for 190 km and 0.00015 s-1 for 240 km, shrouded in relatively large errors of 0.0002-0.0003 s-1. We derive the temperature gradient from the resolved velocity gradients using the seismological-thermodynamic equation of Doornbos et al. (1986) and arrive at 9.0 ± 5.8 K/km and 5.7 ± 4.1 K/km over 190 and 240 km, respectively. The difference in gradient between these two models is statistically significant at the 99% confidence level, and the odds that the apparent steeper gradient is caused by squeezing energy of diffracted waves into a thinner zone can also be rejected with high confidence. The combination of the two models is thus consistent with a nonlinear temperature profile that steepens toward the core-mantle boundary. Both models detect the superadiabatic gradient of temperature in the lowermost mantle.

  15. High-pressure-temperature gradient instrument: use for determining the temperature and pressure limits of bacterial growth.

    PubMed Central

    Yayanos, A A; van Boxtel, R; Dietz, A S

    1984-01-01

    A pressurized temperature gradient instrument allowed a synoptic determination of the effects of temperature and pressure on the reproduction of bacteria. The instrument consisted of eight pressure vessels housed parallel to each other in an insulated aluminum block in which a linear temperature gradient was supported. For a given experiment, eight pressures between 1 and 1,100 bars were chosen; the linear temperature gradient was established over an interval within -20 to 100 degrees C. Pure cultures and natural populations were studied in liquid or solid medium either in short (ca. 2-cm) culture tubes or in long (76.2-cm) glass capillaries. In the case of a pure culture, experiments with the pressurized temperature gradient instrument determined values of temperature and pressure that bounded its growth. Feasibility experiments with mixed populations of bacteria from water samples from a shallow depth of the sea showed that the instrument may be useful in identifying the extent to which a natural population is adapted to the temperatures and pressures at the locale of origin of the sample. Additional conceived uses of the instrument included synoptic determinations of cell functions other than reproduction and of biochemical activities. Images PMID:6391378

  16. Temperature-gradient and heat-flow data, Panther Canyon, Nevada

    SciTech Connect

    Fisher, Marci A.; Gardner, Murray C.

    1981-07-01

    A series of six shallow temperature-gradient holes were drilled for Sunoco Energy Development Company in Panther Canyon, Pershing County, Nevada during the period March 24 through June 15, 1981. A proposed intermediate-depth gradient hole was spud but abandoned after encountering unresolvable drilling problems. The locations of these holes are shown on figure 1. This report summarizes the results of the Panther Canyon project.

  17. Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Rind, David

    2000-01-01

    To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the GISS GCM (Goddard Institute for Space Studies General Circulation Model) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

  18. Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Rind, David

    2000-01-01

    To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model (GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

  19. Range-Wide Latitudinal and Elevational Temperature Gradients for the World's Terrestrial Birds: Implications under Global Climate Change

    PubMed Central

    La Sorte, Frank A.; Butchart, Stuart H. M.; Jetz, Walter; Böhning-Gaese, Katrin

    2014-01-01

    Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity

  20. Range-wide latitudinal and elevational temperature gradients for the world's terrestrial birds: implications under global climate change.

    PubMed

    La Sorte, Frank A; Butchart, Stuart H M; Jetz, Walter; Böhning-Gaese, Katrin

    2014-01-01

    Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity

  1. Influence of temperature gradients on leaf water potential.

    PubMed

    Wiebe, H H; Prosser, R J

    1977-02-01

    Water potential was monitored at nine locations along single maize (Zea mays L.) leaf blades with aluminum block in situ thermocouple hygrometers. Water potential showed a continuous decrease toward the tip, with a 2- to 4-bar difference between leaf base and tip under both moist and dry soil conditions. The water potential difference between the soil and the leaf base was about 4 bars. Water potentials decreased during the day and during a drying cycle, and increased at night and after irrigation. Heating a band of a leaf to 40 C or cooling it to 7 C had no influence on the water potential of the affected portion when this was corrected for hygrometer output over standard calibrating solutions at the respective temperatures. Heating or cooling a portion of a leaf had neither short nor long term effects on water potential of more distal leaf portions continuously monitored by hygrometers in dew point readout. Water potential fluctuated with an amplitude of about 1.5 bars and an irregular period of 10 to 30 minutes. Measurements with silver foil in situ psychrometers gave similar results.

  2. Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite

    PubMed Central

    Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

    2014-01-01

    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. PMID:24748375

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

    PubMed

    Chani, Muhammad Tariq Saeed; Karimov, Kh S; Asiri, Abdullah M; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

    2014-01-01

    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.

  4. Liquid crystal thermography. A method for monitoring temperature gradients in microtitration plates.

    PubMed

    Oliver, D G; Sanders, A H; Jang, L; Poy, D; Van Heuvelen, A

    1983-03-11

    Precise quantitative heat transfer information in microtitration plates can be obtained by filling the wells of a microtitration plate with cholesteric liquid crystals and incubating the plates at the desired temperature in different incubators. The liquid crystals indicate temperature by changes in discrete reproducible colors over various temperature ranges. With these instrumented plates, interwell thermal gradients may be documented visually and are in close agreement with results obtained by using wire thermocouple measuring techniques.

  5. Evolution of the Specific Surface Area of Snow in a High Temperature Gradient Metamorphism

    NASA Astrophysics Data System (ADS)

    Wang, X.; Baker, I.

    2014-12-01

    The structural evolution of low-density snow under a high temperature gradient over a short period usually takes place in the surface layers during diurnal recrystallization or on a clear, cold night. To relate snow microstructures with their thermal properties, we combined X-ray computed microtomography (micro-CT) observations with numerical simulations. Different types of snow were tested over a large range of TGs (100 K m-1- 500 K m-1). The Specific Surface Area (SSA) was used to characterize the temperature gradient metamorphism (TGM). The magnitude of the temperature gradient and the initial snow type both influence the evolution of SSA. The SSA evolution under TGM was dominated by grain growth and the formation of complex surfaces. Fresh snow experienced a logarithmic decrease of SSA with time, a feature been observed previously by others [Calonne et al., 2014; Schneebeli and Sokratov, 2004; Taillandier et al., 2007]. However, for initial rounded and connected snow structures, the SSA will increase during TGM. Understanding the SSA increase is important in order to predict the enhanced uptake of chemical species by snow or increase in snow albedo. Calonne, N., F. Flin, C. Geindreau, B. Lesaffre, and S. Rolland du Roscoat (2014), Study of a temperature gradient metamorphism of snow from 3-D images: time evolution of microstructures, physical properties and their associated anisotropy, The Cryosphere Discussions, 8, 1407-1451, doi:10.5194/tcd-8-1407-2014. Schneebeli, M., and S. A. Sokratov (2004), Tomography of temperature gradient metamorphism of snow and associated changes in heat conductivity, Hydrological Processes, 18(18), 3655-3665, doi:10.1002/hyp.5800. Taillandier, A. S., F. Domine, W. R. Simpson, M. Sturm, and T. A. Douglas (2007), Rate of decrease of the specific surface area of dry snow: Isothermal and temperature gradient conditions, Journal of Geophysical Research: Earth Surface (2003-2012), 112(F3), doi: 10.1029/2006JF000514.

  6. Direct reduction of low grade nickel laterite ore to produce ferronickel using isothermal - temperature gradient

    NASA Astrophysics Data System (ADS)

    Zulhan, Zulfiadi; Gibranata, Ian

    2017-01-01

    In this study, low grade nickel laterite ore was processed by means of isothermal-temperature gradient method to produce ferronickel nugget. The ore and coal as reductant were ground to obtain the grain size of less than 0.25 mm and 0.425 mm, respectively. Both ground laterite ore and coal were mixed, agglomerated in the form of cylindrical pellet by using press machine and then reduced at temperature of 1000°C to 1400°C in a muffle furnace. The experiments were conducted at three stages each at different temperature profile: the first stage was isothermal at 1000°C; the second stage was temperature gradient at certain heating rate from 1000 to 1400°C; and the third stage was isothermal at 1400°C. The heating rate during temperature gradient stage was varied: 6.67, 8.33 and 10°C/minute. No fluxes were added in these experiments. By addition of 10 wt% of coal into the laterite nikel ore, product of ferronickel nugget was formed with the size varies from 1-2 mm. However, by increasing the coal content, the size of ferronickel nugget was decreased to less than 0.2 mm. The observation of the samples during the heating stage showed that ferronickel nugget grew and separated from the gangue during temperature gradient stage as it achieved the temperature of 1380°C. Furthermore, the experiment results indicated that the recovery of ferronickel can be increased at lower heating rate during temperature gradient stage and longer holding time for final isothermal stage. The highest nickel recovery was obtained at a heating rate of 6.67°C/minute.

  7. Pore and grain boundary migration under a temperature gradient: A phase-field model study

    DOE PAGES

    Biner, S. B.

    2016-03-16

    In this study, the collective migration behavior of pores and grain boundaries under a temperature gradient is studied for simple single crystal, bi-crystal and polycrystal configurations with a phase-field model formulism. For simulation of the microstructure of solids, composed of pores and grain boundaries, the results indicate that not only the volume fraction of pores, but also its spatial partitioning between the grain boundary junctions and the grain boundary segments appears to be important. In addition to various physical properties, the evolution kinetics, under given temperature gradients, will be strongly influenced with the initial morphology of a poly-crystalline microstructure.

  8. Temperature gradient scale length measurement: A high accuracy application of electron cyclotron emission without calibration

    NASA Astrophysics Data System (ADS)

    Houshmandyar, S.; Yang, Z. J.; Phillips, P. E.; Rowan, W. L.; Hubbard, A. E.; Rice, J. E.; Hughes, J. W.; Wolfe, S. M.

    2016-11-01

    Calibration is a crucial procedure in electron temperature (Te) inference from a typical electron cyclotron emission (ECE) diagnostic on tokamaks. Although the calibration provides an important multiplying factor for an individual ECE channel, the parameter ΔTe/Te is independent of any calibration. Since an ECE channel measures the cyclotron emission for a particular flux surface, a non-perturbing change in toroidal magnetic field changes the view of that channel. Hence the calibration-free parameter is a measure of Te gradient. BT-jog technique is presented here which employs the parameter and the raw ECE signals for direct measurement of electron temperature gradient scale length.

  9. On the effect of temperature gradients and coating translucence on the accuracy of phosphor thermometry

    NASA Astrophysics Data System (ADS)

    Pilgrim, C. C.; Feist, J. P.; Heyes, A. L.

    2013-10-01

    Accurate knowledge of the operating temperature of thermal barrier coatings (TBCs) is not currently available, therefore significant safety margins are employed during operation of gas turbines, which limit the engine efficiency. Recently, phosphorescent sensor TBCs have been used to detect coating temperatures with a reported accuracy under isothermal conditions up to 4 K. However, the thermal gradient through a TBC in modern gas turbines is of the order of 1 K µm-1­. The interpretation of the temperature provided by a sensor coating therefore requires a better understanding of the through thickness response of the material. Kubelka-Munk theory has been adapted to describe the light propagation and generation through the thickness of a sensor coating. The model indicates that the temperature measurement can be considered to come from a depth of 17 µm below the surface, depending on the coating type, thermal gradient and coating thickness. As such, the coating can be designed to suit the application, and the temperature variation due to the thermal gradient and coating thickness can be limited to 1%. Where coating design is restricted by its application, the sensor material can be embedded within the coating to avoid measurement errors due to thermal gradients, provided the sensor layer is sufficiently thin. This, however, causes a significant reduction in emission intensity, hence reducing the signal-to-noise ratio, and necessitating a compromise between signal amplitude and measurement accuracy.

  10. Evaporation condensation-induced bubble motion after temperature gradient set-up

    NASA Astrophysics Data System (ADS)

    Nikolayev, Vadim S.; Garrabos, Yves; Lecoutre, Carole; Pichavant, Guillaume; Chatain, Denis; Beysens, Daniel

    2017-01-01

    Thermocapillary (Marangoni) motion of a gas bubble (or a liquid drop) under a temperature gradient can hardly be present in a one-component fluid. Indeed, in such a pure system, the vapor-liquid interface is always isothermal (at saturation temperature). However, evaporation on the hot side and condensation on the cold side can occur and displace the bubble. We have observed such a phenomenon in two different fluids submitted to a temperature gradient under reduced gravity: hydrogen under magnetic compensation of gravity in the HYLDE facility at CEA-Grenoble and water in the DECLIC facility onboard the ISS. The experiments and the subsequent analysis are performed in the vicinity of the vapor-liquid critical point to benefit from critical universality. In order to better understand the phenomena, a 1D numerical simulation has been performed. After the temperature gradient is imposed, two regimes can be evidenced. At early times, the temperatures in the bubble and the surrounding liquid become different thanks to their different compressibility and the "piston effect" mechanism, i.e. the fast adiabatic bulk thermalization induced by the expansion of the thermal boundary layers. The difference in local temperature gradients at the vapor-liquid interface results in an unbalanced evaporation/condensation phenomenon that makes the shape of the bubble vary and provoke its motion. At long times, a steady temperature gradient progressively forms in the liquid (but not in the bubble) and induces steady bubble motion towards the hot end. We evaluate the bubble velocity and compare with existing theories.

  11. Evolving ecological networks and the emergence of biodiversity patterns across temperature gradients.

    PubMed

    Stegen, James C; Ferriere, Regis; Enquist, Brian J

    2012-03-22

    In ectothermic organisms, it is hypothesized that metabolic rates mediate influences of temperature on the ecological and evolutionary processes governing biodiversity. However, it is unclear how and to what extent the influence of temperature on metabolism scales up to shape large-scale diversity patterns. In order to clarify the roles of temperature and metabolism, new theory is needed. Here, we establish such theory and model eco-evolutionary dynamics of trophic networks along a broad temperature gradient. In the model temperature can influence, via metabolism, resource supply, consumers' vital rates and mutation rate. Mutation causes heritable variation in consumer body size, which diversifies and governs consumer function in the ecological network. The model predicts diversity to increase with temperature if resource supply is temperature-dependent, whereas temperature-dependent consumer vital rates cause diversity to decrease with increasing temperature. When combining both thermal dependencies, a unimodal temperature-diversity pattern evolves, which is reinforced by temperature-dependent mutation rate. Studying coexistence criteria for two consumers showed that these outcomes are owing to temperature effects on mutual invasibility and facilitation. Our theory shows how and why metabolism can influence diversity, generates predictions useful for understanding biodiversity gradients and represents an extendable framework that could include factors such as colonization history and niche conservatism.

  12. PHYSIOLOGICAL RESPONSES OF ECKLONIA RADIATA (LAMINARIALES) TO A LATITUDINAL GRADIENT IN OCEAN TEMPERATURE(1).

    PubMed

    Staehr, Peter A; Wernberg, Thomas

    2009-02-01

    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 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 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 temperatures (10% higher Q10 -values) than photosynthesis and had a higher optimum temperature, irrespective of sampling location. To maintain a positive carbon balance, E. radiata increased the critical light demand (Ec ) exponentially with increasing experimental temperature. The temperature dependency of Ec was, however, weakened with increasing ocean temperature, such that the critical light demand was relaxed in kelp acclimated to higher ocean temperatures. Nevertheless, calculations of critical depth limits suggested that direct effects of future temperature increases are unlikely to be as strong as effects of reduced water clarity, another globally increasing problem in coastal areas.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  15. Low-power concentration and separation using temperature gradient focusing via Joule heating.

    PubMed

    Kim, Sun Min; Sommer, Greg J; Burns, Mark A; Hasselbrink, Ernest F

    2006-12-01

    We present an experimental study of temperature gradient focusing (TGF) exploiting an inherent Joule heating phenomenon. A simple variable-width PDMS device delivers rapid and repeatable focusing of model analytes using significantly lower power than conventional TGF techniques. High electric potential applied to the device induces a temperature gradient within the microchannel due to the channel's variable width, and the temperature-dependent mobility of the analytes causes focusing at a specific location. The PDMS device also shows simultaneous separation and concentration capability of a mixture of two sample analytes in less than 10 min. An experiment combining Joule heating with external heating/cooling further supports the hypothesis that temperature is indeed the dominant factor in achieving focusing with this technique.

  16. Homochirality beyond grinding: deracemizing chiral crystals by temperature gradient under boiling.

    PubMed

    Viedma, Cristóbal; Cintas, Pedro

    2011-12-28

    A single-chirality solid phase can be obtained in boiling solutions containing a racemic mixture of left- and right-handed enantiomorphous crystals due to dissolution-crystallization cycles induced by a temperature gradient. This phenomenon provides further insights into asymmetric amplification mechanisms under presumably prebiotic conditions.

  17. Poloidal flow driven by ion-temperature-gradient turbulence in tokamaks

    SciTech Connect

    Rosenbluth, M.N.; Hinton, F.L.

    1998-01-01

    We show that linear collisionless processes do not damp poloidal flows driven by ion-temperature-gradient (ITG) turbulence. Since these flows play an important role in saturating the level of the turbulence, this level, as well as the transport caused by ITG modes, may be overestimated by gyrofluid simulations, which employ linear collisionless rotation damping. {copyright} {ital 1998} {ital The American Physical Society}

  18. Experimental and numerical determination of temperature gradients for a single tube alkali metal thermal-to-electric converter cell

    NASA Technical Reports Server (NTRS)

    Wright, S.

    2001-01-01

    This paper presents the results from the experimental and numerical determination of shell temperature gradients for a single tube AMTEC cell evaluated under simulated deep space operating conditions.

  19. Controlled simulation of optical turbulence in a temperature gradient air chamber

    NASA Astrophysics Data System (ADS)

    Toselli, Italo; Wang, Fei; Korotkova, Olga

    2016-05-01

    Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation with controlled strength of the refractive-index fluctuations. The temperature gradients are generated by a sequence of heat guns with controlled individual strengths. The temperature structure functions are measured in two directions transverse to propagation path with the help of a thermocouple array and used for evaluation of the corresponding refractive-index structure functions of optical turbulence.

  20. Pioneer 10 observation of the solar wind proton temperature heliocentric gradient

    NASA Technical Reports Server (NTRS)

    Mihalov, J. D.; Wolfe, J. H.

    1978-01-01

    Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer 10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares fit of average temperature to heliocentric radial distance, R, yields the power law R sup -.52. These average proton temperatures are not correlated as well with Pioneer 10's heliocentric radial distance (-.85) as are the corresponding average Zurich sunspot numbers R sub z (-.95). Consequently, it is difficult to isolate the spatial gradient in the Pioneer 10 solar wind proton temperatures using that data alone.

  1. The impact of summer rainfall on the temperature gradient along the United States-Mexico border

    NASA Technical Reports Server (NTRS)

    Balling, Robert C., Jr.

    1989-01-01

    The international border running through the Sonoran Desert in southern Arizona and northern Sonora is marked by a sharp discontinuity in albedo and grass cover. The observed differences in surface properties are a result of long-term, severe overgrazing of the Mexican lands. Recently, investigators have shown the Mexican side of the border to have higher surface and air temperatures when compared to adjacent areas in the United State. The differences in temperatures appear to be more associated with differential evapotranspiration rates than with albedo changes along the border. In this study, the impact of summer rainfall on the observed seasonal and daily gradient in maximum temperature is examined. On a seasonal time scale, the temperature gradient increases with higher moisture levels, probably due to a vegetative response on the United States' side of the border; at the daily level, the gradient in maximum temperature decreases after a rain event as evaporation rates equalize between the countries. The results suggest that temperature differences between vegetated and overgrazed landscapes in arid areas are highly dependent upon the amount of moisture available for evapotranspiration.

  2. Far-from-equilibrium growth of thin films in a temperature gradient.

    PubMed

    Candia, Julián; Albano, Ezequiel V

    2011-11-01

    The irreversible growth of thin films under far-from-equilibrium conditions is studied in (2+1)-dimensional strip geometries. Across one of the transverse directions, a temperature gradient is applied by thermal baths at fixed temperatures between T(1) and T(2), where T(1)temperature of the system in contact with an homogeneous thermal bath. By using standard finite-size scaling methods, we characterized a continuous order-disorder phase transition driven by the thermal bath gradient with critical temperature T(c)=0.84(2) and critical exponents ν=1.53(6), γ=2.54(11), and β=0.26(8), which belong to a different universality class from that of films grown in an homogeneous bath. Furthermore, the effects of the temperature gradient are analyzed by means of a bond model that captures the growth dynamics. The interplay of geometry and thermal bath asymmetries leads to growth bond flux asymmetries and the onset of transverse ordering effects that explain qualitatively the shift in the critical temperature.

  3. Theory of the jitter radiation in a magnetized plasma accompanying a temperature gradient

    NASA Astrophysics Data System (ADS)

    Hattori, Makoto; Fujiki, Kazushiro

    2016-04-01

    The linear stability of a magnetized plasma accompanying a temperature gradient is reexamined by using plasma kinetic theory. We propose that the anisotropic velocity distribution function should be decomposed into two components. One is proportional to the temperature gradient parallel to the background magnetic field. The other is proportional to the temperature gradient perpendicular to the background magnetic field. Since the amplitude of the anisotropic velocity distribution function is proportional to the heat conductivity, and the heat conductivity perpendicular to the magnetic field is strongly reduced, the first component of the anisotropic velocity distribution function is predominant. The anisotropic velocity distribution function induced by the temperature gradient along the background magnetic field drives plasma kinetic instability and circular polarized magnetic plasma waves are excited. We show that the instability is almost identical to the Weibel instability in the weakly magnetized plasma. However, in the case of the instability caused by the temperature gradient, whether wave vectors of modes are parallel to or antiparallel to the background magnetic field, the growth rate of one mode is suppressed and the growth rate of the other mode is enhanced due to the background magnetic field. In the strongly magnetized plasma, one mode is stabilized and only one of the modes remains unstable. The formulae for the jitter radiation spectrum emitted by relativistic electrons when they travel through the magnetized plasma with the plasma waves driven by the instability are deduced at the first time. We show that the synchrotron emission and the jitter radiation are simultaneously emitted from the same relativistic electron. The jitter radiation is expected to be circularly polarized but with a very small polarization degree since almost the same amounts of left-handed and right-handed circular polarized magnetic waves are excited by the instability.

  4. Spectroscopic analysis of the density and temperature gradients in the laser-heated gas jet

    SciTech Connect

    Matthews, D.L.; Lee, R.W.; Auerbach, J.M.

    1981-01-01

    We have performed an analysis of the x-ray spectra produced by a 1.0TW, lambda/sub L/-0.53..mu..m laser-irradiated gas jet. Plasmas produced by ionization of neon, argon and N/sub 2/ + SF/sub 6/ gases were included in those measurements. Plasma electron density and temperature gradients were obtained by comparison of measured spectra with those produced by computer modeling. Density gradients were also obtained using laser interferometry. The limitations of this technique for plasma diagnosis will be discussed.

  5. Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model

    NASA Astrophysics Data System (ADS)

    Yamagishi, Osamu; Sugama, Hideo

    2016-03-01

    Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.

  6. NMR and pulsed field gradient NMR approach of water sorption properties in Nafion at low temperature.

    PubMed

    Guillermo, Armel; Gebel, Gérard; Mendil-Jakani, Hakima; Pinton, Eric

    2009-05-14

    The water uptake and the water self-diffusion coefficient were measured in Nafion membranes at subzero temperatures. NMR spectroscopy was used to precisely quantify the actual concentration of water in membranes as a function of the temperature and their hydration rates at room temperature. We find that below 273 K the water concentration decreases with temperature to reach, at around 220 K, a limit value independent of the initial concentration. This regime is observed if the concentration at room temperature is higher than 10%. Below this concentration no membrane deswelling was observed. The water self-diffusion coefficient, measured by pulsed field gradient NMR in function of the temperature, is determined by the actual concentration C(T) whatever the concentration at room temperature. The concentration variation is attributed to a decrease in the relative humidity RH(T) of the water vapor surrounding the membrane induced by the simultaneous presence of supercooled water inside the membrane and ice outside the membrane.

  7. Ultraviolet irradiation and gradient temperature assisted autolysis for protein recovery from shrimp head waste.

    PubMed

    Cao, Wenhong; Tan, Caiyun; Zhan, Xiaojian; Li, Huiyi; Zhang, Chaohua

    2014-12-01

    A novel autolysis method using ultraviolet (UV) irradiation and gradient temperature was investigated to efficiently recover proteins from the head of the shrimp Penaeus vannamei. The proteolytic activity of shrimp head subjected to 30W UV irradiation for 20 min was increased by 62%, compared with that of untreated samples. After irradiation, the enzymes remained active across a wide range of temperatures (45-60°C) and pH (7-10). An orthogonal design was used to optimize autolysis condition. After 5h autolysis, protein recovery from the UV-heat treated samples was up to 92.1%. These results indicate the potential of using UV irradiation in combination with gradient temperatures to improve recovery of proteins from shrimp head waste.

  8. Influence of temperature gradient on diffracted X-ray spectrum in quartz crystal

    NASA Astrophysics Data System (ADS)

    Mkrtchyan, A. R.; Potylitsyn, A. P.; Vukolov, A. V.; Novokshonov, A. I.; Gogolev, A. S.; Amiragyan, R. V.; Movsisyan, A. E.

    2016-06-01

    In this work characteristics of hard X-ray (with energy higher than 30 keV) were investigated. In the experiment we measured spectra of X-ray reflected by a quartz monocrystal in Laue geometry under influence of the temperature gradient. The measurements were made by the spectrometer BDER-KI-11K with 300 eV resolution on the 17.74 keV spectral line of Am241 and the spectrometer XR-100CR with 270 eV resolution on the same spectral line. An existence of temperature gradient leads to increasing of the diffracted beam intensity. The intensity was measured dependently on the temperature of one of the edge of the crystal.

  9. Evaluation of Temperature Gradient in Advanced Automated Directional Solidification Furnace (AADSF) by Numerical Simulation

    NASA Technical Reports Server (NTRS)

    Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

    1996-01-01

    A numerical model of heat transfer using combined conduction, radiation and convection in AADSF was used to evaluate temperature gradients in the vicinity of the crystal/melt interface for variety of hot and cold zone set point temperatures specifically for the growth of mercury cadmium telluride (MCT). Reverse usage of hot and cold zones was simulated to aid the choice of proper orientation of crystal/melt interface regarding residual acceleration vector without actual change of furnace location on board the orbiter. It appears that an additional booster heater will be extremely helpful to ensure desired temperature gradient when hot and cold zones are reversed. Further efforts are required to investigate advantages/disadvantages of symmetrical furnace design (i.e. with similar length of hot and cold zones).

  10. The Temperature Gradient and Transition Timescales as a Function of Topography in Complex Terrain

    NASA Astrophysics Data System (ADS)

    Higgins, C. W.; Hoch, S. W.; Pardyjak, E.

    2013-12-01

    Large portions of the Earth's surface are covered by mountainous areas, and understanding atmospheric flow over these regions is critical for weather prediction, (micro)climatological research, and dispersion modeling. Complex interactions between the topographic features, the synoptic forcing and the buoyant forcing drive flow patterns and flow regime transitions. As a part of the MATTERHORN field experiment, Distributed Temperature Sensing (DTS) technology was used to measure the vertical temperature gradient on an east facing slope across a 2km transect of granite ridge in the Utah west desert, from the base of the mountain to the middle slope. Thus, the temperature gradient is sampled above a wide range of topographic features, from valley formations to ridges, and over a wide range of slope and aspect angles. The relationship between these landforms and the timescales of morning and evening transitions is explored and presented.

  11. Melting analysis on microbeads in rapid temperature-gradient inside microchannels for single nucleotide polymorphisms detectiona)

    PubMed Central

    Li, Kan-Chien; Ding, Shih-Torng; Lin, En-Chung; Wang, Lon (Alex); Lu, Yen-Wen

    2014-01-01

    A continuous-flow microchip with a temperature gradient in microchannels was utilized to demonstrate spatial melting analysis on microbeads for clinical Single Nucleotide Polymorphisms (SNPs) genotyping on animal genomic DNA. The chip had embedded heaters and thermometers, which created a rapid and yet stable temperature gradient between 60 °C and 85 °C in a short distance as the detection region. The microbeads, which served as mobile supports carrying the target DNA and fluorescent dye, were transported across the temperature gradient. As the surrounding temperature increased, the fluorescence signals of the microbeads decayed with this relationship being acquired as the melting curve. Fast DNA denaturation, as a result of the improved heat transfer and thermal stability due to scaling, was also confirmed. Further, each individual microbead could potentially bear different sequences and pass through the detection region, one by one, for a series of melting analysis, with multiplex, high-throughput capability being possible. A prototype was tested with target DNA samples in different genotypes (i.e., wild and mutant types) with a SNP location from Landrace sows. The melting temperatures were obtained and compared to the ones using a traditional tube-based approach. The results showed similar levels of SNP discrimination, validating our proposed technique for scanning homozygotes and heterozygotes to distinguish single base changes for disease research, drug development, medical diagnostics, agriculture, and animal production. PMID:25553186

  12. Melting analysis on microbeads in rapid temperature-gradient inside microchannels for single nucleotide polymorphisms detection.

    PubMed

    Li, Kan-Chien; Ding, Shih-Torng; Lin, En-Chung; Wang, Lon Alex; Lu, Yen-Wen

    2014-11-01

    A continuous-flow microchip with a temperature gradient in microchannels was utilized to demonstrate spatial melting analysis on microbeads for clinical Single Nucleotide Polymorphisms (SNPs) genotyping on animal genomic DNA. The chip had embedded heaters and thermometers, which created a rapid and yet stable temperature gradient between 60 °C and 85 °C in a short distance as the detection region. The microbeads, which served as mobile supports carrying the target DNA and fluorescent dye, were transported across the temperature gradient. As the surrounding temperature increased, the fluorescence signals of the microbeads decayed with this relationship being acquired as the melting curve. Fast DNA denaturation, as a result of the improved heat transfer and thermal stability due to scaling, was also confirmed. Further, each individual microbead could potentially bear different sequences and pass through the detection region, one by one, for a series of melting analysis, with multiplex, high-throughput capability being possible. A prototype was tested with target DNA samples in different genotypes (i.e., wild and mutant types) with a SNP location from Landrace sows. The melting temperatures were obtained and compared to the ones using a traditional tube-based approach. The results showed similar levels of SNP discrimination, validating our proposed technique for scanning homozygotes and heterozygotes to distinguish single base changes for disease research, drug development, medical diagnostics, agriculture, and animal production.

  13. Thermal Design to Meet Stringent Temperature Gradient/Stability Requirements of SWIFT BAT Detectors

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2000-01-01

    The Burst Alert Telescope (BAT) is an instrument on the National Aeronautics and Space Administration (NASA) SWIFT spacecraft. It is designed to detect gamma ray burst over a broad region of the sky and quickly align the telescopes on the spacecraft to the gamma ray source. The thermal requirements for the BAT detector arrays are very stringent. The maximum allowable temperature gradient of the 256 cadmium zinc telluride (CZT) detectors is PC. Also, the maximum allowable rate of temperature change of the ASICs of the 256 Detector Modules (DMs) is PC on any time scale. The total power dissipation of the DMs and Block Command & Data Handling (BCDH) is 180 W. This paper presents a thermal design that uses constant conductance heat pipes (CCHPs) to minimize the temperature gradient of the DMs, and loop heat pipes (LHPs) to transport the waste heat to the radiator. The LHPs vary the effective thermal conductance from the DMs to the radiator to minimize heater power to meet the heater power budget, and to improve the temperature stability. The DMs are cold biased, and active heater control is used to meet the temperature gradient and stability requirements.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

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

    2015-10-23

    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.

  16. Precise measurements of radial temperature gradients in the laser-heated diamond anvil cell.

    PubMed

    Kavner, A; Nugent, C

    2008-02-01

    A new spectroradiometry system specialized for measuring two-dimensional temperature gradients for samples at high pressure in the laser heated diamond anvil cell has been designed and constructed at UCLA. Emitted light intensity from sample hotspots is imaged by a videocamera for real time monitoring, an imaging spectroradiometer for temperature measurement, and a high-dynamic-range camera that examines a magnified image of the two-dimensional intensity distribution of the heated spot, yielding precise measurements of temperature gradients. With this new system, most systematic errors in temperature measurement due to chromatic aberration are bypassed. We use this system to compare several different geometries of temperature measurement found in the literature, including scanning a pinhole aperture, and narrow-slit and wide-slit entrance apertures placed before the imaging spectrometer. We find that the most accurate way of measuring a temperature is to use the spectrometer to measure an average hotspot temperature and to use information from the imaging charge coupled device to calculate the temperature distribution to the hotspot. We investigate the effects of possible wavelength- and temperature-dependent emissivity, and evaluate their errors. We apply this technique to measure the anisotropy in temperature distribution of highly oriented graphite at room temperature and also at high pressures. A comparison between model and experiment demonstrates that this system is capable of measuring thermal diffusivity in anisotropic single crystals and is also capable of measuring relative thermal diffusivity at high pressures and temperatures among different materials. This shows the possibility of using this system to provide information about thermal diffusivity of materials at high pressure and temperature.

  17. Experimental characterization of the Taylor-Couette flow submitted to a radial temperature gradient

    NASA Astrophysics Data System (ADS)

    Prigent, Arnaud; Guillerm, Rapha"El; Mutabazi, Innocent; Yang, Kyung-Soo

    2009-11-01

    We have developed a non-intrusive velocity and temperature fields measurement technique using thermochromic liquid crystals which allows to fully characterize the flow produced in a narrow gap and large aspect ratio Couette-Taylor system submitted to a radial temperature gradient. The aspect ratio and radius ratio of the system are respectively equal to 112 and 0.8. The control parameters are the Grashof number Gr, related to the radial temperature gradient, and the Taylor number Ta, related to the rotation of the inner cylinder. Here, Gr is fixed and Ta is gradually increased. For small values of Ta, the base flow is composed of the circular Couette flow and a vertical flow induced by the radial temperature gradient. Above a critical value of Ta, the destabilization of the base flow gives rise to a spiral pattern. While for small Gr values it corresponds to traveling inclined vortices, for large Gr values it corresponds to a modulated wave-like pattern filling the whole length of the system and rotating at the mean angular velocity of the flow. When Ta is further increased, this wave-like pattern is progressively replaced by a counter-rotating vortices pattern. Numerical simulations of the corresponding Boussinesq-Oberbeck equations provide results in good agreement with experiments.

  18. Gradient CdSe/CdS Quantum Dots with Room Temperature Biexciton Unity Quantum Yield.

    PubMed

    Nasilowski, Michel; Spinicelli, Piernicola; Patriarche, Gilles; Dubertret, Benoît

    2015-06-10

    Auger recombination is a major limitation for the fluorescent emission of quantum dots (QDs). It is the main source of QDs fluorescence blinking at the single-particle level. At high-power excitation, when several charge carriers are formed inside a QD, Auger becomes more efficient and severely decreases the quantum yield (QY) of multiexcitons. This limits the efficiency and the use of colloidal QDs in applications where intense light output is required. Here, we present a new generation of thick-shell CdSe/CdS QDs with dimensions >40 nm and a composition gradient between the core and the shell that exhibits 100% QY for the emission of both the monoexciton and the biexciton in air and at room temperature for all the QDs we have observed. The fluorescence emission of these QDs is perfectly Poissonian at the single-particle level at different excitation levels and temperatures, from 30 to 300 K. In these QDs, the emission of high-order (>2) multiexcitons is quite efficient, and we observe white light emission at the single-QD level when high excitation power is used. These gradient thick shell QDs confirm the suppression of Auger recombination in gradient core/shell structures and help further establish the colloidal QDs with a gradient shell as a very stable source of light even under high excitation.

  19. What causes cooling water temperature gradients in a forested stream reach?

    NASA Astrophysics Data System (ADS)

    Garner, G.; Malcolm, I. A.; Sadler, J. P.; Hannah, D. M.

    2014-12-01

    Previous studies have suggested that shading by riparian vegetation may reduce maximum water temperatures and provide refugia for temperature-sensitive aquatic organisms. Longitudinal cooling gradients have been observed during the daytime for stream reaches shaded by coniferous trees downstream of clear cuts or deciduous woodland downstream of open moorland. However, little is known about the energy exchange processes that drive such gradients, especially in semi-natural woodland contexts without confounding cool groundwater inflows. To address this gap, this study quantified and modelled variability in stream temperature and heat fluxes along an upland reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) where riparian land use transitions from open moorland to semi-natural, predominantly deciduous woodland. Observations were made along a 1050 m reach using a spatially distributed network of 10 water temperature data loggers, 3 automatic weather stations and 211 hemispherical photographs that were used to estimate incoming solar radiation. These data parameterised a high-resolution energy flux model incorporating flow routing, which predicted spatio-temporal variability in stream temperature. Variability in stream temperature was controlled largely by energy fluxes at the water-column-atmosphere interface. Net energy gains occurred along the reach, predominantly during daylight hours, and heat exchange across the bed-water-column interface accounted for <1% of the net energy budget. For periods when daytime net radiation gains were high (under clear skies), differences between water temperature observations increased in the streamwise direction; a maximum instantaneous difference of 2.5 °C was observed between the upstream reach boundary and 1050 m downstream. Furthermore, daily maximum water temperature at 1050 m downstream was ≤1 °C cooler than at the upstream reach boundary and lagged by >1 h. Temperature gradients were not generated

  20. Variation of the temperature gradient in the solar photosphere with magnetic activity

    NASA Astrophysics Data System (ADS)

    Faurobert, M.; Balasubramanian, R.; Ricort, G.

    2016-10-01

    Context. The contribution of quiet-Sun regions to the solar irradiance variability is currently unclear. Some solar-cycle variations of the quiet-Sun physical structure, such as the temperature gradient or the photospheric radius, might affect the irradiance. Aims: We intend to investigate possible variations of the photospheric temperature gradient with magnetic activity. Methods: We used high-resolution center-to-limb observations of the FeI 630.15 nm line profile in the quiet Sun performed onboard the Hinode satellite on 2007, December 19, and on 2013, December 7, that is, close to a minimum and a maximum of magnetic activity, respectively. We analyzed samples of 10″ × 10″ internetwork regions. The wings of the FeI 630.15 nm line were used in a non-standard way to recover images at roughly constant continuum optical depths above the continuum formation level. The image formation height is derived from measuring its perspective shift with respect to the continuum image, both observed away from disk center. The measurement relies on a cross-spectral method that is not limited by the spatial resolution of the SOT telescope and does not rely on any radiative transfer computation. The radiation temperature measured in the images is related to the photospheric temperature at their respective formation height. Results: The method allows us to investigate the temperature gradient in the low photosphere at altitudes of between 0 and 60 km above the 500 nm continuum formation height. In this layer the internetwork temperature gradient appears steeper in our 2013 sample than in the sample of 2007 in the northern hemisphere, whereas we detect no significant change in the southern hemisphere. We argue that this might be related to some strong hemispheric asymmetry of the magnetic activity at the solar maximum of cycle 24. Conclusions: Structural changes have been observed in numerical simulations of the magneto-convection at the surface of the Sun where the increase of

  1. Gyrokinetic simulations of an electron temperature gradient turbulence driven current in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Yi, Sumin; Jhang, Hogun; Kwon, J. M.

    2016-10-01

    We report the results of a gyrokinetic simulation study elucidating the characteristics of the current driven by electron temperature gradient (ETG) turbulence in toroidal geometry. We examined the amount of the ETG turbulence-driven current for different turbulence levels, which were obtained by varying the relative electron gyroradius ρ* = ρe/a. Simulations show that the amount of the ETG turbulence-driven current increases with ρ* due to the gyro-Bohm scaling of turbulence intensity. A perturbation of the equilibrium q-profile by the ETG turbulence-driven current becomes noticeable when ρ* > 1/4000. Even in a small ρ* case, the proportional relation between the ETG turbulence-driven current and turbulence intensity suggests that a considerable intrinsic current can be driven inside an edge pedestal where a steep gradient of the electron temperature profile can excite ETG turbulence in a narrow region.

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

    PubMed

    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.

  3. Nonlinear diffusion-wave equation for a gas in a regenerator subject to temperature gradient

    NASA Astrophysics Data System (ADS)

    Sugimoto, N.

    2015-10-01

    This paper derives an approximate equation for propagation of nonlinear thermoacoustic waves in a gas-filled, circular pore subject to temperature gradient. The pore radius is assumed to be much smaller than a thickness of thermoviscous diffusion layer, and the narrow-tube approximation is used in the sense that a typical axial length associated with temperature gradient is much longer than the radius. Introducing three small parameters, one being the ratio of the pore radius to the thickness of thermoviscous diffusion layer, another the ratio of a typical speed of thermoacoustic waves to an adiabatic sound speed and the other the ratio of a typical magnitude of pressure disturbance to a uniform pressure in a quiescent state, a system of fluid dynamical equations for an ideal gas is reduced asymptotically to a nonlinear diffusion-wave equation by using boundary conditions on a pore wall. Discussion on a temporal mean of an excess pressure due to periodic oscillations is included.

  4. The numerical simulation of Taylor-Couette flow with radial temperature gradient

    NASA Astrophysics Data System (ADS)

    Tuliszka-Sznitko, E.; Kiełczewski, K.

    2016-10-01

    The Taylor-Couette flow with radial temperature gradient is a canonical problem for the study of heat transfer in engineering issues. However, gaining insight into the transitional Taylor-Couette flow with temperature gradient still requires detailed experimental and numerical investigations. In the present paper we have performed computations for the cavity of aspect ratio Γ= 3.76 and radii ratios η= 0.82 and 0.375 with the heated rotating bottom disk and stationary outer cylinder. We analyse the influence of the end-wall boundary conditions and the thermal conditions on the flow structure, and on the distributions of the Nusselt number and torque along the inner and outer cylinders. The averaged values along the inner cylinder of the Nusselt number and torque obtained for different Re are analysed in the light of the results published in [2, 16, 17].

  5. The effect of small temperature gradients on flow in a continuous flow electrophoresis chamber

    NASA Technical Reports Server (NTRS)

    Rhodes, P. H.; Snyder, R. S.

    1982-01-01

    Continuous flow electrophoresis employs an electric field to separate biological cells suspended in a flowing liquid buffer solution. Good separations based on differences in electrophoretic mobility are obtained only when a unidirectional flow is maintained. The desired flow has a parabolic structure in the narrow dimension of the chamber and is uniform acros the width, except near the edges where the no-slip condition prevails. However, because of buoyancy, very small laterall or axial temperature gradients deform the flow significantly. The results of experiments conducted with a specially instrumented chamber show the origin and structure of the buoyancy-driven perturbations. It is found that very small temperature gradients can disturb the flow significantly, as was predicted by earlier theoretical work.

  6. Bubble behavior in molten glass in a temperature gradient. [in reduced gravity rocket experiment

    NASA Technical Reports Server (NTRS)

    Meyyappan, M.; Subramanian, R. S.; Wilcox, W. R.; Smith, H.

    1982-01-01

    Gas bubble motion in a temperature gradient was observed in a sodium borate melt in a reduced gravity rocket experiment under the NASA SPAR program. Large bubbles tended to move faster than smaller ones, as predicted by theory. When the bubbles contacted a heated platinum strip, motion virtually ceased because the melt only imperfectly wets platinum. In some cases bubble diameter increased noticeably with time.

  7. Growth of lithium triborate single crystals from molten salt solution under various temperature gradients

    NASA Astrophysics Data System (ADS)

    Guretskii, S. A.; Ges, A. P.; Zhigunov, D. I.; Ignatenko, A. A.; Kalanda, N. A.; Kurnevich, L. A.; Luginets, A. M.; Milovanov, A. S.; Molchan, P. V.

    1995-12-01

    Single crystals of lithium triborate LiB 3O 5 (LBO) have been grown by the top-seeded solution growth method with B 2O 3 as a solvent using different temperature gradients in the zone of crystallization. Optical and nonlinear optical properties of LBO single crystals have been investigated. The influence of post-growth thermal treatment in oxygen atmosphere on the optical properties has been studied.

  8. Investigating the Thermophysical Properties of the Ice-Snow Interface Under a Controlled Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Hammonds, Kevin; Lieb-Lappen, Ross; Baker, Ian; Wang, Xuan; Courville, Zoe

    2015-04-01

    Of critical importance for avalanche forecasting, is the ability to draw meaningful conclusions from a handful of field observations. To this end, it is common for avalanche forecasters to not only have to rely on these sparse data, but also to use their own intuitive understanding of how these observations are correlated with the complex physical processes that produce mechanical instabilities within a snowpack. One such example of this is the long-held notion that kinetic snow metamorphism does not occur at bulk temperature gradients of less than -10°C/m. Although this may be true for the homogeneous case, it has become a point of contention as to whether or not this guideline should be applied to the more representative case of a heavily stratified and anisotropic snowpack. As an idealized case for our initial laboratory investigations, we have studied how an artificially created ice layer or "lens" would affect the thermophysical state of the snow layers adjacent to the ice lens and the ice lens itself, while being held under a controlled temperature gradient. Our findings have shown, via in-situ micro-thermocouple measurements, that a super-temperature gradient many times greater than the imposed bulk temperature gradient can exist within a millimeter above and below the surface of the ice lens. Furthermore, microstructural analysis via time-lapse X-ray Micro-Computed Tomography and environmental SEM imaging has been performed. Results from this analysis show new ice crystal growth and kinetic snow metamorphism occurring simultaneously on or near the ice lens itself with the connectivity density at the ice-snow interface increasing markedly more below the ice lens than above.

  9. Effect of entropy on anomalous transport in electron-temperature-gradient-modes

    SciTech Connect

    Yaqub Khan, M.; Iqbal, J.; Ul Haq, A.

    2014-05-15

    Due to the interconnection of entropy with temperature and density of plasma, it would be interesting to investigate plasma related phenomena with respect to entropy. By employing Braginskii transport equations, it is proved that entropy is proportional to a function of potential and distribution function of entropy is re-defined, ∇S–drift in obtained. New dispersion relation is derived; it is found that the anomalous transport depends on the gradient of the entropy.

  10. Heat source reconstruction from noisy temperature fields using a gradient anisotropic diffusion filter

    NASA Astrophysics Data System (ADS)

    Beitone, C.; Balandraud, X.; Delpueyo, D.; Grédiac, M.

    2017-01-01

    This paper presents a post-processing technique for noisy temperature maps based on a gradient anisotropic diffusion (GAD) filter in the context of heat source reconstruction. The aim is to reconstruct heat source maps from temperature maps measured using infrared (IR) thermography. Synthetic temperature fields corrupted by added noise are first considered. The GAD filter, which relies on a diffusion process, is optimized to retrieve as well as possible a heat source concentration in a two-dimensional plate. The influence of the dimensions and the intensity of the heat source concentration are discussed. The results obtained are also compared with two other types of filters: averaging filter and Gaussian derivative filter. The second part of this study presents an application for experimental temperature maps measured with an IR camera. The results demonstrate the relevancy of the GAD filter in extracting heat sources from noisy temperature fields.

  11. Measurement of temperature gradient in a heated liquid cylinder using rainbow refractometry assisted with infrared thermometry

    NASA Astrophysics Data System (ADS)

    Song, Feihu; Xu, Chuanlong; Wang, Shimin; Li, Zhenfeng

    2016-12-01

    In a heated liquid cylinder, a temperature gradient exists between the hotter surface and the colder core. Measurement of the temperature gradient is very important for the in-depth investigation into the mechanism and optimized control of the heat transfer process. Rainbow refractometry has been attempted to achieve the measurement since several years ago. Yet there is no effective inversion algorithm without predicting refractive index profiles based on experience. In the paper, an improved rainbow refractometry assisted with infrared thermometry was proposed to measure the diameter and the inside temperature gradient of a heated liquid cylinder. The inversion algorithm was designed based on the nonlinear least square method and an optimization process. To evaluate the feasibility of the proposed method, numerical simulations and experiments were carried out. The results of the numerical simulation showed that the relative error of the inversion diameter was about 1%, and the error of the refractive index was less than 6×10-4 at all the radial locations. In the experimental research, t rainbows reconstructed with the reversion parameters were all similar to the corresponding captured ones.

  12. Use of vertical temperature gradients for prediction of tidal flat sediment characteristics

    USGS Publications Warehouse

    Miselis, Jennifer L.; Holland, K. Todd; Reed, Allen H.; Abelev, Andrei

    2012-01-01

    Sediment characteristics largely govern tidal flat morphologic evolution; however, conventional methods of investigating spatial variability in lithology on tidal flats are difficult to employ in these highly dynamic regions. In response, a series of laboratory experiments was designed to investigate the use of temperature diffusion toward sediment characterization. A vertical thermistor array was used to quantify temperature gradients in simulated tidal flat sediments of varying compositions. Thermal conductivity estimates derived from these arrays were similar to measurements from a standard heated needle probe, which substantiates the thermistor methodology. While the thermal diffusivities of dry homogeneous sediments were similar, diffusivities for saturated homogeneous sediments ranged approximately one order of magnitude. The thermal diffusivity of saturated sand was five times the thermal diffusivity of saturated kaolin and more than eight times the thermal diffusivity of saturated bentonite. This suggests that vertical temperature gradients can be used for distinguishing homogeneous saturated sands from homogeneous saturated clays and perhaps even between homogeneous saturated clay types. However, experiments with more realistic tidal flat mixtures were less discriminating. Relationships between thermal diffusivity and percent fines for saturated mixtures varied depending upon clay composition, indicating that clay hydration and/or water content controls thermal gradients. Furthermore, existing models for the bulk conductivity of sediment mixtures were improved only through the use of calibrated estimates of homogeneous end-member conductivity and water content values. Our findings suggest that remotely sensed observations of water content and thermal diffusivity could only be used to qualitatively estimate tidal flat sediment characteristics.

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

    SciTech Connect

    Mavridis, M.; Isliker, H.; Vlahos, L.; Görler, T.; Jenko, F.; Told, D.

    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.

  14. Morning Martian Atmospheric Temperature Gradients and Fluctuations Observed by Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Mihalov, John D.; Haberle, R. M.; Murphy, J. R.; Seiff, A.; Wilson, G. R.

    1999-01-01

    We have studied the most prominent atmospheric temperature fluctuations observed during Martian mornings by Mars Pathfinder and have concluded, based on comparisons with wind directions, that they appear to be a result of atmospheric heating associated with the Lander spacecraft. Also, we have examined the morning surface layer temperature lapse rates, which are found to decrease as autumn approaches at the Pathfinder location, and which have mean (and median) values as large as 7.3 K/m in the earlier portions of the Pathfinder landed mission. It is plausible that brief isolated periods with gradients twice as steep are associated with atmospheric heating adjacent to Lander air bag material. In addition, we have calculated the gradient with height of the structure function obtained with Mars Pathfinder, for Mars' atmospheric temperatures measured within about 1.3 m from the surface, assuming a power law dependence, and have found that these gradients superficially resemble those reported for the upper region of the terrestrial stable boundary layer.

  15. Temperature, thermal efficiency, and gradient performance from two seawater-SZ solar ponds

    SciTech Connect

    Collado, F.; Lowrey, P. )

    1991-01-01

    This paper presents 10 months of experience with two seawater-SZ (Storage Zone) solar ponds operated as a source of warm seawater which could have been used in an adjacent mariculture facility. Observations and extensive temperature, gradient and efficiency data are presented. This work demonstrated operation of and heat extraction from seawater-SZ solar ponds over a much longer interval than in previous work. It confirmed that seawater-SZ solar ponds can consistently give useful temperature elevations. A few phenomena not characteristic of conventional solar ponds were identified and are discussed.

  16. The coherent gradient sensor for film curvature measurements at cryogenic temperature.

    PubMed

    Liu, Cong; Zhang, Xingyi; Zhou, Jun; Zhou, Youhe; Feng, Xue

    2013-11-04

    Coherent Gradient Sensor (CGS) system is presented for measurement of curvatures and nonuniform curvatures changes in film-substrate systems at cryogenic temperature. The influences of the interface of refrigerator and itself on the interferograms which are accounting for the temperature effect are successfully eliminated. Based on the measurement technique, the thermal stresses (including the radial stress, circumferential stress and shear stress) of superconducting YBCO thin-film are obtained by the extended Stoney's formula during the heating process from 30K to 150K. Take the superconducting YBCO thin film as an example, the thermal stresses of which are gained successfully.

  17. Alfvénic ion temperature gradient activities in a weak magnetic shear plasma

    NASA Astrophysics Data System (ADS)

    Chen, W.; Ma, R. R.; Li, Y. Y.; Shi, Z. B.; Du, H. R.; Jiang, M.; Yu, L. M.; Yuan, B. S.; Li, Y. G.; Yang, Z. C.; Shi, P. W.; Ding, X. T.; Dong, J. Q.; Wang, Z. X.; Liu, Yi.; Xu, M.; Xu, Y. H.; Yang, Q. W.; Duan, X. R.

    2016-11-01

    We report the first experimental evidence of Alfvénic ion temperature gradient (AITG) modes in HL-2A Ohmic plasmas. A group of oscillations with f=15\\text{--}40 \\text{kHz} and n=3\\text{--}6 is detected by various diagnostics in high-density Ohmic regimes. They appear in the plasmas with peaked density profiles and weak magnetic shear, which indicates that corresponding instabilities are excited by pressure gradients. The time trace of the fluctuation spectrogram can be either a frequency staircase, with different modes excited at different times or multiple modes may simultaneously coexist. Theoretical analyses by the extended generalized fishbone-like dispersion relation (GFLDR-E) reveal that mode frequencies scale with ion diamagnetic drift frequency and ηi , and they lie in KBM-AITG-BAE frequency ranges. AITG modes are most unstable when the magnetic shear is small in low pressure gradient regions. Numerical solutions of the AITG/KBM equation also shed light on why AITG modes can be unstable for weak shear and low pressure gradients. It is worth emphasizing that these instabilities may be linked to the internal transport barrier (ITB) and H-mode pedestal physics for weak magnetic shear.

  18. Regional-scale directional changes in abundance of tree species along a temperature gradient in Japan.

    PubMed

    Suzuki, Satoshi N; Ishihara, Masae I; Hidaka, Amane

    2015-09-01

    Climate changes are assumed to shift the ranges of tree species and forest biomes. Such range shifts result from changes in abundances of tree species or functional types. Owing to global warming, the abundance of a tree species or functional type is expected to increase near the colder edge of its range and decrease near the warmer edge. This study examined directional changes in abundance and demographic parameters of forest trees along a temperature gradient, as well as a successional gradient, in Japan. Changes in the relative abundance of each of four functional types (evergreen broad-leaved, deciduous broad-leaved, evergreen temperate conifer, and evergreen boreal conifer) and the demography of each species (recruitment rate, mortality, and population growth rate) were analyzed in 39 permanent forest plots across the Japanese archipelago. Directional changes in the relative abundance of functional types were detected along the temperature gradient. Relative abundance of evergreen broad-leaved trees increased near their colder range boundaries, especially in secondary forests, coinciding with the decrease in deciduous broad-leaved trees. Similarly, relative abundance of deciduous broad-leaved trees increased near their colder range boundaries, coinciding with the decrease in boreal conifers. These functional-type-level changes were mainly due to higher recruitment rates and partly to the lower mortality of individual species at colder sites. This is the first report to show that tree species abundances in temperate forests are changing directionally along a temperature gradient, which might be due to current or past climate changes as well as recovery from past disturbances.

  19. A theoretical and numerical investigation of travelling wave induction microfluidic pumping in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Liu, Weiyu; Ren, Yukun; Shao, Jinyou; Jiang, Hongyuan; Ding, Yucheng

    2014-02-01

    The phenomenon of induction electrohydrodynamics (EHD) has recently received great attention as a promising driving mechanism for microfluidic pumping due to its miniaturization capability. To obtain a high working efficiency of induction micropumps, a vertical temperature gradient can be imposed along the depth of a pump channel. A travelling wave (TW) potential signal propagating along an electrode array at the channel substrate interacts with this conductive heat flux, resulting in a local free charge distribution inside the bulk fluid. The induced charge wave lags behind the voltage wave in the spatial phase, and this out-of-phase polarization based pumping effect exhibits a single structural dispersion at charge relaxation frequency of the dielectric system. The classical model of electrothermal flow has always been used to numerically obtain the flow field of TW pumps, but the effect of its small temperature gradient approximation has rarely been investigated. In this study, an enhanced treatment for induction EHD modelling is developed, in which the deflection of potential contour lines caused by large temperature gradients is successfully characterized by an advection-diffusion equation, and a more accurate expression of electrothermal body force is derived and introduced to fluid dynamics as a source term of electrical origin. For the calculation of a repulsion-type induction micropump, although both models present similar results in a small thermal gradient, the enhanced one can provide more exact frequency-dependence of the pump performance and spatial distribution of electrostatic force as well as the resulting velocity profile in an excessive heat flux. Furthermore, a model extension for Joule heating induced TW pumping is also presented, and surprisingly matches the unexpected nonlinear fluid flow behaviour at higher conductivities as reported in a pioneering literature. These results can provide valuable insights into induction pumping of lab

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

    SciTech Connect

    Serrano, I. G.; Hernando, A.; Marín, P.

    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. Chemical reactions accompanying fluid flow through granite held in a temperature gradient

    USGS Publications Warehouse

    Moore, Diane E.; Morrow, C.A.; Byerlee, J.D.

    1983-01-01

    Distilled water was passed at a low rate down a temperature gradient through cylinders of Barre and Westerly Granite. Temperatures ranged from 80-100??C at the outer edges of the cylinders to 250-300??C in central, drilled holes which housed the heating coils. The measured permeabilities of the granite cylinders decreased by as much as two orders of magnitude in experiments of 1-3 weeks' duration. The amount of permeability decrease varied directly with temperature and inversely with the rate of fluid flow. The compositions of the fluids discharged from the granites were functions of temperature and flow rate as well as mineral composition, with dissolved silica concentrations showing trends different from those of the other analyzed species. Fluids from experiments run at higher temperatures but at much lower initial rates of fluid flow had higher concentrations of most ions but substantially lower dissolved silica contents. In contrast, an increase in temperature at similar rates of fluid flow resulted in higher silica concentrations. In the experiments, the distilled water acquired enough dissolved materials at high temperatures to become supersaturated with respect to several minerals at the low-temperature edges of the cylinders. Some of this material, particularly silica, was deposited along grain boundaries and microfractures, causing the observed permeability decreases. The very low rates of fluid flow in some high-temperature experiments significantly increased the rates of SiO2 precipitation and reduced dissolved silica concentrations relative to other species in the discharged fluids. ?? 1983.

  2. Temperature gradient analyzers for compact high-resolution X-ray spectrometers

    PubMed Central

    Ishikawa, D.; Baron, A. Q. R.

    2010-01-01

    Compact high-resolution X-ray spectrometers with a one-dimensional temperature gradient at the analyzer crystal are considered. This gradient, combined with the use of a position-sensitive detector, makes it possible to relax the usual Rowland-circle condition, allowing increased space at the sample position for a given energy resolution or arm radius. Thus, for example, it is estimated that ∼meV resolution is possible with a 3 m analyzer arm and 200 mm clearance between the sample and detector. Simple analytic formulae are provided, supported by excellent agreement with ray-tracing simulations. One variation of this method also allows the detector position sensitivity to be used to determine momentum transfer, effectively improving momentum resolution without reducing (slitting down) the analyzer size. Application to medium-resolution (∼10–100 meV) inelastic X-ray scattering spectrometers with large angular acceptance is discussed, where this method also allows increased space at the sample. In some cases the application of a temperature gradient can improve the energy resolution even with a single-element detector. PMID:20029107

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

    SciTech Connect

    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.

  4. Electron Temperature Gradient Scale Measurements in ICRF Heated Plasmas at Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Houshmandyar, Saeid; Phillips, Perry E.; Rowan, William L.; Howard, Nathaniel T.; Greenwald, Martin

    2016-10-01

    It is generally believed that the temperature gradient is a driving mechanism for the turbulent transport in hot and magnetically confined plasmas. A feature of many anomalous transport models is the critical threshold value (LC) for the gradient scale length, above which both the turbulence and the heat transport increases. This threshold is also predicted by the recent multi-scale gyrokinetic simulations, which are focused on addressing the electron (and ion) heat transport in tokamaks. Recently, we have established an accurate technique (BT-jog) to directly measure the electron temperature gradient scale length (LTe =Te / ∇T) profile, using a high-spatial resolution radiometer-based electron cyclotron emission (ECE) diagnostic. For the work presented here, electrons are heated by ion cyclotron range of frequencies (ICRF) through minority heating in L-mode plasmas at different power levels, TRANSP runs determine the electron heat fluxes and the scale lengths are measured through the BT-jog technique. Furthermore, the experiment is extended for different plasma current and electron densities by which the parametric dependence of LC on magnetic shear, safety factor and density will be investigated. This work is supported by U.S. DoE OFES, under Award No. DE-FG03-96ER-54373.

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

    PubMed

    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.

  6. Temperature gradients drive radial fluid flow in Petri dishes and multiwell plates.

    PubMed

    Lindsay, Stephen M; Yin, John

    2016-06-01

    Liquid in a Petri dish spontaneously circulates in a radial pattern, even when the dish is at rest. These fluid flows have been observed and utilized for biological research, but their origins have not been well-studied. Here we used particle-tracking to measure velocities of radial fluid flows, which are shown to be linked to evaporation. Infrared thermal imaging was used to identify thermal gradients at the air-liquid interface and at the bottom of the dish. Two-color ratiometric fluorescence confocal imaging was used to measure thermal gradients in the vertical direction within the fluid. A finite-element model of the fluid, incorporating the measured temperature profiles, shows that buoyancy forces are sufficient to produce flows consistent with the measured particle velocity results. Such flows may arise in other dish or plate formats, and may impact biological research in positive or negative ways.

  7. Why charged molecules move across a temperature gradient: the role of electric fields.

    PubMed

    Reichl, Maren; Herzog, Mario; Götz, Alexandra; Braun, Dieter

    2014-05-16

    Methods to move solvated molecules are rare. Apart from electric fields, only thermal gradients are effective enough to move molecules inside a fluid. This effect is termed thermophoresis, and the underlying mechanisms are still poorly understood. Nevertheless, it is successfully used to quantify biomolecule binding in complex liquids. Here we show experiments that reveal that thermophoresis in water is dominated by two electric fields, both established by the salt ions of the solution. A local field around the molecule drives molecules along an energy gradient, whereas a global field moves the molecules by a combined thermoelectrophoresis mechanism known as the Seebeck effect. Both mechanisms combined predict the thermophoresis of DNA and RNA polymers for a wide range of experimental parameters. For example, we correctly predict a complex, nonlinear size transition, a salt-species-dependent offset, a maximum of thermophoresis over temperature, and the dependence of thermophoresis on the molecule concentration.

  8. Diversification of Bacterial Community Composition along a Temperature Gradient at a Thermal Spring

    PubMed Central

    Everroad, R. Craig; Otaki, Hiroyo; Matsuura, Katsumi; Haruta, Shin

    2012-01-01

    To better understand the biogeography and relationship between temperature and community structure within microbial mats, the bacterial diversity of mats at a slightly alkaline, sulfide-containing hot spring was explored. Microbial mats that developed at temperatures between 75–52°C were collected from an area of approximately 1 m2 in Nakabusa, Nagano, Japan. Bacterial 16S rRNA genes from these samples were examined by terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis. T-RFLP profiles revealed 66 unique fragments (T-RFs). Based on total T-RFs observed in environmental profiles and clone libraries, a temperature effect on diversity was determined, with complexity in the community increasing as temperature decreased. The T-RF pattern indicated four distinct community assemblages related to temperature. Members of the Aquificales and particularly the sulfuroxidizing bacterium Sulfurihydrogenibium were present at all temperatures and were the dominant component of mats taken at 75–67°C. Sulfide oxidation, which persisted throughout the temperature gradient, was the presumed dominant pathway of primary production above 67°C. As temperature decreased, successive additions of anoxygenic and oxygenic phototrophs increased primary productivity, allowing for diversification of the community. PMID:22673306

  9. Temperatures and interval geothermal-gradient determinations from wells in National Petroleum Reserve in Alaska

    USGS Publications Warehouse

    Blanchard, D.C.; Tailleur, I.L.

    1982-01-01

    Temperature and related records from 28 wells in the National Petroleum Reserve in Alaska (NPRA) although somewhat constrained from accuracy by data gathering methods, extrapolate to undisturbed formation temperatures at specific depths below permafrost, and lead to calculated geothermal gradients between these depths. Tabulation of the results show that extrapolated undisturbed temperatures range from a minimum of 98?F (37?C) at 4,000 feet (1,220 m) to a maximum of 420?F (216?C) at 20,260 feet (6,177 m) and that geothermal gradients range from 0.34?F/100' (6?C/km) between 4,470 feet to 7,975 feet (Lisburne (1) and 3.15?F/100? (57?C/km) between 6,830 feet to 7,940 feet (Drew Point #1). Essential information needed for extrapolations consists of: time-sequential 'bottom-hole' temperatures during wire-line logging of intermediate and deep intervals of the bore hole; the times that circulating drilling fluids had disturbed the formations; and the subsequent times that non-circulating drilling fluids had been in contact with the formation. In several wells presumed near direct measures of rock temperatures recorded from formation fluids recovered by drill stem tests (DST) across thin (approx. 10-20 foot) intervals are made available. We believe that the results approach actual values close enough to serve as approximations of the thermal regimes in appropriate future investigations. Continuous temperature logs obtained at the start and end of final logging operations, conductivity measurements, and relatively long-term measurements of the recovery from disturbance at shallow depths in many of the wells will permit refinements of our values and provide determination of temperatures at other depths.

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

    PubMed

    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.

  11. [The temperature and temperature gradient distribution in the thermophysical model of the rabbit body subjected internal and external changes of temperature].

    PubMed

    Rumiantsev, G V

    2002-03-01

    In a laboratory heat-physical model of the rabbit reflecting basic heat-physical parameters of animal body (weight, heat absorption and heat production, size of a relative surface, capacity heat-production etc.), the changes of radial distribution of temperature and size of a cross superficial temperature gradient of the body were investigated with various parities (ratio) of environmental temperature and size of capacity heat production imitated by an electrical heater. Superficial layer of the body dependent from capacity heat production and environmental temperature can serve for definition of general heat content changes in the body for maintaining its thermal balance within the environment.

  12. Day-night Temperature Gradients and Atmospheric Collapse on Synchronously Rotating Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Koll, D. D. B.; Abbot, D. S.

    2015-12-01

    Terrestrial exoplanets orbiting small host stars are abundant and are also the most promising observational targets for finding life outside our Solar system. Due to their close-in orbits, these planets experience significant tidal interactions with their host stars and will tend to evolve towards spin-orbit resonances or synchronous rotation (=tidally locked). Synchronous rotation has a number of interesting implications for habitability, including the potential for atmospheric collapse on the night side if the surface temperature drops below the condensation point of the gases in the atmosphere. To understand the habitability of synchronously rotating planets, it is therefore important to work out a theory of their temperature and wind structure. Many of these planets will be rotating slowly enough that the well-known weak-temperature-gradient theory holds in the free atmosphere, but even for these planets this theory does not constrain the maximum surface temperature gradient, the planets' thermal phase curve signature, or the threshold for atmospheric collapse. Here we study tidally locked planets using theory and a large array of simulations in a global climate model (GCM) with grey radiative transfer and a full boundary layer scheme. We derive a theory for surface temperatures and atmospheric circulation on synchronously rotating planets that allows us to predict the night-side surface temperature and determine whether atmospheric collapse will occur. We find that atmospheric collapse is sensitive to both the ratio of the Rossby radius to the planetary radius and the ratio of the surface drag timescale to the radiative cooling timescale.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Determination of surface normal temperature gradients using thermographic phosphors and filtered Rayleigh scattering

    NASA Astrophysics Data System (ADS)

    Brübach, J.; Zetterberg, J.; Omrane, A.; Li, Z. S.; Aldén, M.; Dreizler, A.

    2006-09-01

    Wall temperature as well as the temperature distribution within or close-by the boundary layer of an electrically heated axisymmetric jet impinging on a flat plate were monitored to deduce wall-normal temperature gradients. The radial surface temperature profile of the plate was determined by coating it with thermographic phosphors (TPs), materials whose phosphorescence decay time is dependent on their temperature. The TP was excited electronically by a frequency-tripled Nd:YAG laser (355 nm) and the temporal decay of the phosphorescence intensity was measured zero-dimensionally by a photomultiplier tube. In this case the 659-nm emission line of Mg3F2GeO4:Mn was monitored. The non-intrusive measurement of gas temperatures near the surface was performed two-dimensionally by filtered Rayleigh scattering (FRS). A tunable frequency-tripled single-longitudinal-mode alexandrite laser beam at 254 nm was formed into a light sheet pointing parallel to the surface. The scattered light was imaged through a very narrow linewidth atomic mercury filter onto an intensified charged coupled device (ICCD). The elastic stray light from surfaces was strongly suppressed, whereas Doppler-broadened light was detected. Thermographic phosphors proved to be reliable for the measurement of surface temperatures. Dependent on the specific experimental conditions, problems appeared with signals interfering with the FRS radiation close-by the surface. Results and challenges of this approach are discussed.

  15. Evaluating Changes in Paleo-temperature Gradients using Hydrogen Isotopic Compositions of Leaf-wax Biomarkers

    NASA Astrophysics Data System (ADS)

    Krishnan, S.; Huber, M.; Pagani, M.

    2014-12-01

    A long-standing problem in the paleoclimate modeling community has been the inability of the models to reproduce the shallow meridional temperature gradient (∆T) observed in proxy temperature records for the warm, greenhouse time intervals in Earth's history, such as the early Eocene. It is often stated that this mismatch indicates a missing high-latitude feedback mechanism in the climate models that would cause substantial polar amplification of warming. However, this issue is complicated by the potential biasing of proxy records due to issues related to temperature calibrations and/or diagenesis. In this study, we propose an alternative approach to estimate ∆T for these time intervals using hydrogen isotopic composition of leaf-wax biomarkers (dDleaf-wax) preserved in the sedimentary record. Today, dDleaf-wax is closely related to the hydrological cycle and source vegetation. In the mid- and high-latitudes, dDleaf-wax changes pertaining to the hydrological cycle can be interpreted using a Rayleigh distillation process, where evaporated moisture from the sub-tropics undergoes isotopic fractionation and becomes increasingly D-depleted during poleward transport. We develop a box model based on the Rayleigh distillation process that uses the global mean temperature for the time-period and geological archives of dDleaf-wax to estimate the meridional temperature gradient. We use this box model for the Paleocene-Eocene Thermal Maximum (PETM; ~56Ma), a rapid-warming event in the early Eocene where global warming is accompanied by evidence for increased input of greenhouse gases. We compile existing leaf-wax dDleaf-wax records from the extra-tropics to estimate ∆T before and during the PETM. Preliminary results suggest that the temperature gradient increased during the body of the PETM, contradicting our expectations based on temperature proxies. We also use this approach to estimate ∆T during other intervals in earth's history, such as the early Eocene. Further

  16. Tropical cyclogenesis under the hypohydrostatic rescaling in climates with different equator-to-pole temperature gradients.

    NASA Astrophysics Data System (ADS)

    Muir, L.; Boos, W. R.; Fedorov, A. V.

    2015-12-01

    Simulations of strong tropical cyclones, category 3 to 5, in models without convective parameterization typically require a high horizontal resolution on the order of several kilometers, which is currently not feasible for global climate models. In this study we apply the hypohydrostatic rescaling, also referred to as RAVE (Reduced Acceleration in the Vertical, e.g. Kuang et al. 2005), as a means to improve the representation of tropical cyclones in a cloud-resolving model that explicitly represents moist convection (SAM). In effect, RAVE reduces the scale separation between convective and larger-scale motions, enabling the simultaneous and explicit representation of both types of flow in a single model. At a given horizontal resolution, using RAVE increases peak storm intensity and reduces the time needed for tropical cyclogenesis, effects apparently caused by the environmental moistening produced by RAVE. In fact, using RAVE in this model within a global aqua-planet beta-plane configuration improves representation of both the mean tropical climate (eliminating the double-ITCZ problem) and of tropical cyclones (generating storms up to category 5). Further, we present results of these simulations in which we vary the equator-to-pole temperature gradient and focus on the key characteristics of tropical cyclones, including the total number of cyclones, their genesis, strength and latitudinal distribution, and interaction with extra-tropical storms. We find that the tropical cyclone activity changes non-monotonically with reduction in the oceanic meridional temperature gradient - for small changes the cyclone activity decreases, but for larger changes it strongly increases, mainly because of the strong reduction in wind shear in mid-latitudes for weak meridional temperature gradients. The increase in tropical cyclone activity in warm climates is accompanied by the merging between the characteristics of extra-tropical storms and tropical cyclones, as seen in the paths

  17. A Study of Solar Photospheric Temperature Gradient Variation Using Limb Darkening Measurements

    NASA Astrophysics Data System (ADS)

    Criscuoli, Serena; Foukal, Peter

    2017-01-01

    The variation in area of quiet magnetic network measured over the sunspot cycle should modulate the spatially averaged photospheric temperature gradient, since temperature declines with optical depth more gradually in magnetic flux tube atmospheres. Yet, limb darkening measurements show no dependence upon activity level, even at an rms precision of 0.04%. We study the sensitivity of limb darkening to changes in area filling factor using a 3D MHD model of the magnetized photosphere. The limb darkening change expected from the measured 11-year area variation lies below the level of measured limb darkening variations, for a reasonable range of magnetic flux in quiet network and internetwork regions. So the remarkably constant limb darkening observed over the solar activity cycle is not inconsistent with the measured 11-year change in area of quiet magnetic network. Our findings offer an independent constraint on photospheric temperature gradient changes reported from measurements of the solar spectral irradiance from the Spectral Irradiance Monitor, and recently, from wavelength-differential spectrophotometry using the Solar Optical Telescope aboard the HINODE spacecraft.

  18. A multi-decade history of soil carbon turnover along a temperature gradient

    SciTech Connect

    Townsend, A.R.; Trumbore, S.E.; Vitousek, P.M. Univ. of California, Irvine )

    1993-06-01

    We used an altitudinal gradient on the northeast flank of Mauna Kea Volcano, island of Hawaii to examine the effects of temperature on soil carbon turnover and stabilization. The gradient consists of C[sub 3] rainforest in parallel to C[sub 4] pastures converted from this forest several decades ago. Sites with little variation in rainfall or vegetation type were chosen on volcanic ash soils of similar ages. We obtained [delta][sup 13]C and [Delta][sup 14]C values for bulk soils and [delta][sup 13]C values for CO[sub 2] evolved in the field and from microbial fumigations. We constructed an isotope dilution model that uses the isotope data along with data on net primary productivity and total soil carbon to estimate relative pool sizes of highly recalcitrant [open quotes]passive[close quotes] and more labile [open quotes]non-passive[close quotes] soil carbon. Results of this model show that decomposition rates for carbon turning over at annual to decadal time scales increase with increasing temperature in a linear to saturating fashion. This response differs from the exponential relationships reported in numerous studies of litter decomposition and/or soil respiration. If soil carbon turnover as a whole is not an exponential function of temperature, then soils would be far less likely to be a net source of atmospheric CO[sub 2] in a warmer climate.

  19. The effect of magnetic islands on Ion Temperature Gradient turbulence driven transport

    SciTech Connect

    Hill, P.; Hariri, F.; Ottaviani, M.

    2015-04-15

    In this work, we address the question of the influence of magnetic islands on the perpendicular transport due to steady-state ITG turbulence on the energy transport time scale. We demonstrate that turbulence can cross the separatrix and enhance the perpendicular transport across magnetic islands. As the perpendicular transport in the interior of the island sets the critical island size needed for growth of neoclassical tearing modes, this increased transport leads to a critical island size larger than that predicted from considering collisional conductivities, but smaller than that using anomalous effective conductivities. We find that on Bohm time scales, the turbulence is able to re-establish the temperature gradient across the island for islands widths w ≲ λ{sub turb}, the turbulence correlation length. The reduction in the island flattening is estimated by comparison with simulations retaining only the perpendicular temperature and no turbulence. At intermediate island widths, comparable to λ{sub turb}, turbulence is able to maintain finite temperature gradients across the island.

  20. Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

    NASA Astrophysics Data System (ADS)

    Livescu, Daniel; Gerashchenko, Sergiy

    2016-11-01

    The growth rate of the compressible Rayleigh-Taylor instability is studied in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous and viscous-inviscid) at different Atwood numbers, At, and, when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. Compared to the Θ = 0 case, the role of Θ < 0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ > 0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of a background temperature gradient, when the viscosity is temperature dependent.

  1. Effect of temperature gradients on the wave aberration in athermal optical glasses.

    PubMed

    Reitmayer, F; Schroeder, H

    1975-03-01

    Temperature gradients that are caused by partial heating in optical elements may result in wave aberrations. The athermal glasses developed within the past two years exhibit considerably reduced thermal wave aberrations compared to the classical optical glasses. Evidence is given that the total wave aberration is due not only to the change of optical path DeltaW(Gamma) computed from a, n, and dn/dT, but also that, upon the occurrence of thermal stresses, an additional wave aberration DeltaW(s) must be taken into consideration.

  2. Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds

    NASA Technical Reports Server (NTRS)

    Atwater, James E.; Akse, James R.; Jovanovic, Goran N.; Wheeler, Richard R Jr; Sornchamni, Thana

    2003-01-01

    Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co3O4 into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry. c2003 Elsevier Science Ltd. All rights reserved.

  3. Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds.

    PubMed

    Atwater, James E; Akse, James R; Jovanovic, Goran N; Wheeler, Richard R; Sornchamni, Thana

    2003-02-20

    Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co3O4 into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry.

  4. Finite Larmor radius effects on the coupled trapped electron and ion temperature gradient modes

    SciTech Connect

    Sandberg, I.; Isliker, H.; Pavlenko, V. P.

    2007-09-15

    The properties of the coupled trapped electron and toroidal ion temperature gradient modes are investigated using the standard reactive fluid model and taking rigorously into account the effects attributed to the ion polarization drift and to the drifts associated with the lowest-order finite ion Larmor radius effects. In the flat density regime, where the coupling between the modes is relatively weak, the properties of the unstable modes are slightly modified through these effects. For the peak density regions, where the coupling of the modes is rather strong, these second-order drifts determine the spectra of the unstable modes near the marginal conditions.

  5. Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds

    SciTech Connect

    Atwater, James E.; Akse, James R.; Jovanovic, Goran N.; Wheeler, Richard R.; Sornchamni, Thana

    2003-02-20

    Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co{sub 3}O{sub 4} into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26493738

  7. Eutectic pattern transition under different temperature gradients: A phase field study coupled with the parallel adaptive-mesh-refinement algorithm

    NASA Astrophysics Data System (ADS)

    Zhang, A.; Guo, Z.; Xiong, S.-M.

    2017-03-01

    Eutectic pattern transition under an externally imposed temperature gradient was studied using the phase field method coupled with a novel parallel adaptive-mesh-refinement (Para-AMR) algorithm. Numerical tests revealed that the Para-AMR algorithm could improve the computational efficiency by two orders of magnitude and thus made it possible to perform large-scale simulations without any compromising accuracy. Results showed that the direction of the temperature gradient played a crucial role in determining the eutectic patterns during solidification, which agreed well with experimental observations. In particular, the presence of the transverse temperature gradient could tilt the eutectic patterns, and in 3D simulations, the eutectic microstructure would alter from lamellar to rod-like and/or from rod-like to dumbbell-shaped. Furthermore, under a radial temperature gradient, the eutectic would evolve from a dumbbell-shaped or clover-shaped pattern to an isolated rod-like pattern.

  8. Understanding High Temperature Gradients in the Buckman Well Field, Santa Fe County, New Mexico

    NASA Astrophysics Data System (ADS)

    Folsom, M.; Gulvin, C. J.; Tamakloe, F. M.; Yauk, K.; Kelley, S.; Frost, J.; Jiracek, G. R.

    2014-12-01

    We propose a conceptual model to explain elevated thermal gradients, localized laterally over a few 100 m, discovered during the SAGE program in 2013 and confirmed in 2014 at the Buckman water well field in the Española Basin of north central New Mexico. The anomalous gradients of temperature with depth, dT/dz, exceed 70 ºC/km and are found in three shallow (< 100 m-deep) USGS monitoring wells close to the Rio Grande. A temperature increase of only 3 - 4 ºC at ~100 m depth would elevate the regional temperature value enough to yield the anomalous dT/dz values in the upper ~100 m. The coincidence of a 25 km2 region of InSAR-confirmed subsidence with the locally anomalous dT/dz region suggests a way to achieve a higher temperature at ~ 100 m depth. The mechanism is an isothermal release of warmer water from ~ 200 m depth along a fissure or reactivated fault. A fourth well, 290 m away, has a temperature gradient of only 33ºC/km in the upper 100 m and a distinctly different geochemical profile, suggesting aquifer compartmentalization and possible faulting close to the anomaly. In 2001 a 800 m-long surface scarp with up to 0.2 m offset appeared 2 km to the east in response to over-pumping that depressed the groundwater table by over 100 m. Such drawdown is expected to have 2 - 5 m of compaction with attendant movement along faults or fissures. This could allow groundwater to be released upward isothermally until encountering an unbreached aquitard where it would establish an elevated thermal boundary. Besides the local thermal anomaly, we have temperature-logged deeper water wells in the area. These and other measurements have been used to construct cross-sections of isotherms across the Española Basin along the groundwater flow units (GFUs). This allows comparison of the local thermal anomaly with classic, regional, basin hydrological models. For example, the fully-screened Skillet well, 2.3 km from the anomaly, shows a classic concave down dT/dz form indicating

  9. Exploiting the weak temperature gradient approximation for climate theory on slowly rotating, tidally locked planets

    NASA Astrophysics Data System (ADS)

    Mills, S. M.; Abbot, D. S.; Pierrehumbert, R.

    2011-12-01

    Tidally locked planets are subject to extreme temperature variations due to the stellar flux directly warming only one side of the planet. This is important because planets in the habitable zone around M dwarf stars are likely to be tidally locked. Such planets are unlikely to be habitable if their antistellar temperatures are low enough that CO2 will condense. This problem has previously been investigated using GCMs, which explicitly solve for atmospheric dynamics. In order to gain a greater understanding of the effect of different mechanisms on the temperature profile, we use a lower-order energy balance model here. We consider tidally locked planets that rotate slowly enough that we can neglect the Coriolis force, which allows us to assume that atmospheric temperature at any given height is independent of horizontal position (weak temperature gradient approximation). This allows us to easily isolate and contrast the effects of different physical mechanisms, such as greenhouse gas level and surface turbulent exchange, on the resulting temperature profile. We find that the effect of turbulent exchange on climate saturates at fairly low values (very smooth planets), whereas CO2 has a consistently strong effect on climate.

  10. Long-term continuous observation of vertical gradient of water temperature on the deep seafloor

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Hino, R.; Ito, Y.; Kubota, T.; Inazu, D.

    2015-12-01

    We have conducted ocean bottom pressure observations near the Japan Trench and the Kuril Trench using self-pop-up type instruments to detect seafloor vertical displacement accompanied by slip events along the plate boundary faults. Recently, we have started similar observation campaigns in the Hikurangi subduction zone, off the North Island of New Zealand since 2013. As a result of the observations, we have observed an uplift of 5 m due to the 2011 Tohoku-Oki earthquake (Ito et al., 2011) and transient crustal deformations accompanied by slow slip events preceding the earthquake (Ito et al., 2013). Precision thermometer, usually used for temperature compensation of the pressure readings, occasionally recorded strange temperature changes related to occurrence of submarine earthquakes or tsunamis. Arai et al. (2013) interpreted noticeable temperature changes observed after the 2011 Tohoku-Oki earthquake and interpreted it as the result of the turbidity current induced by massive tsunami. Inazu et al. (2015) pointed out a possibility that the temperature disturbance recorded just after the Tohoku-Oki earthquake above the large coseismic slip zone was due to the discharged of submarine groundwater associated with the earthquake. In order to describe these strange temperature signals more quantitatively, we started trial observations allowing investigation of water temperature field on the deep seafloor. In this study, we installed two precision temperature loggers top and bottom of the ocean bottom pressure recorders, with ~ 60 cm in height, to measure vertical gradients of seawater temperature as well as the ocean bottom pressures. Here, we report about 1-year continuous records retrieved from the Japan Trench and off New Zealand. During the observation off New Zealand, an evident slow slip event was identified by the onshore geodetic observations near the locations of our seafloor pressure-temperature monitoring. We are now exploring possible thermal and pressure

  11. AIRS satellite observations of meridional temperature gradient over Indian summer monsoon region

    NASA Astrophysics Data System (ADS)

    Dhaka, S. K.; Gupta, A.; Panwar, V.; Bhatnagar, R.

    2011-12-01

    To investigate temperature changes in the upper troposphere over Indian region covering from Arabian Sea (AS) to Bay of Bengal (BOB), analysis is carried out during both summer (May-June-July-August) and winter (November-December-January-February) using AIRS data at a high spatial (1×1 lat long) resolution over sea and land spanned over 2005-2010. This is done to examine the similarities and differences in the meridional temperature gradient during Asian summer monsoon and winter. During May, there is an increase in temperature latitudinal from 3oN to 20oN by ~ 2.5 K in the all the years, however, temperature is decreased gradually (~ 0.15 K per deg latitude) by ~3 K during June-July-Aug (JJA). Thus, there is a contrast behavior observed in the meridional variation of temperature during May with that of JJA. The study further suggests the latitudinal change in temperature occurs due to low OLR (convection) and its northward progression during summer. Similar analysis for the winter months (NDJF) shows the existence of latitudinal variation in temperature which has an increasing tendency from 3oN to 20oN. The change in temperature is larger (~4-5K) for winter months as compared to the summer months, the apparent change is caused by the presence of monsoon during summer months (high humidity and water vapors). During winter, the variability in temperature for Nov and Dec is found larger as compared to Jan and Feb because of increased convection (low OLR) at low latitudes (3-10oN) in the former months and latter being the dry months with no convection.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Study of near scrape-off layer (SOL) temperature and density gradient lengths with Thomson scattering

    NASA Astrophysics Data System (ADS)

    Sun, H. J.; Wolfrum, E.; Eich, T.; Kurzan, B.; Potzel, S.; Stroth, U.; the ASDEX Upgrade Team

    2015-12-01

    Improvements to the Thomson scattering diagnostic have enabled the study of near scrape-off layer (SOL) decay lengths in the 2014 ASDEX Upgrade experimental campaign. A database of H-mode discharges has been studied using a two-line fit method for the core and log-linear fit for the near SOL region under both attached and detached divertor conditions. SOL electron temperature {{T}e} profiles have been found to have a radial exponential decay distribution which does not vary poloidally, consistent with the two-point model. In attached H-mode regimes, a log-linear regression shows that the SOL upstream dataset has the same main parametric dependencies as the scaling inferred from downstream Infrared camera measurements. A simple collisional relation from two-point model is found to best relate the upstream decay lengths and downstream divertor power widths. The SOL {{T}e} gradient length appears to be independent of {{T}e} pedestal parameters, but may correlate with the pedestal electron pressure parameters. Both the pedestal and SOL density and temperature scale lengths are linearly correlated with an almost constant gradient ratio, {ηe} . The smaller gradient ratio {ηe} and the fact that the Spitzer-Härm model is more valid, agrees with the studied plasma lying in the collisional regime. A transition to flat SOL ne profiles, previously reported for L-mode plasmas in many machines, has been observed in AUG detatched H-mode regimes. When the flattening of density profile happens in H-mode detached plasmas, the broadening of near SOL {{T}e} decay length {λ{{Te,u}}} also appears which may be good news for future machines.

  14. Convection in rotating flows with simultaneous imposition of radial and vertical temperature gradients

    NASA Astrophysics Data System (ADS)

    Banerjee, Ayan Kumar; Bhattacharya, Amitabh; Balasubramanian, Sridhar

    2016-11-01

    Laboratory experiments, with a rotating cylindrical annulus and thermal gradient in both radial and vertical directions (so that radial temperature difference decreases with the elevation), were conducted to study the convection dynamics and heat transport. Temperature data captured using thermocouples, combined with ANSYS Fluent simulation hinted at the co-existence of thermal plume and baroclinicity (inclined isotherms). Presence of columnar plume structure parallel to the rotation axis was found, which had a phase velocity and aided in vertical heat transport. Nusselt number (Nu) plotted as a function of Taylor number (Ta) showed the effect of rotation on heat transport in such systems, where the interplay of plumes and baroclinic waves control the scalar transport. Laser based PIV imaging at a single vertical plane also showed evidence of such flow structures.

  15. Investigation of photospheric temperature gradient variations using limb darkening measurements and simulations

    NASA Astrophysics Data System (ADS)

    Criscuoli, Serena; Foukal, Peter V.

    2016-05-01

    The temperature stratifications of magnetic elements and unmagnetized plasma are different, so that changes of the facular and network filling factor over the cycle modify the average temperature gradient in the photosphere.Such variations have been suggested to explain irradiance measurements obtained by the SIM spectrometers in he visible and infrared spectral ranges. On the other hand, limb darkening measurements show no dependence upon activity level. We investigate the sensitivity of limb darkening to changes in network area filling factor using a 3-D MHD model of the magnetized photosphere. We find that the expected limb darkening change due to the measured 11- yr variation in filling factor lies outside the formal 99% confidence limit of the limb darkening measurements. This poses important constraints for observational validation of 3D-MHD simulations.

  16. A Numerical Model Study of Nocturnal Drainage Flows with Strong Wind and Temperature Gradients.

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Bunker, S.

    1989-07-01

    A second-moment turbulence-closure model described in Yamada and Bunker is used to simulate nocturnal drainage flows observed during the 1984 ASCOT field expedition in Brush Creek, Colorado. In order to simulate the observed strong wind directional shear and temperature gradients, two modifications are added to the model. The strong wind directional shear was maintained by introducing a `nudging' term in the equation of motion to guide the modeled winds in the layers above the ridge top toward the observed wind direction. The second modification was accomplished by reformulating the conservation equation for the potential temperature in such a way that only the deviation from the horizontally averaged value was prognostically computed.The vegetation distribution used in this study is undoubtedly crude. Nevertheless, the present simulation suggests that tall tree canopy can play an important role in producing inhomogeneous wind distribution, particularly in the levels below the canopy top.

  17. Ecophotonics: assessment of temperature gradient in aquatic organisms using up-conversion luminescent particles

    NASA Astrophysics Data System (ADS)

    Volkova, E. K.; Yanina, I. Yu; Popov, A. P.; Bykov, A. V.; Gurkov, A. N.; Borvinskaya, E. V.; Timofeyev, M. A.; Meglinski, I. V.

    2017-02-01

    In the frameworks of developing ecophotonics, we consider the possibility of applying luminescence spectroscopy for monitoring conditions of aquatic organisms, aimed at the study and prognosis of the effect of human activity and climate changes on the environment. The method of luminescence spectroscopy in combination with anti-Stokes luminophores (up-conversion particles) used as optical sensors is used for the noninvasive assessment of the temperature gradient in the internal tissues of aquatic organisms. It is shown that the temperature dependence of the intensity ratio observed in the maxima of the luminescence spectrum bands of the particles Y2O3 : Yb, Er, administered in a biological object, is linear. This fact offers a possibility of using the up-conversion particles for assessing the metabolic activity of different tissues, including those in the framework of ecological monitoring.

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

    PubMed

    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.

  19. Fine-Scale Zonal Flow Suppression of Electron Temperature Gradient Turbulence

    SciTech Connect

    Parker, S. E.; Kohut, J. J.; Chen, Y.; Lin, Z.; Hinton, F. L.; Lee, W. W.

    2006-11-30

    It is found in collisionless Electron Temperature Gradient (ETG) turbulence simulations that, while zonal flows are weak at early times, the zonal flows continue to grow algebraically (proportional to time). These fine-scale zonal flows have a radial wave number such that kr{rho}i > 1 and kr{rho}e < 1. Eventually, the zonal flows grow to a level that suppresses the turbulence due to ExB shearing. The final electron energy flux is found to be relatively low. These conclusions are based on particle convergence studies with adiabatic ion electrostatic flux-tube gyrokinetic {delta}f particle simulations run for long times. The Rosenbluth-Hinton random walk mechanism is given as an explanation for the long time build up of the zonal flow in ETG turbulence and it is shown that the generation is (k perpendicular {rho}e)2 smaller than for isomorphic Ion Temperature Gradient (ITG) problem. This mechanism for zonal flow generation here is different than the modulational instability mechanism for ITG turbulence. These results are important because previous results indicated zonal flows were unimportant for ETG turbulence. Weak collisional damping of the zonal flow is also shown to be a n important effect.

  20. Wave-particle interaction and the nonlinear saturation of the electron temperature gradient mode

    NASA Astrophysics Data System (ADS)

    Vadlamani, Srinath; Parker, Scott E.; Chen, Yang; Howard, James E.

    2004-11-01

    It has been proposed that the electron temperature gradient (ETG) driven turbulence is responsible for experimentally relevant electron thermal transport in tokamak plasmas. Significant transport levels are possible by the creation of radially elongated vortices or ``streamers" [1,2], which are sustained by the nonlinear saturation of the instability and are not susceptible to shear flow destruction, as is the case with the ion temperature gradient (ITG) mode. We present a dynamical system to explore the dependence of saturation level due to E × B and E_\\| motion, as well as the effect of radial elongation. With this model, we can predict the nonlinear saturation level of the ETG streamers. We compare our theoretical predictions with a 2D shear-less slab gyrokinetic electron code that includes the E_\\| nonlinearity. [1]F. Jenko, W. Dorland, M Kotschenreuther, and B.N. Rogers, Phys. Plasmas 7, 1904 (2000). [2]C. Holland, and P.H. Diamond, Phys. Plasmas 9, 3857 (2002). [3]W. M. Manheimer, Phys. Fluids 14, 579 (1971). [4]R. A. Smith, John A. Krommes, and W. W. Lee, Phys. Fluids 28, 1069 (1985).

  1. Variable but persistent coexistence of Prochlorococcus ecotypes along temperature gradients in the ocean's surface mixed layer.

    PubMed

    Chandler, Jeremy W; Lin, Yajuan; Gainer, P Jackson; Post, Anton F; Johnson, Zackary I; Zinser, Erik R

    2016-04-01

    The vast majority of the phytoplankton communities in surface mixed layer of the oligotrophic ocean are numerically dominated by one of two ecotypes of Prochlorococcus, eMIT9312 or eMED4. In this study, we surveyed large latitudinal transects in the Atlantic and Pacific Ocean to determine if these ecotypes discretely partition the surface mixed layer niche, or if populations exist as a continuum along key environmental gradients, particularly temperature. Transitions of dominance occurred at approximately 19-21°C, with the eMED4 ecotype dominating the colder, and eMIT9312 ecotype dominating the warmer regions. Within these zones of regional dominance, however, the minority ecotype was not competed to extinction. Rather, a robust log-linear relationship between ecotype ratio and temperature characterized this stabilized coexistence: for every 2.5°C increase in temperature, the eMIT9312:eMED4 ratio increased by an order of magnitude. This relationship was observed in both quantitative polymerase chain reaction and in pyrosequencing assays. Water column stratification also contributed to the ecotype ratio along the basin-scale transects, but to a lesser extent. Finally, instances where the ratio of the eMED4 and eMIT9312 abundances did not correlate well with temperature were identified. Such occurrences are likely due to changes in water temperatures outpacing changes in community structure.

  2. Estimation of in-situ thermal conductivities from temperature gradient measurements

    SciTech Connect

    Hoang, V.T.

    1980-12-01

    A mathematical model has been developed to study the effect of variable thermal conductivity of the formations, and the wellbore characteristics, on the fluid temperature behavior inside the wellbore during injection or production and after shut-in. During the injection or production period the wellbore fluid temperature is controlled mainly by the fluid flow rate and the heat lost from the fluid to the formation. During the shut-in period, the fluid temperature is strongly affected by differences in the formation thermal conductivities. Based on the results of the present analysis, two methods for estimating in-situ thermal conductivity were derived. First, the line source concept is extended to estimate values of the formation thermal conductivities utilizing the fluid temperature record during the transient period of injection or production and shut-in. The second method is applied when a well is under thermal equilibrium conditions. Values of the formation thermal conductivities can also be estimated by using a continuous temperature gradient log and by measuring the thermal conductivity of the formation at a few selected wellbore locations.

  3. Assessing the temperature sensitivity of soil carbon decomposition along a geo-climatic gradient in Chile

    NASA Astrophysics Data System (ADS)

    Doetterl, Sebastian; Munoz, Cristina; Boeckx, Pascal; Zagal Venegas, Erick

    2016-04-01

    Grasslands are recognized for having a high C sequestration potential and to play an important role in the development of sustainable agriculture in a warming world. Soil organic carbon (SOC) decomposition, and the resultant CO2 emissions, can have a significant impact on atmospheric CO2 levels. However, at a global scale, the temperature sensitivity of C decomposition is not addressed spatially explicit and, hence, introduces large uncertainty into global assessments of future C release from soils. Furthermore, temperature sensitivity is not only a question of climatic and biochemical recalcitrance of SOC, but also crucially dependent on the soil environment in which decomposition takes place. Hence, it is crucial to study SOC decomposition across a large variety of environmental conditions in order to improve the prediction of long-term impacts of global warming on SOC storage. Chile provides one of the best natural laboratories in the world to assess the links between soils, climate and carbon dynamics as both climate and mineralogical parameters show large variability. Here, we show the first results from a one-year temperature sensitive incubation study on soil samples from 37 grassland sites across a 4000km North-South gradient in Chile. Incubation was performed at 5 different temperature levels and we analyze the variability of temperature sensitivity of decomposition in relation to C input quality, soil geochemistry and climatic conditions at the sampling sites.

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

    NASA Astrophysics Data System (ADS)

    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 < ±0.05 m/d) to ±1.0 m/d, while the vertical hydraulic gradients were within the range of -0.2 to 0.15 m/m. The highest and most variable fluxes occurred adjacent to a debris-dam and bridge pier. This phenomenon is very likely

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

    NASA Astrophysics Data System (ADS)

    Taniguchi, Yusuke; Kanaya, Kazuyuki; Suzuki, Hiroshi; Umeda, Takashi; WHOT-QCD Collaboration

    2017-03-01

    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 nonperturbatively O (a ) -improved Wilson quarks, we perform simulations on a fine lattice with a ≃0.07 fm at a heavy u , d quark mass with mπ/mρ≃0.63 , but approximately physical s quark mass with mηss/mϕ≃0.74 . In a temperature range from T ≃174 MeV (Nt=16 ) to 697 MeV (Nt=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 the two definitions with Wilson quarks. The other is a comparison with a prediction of the dilute instanton gas approximation, which is relevant in a study of axions as a candidate of the dark matter in the evolution of the Universe. We find that the topological susceptibility shows a decrease in T which is consistent with the predicted χt(T )∝(T /Tpc)-8 for three-flavor QCD even at low temperature Tpc

  6. Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

    SciTech Connect

    Gerashchenko, Sergiy; Livescu, Daniel

    2016-07-28

    Here we studied the growth rate of the compressible Rayleigh-Taylor instability in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. An analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ=0. Compared to Θ=0 case, the role of Θ<0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ>0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ<0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.

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

    SciTech Connect

    Mills, Sean M.; Abbot, Dorian S.

    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.

  8. Reduction of lateritic iron ore briquette using coal bed reductant by isothermal - temperature gradient method

    NASA Astrophysics Data System (ADS)

    Zulhan, Zulfiadi; Himawan, David Mangatur; Dimyati, Arbi

    2017-01-01

    In this study, isothermal-temperature gradient method was used to separate iron and alumina in lateritic iron ore as an alternative technique. The lateritic iron ore was ground to obtain grain size of less than 200 mesh and agglomerated in the form of cylindrical briquette using a press machine. The iron oxide in the briquette was reduced by addition of coal so that all surface of the briquette was covered by the coal. The temperature profile for the reduction process of the briquette was divided into three stages: the first stage was isothermal at 1000°C, the second stage was temperature gradient at varies heating rate of 5, 6.67 and 8.33°C/minutes from 1000 to 1400°C, and the final stage was isothermal at 1400°C. The effect of dehydroxylation of lateritic iron ore was studied as well. Aluminum distribution inside and outside the briquette was analyzed by scanning electron microscope with energy dispersive spectroscopy (SEM-EDS). The analysis results showed that the aluminum content increased from 8.01% at the outside of the briquette to 13.12% in the inside of the briquette. On contrary, iron content is higher at the outside of the briquette compared to that in the inside. These phenomena indicated that aluminum tends to migrate into the center of the briquette while iron moves outward to the surface of briquette. Furthermore, iron metallization of 91.03% could be achieved in the case of without dehydroxylation treatment. With the dehydroxylation treatment, iron metallization degree was increased up to 95.27%.

  9. Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

    NASA Astrophysics Data System (ADS)

    Gerashchenko, S.; Livescu, D.

    2016-07-01

    The growth rate of the compressible Rayleigh-Taylor instability is studied in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. An analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ = 0. Compared to Θ = 0 case, the role of Θ < 0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ > 0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ < 0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.

  10. Viscous effects on the Rayleigh-Taylor instability with background temperature gradient

    DOE PAGES

    Gerashchenko, Sergiy; Livescu, Daniel

    2016-07-28

    Here we studied the growth rate of the compressible Rayleigh-Taylor instability in the presence of a background temperature gradient, Θ, using a normal mode analysis. The effect of Θ variation is examined for three interface types corresponding to the combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous, and viscous-inviscid) at different Atwood numbers, At, and when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. Anmore » analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of large Θ. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and Θ=0. Compared to Θ=0 case, the role of Θ<0 (hotter light fluid) is destabilizing and becomes stabilizing when Θ>0 (colder light fluid). The most pronounced effect of Θ ≠ 0 is found at low At and/or at large perturbation wavelengths relative to the domain size for all interface types. On the other hand, at small perturbation wavelengths relative to the domain size, the growth rate for the Θ<0 case exceeds the infinite domain incompressible constant density result. The results are applied to two practical examples, using sets of parameters relevant to Inertial Confinement Fusion coasting stage and solar corona plumes. The role of viscosity on the growth rate reduction is discussed together with highlighting the range of wavenumbers most affected by viscosity. The viscous effects further increase in the presence of background temperature gradient, when the viscosity is temperature dependent.« less

  11. Movement of Five Nematode Species through Sand Subjected to Natural Temperature Gradient Fluctuations

    PubMed Central

    Robinson, A. F.

    1994-01-01

    Temperature gradient fluctuations that occur naturally as a result of heating and cooling of the soil surface were reproduced within 15-cm-d, 15-cm-long acrylic tubes filled with moist sand. Sunny and rainy periods during the late summer in eastern Texas were simulated. Five ecologically different nematode species were adapted to fluctuating temperatures for 20-36 hours at a simulated depth of 12.5 cm before being injected simultaneously into the centers of tubes at that depth. When heat waves were propagated horizontally to eliminate gravitational effects, the movement of Ditylenchus phyllobius, Steinernema glaseri, and Heterorhabditis bacteriophora relative to the thermal surface was rapid and largely random. However, Rotylenchulus reniformis moved away from and Meloidogyne incognita moved toward the thermal surface. When heat waves were propagated upward or downward, responses to temperature were the same as when propagated horizontally, irrespective of gravity. The initial direction of movement 1.5 hours after introduction to 20-era-long tubes at five depths at five intervals within a 24-hour cycle indicated that M. incognita moved away from and R. reniformis moved toward the temperature to which last exposed. Differences in movement of the five species tested relative to gravity appeared related to body length, with the smallest nematodes moving downward and the largest moving upward. PMID:19279868

  12. Elevational Ranges of Birds on a Tropical Montane Gradient Lag behind Warming Temperatures

    PubMed Central

    Forero-Medina, German; Terborgh, John; Socolar, S. Jacob; Pimm, Stuart L.

    2011-01-01

    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. PMID:22163309

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

    PubMed

    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.

  14. Compressed exponential decays in correlation experiments: The influence of temperature gradients and convection

    NASA Astrophysics Data System (ADS)

    Gabriel, Jan; Blochowicz, Thomas; Stühn, Bernd

    2015-03-01

    In a wide range of soft materials, correlation experiments using laser light or partially coherent X-rays report the so called compressed exponential correlation functions, i. e., decays c(t) ∝ exp(-(t/τ)β) with β > 1. In many cases, this is related to the relaxation of inner stresses, but in some systems, the source of such a phenomenon is still poorly understood. We performed multi speckle-dynamic light scattering experiments in a system of polystyrene spheres in supercooled propanediol. At low temperatures, compressed exponential decays are observed in a multispeckle experiment, in agreement with the literature findings in similar systems. At the same time, due to the particular geometry of our setup, the speckle pattern shows indication for convection in the sample due to a slight temperature gradient across the sample cuvette mounted in a cold finger cryostat. These effects increase with decreasing temperature and after a temperature jump. In some cases it can be corrected for by assuming convective flow at constant velocity. Such corrections reduce or remove compressed exponential behavior in our experiment.

  15. Autoignition: Modes of reaction front propagation evolving from hot spots with defined temperature gradients

    NASA Astrophysics Data System (ADS)

    Kassoy, David R.

    2014-11-01

    An asymptotic mathematical model, based on the compressible reactive, conservation equations, including transport terms and an arbitrary energy source, is used to quantify the thermo-mechanical consequences of an imposed temperature gradient, ΔT/ l. The mathematical model explains the physics of the gradient system in terms of the local conduction time l2/(kappa), where kappa is the characteristic thermal diffusivity, the local acoustic time l/a0, where a0 is the characteristic acoustic time scale, the characteristic time scale of energy deposition from the source, tds, and the characteristic energy deposition into and through the gradient region on that time scale. The primary objectives are to predict the magnitude of the induced gas motion and determine when and if transport effects are important. The methodology, related to that in several earlier studies [1--5], can be used to distinguish between detonation and deflagration initiation as well as spontaneous reaction wave propagation. This analysis will help to explain the somewhat enigmatic results in Refs. 6-8. 1,2. Clarke, J.F, Kassoy, D.R. and Riley, N. (1984) Proc. Roy. Soc. A393, 309-351; 3. Kassoy, D.R. (2010), J. Eng Math, 68, 249-262. Kassoy, D.R. (2013), CTM, 18, 101-116. Kassoy, D.R. (2014), AIAA J., doi10.2514, /1J052807. Zeldovich, Y.B. (1980), Combust. Flame, 39, 211-214. Gu, X.J., Emerson, D.R., Bradley, D. (2003), Comb. Flame, 133, 63-74. Sankaran, R., Hong, G. Hawkes, E.R. Chen J. H., (2005) Proc. Combustion Inst., 30, 875-882.

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

    PubMed

    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, p<0.05). At the half-way point and finish, the core to skin 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, p<0.05). Sweat rate was lower in the 18 °C group compared to the 26 °C, 34 °C, and 42 °C groups, 3.6±1.3 vs. 7.2±3.0, 7.1±2.0, and 7.6±1.7 g m(-2) min(-1), respectively, p<0.05. There were no group differences in core temperature 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

  17. Ion-temperature-gradient sensitivity of the hydrodynamic instability caused by shear in the magnetic-field-aligned plasma flow

    SciTech Connect

    Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June; Koepke, M. E.

    2014-07-15

    The cross-magnetic-field (i.e., perpendicular) profile of ion temperature and the perpendicular profile of the magnetic-field-aligned (parallel) plasma flow are sometimes inhomogeneous for space and laboratory plasma. Instability caused either by a gradient in the ion-temperature profile or by shear in the parallel flow has been discussed extensively in the literature. In this paper, (1) hydrodynamic plasma stability is investigated, (2) real and imaginary frequency are quantified over a range of the shear parameter, the normalized wavenumber, and the ratio of density-gradient and ion-temperature-gradient scale lengths, and (3) the role of inverse Landau damping is illustrated for the case of combined ion-temperature gradient and parallel-flow shear. We find that increasing the ion-temperature gradient reduces the instability threshold for the hydrodynamic parallel-flow shear instability, also known as the parallel Kelvin-Helmholtz instability or the D'Angelo instability. We also find that a kinetic instability arises from the coupled, reinforcing action of both free-energy sources. For the case of comparable electron and ion temperature, we illustrate analytically the transition of the D'Angelo instability to the kinetic instability as (a) the shear parameter, (b) the normalized wavenumber, and (c) the ratio of density-gradient and ion-temperature-gradient scale lengths are varied and we attribute the changes in stability to changes in the amount of inverse ion Landau damping. We show that near a normalized wavenumber k{sub ⊥}ρ{sub i} of order unity (i) the real and imaginary values of frequency become comparable and (ii) the imaginary frequency, i.e., the growth rate, peaks.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Mode signature and stability for a Hamiltonian model of electron temperature gradient turbulence

    SciTech Connect

    Tassi, E.; Morrison, P. J.

    2011-03-15

    Stability properties and mode signature for equilibria of a model of electron temperature gradient (ETG) driven turbulence are investigated by Hamiltonian techniques. After deriving new infinite families of Casimir invariants, associated with the noncanonical Poisson bracket of the model, a sufficient condition for stability is obtained by means of the Energy-Casimir method. Mode signature is then investigated for linear motions about homogeneous equilibria. Depending on the sign of the equilibrium 'translated' pressure gradient, stable equilibria can either be energy stable, i.e., possess definite linearized perturbation energy (Hamiltonian), or spectrally stable with the existence of negative energy modes. The ETG instability is then shown to arise through a Krein-type bifurcation, due to the merging of a positive and a negative energy mode, corresponding to two modified drift waves admitted by the system. The Hamiltonian of the linearized system is then explicitly transformed into normal form, which unambiguously defines mode signature. In particular, the fast mode turns out to always be a positive energy mode, whereas the energy of the slow mode can have either positive or negative sign. A reduced model with stable equilibria shear flow that possess a continuous spectrum is also analyzed and brought to normal form by a special integral transform. In this way it is seen how continuous spectra can have signature as well.

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

    PubMed Central

    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

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

    SciTech Connect

    Rosenfeld, Katherine A.; Andrews, Sean M.; Wilner, David J.; Qi, Chunhua; Hughes, A. Meredith

    2013-09-01

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

  2. Ecological impacts of invasive alien species along temperature gradients: testing the role of environmental matching.

    PubMed

    Iacarella, Josephine C; Dick, Jaimie T A; Alexander, Mhairi E; Ricciardi, Anthony

    2015-04-01

    Invasive alien species (IAS) can cause substantive ecological impacts, and the role of temperature in mediating these impacts may become increasingly significant in a changing climate. Habitat conditions and physiological optima offer predictive information for IAS impacts in novel environments. Here, using meta-analysis and laboratory experiments, we tested the hypothesis that the impacts of IAS in the field are inversely correlated with the difference in their ambient and optimal temperatures. A meta-analysis of 29 studies of consumptive impacts of IAS in inland waters revealed that the impacts of fishes and crustaceans are higher at temperatures that more closely match their thermal growth optima. In particular, the maximum impact potential was constrained by increased differences between ambient and optimal temperatures, as indicated by the steeper slope of a quantile regression on the upper 25th percentile of impact data compared to that of a weighted linear regression on all data with measured variances. We complemented this study with an experimental analysis of the functional response (the relationship between predation rate and prey supply) of two invasive predators (freshwater mysid shrimp, Hemimysis anomala and Mysis diluviana) across. relevant temperature gradients; both of these species have previously been found to exert strong community-level impacts that are corroborated by their functional responses to different prey items. The functional response experiments showed that maximum feeding rates of H. anomala and M. diluviana have distinct peaks near their respective thermal optima. Although variation in impacts may be caused by numerous abiotic or biotic habitat characteristics, both our analyses point to temperature as a key mediator of IAS impact levels in inland waters and suggest that IAS management should prioritize habitats in the invaded range that more closely match the thermal optima of targeted invaders.

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

    PubMed

    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

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

    PubMed Central

    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

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

    PubMed

    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

  6. Multi-water-bag models of ion temperature gradient instability in cylindrical geometry

    SciTech Connect

    Coulette, David; Besse, Nicolas

    2013-05-15

    Ion temperature gradient instabilities play a major role in the understanding of anomalous transport in core fusion plasmas. In the considered cylindrical geometry, ion dynamics is described using a drift-kinetic multi-water-bag model for the parallel velocity dependency of the ion distribution function. In a first stage, global linear stability analysis is performed. From the obtained normal modes, parametric dependencies of the main spectral characteristics of the instability are then examined. Comparison of the multi-water-bag results with a reference continuous Maxwellian case allows us to evaluate the effects of discrete parallel velocity sampling induced by the Multi-Water-Bag model. Differences between the global model and local models considered in previous works are discussed. Using results from linear, quasilinear, and nonlinear numerical simulations, an analysis of the first stage saturation dynamics of the instability is proposed, where the divergence between the three models is examined.

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

    NASA Astrophysics Data System (ADS)

    Guo, Weixin; Wang, Lu; Zhuang, Ge

    2016-11-01

    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 the 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 the 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 of trace high-Z W get stronger with stronger magnetic shear.

  8. Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

    NASA Technical Reports Server (NTRS)

    Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

    2014-01-01

    Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

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

    SciTech Connect

    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.

  10. Generation of transverse waves in a liquid layer with insoluble surfactant subjected to temperature gradient

    NASA Astrophysics Data System (ADS)

    Mikishev, Alexander B.; Friedman, Barry A.; Nepomnyashchy, Alexander A.

    2016-12-01

    The formation of Faraday waves (FWs) at the surfactant-covered free surface of a vertically vibrated liquid layer is considered. The layer is subjected to a vertical temperature gradient. The surfactant is insoluble. Linear stability analysis and the Floquet method are used for disturbances with arbitrary wave numbers to find the regions of critical vibration amplitude where FWs are generated. The problem is considered for the semi-infinite liquid layer, as well as for the layer of a finite depth. It is shown numerically, that in the semi-infinite case the critical tongue of a neutral stability curve corresponding to the lowest value of the forcing amplitude is related to the subharmonic instability mode. It changes to the harmonic one in the case of finite depth. The influence of thermocapillary Marangoni number on the critical amplitude of FWs is studied. The growth of that number stabilizes the system, however, this effect is very weak.

  11. Kinetic analysis of the ion temperature gradient modes in toroidally rotating plasmas

    SciTech Connect

    Zheng, L.; Tessarotto, M.

    1996-12-01

    With the two time scale feature revealed, an analytical method is developed to solve the combined eigenvalue and initial value problem describing the ion temperature gradient (ITG) modes in the toroidally rotating plasmas. With full gyrokinetics and toroidal geometry effects being taken into account in an ordering consistent manner, dispersion relations are obtained for ITG modes both of toroidal and slab-like branches. The results show that the sonic rotation can be harmful for the stability, while subsonic rotation with flow shear can be expected to be stabilizing. The existence of the flow shear leads the time evolution of the fluctuation signals to display two different time scales{emdash}a fast oscillating (either fast or slow growing) signal with its amplitude modulated by a slowly varying envelope, resembling fishbone-like fluctuations. {copyright} {ital 1996 American Institute of Physics.}

  12. Near-Field Radiative Heat Transfer under Temperature Gradients and Conductive Transfer

    NASA Astrophysics Data System (ADS)

    Jin, Weiliang; Messina, Riccardo; Rodriguez, Alejandro W.

    2017-02-01

    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.

  13. A self-organized criticality model for ion temperature gradient mode driven turbulence in confined plasma

    SciTech Connect

    Isliker, H.; Pisokas, Th.; Vlahos, L.; Strintzi, D.

    2010-08-15

    A new self-organized criticality (SOC) model is introduced in the form of a cellular automaton (CA) for ion temperature gradient (ITG) mode driven turbulence in fusion plasmas. Main characteristics of the model are that it is constructed in terms of the actual physical variable, the ion temperature, and that the temporal evolution of the CA, which necessarily is in the form of rules, mimics actual physical processes as they are considered to be active in the system, i.e., a heating process and a local diffusive process that sets on if a threshold in the normalized ITG R/L{sub T} is exceeded. The model reaches the SOC state and yields ion temperature profiles of exponential shape, which exhibit very high stiffness, in that they basically are independent of the loading pattern applied. This implies that there is anomalous heat transport present in the system, despite the fact that diffusion at the local level is imposed to be of a normal kind. The distributions of the heat fluxes in the system and of the heat out-fluxes are of power-law shape. The basic properties of the model are in good qualitative agreement with experimental results.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Tightly linked oceanic meridional and zonal temperature gradients - a fundamental climate constraint for the Miocene, Pliocene and other epochs

    NASA Astrophysics Data System (ADS)

    Fedorov, A. V.; Burls, N.; Lawrence, K. T.; Peterson, L.

    2015-12-01

    Two major characteristics define the mean climate of the tropics - pronounced zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature (SST). These gradients control the atmospheric zonal and meridional circulations and thus Earth's climate. Previous studies have shown that global cooling, which started in the late Miocene and accelerated since the early Pliocene, was accompanied by the gradual strengthening of these gradients. Here, we carefully analyze temperature trends over the past 5 million years, including a newly generated SST record from the Southern Pacific Ocean (ODP site 1125), and show that changes in these gradients followed each other very closely, reflecting a tight relationship between these two climatic variables. To investigate this relationship we conduct simulations with a comprehensive climate model (CESM) wherein we systematically reduce the meridional temperature gradient by modifying the latitudinal distribution of cloud albedo or atmospheric CO2 concentrations. We find that the zonal SST gradient in the Pacific adjusts accordingly, such that changes along the equator match the imposed changes in the meridional gradient, with the two variables linked by upper-ocean circulation. The meridional temperature distribution is mapped onto the ocean vertical thermal stratification and then onto the east-west SST distribution along the equator. These findings are accounted for by a simple model of tropical climate informed by our simulations. Consequently, the tight relationship between the two SST gradients posits a fundamental constraint on past climates that can help resolve current debates on the state of the tropics during the early Pliocene, including the prevalence of permanent El Nino-like conditions (El Padre).

  16. Redox systematics of a magma ocean with variable pressure-temperature gradients and composition

    PubMed Central

    Righter, K.; Ghiorso, M. S.

    2012-01-01

    Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO2), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO2 that is based on the ratio of Fe and FeO [called “ΔIW (ratio)” hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO2 + O2 = Fe2SiO4 to calculate absolute fO2 and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO2 in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO2 may evolve from high to low fO2 during Earth (and other differentiated bodies) accretion. Any modeling of

  17. Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.

    PubMed

    Righter, K; Ghiorso, M S

    2012-07-24

    Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO(2) that is based on the ratio of Fe and FeO [called "ΔIW (ratio)" hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO(2) + O(2) = Fe(2)SiO(4) to calculate absolute fO(2) and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO(2) in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO(2) may evolve from high to low fO(2) during Earth (and other differentiated bodies) accretion. Any

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

    PubMed Central

    Fuchiwaki, Yusuke; Nagai, Hidenori

    2014-01-01

    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. PMID:25350508

  19. Study of a liquid plug-flow thermal cycling technique using a temperature gradient-based actuator.

    PubMed

    Fuchiwaki, Yusuke; Nagai, Hidenori

    2014-10-27

    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.

  20. Energy efficiency of a concentration gradient flow battery at elevated temperatures

    NASA Astrophysics Data System (ADS)

    van Egmond, W. J.; Starke, U. K.; Saakes, M.; Buisman, C. J. N.; Hamelers, H. V. M.

    2017-02-01

    Fast growth of intermittent renewable energy generation introduces a need for large scale electricity storage. The Concentration Gradient Flow Battery (CGFB) is an emerging technology which combines Electrodialysis with Reverse Electrodialysis into a flow battery which is able to safely store very large amounts of energy in environmental friendly NaCl solutions. In this work, (dis)charge efficiency, energy density and power density are both theoretically and experimentally investigated. Fifteen constant current experiments (-47.5 to +37.5 A m-2) are performed at 40 °C and two experiments (-32.5 and 15 A m-2) at 10 and 25 °C. The magnitudes of the three main energy dissipation sources (internal resistance, water transport and co-ion transport) are measured and mitigation strategies are proposed. The effect of current density, state of charge and temperature on the dissipation sources is analysed. Water transport is shown to cause hysteresis, lower (dis)charge efficiencies and lower energy capacity. At constant current and with increasing temperature, internal resistance is reduced but unwanted water transport is increased. This study reports charge efficiencies up to 58% and discharge efficiencies up to 72%. Full charge or discharge of the battery is shown inefficient. The optimal operating range is therefore introduced and identified (concentration difference Δm > 0.5 and energy efficiency η > 0.4).

  1. The doubled CO2 climate - Impact of the sea surface temperature gradient

    NASA Technical Reports Server (NTRS)

    Rind, David

    1987-01-01

    The Goddard Institute for Space Studies (GISS) GCM of Hansen et al. (1983) was run, with 4 deg x 5 deg resolution, with doubled CO2 and two sets of sea surface temperature gradient distributions. One set was derived from the equilibrium doubled CO2 run of the 8 deg x 10 deg GISS GCM, with minimal high latitude amplification. The other set resembled closely the GFDL model results, with greater amplification. Both experiments had the same global mean surface air temperature change. The two experiments were often found to produce substantially different climate characteristics. With reduced high latitude amplification (set one), and thus, more equatorial warming, there was a greater increase in specific humidity and the greenhouse capacity of the atmosphere, resulting in a warmer atmosphere in general. Features such as the low-latitude precipitation, Hadley cell intensity, jet stream magnitude, and atmospheric energy transports all increased in comparison with the control run. In contrast, these features all decreased in the experiment with greater high latitude amplification (set two).

  2. Predictive simulations of tokamak plasmas with a model for ion-temperature-gradient-driven turbulence

    SciTech Connect

    Redd, A.J.; Kritz, A.H.; Bateman, G.; Horton, W.

    1998-05-01

    A drift wave transport model, recently developed by Ottaviani, Horton and Erba (OHE) [Ottaviani {ital et al.}, Plasma Phys. Controlled Fusion {bold 39}, 1461 (1997)], has been implemented and tested in a time-dependent predictive transport code. This OHE model assumes that anomalous transport is due to turbulence driven by ion temperature gradients and that the fully developed turbulence will extend into linearly stable regions, as described in the reference cited above. A multiplicative elongation factor is introduced in the OHE model and simulations are carried out for 12 discharges from major tokamak experiments, including both L- and H-modes (low- and high-confinement modes) and both circular and elongated discharges. Good agreement is found between the OHE model predictions and experiment. This OHE model is also used to describe the performance of the International Thermonuclear Experimental Reactor (ITER) [Putvinski {ital et al.}, in {ital Proceedings of the 16th IAEA Fusion Energy Conference}, Montr{acute e}al, Canada, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 2, p. 737.] A second version of the OHE model, in which the turbulent transport is not allowed to penetrate into linearly stable regions, has also been implemented and tested. In simulations utilizing this version of the model, the linear stability of the plasma core eliminates the anomalous thermal transport near the magnetic axis, resulting in an increase in the core temperatures to well above the experimental values. {copyright} {ital 1998 American Institute of Physics.}

  3. Determination of stratospheric temperature and height gradients from nimbus 3 radiation data

    NASA Technical Reports Server (NTRS)

    Nicholas, G. W.; Hovland, D. N.; Belmont, A. D.

    1971-01-01

    To improve the specification of stratospheric horizontal temperature and geopotential height fields from satellite radiation data, needed for high flying aircraft, a technique was derived to estimate data between satellite tracks using interpolated IRIS 15-micron data from Nimbus III. The interpolation is based on the observed gradients of the MRIR 15-micron radiances between subsatellite tracks. The technique was verified with radiosonde data taken within 6 hours of the satellite data. The sample varied from 1126 pairs at low levels to 383 pairs at 10 mb using northern hemisphere data for June 15 to July 20, 1969. The data were separated into five latitude bands. The Rms temperature differences were generally from 2 to 5 C for all levels above 300 mb. From 500 to 300 mb RMS differences vary from 4 to 9C except at high latitudes which show values near 3C. The RMS differences between radiosonde heights and those calculated hydrostatically from the surface were from 30 to 280 meters increasing from the surface to 10 mb. Integration starting at 100 mb reduced the RMS difference in the stratosphere to 20 to 120 meters from 70 to 10 mb. From a comparison with actual operational maps at 50 and 10 mb, it appears the techniques developed produce analyses in general agreement with those from radiosonde data. In addition, they are able to indicate details over areas of sparse data not shown by conventional techniques.

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

    PubMed

    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.

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

    PubMed Central

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

    2016-01-01

    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 (14C-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. PMID:26924084

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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 (14C-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.

  7. Collisionless microinstabilities in stellarators. III. The ion-temperature-gradient mode

    SciTech Connect

    Plunk, G. G. Helander, P.; Xanthopoulos, P.

    2014-03-15

    We investigate the linear theory of the ion-temperature-gradient (ITG) mode, with the goal of developing a general understanding that may be applied to stellarators. We highlight the Wendelstein 7X (W7-X) device. Simple fluid and kinetic models that follow closely from existing literature are reviewed and two new first-principle models are presented and compared with results from direct numerical simulation. One model investigates the effect of regions of strong localized shear, which are generic to stellarator equilibria. These “shear spikes” are found to have a potentially significant stabilizing affect on the mode; however, the effect is strongest at short wavelengths perpendicular to the magnetic field, and it is found to be significant only for the fastest growing modes in W7-X. A second model investigates the long-wavelength limit for the case of negligible global magnetic shear. The analytic calculation reveals that the effect of the curvature drive enters at second order in the drift frequency, confirming conventional wisdom that the ITG mode is slab-like at long wavelengths. Using flux tube simulations of a zero-shear W7-X configuration, we observe a close relationship to an axisymmetric configuration at a similar parameter point. It is concluded that scale lengths of the equilibrium gradients constitute a good parameter space to characterize the ITG mode. Thus, to optimize the magnetic geometry for ITG mode stability, it may be fruitful to focus on local parameters, such as the magnitude of bad curvature, connection length, and local shear at locations of bad curvature (where the ITG mode amplitude peaks)

  8. Visualization of turbulent wedges under favorable pressure gradients using shear-sensitive and temperature-sensitive liquid crystals.

    PubMed

    Chong, Tze-Pei; Zhong, Shan; Hodson, Howard P

    2002-10-01

    Turbulent wedges induced by a three-dimensional surface roughness placed on a flat plate were studied using both shear sensitive and temperature sensitive liquid crystals, respectively denoted by SSLC and TSLC. The experiments were carried out at a free-stream velocity of 28 m/sec at three different favorable pressure gradients. The purpose of this investigation was to examine the spreading angles of the turbulent wedges, as indicated by their associated surface shear stresses and heat transfer characteristics, and to obtain more insight about the behavior of transitional momentum and thermal boundary layers when a streamwise pressure gradient exists. It was shown that under a zero pressure gradient the spreading angles indicated by the two types of liquid crystals are the same, but the difference increases as the level of the favorable pressure gradient increases. The result from the present study is important for modelling the transition of thermal boundary layers over gas turbine blades.

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

    NASA Astrophysics Data System (ADS)

    Jiao, Chengru; Zheng, Liancun; Ma, Lianxi

    2015-08-01

    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.

  10. Lateral solidification of a liquid crystalline semiconductor film induced by temperature gradient

    NASA Astrophysics Data System (ADS)

    Hoshino, Tomoya; Ito, Hayato; Fujieda, Ichiro; Hanasaki, Tomonori

    2013-09-01

    Derivatives of [1]benzothieno[3,2-b]benzothiophene (BTBT) are attracting much attention as a highly soluble, highmobility semiconductor material for thin-film transistor applications. These small molecules are known to organize themselves into a single crystalline structure after spin coating or drop casting. Charge transport in a single crystal material is anisotropic in nature. Hence, it is desired to control its orientation during growth or recrystallization so that the source and drain electrodes of a transistor are to be placed along a faster transport direction. We propose to generate temperature gradient in a heated liquid crystalline thin film to induce lateral recrystallization. In experiment, we tried two methods. First, an aluminum plate with two narrow ridges was inserted between a temperature-controlled stage and a square silicon substrate with a 200nm-thick SiO2 and a spin-coated C8-BTBT film. We raised the temperature of the stage to 120oC and let it cool gradually. During cooling at around 105oC , the color of the sample started to change, indicating a phase change. This change proceeded from the corners of the film and in about 30 seconds, darker regions merged at the center of the substrate. Second, the sample was placed at the edge of the stage. In this case, the color change started from the protruding corner of the sample and proceeded toward the other end. Micrograph observation revealed that cracks were formed in these films and they were perpendicular to the direction of the phase change.

  11. Reproductive output of a non-zooxanthellate temperate coral is unaffected by temperature along an extended latitudinal gradient.

    PubMed

    Airi, Valentina; Prantoni, Selena; Calegari, Marco; Lisini Baldi, Veronica; Gizzi, Francesca; Marchini, Chiara; Levy, Oren; Falini, Giuseppe; Dubinsky, Zvy; Goffredo, Stefano

    2017-01-01

    Global environmental change, in marine ecosystems, is associated with concurrent shifts in water temperature, circulation, stratification, and nutrient input, with potentially wide-ranging biological effects. Variations in seawater temperature might alter physiological functioning, reproductive efficiency, and demographic traits of marine organisms, leading to shifts in population size and abundance. Differences in temperature tolerances between organisms can identify individual and ecological characteristics, which make corals able to persist and adapt in a climate change context. Here we investigated the possible effect of temperature on the reproductive output of the solitary non-zooxanthellate temperate coral Leptopsammia pruvoti, along an 8° latitudinal gradient. Samples have been collected in six populations along the gradient and each polyp was examined using histological and cyto-histometric analyses. We coupled our results with previous studies on the growth, demography, and calcification of L. pruvoti along the same temperature gradient, and compared them with those of another sympatric zooxanthellate coral Balanophyllia europaea to understand which trophic strategy makes the coral more tolerant to increasing temperature. The non-zooxanthellate species seemed to be quite tolerant to temperature increases, probably due to the lack of the symbiosis with zooxanthellae. To our knowledge, this is the first field investigation of the relationship between reproductive output and temperature increase of a temperate asymbiotic coral, providing novel insights into the poorly studied non-zooxanthellate scleractinians.

  12. Reproductive output of a non-zooxanthellate temperate coral is unaffected by temperature along an extended latitudinal gradient

    PubMed Central

    Airi, Valentina; Prantoni, Selena; Calegari, Marco; Lisini Baldi, Veronica; Gizzi, Francesca; Marchini, Chiara; Levy, Oren; Falini, Giuseppe; Dubinsky, Zvy; Goffredo, Stefano

    2017-01-01

    Global environmental change, in marine ecosystems, is associated with concurrent shifts in water temperature, circulation, stratification, and nutrient input, with potentially wide-ranging biological effects. Variations in seawater temperature might alter physiological functioning, reproductive efficiency, and demographic traits of marine organisms, leading to shifts in population size and abundance. Differences in temperature tolerances between organisms can identify individual and ecological characteristics, which make corals able to persist and adapt in a climate change context. Here we investigated the possible effect of temperature on the reproductive output of the solitary non-zooxanthellate temperate coral Leptopsammia pruvoti, along an 8° latitudinal gradient. Samples have been collected in six populations along the gradient and each polyp was examined using histological and cyto-histometric analyses. We coupled our results with previous studies on the growth, demography, and calcification of L. pruvoti along the same temperature gradient, and compared them with those of another sympatric zooxanthellate coral Balanophyllia europaea to understand which trophic strategy makes the coral more tolerant to increasing temperature. The non-zooxanthellate species seemed to be quite tolerant to temperature increases, probably due to the lack of the symbiosis with zooxanthellae. To our knowledge, this is the first field investigation of the relationship between reproductive output and temperature increase of a temperate asymbiotic coral, providing novel insights into the poorly studied non-zooxanthellate scleractinians. PMID:28158213

  13. The temperature gradient-forming device, an accessory unit for normal light microscopes to study the biology of hyperthermophilic microorganisms.

    PubMed

    Mora, Maximilian; Bellack, Annett; Ugele, Matthias; Hopf, Johann; Wirth, Reinhard

    2014-08-01

    To date, the behavior of hyperthermophilic microorganisms in their biotope has been studied only to a limited degree; this is especially true for motility. One reason for this lack of knowledge is the requirement for high-temperature microscopy-combined, in most cases, with the need for observations under strictly anaerobic conditions-for such studies. We have developed a custom-made, low-budget device that, for the first time, allows analyses in temperature gradients up to 40°C over a distance of just 2 cm (a biotope-relevant distance) with heating rates up to ∼5°C/s. Our temperature gradient-forming device can convert any upright light microscope into one that works at temperatures as high as 110°C. Data obtained by use of this apparatus show how very well hyperthermophiles are adapted to their biotope: they can react within seconds to elevated temperatures by starting motility-even after 9 months of storage in the cold. Using the temperature gradient-forming device, we determined the temperature ranges for swimming, and the swimming speeds, of 15 selected species of the genus Thermococcus within a few months, related these findings to the presence of cell surface appendages, and obtained the first evidence for thermotaxis in Archaea.

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

    PubMed Central

    Lakeman-Fraser, Poppy; Ewers, Robert M.

    2014-01-01

    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. PMID:24898374

  15. Shear flow instabilities induced by trapped ion modes in collisionless temperature gradient turbulence

    SciTech Connect

    Palermo, F.; Garbet, X.; Cartier-Michaud, T.; Ghendrih, P.; Grandgirard, V.; Sarazin, Y.; Ghizzo, A.

    2015-04-15

    One important issue in turbulence self-organization is the interplay between the Kelvin–Helmholtz (KH) instability and streamers and/or zonal flows. This question has been debated for a long time. The effects of the KH instability and its position in the sequence of events between streamers, turbulence, and zonal flows have been investigated with a reduced gyro-bounce averaged kinetic code devoted to study the primary ion temperature gradient (ITG) instability linked to trapped ion modes (TIM). In toroidal geometry, the specific dynamics of TIM linked to trapped particles becomes important when the frequency of ITG modes falls below the ion bounce frequency, allowing one to average on both the cyclotron and bounce motion fast time scales. This reduction of the number of degrees of freedom leads to a strong reduction of computer resources (memory and computation time). Bounce-averaged gyrokinetic code can be considered as a toy model able to describe basic structures of turbulent transport in tokamak devices. In particular, by means of this code, we have observed that the energy injected in the system by the TIM instability is exchanged between streamers and zonal flows by means of KH vortices that grow along these structures in the nonlinear phase. The energy transfer occurs throughout the relaxation phase of the streamer growth leading to a modification of the KH modes and to the generation of the zonal flows.

  16. Integral eigenmode analysis of shear flow effects on the ion temperature gradient mode

    SciTech Connect

    Artun, M.; Reynders, J.V.M.; Tang, W.M.

    1993-07-01

    Previous numerical and analytic kinetic studies have investigated the influence of velocity shear on the ion temperature gradient (ITG) mode. These studies relied on a differential approximation to study mode structures with k{sub {perpendicular}}{rho}{sub i} {much_lt} 1. A recently developed gyrokinetic integral code is here used to explore the effects of sheared flows on the ITG mode for arbitrary values of k{sub {perpendicular}}{rho}{sub i}. It is found that both the mode structure and eigenfrequencies predicted by the integral code can differ from the results obtained by the differential approach, even in the k{sub y}{rho}{sub i} {much_lt} 1 limit. Although some trends predicted by the differential approximation are recovered by the integral approach, there are some significant differences. For example, the slight destabilizing effect observed for small values of the perpendicular velocity shear at k{sub {perpendicular}}{rho}{sub i} {much_lt} 1 is amplified when the integral approach is applied. In dealing with the higher radial eigenmodes, which can often exhibit the largest growth rates, it is emphasized that their finer radial structure usually dictates that the integral equation analysis is required. Results from the integral code are presented together with comparisons with results from the differential approach.

  17. Bioinspired large-scale aligned porous materials assembled with dual temperature gradients

    PubMed Central

    Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P.; Ritchie, Robert O.

    2015-01-01

    Natural materials, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being porous and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight materials. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, porous, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural materials, in particular advanced materials such as composites, where a higher level of control over the structure is required. PMID:26824062

  18. High temperature gradient micro-sensor for wall shear stress and flow direction measurements

    NASA Astrophysics Data System (ADS)

    Ghouila-Houri, C.; Claudel, J.; Gerbedoen, J.-C.; Gallas, Q.; Garnier, E.; Merlen, A.; Viard, R.; Talbi, A.; Pernod, P.

    2016-12-01

    We present an efficient and high-sensitive thermal micro-sensor for near wall flow parameters measurements. By combining substrate-free wire structure and mechanical support using silicon oxide micro-bridges, the sensor achieves a high temperature gradient, with wires reaching 1 mm long for only 3 μm wide over a 20 μm deep cavity. Elaborated to reach a compromise solution between conventional hot-films and hot-wire sensors, the sensor presents a high sensitivity to the wall shear stress and to the flow direction. The sensor can be mounted flush to the wall for research studies such as turbulence and near wall shear flow analysis, and for technical applications, such as flow control and separation detection. The fabrication process is CMOS-compatible and allows on-chip integration. The present letter describes the sensor elaboration, design, and micro-fabrication, then the electrical and thermal characterizations, and finally the calibration experiments in a turbulent boundary layer wind tunnel.

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

    SciTech Connect

    Moon, Chanho; Kobayashi, Tatsuya; Itoh, Kimitaka; Hatakeyama, Rikizo; Kaneko, Toshiro

    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.

  20. Numerical studies of a confined volatile binary fluid subject to a horizontal temperature gradient

    NASA Astrophysics Data System (ADS)

    Qin, Tongran; Grigoriev, Roman

    2016-11-01

    Our fundamental understanding of convection in a layer of nonisothermal binary fluid with free surface in the presence of noncondensable gases, such as air, is still limited. In relatively thick liquid layers, the flow is driven by a combination of three different forces: buoyancy, thermocapillarity, and solutocapillarity in the liquid layer. Unlike buoyancy, both thermocapillarity and solutocapillarity depend sensitively on the boundary conditions at the liquid-vapor interface. Recent experimental studies showed that the composition of both the liquid and the gas phases have significant effects on the convection pattern. In particular, in a methanol-water mixture, four different flow regimes were identified on a map spanned by the concentration of methanol in the liquid and the concentration of air in the gas, which are thermocapillarity-dominated flow (TDF), solutocapillarity-dominated flow (SDF), unsteady flow (UF) and reversed flow (RF). This talk will present a comprehensive numerical model for a confined volatile binary fluid subject to a horizontal temperature gradient in the presence of noncondensable gases, and illustrate how the composition of both phases affect thermocapillarity and solutocapillarity. The numerical results will also be compared with experiments. Supported by NSF.

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

    NASA Astrophysics Data System (ADS)

    Moon, Chanho; Kobayashi, Tatsuya; Itoh, Kimitaka; Hatakeyama, Rikizo; Kaneko, Toshiro

    2015-05-01

    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 ∇Te/Te strength exceeded 0.54 cm-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.

  2. Weak turbulence theory of ion temperature gradient modes for inverted density plasmas

    SciTech Connect

    Hahm, T.S.; Tang, W.M.

    1989-09-01

    Typical profiles measured in H-mode ( high confinement'') discharges from tokamaks such as JET and DIII-D suggest that the ion temperature gradient instability threshold parameter {eta}{sub i} ({equivalent to}dlnT{sub i}/dlnn{sub i}) could be negative in many cases. Previous linear theoretical calculations have established the onset conditions for these negative {eta}{sub i}-modes and the fact that their growth rate is much smaller than their real frequency over a wide range of negative {eta}{sub i} values. This has motivated the present nonlinear weak turbulence analysis to assess the relevance of such instabilities for confinement in H-mode plasmas. The nonlinear eigenmode equation indicates that the 3-wave coupling to shorter wavelength modes is the dominant nonlinear saturation mechanism. It is found that both the saturation level for these fluctuations and the magnitude of the associated ion thermal diffusivity are considerably smaller than the strong turbulence mixing length type estimates for the more conventional positive-{eta}{sub i}-instabilities. 19 refs., 3 figs.

  3. Role of magnetic shear in dynamics of large-scale structures in electron temperature gradient turbulence

    NASA Astrophysics Data System (ADS)

    Li, Jiquan; Kishimoto, Y.; Miyato, N.; Matsumoto, T.

    2004-11-01

    We investigate how the magnetic shear governs the dynamics of large-scale structures, such as zonal flows and streamers, in electron temperature gradient (ETG) driven turbulence. Based on the well-known 2D Hasegawa-Mima turbulence modeling, which is the inviscid version of fluid (or gyrofluid) ETG turbulence [1], we derive a general dispersion relation of secondary fluctuations through modulation instability analysis. The results show that the formation of different large-scale structures including zonal flow, streamer and so-called generalized Kelvin-Helmholtz (GKH) mode in ETG turbulence depends on the spectral anisotropy of turbulent fluctuation. In a slab geometry, the magnetic shear closely relates to the ETG mode structures so that it may determine the pattern selection in the quasi-steady ETG turbulence. 3D gyrofluid slab ETG simulations show that turbulent ETG fluctuation energy condenses to the zonal flows in the weak shear plasmas and to the streamer component for the high shears. 2D ETG simulations with rather high resolution not only exhibits the global spectral distribution of zonal flows, but also further confirm a mechanism: enhanced zonal flow in weak shear ETG turbulence is limited by exciting a KH mode [1]. Furthermore, in toroidal ETG simulations, streamer structures are observed at around good curvature region along the flux tube in the quasisteady state in some medium shear regime. Related streamer dynamics are also investigated. [1] Jiquan Li and Y. Kishimoto, Phys. Plasmas 11, 1493(2004)

  4. The 1983 Temperature Gradient and Heat Flow Drilling Project for the State of Washington

    SciTech Connect

    Korosec, Michael A.

    1983-11-01

    During the Summer of 1983, the Washington Division of Geology and Earth Resources carried out a three-hole drilling program to collect temperature gradient and heat flow information near potential geothermal resource target areas. The project was part of the state-coupled US Department of Energy Geothermal Program. Richardson Well Drilling of Tacoma, Washington was subcontracted through the State to perform the work. The general locations of the project areas are shown in figure 1. The first hole, DNR 83-1, was located within the Green River valley northwest of Mount St. Helens. This site is near the Green River Soda Springs and along the projection of the Mount St. Helens--Elk Lake seismic zone. The other two holes were drilled near Mount Baker. Hole DNR 83-3 was sited about 1/4 km west of the Baker Hot Springs, 10.5 km east of Mount Baker, while hole DNR 83-5 was located along Rocky Creek in the Sulphur Creek Valley. The Rocky Creek hole is about 10 km south-southwest of the peak. Two other holes, DNR 83-2 and DNR 83-4, were located on the north side of the Sulphur Creek Valley. Both holes were abandoned at early stages of drilling because of deep overburden and severe caving problems. The sites were apparently located atop old landslide deposits.

  5. 1983 temperature gradient and heat flow drilling project for the State of Washington

    SciTech Connect

    Korosec, M.A.

    1983-11-01

    During the Summer of 1983, a three-hole drilling program was carried out to collect temperature gradient and heat flow information near potential geothermal resource target areas. The general locations of the project areas are shown. The first hole, DNR 83-1, was located within the Green River valley northwest of Mount St. Helens. This site is near the Green River Soda Springs and along the projection of the Mount St. Helens - Elk Lake seismic zone. The other two holes were drilled near Mount Baker. Hole DNR 83-3 was sited about 1/4 km west of the Baker Hot Springs, 10.5 km east of Mount Baker, while hole DNR 83-5 was located along Rocky Creek in the Sulphur Creek Valley. The Rocky Creek hole is about 10 km south-southwest of the peak. Two other holes, DNR 83-2 and DNR 83-4, were located on the north side of the Sulphur Creek Valley. Both holes were abandoned at early stages of drilling because of deep overburden and severe caving problems. The sites were apparently located atop old landslide deposits.

  6. Using skin temperature gradients or skin heat flux measurements to determine thresholds of vasoconstriction and vasodilatation.

    PubMed

    House, James R; Tipton, Michael J

    2002-11-01

    Forearm-fingertip skin temperature differentials (T(sk-diff)) are used to indicate vasomotor tone, vasoconstriction defined as having occurred when T(sk-diff)> or =4 degrees C (Sessler et al. 1987, 1988a, b). This study was conducted to determine whether T(sk-diff) or finger pad heat flux (HF) can be used to predict when vasoconstriction and vasodilatation occur. Seven subjects (one female) sat in water at [mean (SD)] 40.7 (0.8) degrees C until their core temperature (T(c)) increased by 1 degrees C, ensuring vasodilatation. The water was then cooled [at a rate of 0.6 (0.1) degrees C x min(-1)] until T(c) fell to 0.5 degrees C below pretesting values, causing vasoconstriction. Subjects were then rewarmed in water [41.2 (1.0) degrees C]. Skin blood flow (SkBF) was measured using laser Doppler flowmetry (LDF) on the left second finger pad [immersed in water at 10.4 (1.4) degrees C as part of another experiment], and infrared plethysmography on the third finger pad of both hands. T(sk-diff) and HF were measured on the right upper limb, which remained in air. When vasodilated, the subjects had a stable T(sk-diff) and HF. During cooling, rapid-onset vasoconstriction occurred coincidental with large gradient changes in HF and T(sk-diff) (inflection points). In two subjects the original vasoconstriction definition (T(sk-diff)> or =4 degrees C) was not attained, in the other five this was achieved 31-51 min after vasoconstriction. During rewarming, the T(sk-diff) and HF inflection points less accurately reflected the onset of vasodilatation, although with one exception they were within 5 min of the LDF changes. We conclude that T(sk-diff) and HF inflection points predict vasoconstriction accurately, and better than T(sk-diff)> or =4 degrees C.

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

    PubMed

    Ngugi, David Kamanda; Antunes, André; Brune, Andreas; Stingl, Ulrich

    2012-01-01

    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 ∼93% 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.

  8. In-Vial Temperature Gradient Headspace Single Drop Microextraction Designed by Multiphysics Simulation.

    PubMed

    Jahan, Sharmin; Zhang, Qiang; Pratush, Amit; Xie, Haiyang; Xiao, Hua; Fan, Liuyin; Cao, Chengxi

    2016-11-01

    Presented herein is a novel headspace single drop microextraction (HS-SDME) based on temperature gradient (TG) for an on-site preconcentration technique of volatile and semivolatile samples. First, an inner vial cap was designed as a cooling device for acceptor droplet in HS-SDME unit to achieve fast and efficient microextraction. Second, for the first time, an in-vial TG was generated between the donor phase in a sample vial at 80 °C and the acceptor droplet under the inner vial cap containing cooling liquid at -20 °C for a TG-HS-SDME. Third, a simple mathematic model and numerical simulations were developed by using heat transfer in fluids, Navier-Stokes and mass balance equations for conditional optimization, and dynamic illumination of the proposed extraction based on COMSOL Multiphysics. Five chlorophenols (CPs) were selected as model analytes to authenticate the proposed method. The comparisons revealed that the simulative results were in good agreement with the quantitative experiments, verifying the design of TG-HS-SDME via the numerical simulation. Under the optimum conditions, the extraction enrichments were improved from 302- to 388-fold within 2 min only, providing 3.5 to 4 times higher enrichment factors as compared to a typical HS-SDME. The simulation indicated that these improvements in the extraction kinetics could be attributed due to the applied temperature gap between the sample matrix and acceptor droplet within the small volume of headspace. Additionally, the experiments demonstrated a good linearity (0.03-100 μg/L, R(2) > 0.9986), low limit of detection (7-10 ng/L), and fair repeatability (<5.9% RSD, n = 6). All of the simulative and experimental results indicated the robustness, precision, and usefulness of TG-HS-SDME for trace analyses of analytes in a wide variety of environmental, pharmaceutical, food safety, and forensic samples.

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

    NASA Astrophysics Data System (ADS)

    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

  10. Temperature-gradient epitaxy under in situ growth mode diagnostics by scanning reflection high-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Koida, T.; Komiyama, D.; Koinuma, H.; Ohtani, M.; Lippmaa, M.; Kawasaki, M.

    2002-01-01

    We have developed a parallel film growth method on a temperature-gradient substrate to quickly control and optimize the film growth mode. A continuous-wave neodymium-doped yttrium-aluminum-garnet laser heating was used to achieve a stable temperature gradient covering a 300 °C range of temperatures over a distance of 11 mm. The growth mode was determined by time-resolved scanning reflection high-energy electron diffraction. Transition from layer-by-layer to step-flow growth by the deposition temperature was observed during La0.5Sr0.5MnO3 film growth on a single SrTiO3 substrate, proving a powerful tool not only for investigating the growth dynamics but also for seeking the optimized deposition conditions in one run of experiment.

  11. Analyzing RNA and DNA folding using temperature gradient gel electrophoresis (TGGE) with application to in vitro selections.

    PubMed

    Chadalavada, Durga M; Bevilacqua, Philip C

    2009-01-01

    Gel electrophoresis is a ubiquitous separation technique in nucleic acid biochemistry. Denaturing gel electrophoresis separates nucleic acids on the basis of length, while native gel electrophoresis separates nucleic acids on the basis of both shape and length. Temperature gradient gel electrophoresis (TGGE), in which a temperature gradient is present across the gel, combines the advantages of denaturing and native gel electrophoresis by having native gel-like properties at low temperatures and denaturing gel-like properties at high temperatures. We describe here the techniques of perpendicular and parallel TGGE and some of their applications. Isolation of stable and unstable RNA and DNA sequences from combinatorial libraries is accomplished with TGGE-SELEX, while thermodynamic characterization of an RNA tertiary motif is performed by perpendicular TGGE-melts. Specific examples are chosen from the literature to illustrate the methods. TGGE provides a powerful biophysical approach for analyzing RNA and DNA that complements more traditional methodologies.

  12. Continuous gradient temperature Raman spectroscopy of n-6 DPA and DHA from -100 C to 20°C

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the great unanswered questions with respect to biological science in general is the absolute necessity of DHA in fast signal processing tissues. N-6 DPA, with just one less diene, group, is fairly abundant in terrestrial food chains yet cannot substitute for DHA. Gradient Temperature Raman sp...

  13. Ion heat pinch due to the magnetic drift resonance with the ion temperature gradient instability in a rotating plasma

    NASA Astrophysics Data System (ADS)

    Zhang, Debing; Xu, Yingfeng; Wang, Shaojie

    2017-03-01

    The ion heat pinch due to the magnetic drift resonance with the ion temperature gradient instability is investigated by using the Lie-transform method. In a tokamak plasma with an equilibrium parallel flow, the total heat flux is found to direct inward with a strong flow shear. The proposed heat pinch can provide possible explanations for some experimental observations.

  14. Spatial and temporal variations in mango colour, acidity, and sweetness in relation to temperature and ethylene gradients within the fruit.

    PubMed

    Nordey, Thibault; Léchaudel, Mathieu; Génard, Michel; Joas, Jacques

    2014-11-01

    Managing fruit quality is complex because many different attributes have to be taken into account, which are themselves subjected to spatial and temporal variations. Heterogeneous fruit quality has been assumed to be partly related to temperature and maturity gradients within the fruit. To test this assumption, we measured the spatial variability of certain mango fruit quality traits: colour of the peel and of the flesh, and sourness and sweetness, at different stages of fruit maturity using destructive methods as well as vis-NIR reflectance. The spatial variability of mango quality traits was compared to internal variations in thermal time, simulated by a physical model, and to internal variations in maturity, using ethylene content as an indicator. All the fruit quality indicators analysed showed significant spatial and temporal variations, regardless of the measurement method used. The heterogeneity of internal fruit quality traits was not correlated with the marked internal temperature gradient we modelled. However, variations in ethylene content revealed a strong internal maturity gradient which was correlated with the spatial variations in measured mango quality traits. Nonetheless, alone, the internal maturity gradient did not explain the variability of fruit quality traits, suggesting that other factors, such as gas, abscisic acid and water gradients, are also involved.

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

    PubMed

    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.

  16. Temperature and diet effects on omnivorous fish performance: Implications for the latitudinal diversity gradient in herbivorous fishes

    USGS Publications Warehouse

    Behrens, M.D.; Lafferty, K.D.

    2007-01-01

    Herbivorous fishes show a clear latitudinal diversity gradient, making up a larger proportion of the fish species in a community in tropical waters than in temperate waters. One proposed mechanism that could drive this gradient is a physiological constraint due to temperature. One prediction based on this mechanism is that if herbivorous fishes could shift their diet to animal material, they would be better able to grow, survive, and reproduce in cold waters. We tested this prediction on the omnivore Girella nigricans under different temperature and diet regimes using RNA-DNA ratios as an indicator of performance. Fish had increased performance (100%) at low temperatures (12??C) when their diet was supplemented with animal material. In contrast, at higher temperatures (17, 22, and 27??C) fish showed no differences between diets. This indicates that omnivorous fishes could increase their performance at low temperatures by consuming more animal matter. This study supports the hypothesis that a relative increase in the nutritional value of plant material at warmer temperatures could drive the latitudinal diversity gradient in herbivorous fishes. ?? 2007 NRC.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. On the role of sea surface temperature gradients in forcing low-level winds and convergence in the tropics

    NASA Technical Reports Server (NTRS)

    Lindzen, Richard S.; Nigam, Sumant

    1987-01-01

    The potential contribution of the SST gradient-driven flow to the low-level (p not less than 700 mb) convergence over tropical oceans is determined using a simple one-layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically (consistent with the ECMWF analyzed data). The influence of the layers above 700 mb is intentionally suppressed. The results of the study demonstrate the importance of taking account of the fact that cumulonimbus convection takes a small but finite time to adjust to low-level convergence. Failure to consider this effect leads to unreasonably large equatorial convergence.

  19. The transport phenomena during the growth of ZnTe crystal by the temperature gradient solution growth technique

    NASA Astrophysics Data System (ADS)

    Yin, Liying; Jie, Wanqi; Wang, Tao; Zhou, Boru; Yang, Fan

    2017-03-01

    A numerical model is developed to simulate the temperature field, the thermosolutal convection, the solute segregation and the growth interface morphology during the growth of ZnTe crystal from Te rich solution by the temperature gradient solution growth (TGSG) technique. Effects of the temperature gradient on the transport phenomena, the growth interface morphology and the growth rate are examined. The influences of the latent heat and the thermal conductivity of ZnTe crystal on the transport phenomena and the growth interface are also discussed. We find that the mass transfer of ZnTe in the solution is very slow because of the low diffusion coefficient and the lack of mixing in the lower part of the solution. During the growth, dilute solution with high density and low growth temperature accumulates in the central region of the growth interface, making the growth interface change into two distinct parts. The inner part is very concave, while the outer part is relatively flat. Growth conditions in front of the two parts of the growth interface are different. The crystalline quality of the inner part of the ingot is predicted to be worse than that of the outer part. High temperature gradient can significantly increase the growth rate, and avoid the diffusion controlled growth to some extent.

  20. Comparison between the Structural Evolution of Dry Snow under Quasi-isothermal Conditions and in a Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Baker, I.; Chen, S.

    2010-12-01

    The structural evolution of dry snow - snow without free water - begins as soon as snow reaches the ground. Both the development of crystal morphologies and the evolution of structural parameters of snow aggregates strongly depend on the thermal conditions encountered in the snowpack, particularly the presence or absence of a macro temperature gradient. To understand the influence of thermal conditions on structural changes, we examined three natural snow specimens as they underwent evolution under three different well-controlled conditions: a macro uniform temperature (-5 ± 0.2°C) and two temperature gradient conditions (50°C m-1 and 140°C m-15, with the top of the specimens maintained at -2.3 ± 0.2°C). An X-ray computed microtomography (micro-CT) scanner was employed at regular time intervals to acquire both three-dimensional renderings and structural parameters, including relative density, specific surface area (SSA), structure thickness (Sr.Th), structure model index (SMI), and degree of anisotropy (DA). A scanning electron microscope (SEM) was used immediately after periodic micro-CT observations to examine fine scale structural features. For the isothermal conditions at -5 ± 0.2°C, the structure became less complex and coarser with increasing time, which was reflected by an exponential decline in SSA and an increase in Sr.Th, respectively. Additionally, the SMI value increased and approached 3, indicating the formation of rounded structures. This rounding process was confirmed by SEM observations. Under a temperature gradient, although the crystals grew much faster, the mean Sr.Th did not increase, probably due to the formation of kinetic forms, such as the staircase-like structures on the edges and flat thin ice layers on the surfaces of crystals revealed by SEM observations. The SMI value declined over time, with a higher rate observed for the specimen subjected to the higher temperature gradient, indicating the formation of faceted crystals. An

  1. The influence of ocean surface temperature gradient and continentality on the Walker circulation. II - Prescribed global changes

    NASA Technical Reports Server (NTRS)

    Stone, P. H.; Chervin, R. M.

    1984-01-01

    The series of experiments presently used to investigate the mechanisms responsible for forcing the global Walker circulation features worldwide changes in ocean surface temperatures (OSTs), topography, and/or continents. The primary factor affecting circulation is noted to be the global distribution of continents and oceans; while OST gradients are also important, topography emerges as comparatively unimportant. Continentality and OST gradients force the model atmosphere through the introduction of zonal variations in surface heating. The vertical motions to which they give rise yield moisture convergence and condensation variations which reinforce vertical motions. The forcing by OST gradients is partly nonlocal, and the atmospheric response is effected by continentality. In all cases, vertical motion zonal variations correlate with precipitation.

  2. On the threshold of magnetic island width in nonlinear mutual destabilization of tearing mode and ion temperature gradient mode

    NASA Astrophysics Data System (ADS)

    Liu, T.; Wang, Z. X.; Hu, Z. Q.; Wei, L.; Li, J. Q.; Kishimoto, Y.

    2016-10-01

    Nonlinear multi-scale interactions between the tearing mode and the ion temperature gradient (ITG) mode are investigated by means of numerical simulations in a self-consistent 5-field Landau-fluid model. It is observed that there exists a threshold of magnetic island width in the nonlinear evolution of interaction, above which the ITG turbulence can enhance the island growth significantly. Dependence of the threshold on basic plasma parameters is deeply analyzed. It is found that the higher ion viscosity may raise the threshold through its effect on the E × B drift and the diamagnetic drift of electron density gradient in different ways, both of which play a synergetic role in determining the threshold. Moreover, the effects of plasma resistivity, gradient length of equilibrium current sheet as well as magnetic shear of field line on the threshold are discussed based on the analyses of the initial growth rate of islands.

  3. 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

    NASA Technical Reports Server (NTRS)

    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.

  4. Neutron decay of the Giant Pairing Vibration in 15C

    NASA Astrophysics Data System (ADS)

    Cavallaro, M.; Agodi, C.; Assié, M.; Azaiez, F.; Cappuzzello, F.; Carbone, D.; de Séréville, N.; Foti, A.; Pandola, L.; Scarpaci, J. A.; Sgouros, O.; Soukeras, V.

    2016-06-01

    The neutron decay of the resonant states of light neutron-rich nuclei is an important and poorly explored property, useful to extract valuable nuclear structure information. The neutron decay of the 15C resonances populated via the two-neutron transfer reaction 13C(18O,16O n) at 84 MeV incident energy is studied using an innovative technique which couples the MAGNEX magnetic spectrometer and the EDEN neutron detector array. The data show that the recently observed 15C Giant Pairing Vibration at 13.7 MeV mainly decays via two-neutron emission.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Multiproxy reconstruction of tropical Pacific Holocene temperature gradients and water column structure

    NASA Astrophysics Data System (ADS)

    Arbuszewski, J. A.; Oppo, D.; Huang, K.; Dubois, N.; Galy, V.; Mohtadi, M.; Herbert, T.; Rosenthal, Y.; Linsley, B. K.

    2012-12-01

    consider records from organic (sterol abundances) and inorganic proxies (Mg/Ca and δ18O of 3 planktonic foraminiferal species, % G. bulloides) to reconstruct zonal tropical Pacific (sub)surface temperature and stratification gradients over the Holocene. A benefit of using this approach is that it enables us to combine the strengths of each individual proxy to derive more robust records. We will compare our records with published paleoproxy and model studies in the Pacific and Indo-Pacific regions. Armed with this information, we aim to better understand mean state changes in the tropical Pacific over the Holocene. 1 Ropelewski, C. F. & Halpert, M. S. Monthly Weather Review 115, 1606-1626 (1987). 2 Collins, M. et al. Nature Geoscience 3, doi: 10.1038/NGEO1868 (2010). 3 Koutavas, A., Lynch-Steiglitz, J., Marchitto, T. & Sachs, J. Science 297, 226-230 (2002). 4 Moy, C. M., Seltzer, G. O., Rodbell, D. T. & Anderson, D. M. Nature 420, 162-165 (2002). 5 Conroy, J. L., Overpeck, J. T., Cole, J. E., Shanahan, T. M. & Steinitz-Kannan, M. Quaternary Science Reviews 27, 1166-1180 (2008). 6 Makou, M. C., Eglinton, T. I., Oppo, D. W. & Hughen, K. A. Geology 38, 43-46 (2010). 7 Karnauskas, K., Smerdon, J., Seager, R. & Gonzalez-Rouco, J. Journal of Climate, doi: 10.1178/JCLI-D-1111-00421.00421 (2012 (in press)). 8 Clement, A., Seager, R. & Cane, M. Paleoceanography 14, 441-456 (2000).

  7. The influence of ocean surface temperature gradient and continentality on the Walker circulation. I - Prescribed tropical changes

    NASA Technical Reports Server (NTRS)

    Chervin, R. M.; Druyan, L. M.

    1984-01-01

    A coarse mesh global climate model has been developed to assess ocean surface temperature (OST) gradient and continentality influences on the Walker circulation, which is characterized in the zonal plane by three pairs of clockwise and counterclockwise cells in the troposphere. The model response exhibits statistically significant changes in the intensity of the various cells and branches with small shifts in the east-west extent. The overall structure in the zonal plane for experiments with the coldest and with mean temperatures, however, remained unchanged. In an experiment involving the replacement of the South American continent by an ocean with OSTs linearly interpolated from the eastern Pacific to the western Atlantic, a dramatic change took place in the structure of the Walker circulation. It is concluded that both continentality and OST gradient are important Walker circulation forcing mechanisms.

  8. Differences in the Temperature Sensitivity of Soil Organic Carbon Decomposition in a Semi-Arid Ecosystem across an Elevational Gradient

    NASA Astrophysics Data System (ADS)

    Delvinne, H.; Flores, A. N.; Benner, S. G.; Feris, K. P.; De Graaff, M. A.

    2015-12-01

    Semi-arid ecosystems are a significant component of the global carbon (C) cycle as they store approximately 20% of global soil C. Yet, projected increases in mean annual temperatures might alter the amount of soil organic C (SOC) currently stored in these ecosystems. Uncertainties about the temperature sensitivity of SOC decomposition have hindered accurate predictions of C cycle feedbacks to climate change. This study aims to elucidate how the temperature sensitivity of SOC decomposition varies along an elevational (1000m) and climatic (i.e. mean annual temperature and precipitation) gradient. The study sites are located at Reynolds Creek Critical Zone Observatory in Owyhee Mountains of Idaho, USA. We conducted stratified random sampling of soil up to 0-5cm across sagebrush canopy and inter-canopy areas at four elevations. We hypothesized decomposition of SOC pools at lower elevations to have greater temperature sensitivity (more CO2 respired per unit C) compared to upper due to the quality of C that is inherently more temperature sensitive. To assess the temperature sensitivity of SOC decomposition, we used aerobic laboratory incubations (n=40) across a temperature gradient ((15, 20, 25, 30) oC) at constant soil moisture (60% water holding capacity) for 120 days and measured CO2 respired. Cumulative CO2 respired increased with increasing incubation temperature. Cumulative CO2 respired also increased with elevation as upper elevations support greater amounts of C. However, when normalized by SOC, we found that the temperature response of CO2 respiration was greater in soils derived from lower than higher elevations (p<0.05). These results indicate that the response of SOC decomposition to elevated temperatures differs strongly across the landscape in semi-arid ecosystems.

  9. Direct numerical simulation of Taylor-Couette flow subjected to a radial temperature gradient

    SciTech Connect

    Teng, Hao; Liu, Nansheng Lu, Xiyun; Khomami, Bamin

    2015-12-15

    Direct numerical simulations have been performed to study the Taylor-Couette (TC) flow between two rotating, coaxial cylinders in the presence of a radial temperature gradient. Specifically, the influence of the buoyant force and the outer cylinder rotation on the turbulent TC flow system with the radius ratio η = 0.912 was examined. For the co-rotating TC flows with Re{sub i} (inner cylinder) =1000 and Re{sub o} (outer cylinder) =100, a transition pathway to highly turbulent flows is realized by increasing σ, a parameter signifying the ratio of buoyant to inertial force. This nonlinear flow transition involves four intriguing states that emerge in sequence as chaotic wavy vortex flow for σ = 0, wavy interpenetrating spiral flows for σ = 0.02 and 0.05, intermittent turbulent spirals for σ = 0.1 and 0.2, and turbulent spirals for σ = 0.4. Overall, the fluid motion changes from a centrifugally driven flow regime characterized by large-scale wavy Taylor vortices (TVs) to a buoyancy-dominated flow regime characterized by small-scale turbulent vortices. Commensurate changes in turbulence statistics and heat transfer are seen as a result of the weakening of large-scale TV circulations and enhancement of turbulent motions. Additionally, the influence of variation of the outer cylinder rotation, −500 < Re{sub o} < 500 in presence of buoyancy (σ = 0.1) with Re{sub i} = 1000, has been considered. Specifically, it is demonstrated that this variation strongly influences the azimuthal and axial mean flows with a weaker influence on the fluctuating fluid motions. Of special interest, here are the turbulent dynamics near the outer wall where a marked decrease of turbulence intensity and a sign inversion of the Reynolds stress R{sub rz} are observed for the strongly counter-rotating regimes (Re{sub o} = − 300 and −500). To this end, it has been shown that the underlying flow physics for this drastic modification are associated with the modification of the correlation

  10. Application of temperature gradient gel electrophoresis to the characterization of a nitrifying bioaugmentation product.

    PubMed

    Fouratt, Melissa A; Rhodes, Jeremy S; Smithers, Charles M; Love, Nancy G; Stevens, Ann M

    2003-03-01

    The microbial population of a nitrifying bioaugmentation product (NBP) has been examined using a combination of conventional bacteriological methods and modern molecular techniques. Variable region 3 (V3) of the 16S rRNA genes of the bacteria in NBP was amplified via the polymerase chain reaction (PCR) with universal eubacterial primers and analyzed via temperature gradient gel electrophoresis (TGGE). Two of the predominant PCR products in NBP were purified from the TGGE gel matrix, reamplified via PCR and sequenced. Two nitrifying strains (NS500-9 and MPN2) that had been isolated from the NBP mixed consortium and grown in pure culture were found, via TGGE, to have identical 16S rRNA sequences to the PCR products under investigation. Nearly the full-length 16S rRNA genes from these two organisms were PCR-amplified, cloned, and sequenced in order to provide a basis for more accurate phylogenetic analysis. The two dominant organisms in the NBP, NS500-9 and MPN2, were thereby found to be most closely related to Nitrosomonas and Nitrobacter species, respectively, in the database. Samples from a laboratory-scale bioreactor, bioaugmented with NBP, were used in an attempt to correlate an increase in activity with a detectable shift in the population of NS500-9 and MPN2 via TGGE. No detectable shift in population was observed in these samples even though the system exhibited increased levels of nitrification. Therefore, the sensitivity of the TGGE system was also examined by determining the limits of detection when NBP was present in activated sludge. In biomass spiking experiments as well as in genomic DNA spiking experiments, it was found that NBP must be present at a level of at least 5% of the total population in order to be detected, whereas bioaugmentation at 1% of the total population was enough to yield significant improvements in nitrification efficiency. This study demonstrates how community profiling of an undefined microbial population via TGGE can be used to

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

    PubMed Central

    2010-01-01

    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. Conclusions This work reports

  12. Short-Scale Turbulent Fluctuations Driven by the Electron-Temperature Gradient in the National Spherical Torus Experiment

    SciTech Connect

    Mazzucato, E.; Smith, D. R.; Bell, R. E.; Kaye, S.; Davis, W.; Hosea, J.; LeBlanc, B; Wilson, J. R.; Ryan, Philip Michael; Domier, C. W.; Luhmann, N. C.; Yuh, H.; Lee, W.; Park, H.

    2008-01-01

    Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k?e 0:1 0:4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient.

  13. Influence of the temperature gradient in blubber on the bioaccumulation of persistent lipophilic organic chemicals in seals.

    PubMed

    Czub, Gertje; McLachlan, Michael S

    2007-08-01

    Seals constitute an important link in food webs of the Arctic environment and are an important vector of persistent lipophilic organic pollutants to top predators (e.g., polar bears) and humans. Two fugacity-based, non-steady state, mechanistic lifetime models were assembled to explore the influence of the temperature gradient in the insulating blubber on the distribution and bioaccumulation of persistent lipophilic organic pollutants in seals. The behavior of a two-compartment model that distinguishes between the gastrointestinal tract and the seal itself was compared with a three-compartment model, in which a separate blubber compartment was implemented with a temperature gradient through the insulation layer. In both models, equilibrium partitioning between the animal's tissues, blood, and milk was assumed. The models were parameterized for ringed seals (Phoca hispida) and evaluated using field data for bioaccumulation of polychlorinated biphenyls in this species. The two-compartment model resulted in predicted concentrations below reported field data. This was in particular the case for females, for which the elimination of the contaminants via milk was overpredicted by up to one order of magnitude. The three-compartment model with its consideration of the temperature gradient in blubber yielded predictions that were much more consistent with the field data. It also predicted a fractionation of polychlorinated biphenyl congeners between different blubber layers, as well as between blubber and blood or milk, which was in good qualitative agreement with observations reported in the literature. This work indicates that the temperature gradient in the blubber has an impact on the bioaccumulation of persistent lipophilic organic pollutants in seals and in marine mammals in general.

  14. Fourier transform infrared and Raman spectroscopic characterization of homogeneous solution concentration gradients near a container wall at different temperatures

    NASA Technical Reports Server (NTRS)

    Loo, B. H.; Burns, D. H.; Lee, Y. G. L.; Emerson, M. T.

    1991-01-01

    Fourier transform infrared (FTIR) and Raman spectroscopic techniques were used to study the solution concentration gradient in succino nitrile-rich and water-rich homogeneous solutions. The spectroscopic data shows significant concentration dependency. Although FTIR-attenuated total reflectance could not yield surface spectra since the evanescent infrared wave penetrated deep into the bulk solution, it showed that water-rich clusters were decreased at higher temperatures. This result is consistent with the calorimetric results reported earlier.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Comparison of Experimentally Measured Temperature Gradient and Finite-Element-Method Simulations for Two Continuously Cast Bloom Heating Strategies

    NASA Astrophysics Data System (ADS)

    Kvíčala, M.; Frydrýšek, K.; Štamborská, M.

    2015-03-01

    This paper deals with the comparison of experimentally measured temperature gradients and finite-element-method (FEM) simulations of two heating strategies that were used for continuously cast bloom soaking. The temperature gradient between the bloom surface and center was measured by two thermocouples incorporated directly into the bloom. Scanning electron microscopy equipped by energy dispersive X-ray spectroscopy analysis, hot tensile tests, and interdendritic solidification software was used for modeling of steel thermophysical properties with respect to the alloying-elements macrosegregation. The model of the bloom was programmed in the Fortran language. The FEM software MARC/MENTAT 2012 was used for simulation of two heating strategies (plane strain formulation). The first heating model was fitted to the commonly used heating strategy when internal defects grew above the critical limit. The second heating model was a newly proposed strategy that consisted of slower heating up to 1073 K when the first warming-through period occurred. The FEM simulations included determinations of the temperature gradient, the equivalent of stress, the equivalent of elastic strain, the equivalent of plastic strain, and the equivalent of total strain. The simulation results were in good agreement with experimental observations. The new heating strategy based on the FEM simulations led to significantly lower occurrence of internal defects in hot-rolled billets that are used for cylinder production.

  18. Comparative Analysis of Denaturing Gradient Gel Electrophoresis and Temporal Temperature Gradient Gel Electrophoresis Profiles as a Tool for the Differentiation of Candida Species

    PubMed Central

    Mohammadi, Parisa; Hamidkhani, Aida; Asgarani, Ezat

    2015-01-01

    Background: Candida species are usually opportunistic organisms that cause acute to chronic infections when conditions in the host are favorable. Accurate identification of Candida species is an essential pre-requisite for improved therapeutic strategy. Identification of Candida species by conventional methods is time-consuming with low sensitivity, yet molecular approaches have provided an alternative way for early diagnosis of invasive candidiasis. Denaturing gradient gel electrophoresis (DGGE) and temporal temperature gradient gel electrophoresis (TTGE) are polymerase chain reaction (PCR)-based approaches that are used for studying the community structure of microorganisms. By using these methods, simultaneous identification of multiple yeast species will be possible and reliable results will be obtained quickly. Objectives: In this study, DGGE and TTGE methods were set up and evaluated for the detection of different Candida species, and their results were compared. Materials and Methods: Five different Candida species were cultured on potato dextrose agar medium for 24 hours. Next, total DNA was extracted by the phenol-chloroform method. Two sets of primers, ITS3-GC/ITS4 and NL1-GC/LS2 were applied to amplify the desired regions. The amplified fragments were then used to analyze DGGE and TTGE profiles. Results: The results showed that NL1-GC/LS2 primer set could yield species-specific amplicons, which were well distinguished and allowed better species discrimination than that generated by the ITS3-GC/ITS4 primer set, in both DGGE and TTGE profiles. All five Candida species were discriminated by DGGE and TTGE using the NL1-GC/LS2 primer set. Conclusions: Comparison of DGGE and TTGE profiles obtained from NL1-GC/LS2 amplicons exhibited the same patterns. Although both DGGE and TTGE techniques are capable of detecting Candida species, TTGE is recommended because of easier performance and lower costs. PMID:26568801

  19. Large-scale spatial variability of riverbed temperature gradients in Snake River fall Chinook salmon spawning areas

    SciTech Connect

    Hanrahan, Timothy P.

    2007-02-01

    In the Snake River basin of the Pacific northwestern United States, hydroelectric dam operations are often based on the predicted emergence timing of salmon fry from the riverbed. The spatial variability and complexity of surface water and riverbed temperature gradients results in emergence timing predictions that are likely to have large errors. The objectives of this study were to quantify the thermal heterogeneity between the river and riverbed in fall Chinook salmon spawning areas and to determine the effects of thermal heterogeneity on fall Chinook salmon emergence timing. This study quantified river and riverbed temperatures at 15 fall Chinook salmon spawning sites distributed in two reaches throughout 160 km of the Snake River in Hells Canyon, Idaho, USA, during three different water years. Temperatures were measured during the fall Chinook salmon incubation period with self-contained data loggers placed in the river and at three different depths below the riverbed surface. At all sites temperature increased with depth into the riverbed, including significant differences (p<0.05) in mean water temperature of up to 3.8°C between the river and the riverbed among all the sites. During each of the three water years studied, river and riverbed temperatures varied significantly among all the study sites, among the study sites within each reach, and between sites located in the two reaches. Considerable variability in riverbed temperatures among the sites resulted in fall Chinook salmon emergence timing estimates that varied by as much as 55 days, depending on the source of temperature data used for the estimate. Monitoring of riverbed temperature gradients at a range of spatial scales throughout the Snake River would provide better information for managing hydroelectric dam operations, and would aid in the design and interpretation of future empirical research into the ecological significance of physical riverine processes.

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

    SciTech Connect

    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.

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

    USGS Publications Warehouse

    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

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

    PubMed

    Osland, Michael J; Day, Richard H; Hall, Courtney T; Brumfield, Marisa D; Dugas, Jason L; 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 yr, 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

  3. Locomotor Activity and Body Temperature Patterns over a Temperature Gradient in the Highveld Mole-Rat (Cryptomys hottentotus pretoriae).

    PubMed

    Haupt, Meghan; Bennett, Nigel C; Oosthuizen, Maria K

    2017-01-01

    African mole-rats are strictly subterranean mammals that live in extensive burrow systems. High humidity levels in the burrows prevent mole-rats from thermoregulating using evaporative cooling. However, the relatively stable environment of the burrows promotes moderate temperatures and small daily temperature fluctuations. Mole-rats therefore display a relatively wide range of thermoregulation abilities. Some species cannot maintain their body temperatures at a constant level, whereas others employ behavioural thermoregulation. Here we test the effect of ambient temperature on locomotor activity and body temperature, and the relationship between the two parameters, in the highveld mole-rat. We exposed mole-rats to a 12L:12D and a DD light cycle at ambient temperatures of 30°C, 25°C and 20°C while locomotor activity and body temperature were measured simultaneously. In addition, we investigated the endogenous rhythms of locomotor activity and body temperature at different ambient temperatures. Mole-rats displayed nocturnal activity at all three ambient temperatures and were most active at 20°C, but least active at 30°C. Body temperature was highest at 30°C and lowest at 20°C, and the daily cycle was highly correlated with locomotor activity. We show that the mole-rats have endogenous rhythms for both locomotor activity and body temperature. However, the endogenous body temperature rhythm appears to be less robust compared to the locomotor activity rhythm. Female mole-rats appear to be more sensitive to temperature changes than males, increased heterothermy is evident at lower ambient temperatures, whilst males show smaller variation in their body temperatures with changing ambient temperatures. Mole-rats may rely more heavily on behavioural thermoregulation as it is more energy efficient in an already challenging environment.

  4. Locomotor Activity and Body Temperature Patterns over a Temperature Gradient in the Highveld Mole-Rat (Cryptomys hottentotus pretoriae)

    PubMed Central

    Haupt, Meghan; Bennett, Nigel C.

    2017-01-01

    African mole-rats are strictly subterranean mammals that live in extensive burrow systems. High humidity levels in the burrows prevent mole-rats from thermoregulating using evaporative cooling. However, the relatively stable environment of the burrows promotes moderate temperatures and small daily temperature fluctuations. Mole-rats therefore display a relatively wide range of thermoregulation abilities. Some species cannot maintain their body temperatures at a constant level, whereas others employ behavioural thermoregulation. Here we test the effect of ambient temperature on locomotor activity and body temperature, and the relationship between the two parameters, in the highveld mole-rat. We exposed mole-rats to a 12L:12D and a DD light cycle at ambient temperatures of 30°C, 25°C and 20°C while locomotor activity and body temperature were measured simultaneously. In addition, we investigated the endogenous rhythms of locomotor activity and body temperature at different ambient temperatures. Mole-rats displayed nocturnal activity at all three ambient temperatures and were most active at 20°C, but least active at 30°C. Body temperature was highest at 30°C and lowest at 20°C, and the daily cycle was highly correlated with locomotor activity. We show that the mole-rats have endogenous rhythms for both locomotor activity and body temperature. However, the endogenous body temperature rhythm appears to be less robust compared to the locomotor activity rhythm. Female mole-rats appear to be more sensitive to temperature changes than males, increased heterothermy is evident at lower ambient temperatures, whilst males show smaller variation in their body temperatures with changing ambient temperatures. Mole-rats may rely more heavily on behavioural thermoregulation as it is more energy efficient in an already challenging environment. PMID:28072840

  5. Effect of design variables, temperature gradients and speed of life and reliability of a rotating disk

    NASA Technical Reports Server (NTRS)

    Zaretsky, E. V.; Smith, T. E.; August, R.

    1986-01-01

    A generalized methodology to predict the fatigue life and reliability of a rotating disk such as used for aircraft engine turbines and compressors is advanced. The approach incorporates the computed life of elemental stress volumes to predict system life and reliability. Disk speed and thermal gradients as well as design variables such as disk diameter and thickness and bolt hole size, number and location are considered.

  6. Modeling of the Snow Temperature Gradient Metamorphism by Using 3D Images from X-ray Microtomography

    NASA Astrophysics Data System (ADS)

    Flin, F.; Brzoska, J.; Pieritz, R. A.; Lesaffre, B.; Coleou, C.; Furukawa, Y.

    2006-12-01

    Among the different kinds of metamorphisms that may occur in snow, the temperature gradient (TG) metamorphism is probably the most interesting. Typically occurring by cold and clear night, when the TG between the top and the bottom of the snow layer is high, this metamorphism is characterized by the formation of facets at the bottom of the grains, while upper parts remain rounded [1]. Since the TG metamorphism may be the source of week layer formation in the snow cover, its study has major issues in avalanche studies and is an active research field in snow and ice community. Despite of this interest, the TG metamorphism remains quite poorly understood. In particular, two fundamental questions have not been fully solved. First, what is the driving force of the matter exchange in the ice matrix and what are the associated mechanisms? Second, what determines concretely whether well-rounded or faceted shapes can appear? These two questions have been addressed and partly solved by Colbeck [2] more than twenty years ago, but the results where based on 2D observations and very simple approximations on the snow geometry. In our approach, we would like to take advantage of X-ray microtomographic techniques and revisit these questions by using high-resolution 3D images. A simple physical model describing the temperature gradient metamorphism of snow is presented in this work. This model, based on Kelvin and Langmuir-Knudsen equations, is close to a previously developed model of isothermal metamorphism [3], but takes into account the variation of the saturating vapor pressure with temperature. It can determine locally whether the ice is condensing or subliming, just depending on both the temperatures in the snow matrix and the local mean curvatures of the ice/pore interface. This model can also explain the formation of facets that occurs during the metamorphism. Thanks to X-ray microtomographic images of snow samples obtained under moderate temperature gradient conditions

  7. Thermal denaturation of double-stranded nucleic acids: prediction of temperatures critical for gradient gel electrophoresis and polymerase chain reaction.

    PubMed Central

    Steger, G

    1994-01-01

    A program is described which calculates the thermal stability and the denaturation behaviour of double-stranded DNAs and RNAs up to a length of 1000 base pairs. The algorithm is based on recursive generation of conditional and a priori probabilities for base stacking. Output of the program may be compared directly to experimental results; thus the program may be used to optimize the nucleic acid fragments, the primers and the experimental conditions prior to experiments like polymerase chain reactions, temperature-gradient gel electrophoresis, denaturing-gradient gel electrophoresis and hybridizations. The program is available in three versions; the first version runs interactively on VAXstations producing graphics output directly, the second is implemented as part of the HUSAR package at GENIUSnet, the third runs on any computer producing text output which serves as input to available graphics programs. Images PMID:8052531

  8. Losses of leaf area owing to herbivory and early senescence in three tree species along a winter temperature gradient

    NASA Astrophysics Data System (ADS)

    González-Zurdo, P.; Escudero, A.; Nuñez, R.; Mediavilla, S.

    2016-11-01

    In temperate climates, evergreen leaves have to survive throughout low temperature winter periods. Freezing and chilling injuries can lead to accelerated senescence of part of the leaf surface, which contributes to a reduction of the lifespan of the photosynthetic machinery and of leaf lifetime carbon gain. Low temperatures are also associated with changes in foliar chemistry and morphology that affect consumption by herbivores. Therefore, the severity of foliar area losses caused by accelerated senescence and herbivory can change along winter temperature gradients. The aim of this study is to analyse such responses in the leaves of three evergreen species ( Quercus ilex, Q. suber and Pinus pinaster) along a climatic gradient. The leaves of all three species presented increased leaf mass per area (LMA) and higher concentrations of structural carbohydrates in cooler areas. Only the two oak species showed visible symptoms of damage caused by herbivory, this being less intense at the coldest sites. The leaves of all three species presented chlorotic and necrotic spots that increased in size with leaf age. The foliar surface affected by chlorosis and necrosis was larger at the sites with the coldest winters. Therefore, the effects of the winter cold on the lifespan of the photosynthetic machinery were contradictory: losses of leaf area due to accelerated senescence increased, but there was a decrease in losses caused by herbivory. The final consequences for carbon assimilation strongly depend on the exact timing of the appearance of the damage resulting from low temperature and grazing by herbivores.

  9. Renormalized theory of ion temperature gradient instability of the magnetic-field-aligned plasma shear flow with hot ions

    SciTech Connect

    Mikhailenko, V. V. Mikhailenko, V. S.; Lee, Hae June

    2015-10-15

    The developed kinetic theory for the stability of a magnetic-field-aligned (parallel) shear flow with inhomogeneous ion temperature [Mikhailenko et al., Phys. Plasmas 21, 072117 (2014)] predicted that a kinetic instability arises from the coupled reinforcing action of the flow velocity shear and ion temperature gradient in the cases where comparable ion and electron temperatures exist. In the present paper, the nonlinear theory was developed for the instability caused by the combined effects of ion-temperature-gradient and shear-flow (ITG–SF). The level of the electrostatic turbulence is determined for the saturation state of the instability on the basis of the nonlinear dispersion equation, which accounts for a nonlinear scattering of ions by the developed turbulence in a sheared flow. The renormalized quasilinear equation for the ion distribution function, which accounts for the turbulent scattering of ions by ITG–SF driven turbulence, was derived and employed for the estimation of the turbulent ion viscosity, the anomalous ion thermal conductivity, and anomalous ion heating rate at the saturation state of the instability.

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

    PubMed Central

    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

  11. Probing temperature gradients within the GaN buffer layer of AlGaN/GaN high electron mobility transistors with Raman thermography

    SciTech Connect

    Hodges, C. Pomeroy, J.; Kuball, M.

    2014-02-14

    We demonstrate the ability of confocal Raman thermography using a spatial filter and azimuthal polarization to probe vertical temperature gradients within the GaN buffer layer of operating AlGaN/GaN high electron mobility transistors. Temperature gradients in the GaN layer are measured by using offset focal planes to minimize the contribution from different regions of the GaN buffer. The measured temperature gradient is in good agreement with a thermal simulation treating the GaN thermal conductivity as homogeneous throughout the layer and including a low thermal conductivity nucleation layer to model the heat flow between the buffer and substrate.

  12. THE EFFECT OF VERTICAL TEMPERATURE GRADIENT ON THE PROPAGATION OF THREE-DIMENSIONAL WAVES IN A PROTOPLANETARY DISK

    SciTech Connect

    Lee, Wing-Kit; Gu, Pin-Gao

    2015-11-20

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

  13. Edge temperature gradient as intrinsic rotation drive in Alcator C-Mod tokamak plasmas.

    PubMed

    Rice, J E; Hughes, J W; Diamond, P H; Kosuga, Y; Podpaly, Y A; Reinke, M L; Greenwald, M J; Gürcan, Ö D; Hahm, T S; Hubbard, A E; Marmar, E S; McDevitt, C J; Whyte, D G

    2011-05-27

    Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge ∇T, but completely different edge ∇n, it may be concluded that the drive of the intrinsic rotation is the edge ∇T rather than ∇P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated.

  14. Cyclic Patterns of Interaction between the Surface Gradient of Temperature, Salinity and Chlorophyll in the Open Ocean and the Coastal Zone

    NASA Astrophysics Data System (ADS)

    Kartushinsky, Alexei

    Satellite data were used to calculate mean gradient fields of temperature, salinity and chlorophyll concentration in the ocean for different periods of time. Also we used data buoy observations in situ and some numerical modeling results for a better understanding of the dynamic mechanisms involved and their role in the Global ocean and coastal zones. The high temperature and salinity gradient are formed under the periodically action of jet currents, large rings and eddies and upwelling, which transfer water masses in the ocean and influence the distribution of phytoplankton. The gradient fields and their high values give us information about spatial distribution of main frontal zones. The main stage of research is evaluation of statistical correlation between gradients of temperature, salinity and chlorophyll concentration, which suggests a combined effect of physical and biological processes in a synergistically active ocean zones. The software calculates and produces the averages horizontal gradients in the ocean for different grids. Calculations are also made to find latitudianal, meridional, and absolute gradients, pointing to main frontal zones. We conducted a study of cyclic patterns in relation to changes of gradient fields. Statistical relation of temperature, salinity and chlorophyll concentration gradients in various areas of the global ocean and coastal zone with various scales of space-time averaging was analyzed. Pair correlation of gradient fields for steady frontal zones was estimated. Numerous researches in the area show that the advection of currents, horizontal turbulent heat exchange and the radiation heat flow in separate parts of the ocean impact on the structure of gradient fields. Cycles of the gradient variability in the oceanic frontal zones can be used to assess pulse disturbance of the mass, heat transport and fluxes over the ocean and their interaction with atmosphere and subsequent impact on land ecosystems.

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

    PubMed

    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.

  16. Segregation of Particles by Size and Density in Dense Sheared Flows: Gravity, Temperature Gradients, and Stress Partitioning

    NASA Astrophysics Data System (ADS)

    Tan, Danielle; Hill, Kimberly

    2013-11-01

    In sheared mixtures of different-sized (same density) particles modestly larger particles tend to go up (toward the free surface), and the smaller particles, down, commonly referred to as the ``Brazil-nut problem'' or ``kinetic sieving.'' If the larger particles are sufficiently denser than the smaller particles, the segregation reverses. Using theory and simulations, we have recently shown that the segregation fluxes among particles differing in size only are driven by two effects: (1) the difference between the partitioning of kinetic and contact stresses among the species in the mixture and (2) a kinetic stress gradient. Specifically, the higher granular temperature of the smaller particles segregates them downward along a kinetic stress gradient toward lower temperatures, and larger particles upward. We adapt the theory to mixtures differing in both size and density and use simulations to show that when the larger particles are sufficiently dense, the theory captures the observed segregation reversal through a reversal in the relative granular temperature born by the two species. In other words, with increasing material density, the larger particles bear increasing fractions of the local kinetic stresses, and the segregation reverses as the larger particles bear a higher fraction than their local concentration in the mixture.

  17. Temperature gradients in a portion of Michigan: a review of the usefulness of data from the AAPG geothermal survey of North America

    SciTech Connect

    Vaught, T.L.

    1980-08-01

    Temperature gradient data derived from drill holes in an east-west zone through the center of the southern peninsula of Michigan are analyzed. The purpose of this work is to investigate possible problems in utilizing the American Association of Petroleum Geologists data base. Michigan was chosen because a review of that State's geothermal potential shows inconsistencies between gradients from shallow wells and nearby deeper wells and because the geology of the State is relativey simple. The structure and stratigraphy are discussed because an understanding of Michigan basin geology makes it easier to predict the influence of lithology on the basin's geothermal gradients. Explanations for elevated gradients are reviewed. (MHR)

  18. Shell properties of commercial clam Chamelea gallina are influenced by temperature and solar radiation along a wide latitudinal gradient

    PubMed Central

    Gizzi, Francesca; Caccia, Maria Giulia; Simoncini, Ginevra Allegra; Mancuso, Arianna; Reggi, Michela; Fermani, Simona; Brizi, Leonardo; Fantazzini, Paola; Stagioni, Marco; Falini, Giuseppe; Piccinetti, Corrado; Goffredo, Stefano

    2016-01-01

    Phenotype can express different morphologies in response to biotic or abiotic environmental influences. Mollusks are particularly sensitive to different environmental parameters, showing macroscale shell morphology variations in response to environmental parameters. Few studies concern shell variations at the different scale levels along environmental gradients. Here, we investigate shell features at the macro, micro and nanoscale, in populations of the commercially important clam Chamelea gallina along a latitudinal gradient (~400 km) of temperature and solar radiation in the Adriatic Sea (Italian cost). Six populations of clams with shells of the same length were analyzed. Shells from the warmest and the most irradiated population were thinner, with more oval shape, more porous and lighter, showing lower load fracture. However, no variation was observed in shell CaCO3 polymorphism (100% aragonite) or in compositional and textural shell parameters, indicating no effect of the environmental parameters on the basic processes of biomineralization. Because of the importance of this species as commercial resource in the Adriatic Sea, the experimentally quantified and significant variations of mass and fracture load in C. gallina shells along the latitudinal gradient may have economic implications for fisheries producing different economical yield for fishermen and consumers along the Adriatic coastline. PMID:27805037

  19. Land surface phenology and land surface temperature changes along an urban-rural gradient in Yangtze River Delta, china.

    PubMed

    Han, Guifeng; Xu, Jianhua

    2013-07-01

    Using SPOT/VGT NDVI time series images (2002-2009) and MODIS/LST images (2002-2009) smoothed by a Savitzky-Golay filter, the land surface phenology (LSP) and land surface temperature (LST), respectively, are extracted for six cities in the Yangtze River Delta, China, including Shanghai, Hangzhou, Nanjing, Changzhou, Wuxi, and Suzhou. The trends of the averaged LSP and LST are analyzed, and the relationship between these values is revealed along the urban-rural gradient. The results show that urbanization advances the start of the growing season, postpones the end of the growing season, prolongs the growing season length (GSL), and reduces the difference between maximal NDVI and minimal NDVI in a year (NDVIamp). More obvious changes occur in surface vegetation phenology as the urbanized area is approached. The LST drops monotonously and logarithmically along the urban-rural gradient. Urbanization generally affects the LSP of the surrounding vegetation within 6 km to the urban edge. Except for GSL, the difference in the LSP between urban and rural areas has a significant logarithmic relationship with the distance to the urban edge. In addition, there is a very strong linear relationship between the LSP and the LST along the urban-rural gradient, especially within 6 km to the urban edge. The correlations between LSP and gross domestic product and population density reveal that human activities have considerable influence on the land surface vegetation growth.

  20. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    PubMed Central

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-01-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-δ (BSCF-D) was prepared by simply treating porous Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) backbone with microwave-plasma. Electrochemical impedance spectroscopy reveals that the oxygen surface exchange rate of the BSCF-D is enhanced by ~250% that of the pristine BSCF due to the appearance of the shell. The heterostructured electrode shows an interfacial resistance as low as 0.148 Ω cm2 at 550°C and an unchanged electrochemical performance after heating treatment for 200 h. This method offers potential to prepare heterostructured oxides not only for electrochemical devices but also for many other applications that use ceramic materials. PMID:22355670

  1. Selecting the Proper Ceramic Material for a Regenerator Experiencing Large Temperature Gradients.

    DTIC Science & Technology

    1984-06-01

    TRANSPORT 57 4.2 SINTERING RATE AS A FUNCTION OF TEMPERATURE AND TIME 59 4.3 SINTERING RATE AS A FUNCTION OF LOGARITHMIC TEMPERATURE AND TIME 60...7 PAGE 4.4 MODEL FOR SINTERING PROCESS 62 -- 4.5 SCHEMATIC DRAWING OF POLYCRYSTALLINE SPECIMEN 67 4.6 ELEVATED TEMPERATURE STRENGTH OF SiC...VERSUS TIME 1/2 FOR SINTERED ALPHA SiC 85 4.12 OXIDATION ISOTHERMS FOR POLYCRYSXALLINE Sig IN OXYGEN AT TEMPERATURES FROM 1297 C TO 1697 C 86 4.13

  2. Scanning tunneling microscope-quartz crystal microbalance study of temperature gradients at an asperity contact.

    PubMed

    Pan, L; Krim, J

    2013-01-01

    Investigations of atomic-scale friction frequently involve setups where a tip and substrate are initially at different temperatures. The temperature of the sliding interface upon contact has thus become a topic of interest. A method for detecting initial tip-sample temperature differences at an asperity contact is described, which consists of a scanning tunneling microscope (STM) tip in contact with the surface electrode of a quartz crystal microbalance (QCM). The technique makes use of the fact that a QCM is extremely sensitive to abrupt changes in temperature. In order to demonstrate the technique's capabilities, QCM frequency shifts were recorded for varying initial tip-substrate temperature differences as an STM tip was brought into and out of contact. The results are interpreted within the context of a recent model for thermal heat conduction at an asperity contact, and it is concluded that the transient frequency response is attributable to small changes in temperature close to the region of contact rather than a change in the overall temperature of the QCM itself. For the assumed model parameters, the results moreover reveal substantial temperature discontinuities at the boundary between the tip and the sample, for example, on the order of 10-15 °C for initial temperature differences of 20 °C.

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

    PubMed

    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.

  4. Self-Action of Second Harmonic Generation and Longitudinal Temperature Gradient in Nonlinear-Optical Crystals

    NASA Astrophysics Data System (ADS)

    Baranov, A. I.; Konyashkin, A. V.; Ryabushkin, O. A.

    2015-09-01

    Model of second harmonic generation with thermal self-action was developed. Second harmonic generation temperature phase matching curves were measured and calculated for periodically polled lithium niobate crystal. Both experimental and calculated data show asymmetrical shift of temperature tuning curves with pump power.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Convective heat transfer studies at high temperatures with pressure gradient for inlet flow Mach number of 0.45

    NASA Technical Reports Server (NTRS)

    Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.

    1984-01-01

    Heat transfer measurements were determined for a flat plate with and without pressure gradient for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.

  7. The effect of temperature gradients on endocrine signaling and antioxidant gene expression during Chironomus riparius development.

    PubMed

    Park, Kiyun; Kwak, Ihn-Sil

    2014-02-01

    Temperature is one of the most important environmental factors affecting the biological processes of aquatic species. To investigate the potential effects of temperature on the developmental processes of aquatic invertebrates, we analyzed biological and molecular transcriptional responses during Chironomus riparius development, including five stages spanning from embryo to adult stages. We assessed the temperature change-induced reduction of survival rate, changes in biological development including the male:female ratio in emerged adults, the success rates of pupation and emergence, and the developmental timing of pupation and emergence. The increased temperature induced expression of endocrine signaling genes, such as the ecdysone receptor, ultraspiracle (ortholog of the RXR), and the estrogen-related receptor in the fourth-instar larval and pupal stages of C. riparius development. Altered temperature also affected the activity of antioxidant genes, including catalase, peroxidase, glutathione peroxidase, and superoxide dismutase during the fourth-instar larval to adult stages of C. riparius development, as a result of altered development. Increased temperature during the fourth-instar larval stage increased oxidative stress in pupae and adults. Responses of antioxidant genes to increased temperature occurred in a developmental stage-dependent manner. However, reduced temperature did not induce the expression of antioxidant genes in a developmental stage-dependent manner, although it did induce oxidative stress during C. riparius development. Increased temperature also caused greater toxicity of di-ethylhexyl phthalate (DEHP) in fourth-instar larvae. Our findings suggest that altered temperatures may disturb the invertebrate hormone system and developmental processes by inducing oxidative stress in aquatic environments.

  8. Thermographic visualization of the superficial vein and extravasation using the temperature gradient produced by the injected materials

    NASA Astrophysics Data System (ADS)

    Nakamura, Katsumasa; Sasaki, Tomonari; Ohga, Saiji; Yoshitake, Tadamasa; Terashima, Kotaro; Asai, Kaori; Matsumoto, Keiji; Shinoto, Makoto; Shioyama, Yoshiyuki; Nishie, Akihoro; Honda, Hiroshi

    2014-11-01

    There are few effective methods to detect or prevent the extravasation of injected materials such as chemotherapeutic agents and radiographic contrast materials. To investigate whether a thermographic camera could visualize the superficial vein and extravasation using the temperature gradient produced by the injected materials, an infrared thermographic camera with a high resolution of 0.04 °C was used. At the room temperature of 26 °C, thermal images and the time course of the temperature changes of a paraffin phantom embedded with rubber tubes (diameter 3.2 mm, wall thickness 0.8 mm) were evaluated after the tubes were filled with water at 15 °C or 25 °C. The rubber tubes were embedded at depths of 0 mm, 1.5 mm, and 3.0 mm from the surface of the phantom. Temperature changes were visualized in the areas of the phantom where the tubes were embedded. In general, changes were more clearly detected when greater temperature differences between the phantom and the water and shallower tube locations were employed. The temperature changes of the surface of a volunteer's arm were also examined after a bolus injection of physiological saline into the dorsal hand vein or the subcutaneous space. The injection of 5 ml room-temperature (26 °C) saline into the dorsal hand vein enabled the visualization of the vein. When 3 ml of room-temperature saline was injected through the vein into the subcutaneous space, extravasation was detected without any visualization of the vein. The subtraction image before and after the injection clearly showed the temperature changes induced by the saline. Thermography may thus be useful as a monitoring system to detect extravasation of the injected materials.

  9. Miniaturized Temperature Data Loggers for Deep Sea Sediment Temperature Gradient Measurements: Examples From TICOFLUX I and Cruises on R/V 'SONNE'

    NASA Astrophysics Data System (ADS)

    Pfender, M.; Villinger, H.; Fisher, A. T.; Silver, E.; Stein, C.; Harris, R. N.; Wheat, G.; Wang, K.; Cherkaoui, A.; Hutnak, M.; Friedmann, P.; Bodzin, R.; Cleary, R.

    2001-12-01

    The aim of the expedition 'TICOFLUX I' off Costa Rica margin was to determine the hydrothermal circulation pattern and the thermal state of the subducting plate seaward of the trench. The University of Bremen contributed to these investigations with a new probe for autonomous high precision temperature measurements which has been extensively tested during preceding expeditions. Our main application for these miniaturized temperature data loggers (MTLs) is the measurement of temperature gradients in deep sea by attaching the loggers on the outside walls of long lances, gravity or piston corers. The MTLs are extremely robust, small (17.3 cm long) and easy to operate in waterdepths up to 6000 m. The temperature range extends from -5 to +60 oC with a resolution of 1 mK. The absolute accuracy is +/-0.1 K and can be improved to several mK by a calibration with a high precision thermometer. Sampling rate and logging duration can be set independently from each other. With the non volatile memory of 64800 measurements and the highest sample rate of 1 s up to 18 hours of recording can be stored. To program the logger and download the data, the instrument is mounted into a read-out unit without opening the pressure case. During the cruise 'EW0104' we used the loggers as outriggers on a routine basis on 10 gravity and 6 piston corers. We derived reliable temperature gradients on all locations and will present the examples of records and processing in this poster. In addition, we will show pogo-style measurements where outriggers were mounted on a 6 m long lance. Our experience with these instruments is very positive so that the loggers can be recommended for a wide variety of marine science applications wherever a high precision temperature measurement is required.

  10. Influence of temperature gradients on partial pressures in a low-pressure chemical-vapor-deposition reactor

    NASA Astrophysics Data System (ADS)

    Oosterlaken, T. G. M.; Leusink, G. J.; Janssen, G. C. A. M.; Radelaar, S.; Kuijlaars, K. J.; Kleijn, C. R.; van den Akker, H. E. A.

    1994-09-01

    Measurements and calculations of the influence of temperature gradients on the partial pressures of the gas species in a cold-wall chemical-vapor-deposition reactor are presented. The experiments were performed at low pressures (300-500 Pa total pressure) and gas mixtures consisting of hydrogen, nitrogen, and tetrafluoromethane. The partial pressures were determined by Raman spectroscopy. The Soret effect (or thermal diffusion) has a large influence on the partial pressures of heavy gases in the vicinity of the heated wafer. In some cases a decrease in partial pressure of 20% compared to the inlet partial pressures was observed. Numerical calculations were performed to predict the behavior of the gas mixture. For mixtures under investigation the gas temperatures as well as the changes in partial pressures due to the Soret effect were predicted correctly.

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

    PubMed

    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.

  12. A dynamic response model for pressure sensors in continuum and high Knudsen number flows with large temperature gradients

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Petersen, Brian J.; Scott, David D.

    1996-01-01

    This paper develops a dynamic model for pressure sensors in continuum and rarefied flows with longitudinal temperature gradients. The model was developed from the unsteady Navier-Stokes momentum, energy, and continuity equations and was linearized using small perturbations. The energy equation was decoupled from momentum and continuity assuming a polytropic flow process. Rarefied flow conditions were accounted for using a slip flow boundary condition at the tubing wall. The equations were radially averaged and solved assuming gas properties remain constant along a small tubing element. This fundamental solution was used as a building block for arbitrary geometries where fluid properties may also vary longitudinally in the tube. The problem was solved recursively starting at the transducer and working upstream in the tube. Dynamic frequency response tests were performed for continuum flow conditions in the presence of temperature gradients. These tests validated the recursive formulation of the model. Model steady-state behavior was analyzed using the final value theorem. Tests were performed for rarefied flow conditions and compared to the model steady-state response to evaluate the regime of applicability. Model comparisons were excellent for Knudsen numbers up to 0.6. Beyond this point, molecular affects caused model analyses to become inaccurate.

  13. Numerical study of a buoyant plume from a multi-flue stack into a variable temperature gradient atmosphere.

    PubMed

    Velamati, Ratna Kishore; Vivek, M; Goutham, K; Sreekanth, G R; Dharmarajan, Santosh; Goel, Mukesh

    2015-11-01

    Air pollution is one of the major global hazards and industries have been one of its major contributors. This paper primarily focuses on analyzing the dispersion characteristics of buoyant plumes of the pollutant released from a multi-flue vertical stack into a variable temperature gradient atmosphere (α) in a constant-velocity cross wind using two stack configurations-inline and parallel. The study is conducted for different Froude numbers, Fr = 12.64, 9.55, and 8.27. The atmospheric temperature gradients considered for the study are 0, +1, +1.5, and +2 K/100 m. The numerical study is done using the commercial computational fluid dynamics (CFD) code FLUENT. The effects of stack configuration, α, and Fr on the plume characteristics are presented. It is observed that the plume rises higher and disperses over a larger area with the inline configuration due to better mixing and shielding effect. With higher α, it is seen that the plume rises initially and then descends due to variation of the buoyant force. The plume rise initially is strongly influenced by the momentum of the jet, and as it moves downstream, it is influenced by the cooling rate of the plume. Furthermore, the plume rises higher and disperses over a larger area with a decrease in Fr.

  14. Rapid concentration of deoxyribonucleic acid via Joule heating induced temperature gradient focusing in poly-dimethylsiloxane microfluidic channel.

    PubMed

    Ge, Zhengwei; Wang, Wei; Yang, Chun

    2015-02-09

    This paper reports rapid microfluidic electrokinetic concentration of deoxyribonucleic acid (DNA) with the Joule heating induced temperature gradient focusing (TGF) by using our proposed combined AC and DC electric field technique. A peak of 480-fold concentration enhancement of DNA sample is achieved within 40s in a simple poly-dimethylsiloxane (PDMS) microfluidic channel of a sudden expansion in cross-section. Compared to a sole DC field, the introduction of an AC field can reduce DC field induced back-pressure and produce sufficient Joule heating effects, resulting in higher concentration enhancement. Within such microfluidic channel structure, negative charged DNA analytes can be concentrated at a location where the DNA electrophoretic motion is balanced with the bulk flow driven by DC electroosmosis under an appropriate temperature gradient field. A numerical model accounting for a combined AC and DC field and back-pressure driven flow effects is developed to describe the complex Joule heating induced TGF processes. The experimental observation of DNA concentration phenomena can be explained by the numerical model.

  15. Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

    NASA Astrophysics Data System (ADS)

    Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

    1984-06-01

    To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

  16. Microzooplankton Growth Rates Examined across a Temperature Gradient in the Barents Sea

    PubMed Central

    Franzè, Gayantonia; Lavrentyev, Peter J.

    2014-01-01

    Growth rates (µ) of abundant microzooplankton species were examined in field experiments conducted at ambient sea temperatures (−1.8–9.0°C) in the Barents Sea and adjacent waters (70–78.5°N). The maximum species-specific µ of ciliates and athecate dinoflagellates (0.33–1.67 d−1 and 0.52–1.14 d−1, respectively) occurred at temperatures below 5°C and exceeded the µmax predicted by previously published, laboratory culture-derived equations. The opposite trend was found for thecate dinoflagellates, which grew faster in the warmer Atlantic Ocean water. Mixotrophic ciliates and dinoflagellates grew faster than their heterotrophic counterparts. At sub-zero temperatures, microzooplankton µmax matched those predicted for phytoplankton by temperature-dependent growth equations. These results indicate that microzooplankton protists may be as adapted to extreme Arctic conditions as their algal prey. PMID:24475119

  17. Influence of fluid temperature gradient on the flow within the shaft gap of a PLR pump

    NASA Astrophysics Data System (ADS)

    Qian, W.; Rosic, B.; Zhang, Q.; Khanal, B.

    2016-03-01

    In nuclear power plants the primary-loop recirculation (PLR) pump circulates the high temperature/high-pressure coolant in order to remove the thermal energy generated within the reactor. The pump is sealed using the cold purge flow in the shaft seal gap between the rotating shaft and stationary casing, where different forms of Taylor-Couette flow instabilities develop. Due to the temperature difference between the hot recirculating water and the cold purge water (of order of 200 °C), the flow instabilities in the gap cause temperature fluctuations, which can lead to shaft or casing thermal fatigue cracks. The present work numerically investigated the influence of temperature difference and rotating speed on the structure and dynamics of the Taylor-Couette flow instabilities. The CFD solver used in this study was extensively validated against the experimental data published in the open literature. Influence of temperature difference on the fluid dynamics of Taylor vortices was investigated in this study. With large temperature difference, the structure of the Taylor vortices is greatly stretched at the interface region between the annulus gap and the lower recirculating cavity. Higher temperature difference and rotating speed induce lower fluctuating frequency and smaller circumferential wave number of Taylor vortices. However, the azimuthal wave speed remains unchanged with all the cases tested. The predicted axial location of the maximum temperature fluctuation on the shaft is in a good agreement with the experimental data, identifying the region potentially affected by the thermal fatigue. The physical understandings of such flow instabilities presented in this paper would be useful for future PLR pump design optimization.

  18. Local adaptation and evolutionary potential along a temperature gradient in the fungal pathogen Rhynchosporium commune

    PubMed Central

    Stefansson, Tryggvi S; McDonald, Bruce A; Willi, Yvonne

    2013-01-01

    To predict the response of plant pathogens to climate warming, data are needed on current thermal adaptation, the pathogen's evolutionary potential, and the link between them. We conducted a common garden experiment using isolates of the fungal pathogen Rhynchosporium commune from nine barley populations representing climatically diverse locations. Clonal replicates of 126 genetically distinct isolates were assessed for their growth rate at 12°C, 18°C, and 22°C. Populations originating from climates with higher monthly temperature variation had higher growth rate at all three temperatures compared with populations from climates with less temperature fluctuation. Population differentiation in growth rate (QST) was significantly higher at 22°C than population differentiation for neutral microsatellite loci (GST), consistent with local adaptation for growth at higher temperatures. At 18°C, we found evidence for stabilizing selection for growth rate as QST was significantly lower than GST. Heritability of growth rate under the three temperatures was substantial in all populations (0.58–0.76). Genetic variation was lower in populations with higher growth rate at the three temperatures and evolvability increased under heat stress in seven of nine populations. Our findings imply that the distribution of this pathogen is unlikely to be genetically limited under climate warming, due to its high genetic variation and plasticity for thermal tolerance. PMID:23745143

  19. Reproductive Efficiency of a Mediterranean Endemic Zooxanthellate Coral Decreases with Increasing Temperature along a Wide Latitudinal Gradient

    PubMed Central

    Airi, Valentina; Gizzi, Francesca; Falini, Giuseppe; Levy, Oren; Dubinsky, Zvy; Goffredo, Stefano

    2014-01-01

    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. PMID:24618568

  20. Full-field measurement of surface topographies and thin film stresses at elevated temperatures by digital gradient sensing method.

    PubMed

    Zhang, Changxing; Qu, Zhe; Fang, Xufei; Feng, Xue; Hwang, Keh-Chih

    2015-02-01

    Thin film stresses in thin film/substrate systems at elevated temperatures affect the reliability and safety of such structures in microelectronic devices. The stresses result from the thermal mismatch strain between the film and substrate. The reflection mode digital gradient sensing (DGS) method, a real-time, full-field optical technique, measures deformations of reflective surface topographies. In this paper, we developed this method to measure topographies and thin film stresses of thin film/substrate systems at elevated temperatures. We calibrated and compensated for the air convection at elevated temperatures, which is a serious problem for optical techniques. We covered the principles for surface topography measurements by the reflection mode DGS method at elevated temperatures and the governing equations to remove the air convection effects. The proposed method is applied to successfully measure the full-field topography and deformation of a NiTi thin film on a silicon substrate at elevated temperatures. The evolution of thin film stresses obtained by extending Stoney's formula implies the "nonuniform" effect the experimental results have shown.

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

    NASA Technical Reports Server (NTRS)

    Rashidnia, N.; Balasubramaniam, R.

    1989-01-01

    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).

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

    NASA Technical Reports Server (NTRS)

    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).

  3. A Simulation Model for the Toroidal Ion Temperature Gradient Instability with Fully Kinetic Ions

    NASA Astrophysics Data System (ADS)

    Sturdevant, Benjamin; Parker, Scott; Chen, Yang

    2016-10-01

    A simulation model for the toroidal ITG mode in which the ions follow the primitive Lorentz force equations of motion is presented. Such a model can provide an important validation tool or replacement for gyrokinetic ion models in applications where higher order terms may be important. A number of multiple-scale simulation techniques are employed in this work, based on the previous success in slab geometry with an implicit orbit averaged and sub-cycled δf model. For the toroidal geometry model, we have derived a particle integration scheme based on variational principles, which is demonstrated to produce stable and accurate ion trajectories on long time scales. Orbit averaging and sub-cycling will be implemented with the variational integration scheme. The inclusion of equilibrium gradients in the fully kinetic δf formulation is achieved through the use of a guiding center coordinate transformation of the weight equation. Simulation results for the fully kinetic ion model will be presented for the cyclone base case and comparisons will be made with gyrokinetic ion models.

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

    NASA Astrophysics Data System (ADS)

    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

  5. On the motion of a solid sphere through a viscous medium with a vertical temperature gradient

    NASA Astrophysics Data System (ADS)

    Wozniak, G.; Balasubramaniam, R.; Koukan, E.

    In this paper, we report experiments conducted on the temperature distribution around a solid sphere that settles slowly in a thermally stratified viscous fluid. The temperature field has been obtained using interferometry. In some cases thermochromic liquid crystal tracers have been used to simultaneously obtain the velocity and the temperature fields. We also describe a theoretical analysis of the problem and compare experimental and theoretical findings and discuss the results. we find that natural convection has a significant influence in determining the nature of the temperature field away from the sphere. Zusammenfassung In der vorliegenden Arbeit berichten wir über Experimente mit festen Kugeln, welche sich in einem thermisch geschichteten viskosen Fluid langsam nach unten bewegen. Das Temperaturfeld wurde mit Hilfe der Interferometrie bestimmt, in einigen Fällen auch mit thermochromen Flüssigkristall-Teilchen. Auch eine theoretische Analyse wird beschrieben. Experimentelle Resultate werden den theoretischen Daten gegenüber gestellt und die Ergebnisse diskutiert. Es zeigt sich, daß natürliche Konvektion einen erheblichen Einfluß bei der Bestimmung des Temperaturfeldcharakters außerhalb der Kugel hat.

  6. Geometrical gradients in the distribution of temperature and absorbed ultraviolet radiation in ocular tissues.

    PubMed

    Sliney, David H

    2002-01-01

    The geographical variations in the incidence of age-related ocular changes such as presbyopia and cataracts and diseases such as pterygium and droplet keratopathies have led to theories pointing to sunlight, ultraviolet radiation (UVR) exposure and ambient temperature as potential etiological factors. Some epidemiological evidence also points to an association of age-related macular degeneration to sunlight exposure. The actual distribution of sunlight exposure and the determination of temperature variations of different tissues within the anterior segment of the eye are difficult to assess. Of greatest importance are the geometrical factors that influence selective UVR exposures to different segments of the lens, cornea and retina. Studies show that the temperature of the lens and cornea varies by several degrees depending upon climate, and that the incidence of nuclear cataract incidence is greater in areas of higher ambient temperature (i.e., in the tropics). Likewise, sunlight exposure to local areas of the cornea, lens and retina varies greatly in different environments. However, epidemiological studies of the influence of environmental UVR in the development of cataract, pterygium, droplet keratopathies and age-related macular degeneration have produced surprisingly inconsistent findings. The lack of consistent results is seen to be due largely to either incomplete or erroneous estimates of outdoor UV exposure dose. Geometrical factors dominate the determination of UVR exposure of the eye. The degree of lid opening limits ocular exposure to rays entering at angles near the horizon. Clouds redistribute overhead UVR to the horizon sky. Mountains, trees and building shield the eye from direct sky exposure. Most ground surfaces reflect little UVR. The result is that highest UVR exposure occurs during light overcast where the horizon is visible and ground surface reflection is high. By contrast, exposure in a high mountain valley (lower ambient temperature) with

  7. Inferred calcification rate of a Mediterranean azooxanthellate coral is uncoupled with sea surface temperature along an 8° latitudinal gradient

    PubMed Central

    2012-01-01

    Introduction Correlations between sea surface temperature (SST) and growth parameters of the solitary azooxanthellate Dendrophylliid Leptopsammia pruvoti were assessed along an 8° latitudinal gradient on western Italian coasts (Mediterranean Sea), to check for possible negative effects of increasing temperature as the ones reported for a closely related, sympatric but zooxanthellate species. Results Calcification rate was correlated with skeletal density but not with linear extension rate, indicating that calcium carbonate deposition was preferentially allocated to keep a constant skeletal density. Unlike most studies on both temperate and tropical zooxanthellate corals, where calcification rate is strongly related to environmental parameters such as SST, in the present study calcification rate was not correlated with SST. Conclusions The lower sensitivity of L. pruvoti to SST with respect to other sympatric zooxanthellate corals, such as Balanophyllia europaea, may rely on the absence of a temperature induced inhibition of photosynthesis, and thus the absence of an inhibition of the calcification process. This study is the first field investigation of the relationship between SST and the three growth parameters of an azooxanthellate coral. Increasing research effort on determining the effects of temperature on biological traits of the poorly studied azooxanthellate scleractinians may help to predict the possible species assemblage shifts that are likely to occur in the immediate future as a consequence of global climatic change. PMID:23163981

  8. Temperature gradients in XMM-Newton observed REFLEX-DXL galaxy clusters at z ˜ 0.3

    NASA Astrophysics Data System (ADS)

    Zhang, Y.-Y.; Finoguenov, A.; Böhringer, H.; Ikebe, Y.; Matsushita, K.; Schuecker, P.

    2004-01-01

    We present XMM-Newton results on the temperature profiles of a volume-limited sample of galaxy clusters at redshifts z˜0.3, selected from the REFLEX survey (REFLEX-DXL sample). In the spectral analysis, where only the energies above 1 keV were considered, we obtained consistent results for the temperature derived from the pn, MOS1 and MOS2 data. Useful temperature measurements could be performed out to radii with overdensity 500 (r500) for all nine clusters. We discovered a diversity in the temperature gradients at the outer cluster radii with examples of both flat and strongly decreasing profiles. Using the total mass and the gas mass profiles for the cluster RXCJ0307.0-2840 we demonstrate that the errors on the mass estimates for the REFLEX-DXL clusters are within 25% up to r500. This work is based on observations made with the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA).

  9. Bioenergetic modeling reveals that Chinese green tree vipers select postprandial temperatures in laboratory thermal gradients that maximize net energy intake.

    PubMed

    Tsai, Tein-Shun; Lee, How-Jing; Tu, Ming-Chung

    2009-11-01

    With bioenergetic modeling, we tested the hypothesis that reptiles maximize net energy gain by postprandial thermal selection. Previous studies have shown that Chinese green tree vipers (Trimeresurus s. stejnegeri) have postprandial thermophily (mean preferred temperature T(p) for males =27.8 degrees C) in a linear thigmothermal gradient when seclusion sites and water existed. With some published empirical models of digestion associated factors for this snake, we calculated the average rate (E(net)) and efficiency (K(net)) of net energy gain from possible combinations of meal size, activity level, and feeding frequency at each temperature. The simulations consistently revealed that E(net) maximizes at the T(p) of these snakes. Although the K(net) peaks at a lower temperature than E(net), the value of K(net) remains high (>=0.85 in ratio to maximum) at the peak temperature of E(net). This suggested that the demands of both E(net) and K(net) can be attained by postprandial thermal selection in this snake. In conclusion, the data support our prediction that postprandial thermal selection may maximize net energy gain.

  10. Low Temperature Geomicrobiology Follows Host Rock Composition Along a Geochemical Gradient in Lau Basin

    PubMed Central

    Sylvan, Jason B.; Sia, Tiffany Y.; Haddad, Amanda G.; Briscoe, Lindsey J.; Toner, Brandy M.; Girguis, Peter R.; Edwards, Katrina J.

    2013-01-01

    The East Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle chemistry manifest themselves as gradients in seafloor rock geochemistry. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected, from north to south, at the vent fields Kilo Moana, ABE, Tui Malila, and Mariner. This is the first study of microbial populations on basaltic andesite, which was sampled at Mariner vent field. Silicate rock geochemistry exhibits clear latitudinal trends that are mirrored by changes in bacterial community composition. α-proteobacteria, ε-proteobacteria, and Bacteroidetes are most common on a silicate collected from Kilo Moana and their proportions decrease linearly on silicates collected further south. Conversely, a silicate from Mariner vent field hosts high proportions of a unique lineage of Chloroflexi unrelated (<90% sequence similarity) to previously recovered environmental clones or isolates, which decrease at ABE and are absent at Kilo Moana. The exteriors of inactive sulfide structures are dominated by lineages of sulfur oxidizing α-proteobacteria, γ-proteobacteria, and ε-proteobacteria, while the interior of one chimney is dominated by putative sulfur-reducing δ-proteobacteria. A comparison of bacterial communities on inactive sulfides from this and previous studies reveals the presence of a clade of uncultured Bacteroidetes exclusive to sulfidic environments, and a high degree of heterogeneity in bacterial community composition from one sulfide structure to another. In light of the heterogeneous nature of bacterial communities observed here and in previous studies of both active and inactive hydrothermal sulfide structures, the presence of numerous niches may be detected on these structures in the future by finer scale sampling and analysis. PMID:23543862

  11. Low temperature geomicrobiology follows host rock composition along a geochemical gradient in lau basin.

    PubMed

    Sylvan, Jason B; Sia, Tiffany Y; Haddad, Amanda G; Briscoe, Lindsey J; Toner, Brandy M; Girguis, Peter R; Edwards, Katrina J

    2013-01-01

    The East Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle chemistry manifest themselves as gradients in seafloor rock geochemistry. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected, from north to south, at the vent fields Kilo Moana, ABE, Tui Malila, and Mariner. This is the first study of microbial populations on basaltic andesite, which was sampled at Mariner vent field. Silicate rock geochemistry exhibits clear latitudinal trends that are mirrored by changes in bacterial community composition. α-proteobacteria, ε-proteobacteria, and Bacteroidetes are most common on a silicate collected from Kilo Moana and their proportions decrease linearly on silicates collected further south. Conversely, a silicate from Mariner vent field hosts high proportions of a unique lineage of Chloroflexi unrelated (<90% sequence similarity) to previously recovered environmental clones or isolates, which decrease at ABE and are absent at Kilo Moana. The exteriors of inactive sulfide structures are dominated by lineages of sulfur oxidizing α-proteobacteria, γ-proteobacteria, and ε-proteobacteria, while the interior of one chimney is dominated by putative sulfur-reducing δ-proteobacteria. A comparison of bacterial communities on inactive sulfides from this and previous studies reveals the presence of a clade of uncultured Bacteroidetes exclusive to sulfidic environments, and a high degree of heterogeneity in bacterial community composition from one sulfide structure to another. In light of the heterogeneous nature of bacterial communities observed here and in previous studies of both active and inactive hydrothermal sulfide structures, the presence of numerous niches may be detected on these structures in the future by finer scale sampling and analysis.

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

    PubMed

    Hu, Zhaoyong; Wang, Genxu; Sun, Xiangyang

    2017-03-09

    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.

  13. Modelling of ultrasonic propagation in turbulent liquid sodium with temperature gradient

    SciTech Connect

    Massacret, N.; Moysan, J. Ploix, M. A.; Corneloup, G.; Jeannot, J. P.

    2014-05-28

    The use of ultrasonic instrumentation in sodium-cooled fast reactors requires to understand and to predict how ultrasonic waves can be deflected, slowed down or speeded up, depending on the thermo-hydraulic characteristics of the liquid sodium. These thermo-hydraulic characteristics are mainly the local temperature and flow speed of the sodium. In this study we show that ray theory can be used to simulate ultrasonic propagation in a medium similar to the core of a sodium-cooled fast reactor, in order to study ultrasonic instrumentation and prepare it installation and utilisation in the sodium of the nuclear reactor. A suitable model has been developed and a set of thermo-hydraulics data has been created, taking account of the particularities of the sodium flow. The results of these simulations are then analysed within the framework of acoustic thermometry, in order to determine which disturbance must be taken into account for the correct operation of the temperature measurement.

  14. Modelling of ultrasonic propagation in turbulent liquid sodium with temperature gradient

    NASA Astrophysics Data System (ADS)

    Massacret, N.; Moysan, J.; Ploix, M. A.; Jeannot, J. P.; Corneloup, G.

    2014-05-01

    The use of ultrasonic instrumentation in sodium-cooled fast reactors requires to understand and to predict how ultrasonic waves can be deflected, slowed down or speeded up, depending on the thermo-hydraulic characteristics of the liquid sodium. These thermo-hydraulic characteristics are mainly the local temperature and flow speed of the sodium. In this study we show that ray theory can be used to simulate ultrasonic propagation in a medium similar to the core of a sodium-cooled fast reactor, in order to study ultrasonic instrumentation and prepare it installation and utilisation in the sodium of the nuclear reactor. A suitable model has been developed and a set of thermo-hydraulics data has been created, taking account of the particularities of the sodium flow. The results of these simulations are then analysed within the framework of acoustic thermometry, in order to determine which disturbance must be taken into account for the correct operation of the temperature measurement.

  15. ac-Field-induced fluid pumping in microsystems with asymmetric temperature gradients.

    PubMed

    Holtappels, Moritz; Stubbe, Marco; Gimsa, Jan

    2009-02-01

    We present two different designs of electrohydrodynamic micropumps for microfluidic systems. The micropumps have no movable parts, and their simple design allows for fabrication by microsystems technology. The pumps are operated by ac voltages from 1 to 60 V and were tested with aqueous solutions in the conductivity range of 1-112 mS m(-1). The pump effect is induced by an ac electric field across a fluid medium with an inhomogeneous temperature distribution. It is constant over a wide range of the ac field frequency with a conductivity-dependent drop-off at high frequencies. The temperature-dependent conductivity and permittivity distributions in the fluid induce space charges that interact with the electric field and induce fluid motion. The temperature distribution can be generated either by Joule heating in the medium or by external heating. We present experimental results obtained with two prototypes featuring Joule heating and external heating by a heating filament. Experimental and numerical results are compared with an analytical model.

  16. Metabolic and embryonic responses to terrestrial incubation of Fundulus grandis embryos across a temperature gradient.

    PubMed

    Brown, C A; Green, C C

    2014-03-01

    This study simulated terrestrial incubation and measured rates of embryogenesis, nitrogen elimination, heart rate, lactate production, maximum length of time a hatch could be delayed and developmental responses of terrestrially incubated Gulf killifish Fundulus grandis embryos at temperatures ranging from 20 to 30° C. Temperature had a positive relationship with rate of embryogenesis, but a negative relationship with extent of extended incubation. The 30° C treatment reached embryonic maturity 6 days before the 20° C treatment. Embryos hatched between intervals of 240 and 336, 144 and 288, 96 and 240 and 96 and 192 h after reaching developmental maturity for the 20, 23, 26 and 30° C treatments. Significantly higher concentrations of total nitrogen, in the form of ammonia and urea, were recorded in the 20 and 30° C treatments. While temperature significantly influenced lactate and ATP concentrations, no significant influence of time of incubation was detected. Terrestrial embryos displayed an ability to develop quickly during embryogenesis and prolong incubation for an extended period of time after reaching embryonic maturity. This adaptation may be a life-history trait used to minimize asynchronous hatching, cannibalism and cohort size heterogeneity.

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

    PubMed Central

    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. PMID:27835651

  18. A map of the large day-night temperature gradient of a super-Earth exoplanet

    NASA Astrophysics Data System (ADS)

    Demory, Brice-Olivier; Gillon, Michael; de Wit, Julien; Madhusudhan, Nikku; Bolmont, Emeline; Heng, Kevin; Kataria, Tiffany; Lewis, Nikole; Hu, Renyu; Krick, Jessica; Stamenković, Vlada; Benneke, Björn; Kane, Stephen; Queloz, Didier

    2016-04-01

    Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths—exoplanets with masses of one to ten times that of Earth—have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e (refs 4, 5) revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 ± 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1,380 ± 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1,300 kelvin hotter (2,700 ± 270 kelvin) at a wavelength of 4.5 micrometres, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface.

  19. A map of the large day-night temperature gradient of a super-Earth exoplanet.

    PubMed

    Demory, Brice-Olivier; Gillon, Michael; de Wit, Julien; Madhusudhan, Nikku; Bolmont, Emeline; Heng, Kevin; Kataria, Tiffany; Lewis, Nikole; Hu, Renyu; Krick, Jessica; Stamenković, Vlada; Benneke, Björn; Kane, Stephen; Queloz, Didier

    2016-04-14

    Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths--exoplanets with masses of one to ten times that of Earth--have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e (refs 4, 5) revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 ± 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1,380 ± 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1,300 kelvin hotter (2,700 ± 270 kelvin) at a wavelength of 4.5 micrometres, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface.

  20. Native rainbow smelt and nonnative alewife distribution related to temperature and light gradients in Lake Champlain

    USGS Publications Warehouse

    Parrish, Donna; Simonin, Paul W.; Rudstam, Lars G.; Sullivan, Patrick J.; Pientka, Bernard

    2012-01-01

    Alewife (Alosa pseudoharengus) recently became established in Lake Champlain and may compete with native rainbow smelt (Osmerus mordax) for food or consume larval rainbow smelt. The strength of this effect depends partly on the spatial and temporal overlap of different age groups of the two species; therefore, we need a better understanding of factors affecting alewife and rainbow smelt distributions in Lake Champlain. We used hydroacoustics, trawls, and gill nets to document vertical fish distribution, and recorded environmental data during 16 day–night surveys over two years. Temperature, temperature change, and light were all predictors of adult and age-0 rainbow smelt distribution, and temperature and light were predictors of age-0 alewives' distribution (based on GAMM models evaluated with AIC). Adult alewives were 5–30 m shallower and age-0 alewives were 2–15 m shallower than their rainbow smelt counterparts. Adult rainbow smelt distribution overlapped with age-0 rainbow smelt and age-0 alewives near the thermocline (10–25 m), whereas adult alewives were shallower (0–6 m) and overlapped with age-0 alewives and rainbow smelt in the epilimnion. Adult rainbow smelt were in water < 10–12 °C, whereas age-0 rainbow smelt were in 10–20 °C, and adult and age-0 alewives were in 15–22 °C water. Predicting these species distributions is necessary for quantifying the strength of predatory and competitive interactions between alewife and rainbow smelt, as well as between alewife and other fish species in Lake Champlain.

  1. Lamb wave Propagation in Functionally Graded Piezoelectric Material Created by Internal Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Dammak, Y.; Thomas, J. H.; Ghozlen, M. H. Ben

    This work presents a theoretical study of the propagation behavior of lamb wave in a functionally graded piezoelectric material (FGPM). The piezoelectric material is polarized when the six fold symmetry axis is put along the propagation direction x1 and the material properties change gradually perpendicularly to the plate. The FGPM behavior is created by forming a temperature variation across the plate. The ordinary differential equation (ODE) and the Stiffness Matrix Method (SMM) are used to investigate the propagation of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb wave modes.

  2. Momentum transport in the vicinity of q{sub min} in reverse shear tokamaks due to ion temperature gradient turbulence

    SciTech Connect

    Singh, Rameswar; Singh, R; Jhang, Hogun; Diamond, P. H.

    2014-01-15

    We present an analytic study of momentum transport of tokamak plasmas in the vicinity of minimum safety factor (q) position in reversed magnetic shear configuration. Slab ion temperature gradient modes with an equilibrium flow profile are considered in this study. Quasi-linear calculations of momentum flux clearly show the novel effects of q-curvature on the generation of intrinsic rotation and mean poloidal flow without invoking reflectional symmetry breaking of parallel wavenumber (k{sub ∥}). This q-curvature effect originates from the inherent asymmetry in k{sub ∥} populations with respect to a rational surface due to the quadratic proportionality of k{sub ∥} when q-curvature is taken into account. Discussions are made of possible implications of q-curvature induced plasma flows on internal transport barrier formation in reversed shear tokamaks.

  3. Patterns in Temporal Variability of Temperature, Oxygen and pH along an Environmental Gradient in a Coral Reef

    PubMed Central

    Guadayol, Òscar; Silbiger, Nyssa J.; Donahue, Megan J.; Thomas, Florence I. M.

    2014-01-01

    Spatial and temporal environmental variability are important drivers of ecological processes at all scales. As new tools allow the in situ exploration of individual responses to fluctuations, ecologically meaningful ways of characterizing environmental variability at organism scales are needed. We investigated the fine-scale spatial heterogeneity of high-frequency temporal variability in temperature, dissolved oxygen concentration, and pH experienced by benthic organisms in a shallow coastal coral reef. We used a spatio-temporal sampling design, consisting of 21 short-term time-series located along a reef flat-to-reef slope transect, coupled to a long-term station monitoring water column changes. Spectral analyses revealed sharp gradients in variance decomposed by frequency, as well as differences between physically-driven and biologically-reactive parameters. These results highlight the importance of environmental variance at organismal scales and present a new sampling scheme for exploring this variability in situ. PMID:24416364

  4. Temperature gradient-induced fluid pumping inside a single-wall carbon nanotube: A non-equilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Faraji, Fahim; Rajabpour, Ali

    2016-09-01

    In this paper we investigate the fluid transport inside a single-wall carbon nanotube induced by a temperature gradient along the tube length, focusing on the effect of fluid-wall interaction strength. It is found that the fluid moves from the hot side of the nanotube towards the cold side. By increasing the fluid-wall interaction strength, the fluid volumetric flux assumes a maximum, increases, and then decreases. Fluid transport is pressure-driven in weak interactions; in contrast, in strong interactions, the fluid is broken into two parts in the radial direction. Fluid transport in the central regions of the tube is pressure-driven, while it is surface-driven in the areas close to the wall.

  5. Phenotypic Plasticity of Leaf Shape along a Temperature Gradient in Acer rubrum

    PubMed Central

    Royer, Dana L.; Meyerson, Laura A.; Robertson, Kevin M.; Adams, Jonathan M.

    2009-01-01

    Both phenotypic plasticity and genetic determination can be important for understanding how plants respond to environmental change. However, little is known about the plastic response of leaf teeth and leaf dissection to temperature. This gap is critical because these leaf traits are commonly used to reconstruct paleoclimate from fossils, and such studies tacitly assume that traits measured from fossils reflect the environment at the time of their deposition, even during periods of rapid climate change. We measured leaf size and shape in Acer rubrum derived from four seed sources with a broad temperature range and grown for two years in two gardens with contrasting climates (Rhode Island and Florida). Leaves in the Rhode Island garden have more teeth and are more highly dissected than leaves in Florida from the same seed source. Plasticity in these variables accounts for at least 6–19 % of the total variance, while genetic differences among ecotypes probably account for at most 69–87 %. This study highlights the role of phenotypic plasticity in leaf-climate relationships. We suggest that variables related to tooth count and leaf dissection in A. rubrum can respond quickly to climate change, which increases confidence in paleoclimate methods that use these variables. PMID:19893620

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

    NASA Astrophysics Data System (ADS)

    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 < 10-6 m3 s-1 while during increased mass flow rates the water vapor 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.

  7. A novel bisulfite-microfluidic temperature gradient capillary electrophoresis platform for highly sensitive detection of gene promoter methylation.

    PubMed

    Zhang, Huidan; Shan, Lianfeng; Wang, Xiaonan; Ma, Qian; Fang, Jin

    2013-04-15

    The hypermethylated tumor suppressor gene promoters are widely recognized as promising markers for cancer screening and ideal targets for cancer therapy, however, a major obstacle in their clinical study is highly sensitive screening. To address this limitation, we developed a novel bisulfite-microfluidic temperature gradient capillary electrophoresis (bisulfite-μTGCE) platform for gene methylation analysis by combining bisulfite treatment and slantwise radiative heating system-based μTGCE. Bisulfite-treated genomic DNA (gDNA) was amplified with universal primers for both methylated and unmethylated sequences, and introduced into glass microfluidic chip to perform electrophorectic separation under a continuous temperature gradient based on the formation of heteroduplexes. Eight CDKN2A promoter model fragments with different number and location of methylation sites were prepared and successfully analyzed according to their electrophoretic peak patterns, with high stability, picoliter-scale sample consumption, and significantly increased detection speed. The bisulfite-μTGCE could detect methylated gDNA with a detection limit of 7.5pg, and could distinguish as low as 0.1% methylation level in CDKN2A in an unmethylated background. Detection of seven colorectal cancer (CRC) cell lines with known and unknown methylation statuses of CDKN2A promoter and 20 tumor tissues derived from CRC patients demonstrated the capability of detecting hypermethylation in real-world samples. The wider adaptation of this platform was further supported by the detection of the CDKN2A and MLH1 promoters' methylation statuses in combination. This highly sensitive, fast, and low-consumption platform for methylation detection shows great potential for future clinical applications.

  8. Non-modal theory of the kinetic ion temperature gradient driven instability of plasma shear flows across the magnetic field

    NASA Astrophysics Data System (ADS)

    Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June

    2016-06-01

    The temporal evolution of the kinetic ion temperature gradient driven instability and of the related anomalous transport of the ion thermal energy of plasma shear flow across the magnetic field is investigated analytically. This instability develops in a steady plasma due to the inverse ion Landau damping and has the growth rate of the order of the frequency when the ion temperature is equal to or above the electron temperature. The investigation is performed employing the non-modal methodology of the shearing modes which are the waves that have a static spatial structure in the frame of the background flow. The solution of the governing linear integral equation for the perturbed potential displays that the instability experiences the non-modal temporal evolution in the shearing flow during which the unstable perturbation becomes very different from a canonical modal form. It transforms into the non-modal structure with vanishing frequency and growth rate with time. The obtained solution of the nonlinear integral equation, which accounts for the random scattering of the angle of the ion gyro-motion due to the interaction of ions with ensemble of shearing waves, reveals similar but accelerated process of the transformations of the perturbations into the zero frequency structures. It was obtained that in the shear flow the anomalous ion thermal conductivity decays with time. It is a strictly non-modal effect, which originates from the temporal evolution of the shearing modes turbulence.

  9. Effect of electric field and temperature gradient on the orientational dynamics of liquid crystals in a microvolume cylindrical cavity

    NASA Astrophysics Data System (ADS)

    Zakharov, A. V.; Vakulenko, A. A.; Romano, Silvano

    2009-10-01

    We have considered a homogeneously aligned liquid crystal (HALC) microvolume confined between two infinitely long horizontal coaxial cylinders and investigated dynamic field pumping, i.e., studied the interactions between director, velocity, and electric E fields as well as a radially applied temperature gradient ∇T, where the inner cylinder is kept at a lower temperature than the outer one. In order to elucidate the role of ∇T in producing hydrodynamic flow u, we have carried out a numerical study of a system of hydrodynamic equations including director reorientation, fluid flow, and temperature redistribution across the HALC cavity. Calculations show that only under the influence of ∇T does the initially quiescent HALC sample settle down to a stationary flow regime with horizontal component of velocity ueq(r). The effects of ∇T and of the size of the HALC cavity on magnitude and direction of ueq(r) have been investigated for a number of hydrodynamic regimes. Calculations also showed that E influences only the director redistribution across the HALC but not the magnitude of the velocity ueq(r).

  10. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through Tc

    NASA Astrophysics Data System (ADS)

    Huang, Shichun; Kubo, Takayuki; Geng, R. L.

    2016-08-01

    Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80 K /m are studied under various applied magnetic fields from 5 to 20 μ T . We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity rfl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of d T /d s dependence of Rfl/Ba are also discussed.

  11. Temperature gradients due to adiabatic plasma expansion in a magnetic nozzle

    NASA Astrophysics Data System (ADS)

    Sheehan, J. P.; Longmier, B. W.; Bering, E. A.; Olsen, C. S.; Squire, J. P.; Ballenger, M. G.; Carter, M. D.; Cassady, L. D.; Díaz, F. R. Chang; Glover, T. W.; Ilin, A. V.

    2014-08-01

    A mechanism for ambipolar ion acceleration in a magnetic nozzle is proposed. The plasma is adiabatic (i.e., does not exchange energy with its surroundings) in the diverging section of a magnetic nozzle so any energy lost by the electrons must be transferred to the ions via the electric field. Fluid theory indicates that the change in plasma potential is proportional to the change in average electron energy. These predictions were compared to measurements in the VX-200 experiment which has conditions conducive to ambipolar ion acceleration. A planar Langmuir probe was used to measure the plasma potential, electron density, and electron temperature for a range of mass flow rates and power levels. Axial profiles of those parameters were also measured, showing consistency with the adiabatic ambipolar fluid theory.

  12. The effect of zonal gradients of sea surface temperature on the Indian Ocean winter monsoon

    NASA Technical Reports Server (NTRS)

    Cohen, C.

    1981-01-01

    Several global climate simulations by the 7-layer, 8 x 10 GISS climate model were designed to test the contributions of various surface boundary conditions to the global climate. The model was run with the sun fixed at a perpetual January. In a comparison of run #5, in which realistic January surface boundary conditions were used, with run #4, which was the same except that a zonally symmetric climatological January sea surface temperature (SST) field was used, one of the results was that run #5 provided a better simulation of the Indian Ocean monsoon. A further comparison of the wind fields over the Indian Ocean that were generated by these two model runs is presented.

  13. Length Scales of Local Glass Transition Temperature Gradients Near Soft and Hard Polymer-Polymer Interfaces

    NASA Astrophysics Data System (ADS)

    Baglay, Roman; Roth, Connie

    Polymer-polymer interfaces are ubiquitous in polymer blends and block copolymers, while opening up another avenue for the study of interfacial perturbations to the local glass transition temperature Tg(z). We have previously reported the full local Tg(z) profile across a glassy-rubbery polymer interface between polystyrene (PS) and poly(n-butyl methacrylate) (PnBMA), an 80 K difference in bulk Tg [Baglay & Roth, J Chem Phys 2015, 143, 111101]. By using local fluorescence measurements, we revealed how the Tg(z) profile extends hundreds of nanometers away from the interface showing an asymmetric behavior penetrating deeper into the glassy PS side relative to the composition profile. Here, we extend these measurements to investigate how the local Tg profile in PS varies when in contact with a variety of immiscible polymers whose Tgs vary between +90 K and -80 K relative to the bulk Tg of PS, so-called hard vs. soft confinement. The data reveal that the onset of local Tg deviation from bulk in PS occurs at two distinct length scales, which depend on whether PS is the low Tg component (hard confinement) or the high Tg component (soft confinement). In addition, we explore the influence of finite system size on the range of dynamics by the introduction of periodic boundary conditions, as is commonly encountered in computer simulations or block copolymer systems.

  14. The Hengill geothermal area, Iceland: variation of temperature gradients deduced from the maximum depth of seismogenesis

    USGS Publications Warehouse

    Foulger, G.R.

    1995-01-01

    Given a uniform lithology and strain rate and a full seismic data set, the maximum depth of earthquakes may be viewed to a first order as an isotherm. These conditions are approached at the Hengill geothermal area, S. Iceland, a dominantly basaltic area. The temperature at which seismic failure ceases for the strain rates likely at the Hengill geothermal area is determined by analogy with oceanic crust, and is about 650 ?? 50??C. The topographies of the top and bottom of the seismogenic layer were mapped using 617 earthquakes. The thickness of the seismogenic layer is roughly constant and about 3 km. A shallow, aseismic, low-velocity volume within the spreading plate boundary that crosses the area occurs above the top of the seismogenic layer and is interpreted as an isolated body of partial melt. The base of the seismogenic layer has a maximum depth of about 6.5 km beneath the spreading axis and deepens to about 7 km beneath a transform zone in the south of the area. -from Author

  15. Buoyant-thermocapillary instabilities in extended liquid layers subjected to a horizontal temperature gradient

    NASA Astrophysics Data System (ADS)

    Burguete, J.; Mukolobwiez, N.; Daviaud, F.; Garnier, N.; Chiffaudel, A.

    2001-10-01

    We report experiments on buoyant-thermocapillary instabilities in differentially heated liquid layers. The results are obtained for a fluid of Prandtl number 10 in a rectangular geometry with different aspect ratios. Depending on the height of liquid and on the aspect ratios, the two-dimensional basic flow destabilizes into oblique traveling waves or longitudinal stationary rolls, respectively, for small and large fluid heights. Temperature measurements and space-time recordings reveal the waves to correspond to the hydrothermal waves predicted by the linear stability analysis of Smith and Davis [J. Fluid Mech. 132, 119 (1983)]. Moreover, the transition between traveling and stationary modes agrees with the work by Mercier and Normand [Phys. Fluids 8, 1433 (1996)] even if the exact characteristics of longitudinal rolls differ from theoretical predictions. A discussion about the relevant nondimensional parameters is included. In the stability domain of the waves, two types of sources have been evidenced. For larger heights, the source is a line and generally evolves towards one end of the container leaving a single wave whereas for smaller heights, the source looks like a point and emits a circular wave which becomes almost planar farther from the source in both directions.

  16. Alpine 1/Federal: Temperature gradients, geothermal potential, and geology. Final report, Part 2

    SciTech Connect

    Witcher, J.C.; Hahman, W.R.; Swanberg, C.A.

    1994-06-01

    The Alpine 1/Federal drilling project provided valuable new; information on the geology of the region. Except for drilling into Precambrian rocks, the objectives of the project were accomplished. sufficient temperature and heat-flow information were obtained to assess the near-term HDR geothermal potential of the eastern White Mountains region. Therefore, the primary mission of the project was successful. The HDR potential for near-term electrical power production is not economic. Potential for HDR direct-use space heating is marginal at best and should realistically be considered uneconomic. The Alpine 1/Federal hole should be deepened to Precambrian basement to provide definitive subsurface geological information for this region. Deeper drilling will determine Precambrian lithology and assess if older Paleozoic rock units are present. The hole may be deepened with a BQ drill string. Depth to Precambrian is likely to be between 800 and 2,000 feet below the current 4,505 feet total depth. The failure to reach Precambrian basement due to a previously unknown and unmapped major structural offset highlights the need for detailed surface geological mapping in this poorly understood region.

  17. Solar cycle signal in air temperature in North America - Amplitude, gradient, phase and distribution

    NASA Technical Reports Server (NTRS)

    Currie, R. G.

    1981-01-01

    The considered investigation was motivated by three factors. One is related to an extension of single-channel MESA to multi-channel by Strand (1977), Morf et al. (1978), and Jones (1978). MESA is a high-resolution signal processing and spectrum analysis technique due to Burg (1975). The considered developments resulted in the discovery of the 11-year solar cycle signal in the change of the length of day by Currie (1980, 1981). They also led Currie (1981) to study the phase spectrum of the 11-year term in height H of sea level. The investigation tries to clarify the phase relations among the involved parameters. The second factor is connected with an application of the linear time domain technique used by Currie (1981) to temperature records to obtain more accurate information regarding the signal amplitude. The third factor of motivation is related to increases in the number of stations available for an analysis, the greater average length of the records, and the more accurate data set.

  18. Separation of short-chain branched polyolefins by high-temperature gradient adsorption liquid chromatography.

    PubMed

    Macko, Tibor; Brüll, Robert; Alamo, Rufina G; Stadler, Florian J; Losio, Simone

    2011-02-01

    A new separation principle was recently introduced into the analytical characterization of polyolefins by researchers from the German Institute for Polymers in Darmstadt. It was demonstrated that polyolefins can be selectively separated via high-performance liquid chromatography on the basis of their adsorption/desorption behaviours at temperatures as high as 160 °C. A Hypercarb® column packed with porous graphite gave the best results. The mobile phase consisted of a mixture of 1-decanol and 1,2,4-trichlorobenzene. In this work, the same chromatographic system is applied to the separation of ethylene/alkene and ethylene/norbornene copolymers. It was found that the elution volumes of the samples correlate linearly with the average chemical composition of samples. The elution volume is indirectly proportional to the concentration of branches in the ethylene/alkene copolymer. Branching shortens the length of continuous methylene sequences of the polymer backbone, thus decreasing the probability of orientation of a methylene sequence in a flat conformation on the graphite surface, which enables the most intensive van der Waals interactions between the methylene backbone and the carbon surface. An opposite trend in the elution order has been found for ethylene/norbornene copolymers. The elution volume of the ethylene/norbornene copolymers increased with the concentration of norbornene. It indicates pronounced attractive interactions between graphite and the cyclic comonomer.

  19. Effect of temperature and host tree on cold hardiness of hemlock looper eggs along a latitudinal gradient.

    PubMed

    Rochefort, Sophie; Berthiaume, Richard; Hébert, Christian; Charest, Martin; Bauce, Eric

    2011-06-01

    The hemlock looper, Lambdina fiscellaria, is an economically important insect pest of Canadian forests which overwinters as eggs. Although the hemlock looper causes extensive damages, no information on the mechanisms related to its cold tolerance is known. The objective of this study was to determine the effect of temperature and exposure duration on hemlock looper winter survival but also to identify seasonal supercooling capacity and cryoprotectant levels of three populations along a latitudinal gradient. As host plant may contribute to offspring overwintering success, cold tolerance of hemlock looper eggs from parents whose larvae were fed on three different tree species was also measured. Mean supercooling point (SCP) of hemlock looper eggs was lower than -30 °C from October through the following spring with values being as low as -47 °C in February. Trehalose was the most abundant sugar found in hemlock looper eggs with a peak concentration of 0.3 μg mg⁻¹ DW⁻¹. Glycerol, a polyol, was more often absent in eggs of the different populations and tree species tested in the study. When exposed to different temperature regimes for various periods of time, significant mortality of hemlock looper eggs occurred at higher temperatures than the mean SCP. Thus, hemlock looper could be considered as a chill tolerant species. No clear pattern of population and host plant effects on SCP and cryoprotectants was detected in this study. However, when exposed to different winter temperatures and exposure duration, hemlock looper from higher latitudes survived better (survival rates ranging between 0 and 89% at -20 °C) than those from lower latitudes (survival rates ranging between 0 and 56% at -20 °C). Our results may contribute to a better understanding of hemlock looper winter biology and thus facilitate predictions of outbreaks and range expansion.

  20. Comparison of kinetic and extended magnetohydrodynamics computational models for the linear ion temperature gradient instability in slab geometry

    NASA Astrophysics Data System (ADS)

    Schnack, D. D.; Cheng, J.; Barnes, D. C.; Parker, S. E.

    2013-06-01

    We perform linear stability studies of the ion temperature gradient (ITG) instability in unsheared slab geometry using kinetic and extended magnetohydrodynamics (MHD) models, in the regime k∥/k⊥≪1. The ITG is a parallel (to B) sound wave that may be destabilized by finite ion Larmor radius (FLR) effects in the presence of a gradient in the equilibrium ion temperature. The ITG is stable in both ideal and resistive MHD; for a given temperature scale length LTi0, instability requires that either k⊥ρi or ρi/LTi0 be sufficiently large. Kinetic models capture FLR effects to all orders in either parameter. In the extended MHD model, these effects are captured only to lowest order by means of the Braginskii ion gyro-viscous stress tensor and the ion diamagnetic heat flux. We present the linear electrostatic dispersion relations for the ITG for both kinetic Vlasov and extended MHD (two-fluid) models in the local approximation. In the low frequency fluid regime, these reduce to the same cubic equation for the complex eigenvalue ω =ωr+iγ. An explicit solution is derived for the growth rate and real frequency in this regime. These are found to depend on a single non-dimensional parameter. We also compute the eigenvalues and the eigenfunctions with the extended MHD code NIMROD, and a hybrid kinetic δf code that assumes six-dimensional Vlasov ions and isothermal fluid electrons, as functions of k⊥ρi and ρi/LTi0 using a spatially dependent equilibrium. These solutions are compared with each other, and with the predictions of the local kinetic and fluid dispersion relations. Kinetic and fluid calculations agree well at and near the marginal stability point, but diverge as k⊥ρi or ρi/LTi0 increases. There is good qualitative agreement between the models for the shape of the unstable global eigenfunction for LTi0/ρi=30 and 20. The results quantify how far fluid calculations can be extended accurately into the kinetic regime. We conclude that for the linear ITG

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

    PubMed

    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

    NASA Astrophysics Data System (ADS)

    Sawall, Yvonne; Al-Sofyani, Abdulmoshin; Hohn, Sönke; Banguera-Hinestroza, Eulalia; Voolstra, Christian R.; Wahl, Martin

    2015-03-01

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

    PubMed

    Sawall, Yvonne; Al-Sofyani, Abdulmoshin; Hohn, Sönke; Banguera-Hinestroza, Eulalia; Voolstra, Christian R; Wahl, Martin

    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.

  4. Effects of temperature gradient in the growth of Si0.5Ge0.5 crystals by the traveling liquidus-zone method on board the International Space Station

    NASA Astrophysics Data System (ADS)

    Kinoshita, K.; Arai, Y.; Inatomi, Y.; Tsukada, T.; Miyata, H.; Tanaka, R.

    2016-12-01

    Si0.5Ge0.5 crystals were grown at two different temperature gradients on board the International Space Station (ISS) using the traveling liquidus-zone (TLZ) method and effects of temperature gradient on crystal quality were investigated. Although average axial Ge concentration profile was not affected by the temperature gradient, crystal quality was affected greatly. Single crystal length was shortened and constitutional supercooling (CS) is shown to occur more easily at higher temperature gradient. The calculated degree of CS based on the solute concentration profile in the melt and phase diagram data is about 4 times larger when the temperature gradient is twice, which supports the experimental results. Instability at high temperature gradient is unique to the TLZ method and is not common to other crystal growth methods such as the directional solidification method and Czochralski method.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Caudill, Christopher C; Keefer, Matthew L; Clabough, Tami S; Naughton, George P; Burke, Brian J; Peery, Christopher A

    2013-01-01

    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.

  7. Indirect Effects of Impoundment on Migrating Fish: Temperature Gradients in Fish Ladders Slow Dam Passage by Adult Chinook Salmon and Steelhead

    PubMed Central

    Caudill, Christopher C.; Keefer, Matthew L.; Clabough, Tami S.; Naughton, George P.; Burke, Brian J.; Peery, Christopher A.

    2013-01-01

    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. PMID:24392020

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

    PubMed

    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.

  9. A circular equilibrium model for local gyrokinetic simulations of ion temperature gradient fluctuations in reversed field pinches

    SciTech Connect

    Tangri, Varun; Terry, P. W.; Waltz, R. E.

    2011-05-15

    A simple large-aspect-ratio (R{sub 0}/r) circular equilibrium model is developed for low-beta reversed field pinch (RFP) geometry. The model is suitable for treating small scale instability and turbulent transport driven by ion temperature gradient (ITG) and related electron drift modes in gyrokinetic simulations. The equilibrium model is an RFP generalization of the common tokamak s-{alpha} model to small safety factor (q), where the poloidal field dominates the toroidal field. The model accommodates the RFP toroidal field reversal (where q vanishes) by generalizing the cylindrical force-free Bessel function model (BFM) [J. B. Taylor, Phys. Rev. Lett. 33, 1139 (1974)] to toroidal geometry. The global equilibrium can be described in terms of the RFP field reversal and pinch parameters [F,{Theta}]. This new toroidal Bessel function model (TBFM) has been incorporated into the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J.Comput. Phys. 186, 545 (2003)] and used here to explore local electrostatic ITG adiabatic electron instability rates for typical low-q RFP parameters.

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

    PubMed Central

    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. PMID:28301482

  11. Influence of atmospheric static stability and meridional temperature gradient on the growth in amplitude of synoptic-scale unstable waves

    NASA Astrophysics Data System (ADS)

    Soldatenko, S. A.

    2014-11-01

    Observations and results of numerical experiments with climate models under different green-house-gas emission scenarios point to a reconstruction of the thermal and circulation atmospheric regime induced by global climate changes. In particular, an increase in atmospheric static stability, a poleward shift of midlatitude storm tracks, a decrease in the frequency of extratropical cyclones, and a change in their intensity are found at tropical and middle latitudes. This paper, using a simplified idealized model of baroclinic instability, investigates the influence of small variations in the basic atmospheric parameters governing the development of baroclinic instability, namely, static stability and the vertical quasi-zonal flow velocity shear induced by a meridional temperature gradient, on variations in the growth rate of the amplitude of synopticscale unstable waves. Analytical expressions are derived for absolute and relative sensitivity functions to estimate the absolute and relative contribution of variations in the static stability and the vertical flow velocity shear to a change in the growth rate of the amplitude of unstable modes.

  12. Application of temperature gradient gel electrophoresis to the study of yeast diversity in the estuary of the Tagus river, Portugal.

    PubMed

    Gadanho, Mário; Sampaio, José Paulo

    2004-12-01

    Temperature gradient gel electrophoresis (TGGE) was employed for the assessment of yeast diversity in the estuary of the Tagus river (Portugal). The molecular detection of yeasts was carried out directly from water samples and, in parallel, a cultivation approach by means of an enrichment step was employed. A nested PCR was employed to obtain a fungal amplicon containing the D2 domain of the 26S rRNA gene. For identification the TGGE bands were extracted, re-amplified, and sequenced. Fourteen fungal taxa were detected and all except one were yeasts. Most yeast sequences corresponded to members of the Ascomycota and only three belonged to the Basidiomycota. Five yeasts (four ascomycetes and one basidiomycete) could not be identified to the species level due to the uniqueness of their sequences. The number of species detected after enrichment was higher than the number of taxa found using the direct detection method. This suggests that some yeast populations are present in densities that are below the detection threshold of the method. With respect to the analysis of the yeast community structure, our results indicate that the dominant populations belong to Debaryomyces hansenii, Rhodotorula mucilaginosa, Cryptococcus longus, and to an uncultured basidiomycetous yeast phylogenetically close to Cr. longus. The combined analysis of direct detection and cultivation approaches indicates a similar community structure at the two sampled sites since nine species were present at both localities.

  13. Forearm-finger skin temperature gradient as an index of cutaneous perfusion during steady-state exercise.

    PubMed

    Keramidas, Michail E; Geladas, Nickos D; Mekjavic, Igor B; Kounalakis, Stylianos N

    2013-09-01

    The purpose of this study was to examine whether the forearm-finger skin temperature gradient (T(forearm-finger)), an index of vasomotor tone during resting conditions, can also be used during steady-state exercise. Twelve healthy men performed three cycling trials at an intensity of ~60% of their maximal oxygen uptake for 75 min separated by at least 48 h. During exercise, forearm skin blood flow (BFF ) was measured with a laser-Doppler flowmeter, and finger skin blood flow (PPG) was recorded from the left index fingertip using a pulse plethysmogram. T(forearm-finger) of the left arm was calculated from the values derived by two thermistors placed on the radial side of the forearm and on the tip of the middle finger. During exercise, PPG and BFF increased (P<0.001), and T(forearm-finger) decreased (P<0.001) from their resting values, indicating a peripheral vasodilatation. There was a significant correlation between T(forearm-finger) and both PPG (r = -0.68; P<0.001) and BFF (r = -0.50; P<0.001). It is concluded that T(forearm-finger) is a valid qualitative index of cutaneous vasomotor tone during steady-state exercise.

  14. Perpendicular wavenumber dependence of the linear stability of global ion temperature gradient modes on E × B flows

    NASA Astrophysics Data System (ADS)

    Hill, P.; Saarelma, S.; McMillan, B.; Peeters, A.; Verwichte, E.

    2012-06-01

    Sheared E × B flows are known to stabilize turbulence. This paper investigates how the linear stability of the ion-temperature-gradient (ITG) mode depends on k⊥ in both circular and MHD geometry. We study the effects of both rotation profiles of constant shear and of purely toroidal flow taken from experiment, using the global gyrokinetic particle-in-cell code NEMORB. We find that in order to effectively stabilize the linear mode, the fastest growing mode requires a shearing rate (γE) around 1-2 times its linear growth rate without flow (γ0), while both longer and shorter wavelength modes need much larger flow shear compared with their static linear growth rates. Modes with kθρi < 0.2 need γE as much as 10 times their γ0. This variation exists in both large-aspect ratio circular cross-section and small-aspect ratio MHD geometries, with both analytic constant shear and experimental flow profiles. There is an asymmetry in the suppression with respect to the sign of γE, due to competition between equilibrium profile variation and flow shear. The maximum growth rate for cases using the experimental profile in MAST equilibria occurs at shearing rates of 10% the experimental level.

  15. Thermal dependence of sprint performance in the lizard Psammodromus algirus along a 2200-meter elevational gradient: Cold-habitat lizards do not perform better at low temperatures.

    PubMed

    Zamora-Camacho, Francisco Javier; Rubiño-Hispán, María Virtudes; Reguera, Senda; Moreno-Rueda, Gregorio

    2015-08-01

    Sprint speed has a capital relevance in most animals' fitness, mainly for fleeing from predators. Sprint performance is maximal within a certain range of body temperatures in ectotherms, whose thermal upkeep relies on exogenous thermal sources. Ectotherms can respond to diverse thermal environments either by shifting their thermal preferences or maintaining them through different adaptive mechanisms. Here, we tested whether maximum sprint speed of a lizard that shows conservative thermal ecology along a 2200-meter elevational gradient differs with body temperature in lizards from different elevations. Lizards ran faster at optimum than at suboptimum body temperature. Notably, high-elevation lizards were not faster than mid- and low-elevation lizards at suboptimum body temperature, despite their low-quality thermal environment. This result suggests that both preferred body temperature and thermal dependence of speed performance are co-adapted along the elevational gradient. High-elevation lizards display a number of thermoregulatory strategies that allow them to achieve high optimum body temperatures in a low thermal-quality habitat and thus maximize speed performance. As for reproductive condition, we did not find any effect of it on sprint speed, or any significant interaction with elevation or body temperature. However, strikingly, gravid females were significantly slower than males and non-gravid females at suboptimum temperature, but performed similarly well at optimal temperature.

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

    PubMed

    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

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

    PubMed

    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 (13)C 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

  18. The Measurement of Temperature Gradients in a Soft Tissue Phantom using PVDF arrays: A Simulation Case Using the Finite Element Method (FEM)

    NASA Astrophysics Data System (ADS)

    Acevedo, Pedro; Vázquez, Mónica; Durán, Joel; Petrearce, Rodolfo

    A simulation case is presented using the Finite Element Method (FEM) to simulate the performance of PVDF arrays to measure temperature gradients through the determination of phase shifts, i.e. time shifts of the waveform of the echo due to a change in the speed of propagation of ultrasound as a result of a change in temperature, they can be interpreted as phase shifts in the frequency domain. Making it possible to determine the change in temperature from the phase shifts; in a medium of propagation previously characterized.

  19. Double-stranded cucumovirus associated RNA 5: experimental analysis of necrogenic and non-necrogenic variants by temperature-gradient gel electrophoresis.

    PubMed Central

    Po, T; Steger, G; Rosenbaum, V; Kaper, J; Riesner, D

    1987-01-01

    Cucumber mosaic virus (CMV) and peanut stunt virus (PSV) each contain a fifth major RNA in the size range of 334 to 393 nucleotides. This fifth RNA is a satellite capable of modulating the expression of viral disease symptoms. It is present in infected tissue in single-stranded and double-stranded form. Nucleotide sequence variants of the double-stranded CMV-associated RNA 5 (dsCARNA 5) and PSV-associated RNA 5 (dsPARNA 5) were analysed by temperature-gradient gel electrophoresis. Gels were 5% polyacrylamide, containing 8 M urea in 8.9 mM Tris-borate buffer, with temperature differences of 25-40 degrees C establishing gradients either perpendicular or parallel to the direction of the electric field. For dsCARNA 5 two characteristic transitions were detected with increasing temperature: at temperatures between 40 degrees C and 46 degrees C a drastic retardation in electrophoretic mobility induced by partial dissociation of the duplex structure from the ends and at temperatures above 52 degrees C an abrupt increase in mobility due to complete strand dissociation. dsPARNA 5 exhibited both transitions at up to 10 degrees C higher temperatures and an additional retardation between the transitions mentioned. Seven different variants of dsCARNA 5, 4 necrogenic and 3 non-necrogenic, were analysed. Some showed only one single band, others gave rise to up to six well separated bands corresponding to six molecular species. From all experimental results a correlation between the temperature of the retardation transition and the necrogenicity of CARNA 5 was derived. The diagnostic application of the temperature-gradient gel analysis in agriculture, particularly for the use of non-necrogenic variants as biological control agents to impede CMV-infections, is discussed. Images PMID:3601667

  20. Current density and state of charge inhomogeneities in Li-ion battery cells with LiFePO4 as cathode material due to temperature gradients

    NASA Astrophysics Data System (ADS)

    Fleckenstein, Matthias; Bohlen, Oliver; Roscher, Michael A.; Bäker, Bernard

    2011-05-01

    Current density distributions and local state of charge (SoC) differences that are caused by temperature gradients inside actively cooled Li-ion battery cells are discussed and quantified. As an example, a cylindrical Li-ion cell with LiFePO4 as cathode material (LiFePO4-cell) is analyzed in detail both experimentally and by means of spatial electro-thermal co-simulations. The reason for current density inhomogeneities is found to be the local electrochemical impedance varying with temperature in different regions of the jelly roll. For the investigated cell, high power cycling and the resulting temperature gradient additionally cause SoC-gradients inside the jelly roll. The local SoCs inside one cell diverge firstly because of asymmetric current density distributions during charge and discharge inside the cell and secondly because of the temperature dependence of the local open circuit potential. Even after long relaxation periods, the SoC distribution in cycled LiFePO4-cells remains inhomogeneous across the jelly roll as a result of hysteresis in the open circuit voltage. The occurring thermal electrical inhomogeneities are expected to influence local aging differences and thus, global cell aging. Additionally the occurrence of inhomogeneous current flow and SoC-development inside non-uniformly cooled battery packs of parallel connected LiFePO4-cells is measured and discussed.

  1. Double-stranded cucumovirus associated RNA 5: which sequence variations may be detected by optical melting and temperature-gradient gel electrophoresis?

    PubMed

    Steger, G; Po, T; Kaper, J; Riesner, D

    1987-07-10

    Sequence variants of the double-stranded form of satellite RNAs of cucumber mosaic virus (dsCARNA 5) were analyzed for the possibility to experimentally detect minor nucleotide sequence changes. Denaturation maps (helix-probability versus position of the nucleotide in the sequence versus temperature) were calculated applying the Poland algorithm. Optical denaturation curves and temperature-gradient gel mobility curves were simulated using the denaturation maps and were compared with experimental results from optical melting and temperature-gradient gel electrophoresis (Tien Po et al., accompanying paper). Melting of the dsRNAs starts from both ends of the molecule in two transitions of low co-operativity, continues in the right part in a highly co-operative transition, and is finished in another highly co-operative transition including strand-separation. Whereas all parts of the molecule contribute uniformly to the optical melting curve, opening of the ends predominates in the retardation transition in gel electrophoresis. Detailed discussion of the influence of base pair changes in the sequence shows that a single base pair change may be detected by temperature-gradient gel electrophoresis, if it is located in certain favorable locations, whereas its detection in optical melting curves is possible only in very special cases. The systematic differences found in the accompanying paper between necrogenic and non-necrogenic dsCARNA 5 could be interpreted on the basis of such nucleotide sequence differences.

  2. No divergence in Cassiope tetragona: persistence of growth response along a latitudinal temperature gradient and under multi-year experimental warming

    PubMed Central

    Weijers, Stef; Greve Alsos, Inger; Bronken Eidesen, Pernille; Broekman, Rob; Loonen, Maarten J.J.E.; Rozema, Jelte

    2012-01-01

    Background and Aims The dwarf shrub Cassiope tetragona (Arctic bell-heather) is increasingly used for arctic climate reconstructions, the reliability of which depends on the existence of a linear climate–growth relationship. This relationship was examined over a high-arctic to sub-arctic temperature gradient and under multi-year artificial warming at a high-arctic site. Methods Growth chronologies of annual shoot length, as well as total leaf length, number of leaves and average leaf length per year, were constructed for three sites. Cassiope tetragona was sampled near its cold tolerance limit at Ny-Ålesund, Svalbard, at its assumed climatic optimum in Endalen, Svalbard, and near its European southern limit at Abisko, Sweden. Together these sites represent the entire temperature gradient of this species. Leaf life span was also determined. Each growing season from 2004 to 2010, 17 open top chambers (OTCs) were placed near Ny-Ålesund, thus increasing the daily mean temperatures by 1·23°C. At the end of the 2010 growing season, shoots were harvested from OTCs and control plots, and growth parameters were measured. Key Results All growth parameters, except average leaf length, exhibited a linear positive response (R2 between 0·63 and 0·91) to mean July temperature over the temperature gradient. Average leaf life span was 1·4 years shorter in sub-arctic Sweden compared with arctic Svalbard. All growth parameters increased in response to the experimental warming; the leaf life span was, however, not significantly affected by OTC warming. Conclusions The linear July temperature–growth relationships, as well as the 7 year effect of experimental warming, confirm that the growth parameters annual shoot length, total leaf length and number of leaves per year can reliably be used for monitoring and reconstructing temperature changes. Furthermore, reconstructing July temperature from these parameters is not hampered by divergence. PMID:22700943

  3. Towards high concentration enhancement of microfluidic temperature gradient focusing of sample solutes using combined AC and DC field induced Joule heating.

    PubMed

    Ge, Zhengwei; Wang, Wei; Yang, Chun

    2011-04-07

    It is challenging to continuously concentrate sample solutes in microfluidic channels. We present an improved electrokinetic technique for enhancing microfluidic temperature gradient focusing (TGF) of sample solutes using combined AC and DC field induced Joule heating effects. The introduction of an AC electric field component services dual functions: one is to produce Joule heat for generating temperature gradient; the other is to suppress electroosmotic flow. Consequently the required DC voltages for achieving sample concentration by Joule heating induced TGF are reduced, thereby leading to smaller electroosmotic flow (EOF) and thus backpressure effects. As a demonstration, the proposed technique can lead to concentration enhancement of sample solutes of more than 2500-fold, which is much higher than the existing literature reported microfluidic concentration enhancement by utilizing the Joule heating induced TGF technique.

  4. 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

    NASA Astrophysics Data System (ADS)

    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

  5. 17 CFR 240.15c1-9 - Use of pro forma balance sheets.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 3 2013-04-01 2013-04-01 false Use of pro forma balance sheets. 240.15c1-9 Section 240.15c1-9 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... pro forma balance sheets. The term manipulative, deceptive, or other fraudulent device or...

  6. 17 CFR 240.15c1-9 - Use of pro forma balance sheets.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 4 2014-04-01 2014-04-01 false Use of pro forma balance sheets. 240.15c1-9 Section 240.15c1-9 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... pro forma balance sheets. The term manipulative, deceptive, or other fraudulent device or...

  7. 17 CFR 240.15c1-9 - Use of pro forma balance sheets.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 17 Commodity and Securities Exchanges 3 2012-04-01 2012-04-01 false Use of pro forma balance sheets. 240.15c1-9 Section 240.15c1-9 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... pro forma balance sheets. The term manipulative, deceptive, or other fraudulent device or...

  8. 17 CFR 240.15c3-2 - Customers' free credit balances.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of...

  9. 17 CFR 240.15c1-9 - Use of pro forma balance sheets.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Use of pro forma balance sheets. 240.15c1-9 Section 240.15c1-9 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... pro forma balance sheets. The term manipulative, deceptive, or other fraudulent device or...

  10. 17 CFR 240.15c3-2 - Customers' free credit balances.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of...

  11. 17 CFR 240.15c1-9 - Use of pro forma balance sheets.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Use of pro forma balance sheets. 240.15c1-9 Section 240.15c1-9 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... pro forma balance sheets. The term manipulative, deceptive, or other fraudulent device or...

  12. 17 CFR 240.15c3-2 - Customers' free credit balances.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of...

  13. 17 CFR 240.15c3-2 - Customers' free credit balances.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of...

  14. Responses of Ornithonyssus sylviarum (Acari: Macronyssidae) and Menacanthus stramineus (Phthiraptera: Menoponidae) to gradients of temperature, light, and humidity, with comments on microhabitat selection on chickens.

    PubMed

    Halbritter, D A; Mullens, B A

    2011-03-01

    Responses of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini & Fanzago) (Acari: Macronyssidae), and the chicken body louse (CBL), Menacanthus stramineus (Nitzsch) (Phthiraptera: Menoponidae), to variation in temperature, light, and humidity were assessed in bioassays. The location on a continuous thermal gradient at which each ectoparasite arrested was recorded and analyzed. NFM adults arrested at an average temperature of 30.09 +/- 0.34 degrees C. Adult CBL and first-instar CBL nymphs arrested at 33.69 +/- 0.20 degrees C and 34.99 +/- 0.26 degrees C, respectively. Groups of each ectoparasite were placed into clear glass vials (n = 10/vial) with one half shaded, and vials were exposed to three light levels, as follows: high (200 micromolm(-2)s(-1)), low (4 micromolm(-2)s(-1)), and nearly no light (0 micromolm(-2)s(-1)). The vial cap edges provided an opportunity to assess the interactive effect of light with harborage. NFM avoided light and sought harborage. In low light, the harborage preference overrode the tendency to avoid light. CBL avoided the harborage and showed a minimal preference for light. A four-level humidity gradient was established in two separate experimental arenas for NFM and CBL. Trials were run in ambient light (4 micromolm(-2)s(-1)) for the NFM and in nearly no light for the CBL. The NFM gradient used 38 +/- 2%, 54 +/- 7%, 73 +/- 3%, and 90 +/- 4% RH, whereas the CBL gradient used 42 +/- 5%, 48 +/- 7%, 63 +/- 4%, and 73 +/- 5% RH. NFM showed no humidity response in the walking bioassay, but the CBL settled at the lowest humidity level. Temperature and humidity on different hen body regions were related to the bioassay results and observed on-host ectoparasite distributions.

  15. Empirical equation estimates geothermal gradients

    SciTech Connect

    Kutasov, I.M. )

    1995-01-02

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

  16. Nonisothermal turbulent boundary-layer adverse pressure gradient large scale thermal structure measurements

    SciTech Connect

    Bagheri, N.; White, B.R.; Lei, T.

    1994-01-01

    Hot-wire anemometry measurements in an incompressible turbulent boundary-layer flow over a heated flat plate under equilibrium adverse-pressure-gradient conditions (beta = 1.8) were made for two different temperature difference cases (10 and 15 C) between the wall and the freestream. Space-time correlations of temperature fluctuations (T`) were obtained with a pair of subminiature temperature fluctuation probes. The mean convection velocities, the mean inclination angles, and coherence characteristics of the T` large-scale structure were determined. The present temperature structures measurements for a nonisothermal boundary layer are compared to the zero-pressure-gradient case with identical temperature differences previously reported, in which the mean convection velocity of the T` structure was a function of position y(sup +) and independent of the limited temperature-difference cases tested. The three major findings of the present study, as compared to the zero-pressure-gradient case, are (1) the mean convection speed of the T` structure under beta = 1.8 pressure-gradient conditions was found to be substantially lower in the logarithmic core region than the zero-pressure-gradient case. Additionally, the mean convection speed is felt by the authors to be a function of pressure-gradient parameter beta; (2) the mean inclination angle of the T` structure to the wall under the adverse-pressure-gradient flow was 32 deg, which compares favorably to the 30-deg value of the zero-pressure-gradient case; and (3) the limited data suggests that the mean convection velocity of the T` structure is a function of y(sup +) and independent of the limited temperature-difference cases tested. 11 refs.

  17. Solar irradiance modulation of Equator-to-Pole (Arctic) temperature gradients: Empirical evidence for climate variation on multi-decadal timescales

    NASA Astrophysics Data System (ADS)

    Soon, Willie; Legates, David R.

    2013-02-01

    Using thermometer-based air temperature records for the period 1850-2010, we present empirical evidence for a direct relationship between total solar irradiance (TSI) and the Equator-to-Pole (Arctic) surface temperature gradient (EPTG). Modulation of the EPTG by TSI is also shown to exist, in variable ways, for each of the four seasons. Interpretation of the positive relationship between the TSI and EPTG indices suggests that solar-forced changes in the EPTG may represent a hemispheric-scale relaxation response of the system to a reduced Equator-to-Pole temperature gradient, which occurs in response to an increasing gradient of incoming solar insolation. Physical bases for the TSI-EPTG relationship are discussed with respect to their connections with large-scale climate dynamics, especially a critical relationship with the total meridional poleward energy transport. Overall, evidence suggests that a net increase in the TSI, or in the projected solar insolation gradient which reflects any net increase in solar radiation, has caused an increase in both oceanic and atmospheric heat transport to the Arctic in the warm period since the 1970s, resulting in a reduced temperature gradient between the Equator and the Arctic. We suggest that this new interpretative framework, which involves the extrinsic modulation of the total meridional energy flux beyond the implicit assumptions of the Bjerknes Compensation rule, may lead to a better understanding of how global and regional climate has varied through the Holocene and even the Quaternary (the most recent 2.6 million years of Earth's history). Similarly, a reassessment is now required of the underlying mechanisms that may have governed the equable climate dynamics of the Eocene (35-55 million years ago) and late Cretaceous (65-100 million years ago), both of which were warm geological epochs. This newly discovered relationship between TSI and the EPTG represents the "missing link" that was implicit in the empirical

  18. An objective tropical Atlantic sea surface temperature gradient index for studies of south Amazon dry-season climate variability and change.

    PubMed

    Good, Peter; Lowe, Jason A; Collins, Mat; Moufouma-Okia, Wilfran

    2008-05-27

    Future changes in meridional sea surface temperature (SST) gradients in the tropical Atlantic could influence Amazon dry-season precipitation by shifting the patterns of moisture convergence and vertical motion. Unlike for the El Niño-Southern Oscillation, there are no standard indices for quantifying this gradient. Here we describe a method for identifying the SST gradient that is most closely associated with June-August precipitation over the south Amazon. We use an ensemble of atmospheric general circulation model (AGCM) integrations forced by observed SST from 1949 to 2005. A large number of tropical Atlantic SST gradient indices are generated randomly and temporal correlations are examined between these indices and June-August precipitation averaged over the Amazon Basin south of the equator. The indices correlating most strongly with June-August southern Amazon precipitation form a cluster of near-meridional orientation centred near the equator. The location of the southern component of the gradient is particularly well defined in a region off the Brazilian tropical coast, consistent with known physical mechanisms. The chosen index appears to capture much of the Atlantic SST influence on simulated southern Amazon dry-season precipitation, and is significantly correlated with observed southern Amazon precipitation. We examine the index in 36 different coupled atmosphere-ocean model projections of climate change under a simple compound 1% increase in CO2. Within the large spread of responses, we find a relationship between the projected trend in the index and the Amazon dry-season precipitation trends. Furthermore, the magnitude of the trend relationship is consistent with the inter-annual variability relationship found in the AGCM simulations. This suggests that the index would be of use in quantifying uncertainties in climate change in the region.

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

    NASA Astrophysics Data System (ADS)

    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

  20. [Multi-gradients of land surface temperature in mountainous cities with rapid urbanization: a case study in central area of Chongqing City].

    PubMed

    Han, Gui-Feng; Zhao, Ke; Yan, Wen-Tao; Ye, Lin

    2012-06-01

    By using TM/ETM+ and MODIS images, the land surface temperature (LST) and relative heat island intensity (RHII) of the central area of Chongqing City were extracted to analyze the distribution patterns of the LST and RHII along the multi-gradients of topography, population, and gross domestic product (GDP) as well as the potential quantitative relationships. The LST and RHII manifested a non-monotonically decreasing trend along the gradients of elevation and relief degree, respectively, both with a significant quadratic polynomial relationship. The maximum RHII appeared at 200-350 m elevation section due to the massive urban construction activities, and had significant linear relationships with the population density and the GDP per square kilometer. The RHII rose about 0.10 degrees C when the population density increased 1000 people per square kilometer, and rose about 0.08 degrees C when the GDP per square kilometer increased 10 million RMB Yuan.

  1. 17 CFR 240.15c3-1d - Satisfactory Subordination Agreements (Appendix D to 17 CFR 240.15c3-1).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (D). (2) Certain Definitions. For purposes of 17 CFR 240.15c3-1 and this Appendix (D): (i) A... market value of commodity options purchased by option customers subject to the rules of a contract market, each such deduction not to exceed the amount of funds in the option customer's account), if greater....

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

    SciTech Connect

    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.

  3. Analysis of orbital occupancy of valence neutron in {sup 15}C through Coulomb breakup reactions

    SciTech Connect

    Singh, P. E-mail: pardeep.phy@dcrustm.org

    2015-03-15

    The Coulomb breakup reactions {sup 208}Pb({sup 15}C, {sup 14}C + n){sup 208}Pb and {sup 181}Ta({sup 15}C, {sup 14}C + n){sup 181}Ta have been studied at 68 and 85 A MeV beam energies, respectively, within the framework of the eikonal approximation to investigate the orbital occupancy of valence neutron in the {sup 15}C nucleus. The outcomes of the present work favor 0{sup +} ⊗ 2s{sub 1/2} as the core-neutron coupling for the ground-state structure with 0.91 as a spectroscopic factor.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Temperature profile analysis for Amargosa Valley wells LWS-A, ASH-B, and MSH-C. DOE UGTA RI/FS geothermal gradient study results FY 1995

    SciTech Connect

    Gillespie, D.

    1995-09-01

    The purpose of this investigation is to estimate vertical fluid flux rates in saturated units penetrated by selected wells at the Nevada Test Site (NTS) using geothermal gradient data. Estimates of vertical fluid flux rates are critical in developing models for contaminate flow within, recharge potential to, and discharge from the groundwater system at the NTS. If temperature in the well is in equilibrium with the surrounding rocks, it is possible to detect the vertical flow of groundwater from the well`s thermal profile. Heat in the subsurface is transported by conduction through the rock and by advection caused by subsurface water movement. Units in which vertical flow is occurring will produce a curve in the thermal profile within the well. Prior to the implementation of the Underground Test Area Remedial Investigation/Feasibility Study (UGTA RI/FS), investigation of thermal data from wells at the NTS was hindered by the completion of wells as open holes or without casing cemented in place. The open-hole type of completion allows cross-flow within the wellbore which can yield information about relative pressures between connected aquifers, but which renders thermal gradient data essentially useless, or at best highly suspect for interpreting in situ groundwater movement. Wells recently completed in the Department of Energy (DOE) Environmental Restoration (ER) Program have been completed with casing cemented to the surface (to prohibit cross-flow between units in the annular space between the casing and the wellbore) and with completion zones open to a single hydrologic horizon. This type of completion results in temperature gradient profiles more representative of actual thermal conditions in the units penetrated by the well. Results are presented of temperature profiles of 3 wells located in the Death Valley Groundwater Basin, outside the southern border of the NTS.

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

    PubMed

    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).

  7. [Use of the rectal-skin temperature gradient for the rapid evaluation of the severity and prediction of the outcomes in critical states].

    PubMed

    Nazarenko, G I

    1986-10-01

    Results of the monitor observation of the recto-skin temperature gradient in 263 patients are described. Among them 199 patients were in critical condition (traumatic shock--in 51; burn--in 99; cardiogenic shock--in 33; septic collapse--in 11). The elevation of this parameter more than 9 degrees C shows the presence of shock. It can be used for control of the efficiency of the antishock therapy and represents a simple, reliable and highly informative method not requiring an expensive equipment.

  8. Microstructure and high temperature oxidation resistance of Ti-Ni gradient coating on TA2 titanium alloy fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Fencheng; Mao, Yuqing; Lin, Xin; Zhou, Baosheng; Qian, Tao

    2016-09-01

    To improve the high temperature oxidation resistance of TA2 titanium alloy, a gradient Ni-Ti coating was laser cladded on the surface of the TA2 titanium alloy substrate, and the microstructure and oxidation behavior of the laser cladded coating were investigated experimentally. The gradient coating with a thickness of about 420-490 μm contains two different layers, e.g. a bright layer with coarse equiaxed grain and a dark layer with fine and columnar dendrites, and a transition layer with a thickness of about 10 μm exists between the substrate and the cladded coating. NiTi, NiTi2 and Ni3Ti intermetallic compounds are the main constructive phases of the laser cladded coating. The appearance of these phases enhances the microhardness, and the dense structure of the coating improves its oxidation resistance. The solidification procedure of the gradient coating is analyzed and different kinds of solidification processes occur due to the heat dissipation during the laser cladding process.

  9. 17 CFR 240.15c1-8 - Sales at the market.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a...

  10. 17 CFR 240.15c1-8 - Sales at the market.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a...

  11. 17 CFR 240.15c1-8 - Sales at the market.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 4 2014-04-01 2014-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a...

  12. 17 CFR 240.15c1-8 - Sales at the market.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 17 Commodity and Securities Exchanges 3 2012-04-01 2012-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a...

  13. 17 CFR 240.15c1-8 - Sales at the market.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 3 2013-04-01 2013-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a...

  14. Presence of a temperature gradient among genital tract portions and the thermal changes within these portions over the estrous cycle in beef cows.

    PubMed

    El-Sheikh Ali, Hossam; Kitahara, Go; Tamura, Youji; Kobayashi, Ikuo; Hemmi, Koichiro; Torisu, Shidow; Sameshima, Hiroshi; Horii, Yoichiro; Zaabel, Samy; Kamimura, Shunichi

    2013-01-01

    The aim of the present study was to describe the temperature of the different portions of the female genital tract and their relation to rectal temperature and to investigate the effect of steroid hormones profiles on these variables over the estrous cycle in cattle. Four nonpregnant Japanese Black cows were investigated daily over two successive estrous cycles using a digital thermometer with a long probe and rounded-end sensor to record the temperature of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT) and uterine horns (UHT). Blood samples were collected immediately before temperature recording to assay peripheral levels of progesterone (P(4)) and estradiol-17β (E(2)). Moreover, transrectal ultrasonography was carried out after temperature recording to monitor the ovulatory follicle and track ovulation. During the experiment, the ambient temperature and relative humidity were recorded for further calculation of the temperature humidity index (THI). The temperature within the genital tracts in these cows progressively increased towards the uterine horns from the vagina. The VT, CT, UBT and UHTs were significantly higher in association with peripheral P(4) concentrations greater than 4 ng/ml (mid-luteal phase) when compared with lower peripheral P(4) concentrations. The VT was more significantly (P<0.01) correlated to the CT, UBT and UHTs than RT. In conclusion, a temperature gradient was present among the vagina, cervix and uterus over the estrous cycle, and changes in peripheral P(4) concentrations were associated with the thermal variations within these portions. The VT could be more beneficial than RT in monitoring temperature of deeper portions of the female genital tract in bovine.

  15. Gradient Driven Fluctuations

    NASA Technical Reports Server (NTRS)

    Cannell, David

    2005-01-01

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

  16. Changes in permeability and fluid chemistry of the Topopah Spring Member of the Paintbrush tuff (Nevada Test Site) when held in a temperature gradient: summary of results

    SciTech Connect

    Moore, D.E.; Morrow, C.A.; Byerlee, J.D.

    1984-06-01

    The permeability and groundwater chemistry results for the Topopah Spring Member are reported and compared with the results from the previous work on Bullfrog. Permeability measurements made on samples of the Topopah Spring Member of the Paintbrush Tuff at room-temperature and in a temperature gradient show that the initially high (3-65 {mu}da) permeabilities are little affected by heating to at least 150{sup 0}C. These permeability relationships are favvorable for the disposal of nuclear waste in this stuff in an unsaturated zone at the Nevada Test Site. The fluids discharged from the samples of tuff during the experiments are dilute, nearly neutral solutions that differ only slightly from the starting groundwater composition. 8 references, 10 figures, 5 tables.

  17. Heating/ethanol-response of poly methyl methacrylate (PMMA) with gradient pre-deformation and potential temperature sensor and anti-counterfeit applications

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Huang, Wei Min; Lian Wu, Xue; Ge, Yu Chun; Zhang, Fan; Zhao, Yong; Geng, Junfeng

    2014-06-01

    In this paper, the heating/ethanol-response of a commercial poly methyl methacrylate (PMMA) is investigated. All PMMA samples are pre-deformed by means of impression (surface compression with a mold) to introduce a gradient pre-strain/stress field. Two types of molds are applied in impression. One is a Singaporean coin and the other is a particularly designed mold with a variable protrusive feature on top. Two potential applications—temperature sensors to monitor overheating temperatures and anti-counterfeit labels with a water-mark that appears only upon heating to a particular temperature—are demonstrated. Since the heating-responsive shape memory effect (SME) is an intrinsic feature of almost all polymers, other conventional polymers may be used in such applications as well.

  18. Coral record of southeast Indian Ocean SST, SSH and salinity and their modulation by ENSO and the Western Pacific temperature gradient

    NASA Astrophysics Data System (ADS)

    Zinke, Jens; Hoell, Andrew; Lough, Janice M.; Feng, Ming; McCulloch, Malcolm T.

    2016-04-01

    Variability of southeastern Indian Ocean (SEIO) sea surface temperatures (SST), sea surface height (SSH) and salinities off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Niña events often result in a strengthened Leeuwin Current, high coastal sea levels, low salinities and unusually warm SSTs, now termed Ningaloo Niño events. The long-term teleconnections of the southeastern Indian Ocean (SEIO) with ENSO and the West Pacific Warm Pool are poorly understood. Here we demonstrate the role of Indo-Pacific coupling in modulating SST, SSH and salinity in the poorly studied SEIO, through a robust 215 year (1795-2010) geochemical coral proxy sea surface temperature (SST), SSH and salinity record. We show that higher SST and SSH accompanied by lower salinities in the SEIO are linked to the behaviour of ENSO and 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. Better understanding of the interplay between the zonal SST gradient in the western Pacific, ENSO phase and intrinsic Indian Ocean variability is expected to improve our ability to better predict unusual marine heat waves, sea level surges and important consequences for marine socio-ecological systems in the Future.

  19. Search for Correlation Between Plasma Rotation and Electron Temperature Gradient Scale Length in LOC/SOC Transition at Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Houshmandyar, Saeid; Rowan, William L.; Phillips, Perry E.; Walk, John R.; Rice, John E.

    2015-11-01

    Understanding the mechanism governing the linear ohmic confinement (LOC) and the transition to saturated ohmic confinement (SOC) has long been a focus of tokamak research. It is commonly accepted that at low density, the confinement is dominated by electron-scale turbulence while at high density, the turbulence is dominated by ion temperature gradient. At Alcator C-Mod, the core rotation reversal was shown to be consistent with this ansatz. However a recent study at AUG suggests that the intrinsic rotation behavior is rather determined by local plasma parameters regardless of the heating method or the confinement regime. Here, we follow this idea and search for dependence of intrinsic rotation on electron temperature gradient scale length, a quantity with a pivotal role in plasma transport. The high-resolution (1 μs, 7mm) electron cyclotron emission diagnostic at C-Mod (FRCECE) coupled with the BT jog technique allows direct LTe measurements. In the BT jog technique, a 1.5% change in the toroidal magnetic field shifts the viewing volume of the ECE by ~ 1 cm, and the ratio of the average of the signal to the change in the signal during its ramp-up yields LTe. Supported by USDoE awards DE-FG03-96ER-54373 and DE-FC02-99ER54512.

  20. Effects of radio frequency fields in the lower hybrid range on temperature gradient driven drift-modes in tokamaks: Momentum and impurity transport

    NASA Astrophysics Data System (ADS)

    Das, Salil; Jhang, Hogun; Singh, R.; Nordman, H.

    2016-10-01

    The significant effect of impurities in radiation losses and plasma dilution, which result in lower fusion power, and the evaluation of the important effects of intrinsic rotation on transport barrier formation, determination of momentum pinch velocity and its theoretical basis, in tokamak performance is studied using the four-wave parametric process using an electrostatic, collisionless fluid model for ion-temperature-gradient and trapped-electron mode driven turbulence in the presence of radio frequency fields in the lower hybrid (LH) range of frequencies. The beating of the pump and the sidebands exert a ponderomotive force on electrons, modifying the eigenfrequency of the drift waves and influencing the growth rates and the turbulent transport properties. Explicit expressions for the non-linear growth rate and the associated ion thermal conductivity and effective impurity diffusivity are derived. The effects of the rf fields on the momentum and impurity transport coefficients are evaluated for key parameters like rf power, temperature gradients, and magnetic shear. Prince Georges Community College, Largo, Maryland 20774, USA.

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

    PubMed

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

    2017-03-22

    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.

  2. Effect of temperature gradients on single-strand conformation polymorphism analysis in a capillary electrophoresis system using Pluronic polymer matrix.

    PubMed

    Hwang, Hee Sung; Shin, Gi Won; Park, Han Jin; Ryu, Chang Y; Jung, Gyoo Yeol

    2013-09-02

    Capillary electrophoresis-single strand conformation polymorphism (CE-SSCP) analysis is a prominent bioseparation method based on the mobility diversity caused by sequence-induced conformational differences of single-stranded DNA. The use of Pluronic polymer matrix has opened up new opportunities for CE-SSCP, because it improved the resolution for various genetic analyses. However, there still exists a challenge in optimizing Pluronic-based CE-SSCP, because the physical properties of Pluronic solutions are sensitive to temperature, particularly near the gelation temperature, where the viscoelasticity of Pluronic F108 solutions sharply changes from that of a Newtonian fluid to a hydrogel upon heating. We have focused on a set of experiments to control the ambient temperature of the CE system with the aim of enhancing the reliability of the CE-SSCP analysis by using the Applied Biosystems ABI 3130xl genetic analyzer with Pluronic F108 solution matrix. The ambient temperature control allowed us to vary the inlet and outlet portion of the capillary column, while the temperature of the column was kept at 35°C. The resolution to separate 2 single-base-pair-differing DNA fragments was significantly enhanced by changing the temperature from 19 to 30°C. The viscoelastic properties of the F108 solution matrix upon heating were also investigated by ex situ rheological experiments with an effort to reveal how the development of gels in Pluronic solutions affects the resolution of CE-SSCP. We found that the column inlet and outlet temperatures of the capillary column have to be controlled to optimize the resolution in CE-SSCP by using the Pluronic matrix.

  3. Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum - Results from IODP Expedition 325

    NASA Astrophysics Data System (ADS)

    Felis, Thomas; McGregor, Helen V.; Linsley, Braddock K.; Tudhope, Alexander W.; Gagan, Michael K.; Suzuki, Atsushi; Inoue, Mayuri; Thomas, Alexander L.; Esat, Tezer M.; Thompson, William G.; Tiwari, Manish; Potts, Donald C.; Mudelsee, Manfred; Yokoyama, Yusuke; Webster, Jody M.

    2015-04-01

    Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and δ18O for Last Glacial Maximum and deglacial corals that were drilled by Integrated Ocean Drilling Program (IODP) Expedition 325 along the shelf edge seaward of the modern GBR. The Sr/Ca and δ18O records of the precisely U-Th dated fossil shallow-water corals show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 ° C larger temperature decrease between 17° S and 20° S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial and regionally differing temperature change during the last deglaciation, much larger temperature changes than previously recognized. Furthermore, our findings suggest a northward contraction of the Western Pacific Warm Pool during the LGM and last deglaciation, and serve to explain anomalous drying of northeastern Australia at that time. Overall, the GBR developed through significant SST change and, considering temperature alone, may be more resilient than previously thought. Webster, J. M., Yokoyama, Y. & Cotteril, C. & the Expedition 325 Scientists. Proceedings of the Integrated Ocean Drilling Program Vol. 325 (Integrated Ocean Drilling Program Management International Inc., 2011). Felis, T., McGregor, H. V., Linsley, B. K., Tudhope, A. W., Gagan, M. K., Suzuki, A., Inoue, M., Thomas, A. L., Esat, T. M., Thompson, W. G., Tiwari, M., Potts, D. C., Mudelsee, M., Yokoyama, Y., Webster, J. M. Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum. Nature Communications 5, 4102

  4. Data Report. Volume I. Velocity and Temperature Profile Data for Zero Pressure Gradient, Fully Turbulent Boundary Layers.

    DTIC Science & Technology

    1981-01-01

    o I kru T V A L t’ CF Trvu-R1TL1;r rl;7LT 7 Z CALCLLtTCP DELTA = 6116T D!SrLACrm -T THICX!.%~c (LrLSTf!Z) = .l747f7426 ?A-,, rTU - Tl4-7 -XQ,-rS (TW-TA...2 g VELOCITY AND TEMPERATURE RATIOS ISA 0.0 U0 T~*T 30- VELOCITY AND TEMPERATURE DISTRIBUTIONS IN UNIVERSAL COORDINATES + 1O1 Figure 44. Boundary

  5. On the sensitive measurement of horizontal temperature gradients of air near an astrometric instrument for correcting anomalous refraction.

    NASA Astrophysics Data System (ADS)

    Hu, N.; Wang, Z.; Jiang, X.

    Anomalous refraction is believed to be the main error source for classical astrometry. This paper suggests that by measuring the small difference of two average temperature values for two long air columns, which are close to the star light beam, then the anomalous refraction taking place between these two air columns can be obtained in real-time. Suitable measuring equipment with a sensitivity of 0.003°C in measuring the temperature difference of air columns corresponding to a sensitivity of 0arcsec.008 in determining the anomalous refraction are under development.

  6. Shear-layer correction after Amiet under consideration of additional temperature gradient. Working diagrams for correction of signals

    NASA Technical Reports Server (NTRS)

    Dobrzynski, W.

    1984-01-01

    Amiet's correction scheme for sound wave transmission through shear-layers is extended to incorporate the additional effects of different temperatures in the flow-field in the surrounding medium at rest. Within a parameter-regime typical for acoustic measurements in wind tunnels amplitude- and angle-correction is calculated and plotted systematically to provide a data base for the test engineer.

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

    USGS Publications Warehouse

    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.

  8. Northern Hemisphere Meridional and Zonal Temperature Gradients and their Relation to Hydrologic Extremes at Mid-latitudes: Trends, Variability and Link to Climate Modes in Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Karamperidou, C.; Lall, U.; Cioffi, F.

    2010-12-01

    The mid-latitude storm track, which depends on how the jet stream dynamics (mean flow and transient eddies coupled to it) are modulated by large scale ocean-land boundary conditions, is a factor in determining moisture and heat transport associated with extreme hydrologic events, such as floods and droughts. These boundary conditions depend in turn on both the state of evolution of the known interannual and multi-decadal natural variability (e.g., the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO)) and on changes in meridional and zonal surface temperature gradients (Equator-to-Pole and Ocean-Land contrast, respectively) due to anthropogenic forcing. We examine the historical trends of the seasonal NH Equator-to-Pole temperature Gradient (EPG) and the Ocean-Land temperature Contrast (OLC), their probability structure, and their potential relation to anthropogenic warming. We investigate how different combinations of EPG and OLC are associated with precipitation anomalies at mid-latitudes, with a focus in the US and European region. Figure 1 shows an example of how the combination of high OLC- low EPG is associated with positive precipitation anomalies in the aforementioned regions (upper panel), while the combination of low EPG-high OLC is linked to average conditions or negative precipitation anomalies (lower panel), data from Eischeid et al. (1991). We also explore their relation to modes of variability, such as ENSO, as exhibited in observational data and GCM simulations, and utilize GCM projections to estimate potential changes in the frequency and persistence of certain combinations of EPG and OLC associated with precipitation anomalies under climate change scenarios. Winter (DJF) precipitation anomalies for two cases of combinations of EPG and OLC. (a) High OLC and low EPG corresponds to positive anomalies. (b) Low OLC and high EPG corresponds to near zero or negative anomalies for most regions. Data from Eischeid et al (1991).

  9. The sensitivity of tropical leaf litter decomposition to temperature: results from a large-scale leaf translocation experiment along an elevation gradient in Peruvian forests.

    PubMed

    Salinas, N; Malhi, Y; Meir, P; Silman, M; Roman Cuesta, R; Huaman, J; Salinas, D; Huaman, V; Gibaja, A; Mamani, M; Farfan, F

    2011-03-01

    • We present the results from a litter translocation experiment along a 2800-m elevation gradient in Peruvian tropical forests. The understanding of the environmental factors controlling litter decomposition is important in the description of the carbon and nutrient cycles of tropical ecosystems, and in predicting their response to long-term increases in temperature. • Samples of litter from 15 species were transplanted across all five sites in the study, and decomposition was tracked over 448 d. • Species' type had a large influence on the decomposition rate (k), most probably through its influence on leaf quality and morphology. When samples were pooled across species and elevations, soil temperature explained 95% of the variation in the decomposition rate, but no direct relationship was observed with either soil moisture or rainfall. The sensitivity of the decay rate to temperature (κ(T)) varied seven-fold across species, between 0.024 and 0.169 °C⁻¹, with a mean value of 0.118 ± 0.009 °C⁻¹ (SE). This is equivalent to a temperature sensitivity parameter (Q₁₀) for litter decay of 3.06 ± 0.28, higher than that frequently assumed for heterotrophic processes. • Our results suggest that the warming of approx. 0.9 °C experienced in the region in recent decades may have increased decomposition and nutrient mineralization rates by c. 10%.

  10. Soil carbon dynamics following land-use change varied with temperature and precipitation gradients: evidence from stable isotopes.

    PubMed

    Zhang, Kerong; Dang, Haishan; Zhang, Quanfa; Cheng, Xiaoli

    2015-02-02

    Knowledge of soil organic matter (SOM) dynamics following deforestation or reforestation is essential for evaluating carbon (C) budgets and cycle at regional or global scales. Worldwide land-use changes involving conversion of vegetation with different photosynthetic pathways (e.g. C3 and C4 ) offer a unique opportunity to quantify SOM decomposition rate and its response to climatic conditions using stable isotope techniques. We synthesized the results from 131 sites (including 87 deforestation observations and 44 reforestation observations) which were compiled from 36 published papers in the literatures as well as our observations in China's Qinling Mountains. Based on the (13) C natural abundance analysis, we evaluated the dynamics of new and old C in top soil (0-20 cm) following land-use change and analyzed the relationships between soil organic C (SOC) decomposition rates and climatic factors. We found that SOC decomposition rates increased significantly with mean annual temperature and precipitation in the reforestation sites, and they were not related to any climatic factor in deforestation sites. The mean annual temperature explained 56% of variation in SOC decomposition rates by exponential model (y = 0.0014e(0.1395x) ) in the reforestation sites. The proportion of new soil C increased following deforestation and reforestation, whereas the old soil C showed an opposite trend. The proportion of new soil C exceeded the proportion of old soil C after 45.4 years' reforestation and 43.4 years' deforestation, respectively. The rates of new soil C accumulation increased significantly with mean annual precipitation and temperature in the reforestation sites, yet only significantly increased with mean annual precipitation in the deforestation sites. Overall, our study provides evidence that SOC decomposition rates vary with temperature and precipitation, and thereby implies that global warming may accelerate SOM decomposition.

  11. Method for compression molding of thermosetting plastics utilizing a temperature gradient across the plastic to cure the article

    NASA Technical Reports Server (NTRS)

    Heier, W. C. (Inventor)

    1974-01-01

    A method is described for compression molding of thermosetting plastics composition. Heat is applied to the compressed load in a mold cavity and adjusted to hold molding temperature at the interface of the cavity surface and the compressed compound to produce a thermal front. This thermal front advances into the evacuated compound at mean right angles to the compression load and toward a thermal fence formed at the opposite surface of the compressed compound.

  12. 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.

    PubMed

    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

  13. 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

    PubMed Central

    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

  14. Main-ion intrinsic toroidal rotation profile driven by residual stress torque from ion temperature gradient turbulence in the DIII-D tokamak

    DOE PAGES

    Grierson, B. A.; Wang, W. X.; Ethier, S.; ...

    2017-01-06

    Intrinsic toroidal rotation of the deuterium main ions in the core of the DIII-D tokamak is observed to transition from flat to hollow, forming an off-axis peak, above a threshold level of direct electron heating. Nonlinear gyrokinetic simulations show that the residual stress associated with electrostatic ion temperature gradient turbulence possesses the correct radial location and stress structure to cause the observed hollow rotation profile. Residual stress momentum flux in the gyrokinetic simulations is balanced by turbulent momentum diffusion, with negligible contributions from turbulent pinch. Finally, the prediction of the velocity profile by integrating the momentum balance equation produces amore » rotation profile that qualitatively and quantitatively agrees with the measured main-ion profile, demonstrating that fluctuation-induced residual stress can drive the observed intrinsic velocity profile.« less

  15. Main-Ion Intrinsic Toroidal Rotation Profile Driven by Residual Stress Torque from Ion Temperature Gradient Turbulence in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Grierson, B. A.; Wang, W. X.; Ethier, S.; Staebler, G. M.; Battaglia, D. J.; Boedo, J. A.; deGrassie, J. S.; Solomon, W. M.

    2017-01-01

    Intrinsic toroidal rotation of the deuterium main ions in the core of the DIII-D tokamak is observed to transition from flat to hollow, forming an off-axis peak, above a threshold level of direct electron heating. Nonlinear gyrokinetic simulations show that the residual stress associated with electrostatic ion temperature gradient turbulence possesses the correct radial location and stress structure to cause the observed hollow rotation profile. Residual stress momentum flux in the gyrokinetic simulations is balanced by turbulent momentum diffusion, with negligible contributions from turbulent pinch. The prediction of the velocity profile by integrating the momentum balance equation produces a rotation profile that qualitatively and quantitatively agrees with the measured main-ion profile, demonstrating that fluctuation-induced residual stress can drive the observed intrinsic velocity profile.

  16. Main-Ion Intrinsic Toroidal Rotation Profile Driven by Residual Stress Torque from Ion Temperature Gradient Turbulence in the DIII-D Tokamak.

    PubMed

    Grierson, B A; Wang, W X; Ethier, S; Staebler, G M; Battaglia, D J; Boedo, J A; deGrassie, J S; Solomon, W M

    2017-01-06

    Intrinsic toroidal rotation of the deuterium main ions in the core of the DIII-D tokamak is observed to transition from flat to hollow, forming an off-axis peak, above a threshold level of direct electron heating. Nonlinear gyrokinetic simulations show that the residual stress associated with electrostatic ion temperature gradient turbulence possesses the correct radial location and stress structure to cause the observed hollow rotation profile. Residual stress momentum flux in the gyrokinetic simulations is balanced by turbulent momentum diffusion, with negligible contributions from turbulent pinch. The prediction of the velocity profile by integrating the momentum balance equation produces a rotation profile that qualitatively and quantitatively agrees with the measured main-ion profile, demonstrating that fluctuation-induced residual stress can drive the observed intrinsic velocity profile.

  17. Permeability and continuous gradient temperature monitoring of volcanic rocks: new insights from borehole and laboratory analysis at the Campi Flegrei caldera (Southern Italy).

    NASA Astrophysics Data System (ADS)

    Carlino, Stefano; Piochi, Monica; Tramelli, Anna; Troise, Claudia; Mormone, Angela; Montanaro, Cristian; Scheu, Bettina; Klaus, Mayer; Somma, Renato; De Natale, Giuseppe

    2016-04-01

    The pilot borehole recently drilled in the eastern caldera of Campi Flegrei (Southern Italy), during the Campi Flegrei Deep Drill Project (CFDDP) (in the framework of the International Continental Scientific Drilling Program) allowed (i) estimating on-field permeability and coring the crustal rocks for laboratory experiments, and (ii) determining thermal gradient measurements down to ca. 500 m of depth. We report here a first comparative in situ and laboratory tests to evaluate the rock permeability in the very high volcanic risk caldera of Campi Flegrei, in which ground deformations likely occur as the persistent disturbance effect of fluid circulation in the shallower geothermal system. A large amount of petro-physical information derives from outcropping welded tuffs, cores and geophysical logs from previous AGIP's drillings, which are located in the central and western part of the caldera. We discuss the expected scale dependency of rock permeability results in relation with well-stratigraphy and core lithology, texture and mineralogy. The new acquired data improve the database related to physical property of Campi Flegrei rocks, allowing a better constrain for the various fluid-dynamical models performed in the tentative to understand (and forecast) the caldera behavior. We also present the first data on thermal gradient continuously measured through 0 - to 475 m of depth by a fiber optic sensor installed in the CFDDP pilot hole. As regards, we show that the obtained values of permeability, compared with those inferred from eastern sector of the caldera, can explain the different distribution of temperature at depth, as well as the variable amount of vapor phase in the shallow geothermal system. The measured temperatures are consistent with the distribution of volcanism in the last 15 ka.

  18. 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.

    PubMed

    Karsten, Ulf; Herburger, Klaus; Holzinger, Andreas

    2016-05-01

    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.

  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

    PubMed Central

    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. Buckling and free vibration of shallow curved micro/nano-beam based on strain gradient theory under thermal loading with temperature-dependent properties

    NASA Astrophysics Data System (ADS)

    Rahmani, O.; Hosseini, S. A. H.; Ghoytasi, I.; Golmohammadi, H.

    2017-01-01

    In this study, influences of a uniform thermomechanical loading in buckling and free vibration of a curved FG microbeam have been investigated, based on strain gradient theory (SGT) theory and Timoshenko beam model. Distribution of structural materials varies continuously in thickness direction due to power-law exponent. Unlike classical models, this novel model employs three length scale parameters which can capture the size effect. This work is based on SGT theory and Timoshenko beam model. Governing equation of motion and associated boundary condition have been developed based on Hamilton's principle, which is the specified case of virtual work theorem. In continuance, final differential equations were solved by Navier's solution method and the results have been presented. Moreover, influences of dimensionless length-to-thickness ratio (aspect ratio), dimensionless length scale parameter, power-law exponent, temperature difference and arc angle for various values of mode numbers on natural frequency and critical temperature by considering temperature-dependent material properties have been investigated. In order to validate accomplished study, some of the results were compared with those of previous works. It has been concluded that applying a thermomechanical loading on a FG microbeam causes the natural frequency to become more sensitive about variations of geometrical, physical and mechanical properties and characteristics.

  1. Discovery and Classification of DES15C2ir by SALT

    NASA Astrophysics Data System (ADS)

    Kasai, E.; Bassett, B.; Crawford, S.; Vaisanen, P.; Smith, M.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Scolnic, D.; Covarrubias, R. A.; Brout, D. J.; Fischer, J. A.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; D'Andrea, C.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.

    2015-09-01

    We report optical spectroscopy of a supernova candidate discovered by the Dark Energy Survey (ATel #4668). The spectrum (400-850nm) of DES15C2ir was obtained using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT).

  2. 17 CFR 240.15c2-8 - Delivery of prospectus.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Delivery of prospectus. 240... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c2-8 Delivery of... delivery requirements of section 5(b) (1) and (2) of the Securities Act of 1933. (i) This section shall...

  3. 17 CFR 240.15c2-8 - Delivery of prospectus.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Delivery of prospectus. 240... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c2-8 Delivery of... delivery requirements of section 5(b) (1) and (2) of the Securities Act of 1933. (i) This section shall...

  4. 17 CFR 240.15c1-2 - Fraud and misrepresentation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 4 2014-04-01 2014-04-01 false Fraud and misrepresentation... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and... any act, practice, or course of business which operates or would operate as a fraud or deceit upon...

  5. 17 CFR 240.15c1-2 - Fraud and misrepresentation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 3 2013-04-01 2013-04-01 false Fraud and misrepresentation... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and... any act, practice, or course of business which operates or would operate as a fraud or deceit upon...

  6. 17 CFR 240.15c1-2 - Fraud and misrepresentation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 17 Commodity and Securities Exchanges 3 2012-04-01 2012-04-01 false Fraud and misrepresentation... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and... any act, practice, or course of business which operates or would operate as a fraud or deceit upon...

  7. 17 CFR 240.15c1-2 - Fraud and misrepresentation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Fraud and misrepresentation... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and... any act, practice, or course of business which operates or would operate as a fraud or deceit upon...

  8. 17 CFR 240.15c1-2 - Fraud and misrepresentation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Fraud and misrepresentation... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and... any act, practice, or course of business which operates or would operate as a fraud or deceit upon...

  9. 17 CFR 240.15c3-1 - Net capital requirements for brokers or dealers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... term “dealer” includes: (A) Any broker or dealer that endorses or writes options otherwise than on a... conformity with paragraph (b)(2) of § 240.15c2-4, so long as those persons engage in no other dealer... application by an OTC derivatives dealer when calculating net capital to use the market risk standards...

  10. Revisiting the high temperature metamorphic field gradient of the Ryoke Belt (SW Japan): New constraints from the Iwakuni-Yanai area

    NASA Astrophysics Data System (ADS)

    Skrzypek, Etienne; Kawakami, Tetsuo; Hirajima, Takao; Sakata, Shuhei; Hirata, Takafumi; Ikeda, Takeshi

    2016-09-01

    We revisit the origin of the metamorphic field gradient exposed in the Ryoke Belt (SW Japan) - the type locality for low pressure/high temperature (LP/HT) conditions - based on combined structural, petrological and geochronological data from the Iwakuni-Yanai area (W Ryoke). In this area metasedimentary rocks pass from schist in the north to partly migmatitic paragneiss in the south, and are surrounded by numerous granitoid bodies. Three deformation phases are emphasized; an accretionary-stage or burial deformation of weak intensity (D0), a vertical shortening (D1) which generated a subhorizontal, locally extensional foliation in the southern gneiss zone, and E-W upright folding (D2) which reworked both the northern schist and southern gneiss zones. Crystallization-deformation relationships indicate that, in the schist zone, most andalusite, cordierite and mica porphyroblasts formed after D0 and before D1. Syn-D1 mineral assemblages define E-W trending metamorphic zones with increasing grade from north to south, and rare syn-D2 parageneses reveal a similar pattern. Continuous magmatic activity lasted from ca. 105 to 94 Ma. The oldest granitoids (Shimokuhara, Soo, Namera), found in the western part of the belt, were emplaced below schistose rocks at 105-100 Ma. Subsequently, syn- to post-D1 granodiorite (Gamano) intruded concordantly with the foliation of southern, high-grade gneissic rocks from 100 to 94 Ma. A large, syn-D1 pluton (Kibe) intruded the center of the belt at 98 Ma, whereas a younger granite (Iwakuni) and its satellite dykes were emplaced to the northeast at 96-94 Ma. Constraints on the timing of D1 (103-99 Ma) and the likely diachronous D2 phase (100-94 Ma) suggest a deformation continuum during magma intrusion and metamorphism. We conclude that the exposed metamorphic field gradient is an apparent, but fortuitous, alignment of P-T data resulting from spatially and temporally distinct thermal events. Peak temperature conditions in the relatively

  11. Chill coma temperatures appear similar along a latitudinal gradient, in contrast to divergent chill coma recovery times, in two widespread ant species.

    PubMed

    Maysov, Andrey

    2014-08-01

    Populations of widely distributed ectotherms demonstrate different cold resistance corresponding to the local climate. However, efficiently thermoregulating ectotherms could avoid divergence in cold resistance. Two species of ants, previously shown to even out latitudinal differences of mean summer temperatures in their nests, were used to test this hypothesis by comparing the temperature dependence of cold resistance in three distant populations (from 50°, 60° and 67°N). The species differ in habitat preferences, one (Myrmica rubra) being less stenotopic than the other (M. ruginodis). Therefore, three different predictions were made about their cold resistance: along the latitudinal gradient, it might be similar within the two species (because of thermoregulation within nests/habitats) or similar only in M. rubra (as a result of thermoregulation among habitats), or divergent at least in M. rubra (no effect of thermoregulation). Among populations of both species, neither differences nor latitudinal trends in chill coma temperature were statistically significant after 11 months of standard conditions, with or without cold hardening. In contrast, recovery time significantly differed among populations in both species, although its latitudinal trends were strongly curvilinear: in M. rubra, the intermediate population tended towards the slowest recovery, and in M. ruginodis, it tended towards the fastest. After 22 months, the patterns remained the same, except that M. ruginodis showed a significant linear latitudinal trend in chill coma temperature (with no significant populational differences). Hence, thermoregulation, both within and among habitats, apparently does keep chill coma temperatures similar. Recovery rate demonstrates divergence, but its curvilinear trends suggest a connection with climates experienced by ancestral populations.

  12. Assessment of the effect of parallel temperature gradients in the JET SOL on Te measured by divertor target Langmuir probes

    NASA Astrophysics Data System (ADS)

    Ďuran, I.; Ješko, K.; Fuchs, V.; Groth, M.; Guillemaut, C.; Gunn, J. P.; Horacek, J.; Pitts, R. A.; Tskhakaya, D.

    2015-08-01

    Higher than expected electron temperatures (Te) are often measured by divertor Langmuir probes (LP) in high recycling and detached regimes in JET and other tokamaks. As a possible mechanism to explain this discrepancy, we investigate the effect of penetration of fast, almost collisionless electrons connecting the hot upstream scrape-off layer (SOL) region to the divertor targets in JET. We simulate the electron velocity distribution function (EVDF) near the divertor targets using a simple 1D kinetic model using parallel SOL profiles from EDGE2D-EIRENE simulations. The resulting EVDF is used to construct synthetic LP current-voltage (IV) characteristics and evaluation of Te is performed in the same way as for experimental data. Results indicate that the process does not explain the anomalously high Te values estimated from the target probe measurements if the EDGE2D-EIRENE simulated parallel profiles are a good representation of reality.

  13. Gradient networks

    NASA Astrophysics Data System (ADS)

    Toroczkai, Zoltán; Kozma, Balázs; Bassler, Kevin E.; Hengartner, N. W.; Korniss, G.

    2008-04-01

    Gradient networks are defined (Toroczkai and Bassler 2004 Nature 428 716) as directed graphs formed by local gradients of a scalar field distributed on the nodes of a substrate network G. We present the derivation for some of the general properties of gradient graphs and give an exact expression for the in-degree distribution R(l) of the gradient network when the substrate is a binomial (Erd{\\;\\kern -0.10em \\raise -0.35ex \\{{^{^{\\prime\\prime}}}}\\kern -0.57em \\o} s-Rényi) random graph, G_{N,p} , and the scalars are independent identically distributed (i.i.d.) random variables. We show that in the limit N \\to \\infty, p \\to 0, z = pN = \\mbox{const} \\gg 1, R(l)\\propto l^{-1} for l < l_c = z , i.e., gradient networks become scale-free graphs up to a cut-off degree. This paper presents the detailed derivation of the results announced in Toroczkai and Bassler (2004 Nature 428 716).

  14. Influence of river level on temperature and hydraulic gradients in chum and fall Chinook salmon spawning areas downstream of Bonneville Dam, Columbia River

    SciTech Connect

    Geist, David R.; Arntzen, Evan V.; Murray, Christopher J.; McGrath, Kathy; Bott, Yi-Ju; Hanrahan, Timothy P.

    2008-02-01

    Chum (Oncorhynchus keta) and fall Chinook (O. tshawytscha) salmon segregate spatially during spawning in the Ives Island side channel of the lower Columbia River downstream from Bonneville Dam. Previous research during one spawning season (2000) suggested that these species selected spawning habitats based on differences in hyporheic