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Sample records for background temperature fluctuations

  1. Non-Gaussianity in the Cosmic Microwave Background temperature fluctuations from cosmic (super-)strings

    SciTech Connect

    Takahashi, Keitaro; Naruko, Atsushi; Sendouda, Yuuiti; Yamauchi, Daisuke; Sasaki, Misao; Yoo, Chul-Moon E-mail: naruko@yukawa.kyoto-u.ac.jp E-mail: yamauchi@yukawa.kyoto-u.ac.jp E-mail: misao@yukawa.kyoto-u.ac.jp

    2009-10-01

    We compute analytically the small-scale temperature fluctuations of the cosmic microwave background from cosmic (super-)strings and study the dependence on the string intercommuting probability P. We develop an analytical model which describes the evolution of a string network and calculate the numbers of string segments and kinks in a horizon volume. Then we derive the probability distribution function (pdf) which takes account of finite angular resolution of observation. The resultant pdf consists of a Gaussian part due to frequent scatterings by long string segments and a non-Gaussian tail due to close encounters with kinks. The dispersion of the Gaussian part is reasonably consistent with that obtained by numerical simulations by Fraisse et al.. On the other hand, the non-Gaussian tail contains two phenomenological parameters which are determined by comparison with the numerical results for P = 1. Extrapolating the pdf to the cases with P < 1, we predict that the non-Gaussian feature is suppressed for small P.

  2. Radio brightness distribution within cosmic background fluctuations

    NASA Astrophysics Data System (ADS)

    Sazhin, M. V.

    1985-08-01

    The angular fluctuations delta T in the microwave background temperature constitute a random process. Calculations are performed for the number of 'pips' above a base level that might be produced by primordial scalar density perturbations or gravitational waves. The flux density expected for typical pips is determined, as well as the mean solid angle subtended by a pip that would exceed a level three times the dispersion in delta T.

  3. Topology of microwave background fluctuations - Theory

    NASA Technical Reports Server (NTRS)

    Gott, J. Richard, III; Park, Changbom; Bies, William E.; Bennett, David P.; Juszkiewicz, Roman

    1990-01-01

    Topological measures are used to characterize the microwave background temperature fluctuations produced by 'standard' scenarios (Gaussian) and by cosmic strings (non-Gaussian). Three topological quantities: total area of the excursion regions, total length, and total curvature (genus) of the isotemperature contours, are studied for simulated Gaussian microwave background anisotropy maps and then compared with those of the non-Gaussian anisotropy pattern produced by cosmic strings. In general, the temperature gradient field shows the non-Gaussian behavior of the string map more distinctively than the temperature field for all topology measures. The total contour length and the genus are found to be more sensitive to the existence of a stringy pattern than the usual temperature histogram. Situations when instrumental noise is superposed on the map, are considered to find the critical signal-to-noise ratio for which strings can be detected.

  4. Characterizing the Cosmic Infrared Background Fluctuations

    NASA Astrophysics Data System (ADS)

    Li, Yanxia; Hasinger, Guenther; Cappelluti, Nico; Cappelluti, Nico; Arendt, Richard G.

    2016-01-01

    A salient feature of the Cosmic Infrared Background (CIB) fluctuations is that their spatial power spectrum rises a factor of ~10 above the expected contribution from all known sources at angular scales >20". A tantalizing large-scale correlation signal between the residual Cosmic X-ray Background (CXB) and CIB found in the Extended Groth Strip (EGS) further suggests that at least 20% of the CIB fluctuations are associated with accreting X-ray sources, with efficient energy production similar to black holes. However, there is still a controversy about the sources that produce the excess flux. They could be faint, local populations with different spatial distribution from other known galaxies, or high-z populations at the epoch of reionization that we know little of. Constraining the origin of the CIB fluctuations will help to establish our understanding of the overall cosmic energy budget. We will combine the archival Spitzer/IRAC and the Chandra data of the Cosmic Evolution Survey (COSMOS), to accurately measure the source-subtracted CIB and CXB fluctuations to the largest angular scale (~1-2 deg) to date. The newly discovered link between CIB and CXB fluctuations found in the EGS will be revisited in the COSMOS, which provides better photon statistics. We will present current state of data collection and analysis progress.

  5. Characterizing the Cosmic Infrared Background Fluctuations

    NASA Astrophysics Data System (ADS)

    Li, Yanxia

    2015-08-01

    A salient feature of the Cosmic Infrared Background (CIB) fluctuations is that their spatial power spectrum rises a factor of ~10 above the expected contribution from all known sources at angular scales >20‧‧. A tantalizing large-scale correlation signal between the residual Cosmic X-ray Background (CXB) and CIB found in the Extended Groth Strip (EGS) further suggests that at least 20% of the CIB fluctuations are associated with accreting X-ray sources, with efficient energy production similar to black holes. However, there is still a controversy about the sources that produce the excess flux. They could be faint, local populations with different spatial distribution from other known galaxies, e.g., intra-halo light (emitted from stars in the outskirts of local galaxies), or really high-z populations at the epoch of reionization that we know little of. Constraining the origin of the CIB fluctuations will help to establish our understanding of the overall cosmic energy budget.In this talk, we will present our plan to break down this controversy, current state of data collection and analysis.(1) We will combine the archival Spitzer/IRAC and Herschel/PACS data, with the Chandra data of the Cosmic Evolution Survey (COSMOS), to accurately measure the source-subtracted CIB and CXB fluctuations to the largest angular scale (~1-2 deg) to date. The newly discovered link between CIB and CXB fluctuations found in the EGS will be revisited in the COSMOS, which provides better photon statistics. (2) We have been working on cross-correlating the unresolved background with the discrete sources detected at shorter wavelengths (1- 2μm), using ground-based multi-wavelength observations. In addition to exploring the Pan-STARRS 3PI and Medium Deep Survey database, we have also been awarded the telescope time of CFHT/WIRCam and Subaru/Hyper-Suprime-Cam for this purpose. The preliminary data analysis will be presented.

  6. Cosmic Infrared Background Fluctuations and Zodiacal Light

    NASA Astrophysics Data System (ADS)

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

    2016-06-01

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS field at low ecliptic latitude where the zodiacal light intensity varies by factors of ˜2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (≳100″) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

  7. Ultraviolet background fluctuations with clustered sources

    NASA Astrophysics Data System (ADS)

    Desjacques, Vincent; Dizgah, Azadeh Moradinezhad; Biagetti, Matteo

    2014-11-01

    We develop a count-in-cells approach to the distribution of ultraviolet background fluctuations that includes source clustering. We demonstrate that an exact expression can be obtained if the clustering of ionizing sources follows the hierarchical ansatz. In this case, the intensity distribution depends solely on their two-point correlation function. We show that the void scaling function of high-redshift mock quasars is consistent with the negative binomial form, before applying our formalism to the description of He II-ionizing fluctuations at the end of helium reionization. The model inputs are the observed quasar luminosity function and two-point correlation at z ˜ 3. We find that, for an (comoving) attenuation length ≲55 Mpc, quasar clustering contributes less than 30 per cent of the variance of intensity fluctuations so long as the quasar correlation length does not exceed ˜15 Mpc. We investigate also the dependence of the intensity distribution on the large-scale environment. Differences in the mean He II-ionizing intensity between low- and high-density regions could be a factor of few if the sources are highly clustered. An accurate description of quasar demographics and their correlation with strong absorption systems is required to make more precise predictions.

  8. Non-Gaussian microwave background fluctuations from nonlinear gravitational effects

    NASA Technical Reports Server (NTRS)

    Salopek, D. S.; Kunstatter, G. (Editor)

    1991-01-01

    Whether the statistics of primordial fluctuations for structure formation are Gaussian or otherwise may be determined if the Cosmic Background Explorer (COBE) Satellite makes a detection of the cosmic microwave-background temperature anisotropy delta T(sub CMB)/T(sub CMB). Non-Gaussian fluctuations may be generated in the chaotic inflationary model if two scalar fields interact nonlinearly with gravity. Theoretical contour maps are calculated for the resulting Sachs-Wolfe temperature fluctuations at large angular scales (greater than 3 degrees). In the long-wavelength approximation, one can confidently determine the nonlinear evolution of quantum noise with gravity during the inflationary epoch because: (1) different spatial points are no longer in causal contact; and (2) quantum gravity corrections are typically small-- it is sufficient to model the system using classical random fields. If the potential for two scalar fields V(phi sub 1, phi sub 2) possesses a sharp feature, then non-Gaussian fluctuations may arise. An explicit model is given where cold spots in delta T(sub CMB)/T(sub CMB) maps are suppressed as compared to the Gaussian case. The fluctuations are essentially scale-invariant.

  9. Mathematical Background of 1/f Fluctuations

    SciTech Connect

    Musha, Toshimitsu

    2009-04-23

    Energy of harmonic oscillators in equilibrium decays exponentially in time when they are coupled in quadratic forms in amplitudes. In reality, however, their Hamiltonian includes higher-order coupling terms. Not all of the higher-order coupling terms contribute to the energy decay of oscillators after averaging over reservoir oscillators, and we find that one of the lowest higher-order terms makes a finite contribution to the energy decay. This effect is equivalently represented by a modified coupling coefficient of quadratic coupling terms. This modification works as a positive feedback to the action-reaction process between oscillators. Eventually the modified coupling terms generate 1/f fluctuations in energy partition among oscillators in equilibrium. It is concluded that 1/f type of energy partition is observable with harmonic oscillators if they obey the Bose-Einstein statistics regardless of whether the collective system is classical or quantum mechanical regime.

  10. Temperature-polarization correlations from tensor fluctuations

    SciTech Connect

    Crittenden, R.G.; Coulson, D.; Turok, N.G. |

    1995-11-15

    We study the polarization-temperature correlations on the cosmic microwave sky resulting from an initial scale-invariant spectrum of tensor (gravity wave) fluctuations, such as those which might arise during inflation. The correlation function has the opposite sign to that for scalar fluctuations on large scales, raising the possibility of a direct determination of whether the microwave anisotropies have a significant tensor component. We briefly discuss the important problem of estimating the expected foreground contamination.

  11. Classical and quantum temperature fluctuations via holography

    SciTech Connect

    Balatsky, Alexander V.; Gudnason, Sven Bjarke; Thorlacius, Larus; Zarembo, Konstantin; Krikun, Alexander; Kedem, Yaron

    2014-05-27

    We study local temperature fluctuations in a 2+1 dimensional CFT on the sphere, dual to a black hole in asymptotically AdS space-time. The fluctuation spectrum is governed by the lowest-lying hydrodynamic sound modes of the system whose frequency and damping rate determine whether temperature fluctuations are thermal or quantum. We calculate numerically the corresponding quasinormal frequencies and match the result with the hydrodynamics of the dual CFT at large temperature. As a by-product of our analysis we determine the appropriate boundary conditions for calculating low-lying quasinormal modes for a four-dimensional Reissner-Nordstrom black hole in global AdS.

  12. THE COSMIC NEAR-INFRARED BACKGROUND. II. FLUCTUATIONS

    SciTech Connect

    Fernandez, Elizabeth R.; Komatsu, Eiichiro; Shapiro, Paul R.; Iliev, Ilian T.

    2010-02-20

    The near-infrared background (NIRB) is one of a few methods that can be used to observe the redshifted light from early stars at a redshift of 6 and above, and thus it is imperative to understand the significance of any detection or nondetection of the NIRB. Fluctuations of the NIRB can provide information on the first structures, such as halos and their surrounding ionized regions in the intergalactic medium (IGM). We combine, for the first time, N-body simulations, radiative transfer code, and analytic calculations of luminosity of early structures to predict the angular power spectrum (C{sub l} ) of fluctuations in the NIRB. We study in detail the effects of various assumptions about the stellar mass, the initial mass spectrum of stars, the metallicity, the star formation efficiency (f{sub *}), the escape fraction of ionizing photons (f{sub esc}), and the star formation timescale (t{sub SF}), on the amplitude as well as the shape of C{sub l} . The power spectrum of NIRB fluctuations is maximized when f{sub *} is the largest (as C{sub l} {proportional_to} f {sup 2}{sub *}) and f{sub esc} is the smallest (as more nebular emission is produced within halos). A significant uncertainty in the predicted amplitude of C{sub l} exists due to our lack of knowledge of t{sub SF} of these early populations of galaxies, which is equivalent to our lack of knowledge of the mass-to-light ratio of these sources. We do not see a turnover in the NIRB angular power spectrum of the halo contribution, which was claimed to exist in the literature, and explain this as the effect of high levels of nonlinear bias that was ignored in the previous calculations. This is partly due to our choice of the minimum mass of halos contributing to NIRB ({approx}2 x 10{sup 9} M{sub sun}), and a smaller minimum mass, which has a smaller nonlinear bias, may still exhibit a turnover. Therefore, our results suggest that both the amplitude and shape of the NIRB power spectrum provide important information

  13. Studying extragalactic background fluctuations with the Cosmic Infrared Background ExpeRiment 2 (CIBER-2)

    NASA Astrophysics Data System (ADS)

    Lanz, Alicia; Arai, Toshiaki; Battle, John; Bock, James; Cooray, Asantha; Hristov, Viktor; Korngut, Phillip; Lee, Dae Hee; Mason, Peter; Matsumoto, Toshio; Matsuura, Shuji; Morford, Tracy; Onishi, Yosuke; Shirahata, Mai; Tsumura, Kohji; Wada, Takehiko; Zemcov, Michael

    2014-08-01

    Fluctuations in the extragalactic background light trace emission from the history of galaxy formation, including the emission from the earliest sources from the epoch of reionization. A number of recent near-infrared measure- ments show excess spatial power at large angular scales inconsistent with models of z < 5 emission from galaxies. These measurements have been interpreted as arising from either redshifted stellar and quasar emission from the epoch of reionization, or the combined intra-halo light from stars thrown out of galaxies during merging activity at lower redshifts. Though astrophysically distinct, both interpretations arise from faint, low surface brightness source populations that are difficult to detect except by statistical approaches using careful observations with suitable instruments. The key to determining the source of these background anisotropies will be wide-field imaging measurements spanning multiple bands from the optical to the near-infrared. The Cosmic Infrared Background ExpeRiment 2 (CIBER-2) will measure spatial anisotropies in the extra- galactic infrared background caused by cosmological structure using six broad spectral bands. The experiment uses three 2048 x 2048 Hawaii-2RG near-infrared arrays in three cameras coupled to a single 28.5 cm telescope housed in a reusable sounding rocket-borne payload. A small portion of each array will also be combined with a linear-variable filter to make absolute measurements of the spectrum of the extragalactic background with high spatial resolution for deep subtraction of Galactic starlight. The large field of view and multiple spectral bands make CIBER-2 unique in its sensitivity to fluctuations predicted by models of lower limits on the luminosity of the first stars and galaxies and in its ability to distinguish between primordial and foreground anisotropies. In this paper the scientific motivation for CIBER-2 and details of its first flight instrumentation will be discussed, including

  14. Fluctuations and effective temperatures in coarsening

    NASA Astrophysics Data System (ADS)

    Corberi, Federico; Cugliandolo, Leticia F.

    2009-05-01

    We study dynamic fluctuations in non-disordered finite dimensional ferromagnetic systems quenched to the critical point and the low temperature phase. We investigate the fluctuations of two two-time quantities, called χ and C, the averages of which yield the self-linear response and correlation functions. We introduce a restricted average of the χs, summing over all configurations with a given value of C. We find that the restricted average langχrangC obeys a scaling form, and that the slope of the scaling function approaches the universal value X_\\infty of the limiting effective temperature in the long time limit and for C\\to 0 . Our results tend to confirm the expectation that time-reparameterization invariance is not realized in coarsening systems at criticality. Finally, we discuss possible experimental tests of our proposal.

  15. Quark number fluctuations at high temperatures

    SciTech Connect

    Petreczky, P.; Hegde, P.; Velytsky, A.

    2009-11-01

    We calculate the second, fourth and sixth order quark number fluctuations in the deconfined phase of 2+1 flavor QCD using lattices with temporal extent N{sub t} = 4,6,8 and 12. We consider light, strange and charm quarks. We use p4 action for valence quarks and gauge configurations generated with p4 action with physical value of the strange quark mass and light quark mass m{sub q} = 0.1 m{sub s} generated by the RBC-Bielefeld collaboration. We observe that for all quark masses the quark number fluctuations rapidly get close to the corresponding ideal gas limits. We compare our results to predictions of a quasi-particle model and resummed high temperature perturbative calculations. We also investigate correlations among different flavor channels.

  16. Fluctuations in the soft X-ray background

    NASA Technical Reports Server (NTRS)

    Barber, C. R.; Warwick, R. S.; Snowden, S. L.

    1996-01-01

    Eight overlapping Rosat position sensitive proportional counter (PSPC) observations are discussed. The data concern the Lockman hole region and were analyzed in the 0.1 keV to 0.4 keV band. The contribution of noncosmic contaminants and bright discrete sources were removed from the data. A strong anticorrelation with column density was detected. Evidence for significant excess fluctuations superimposed on this anticorrelation was found. The fluctuations' possible origins are discussed.

  17. THE TEMPERATURE OF THE COSMIC MICROWAVE BACKGROUND

    SciTech Connect

    Fixsen, D. J.

    2009-12-20

    The Far InfraRed Absolute Spectrophotometer data are independently recalibrated using the Wilkinson Microwave Anisotropy Probe data to obtain a cosmic microwave background (CMB) temperature of 2.7260 +- 0.0013. Measurements of the temperature of the CMB are reviewed. The determination from the measurements from the literature is CMB temperature of 2.72548 +- 0.00057 K.

  18. Multiplicity fluctuations due to the temperature fluctuations in high-energy nuclear collisions

    SciTech Connect

    Wilk, Grzegorz; Wlodarczyk, Zbigniew

    2009-05-15

    We investigate the multiplicity fluctuations observed in high-energy nuclear collisions attributing them to intrinsic fluctuations of temperature of the hadronizing system formed in such processes. To account for these fluctuations, we replace the usual Boltzmann-Gibbs (BG) statistics by the nonextensive Tsallis statistics characterized by the nonextensivity parameter q, with |q-1| being a direct measure of fluctuation. In the limit of vanishing fluctuations, q{yields}1 and Tsallis statistics converge to the usual BG. We evaluate the nonextensivity parameter q and its dependence on the hadronizing system size from the experimentally observed collision centrality dependence of the mean multiplicity and its variance Var(N). We attribute the observed system size dependence of q to the finiteness of the hadronizing source, with q=1 corresponding to an infinite, thermalized source with a fixed temperature, and with q>1 (which is observed) corresponding to a finite source in which both the temperature and energy fluctuate.

  19. Mesoscale Temperature Fluctuations in the Southern Hemisphere Stratosphere

    NASA Technical Reports Server (NTRS)

    Gary, Bruce L.

    2008-01-01

    Isentrope surfaces in the Southern Hemisphere stratosphere reveal that air parcels undergo mesoscale temperature fluctuations that depend on latitude and season. The largest temperature fluctuations occur at high latitude winter, whereas the smallest fluctuations occur at high latitude summer. This is the same pattern found for the Northern Hemisphere stratosphere. However, the amplitude of the seasonal dependence in the Southern Hemisphere is only 37% of the Northern Hemisphere's seasonal amplitude.

  20. Minute Temperature Fluctuations Detected in Eta Bootis

    NASA Astrophysics Data System (ADS)

    1994-11-01

    periods around 20 minutes. These periods are longer than those of the Sun, as expected for a star that is larger and heavier than the Sun. The figure accompanying this Press Release shows these oscillations in the form of a "power spectrum", i.e., the amount of temperature change at different values of the period. Most of the highest peaks correspond to the real oscillations in the star. The changes (fluctuations) of the temperature of Eta Bootis vary with the oscillation mode and, at the time of these observations, were mostly between 0.03 and 0.08 degrees. This diagramme provides the first strong evidence ever for solar-type oscillations in a star other than the Sun. An article with the detailed results will soon appear in the "Astronomical Journal". Agreement with Stellar Theory The measured periods of the main oscillation modes give important information about the interior of Eta Bootis. Theoretical models of the star have now been compared with these observations and the astronomers were pleased to find that the agreement is excellent, implying that current stellar theory is remarkably good. This shows that we apparently understand stars quite well, but there is of course still much to be learned. Future observations of this kind, with ground-based telescopes and possibly in a more distant future also from space, promise to open up a new and exciting way of studying stars. From now on, we will be able "to look inside" stars in great detail. Appendix: Spectral Analysis Dark spectral lines were first seen in the solar spectrum by the German physicist Johann Fraunhofer in 1814. Later, in the mid-nineteenth century, such lines were also seen in the spectra of other stars. It is now known that they are due to the upper, cooler layers in the solar and stellar atmospheres, whose atoms and molecules absorb the radiation from the hotter, deeper layers at specific wavelengths. These wavelengths serve as "footprints" of these atoms and molecules and allow astronomers to

  1. Proton resonant firehose instability: Temperature anisotropy and fluctuating field constraints

    NASA Astrophysics Data System (ADS)

    Gary, S. Peter; Li, Hui; O'Rourke, Sean; Winske, Dan

    1998-07-01

    The electromagnetic proton firehose instability may grow in a plasma if the proton velocity distribution is approximately bi-Maxwellian and T∥p>T⊥p, where the directional subscripts denote directions relative to the background magnetic field. Linear Vlasov dispersion theory in a homogeneous electron-proton plasma implies an instability threshold condition at constant maximum growth rate 1-T⊥p/T∥p=Sp/β∥pαp over 1<β∥p<=10 where β∥p≡8πnpT∥p/B02 and B0 is the background magnetic field. Here Sp and αp are fitting parameters and αp~=0.7. One- and two-dimensional initial value hybrid simulations of this growing mode are carried out under proton cyclotron resonant conditions in a homogeneous plasma on the initial domain 2<~β∥p<=100. The two-dimensional simulations show that enhanced fluctuations from this instability impose a bound on the proton temperature anisotropy of the form of the above equation with the fluid theory result αp~=1.0. On this domain both one- and two-dimensional simulations yield a new form for the upper bound on the fluctuating field energy density from the proton resonant firehose instability |δB|2/B02=SB+αBln(β∥p) where SB and αB are empirical parameters which are functions of the initial growth rate. This logarithmic behavior is qualitatively different from a fluid theory prediction and, like the anisotropy bound, should be subject to observational verification in any sufficiently homogeneous plasma in which the proton velocity distribution is approximately bi-Maxwellian.

  2. Maps of the little bangs through energy density and temperature fluctuations

    NASA Astrophysics Data System (ADS)

    Basu, Sumit; Chatterjee, Rupa; Nandi, Basanta K.; Nayak, Tapan K.

    2016-01-01

    Heavy-ion collisions at ultra-relativistic energies are often referred to as little bangs. We propose for the first time to map the heavy-ion collisions at ultra-relativistic energies, similar to the maps of the cosmic microwave background radiation, using fluctuations of energy density and temperature in small phase space bins. We study the evolution of fluctuations at each stage of the collision using an event-by-event hydrodynamic framework. We demonstrate the feasibility of making fluctuation maps from experimental data and its usefulness in extracting considerable information regarding the early stages of the collision and its evolution.

  3. AKARI Observation of the Sub-degree Scale Fluctuation of the Near-infrared Background

    NASA Astrophysics Data System (ADS)

    Seo, H. J.; Lee, Hyung Mok; Matsumoto, T.; Jeong, W.-S.; Lee, Myung Gyoon; Pyo, J.

    2015-07-01

    We report spatial fluctuation analysis of the sky brightness in the near-infrared from observations toward the north ecliptic pole (NEP) by the AKARI at 2.4 and 3.2 μm. As a follow-up study of our previous work on the Monitor field of AKARI, we used NEP deep survey data, which covered a circular area of about 0.4 square degrees, in order to extend fluctuation analysis at angular scales up to 1000″. We found residual fluctuation over the estimated shot noise at larger angles than the angular scale of the Monitor field. The excess fluctuation of the NEP deep field smoothly connects with that of the Monitor field at angular scales of a few hundred arcseconds and extends without any significant variation to larger angular scales up to 1000″. By comparing excess fluctuations at two wavelengths, we confirm a blue spectral feature similar to the result of the Monitor field. We find that the result of this study is consistent with Spitzer Space Telescope observations at 3.6 μm. The origin of the excess fluctuation in the near-infrared background remains to be determined, but we could exclude zodiacal light, diffuse Galactic light, and unresolved faint galaxies at low redshift based on the comparison with mid- and far-infrared brightness, ground-based near-infrared images.

  4. Influence of temperature fluctuations on infrared limb radiance: a new simulation code

    NASA Astrophysics Data System (ADS)

    Rialland, Valérie; Chervet, Patrick

    2006-08-01

    Airborne infrared limb-viewing detectors may be used as surveillance sensors in order to detect dim military targets. These systems' performances are limited by the inhomogeneous background in the sensor field of view which impacts strongly on target detection probability. This background clutter, which results from small-scale fluctuations of temperature, density or pressure must therefore be analyzed and modeled. Few existing codes are able to model atmospheric structures and their impact on limb-observed radiance. SAMM-2 (SHARC-4 and MODTRAN4 Merged), the Air Force Research Laboratory (AFRL) background radiance code can be used to in order to predict the radiance fluctuation as a result of a normalized temperature fluctuation, as a function of the line-of-sight. Various realizations of cluttered backgrounds can then be computed, based on these transfer functions and on a stochastic temperature field. The existing SIG (SHARC Image Generator) code was designed to compute the cluttered background which would be observed from a space-based sensor. Unfortunately, this code was not able to compute accurate scenes as seen by an airborne sensor especially for lines-of-sight close to the horizon. Recently, we developed a new code called BRUTE3D and adapted to our configuration. This approach is based on a method originally developed in the SIG model. This BRUTE3D code makes use of a three-dimensional grid of temperature fluctuations and of the SAMM-2 transfer functions to synthesize an image of radiance fluctuations according to sensor characteristics. This paper details the working principles of the code and presents some output results. The effects of the small-scale temperature fluctuations on infrared limb radiance as seen by an airborne sensor are highlighted.

  5. Cosmic Infrared Background Fluctuations in Deep Spitzer Infrared Array Camera Images: Data Processing and Analysis

    NASA Technical Reports Server (NTRS)

    Arendt, Richard; Kashlinsky, A.; Moseley, S.; Mather, J.

    2010-01-01

    This paper provides a detailed description of the data reduction and analysis procedures that have been employed in our previous studies of spatial fluctuation of the cosmic infrared background (CIB) using deep Spitzer Infrared Array Camera observations. The self-calibration we apply removes a strong instrumental signal from the fluctuations that would otherwise corrupt the results. The procedures and results for masking bright sources and modeling faint sources down to levels set by the instrumental noise are presented. Various tests are performed to demonstrate that the resulting power spectra of these fields are not dominated by instrumental or procedural effects. These tests indicate that the large-scale ([greater, similar]30') fluctuations that remain in the deepest fields are not directly related to the galaxies that are bright enough to be individually detected. We provide the parameterization of these power spectra in terms of separate instrument noise, shot noise, and power-law components. We discuss the relationship between fluctuations measured at different wavelengths and depths, and the relations between constraints on the mean intensity of the CIB and its fluctuation spectrum. Consistent with growing evidence that the [approx]1-5 [mu]m mean intensity of the CIB may not be as far above the integrated emission of resolved galaxies as has been reported in some analyses of DIRBE and IRTS observations, our measurements of spatial fluctuations of the CIB intensity indicate the mean emission from the objects producing the fluctuations is quite low ([greater, similar]1 nW m-2 sr-1 at 3-5 [mu]m), and thus consistent with current [gamma]-ray absorption constraints. The source of the fluctuations may be high-z Population III objects, or a more local component of very low luminosity objects with clustering properties that differ from the resolved galaxies. Finally, we discuss the prospects of the upcoming space-based surveys to directly measure the epochs

  6. Effect of Background Fluctuations on Kinetic Alfvén Wave Turbulence

    NASA Astrophysics Data System (ADS)

    Kumari, Anju; Sharma, R. P.

    2016-07-01

    The localization of Kinetic Alfvén wave (KAW) caused by finite amplitude background density fluctuations has been studied in intermediate beta plasma. The dynamical equations are derived taking into account the ponderomotive nonlinearity of the KAW as well as background density fluctuations and then studied numerically. Numerical simulation has been performed to analyze the effect of background density fluctuations on localized structures and resulting turbulent spectrum of KAW applicable to the magnetopause. Simulation results reveal that the power spectrum deviates from Kolmogorov scaling at the transverse size of KAW, equal to ion gyroradius. Steepening of the power spectrum at shorter wavelengths may be accountable for heating and acceleration of the plasma particles. Thus the presented coupling suggests a mechanism of energy transfer from larger length-scales to smaller length-scales. The relevance of present investigation with observations collected from the THEMIS spacecraft in magnetopause is also discussed [Chaston et al., 2008]. Reference Chaston, C., J. Bonnell, J. P. McFadden, C. W. Carlson, C. Cully, O. Le Contel A. Roux, H. U. Auster, K. H. Glassmeier, V. Angelopoulos, C. T. Russell (2008), Turbulent heating and cross-field transport near the magnetopause from THEMIS, Geophys. Res. Lett., 35, L17S08.

  7. Density and temperature of bosons from quantum fluctuations

    NASA Astrophysics Data System (ADS)

    Zheng, Hua; Giuliani, Gianluca; Bonasera, Aldo

    2012-10-01

    A method to determine the density and temperature of a system is proposed based on quantum fluctuations typical of bosons in the limit where the temperature T is close to the critical temperature Tc for a Bose-Einstein condensate (BEC) at a given density ρ. Quadrupole and particle multiplicity fluctuations using Landau's theory of fluctuations near the critical point are derived. As an example, we apply our approach to heavy ion collisions using the Constrained Molecular Dynamics model (CoMD) which includes the Fermi statistics. The model shows some clusterization into deuteron (d) and alpha (α) clusters but it is not enough to reproduce available experimental data. We propose a modification of the collision term in the approach to include the possibility of α-α collisions. The relevant Bose-Einstein factor in the collision term is properly taken into account. This approach increases the yields of bosons relative to fermions closer to data. Boson fluctuations become larger than 1 as expected. If they are confirmed a new field of research could open up for a mixture of strongly interacting fermions and bosons which requires novel techniques both theoretically and experimentally.

  8. Ion temperature fluctuation measurements using a retarding field analyzer.

    PubMed

    Nedzelskiy, I S; Silva, C; Duarte, P; Fernandes, H

    2011-04-01

    The retarding field analyzer (RFA) is a widely used diagnostic tool for the ion temperature measurement in the scrape-off-layer (SOL) of the thermonuclear plasma devices. However, the temporal resolution in the standard RFA application is restricted to the ms timescale. In this paper, a dc operation of the RFA is considered, which allows for the measurement of the plasma ion temperature fluctuations. The method is based on the relation for the RFA current-voltage (I-V) characteristic resulted from a common RFA model of shifted Maxwellian distribution of the analyzed ions, and the measurements of two points on the exponentially decaying region of the I-V characteristic with two differently dc biased RFA electrodes. The method has been tested and compared with conventional RFA measurements of the ion temperature in the tokamak ISTTOK SOL plasma. An ion temperature of T(i) = 17 eV is obtained near the limiter position. The agreement between the results of the two methods is within ∼25%. The amplitude of the ion temperature fluctuations is found to be around 5 eV at this location. The method has been validated by taking into account the effect of fluctuations in the plasma potential and the noise contamination, proving the reliability of the results obtained. Finally, constrains to the method application are discussed that include a negligible electron emission from the RFA grids and the restriction to operate in the exponentially decaying region of the I-V characteristic. PMID:21529006

  9. Cosmic birefringence fluctuations and cosmic microwave background B-mode polarization

    NASA Astrophysics Data System (ADS)

    Lee, Seokcheon; Liu, Guo-Chin; Ng, Kin-Wang

    2015-06-01

    Recently, BICEP2 measurements of the cosmic microwave background (CMB) B-mode polarization has indicated the presence of primordial gravitational waves at degree angular scales, inferring the tensor-to-scalar ratio of r = 0.2 and a running scalar spectral index, provided that dust contamination is low. In this Letter, we show that the existence of the fluctuations of cosmological birefringence can give rise to CMB B-mode polarization that fits BICEP2 data with r < 0.11 and no running of the scalar spectral index. When dust contribution is taken into account, we derive an upper limit on the cosmological birefringence, Aβ2 < 0.0075, where A is the amplitude of birefringence fluctuations that couple to electromagnetism with a coupling strength β.

  10. Reconstructing Emission from Pre-reionization Sources with Cosmic Infrared Background Fluctuation Measurements by the JWST

    NASA Astrophysics Data System (ADS)

    Kashlinsky, A.; Mather, J. C.; Helgason, K.; Arendt, R. G.; Bromm, V.; Moseley, S. H.

    2015-05-01

    We present new methodology to use cosmic infrared background (CIB) fluctuations to probe sources at 10≲ z≲ 30 from a James Webb Space Telescope (JWST)/NIRCam configuration that will isolate known galaxies to 28 AB mag at 0.5-5 μm. At present significant mutually consistent source-subtracted CIB fluctuations have been identified in the Spitzer and AKARI data at ˜2-5 μm, but we demonstrate internal inconsistencies at shorter wavelengths in the recent CIBER data. We evaluate CIB contributions from remaining galaxies and show that the bulk of the high-z sources will be in the confusion noise of the NIRCam beam, requiring CIB studies. The accurate measurement of the angular spectrum of the fluctuations and probing the dependence of its clustering component on the remaining shot noise power would discriminate between the various currently proposed models for their origin and probe the flux distribution of its sources. We show that the contribution to CIB fluctuations from remaining galaxies is large at visible wavelengths for the current instruments precluding probing the putative Lyman-break of the CIB fluctuations. We demonstrate that with the proposed JWST configuration such measurements will enable probing the Lyman-break. We develop a Lyman-break tomography method to use the NIRCam wavelength coverage to identify or constrain, via the adjacent two-band subtraction, the history of emissions over 10≲ z≲ 30 as the universe comes out of the “Dark Ages.” We apply the proposed tomography to the current Spitzer/IRAC measurements at 3.6 and 4.5 μm, to find that it already leads to interestingly low upper limit on emissions at z≳ 30.

  11. Reconstructing Emission from Pre-Reionization Sources with Cosmic Infrared Background Fluctuation Measurements by the JWST

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.; Mather, J. C.; Helgason, K.; Arendt, R. G.; Bromm, V.; Moseley, S. H.

    2015-01-01

    We present new methodology to use cosmic infrared background (CIB) fluctuations to probe sources at 10 less than or approx. equal to z less than or approx. equal to 30 from a James Webb Space Telescope (JWST) NIRCam configuration that will isolate known galaxies to 28 AB mag at 0.55 m. At present significant mutually consistent source-subtracted CIB fluctuations have been identified in the Spitzer and AKARI data at 25 m, but we demonstrate internal inconsistencies at shorter wavelengths in the recent CIBER data. We evaluate CIB contributions from remaining galaxies and show that the bulk of the high-z sources will be in the confusion noise of the NIRCam beam, requiring CIB studies. The accurate measurement of the angular spectrum of the fluctuations and probing the dependence of its clustering component on the remaining shot noise power would discriminate between the various currently proposed models for their origin and probe the flux distribution of its sources. We show that the contribution to CIB fluctuations from remaining galaxies is large at visible wavelengths for the current instruments precluding probing the putative Lyman-break of the CIB fluctuations. We demonstrate that with the proposed JWST configuration such measurements will enable probing the Lyman-break. We develop a Lyman-break tomography method to use the NIRCam wavelength coverage to identify or constrain, via the adjacent two-band subtraction, the history of emissions over 10 less than or approx. equal to z less than or approx. equal to 30 as the universe comes out of the Dark Ages. We apply the proposed tomography to the current SpitzerIRAC measurements at 3.6 and 4.5 m, to find that it already leads to interestingly low upper limit on emissions at z greater than or approx. equal to 30.

  12. Small-scale spatial fluctuations in the soft-X-ray background

    NASA Astrophysics Data System (ADS)

    Kuntz, Kip Dee

    In order to isolate the diffuse extragalactic component of the soft X-ray background, we have used a combination of ROSAT All-Sky Survey and IRAS 100 mum data to separate the soft X-ray background into five components. We find a Local Hot Bubble similar to that described by Snowden et al (1998). We make a first calculation of the contribution by unresolved Galactic stars to the diffuse background. We constrain the normalization, of the Extragalactic Power Law (the contribution of the unresolved extragalactic point sources such as AGN, QSO's, and normal galaxies) to 9.5 +/- 0.9 keV cm -2 s-1 sr-1 keV -1, assuming a power-law index of 1.46. We show that the remaining emission, which is some combination of Galactic halo emission and the putative diffuse extragalactic emission, must be composed of at least two components which we have characterized by thermal spectra. The softer component has log T ˜ 6.08 and a patchy distribution; thus it is most probably part of the Galactic halo. The harder component has log T ˜ 6.46 and is nearly isotropic; some portion may be due to the Galactic halo and some portion may be due to the diffuse extragalactic emission. The maximum upper limit to the strength of the emission by the diffuse extragalactic component is the total of the hard component, ˜7.4 +/- 1.0 keV cm-2 s-1 sr-1 keV-1 in the ¾ keV band. We have made the first direct measure of the fluctuations due to the diffuse extragalactic emission in the ¾ keV band. Physical arguments suggest that small angular scale (˜10') fluctuations in the Local Hot Bubble or the Galactic halo will have very short dissipation times (˜105 years). Therefore, the fluctuation spectrum of the soft X-ray background should measure the distribution of the diffuse extragalactic emission. Using mosaics of deep, overlapping PSPC pointings, we find an autocorrelation function value of ˜0.0025 for 10' < theta < 20', and a value consistent with zero on larger scales. Measurement of the fluctuations

  13. Small-Scale Spatial Fluctuations in the Soft X-Ray Background

    NASA Astrophysics Data System (ADS)

    Kuntz, K. D.

    2001-02-01

    In order to isolate the diffuse extragalactic component of the soft X-ray background, we have used a combination of ROSAT All-Sky Survey and IRAS 100 micron data to separate the soft X-ray background into five components. We find a Local Hot Bubble similar to that described by Snowden et al (1998). We make a first calculation of the contribution by unresolved Galactic stars to the diffuse background. We constrain the normalization of the Extragalactic Power Law (the contribution of the unresolved extragalactic point sources such as AGN, QSO'S, and normal galaxies) to 9.5 +/- 0.9 keV/(sq cm s sr keV), assuming a power-law index of 1.46. We show that the remaining emission, which is some combination of Galactic halo emission and the putative diffuse extragalactic emission, must be composed of at least two components which we have characterized by thermal spectra. The softer component has log T - 6.08 and a patchy distribution; thus it is most probably part of the Galactic halo. The harder component has log T - 6.46 and is nearly isotropic; some portion may be due to the Galactic halo and some portion may be due to the diffuse extragalactic emission. The maximum upper limit to the strength of the emission by the diffuse extragalactic component is the total of the hard component, approx. 7.4 +/- 1.0 keV/(sq cm s sr keV) in the 3/4 keV band. We have made the first direct measure of the fluctuations due to the diffuse extragalactic emission in the 3/4 keV band. Physical arguments suggest that small angular scale (approx. 10') fluctuations in the Local Hot Bubble or the Galactic halo will have very short dissipation times (about 105 years). Therefore, the fluctuation spectrum of the soft X-ray background should measure the distribution of the diffuse extragalactic emission. Using mosaics of deep, overlapping PSPC pointings, we find an autocorrelation function value of approx. 0.0025 for 10' < theta < 20', and a value consistent with zero on larger scales. Measurement of

  14. Small-Scale Spatial Fluctuations in the Soft X-ray Background

    NASA Astrophysics Data System (ADS)

    Kuntz, K. D.

    2001-01-01

    In order to isolate the diffuse extragalactic component of the soft X-ray background, we have used a combination of ROSAT All-Sky Survey and IRAS 100 micrometer data to separate the soft X-ray background into five components: (1) We find a Local Hot Bubble similar to that described by Snowden et al.; (2) We make a first calculation of the contribution by unresolved galactic stars to the diffuse background; (3) We constrain the normalization of the Extragalactic Power Law (the contribution of the unresolved extragalactic point sources such as AGN, QSO's, and normal galaxies) to 9.5 +/- 0.9 keV/sq cm/s/sr/kEv, assuming a power-law index of 1.46; (4) We show that the remaining emission, which is some combination of galactic halo emission and the putative diffuse extragalactic emission, must be composed of at least two components which we have characterized by thermal spectra. The softer component has logT approx. = 6.08 and a patchy distribution; thus it is most probably part of the Galactic halo. The harder component has log T approx. = 6.46 and is nearly isotropic; some portion may be due to the Galactic halo and some portion may be due to the diffuse extragalactic emission. The maximum upper limit to the strength of the emission by the diffuse extragalactic component is the total of the hard component, approx. 7.4 +/- 1.0 keV/sq cm/s/sr/keV in the 3/4 keV band; (5) We have made the first direct measure of the fluctuations due to the diffuse extragalactic emission in the 1 keV band. Physical arguments suggest that small angular scale (approx. 10 min) fluctuations in the Local Hot Bubble or the Galactic halo will have very short dissipation times (approx. 105 years). Therefore, the fluctuation spectrum of the soft X-ray background should measure the distribution of the diffuse extragalactic emission. Using mosaics of deep, overlapping PSPC pointings, we find an autocorrelation function value of approx. 0.0025 for 10 min < theta < 20 min, and a value consistent with

  15. Effect of temperature and temperature fluctuation on thermophilic anaerobic digestion of cattle manure.

    PubMed

    El-Mashad, Hamed M; Zeeman, Grietje; van Loon, Wilko K P; Bot, Gerard P A; Lettinga, Gatze

    2004-11-01

    The influence of temperature, 50 and 60 degrees C, at hydraulic retention times (HRTs) of 20 and 10 days, on the performance of anaerobic digestion of cow manure has been investigated in completely stirred tank reactors (CSTRs). Furthermore, the effect of both daily downward and daily upward temperature fluctuations has been studied. In the daily downward temperature fluctuation regime the temperatures of each reactor was reduced by 10 degrees C for 10 h while in the daily upward fluctuation regime the temperature of each reactor was increased 10 degrees C for 5 h. The results show that the methane production rate at 60 degrees C is lower than that at 50 degrees C at all experimental conditions of imposed HRT except when downward temperature fluctuations were applied at an HRT of 10 days. It also was found that the free ammonia concentration not only affects the acetate-utilising bacteria but also the hydrolysis and acidification process. The upward temperature fluctuation affects the maximum specific methanogenesis activity more severely as compared to imposed downward temperature fluctuations. The results clearly reveal the possibility of using available solar energy at daytime to heat up the reactor(s) without the need of heat storage during nights, especially at an operational temperature of 50 degrees C and at a 20 days HRT, and without the jeopardising of the overheating. PMID:15246444

  16. Quantum-gravity fluctuations and the black-hole temperature

    NASA Astrophysics Data System (ADS)

    Hod, Shahar

    2015-05-01

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum.

  17. Tracing the first stars with fluctuations of the cosmic infrared background.

    PubMed

    Kashlinsky, A; Arendt, R G; Mather, J; Moseley, S H

    2005-11-01

    The deepest space- and ground-based observations find metal-enriched galaxies at cosmic times when the Universe was less than 1 Gyr old. These stellar populations had to be preceded by the metal-free first stars, known as 'population III'. Recent cosmic microwave background polarization measurements indicate that stars started forming early--when the Universe was < or =200 Myr old. It is now thought that population III stars were significantly more massive than the present metal-rich stellar populations. Although such sources will not be individually detectable by existing or planned telescopes, they would have produced significant cosmic infrared background radiation in the near-infrared, whose fluctuations reflect the conditions in the primordial density field. Here we report a measurement of diffuse flux fluctuations after removing foreground stars and galaxies. The anisotropies exceed the instrument noise and the more local foregrounds; they can be attributed to emission from population III stars, at an era dominated by these objects. PMID:16267547

  18. Problems encountered in fluctuating flame temperature measurements by thermocouple.

    SciTech Connect

    Donaldson, A. Burl; Lucero, Ralph E.; Gill, Walter; Yilmaz, Nadir

    2008-11-01

    Some thermocouple experiments were carried out in order to obtain sensitivity of thermocouple readings to fluctuations in flames and to determine if the average thermocouple reading was representative of the local volume temperature for fluctuating flames. The thermocouples considered were an exposed junction thermocouple and a fully sheathed thermocouple with comparable time constants. Either the voltage signal or indicated temperature for each test was recorded at sampling rates between 300-4,096 Hz. The trace was then plotted with respect to time or sample number so that time variation in voltage or temperature could be visualized and the average indicated temperature could be determined. For experiments where high sampling rates were used, the signal was analyzed using Fast Fourier Transforms (FFT) to determine the frequencies present in the thermocouple signal. This provided a basic observable as to whether or not the probe was able to follow flame oscillations. To enhance oscillations, for some experiments, the flame was forced. An analysis based on thermocouple time constant, coupled with the transfer function for a sinusoidal input was tested against the experimental results.

  19. Ionization and Cooling of a Hot Plasma with Temperature Fluctuations

    NASA Astrophysics Data System (ADS)

    Kholtygin, A. F.; Bratsev, V. F.; Ochkur, V. I.

    2002-01-01

    Cooling functions for a stationary plasma are calculated in a wide temperature range from 5·103 K to 108 K, both for a plasma with the solar abundances of elements and for a plasma with an anomalous chemical composition typical of Wolf—Rayet stars. The HILYS project is described, with the aim of calculating cross sections and rates of excitation by electron collision of atoms and ions with a charge Z 26 and principal electron quantum numbers n 10, needed to calculate the ionization and thermal states of a plasma and the development of methods of calculating the plasma's spectrum in the visible, UV, and x-ray ranges. The results of a calculation of cross sections and effective collision strengths obtained within the framework of the project are given. The influence of temperature fluctuations (T/T 0.16) on the relative ion abundances and the total cooling function is studied. It is shown that the presence of such fluctuations considerably increases the temperature range in which the abundances of ions of a given degree of ionization are not negligible, while the cooling function can differ considerably from that calculated for a one-temperature plasma. The contribution of dielectronic recombination to the total cooling function is investigated, and it proves to be significant only for a plasma with high abundances of heavy elements. The x-ray spectrum of the bright supergiant Pup is analyzed.

  20. Problems Encountered in Fluctuating Flame Temperature Measurements by Thermocouple

    PubMed Central

    Yilmaz, Nadir; Gill, Walt; Donaldson, A. Burl; Lucero, Ralph E.

    2008-01-01

    Some thermocouple experiments were carried out in order to obtain sensitivity of thermocouple readings to fluctuations in flames and to determine if the average thermocouple reading was representative of the local volume temperature for fluctuating flames. The thermocouples considered were an exposed junction thermocouple and a fully sheathed thermocouple with comparable time constants. Either the voltage signal or indicated temperature for each test was recorded at sampling rates between 300-4,096 Hz. The trace was then plotted with respect to time or sample number so that time variation in voltage or temperature could be visualized and the average indicated temperature could be determined. For experiments where high sampling rates were used, the signal was analyzed using Fast Fourier Transforms (FFT) to determine the frequencies present in the thermocouple signal. This provided a basic observable as to whether or not the probe was able to follow flame oscillations. To enhance oscillations, for some experiments, the flame was forced. An analysis based on thermocouple time constant, coupled with the transfer function for a sinusoidal input was tested against the experimental results.

  1. Objective differentiation of neonatal EEG background grades using detrended fluctuation analysis

    PubMed Central

    Matic, Vladimir; Cherian, Perumpillichira Joseph; Koolen, Ninah; Ansari, Amir H.; Naulaers, Gunnar; Govaert, Paul; Van Huffel, Sabine; De Vos, Maarten; Vanhatalo, Sampsa

    2015-01-01

    A quantitative and objective assessment of background electroencephalograph (EEG) in sick neonates remains an everyday clinical challenge. We studied whether long range temporal correlations quantified by detrended fluctuation analysis (DFA) could be used in the neonatal EEG to distinguish different grades of abnormality in the background EEG activity. Long-term EEG records of 34 neonates were collected after perinatal asphyxia, and their background was scored in 1 h epochs (8 h in each neonate) as mild, moderate or severe. We applied DFA on 15 min long, non-overlapping EEG epochs (n = 1088) filtered from 3 to 8 Hz. Our formal feasibility study suggested that DFA exponent can be reliably assessed in only part of the EEG epochs, and in only relatively short time scales (10–60 s), while it becomes ambiguous if longer time scales are considered. This prompted further exploration whether paradigm used for quantifying multifractal DFA (MF-DFA) could be applied in a more efficient way, and whether metrics from MF-DFA paradigm could yield useful benchmark with existing clinical EEG gradings. Comparison of MF-DFA metrics showed a significant difference between three visually assessed background EEG grades. MF-DFA parameters were also significantly correlated to interburst intervals quantified with our previously developed automated detector. Finally, we piloted a monitoring application of MF-DFA metrics and showed their evolution during patient recovery from asphyxia. Our exploratory study showed that neonatal EEG can be quantified using multifractal metrics, which might offer a suitable parameter to quantify the grade of EEG background, or to monitor changes in brain state that take place during long-term brain monitoring. PMID:25954174

  2. Response of the ice sheets to fluctuating temperatures

    NASA Astrophysics Data System (ADS)

    Bøgeholm Mikkelsen, Troels; Grinsted, Aslak; Ditlevsen, Peter

    2016-04-01

    Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing tempera- tures. Using coupled climate and ice sheet models long time forecasting is often made computationally feasible by running the ice sheet model in off-line mode, such that the temperature and precipitation fields govern- ing the mass balance of the ice sheets are taken to be constant over time. As the temperature and precipitation fluctuates, the asymmetry in the typical time scales for accumulation and ablation would result in a bias in the resulting mass balance of the ice sheet. We show that the steady state of the ice sheet is biased toward larger size of the ice sheet, if the short time scale fluctuations in temperature are not taken into account. This could potentially imply that the critical global temperature increase for ice sheet collapse is overestimated, thus the risk of collapse in a given climate change scenario underestimated. Our results highlight the need to consider the variability and not only the mean of the forcing of the mass balance of the ice sheet. We estimate that the effect of temperature variability on surface mass balance of the Greenland Ice Sheet in recent ensemble forecasting should be adjusted downward by as much as 10 percent of the present day observed value, if assuming a 2 degree warming. We are thus closer to a potential tipping point, than previously anticipated. Many predicted scenarios of the future climate show an increased variability in temperature over much of the Earth. In light of the findings presented here, it is important to gauge the extent to which this increased variability will further influence climate change.

  3. Near-infrared sky background fluctuations at mid- and low latitudes

    NASA Astrophysics Data System (ADS)

    Moreels, G.; Clairemidi, J.; Faivre, M.; Pautet, D.; Rubio da Costa, F.; Rousselot, P.; Meriwether, J. W.; Lehmacher, G. A.; Vidal, E.; Chau, J. L.; Monnet, G.

    2008-10-01

    The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700 3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512 × 512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36° × 36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin2 area are monitored during periods of time of several hours. The sky intensity measured in the 754 900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond2. A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5 40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3 6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/ . Enter username: nirsky and password: skynir.

  4. Transport and fluctuations in high temperature spheromak plasmas

    SciTech Connect

    McLean, H.S.; Wood, R.D.; Cohen, B.I.; Hooper, E.B.; Hill, D.N.; Moller, J.M.; Romero-Talamas, C.; Woodruff, S.

    2006-05-15

    Higher electron temperature (T{sub e}>350 eV) and reduced electron thermal diffusivity ({chi}{sub e}<10 m{sup 2}/s) is achieved in the Sustained Spheromak Physics Experiment (SSPX) by increasing the discharge current=I{sub gun} and gun bias flux={psi}{sub gun} in a prescribed manner. The internal current and q=safety factor profile derived from equilibrium reconstruction as well as the measured magnetic fluctuation amplitude can be controlled by programming the ratio {lambda}{sub gun}={mu}{sub 0}I{sub gun}/{psi}{sub gun}. Varying {lambda}{sub gun} above and below the minimum energy eigenvalue={lambda}{sub FC} of the flux conserver ({nabla}xB-vector={lambda}{sub FC}B-vector) varies the q profile and produces the m/n=poloidal/toroidal magnetic fluctuation mode spectrum expected from mode-rational surfaces with q=m/n. The highest T{sub e} is measured when the gun is driven with {lambda}{sub gun} slightly less than {lambda}{sub FC}, producing low fluctuation amplitudes (<1%) and 1/2fluctuations associated with low-order mode-rational surfaces, and the quality of magnetic surfaces.

  5. A Model for Temperature Fluctuations in a Buoyant Plume

    NASA Astrophysics Data System (ADS)

    Bisignano, A.; Devenish, B. J.

    2015-11-01

    We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source that includes the effects of temperature fluctuations. The model is based on that of Webster and Thomson (Atmos Environ 36:5031-5042, 2002) in that it is a coupling of a classical plume model in a crossflow with stochastic differential equations for the vertical velocity and temperature (which are themselves coupled). The novelty lies in the addition of the latter stochastic differential equation. Parametrizations of the plume turbulence are presented that are used as inputs to the model. The root-mean-square temperature is assumed to be proportional to the difference between the centreline temperature of the plume and the ambient temperature. The constant of proportionality is tuned by comparison with equivalent statistics from large-eddy simulations (LES) of buoyant plumes in a uniform crossflow and linear stratification. We compare plume trajectories for a wide range of crossflow velocities and find that the model generally compares well with the equivalent LES results particularly when added mass is included in the model. The exception occurs when the crossflow velocity component becomes very small. Comparison of the scalar concentration, both in terms of the height of the maximum concentration and its vertical spread, shows similar behaviour. The model is extended to allow for realistic profiles of ambient wind and temperature and the results are compared with LES of the plume that emanated from the explosion and fire at the Buncefield oil depot in 2005.

  6. Temperature fluctuation of the Iceland mantle plume through time

    NASA Astrophysics Data System (ADS)

    Spice, Holly E.; Fitton, J. Godfrey; Kirstein, Linda A.

    2016-02-01

    The newly developed Al-in-olivine geothermometer was used to find the olivine-Cr-spinel crystallization temperatures of a suite of picrites spanning the spatial and temporal extent of the North Atlantic Igneous Province (NAIP), which is widely considered to be the result of a deep-seated mantle plume. Our data confirm that start-up plumes are associated with a pulse of anomalously hot mantle over a large spatial area before becoming focused into a narrow upwelling. We find that the thermal anomaly on both sides of the province at Baffin Island/West Greenland and the British Isles at ˜61 Ma across an area ˜2000 km in diameter was uniform, with Al-in-olivine temperatures up to ˜300°C above that of average mid-ocean ridge basalt (MORB) primitive magma. Furthermore, by combining our results with geochemical data and existing geophysical and bathymetric observations, we present compelling evidence for long-term (>107 year) fluctuations in the temperature of the Iceland mantle plume. We show that the plume temperature fell from its initial high value during the start-up phase to a minimum at about 35 Ma, and that the mantle temperature beneath Iceland is currently increasing.

  7. Fluctuations in radiation backgrounds at high redshift and the first stars

    NASA Astrophysics Data System (ADS)

    Holzbauer, Lauren Nicole

    The first stars to light up our universe are as yet unseen, but there have been many attempts to elucidate their properties. The characteristics of these stars (`Population/Pop III' stars) that we do know lie mostly within theory; they formed out of metal-free hydrogen and helium gas contained in dark matter minihalos at redshifts z 20-30. The extent to which Pop III star formation reached into later times is unknown. Current and near future instruments are incapable of resolving individual Pop III stars. Consequently, astronomers must devise creative means with which to indirectly predict and measure and their properties. In this thesis, we will investigate a few of those means. We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos that is necessary for star formation. By using a variation of the `halo model', which describes the spatial distribution and clustering of halos, we can efficiently generate power spectra for these backgrounds. Spatial fluctuations in the LW and (indirectly) the Lyman-alpha BG can tell us about the transition from primordial star formation to a more metal-enriched mode that marks the beginning of the second generation of stars in our Universe. The Near Infrared Background (NIRB) has for some time been considered a potential tool with which to indirectly observe the first stars. Ultraviolet (UV) emission from these stars is redshifted into the NIR band, making the NIRB amenable for hunting Pop III stellar signatures. There have been several measurements of the NIRB and subsequent theoretical studies attempting to explain them in recent years. Though controversial, residual levels of the mean NIRB intensity and anisotropies have been

  8. Temperature fluctuations as a source of brown dwarf variability

    SciTech Connect

    Robinson, Tyler D.; Marley, Mark S.

    2014-04-20

    A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10%-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed variability, it is possible that some of the variations arise from atmospheric temperature fluctuations instead of, or in addition to, clouds. To better understand the role that thermal variability might play we present a case study of brown dwarf variability using a newly developed one-dimensional, time-stepping model of atmospheric thermal structure. We focus on the effects of thermal perturbations, intentionally simplifying the problem through omission of clouds and atmospheric circulation. Model results demonstrate that thermal perturbations occurring deep in the atmosphere (at pressures greater than 10 bar) of a model T-dwarf can be communicated to the upper atmosphere through radiative heating via the windows in near-infrared water opacity. The response time depends on where in the atmosphere a thermal perturbation is introduced. We show that, for certain periodic perturbations, the emission spectrum can have complex time- and wavelength-dependent behaviors, including phase shifts in times of maximum flux observed at different wavelengths. Since different wavelengths probe different levels in the atmosphere, these variations track a wavelength-dependent set of radiative exchanges happening between different atmospheric levels as a perturbation evolves in time. We conclude that thermal—as well as cloud—fluctuations must be considered as possible contributors to the observed brown dwarf variability.

  9. Transport and Fluctuations in High Temperature Spheromak Plasmas

    SciTech Connect

    McLean, H S; Woodruff, S; Wood, R D; Hooper, E B; Hill, D N; Moller, J; Romero-Talamas, C

    2005-10-27

    Globally coherent magnetic fluctuations often observed during the driven phase after spheromak formation in the Sustained Spheromak Physics Experiment (SSPX) can be reduced to small amplitude by programming the magnetic flux = {Psi}{sub gun} and the discharge current = I{sub gun} in the formation gun. Scanning the edge normalized current = {lambda}{sub edge} = {lambda}{sub gun} = {mu}{sub 0}I{sub gun}/{Psi}{sub gun} above and below the minimum energy eigenvalue = {lambda}{sub FC} of the flux conserver provides a variation in the internal q = safety factor profile producing the expected q = m/n = poloidal/toroidal mode spectrum. By driving the edge with the proper {lambda}{sub gun}, the system can be operated with the poloidal/toroidal mode spectrum between the m/n = 1/2 and 2/3 modes producing low magnetic fluctuation amplitudes and high electron temperature = T{sub e} > 350 eV. Transport and confinement parameters calculated using Thomson scattering-measured T{sub e} and N{sub e} profiles coupled with the equilibrium code internal current profiles show a reduction in electron thermal diffusivity as T{sub e} increases. This scaling behavior is more classical-like than Bohm or open field line transport models where thermal diffusivity increases with T{sub e}. Electron diffusivity is calculated to be less than 10 m{sup 2}/s, approaching levels seen in tokamaks.

  10. Observing temperature fluctuations in humans using infrared imaging

    PubMed Central

    Liu, Wei-Min; Meyer, Joseph; Scully, Christopher G.; Elster, Eric; Gorbach, Alexander M.

    2013-01-01

    In this work we demonstrate that functional infrared imaging is capable of detecting low frequency temperature fluctuations in intact human skin and revealing spatial, temporal, spectral, and time-frequency based differences among three tissue classes: microvasculature, large sub-cutaneous veins, and the remaining surrounding tissue of the forearm. We found that large veins have stronger contractility in the range of 0.005-0.06 Hz compared to the other two tissue classes. Wavelet phase coherence and power spectrum correlation analysis show that microvasculature and skin areas without vessels visible by IR have high phase coherence in the lowest three frequency ranges (0.005-0.0095 Hz, 0.0095-0.02 Hz, and 0.02-0.06 Hz), whereas large veins oscillate independently. PMID:23538682

  11. Cosmic Microwave Background Fluctuations from the Kinetic Sunyaev-Zeldovich Effect as a Cosmological Probe

    NASA Astrophysics Data System (ADS)

    Park, Hyunbae; Shapiro, P.; Komatsu, E.

    2012-01-01

    We present a calculation of the kinetic Sunyaev-Zel'dovich (kSZ) effect on of the Comic Microwave Background fluctuation. We focus on the scale at the multipole moment of l = 3000 10000 that is currently being probed by the South Pole Telescope (SPT) and the Atacama Cosmology Telescope. For the post-reionization contribution of the total signal, we use the 3rd order perturbation theory (3PT) to model non-linearity of post-reionization epoch. We evaluate a non-linear expression for momentum powerspectrum in Ma and Fry (2002) with the 3PT density and velocity powerspectrum. And, we use the 3PT momentum powerspectrum to calculate the kSZ signal. We show that the 3PT is a reasonable approximation by comparing our result with previous work by Zhang, Pen and Trac (2004). For reionization contribution, we use our N-body radiative transfer simulations to take patchiness of ionization of intergalactic medium in reionization epoch into account. Using ionized fraction field in the simulation, we calculate the momentum field of the ionized gas. And, we correct for the missing power in finite size boxes of simulations. Finally, we show the kSZ calculation for different simulations with reionization scenarios. With contributions from each epoch, we predict total kSZ signal for different reionization history and put constraint on reionization scenario using an upper bound of the signal from recent SPT measurement.

  12. 21 cm signal from cosmic dawn: imprints of spin temperature fluctuations and peculiar velocities

    NASA Astrophysics Data System (ADS)

    Ghara, Raghunath; Choudhury, T. Roy; Datta, Kanan K.

    2015-02-01

    The 21 cm brightness temperature δTb fluctuations from reionization promise to provide information on the physical processes during that epoch. We present a formalism for generating the δTb distribution using dark matter simulations and a 1D radiative transfer code. Our analysis is able to account for the spin temperature TS fluctuations arising from inhomogeneous X-ray heating and Lyα coupling during cosmic dawn. The δTb power spectrum amplitude at large scales (k ˜ 0.1 Mpc-1) is maximum when ˜10 per cent of the gas (by volume) is heated above the cosmic microwave background temperature. The power spectrum shows a `bump'-like feature during cosmic dawn and its location measures the typical sizes of heated regions. We find that the effect of peculiar velocities on the power spectrum is negligible at large scales for most part of the reionization history. During early stages (when the volume averaged ionization fraction ≲ 0.2) this is because the signal is dominated by fluctuations in TS. For reionization models that are solely driven by stars within high-mass (≳ 109 M⊙) haloes, the peculiar velocity effects are prominent only at smaller scales (k ≳ 0.4 Mpc-1) where patchiness in the neutral hydrogen density dominates the signal. The conclusions are unaffected by changes in the amplitude or steepness in the X-ray spectra of the sources.

  13. Transport and fluctuations in high temperature spheromak plasmas

    NASA Astrophysics Data System (ADS)

    McLean, Harry

    2005-10-01

    A systematic analysis is presented of thermal transport in a driven spheromak that extends well into the collisionless regime and spans a wide range of magnetic fluctuation levels. The relationship between internal fluctuations and energy/helicity transport is of fundamental interest to many self-organized configurations in laboratory and space plasmas and the subject of ongoing multi-institutional collaborations. With the recent achievement on the SSPX spheromak[1] of electron temperature Te˜350eV in the core, and good confinement (core electron thermal diffusivity χe<10m^2/ for Te>200eV), we are now comparing heat transport in the experiment with a variety of models including classical, Bohm, and stochastic[2]/diffusive[3]/open[4] field lines. Using Thomson scattering to measure Te, ne profiles and the CORSICA equilibrium code to calculate internal current profiles from magnetic probe fits, we find that χe decreases as Te increases, a scaling behavior more classical-like than Bohm or open field line models would indicate. Lower Te and higher χe is observed in the transition region between the core and the separatrix where NIMROD 3d resistive MHD calculations[5] show the possible existence of chaotic field lines. We will also discuss plans including multi-pulse Thomson scattering and neutral beam heating. [1] E.B. Hooper, et al., Nucl. Fusion 39, 863 (1999). [2] A.B. Rechester and M.N. Rosenbluth, Phys. Rev. Lett. 40, 38 (1978). [3] J.D. Callen, Phys. Rev. Lett. 94, 055002 (2005). [4] R.W. Moses, et al., Phys. Plasmas 8, 4839 (2001). [5] B.I. Cohen, et al., Phys. Plasmas 12, 056106 (2005). This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  14. Temperature fluctuations driven by magnetorotational instability in protoplanetary disks

    SciTech Connect

    McNally, Colin P.; Hubbard, Alexander; Low, Mordecai-Mark Mac; Yang, Chao-Chin E-mail: ahubbard@amnh.org E-mail: ccyang@astro.lu.se

    2014-08-10

    The magnetorotational instability (MRI) drives magnetized turbulence in sufficiently ionized regions of protoplanetary disks, leading to mass accretion. The dissipation of the potential energy associated with this accretion determines the thermal structure of accreting regions. Until recently, the heating from the turbulence has only been treated in an azimuthally averaged sense, neglecting local fluctuations. However, magnetized turbulence dissipates its energy intermittently in current sheet structures. We study this intermittent energy dissipation using high resolution numerical models including a treatment of radiative thermal diffusion in an optically thick regime. Our models predict that these turbulent current sheets drive order-unity temperature variations even where the MRI is damped strongly by Ohmic resistivity. This implies that the current sheet structures where energy dissipation occurs must be well-resolved to correctly capture the flow structure in numerical models. Higher resolutions are required to resolve energy dissipation than to resolve the magnetic field strength or accretion stresses. The temperature variations are large enough to have major consequences for mineral formation in disks, including melting chondrules, remelting calcium-aluminum-rich inclusions, and annealing silicates; and may drive hysteresis: current sheets in MRI active regions could be significantly more conductive than the remainder of the disk.

  15. The gravitational wave contribution to cosmic microwave background anisotropies and the amplitude of mass fluctuations from COBE results

    NASA Technical Reports Server (NTRS)

    Lucchin, Francesco; Matarrese, Sabino; Mollerach, Silvia

    1992-01-01

    A stochastic background of primordial gravitational waves may substantially contribute, via the Sachs-Wolfe effect, to the large-scale cosmic microwave background (CMB) anisotropies recently detected by COBE. This implies a bias in any resulting determination of the primordial amplitude of density fluctuations. We consider the constraints imposed on n is less than 1 ('tilted') power-law fluctuation spectra, taking into account the contribution from both scalar and tensor waves, as predicted by power-law inflation. The gravitational wave contribution to CMB anisotropies generally reduces the required rms level of mass fluctuation, thereby increasing the linear bias parameter, even in models where the spectral index is close to the Harrison-Zel'dovich value n = 1. This 'gravitational wave bias' helps to reconcile the predictions of CDM models with observations on pairwise galaxy velocity dispersion on small scales.

  16. Correlation Ece Measurements of Turbulent Electron Temperature Fluctuations in Diii-D

    NASA Astrophysics Data System (ADS)

    White, A. E.; Peebles, W. A.; Rhodes, T. L.; Wang, G.; Schmitz, L.; Carter, T. A.; Hillesheim, J. C.; Doyle, E. J.; Zeng, L.; Holland, C. H.; McKee, G. R.; Staebler, G. M.; Waltz, R. E.; Candy, J.; Deboo, J. C.; Petty, C. C.; Burrell, K. H.

    2011-02-01

    This paper describes measurements of long wavelength, turbulent electron temperature fluctuations in the core plasma of the DIII-D tokamak made with a correlation electron cyclotron emission (CECE) radiometer-based diagnostic. Experimental and simulation results indicate that long wavelength electron temperature fluctuations (1) are similar in amplitude and spectrum to density fluctuations, (2) can be associated with both ITG and TEM turbulence, (3) exhibit changes in the relative fluctuation level that correlate with changes in electron thermal transport, and (4) are correlated, but out of phase, with density fluctuations measured simultaneously with reflectometry.

  17. AKARI OBSERVATION OF THE FLUCTUATION OF THE NEAR-INFRARED BACKGROUND

    SciTech Connect

    Matsumoto, T.; Seo, H. J.; Lee, H. M.; Jeong, W.-S.; Pyo, J.; Matsuura, S.; Matsuhara, H.; Oyabu, S.; Wada, T.

    2011-12-01

    We report a search for fluctuations of the sky brightness toward the north ecliptic pole with the Japanese infrared astronomical satellite AKARI, at 2.4, 3.2, and 4.1 {mu}m. We obtained circular maps with 10' diameter fields of view, which clearly show a spatial structure on the scale of a few hundred arcseconds. A power spectrum analysis shows that there is a significant excess fluctuation at angular scales larger than 100'' that cannot be explained by zodiacal light, diffuse Galactic light, shot noise of faint galaxies, or clustering of low-redshift galaxies. These results are consistent with observations at 3.6 and 4.5 {mu}m by NASA's Spitzer Space Telescope. The fluctuating component observed at large angular scales has a blue stellar spectrum which is similar to that of the spectrum of the excess isotropic emission observed with the Infrared Telescope in Space. A significant spatial correlation between wavelength bands was found, and the slopes of the linear correlations are consistent with the spectrum of the excess fluctuation. These findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i.e., Population III stars. The observed fluctuation provides an important constraint on the era of the first stars.

  18. Effects of gas temperature fluctuations on the evolution of Nitrogenous species during coal devolatilization

    SciTech Connect

    Zhang, H.T.; Zhang, J.

    2009-02-15

    The effects of gas temperature fluctuations on the instantaneous evolution processes of nitrogenous species were investigated for pulverized coal particles undergoing devolatilization in a hot gas. The instantaneous mass variations of nitrogenous species released from the particles with diameters of 10-50 {mu} m were computed for different conditions. The instantaneous gas temperature was varied with time either in a simple harmonic way or in a random way. The calculated results showed that, under different time-average gas temperatures, the HCN evolution behaviors of particles with different diameters were all affected by the gas temperature fluctuations. The gas temperature fluctuations led to more rapid HCN release from the pulverized coal particles compared to the results obtained without gas temperature fluctuations. The effects were further enhanced by increasing the amplitude or intensity of the gas temperature fluctuations.

  19. New Measurements of the Cosmic Infrared Background Fluctuations in Deep SpitzerllRAC Survey Data and their Cosmological Implications

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.; Arendt, R. G.; Ashby, M. L. N.; Fazio, G. G.; Mather, J.; Moseley, S. H.

    2012-01-01

    We extend the previous measurements of CIB fluctuations to angular scales of less than or equal to 1 degree new data obtained in the course of the 2,000+ hour Spitzer Extended Deep Survey. Two fields with completed observations of approximately equal to 12 hr/pixel are analyzed for source-subtracted CIB fluctuations at 3.6 and 4.5 micrometers. The fields, EGS and UDS, cover a total area of approximately 0.25 deg and lie at high Galactic and Ecliptic latitudes, thus minimizing cirrus and zodiacal light contributions to the fluctuations. The observations have been conducted at 3 distinct epochs separated by about 6 months. As in our previous studies, the fields were assembled using the self-calibration method which is uniquely suitable for probing faint diffuse backgrounds. The assembled fields were cleaned off the bright sources down to the low shot noise levels corresponding to AB mag approximately equal to 25, Fourier-transformed and their power spectra evaluated. The noise was estimated from the time-differenced data and subtracted from the signal isolating the fluctuations remaining above the noise levels. The power spectra of the source-subtracted fields remain identical (within the observational uncertainties) for the three epochs of observations indicating that zodiacal light contributes negligibly to the fluctuations. By comparing to the measurements for the same regions at 8 micrometers we demonstrate that Galactic cirrus cannot account for the levels of the fluctuations either. The signal appears isotropically distributed on the sky as required by its origin in the CIB fluctuations. This measurement thus extends our earlier results to the important range of sub-degree scales. We find that the CIB fluctuations continue to diverge to more than 10 times those of known galaxy populations on angular scales out to less than or equal to 1 degree. The low shot noise levels remaining in the diffuse maps indicate that the large scale fluctuations arise from spatial

  20. RECONSTRUCTING THE NEAR-INFRARED BACKGROUND FLUCTUATIONS FROM KNOWN GALAXY POPULATIONS USING MULTIBAND MEASUREMENTS OF LUMINOSITY FUNCTIONS

    SciTech Connect

    Helgason, Kari; Ricotti, Massimo; Kashlinsky, Alexander

    2012-06-20

    We model fluctuations in the cosmic infrared background (CIB) arising from known galaxy populations using 233 measured UV, optical, and near-IR luminosity functions (LFs) from a variety of surveys spanning a wide range of redshifts. We compare best-fit Schechter parameters across the literature and find clear indication of evolution with redshift. Providing fitting formulae for the multi-band evolution of the LFs out to z {approx} 5, we calculate the total emission redshifted into the near-IR bands in the observer frame and recover the observed optical and near-IR galaxy counts to good accuracy. Our empirical approach, in conjunction with a halo model describing the clustering of galaxies, allows us to compute the fluctuations of the unresolved CIB and compare the models to current measurements. We find that fluctuations from known galaxy populations are unable to account for the large-scale CIB clustering signal seen by Spitzer/IRAC and AKARI/IRC and continue to diverge out to larger angular scales. This holds true even if the LFs are extrapolated out to faint magnitudes with a steep faint-end slope all the way to z = 8. We also show that removing resolved sources to progressively fainter magnitude limits isolates CIB fluctuations to increasingly higher redshifts. Our empirical approach suggests that known galaxy populations are not responsible for the bulk of the fluctuation signal seen in the measurements and favors a very faint population of highly clustered sources.

  1. Reduction of thermal emission background in high temperature microheaters

    NASA Astrophysics Data System (ADS)

    Armstrong, Philip R.; Mah, Merlin L.; Olson, Kyle D.; Taylor, Lucas N.; Talghader, Joseph J.

    2016-05-01

    High temperature microheaters have been designed and constructed to reduce the background thermal emission radiation produced by the heater. Such heaters allow one to probe luminescence with very low numbers of photons where the background emission would overwhelm the desired signal. Two methods to reduce background emission are described: one with low emission materials and the other with interference coating design. The first uses platforms composed of material that is transparent to mid-infrared light and therefore of low emissivity. Heating elements are embedded in the periphery of the heater. The transparent platform is composed of aluminum oxide, which is largely transparent for wavelengths less than about 8 μm. In the luminescent microscopy used to test the heater, an optical aperture blocks emission from the heating coils while passing light from the heated objects on the transparent center of the microheater. The amount of infrared light transmitted through the aperture was reduced by 90% as the aperture was moved from the highly emissive heater coils at 450 °C to the largely transparent center at the same temperature. The second method uses microheaters with integrated multilayer interference structures designed to limit background emission in the spectral range of the low-light luminescence object being measured. These heaters were composed of aluminum oxide, titanium dioxide, and platinum and were operated over a large range of temperatures, from 50 °C to 600 °C. At 600 °C, they showed a background photon emission only 1/800 that of a comparison heater without the multilayer interference structure. In this structure, the radiation background was sufficiently reduced to easily monitor weak thermoluminescent emission from CaSO4:Ce,Tb microparticles.

  2. Low-background temperature sensors fabricated on parylene substrates

    NASA Astrophysics Data System (ADS)

    Dhar, A.; Loach, J. C.; Barton, P. J.; Larsen, J. T.; Poon, A. W. P.

    2015-12-01

    Temperature sensors fabricated from ultra-low radioactivity materials have been developed for low-background experiments searching for neutrinoless double-beta decay and the interactions of WIMP dark matter. The sensors consist of electrical traces photolithographically-patterned onto substrates of vapor-deposited parylene. They are demonstrated to function as expected, to do so reliably and robustly, and to be highly radio-pure. This work is a proof-of-concept study of a technology that can be applied to broad class of electronic circuits used in low-background experiments.

  3. Impact of porous medium on the high cycle temperature fluctuations in a mixing tee

    SciTech Connect

    Bu, L.; Zhao, J.

    2012-07-01

    Temperature fluctuations occur in the region where hot and cold fluids mix turbulently in the nuclear power plants. Temperature fluctuations cause thermal fatigue of piping systems. In the design of generation IV nuclear power plants, supercritical fluids are supposed to be used widely. This paper investigated the thermal striping phenomenon caused by the turbulent mixing in a supercritical water Tee. There are two key issues in the study of thermal striping phenomenon: One is to find the region which experiences the peak temperature fluctuation; the other is how to attenuate it. Porous media was used to attenuate the temperature fluctuations in this paper. The results show that porous media with proper parameters in a tee can reduce the temperature fluctuations magnificently. (authors)

  4. Prominence oscillations: Effect of a time-dependent background temperature

    NASA Astrophysics Data System (ADS)

    Ballester, J. L.; Carbonell, M.; Soler, R.; Terradas, J.

    2016-06-01

    Context. Small amplitude oscillations in prominences have been known about for a long time, and from a theoretical point of view, these oscillations have been interpreted in terms of standing or propagating linear magnetohydrodynamic (MHD) waves. In general, these oscillations were studied by producing small perturbations in a background equilibrium with stationary physical properties. Aims: Taking into account that prominences are dynamic plasma structures, the assumption of a stationary equilibrium is not realistic. Therefore, our main aim is to study the effects produced by a non-stationary background on slow MHD waves, which could be responsible for prominence oscillations. Methods: Assuming that the radiation term is proportional to temperature and constant external heating, we have derived an expression for the temporal variation of the background temperature, which depends on the imbalance between heating and cooling processes. Furthermore, radiative losses, together with parallel thermal conduction, have also been included as damping mechanisms for the waves. Results: As temperature increases with time, the period of slow waves decreases and the amplitude of the velocity perturbations is damped. The inclusion of radiative losses enhances the damping. As temperature decreases with time, the period of slow waves increases and the amplitude of velocity perturbations grows while, as expected, the inclusion of radiative losses contributes to the damping of oscillations. Conclusions: There is observational evidence that, in different locations of the same prominence, oscillations are damped or amplified with time. This temporal damping or amplification can be obtained by a proper combination of a variable background temperature, together with radiative damping. Furthermore, decayless oscillations can also be obtained with an appropriate choice of the characteristic radiation time.

  5. Dipole modulation of cosmic microwave background temperature and polarization

    NASA Astrophysics Data System (ADS)

    Ghosh, Shamik; Kothari, Rahul; Jain, Pankaj; Rath, Pranati K.

    2016-01-01

    We propose a dipole modulation model for the Cosmic Microwave Background Radiation (CMBR) polarization field. We show that the model leads to correlations between l and l+1 multipoles, exactly as in the case of temperature. We obtain results for the case of TE, EE and BB correlations. An anisotropic or inhomogeneous model of primordial power spectrum which leads to such correlations in temperature field also predicts similar correlations in CMBR polarization. We analyze the CMBR temperature and polarization data in order to extract the signal of these correlation between l and l+1 multipoles. Our results for the case of temperature using the latest PLANCK data agree with those obtained by an earlier analysis. A detailed study of the correlation in the polarization data is not possible at present. Hence we restrict ourselves to a preliminary investigation in this case.

  6. Fluctuation-induced heat release from temperature-quenched nuclear spins near a quantum critical point.

    PubMed

    Kim, Y H; Kaur, N; Atkins, B M; Dalal, N S; Takano, Y

    2009-12-11

    At a quantum critical point (QCP)--a zero-temperature singularity in which a line of continuous phase transition terminates--quantum fluctuations diverge in space and time, leading to exotic phenomena that can be observed at nonzero temperatures. Using a quantum antiferromagnet, we present calorimetric evidence that nuclear spins frozen in a high-temperature nonequilibrium state by temperature quenching are annealed by quantum fluctuations near the QCP. This phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, serves as an excellent marker of a quantum critical region around the QCP and provides a probe of the dynamics of the divergent quantum fluctuations. PMID:20366226

  7. Temperature dependence of vibrational frequency fluctuation of N3- in D2O

    NASA Astrophysics Data System (ADS)

    Tayama, Jumpei; Ishihara, Akane; Banno, Motohiro; Ohta, Kaoru; Saito, Shinji; Tominaga, Keisuke

    2010-07-01

    We have studied the temperature dependence of the vibrational frequency fluctuation of the antisymmetric stretching mode of N3- in D2O by three-pulse infrared (IR) photon echo experiments. IR pump-probe measurements were also carried out to investigate the population relaxation and the orientational relaxation of the same band. It was found that the time-correlation function (TCF) of the frequency fluctuation of this mode is well described by a biexponential function with a quasistatic term. The faster decay component has a time constant of about 0.1 ps, and the slower component varies from 1.4 to 1.1 ps in the temperature range from 283 to 353 K. This result indicates that liquid dynamics related to the frequency fluctuation are not highly sensitive to temperature. We discuss the relationship between the temperature dependence of the vibrational frequency fluctuation and that of the molecular motion of the system to investigate the molecular origin of the frequency fluctuation of the solute. We compare the temperature dependence of the frequency fluctuation with that of other dynamics such as dielectric relaxation of water. In contrast to the Debye dielectric relaxation time of D2O, the two time constants of the TCF of the frequency fluctuation do not exhibit strong temperature dependence. We propose a simple theoretical model for the frequency fluctuation in solutions based on perturbation theory and the dipole-dipole interaction between the vibrational mode of the solute and the solvent molecules. This model suggests that the neighboring solvent molecules in the vicinity of the solute play an important role in the frequency fluctuation. We suggest that the picosecond component of the frequency fluctuation results from structural fluctuation of the hydrogen-bonding network in water.

  8. Anderson localization in high temperature QCD: background configuration properties and Dirac eigenmodes

    NASA Astrophysics Data System (ADS)

    Cossu, Guido; Hashimoto, Shoji

    2016-06-01

    We investigate the properties of the background gauge field configurations that act as disorder for the Anderson localization mechanism in the Dirac spectrum of QCD at high temperatures. We compute the eigenmodes of the Möbius domain-wall fermion operator on configurations generated for the SU(3) gauge theory with two flavors of fermions, in the temperature range [0.9, 1.9]T c . We identify the source of localization of the eigenmodes with gauge configurations that are self-dual and support negative fluctuations of the Polyakov loop P L , in the high temperature sea of P L ˜ 1. The dependence of these observations on the boundary conditions of the valence operator is studied. We also investigate the spatial overlap of the left-handed and right-handed projected eigenmodes in correlation with the localization and the corresponding eigenvalue. We discuss an interpretation of the results in terms of monopole-instanton structures.

  9. Magnetic-Fluctuation-Induced Particle Transport and Density Relaxation in a High-Temperature Plasma

    SciTech Connect

    Ding, W. X.; Brower, D. L.; Fiksel, G.; Den Hartog, D. J.; Prager, S. C.; Sarff, J. S.

    2009-07-10

    The first direct measurement of magnetic-fluctuation-induced particle flux in the core of a high-temperature plasma is reported. Transport occurs due to magnetic field fluctuations associated with global tearing instabilities. The electron particle flux, resulting from the correlated product of electron density and radial magnetic fluctuations, accounts for density profile relaxation during a magnetic reconnection event. The measured particle transport is much larger than that expected for ambipolar particle diffusion in a stochastic magnetic field.

  10. Thermal fluctuations affect the transcriptome through mechanisms independent of average temperature.

    PubMed

    Sørensen, Jesper Givskov; Schou, Mads Fristrup; Kristensen, Torsten Nygaard; Loeschcke, Volker

    2016-01-01

    Terrestrial ectotherms are challenged by variation in both mean and variance of temperature. Phenotypic plasticity (thermal acclimation) might mitigate adverse effects, however, we lack a fundamental understanding of the molecular mechanisms of thermal acclimation and how they are affected by fluctuating temperature. Here we investigated the effect of thermal acclimation in Drosophila melanogaster on critical thermal maxima (CTmax) and associated global gene expression profiles as induced by two constant and two ecologically relevant (non-stressful) diurnally fluctuating temperature regimes. Both mean and fluctuation of temperature contributed to thermal acclimation and affected the transcriptome. The transcriptomic response to mean temperatures comprised modification of a major part of the transcriptome, while the response to fluctuations affected a much smaller set of genes, which was highly independent of both the response to a change in mean temperature and to the classic heat shock response. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to contribute to our understanding of thermal adaptation. We provide evidence that environmental sensing, particularly phototransduction, is a central mechanism underlying the regulation of thermal acclimation to fluctuating temperatures. Thus, genes and pathways involved in phototransduction are likely of importance in fluctuating climates. PMID:27487917

  11. Thermal fluctuations affect the transcriptome through mechanisms independent of average temperature

    PubMed Central

    Sørensen, Jesper Givskov; Schou, Mads Fristrup; Kristensen, Torsten Nygaard; Loeschcke, Volker

    2016-01-01

    Terrestrial ectotherms are challenged by variation in both mean and variance of temperature. Phenotypic plasticity (thermal acclimation) might mitigate adverse effects, however, we lack a fundamental understanding of the molecular mechanisms of thermal acclimation and how they are affected by fluctuating temperature. Here we investigated the effect of thermal acclimation in Drosophila melanogaster on critical thermal maxima (CTmax) and associated global gene expression profiles as induced by two constant and two ecologically relevant (non-stressful) diurnally fluctuating temperature regimes. Both mean and fluctuation of temperature contributed to thermal acclimation and affected the transcriptome. The transcriptomic response to mean temperatures comprised modification of a major part of the transcriptome, while the response to fluctuations affected a much smaller set of genes, which was highly independent of both the response to a change in mean temperature and to the classic heat shock response. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to contribute to our understanding of thermal adaptation. We provide evidence that environmental sensing, particularly phototransduction, is a central mechanism underlying the regulation of thermal acclimation to fluctuating temperatures. Thus, genes and pathways involved in phototransduction are likely of importance in fluctuating climates. PMID:27487917

  12. Measurement of Yields and Fluctuations using Background and Calibration Data from the LUX Detector

    NASA Astrophysics Data System (ADS)

    Pease, Evan; LUX Collaboration

    2016-03-01

    The Large Underground Xenon (LUX) detector is a 350-kg liquid xenon (LXe) time-projection chamber designed for the direct detection of weakly-interacting massive particles (WIMPs), a leading dark matter candidate. LUX operates on the 4850-foot level of the Sanford Underground Research Facility in Lead, SD. Monoenergetic electronic recoil (ER) peaks in the WIMP search and calibration data from the first underground science run of the LUX detector have been used to measure ER light and charge yields in LXe between 5.2 keV and 662 keV. The energy resolution of the LUX detector at these energies will also be presented. Recombination fluctuations are observed to follow a linear dependence on the number of ions for the energies in this study, and this dependence is consistent with low-energy measurements made with a tritium beta source in the LUX detector. Using these results and additional measurements of the recoil bands from tritium and D-D neutron calibrations, I will compare recombination fluctuations in LXe response to electronic and nuclear recoils. The presenter is supported by the U.S. Department of Energy, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract DE-AC05-06OR23100.

  13. Effect of Contraction on Turbulence and Temperature Fluctuations Generated by a Warm Grid

    NASA Technical Reports Server (NTRS)

    Mills, Robert R., Jr.; Corrsin, Stanley

    1959-01-01

    Hot-wire anemometer measurements were made of several statistical properties of approximately homogeneous and isotropic fields of turbulence and temperature fluctuations generated by a warm grid in a uniform airstream sent through a 4-to-1 contraction. These measurements were made both in the contraction and in the axisymmetric domain farther downstream. In addition to confirming the well-known turbulence anisotropy induced by strain, the data show effects on the skewnesses of both longitudinal velocity fluctuation (which has zero skewness in isotropic turbulence) and its derivative. The concomitant anisotropy in the temperature field accelerates the decay of temperature fluctuations.

  14. Quantum Fluctuations of Mesoscopic Damped Circuit Involving Capacitance-Inductance Coupling at a Finite Temperature

    NASA Astrophysics Data System (ADS)

    Xu, Xing-Lei; Xu, Shi-Min; Li, Hong-Qi

    2008-06-01

    The quantization of mesoscopic damped circuit involving capacitance-inductance coupling is proposed by the method of thrice linear transformation and damped harmonic oscillator quantization. The quantum fluctuations of the charges and current of each loop are calculated by thermo-field dynamics (TFD) in thermal vacuum state, thermal coherent state and thermal squeezed state, respectively. It is shown that the quantum fluctuations of the charges and current not only depend on circuit inherent parameter and coupled magnitude, but also rely on squeezed coefficients, squeezed angle, environmental temperature and damped resistance. And, because of influence of environmental temperature and damped resistance, the quantum fluctuations increase with increasing temperature and decrease with prolonging time.

  15. Effect of Fluctuations of Temperature During Frozen Storage on Denaturation of Fish Myofibrillar Protein

    NASA Astrophysics Data System (ADS)

    Fukuda, Yutaka; Okazaki, Emiko; Wada, Ritsuko

    The fluctuation in frozen storage temperature was set up by moving the minced meat from chub mackerel reversibly from the room of lower temperature to that of higher temperature for 7 hours every day during 180 days. The freeze denaturation of myofibrillar protein was studied in term the first-order rate (KD) of inactivation of myofibrillar Ca-ATPase. The freeze denaturation rate constant of the myofibrillar protein fluctuated between two different temperatures was same as or higher than the KD in case of constant temperature in higher temperature side.

  16. Skewness in CMB temperature fluctuations from curved cosmic (super-)strings

    SciTech Connect

    Yamauchi, Daisuke; Sendouda, Yuuiti; Yoo, Chul-Moon; Naruko, Atsushi; Sasaki, Misao; Takahashi, Keitaro E-mail: sendouda@yukawa.kyoto-u.ac.jp E-mail: keitaro@a.phys.nagoya-u.ac.jp E-mail: misao@yukawa.kyoto-u.ac.jp

    2010-05-01

    We compute the one-point probability distribution function of small-angle cosmic microwave background temperature fluctuations due to curved cosmic (super-)strings with a simple model of string network by performing Monte Carlo simulations. Taking into account of the correlation between the curvature and the velocity of string segments, there appear non-Gaussian features, specifically non-Gaussian tails and a skewness, in the one-point pdf. The obtained sample skewness for the conventional field-theoretic cosmic strings is g{sub 1} ≈ −0.14, which is consistent with the result reported by Fraisse et al. We also discuss the dependence of the pdf on the intercommuting probability. We find that the standard deviation of the Gaussian part increases and non-Gaussian features are suppressed as the intercommuting probability decreases. For sufficiently small intercommuting probability, the skewness is given by ∼< (a few) × 10{sup −2}.

  17. Quantum Dynamics in Noisy Backgrounds: from Sampling to Dissipation and Fluctuations

    NASA Astrophysics Data System (ADS)

    Oliveira, O.; Paula, W. de; Frederico, T.; Hussein, M. S.

    2016-08-01

    We investigate the dynamics of a quantum system coupled linearly to Gaussian white noise using functional methods. By performing the integration over the noisy field in the evolution operator, we get an equivalent non-Hermitian Hamiltonian, which evolves the quantum state with a dissipative dynamics. We also show that if the integration over the noisy field is done for the time evolution of the density matrix, a gain contribution from the fluctuations can be accessed in addition to the loss one from the non-hermitian Hamiltonian dynamics. We illustrate our study by computing analytically the effective non-Hermitian Hamiltonian, which we found to be the complex frequency harmonic oscillator, with a known evolution operator. It leads to space and time localisation, a common feature of noisy quantum systems in general applications.

  18. Introduction to temperature anisotropies of Cosmic Microwave Background radiation

    NASA Astrophysics Data System (ADS)

    Sugiyama, Naoshi

    2014-06-01

    Since its serendipitous discovery, Cosmic Microwave Background (CMB) radiation has been recognized as the most important probe of Big Bang cosmology. This review focuses on temperature anisotropies of CMB which make it possible to establish precision cosmology. Following a brief history of CMB research, the physical processes working on the evolution of CMB anisotropies are discussed, including gravitational redshift, acoustic oscillations, and diffusion dumping. Accordingly, dependencies of the angular power spectrum on various cosmological parameters, such as the baryon density, the matter density, space curvature of the universe, and so on, are examined and intuitive explanations of these dependencies are given.

  19. REGULATION OF ISOPRENE EMISSION RESPONSES TO RAPID LEAF TEMPERATURE FLUCTUATIONS

    EPA Science Inventory

    Isoprene emission from leaves is temperature dependent and may protect them from damage at high temperatures. We measured the temperature of white oak (Quercus alba L.) leaves at the top of the canopy. The largest changes in leaf temperature were associated with changes in solar ...

  20. Age specific fecundity of Lygus hesperus in high, fluctuating temperatures.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have simulated hourly temperatures to examine Lygus response to hot summers in the San Joaquin Valley. Constant temperature of 33C quickly killed Lygus and SJV temperatures routinely surpass this level. Average hourly temperatures were tested for the months May, July, and September. Age specific ...

  1. Systematic measurement of fast neutron background fluctuations in an urban area using a mobile detection system

    NASA Astrophysics Data System (ADS)

    Iyengar, A.; Beach, M.; Newby, R. J.; Fabris, L.; Heilbronn, L. H.; Hayward, J. P.

    2015-02-01

    Neutron background measurements using a mobile trailer-based system were conducted in Knoxville, Tennessee, USA. The 0.5 m2 system, consisting of eight EJ-301 liquid scintillation detectors, was used to collect neutron background measurements in order to better understand the systematic variations in background that depend solely on the street-level measurement position in a downtown area. Data was collected along 5 different streets, and the measurements were found to be repeatable. Using 10-min measurements, the fractional uncertainty in each measured data point was <2%. Compared with fast neutron background count rates measured away from downtown Knoxville, a reduction in background count rates ranging from 10% to 50% was observed in the downtown area, sometimes varying substantially over distances of tens of meters. These reductions are attributed to the net shielding of the cosmic ray neutron flux by adjacent buildings. For reference, the building structure as observed at street level is quantified in part here by a measured angle-of-open-sky metric.

  2. Systematic measurement of fast neutron background fluctuations in an urban area using a mobile detection system

    DOE PAGESBeta

    Iyengar, Anagha; Beach, Matthew; Newby, Robert J.; Fabris, Lorenzo; Heilbronn, Lawrence H.; Hayward, Jason P.

    2015-11-12

    Neutron background measurements using a mobile trailer-based system were conducted in Knoxville, Tennessee. The 0.5 m2 system consisting of 8 EJ-301 liquid scintillation detectors was used to collect neutron background measurements in order to better understand the systematic background variations that depend solely on the street-level measurement position in a local, downtown area. Data was collected along 5 different streets in the downtown Knoxville area, and the measurements were found to be repeatable. Using 10-min measurements, fractional uncertainty in each measured data point was <2%. Compared with fast neutron background count rates measured away from downtown Knoxville, a reduction inmore » background count rates ranging from 10-50% was observed in the downtown area, sometimes varying substantially over distances of tens of meters. These reductions are attributed to the shielding of adjacent buildings, quantified in part here by the metric angle-of-open-sky. The adjacent buildings may serve to shield cosmic ray neutron flux.« less

  3. Systematic measurement of fast neutron background fluctuations in an urban area using a mobile detection system

    SciTech Connect

    Iyengar, Anagha; Beach, Matthew; Newby, Robert J.; Fabris, Lorenzo; Heilbronn, Lawrence H.; Hayward, Jason P.

    2015-11-12

    Neutron background measurements using a mobile trailer-based system were conducted in Knoxville, Tennessee. The 0.5 m2 system consisting of 8 EJ-301 liquid scintillation detectors was used to collect neutron background measurements in order to better understand the systematic background variations that depend solely on the street-level measurement position in a local, downtown area. Data was collected along 5 different streets in the downtown Knoxville area, and the measurements were found to be repeatable. Using 10-min measurements, fractional uncertainty in each measured data point was <2%. Compared with fast neutron background count rates measured away from downtown Knoxville, a reduction in background count rates ranging from 10-50% was observed in the downtown area, sometimes varying substantially over distances of tens of meters. These reductions are attributed to the shielding of adjacent buildings, quantified in part here by the metric angle-of-open-sky. The adjacent buildings may serve to shield cosmic ray neutron flux.

  4. Experimental study of electron temperature fluctuations in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    White, Anne Elisabeth

    The study of anomalous transport caused by turbulence in plasmas is an important aspect of magnetic fusion energy research. The importance of long-wavelength, electron temperature fluctuations in determining electron heat transport remains an open question. In this work, experiments were carried out to investigate the transport relevance of electron temperature fluctuations at the DIII-D tokamak using a radiometer-based, Correlation Electron Cyclotron Emission (CECE) diagnostic. The measurements of electron temperature fluctuations at DIII-D have provided the unique opportunity to quantitatively compare simultaneously measured electron temperature and density fluctuations with predictions from nonlinear gyrokinetic simulations. Experimentally, it is observed that the profiles of the two fields are similar in amplitude and spectrum in neutral beam-heated, low-confinement mode (L-mode) plasmas where the Ion Temperature Gradient (ITG) mode is expected to be the dominant linear instability. It is also observed that electron temperature fluctuations in the core plasma are reduced in high-confinement mode (H-mode), correlated with improved confinement. When Electron Cyclotron Heating (ECH) is used to modify profiles in neutral beam-heated L-mode plasmas, it is observed that the ratio of electron temperature and density fluctuation amplitudes increases, while theory predicts that the changes in the profiles will result in an increase in the Trapped Electron Mode (TEM) drive. The simultaneously measured profiles of electron temperature and density fluctuations in neutral beam-heated L-mode plasmas are compared with predictions from local, nonlinear gyrokinetic simulations using the GYRO code. The GYRO predictions are in good agreement with experimental observations of transport levels and fluctuation levels at one core location. GYRO predicts that electron temperature fluctuations are out of phase with potential fluctuations (non-Boltzmann response) and will contribute

  5. Fluctuating temperature leads to evolution of thermal generalism and preadaptation to novel environments.

    PubMed

    Ketola, Tarmo; Mikonranta, Lauri; Zhang, Ji; Saarinen, Kati; Ormälä, Anni-Maria; Friman, Ville-Petri; Mappes, Johanna; Laakso, Jouni

    2013-10-01

    Environmental fluctuations can select for generalism, which is also hypothesized to increase organisms' ability to invade novel environments. Here, we show that across a range of temperatures, opportunistic bacterial pathogen Serratia marcescens that evolved in fluctuating temperature (daily variation between 24°C and 38°C, mean 31°C) outperforms the strains that evolved in constant temperature (31°C). The growth advantage was also evident in novel environments in the presence of parasitic viruses and predatory protozoans, but less clear in the presence of stressful chemicals. Adaptation to fluctuating temperature also led to reduced virulence in Drosophila melanogaster host, which suggests that generalism can still be costly in terms of reduced fitness in other ecological contexts. While supporting the hypothesis that evolution of generalism is coupled with tolerance to several novel environments, our results also suggest that thermal fluctuations driven by the climate change could affect both species' invasiveness and virulence. PMID:24094344

  6. Test for anisotropy in the mean of the CMB temperature fluctuation in spherical harmonic space

    NASA Astrophysics Data System (ADS)

    Kashino, Daichi; Ichiki, Kiyotomo; Takeuchi, Tsutomu T.

    2012-03-01

    The standard models of inflation predict statistically homogeneous and isotropic primordial fluctuations, which should be tested by observations. In this paper we illustrate a method to test the statistical isotropy of the mean of the cosmic microwave background temperature fluctuations in the spherical harmonic space and apply the method to the Wilkinson Microwave Anisotropy Probe seven-year observation data. A classical method to test a mean, like the simple Student’s t test, is not appropriate for this purpose because the Wilkinson Microwave Anisotropy Probe data contain anisotropic instrumental noise and suffer from the effect of the mask for the foreground emissions which breaks the statistical independence. Here we perform a band-power analysis with Monte Carlo simulations in which we take into account the anisotropic noise and the mask. We find evidence of a nonzero mean at 99.93% confidence level in a particular range of multipoles. The evidence against the zero-mean assumption as a whole is still significant at the 99% confidence level even if the fact is taken into account that we have tested multiple ranges.

  7. Phase speed saturation of Farley-Buneman waves due to stochastic, self-induced fluctuations in the background flow

    NASA Astrophysics Data System (ADS)

    Rojas, E. L.; Young, M. A.; Hysell, D. L.

    2016-06-01

    The phase speed saturation of Farley-Buneman waves is studied as an interaction with the random turbulent fluctuations in the background. We used the formalism of stochastic differential equations to model the complex interactions with a linearized system plus a stochastic term. Applying an averaging technique, we can obtain an augmented linear system that depends on the random behavior of the waves. The results show that following this approach we can obtain phase velocities that saturate close to the ion acoustic speed (Cs). This approach seems promising for the study of the influence of plasma turbulence generated by different kinds of instabilities on the mean state of the ionosphere.

  8. Small-Scale Spatial Fluctuations in the Soft X-Ray Background. Degree awarded by Maryland Univ., 2000

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; White, Nicolas E. (Technical Monitor)

    2001-01-01

    In order to isolate the diffuse extragalactic component of the soft X-ray background, we have used a combination of ROSAT All-Sky Survey and IRAS 100 micron data to separate the soft X-ray background into five components. We find a Local Hot Bubble similar to that described by Snowden et al (1998). We make a first calculation of the contribution by unresolved Galactic stars to the diffuse background. We constrain the normalization of the Extragalactic Power Law (the contribution of the unresolved extragalactic point sources such as AGN, QSO'S, and normal galaxies) to 9.5 +/- 0.9 keV/(sq cm s sr keV), assuming a power-law index of 1.46. We show that the remaining emission, which is some combination of Galactic halo emission and the putative diffuse extragalactic emission, must be composed of at least two components which we have characterized by thermal spectra. The softer component has log T - 6.08 and a patchy distribution; thus it is most probably part of the Galactic halo. The harder component has log T - 6.46 and is nearly isotropic; some portion may be due to the Galactic halo and some portion may be due to the diffuse extragalactic emission. The maximum upper limit to the strength of the emission by the diffuse extragalactic component is the total of the hard component, approx. 7.4 +/- 1.0 keV/(sq cm s sr keV) in the 3/4 keV band. We have made the first direct measure of the fluctuations due to the diffuse extragalactic emission in the 3/4 keV band. Physical arguments suggest that small angular scale (approx. 10') fluctuations in the Local Hot Bubble or the Galactic halo will have very short dissipation times (about 10(exp 5) years). Therefore, the fluctuation spectrum of the soft X-ray background should measure the distribution of the diffuse extragalactic emission. Using mosaics of deep, overlapping PSPC pointings, we find an autocorrelation function value of approx. 0.0025 for 10' < theta < 20', and a value consistent with zero on larger scales

  9. Daily Temperature Fluctuations Alter Interactions between Closely Related Species of Marine Nematodes.

    PubMed

    De Meester, Nele; Dos Santos, Giovanni A P; Rigaux, Annelien; Valdes, Yirina; Derycke, Sofie; Moens, Tom

    2015-01-01

    In addition to an increase in mean temperature, climate change models predict decreasing amplitudes of daily temperature fluctuations. In temperate regions, where daily and seasonal fluctuations are prominent, such decreases in daily temperature fluctuations can have a pronounced effect on the fitness of species and on the outcome of species interactions. In this study, the effect of a temperature regime with daily fluctuations versus a constant temperature on the fitness and interspecific interactions of three cryptic species of the marine nematode species complex of Litoditis marina (Pm I, Pm III and Pm IV) were investigated. In a lab experiment, different combinations of species (monospecific treatment: Pm I and Pm IV and Pm III alone; two-species treatment: Pm I + Pm IV; three-species treatment: Pm I + Pm IV + Pm III) were subjected to two different temperature regimes: one constant and one fluctuating temperature. Our results showed that fluctuating temperature had minor or no effects on the population fitness of the three species in monocultures. In contrast, interspecific interactions clearly influenced the fitness of all three species, both positively and negatively. Temperature regime did have a substantial effect on the interactions between the species. In the two-species treatment, temperature regime altered the interaction from a sort of mutualism to commensalism. In addition, the strength of the interspecific interactions changed depending on the temperature regime in the three-species treatment. This experiment confirms that interactions between the species can change depending on the abiotic environment; these results show that it is important to incorporate the effect of fluctuations on interspecific interactions to predict the effect of climate change on biodiversity. PMID:26147103

  10. The impact of temperature fluctuations on the large-scale clustering of the Lyα forest

    NASA Astrophysics Data System (ADS)

    Greig, Bradley; Bolton, James S.; Wyithe, J. Stuart B.

    2015-03-01

    We develop a semi-analytic method for assessing the impact of the large-scale IGM temperature fluctuations expected following He II reionization on three-dimensional clustering measurements of the Lyα forest. Our methodology builds upon the existing large volume, mock Lyα forest survey simulations presented by Greig et al. by including a prescription for a spatially inhomogeneous ionizing background, temperature fluctuations induced by patchy He II photoheating and the clustering of quasars. This approach enables us to achieve a dynamic range within our semi-analytic model substantially larger than currently feasible with computationally expensive, fully numerical simulations. The results agree well with existing numerical simulations, with large-scale temperature fluctuations introducing a scale-dependent increase in the spherically averaged 3D Lyα forest power spectrum of up to 20-30 per cent at wavenumbers k ˜ 0.02 Mpc- 1. Although these large-scale thermal fluctuations will not substantially impact upon the recovery of the baryon acoustic oscillation scale from existing and forthcoming dark energy spectroscopic surveys, any complete forward modelling of the broad-band term in the Lyα correlation function will none the less require their inclusion.

  11. KINETICS OF LEAF TEMPERATURE FLUCTUATION AFFECT ISOPRENE EMISSION FROM RED OAK (QUERCUS RUBRA) LEAVES

    EPA Science Inventory

    Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated the natural fluctuations on leaf temperature and the effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the to...

  12. Large fluctuations in the hydrogen-ionizing background and mean free path following the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Davies, Frederick B.; Furlanetto, Steven R.

    2016-08-01

    Extremely large opaque troughs in the Lyα forest have been interpreted as a sign of an extended reionization process below z ˜ 6. Such features are impossible to reproduce with simple models of the intergalactic ionizing background that assume a uniform mean free path of ionizing photons. We build a self-consistent model of the ionizing background that includes fluctuations in the mean free path due to the varying strength of the ionizing background and large-scale density field. The dominant effect is the suppression of the ionizing background in large-scale voids due to `self-shielding' by an enhanced number of optically thick absorbers. Our model results in a distribution of 50 Mpc h-1 Lyα forest effective optical depths that significantly improves agreement with the observations at z ˜ 5.6. Extrapolation to z ˜ 5.4 and 5.8 appears promising, but matching the mean background evolution requires evolution in the absorber population beyond the scope of the present model. We also demonstrate the need for extremely large volumes (>400 Mpc on a side) to accurately determine the incidence of rare large-scale features in the Lyα forest.

  13. Large fluctuations in the hydrogen-ionizing background and mean free path following the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Davies, Frederick B.; Furlanetto, Steven R.

    2016-04-01

    Extremely large opaque troughs in the Lyα forest have been interpreted as a sign of an extended reionization process below z ˜ 6. Such features are impossible to reproduce with simple models of the intergalactic ionizing background that assume a uniform mean free path of ionizing photons. We build a self-consistent model of the ionizing background that includes fluctuations in the mean free path due to the varying strength of the ionizing background and large-scale density field. The dominant effect is the suppression of the ionizing background in large-scale voids due to "self-shielding" by an enhanced number of optically thick absorbers. Our model results in a distribution of 50 Mpc/h Lyα forest effective optical depths that significantly improves agreement with the observations at z ˜ 5.6. Extrapolation to z ˜ 5.4 and z ˜ 5.8 appears promising, but matching the mean background evolution requires evolution in the absorber population beyond the scope of the present model. We also demonstrate the need for extremely large volumes ( > 400 Mpc on a side) to accurately determine the incidence of rare large-scale features in the Lyα forest.

  14. Impact of fluctuating temperatures on development of the koinobiont endoparasitoid Venturia canescens.

    PubMed

    Spanoudis, Christos G; Pappas, Christos S; Delpisi, Argyroula G; Andreadis, Stefanos S; Savopoulou-Soultani, Matilda

    2015-07-01

    The effect of temperature on the biology of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. Herein we studied the influence of fluctuating temperatures on biological parameters of V. canescens. Parasitized fifth-instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were reared individually in incubators at six fluctuating temperature regimes (15-19.5°C with a mean of 17.6°C, 17.5-22.5°C with a mean of 19.8°C, 20-30°C with a mean of 22.7°C, 22.5-27.5°C with a mean of 25°C, 25.5-32.5°C with a mean of 28.3°C and 28.5-33°C with a mean of 30°C) until emergence and death of V. canescens adults. Developmental time from parasitism to adult eclosion, adult longevity and survival were recorded at each fluctuating temperature regime. In principle, developmental time decreased with an increase of the mean temperature of the fluctuating temperature regime. Upper and lower threshold temperatures for total development were estimated at 34.9 and 6.7°C, respectively. Optimum temperature for development and thermal constant were 28.6°C and 526.3 degree days, respectively. Adult longevity was also affected by fluctuating temperature, as it was significantly reduced at the highest mean temperature (7.0 days at 30°C) compared to the lowest one (29.4 days at 17.6°C). Survival was low at all tested fluctuating temperatures, apart from mean fluctuating temperature of 25°C (37%). Understanding the thermal biology of V. canescens under more natural conditions is of critical importance in applied contexts. Thus, predictions of biological responses to fluctuating temperatures may be used in population forecasting models which potentially influence decision-making in IPM programs. PMID:25965020

  15. Homeostasis of plasma membrane viscosity in fluctuating temperatures.

    PubMed

    Martinière, Alexandre; Shvedunova, Maria; Thomson, Adrian J W; Evans, Nicola H; Penfield, Steven; Runions, John; McWatters, Harriet G

    2011-10-01

    Temperature has a direct effect at the cellular level on an organism. For instance, in the case of biomembranes, cooling causes lipids to lose entropy and pack closely together. Reducing temperature should, in the absence of other factors, increase the viscosity of a lipid membrane. We have investigated the effect of temperature variation on plasma membrane (PM) viscosity. We used dispersion tracking of photoactivated green fluorescent protein (GFP) and fluorescence recovery after photobleaching in wild-type and desaturase mutant Arabidopsis thaliana plants along with membrane lipid saturation analysis to monitor the effect of temperature and membrane lipid composition on PM viscosity. Plasma membrane viscosity in A. thaliana is negatively correlated with ambient temperature only under constant-temperature conditions. In the more natural environment of temperature cycles, plants actively manage PM viscosity to counteract the direct effects of temperature. Plasma membrane viscosity is regulated by altering the proportion of desaturated fatty acids. In cold conditions, cell membranes accumulate desaturated fatty acids, which decreases membrane viscosity and vice versa. Moreover, we show that control of fatty acid desaturase 2 (FAD2)-dependent lipid desaturation is essential for this homeostasis of membrane viscosity. Finally, a lack of FAD2 function results in aberrant temperature responses. PMID:21762166

  16. Spectral analysis of temperature and Brunt-Vaisala frequency fluctuations observed by radiosondes

    NASA Technical Reports Server (NTRS)

    Tsuda, T.; Vanzandt, T. E.; Kato, S.; Fukao, S.; Sato, T.

    1989-01-01

    Recent studies have revealed that vertical wave number spectra of wind velocity and temperture fluctuations in the troposphere and the lower stratosphere are fairly well explained by a saturated gravity wave spectrum. But N(2) (N:Brunt-Vaisala (BV) frequency) spectra seem to be better for testing the scaling of the vertical wave number spectra in layers with different stratifications, beause its energy density is proportional only to the background value of N(2), while that for temperature depends on both the BV frequency and the potential temperature. From temperature profiles observed in June to August 1987 over the MU Observatory, Japan, by using a radiosonde with 30 m height resolution, N(2) spectra are determined in the 2 to 8.5 km (troposphere) and 18.5 to 25 km (lower stratosphere) ranges. Although individual spectra show fairly large day-by-day variability, the slope of the median of 34 spectra agrees reasonably with the theoretical value of -1 in the wave number range of 6 x 10(-4) similar to 3 x 10(-3) (c/m). The ratio of the spectral energy between these two height regions is about equal to the ratio of N(2), consistent with the prediction of saturated gravity wave theory.

  17. Effects of daily fluctuating temperatures on the Drosophila-Leptopilina boulardi parasitoid association.

    PubMed

    Delava, Emilie; Fleury, Frédéric; Gibert, Patricia

    2016-08-01

    Koinobiont parasitoid insects, which maintain intimate and long-term relationships with their arthropod hosts, constitute an association of ectothermic organisms that is particularly sensitive to temperature variations. Because temperature shows pronounced natural daily fluctuations, we examined if experiments based on a constant temperature range can mask the real effects of the thermal regime on host-parasitoid interactions. The effects of two fluctuating thermal regimes on several developmental parameters of the Drosophila larval parasitoid Leptopilina boulardi were analyzed in this study. Regime 1 included a range of 16-23-16°C and regime 2 included a range of 16-21-26-21-16°C (mean temperature 20.1°C) compared to a 20.1°C constant temperature. Under an average temperature of 20.1°C, which corresponds to a cold condition of L. boulardi development, we showed that the success of parasitism is significantly higher under a fluctuating temperature regime than at constant temperature. A fluctuating regime also correlated with a reduced development time of the parasitoids. In contrast, the thermal regime did not affect the ability of Drosophila to resist parasitoid infestation. Finally, we demonstrated that daily temperature fluctuation prevented the entry into diapause for this species, which is normally observed at a constant temperature of 21°C. Overall, the results reveal that constant temperature experiments can produce misleading results, highlighting the need to study the thermal biology of organisms under fluctuating regimes that reflect natural conditions as closely as possible. This is particularly a major issue in host-parasitoid associations, which constitute a good model to understand the effect of climate warming on interacting species. PMID:27503721

  18. Interaction of Mean Temperature and Daily Fluctuation Influences Dengue Incidence in Dhaka, Bangladesh.

    PubMed

    Sharmin, Sifat; Glass, Kathryn; Viennet, Elvina; Harley, David

    2015-01-01

    Local weather influences the transmission of the dengue virus. Most studies analyzing the relationship between dengue and climate are based on relatively coarse aggregate measures such as mean temperature. Here, we include both mean temperature and daily fluctuations in temperature in modelling dengue transmission in Dhaka, the capital of Bangladesh. We used a negative binomial generalized linear model, adjusted for rainfall, anomalies in sea surface temperature (an index for El Niño-Southern Oscillation), population density, the number of dengue cases in the previous month, and the long term temporal trend in dengue incidence. In addition to the significant associations of mean temperature and temperature fluctuation with dengue incidence, we found interaction of mean and temperature fluctuation significantly influences disease transmission at a lag of one month. High mean temperature with low fluctuation increases dengue incidence one month later. Besides temperature, dengue incidence was also influenced by sea surface temperature anomalies in the current and previous month, presumably as a consequence of concomitant anomalies in the annual rainfall cycle. Population density exerted a significant positive influence on dengue incidence indicating increasing risk of dengue in over-populated Dhaka. Understanding these complex relationships between climate, population, and dengue incidence will help inform outbreak prediction and control. PMID:26161895

  19. Interaction of Mean Temperature and Daily Fluctuation Influences Dengue Incidence in Dhaka, Bangladesh

    PubMed Central

    Sharmin, Sifat; Glass, Kathryn; Viennet, Elvina; Harley, David

    2015-01-01

    Local weather influences the transmission of the dengue virus. Most studies analyzing the relationship between dengue and climate are based on relatively coarse aggregate measures such as mean temperature. Here, we include both mean temperature and daily fluctuations in temperature in modelling dengue transmission in Dhaka, the capital of Bangladesh. We used a negative binomial generalized linear model, adjusted for rainfall, anomalies in sea surface temperature (an index for El Niño-Southern Oscillation), population density, the number of dengue cases in the previous month, and the long term temporal trend in dengue incidence. In addition to the significant associations of mean temperature and temperature fluctuation with dengue incidence, we found interaction of mean and temperature fluctuation significantly influences disease transmission at a lag of one month. High mean temperature with low fluctuation increases dengue incidence one month later. Besides temperature, dengue incidence was also influenced by sea surface temperature anomalies in the current and previous month, presumably as a consequence of concomitant anomalies in the annual rainfall cycle. Population density exerted a significant positive influence on dengue incidence indicating increasing risk of dengue in over-populated Dhaka. Understanding these complex relationships between climate, population, and dengue incidence will help inform outbreak prediction and control. PMID:26161895

  20. First measurements of core electron temperature fluctuations in Alcator C-Mod via Correlation ECE

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A.; Howard, N.; Oi, C.; Rice, J.; Gao, C.; Ennever, P.; Porkolab, M.; Hubbard, A.; Greenwald, M.

    2012-10-01

    A new Correlation Electron Cyclotron Emission (CECE) diagnostic has been installed at Alcator C-Mod to measure broadband, turbulent electron temperature fluctuations in the core region (ρ<0.9). This diagnostic has high poloidal resolution (φ0< 0.5cm ), and can measure long wavelength turbulence (kθρs< 0.4). We obtained the first electron temperature fluctuation data in Ohmic and ICRH plasmas. It was observed that the core (ρ˜0.8) electron temperature fluctuation level decreases as the Ohmic confinement regime transitions from Linear Ohmic Confinement (LOC) to Saturated Ohmic Confinement (SOC), while edge fluctuation levels (ρ> 0.9) stay similar in amplitude. These first quantitative, local electron temperature fluctuation measurements in C-Mod demonstrate that core turbulence characteristics change between LOC and SOC. In order to interpret the data, linear stability analysis is being performed, and the relation between fluctuation level and other plasma parameters is being investigated. This talk will describe the new CECE diagnostic, the SOC/LOC measurements, and associated gyrokinetic analyses.

  1. Spatial Fluctuations in the Diffuse Cosmic X-Ray Background. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shafer, R. A.

    1983-01-01

    The bright, essentially isotropic, X-ray sky flux above 2 keV yields information on the universe at large distances. However, a definitive understanding of the origin of the flux is lacking. Some fraction of the total flux is contributed by active galactic nuclei and clusters of galaxies, but less than one percent of the total is contributed by the or approximately 3 keV band resolved sources, which is the band where the sky flux is directly observed. Parametric models of AGN (quasar) luminosity function evolution are examined. Most constraints are by the total sky flux. The acceptability of particular models hinges on assumptions currently not directly testable. The comparison with the Einstein Observatory 1 to keV low flux source counts is hampered by spectral uncertainties. A tentative measurement of a large scale dipole anisotropy is consistent with the velocity and direction derived from the dipole in the microwave background. The impact of the X-ray anisotropy limits for other scales on studies of large-scale structure in the universe is sketched. Models of the origins of the X-ray sky flux are reviewed, and future observational programs outlined.

  2. Measurement of Temperature Fluctuations and Microscopic Growth Rates in a Silicon Floating Zone and Microgravity

    NASA Technical Reports Server (NTRS)

    Schweizer, Markus; Croell, Arne

    1999-01-01

    A silicon crystal growth experiment has been accomplished using the floating-zone technique under microgravity on a sounding rocket (TEXUS 36). Measurements of temperature fluctuations in the silicon melt zone due to time dependent thermocapillary convection (Marangoni convection) and an observation of the microscopic growth rate were simultaneously performed during the experiment. Temperature fluctuations of about 0.5 - 0.7 C with a frequency range < 0.5Hz were detectable. The microscopic growth rate fluctuates considerably around the average growth rate of 1 mm/min: Growth rates up to 3 to 4mm/min, close to zero mm/min, as well as negative values (backmelting) were observed. Dopant striations are clearly visible in the Sb-doped crystal. They were characterized by Spreading Resistance measurements and Differential Interference Contrast microscopy. The frequencies of temperature fluctuations, microscopic growth rates, and the dopant inhomogeneities correspond quite well, with main frequencies between 0.1 and 0.3 Hz. 3D numerical simulations were performed to predict the optimum position of the temperature sensor, and the characteristic temperature amplitudes and frequencies. At a position 3.4mm above the interface and 1.4mm inside the melt, equivalent to the sensor tip position in the experiment, temperature fluctuations up to 1.8 C and frequencies ? 0.25Hz were found in the simulations.

  3. High temperature conductance fluctuations in an InGaAs/InAlAs open quantum dot

    NASA Astrophysics Data System (ADS)

    Faniel, S.; Hackens, B.; Delfosse, F.; Gustin, C.; Boutry, H.; Huynen, I.; Bayot, V.; Wallart, X.; Bollaert, S.; Cappy, A.

    2002-03-01

    We present magnetotransport measurements in an open quantum dot realized on an InGaAs/InAlAs narrow quantum well. The measurements are performed on a 500 nm diameter circular cavity patterned by electron beam lithography and wet etching. The electronic density can be tuned by a Ti/Pt/Au electrostatic gate. The sample is characterized down to 300mK in a magnetic field up to 5T. We observe a superposition of slowly varying reproducible magnetoconductance fluctuations and a rich pattern of universal conductance fluctuations whose characteristic magnetic field scale is much shorter. We study the evolution of these two types of fluctuations as a function of the temperature (up to 230K) and the gate voltage. We notice the persistence of fluctuations up to unexpectedly high temperatures.

  4. Lyman-tomography of Cosmic Infrared Background Fluctuations with Euclid: Probing Emissions and Baryonic Acoustic Oscillations at z ≳ 10

    NASA Astrophysics Data System (ADS)

    Kashlinsky, A.; Arendt, R. G.; Atrio-Barandela, F.; Helgason, K.

    2015-11-01

    The Euclid space mission, designed to probe evolution of the Dark Energy (DE), will map a large area of the sky at three adjacent near-IR filters, Y, J, and H. This coverage will also enable mapping source-subtracted cosmic infrared background (CIB) fluctuations with unprecedented accuracy on sub-degree angular scales. Here, we propose methodology, using the Lyman-break tomography applied to the Euclid-based CIB maps, to accurately isolate the history of CIB emissions as a function of redshift from 10 ≲ z ≲ 20 and to identify the baryonic acoustic oscillations (BAOs) at those epochs. To identify the BAO signature, we would assemble individual CIB maps over conservatively large contiguous areas of ≳400 deg2. The method can isolate the CIB spatial spectrum by z to sub-percent statistical accuracy. We illustrate this with a specific model of CIB production at high z normalized to reproduce the measured Spitzer-based CIB fluctuation. We show that even if the latter contains only a small component from high-z sources, the amplitude of that component can be accurately isolated with the methodology proposed here and the BAO signatures at z ≳ 10 are recovered well from the CIB fluctuation spatial spectrum. Probing the BAO at those redshifts will be an important test of the underlying cosmological paradigm and would narrow the overall uncertainties on the evolution of cosmological parameters, including the DE. Similar methodology is applicable to the planned WFIRST mission, where we show that a possible fourth near-IR channel at ≥2 μm would be beneficial.

  5. Measurements of temperature and pressure fluctuations in the T prime 2 cryogenic wind tunnel

    NASA Technical Reports Server (NTRS)

    Blanchard, A.; Dor, J. B.; Breil, J. F.

    1980-01-01

    Cold wire measurement of temperature fluctuations were made in a DERAT T'2 induction powered cryogenic wind tunnel for 2 types of liquid nitrogen injectors. Thermal turbulence measured in the tranquilization chamber depends to a great extent on the injector used; for fine spray of nitrogen drops, this level of turbulence seemed completely acceptable. Fluctuations in static pressure taken from the walls of the vein by Kulite sensors showed that there was no increase in aerodynamic noise during cryogenic gusts.

  6. Photosynthetic response of switchgrass ecotypes to fluctuating growth temperatures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Switchgrass (Panicum virgatum L.), a warm-season C4 grass that shows excellent potential as a bioenergy feedstock and conservation crop, is widely adapted throughout North America, but its productivity tends to decline with increasing latitude. In northern regions where growing season temperatures c...

  7. ESTIMATATION OF GROWTH OF CLOSTRIDIUM PERFRINGENS IN COOKED BEEF UNDER FLUCTUATING TEMPERATURE CONDITIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new concept for estimating the bacterial growth under temperature fluctuations was hypothesized and validated using Clostridium perfringens as a test organism. This new methodology was based on the Gompertz models to calculate the equivalent growth times under different temperatures, and estimate...

  8. Zero-Temperature Fluctuations in Short-Range Spin Glasses

    NASA Astrophysics Data System (ADS)

    Arguin, L.-P.; Newman, C. M.; Stein, D. L.; Wehr, J.

    2016-06-01

    We consider the energy difference restricted to a finite volume for certain pairs of incongruent ground states (if they exist) in the d-dimensional Edwards-Anderson Ising spin glass at zero temperature. We prove that the variance of this quantity with respect to the couplings grows proportionally to the volume in any d ≥ 2. An essential aspect of our result is the use of the excitation metastate. As an illustration of potential applications, we use this result to restrict the possible structure of spin glass ground states in two dimensions.

  9. A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Chinitz, W.; Foy, E.; Rowan, G.; Goldstein, D.

    1982-01-01

    The use of probability theory to determine the effects of turbulent fluctuations on reaction rates in turbulent combustion systems is briefly reviewed. Results are presented for the effect of species fluctuations in particular. It is found that turbulent fluctuations of species act to reduce the reaction rates, in contrast with the temperature fluctuations previously determined to increase Arrhenius reaction rate constants. For the temperature fluctuations, a criterion is set forth for determining if, in a given region of a turbulent flow field, the temperature can be expected to exhibit ramp like fluctuations. Using the above results, along with results previously obtained, a model is described for testing the effects of turbulent fluctuations of temperature and species on reaction rates in computer programs dealing with turbulent reacting flows. An alternative model which employs three variable probability density functions (temperature and two species) and is currently being formulated is discussed as well.

  10. Soil cover in the southern forest-steppe of the Central Russian Upland against the background of centennial climate fluctuations

    NASA Astrophysics Data System (ADS)

    Smirnova, L. G.; Kukharuk, N. S.; Chendev, Yu. G.

    2016-07-01

    Special approaches and algorithms for studying the response of zonal soils and the soil cover of the forest-steppe zone to climate fluctuations were developed on the basis of data of repeated soil surveys. They made it possible to analyze the particular transformations of the soil cover as indicators of short-term climate fluctuations in the southern forest-steppe of the Central Russian Upland. Vector soil maps and related databases on soil polygons were developed using GIS technologies. Changes in the climatic conditions between two rounds of large-scale soil surveys in 1971 and 1991 reflecting the so-called Brückner cycles were identified. A characteristic feature of climate change during that period was the rise in the mean annual air temperature by 0.2°C and an increase in the mean annual precipitation by 83 mm. In response to this change, the area of leached chernozems (Luvic Chernozems) on the interfluves somewhat increased, whereas the area of typical chernozems (Haplic Chernozems) decreased.

  11. The effect of temperature fluctuations of reaction rate constants in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Chinitz, W.; Antaki, P. J.; Kassar, G. M.

    1981-01-01

    Current models of turbulent reacting flows frequently use Arrhenius reaction rate constants obtained from static or laminar flow theory and/or experiments, or from best fits of static, laminar, and turbulent data. By treating the reaction rate constant as a continuous random variable which is temperature-dependent, the present study assesses the effect of turbulent temperature fluctuations on the reaction rate constant. This model requires that a probability density function (PDF) describing the nature of the fluctuations be specified. Three PDFs are examined: the clipped Gaussian, the beta PDF, and the ramp model. All the models indicate that the reaction rate constant is greater in a turbulent flow field than in an equivalent laminar flow. In addition, an amplification ratio, which is the ratio of the turbulent rate constant to the laminar rate constant, is defined and its behavior as a function of the mean temperature fluctuations is described

  12. Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements

    SciTech Connect

    Rudakov, D.L.; Boedo, J.A.; Moyer, R.A.; Stangeby, P.C.; McLean, A.; Watkins, J.G.

    2004-10-01

    Swept Langmuir probes are widely used to measure electron temperature (T{sub e}) in laboratory plasmas by performing an exponential fit to the measured volt-ampere (I-V) characteristic. Often the probe voltage sweep frequency is much lower than the characteristic frequencies of the plasma fluctuations and a time-averaged I-V characteristic is used for the fit. We show by numerical modeling that in the presence of T{sub e} fluctuations with frequencies well above the voltage sweep frequency this standard technique applied to a swept single probe tends to read higher than the actual time-averaged T{sub e} provided no correlated plasma potential (V{sub p}) fluctuations are present. In the presence of coupled T{sub e} and V{sub p} fluctuations a slowly swept single probe may read either higher or lower than the average T{sub e}, depending on the relative amplitude and phase of the temperature and potential fluctuations. In contrast, swept double probe measurements of T{sub e} are virtually unaffected by either T{sub e} or V{sub p} fluctuations.

  13. Fluctuation induced diamagnetism in the zero magnetic field limit in a low temperature superconducting alloy.

    PubMed

    Mosqueira, J; Carballeira, C; Vidal, F

    2001-10-15

    By using a Pb-18 at. % In alloy, the fluctuation induced diamagnetism was measured in the zero magnetic field limit, never observed until now in a low-T(C) superconductor. This allows us to disentangle the dynamic and the nonlocal electrodynamic effects from the short-wavelength fluctuation effects. The latter may be explained on the grounds of the Gaussian-Ginzburg-Landau approach by introducing a total energy cutoff in the fluctuation spectrum, which strongly suggests the existence of a well-defined temperature in the normal state above which all fluctuating modes vanish. This conclusion may also have implications when describing the superconducting state formation of the high-T(C) cuprates. PMID:11690233

  14. Temperature fluctuations underneath the ice in Diamond Lake, Hennepin County, Minnesota

    NASA Astrophysics Data System (ADS)

    Kletetschka, Gunther; Fischer, Tomas; Mls, Jiří; DěDeček, Petr

    2013-06-01

    Diamond Lake in Minnesota is covered every winter with ice and snow providing a modified thermal insulation between water and air. Autonomous temperature sensors, data loggers, were placed in this lake so that hourly measurements could be obtained from the snow-covered ice and water. The sensors that became frozen measured damped and delayed thermal response from the air-temperature fluctuation. Those sensors that were deeper within the snow-covered ice measured continuous, almost constant, temperature values near freezing. Several of them were within the liquid water and responded with a fluctuation of 24 h periods of amplitudes up to 0.2°C. Our analysis of the vertical temperature profiles suggested that the source of periodic water heating comes from the lake bottom. Because of the absence of daily temperature variations of the snow-covered ice, the influence of the air-temperature fluctuation can be ruled out. We attribute the heating process to the periodic inflow of groundwater to the lake and the cooling to the heat diffusion to the overlying ice cover. The periodic groundwater inflow is interpreted due to solid Earth tides, which cause periodic fluctuations of the groundwater pressure head.

  15. Observation of Aharonov-Bohm and Al'tshuler-Aronov-Spivak oscillations in the background of universal conductance fluctuations in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Mtsuko, Davie; Aslan, Tahir; Ncube, Siphephile; Coleman, Christopher; Wamwangi, Daniel; Bhattacharyya, Somnath

    2016-02-01

    Magnetoresistance (MR) oscillations of multiple periodicities are recorded in singly connected silicon nanowires of diameter ≈50 \\text{nm} . At 100 K we observe oscillations of periodicity ≈1.78 \\text{T} and 0.444 T corresponding to h/e and h/4e Aharonov-Bohm (AB) oscillations, whereas at 10 K we record periodicities of 0.98 T, 0.49 T and 0.25 T corresponding to h/e, h/2e (Al'tshuler-Aronov-Spivak (AAS)) and h/4e oscillations. At 2.5 K we find magnetoresistance oscillations with multiple periodicities of 1.3 T, 0.52 T, and 0.325 T corresponding to AB and AAS oscillations. The h/2e and h/4e peaks can be attributed to the interference of time-reversed paths originating from the core orbits that scatter coherently on the surface of the nanowires multiple times. We also observed 20 mT and 60 mT oscillations of small amplitude superimposed on a quasi-periodic background which we attribute to the quantum interference of special surface states associated with skipping orbits that propagate quasi-ballistically. The aperiodic fluctuations in the MR at all temperatures are universal conductance fluctuations (UCF) originating from randomly spaced impurity scattering in the core of the nanowire.

  16. Fine-scale temperature fluctuation and modulation of Dirofilaria immitis larval development in Aedes aegypti.

    PubMed

    Ledesma, Nicholas; Harrington, Laura

    2015-04-15

    We evaluated degree-day predictions of Dirofilaria immitis development (HDU) under constant and fluctuating temperature treatments of equal average daily temperature. Aedes aegypti mosquitoes were infected with D. immitis microfilariae and parasite development was recorded at set time points in dissected mosquitoes. Time to L3 development in Malpighian tubules and detection in mosquito heads was shorter for larvae experiencing a daily regime of 19±9°C than larvae at constant 19°C; larval development rate in Malpighian tubules was slower in fluctuating regimes maintained above the 14°C developmental threshold than larvae under constant temperatures. We showed that hourly temperature modeling more accurately predicted D. immitis development to infective L3 stage. Development time differed between fluctuating and constant temperature treatments spanning the 14°C development threshold, implicating a physiological basis for these discrepancies. We conclude that average daily temperature models underestimate L3 development-and consequently dog heartworm transmission risk-at colder temperatures, and spatiotemporal models of D. immitis transmission risk should use hourly temperature data when analyzing high daily temperature ranges spanning 14°C. PMID:25747489

  17. The relation between isolated tree brightness temperature and grass background brightness temperature

    NASA Astrophysics Data System (ADS)

    Krusinger, A. E.

    1983-08-01

    This study involves thermal infrared measurement for the determination of the diurnal and seasonal aspects of the relations between isolated evergreen tress and a cut grass background and between a large truck brightness temperature and cut grass, uncut grass, and bare soil backgrounds. Seasonal changes in the tree brightness temperature-background brightness temperature contrast ranged from 4 to 5 C in February and March to 1 to 2 C in July. At night, the thermal contrast between trees and background was found to vary inversely with long wave incoming radiation, which is a measure of cloudiness. A study of the change in the thermal contrast during the night showed that, during clear weather, the contrast was at a peak a few hours after sundown and decreased the rest of the night. In overcast conditions, a reduced contrast peak occurred at sundown and very gradually diminished through the night. Isothermal conditions were found to occur in the early mornings, and the time of these occurrences changed seasonally, in a systematic manner.

  18. Impacts of Short-Term Meteorological Fluctuations on Near-Surface Ground Temperatures in Spitsbergen, Svalbard

    NASA Astrophysics Data System (ADS)

    Strand, S. M.; Christiansen, H. H.

    2015-12-01

    The state of permafrost in a given area is dependent on heat balance, which is largely controlled by major trends in climate. However, smaller-scale meteorological events can impact the thermal regime as well, depending on a number of ground surface factors. This project investigates the impact of short-term meteorological fluctuations on near-surface ground temperatures in central Spitsbergen, Svalbard, and identifies the depths at which these changes are perceptible. The Svalbard archipelago is subject to significant air temperature fluctuations due to its maritime climate; this can result in wintertime rain events. Even when snow is present, rain has the potential to notably affect near-surface ground temperatures. A few studies have examined Svalbard ground temperatures during specific wintertime warm periods, but no previous research has utilized the available long-term active layer and permafrost temperature data to compare distinct events. Though summer air temperatures on Svalbard are more stable, particularly warm intervals alter active layer thaw progression. By comparing high-resolution air temperature data with high-resolution ground temperature data, the temporal and spatial impact of short-term meteorological fluctuations is assessed and compared between sites from varying locations and lithology.

  19. Variable-Temperature Tip-Enhanced Raman Spectroscopy of Single-Molecule Fluctuations and Dynamics.

    PubMed

    Park, Kyoung-Duck; Muller, Eric A; Kravtsov, Vasily; Sass, Paul M; Dreyer, Jens; Atkin, Joanna M; Raschke, Markus B

    2016-01-13

    Structure, dynamics, and coupling involving single-molecules determine function in catalytic, electronic or biological systems. While vibrational spectroscopy provides insight into molecular structure, rapid fluctuations blur the molecular trajectory even in single-molecule spectroscopy, analogous to spatial averaging in measuring large ensembles. To gain insight into intramolecular coupling, substrate coupling, and dynamic processes, we use tip-enhanced Raman spectroscopy (TERS) at variable and cryogenic temperatures, to slow and control the motion of a single molecule. We resolve intrinsic line widths of individual normal modes, allowing detailed and quantitative investigation of the vibrational modes. From temperature dependent line narrowing and splitting, we quantify ultrafast vibrational dephasing, intramolecular coupling, and conformational heterogeneity. Through statistical correlation analysis of fluctuations of individual modes, we observe rotational motion and spectral fluctuations of the molecule. This work demonstrates single-molecule vibrational spectroscopy beyond chemical identification, opening the possibility for a complete picture of molecular motion ranging from femtoseconds to minutes. PMID:26679007

  20. Seasonal cycle dependence of temperature fluctuations in the atmosphere. Master's thesis

    SciTech Connect

    Tobin, B.F.

    1994-08-01

    The correlation statistics of meteorological fields have been of interest in weather forecasting for many years and are also of interest in climate studies. A better understanding of the seasonal variation of correlation statistics can be used to determine how the seasonal cycle of temperature fluctuations should be simulated in noise-forced energy balance models. It is shown that the length scale does have a seasonal dependence and will have to be handled through the seasonal modulation of other coefficients in noise-forced energy balance models. The temperature field variance and spatial correlation fluctuations exhibit seasonality with fluctuation amplitudes larger in the winter hemisphere and over land masses. Another factor contributing to seasonal differences is the larger solar heating gradient in the winter.

  1. Study of Turbulent Fluctuations Driven by the Electron Temperature Gradient in the National Spherical Torus Experiment

    SciTech Connect

    Mazzucato, E.; Bell, R. E.; Ethier, S.; Hosea, J. C.; Kaye, S. M.; LeBlanc, B. P.; Lee, W. W.; Ryan, P. M.; Smith, D. R.; Wang, W. X.; Wilson, J. R.

    2009-03-26

    Various theories and numerical simulations support the conjecture that the ubiquitous problem of anomalous electron transport in tokamaks may arise from a short-scale turbulence driven by the electron temperature gradient. To check whether this turbulence is present in plasmas of the National Spherical Torus Experiment (NSTX), measurements of turbulent fluctuations were performed with coherent scattering of electromagnetic waves. Results from plasmas heated by high harmonic fast waves (HHFW) show the existence of density fluctuations in the range of wave numbers k⊥ρe=0.1-0.4, corresponding to a turbulence scale length of the order of the collisionless skin depth. Experimental observations and agreement with numerical results from the linear gyro-kinetic GS2 code indicate that the observed turbulence is driven by the electron temperature gradient. These turbulent fluctuations were not observed at the location of an internal transport barrier driven by a negative magnetic shear.

  2. Effects of rapid temperature fluctuations prior to breeding on reproductive efficiency in replacement gilts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recently, we determined that rapidly cooling pigs after acute heat stress (HS) resulted in a pathological condition, and because rapid temperature fluctuations are often associated with reduced reproductive success in sows it lends itself to the hypothesis that these conditions may be linked. Study ...

  3. Large diurnal temperature fluctuations negatively influence Aedes aegypti (Diptera: Culicidae) life-history traits.

    PubMed

    Carrington, Lauren B; Seifert, Stephanie N; Willits, Neil H; Lambrechts, Louis; Scott, Thomas W

    2013-01-01

    Seasonal variation in dengue virus transmission in northwestern Thailand is inversely related to the magnitude of diurnal temperature fluctuations, although mean temperature does not vary significantly across seasons. We tested the hypothesis that diurnal temperature fluctuations negatively influence epidemiologically important life-history traits of the primary dengue vector, Aedes aegypti (L.), compared with a constant 26 degrees C temperature. A large diurnal temperature range (DTR) (approximately equals 18 degrees C daily swing) extended immature development time (>1 d), lowered larval survival (approximately equals 6%), and reduced adult female reproductive output by 25% 14 d after blood feeding, relative to the constant 26 degreesC temperature. A small DTR (approximately equal 8 degrees C daily swing) led to a negligible or slightly positive effect on the life history traits tested. Our results indicate that there is a negative impact of large DTR on mosquito biology and are consistent with the hypothesis that, in at least some locations, large temperature fluctuations contribute to seasonal reduction in dengue virus transmission. PMID:23427651

  4. Mars Background Noise Temperatures Received by Spacecraft Antennas

    NASA Astrophysics Data System (ADS)

    Ho, C.; Slobin, S.; Sue, M.; Njoku, E.

    2002-01-01

    Radio noise emissions seen by a spacecraft orbiting Mars or a lander located on the Martian surface are expected to be from Mars' atmospheric emission, surface noise, and extra-Martian sources. Compared with Earth, Mars has lower surface temperatures and much lower atmospheric absorption and radiation. However, Mars has higher surface emissivity due to the roughness of soil and rocks. Because of very low atmospheric density and optical depth, Mars' atmospheric emission from oxygen and water vapor is almost negligible. The upwelling brightness temperature at Mars is caused mainly by its surface temperature, with strong local time and latitudinal dependence. Downwelling brightness temperature is dominated by sky temperature. The actual radio noise contributing to the antenna temperature is also a function of antenna orientation, elevation angle, and gain pattern. Assuming a dish antenna with 1-m diameter, for a downward-looking antenna the total noise temperature is about the same as the Earth's for all frequency bands of interest, with ±15 percent deviations. For an upward-looking antenna, the noise temperature is less than half that of Earth.

  5. Analytical Comparisons of Tree Ring Data, Greenland Ice Core Temperatures and Temperature Fluctuations of the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Otto, James; Roberts, Jim; Dahiya, Jai

    2012-10-01

    Embedded in various events on Earth are data that allow us to map the temperature of the Earth over many years. In this work we have chosen the temperature fluctuations in the Sargasso sea, the changing patterns in tree ring growth and temperature fluctuations in Greenland ice core samples for comparison with a goal to understanding the patterns in global warming. Signatures have been identified that predate the Industrial Revolution, which had been blamed for much of global warming, that indicate that Earth temperatures have enjoyed numerous intervals of both global warming and global cooling. The intention of this work is not to stir controversy but to make comparisons of scientific data and processes rather than rely on popular opinion or deduction by ``experts'' in climatology to explain global warming.

  6. Analytical Comparisons of Tree Ring Data, Greenland Ice Core Temperatures and Temperature Fluctuations of the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Roberts, James; Dahiya, Jai

    2010-10-01

    Embedded in various events on Earth are data that allow us to map the temperature of the Earth over many years. In this work we have chosen the temperature fluctuations in the Sargasso Sea, the changing patterns in tree ring growth and temperature fluctuations in Greenland ice core samples for comparison with a goal to understanding the patterns in global warming. Signatures have been identified that predate the Industrial Revolution, which had been blamed for much of global warming, that indicate that Earth temperatures have enjoyed numerous intervals of both global warming and global cooling. The intention of this work is not to stir controversy but to provoke legitimate debate based on scientific data and processes rather than popular opinion or deduction by ``experts'' in climatology.

  7. Prediction of growth of Pseudomonas fluorescens in milk during storage under fluctuating temperature.

    PubMed

    Lin, Hao; Shavezipur, Mohammad; Yousef, Ahmed; Maleky, Farnaz

    2016-03-01

    Accurate prediction of growth of undesirable organisms (e.g., Pseudomonas fluorescens) in perishable foods (e.g., milk), held under sub-ideal storage conditions, can help ensure the quality and safety of these foods at the point of consumption. In this investigation, we inoculated sterile milk with P. fluorescens (~10(3) cfu/mL) and monitored inoculum growth behavior at constant and fluctuating storage temperatures. Three storage temperatures, 4 °C, 15 °C and 29 °C, were selected to simulate proper refrigeration conditions (4 °C) and temperature abuse, respectively. To simulate temperature fluctuation, milk held at 4 °C was subjected to temperature shifts to 15 °C or 29 °C for 4 to 6h. A modified logistic model was used to obtain the best-fit curve for the microbial growth under constant storage temperature. The specific growth rates at 4 °C, 15 °C, and 29 °C, obtained from experimental data, were 0.056 ± 0.00, 0.17 ± 0.05, and 0.46 ± 0.02 h(-1), respectively, and the lag time values were 29.5 ± 4.2, 12.7 ± 4.4, and 2.8 ± 0.3h, respectively. A model predicting bacterial growth under different temperature fluctuations was obtained using the growth parameters extracted from constant temperature experiments. Growth behavior predicted by the fluctuating temperature model and that obtained experimentally were in good agreement. Lag time exhibited a larger variation compared with specific growth rate, suggesting that it depends not only on growth temperature but also on the sample population and temperature gradient. Additionally, experimental data showed that changing the temperature during the lag phase induced an additional lag time before growth; however, no significant lag time was observed under the temperature fluctuation during the exponential phase. The results of this study provide information for precise shelf-life determination and reduction of food waste, particularly for milk and milk-containing food products. PMID:26723126

  8. POWER ASYMMETRY IN COSMIC MICROWAVE BACKGROUND FLUCTUATIONS FROM FULL SKY TO SUB-DEGREE SCALES: IS THE UNIVERSE ISOTROPIC?

    SciTech Connect

    Hansen, F. K.; Eriksen, H. K.; Lilje, P. B.; Banday, A. J.; Gorski, K. M. E-mail: h.k.k.eriksen@astro.uio.n E-mail: banday@MPA-Garching.MPG.D

    2009-10-20

    We repeat and extend the analysis of Eriksen et al. and Hansen et al., testing the isotropy of the cosmic microwave background fluctuations. We find that the hemispherical power asymmetry previously reported for the largest scales l = 2-40 extends to much smaller scales. In fact, for the full multipole range l = 2-600, significantly more power is found in the hemisphere centered at (theta = 107{sup 0} +- 10{sup 0}, phi = 226{sup 0} +- 10{sup 0}) in galactic co-latitude and longitude than in the opposite hemisphere, consistent with the previously detected direction of asymmetry for l = 2-40. We adopt a model selection test where the direction and amplitude of asymmetry, as well as the multipole range, are free parameters. A model with an asymmetric distribution of power for l = 2-600 is found to be preferred over the isotropic model at the 0.4% significance level, taking into account the additional parameters required to describe it. A similar direction of asymmetry is found independently in all six subranges of 100 multipoles between l = 2-600. None of our 9800 isotropic simulated maps show a similarly consistent direction of asymmetry over such a large multipole range. No known systematic effects or foregrounds are found to be able to explain the asymmetry.

  9. The effects of fluctuating culture temperature on stress tolerance and antioxidase expression in Esteya vermicola.

    PubMed

    Wang, Yun-bo; Pang, Wen-xing; Yv, Xiao-na; Li, Jing-jie; Zhang, Yong-an; Sung, Chang-keun

    2015-02-01

    The endoparasitic nematophagous fungus, Esteya vermicola, has shown great potential as a biological control agent against the pine wood nematode, Bursaphelenchus xylophilus. Fluctuating culture temperatures can affect fungal yields and fungal tolerance to desiccation, UV radiation, H2O2, and heat stress, as well as antioxidase expression. To explore these effects, E. vermicola cultured under five temperature ranges, 26°C, 15-26°C, 26-35°C, 20-30°C, and 15-35°C, were compared. The cultures grown at lower temperatures showed better growth, stronger tolerance to desiccation, UV, and H2O2 stresses, and increased catalase expression, However, these cultures also showed weaker heat stress tolerance and lower superoxide dismutase expression than the higher-temperature cultures. In particular, the E. vermicola cultured at 20-30°C, i.e., fluctuating in a narrow range around the optimal temperature, showed the best performance. Therefore, for production in practical applications, this narrowly fluctuating, moderate temperature appears to be optimal for yield and stress tolerance in E. vermicola. PMID:25626367

  10. A large temperature fluctuation may trigger an epidemic erythromelalgia outbreak in China

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Zhang, Yonghui; Lin, Hualiang; Lv, Xiaojuan; Xiao, Jianpeng; Zeng, Weilin; Gu, Yuzhou; Rutherford, Shannon; Tong, Shilu; Ma, Wenjun

    2015-03-01

    Although erythromelalgia (EM) has been documented in the literature for almost 150 years, it is still poorly understood. To overcome this limitation, we examined the spatial distribution of epidemic EM, and explored the association between temperature fluctuation and epidemic EM outbreaks in China. We searched all peer-reviewed literature on primary epidemic EM outbreaks in China. A two-stage model was used to characterize the relationship between temperature fluctuation and epidemic EM outbreaks. We observed that epidemic EM outbreaks were reported from 13 provinces during 1960-2014 and they mainly occurred between February and March in southern China. The majority of EM cases were middle school students, with a higher incidence rate in female and resident students. The major clinical characteristics of EM cases included burning, sharp, tingling and/or stinging pain in toes, soles and/or dorsum of feet, fever, erythema and swelling. A large ``V''-shaped fluctuation of daily average temperature (TM) observed during the epidemic EM outbreaks was significantly associated with the number of daily EM cases (β = 1.22, 95%CI: 0.66 ~ 1.79), which indicated that this ``V''-shaped fluctuation of TM probably triggered the epidemic EM outbreaks.

  11. Evidence for large temperature fluctuations in quasar accretion disks from spectral variability

    SciTech Connect

    Ruan, John J.; Anderson, Scott F.; Agol, Eric; Dexter, Jason

    2014-03-10

    The well-known bluer-when-brighter trend observed in quasar variability is a signature of the complex processes in the accretion disk and can be a probe of the quasar variability mechanism. Using a sample of 604 variable quasars with repeat spectra in the Sloan Digital Sky Survey-I/II (SDSS), we construct difference spectra to investigate the physical causes of this bluer-when-brighter trend. The continuum of our composite difference spectrum is well fit by a power law, with a spectral index in excellent agreement with previous results. We measure the spectral variability relative to the underlying spectra of the quasars, which is independent of any extinction, and compare to model predictions. We show that our SDSS spectral variability results cannot be produced by global accretion rate fluctuations in a thin disk alone. However, we find that a simple model of an inhomogeneous disk with localized temperature fluctuations will produce power-law spectral variability over optical wavelengths. We show that the inhomogeneous disk will provide good fits to our observed spectral variability if the disk has large temperature fluctuations in many independently varying zones, in excellent agreement with independent constraints from quasar microlensing disk sizes, their strong UV spectral continuum, and single-band variability amplitudes. Our results provide an independent constraint on quasar variability models and add to the mounting evidence that quasar accretion disks have large localized temperature fluctuations.

  12. Evidence for Large Temperature Fluctuations in Quasar Accretion Disks from Spectral Variability

    NASA Astrophysics Data System (ADS)

    Ruan, John J.; Anderson, Scott F.; Dexter, Jason; Agol, Eric

    2014-03-01

    The well-known bluer-when-brighter trend observed in quasar variability is a signature of the complex processes in the accretion disk and can be a probe of the quasar variability mechanism. Using a sample of 604 variable quasars with repeat spectra in the Sloan Digital Sky Survey-I/II (SDSS), we construct difference spectra to investigate the physical causes of this bluer-when-brighter trend. The continuum of our composite difference spectrum is well fit by a power law, with a spectral index in excellent agreement with previous results. We measure the spectral variability relative to the underlying spectra of the quasars, which is independent of any extinction, and compare to model predictions. We show that our SDSS spectral variability results cannot be produced by global accretion rate fluctuations in a thin disk alone. However, we find that a simple model of an inhomogeneous disk with localized temperature fluctuations will produce power-law spectral variability over optical wavelengths. We show that the inhomogeneous disk will provide good fits to our observed spectral variability if the disk has large temperature fluctuations in many independently varying zones, in excellent agreement with independent constraints from quasar microlensing disk sizes, their strong UV spectral continuum, and single-band variability amplitudes. Our results provide an independent constraint on quasar variability models and add to the mounting evidence that quasar accretion disks have large localized temperature fluctuations.

  13. Two dimensional electron cyclotron emission imaging study of electron temperature profiles and fluctuations in Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Deng, Bihe

    An innovative plasma diagnostic technique, electron cyclotron emission imaging (ECEI), was successfully developed and implemented on the TEXT-U and RTP tokamaks for the study of plasma electron temperature profiles and fluctuations. Due to the high spatial and temporal resolution of this new diagnostic, plasma filamentation was observed during high power electron cyclotron resonance heating (ECRH) in TEXT-U, and was identified as multiple rotating magnetic islands. In RTP, under special plasma conditions, evidence for magnetic bubbling was first observed, which is characterized by the flattening of the electron temperature and pressure profiles over a small annular region of about 1-2 cm extent near the q = 2 surface. More important results arose from the detailed study of the broadband plasma turbulence in TEXT-U and RTP. With the first measurements of poloidal wavenumbers and dispersion relations, turbulent Te fluctuations in the confinement region of TEXT-U plasmas were identified as electron drift wave turbulence. The fluctuation amplitude is found to follow the mixing length scaling, and the fluctuation-induced conducted- heat flux can account for the observed anomalous energy transport in TEXT-U. In RTP, detailed ECEI study of broadband Te fluctuations has shown that many characteristics of the observed fluctuations are consistent with the predictions of toroidal ηi mode theory. These include the global dependence of the fluctuation frequency and amplitude on the plasma density and current. The measured isotope and impurity scalings quantitatively match the predictions of toroidal ηi mode theory. The ECEI measurements in combination with ECRH modification of T e profiles argue against the Te gradients serving as the driving force of the turbulence. With the detailed 2- D measurements of the fluctuation distribution over the plasma minor cross-section, large scale, coherent structures similar to the eigenmode structures predicted by toroidal ηi mode theory

  14. Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere

    NASA Astrophysics Data System (ADS)

    Podglajen, Aurélien; Hertzog, Albert; Plougonven, Riwal; Legras, Bernard

    2016-04-01

    Wave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum.

  15. Simultaneous Microwave Imaging System for Density and Temperature Fluctuation Measurements on TEXTOR

    SciTech Connect

    H. Park; E. Mazzucato; T. Munsat; C.W. Domier; M. Johnson; N.C. Luhmann, Jr.; J. Wang; Z. Xia; I.G.J. Classen; A.J.H. Donne; M.J. van de Pol

    2004-05-07

    Diagnostic systems for fluctuation measurements in plasmas have, of necessity, evolved from simple 1-D systems to multi-dimensional systems due to the complexity of the MHD and turbulence physics of plasmas illustrated by advanced numerical simulations. Using the recent significant advancements in millimeter wave imaging technology, Microwave Imaging Reflectometry (MIR) and Electron Cyclotron Emission Imaging (ECEI), simultaneously measuring density and temperature fluctuations, are developed for TEXTOR. The MIR system was installed on TEXTOR and the first experiment was performed in September, 2003. Subsequent MIR campaigns have yielded poloidally resolved spectra and assessments of poloidal velocity. The new 2-D ECE Imaging system (with a total of 128 channels), installed on TEXTOR in December, 2003, successfully captured a true 2-D images of Te fluctuations of m=1 oscillation (''sawteeth'') near the q {approx} 1 surface for the first time.

  16. Occupation number and fluctuations in the finite-temperature Bose-Hubbard model

    SciTech Connect

    Plimak, L.I.; Fleischhauer, M.; Olsen, M.K.

    2004-07-01

    We study the occupation numbers and number fluctuations of ultracold atoms in deep optical lattices for finite-temperatures within the Bose-Hubbard model. Simple analytical expressions for the mean occupation number and number fluctuations are obtained in the weak-hopping regime using an interpolation between results from different perturbation approaches in the Mott-insulator and superfluid phases. With this approach the magnitude of number fluctuations under a wide range of experimental conditions can be estimated and the properties of the finite-temperature phase diagram can be studied. These analytical results are compared to exact one-dimensional numerical calculations using a finite temperature variant of the density-matrix renormalization group (DMRG) method and found to have a high degree of accuracy. We find very good agreement, also in the crossover 'thermal' region. We also analyze the influence of finite temperature on the behavior of the system in the vicinity of the zero-temperature phase transition, in one, two, and three dimensions.

  17. Finite-temperature quantum fluctuations in two-dimensional Fermi superfluids

    NASA Astrophysics Data System (ADS)

    Bighin, G.; Salasnich, L.

    2016-01-01

    In two-dimensional systems with a continuous symmetry, the Mermin-Wagner-Hohenberg theorem precludes spontaneous symmetry breaking and condensation at finite temperature. The Berezinskii-Kosterlitz-Thouless critical temperature marks the transition from a superfluid phase characterized by quasicondensation and algebraic long-range order, to a normal phase in which vortex proliferation completely destroys superfluidity. As opposed to conventional off-diagonal long-range order typical of three-dimensional superfluid systems, algebraic long-range order is driven by quantum and thermal fluctuations strongly enhanced in reduced dimensionality. Motivated by this unique scenario and by the very recent experimental realization of trapped quasi-two-dimensional fermionic clouds, we include one-loop Gaussian fluctuations in the theoretical description of resonant Fermi superfluids in two dimensions demonstrating that first sound, second sound, and also critical temperature are strongly renormalized, away from their mean-field values. In particular, we prove that in the intermediate- and strong-coupling regimes, these quantities are radically different when Gaussian fluctuations are taken into account. Our one-loop theory shows good agreement with very recent experimental data on the Berezinskii-Kosterlitz-Thouless critical temperature [Phys. Rev. Lett. 115, 010401 (2015)], 10.1103/PhysRevLett.115.010401 and on the first sound velocity, giving predictions for the second sound as a function of interaction strength and temperature that are open for experimental verification.

  18. Coupled Nosé-Hoover equations of motion to implement a fluctuating heat-bath temperature

    NASA Astrophysics Data System (ADS)

    Fukuda, Ikuo; Moritsugu, Kei

    2016-03-01

    The Nosé-Hoover (NH) equation provides a universal and powerful computer simulation protocol to realize an equilibrium canonical temperature for a target physical system. Here we demonstrate a general formalism to couple such NH equations. We provide a coupled NH equation that is constructed by coupling the NH equation of a target physical system and the NH equation of a temperature system. Thus, in contrast to the conventional single NH equation, the heat-bath temperature is a dynamical variable. The temperature fluctuations are not ad hoc, but instead are generated by the newly defined temperature system, and the statistical distribution of the temperature is completely described with an arbitrarily given probability function. The current equations of motion thus describe the physical system that develops with a predistributed fluctuating temperature, which allows enhanced sampling of the physical system. Since the total system is governed by a prescribed distribution, the equilibrium of the physical system is also reconstructed by reweighting. We have formulated a scheme for specifically setting the distribution of the dynamical inverse temperature and demonstrate the statistical relationship between the dynamical and physical temperatures. The statistical features, dynamical properties, and sampling abilities of the current method are demonstrated via the distributions, trajectories, dynamical correlations, and free energy landscapes for both a model system and a biomolecular system. These results indicated that the current coupled NH scheme works well.

  19. Effects of fluctuating temperature on mortality, stress, and energy reserves of juvenile coho salmon

    SciTech Connect

    Thomas, R.E.; Gharrett, J.A.; Carls, M.G.; Rice, S.D.; Moles, A.; Korn, S.

    1986-01-01

    The effects of fluctuating diel temperature cycles on survival, growth, plasma cortisol and glucose concentrations, liver weight, and liver glycogen of juvenile coho salmon Oncorhynchus kisutch were determined. Temperature cycles (10-13/sup 0/, 9-15/sup 0/, 8-17/sup 0/, and 6.5-20/sup 0/C) were selected to stimulate observed temperatures in clear-cuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. LT50s (peak temperature within a cycle producing 50% mortality) were 28/sup 0/C for age-0 fish (350 mg) and 26/sup 0/ for age-II fish (22-g presmolts). Cyclic temperatures for 40 d, averaging 11/sup 0/C daily, did not influence growth of age-0 fish on any food ration as compared to controls held at a constant 11/sup 0/C. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5-20/sup 0/C cycle but not different in fish in 10-13/sup 0/ and 9-15/sup 0/ cycles or a constant 11/sup 0/C. These elevated concentrations may be indicators of long-term stress. Plasma cortisol concentrations were lower in starved fish than in fed fish at all temperature regimes; however, fluctuating temperature did not enhance starvation effects on cortisol levels. Diel temperature cycles did not affect liver weights or liver glycogen concentrations.

  20. Concentration fluctuations in miscible polymer blends: Influence of temperature and chain rigidity

    SciTech Connect

    Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.

    2014-05-21

    In contrast to binary mixtures of small molecule fluids, homogeneous polymer blends exhibit relatively large concentration fluctuations that can strongly affect the transport properties of these complex fluids over wide ranges of temperatures and compositions. The spatial scale and intensity of these compositional fluctuations are studied by applying Kirkwood-Buff theory to model blends of linear semiflexible polymer chains with upper critical solution temperatures. The requisite quantities for determining the Kirkwood-Buff integrals are generated from the lattice cluster theory for the thermodynamics of the blend and from the generalization of the random phase approximation to compressible polymer mixtures. We explore how the scale and intensity of composition fluctuations in binary blends vary with the reduced temperature τ ≡ (T − T{sub c})/T (where T{sub c} is the critical temperature) and with the asymmetry in the rigidities of the components. Knowledge of these variations is crucial for understanding the dynamics of materials fabricated from polymer blends, and evidence supporting these expectations is briefly discussed.

  1. The dynamics of mid-ocean ridge hydrothermal systems: Splitting plumes and fluctuating vent temperatures

    NASA Astrophysics Data System (ADS)

    Coumou, Dim; Driesner, Thomas; Geiger, Sebastian; Heinrich, Christoph A.; Matthäi, Stephan

    2006-05-01

    We present new, accurate numerical simulations of 2D models resembling hydrothermal systems active in the high-permeability axial plane of mid-ocean ridges and show that fluid flow patterns are much more irregular and convection much more unstable than reported in previous simulation studies. First, we observe the splitting of hot, rising plumes. This phenomenon is caused by the viscous instability at the interface between hot, low-viscosity fluid and cold, high-viscosity fluid. This process, known as Taylor-Saffman fingering could potentially explain the sudden extinguishing of black smokers. Second, our simulations show that for relatively moderate permeabilities, convection is unsteady resulting in transiently varying vent temperatures. The amplitude of these fluctuations typically is 40 °C with a period of decades or less, depending on the permeability. Although externally imposed events such as dike injections are possible mechanisms, they are not required to explain temperature variations observed in natural systems. Our results also offer a simple explanation of how seismic events cause fluctuating temperatures: Earthquake-induced permeability-increase shifts the hydrothermal system to the unsteady regime with accompanying fluctuating vent temperatures. We demonstrate that realistic modelling of these high-Rayleigh number convection systems does not only require the use of real fluid properties, but also the use of higher order numerical methods capable of handling high-resolution meshes. Less accurate numerical solutions smear out sharp advection fronts and thereby artificially stabilize the system.

  2. Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates.

    PubMed

    Convey, Peter; Abbandonato, Holly; Bergan, Frode; Beumer, Larissa Teresa; Biersma, Elisabeth Machteld; Bråthen, Vegard Sandøy; D'Imperio, Ludovica; Jensen, Christina Kjellerup; Nilsen, Solveig; Paquin, Karolina; Stenkewitz, Ute; Svoen, Mildrid Elvik; Winkler, Judith; Müller, Eike; Coulson, Stephen James

    2015-12-01

    The extreme polar environment creates challenges for its resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditions experienced at microhabitat level, few studies have explicitly set out to link field conditions experienced by natural multispecies communities with the more detailed laboratory ecophysiological studies of a small number of 'representative' species. This is particularly the case during winter, when snow cover may insulate terrestrial habitats from extreme air temperature fluctuations. Further, climate projections suggest large changes in precipitation will occur in the polar regions, with the greatest changes expected during the winter period and, hence, implications for the insulation of overwintering microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow, Shallow Snow (30 cm) and Deep Snow (120 cm). Air temperatures during the winter period fluctuated frequently between +3 and -24 °C, and the No Snow soil temperatures reflected this variation closely, with the extreme minimum being slightly lower. Under 30 cm of snow, soil temperatures varied less and did not decrease below -12 °C. Those under deep snow were even more stable and did not decline below -2 °C. Despite these striking differences in winter thermal regimes, there were no clear differences in survival of the invertebrate fauna between treatments, including oribatid, prostigmatid and mesostigmatid mites, Araneae, Collembola, Nematocera larvae or Coleoptera. This indicates widespread tolerance, previously undocumented for the Araneae, Nematocera or Coleoptera, of

  3. Temperature fluctuations and infrared emission from dust particles in a hot gas

    NASA Technical Reports Server (NTRS)

    Dwek, E.

    1986-01-01

    In this paper, the effect of temperature fluctuations in very small dust particles caused by electronic collisions with an ambient hot gas, is calculated. The dust-temperature distribution differs strongly from that derived on the basis of equilibrium heating models, peaking at lower temperatures in the stochastically heated case. The resulting infrared spectrum is broadened at short wavelengths, giving much more emission than expected from equilibrium calculations, and at long wavelengths exhibits a lower color temperature. Dust-temperature fluctuations are thus expected to play an important role in determining the infrared spectrum of dusty, X-ray-emitting plasmas. A power-law distribution of grain radii extended to very small grain sizes will have a distinct infrared spectrum characterized by an infrared excess at the Wien side of the spectrum. This excess emission represents a high-temperature component in the spectrum, resulting from the stochastic heating of very small dust particles. Its magnitude depends on the grain-size distribution and the temperature and density of the ambient hot gas. This excess emission may be observed by IRAS in supernova remnants and rich clusters of galaxies.

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

    USGS Publications Warehouse

    Moffitt, Christine M.; James, Christopher A.

    2012-01-01

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

  5. An Experimental Study of the Statistics of Temperature Fluctuations in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Costa Frola, Elena; Mazzino, Andrea; Cassola, Federico; Mortarini, Luca; Ferrero, Enrico

    2014-01-01

    A statistical characterization for two-point temperature fluctuations in the planetary boundary layer (PBL) is analyzed and its implications on the long-standing closure problem discussed. Despite the non-triviality of the dynamics of temperature fluctuations, our analysis supports the idea that the most relevant statistical properties can be captured solely in terms of two scaling exponents. They turned out to be weakly dependent on the stability properties of the PBL. Its statistics have been investigated by collecting data from a field experiment carried out in the urban area of Turin (Italy) from January 2007 to March 2008. Our results confirm those from a large-eddy simulation (LES) analysis carried out for the convective PBL with different level of convection. We extend the scenario to the stable PBL, a regime much more difficult to simulate when exploiting LES.

  6. Measurements of density, temperature, and their fluctuations in turbulent supersonic flow using UV laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Fletcher, Douglas G.; Mckenzie, R. L.

    1992-01-01

    Nonintrusive measurements of density, temperature, and their turbulent fluctuation levels were obtained in the boundary layer of an unseeded, Mach 2 wind tunnel flow. The spectroscopic technique that was used to make the measurements is based on the combination of laser-induced oxygen fluorescence and Raman scattering by oxygen and nitrogen from the same laser pulse. Results from this demonstration experiment are compared with previous measurements obtained in the same facility using conventional probes and an earlier spectroscopic technique. Densities and temperatures measured with the current technique agree with the previous surveys to within 3 percent and 2 percent, respectively. The fluctuation amplitudes for both variables agree with the measurements obtained using the earlier spectroscopic technique and show evidence of an unsteady, weak shock wave that perturbs the boundary layer.

  7. Measurements of temperature, density, pressure, and their fluctuations in supersonic turbulence using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Gross, K. P.; Mckenzie, R. L.; Logan, P.

    1987-01-01

    A laser-induced fluorescence method has been developed that provides simultaneous measurements of temperature, density, and their fluctuations owing to turbulence in unheated compressible flows. Pressure and its fluctuations are also deduced using the equation of state. Fluorescence is induced in nitric oxide that has been seeded into a nitrogen flow in concentrations of 100 ppm. Measurements are obtained from each laser pulse, with a spatial resolution of 1 mm and a temporal resolution of 125 ns. The method was applied to a supersonic, turbulent, boundary-layer flow with a free-stream Mach number of 2. For stream conditions in the range from 150-300 K and 0.3-1 atm, temperature is measured with an uncertainty of approximately 1 percent rms, while density and pressure uncertainties are approximately 2 percent rms.

  8. Characterizing the effect of temperature fluctuation on the incidence of malaria: an epidemiological study in south-west China using the varying coefficient distributed lag non-linear model

    PubMed Central

    2014-01-01

    Background Malaria transmission is strongly determined by the environmental temperature and the environment is rarely constant. Therefore, mosquitoes and parasites are not only exposed to the mean temperature, but also to daily temperature variation. Recently, both theoretical and laboratory work has shown, in addition to mean temperatures, daily fluctuations in temperature can affect essential mosquito and parasite traits that determine malaria transmission intensity. However, so far there is no epidemiological evidence at the population level to this problem. Methods Thirty counties in southwest China were selected, and corresponding weekly malaria cases and weekly meteorological variables were collected from 2004 to 2009. Particularly, maximum, mean and minimum temperatures were collected. The daily temperature fluctuation was measured by the diurnal temperature range (DTR), the difference between the maximum and minimum temperature. The distributed lag non-linear model (MDLNM) was used to study the correlation between weekly malaria incidences and weekly mean temperatures, and the correlation pattern was allowed to vary over different levels of daily temperature fluctuations. Results The overall non-linear patterns for mean temperatures are distinct across different levels of DTR. When under cooler temperature conditions, the larger mean temperature effect on malaria incidences is found in the groups of higher DTR, suggesting that large daily temperature fluctuations act to speed up the malaria incidence in cooler environmental conditions. In contrast, high daily fluctuations under warmer conditions will lead to slow down the mean temperature effect. Furthermore, in the group of highest DTR, 24-25°C or 21-23°C are detected as the optimal temperature for the malaria transmission. Conclusion The environment is rarely constant, and the result highlights the need to consider temperature fluctuations as well as mean temperatures, when trying to understand or

  9. Fiberoptic probe for measuring high frequency temperature fluctuations in combustion gases

    SciTech Connect

    Dils, R.R.; Tichenor, D.A.

    1984-02-01

    A new fiberoptic probe for measuring high frequency gas-temperature fluctuations is described. The fiberoptic probe is an optical pyrometer in which the thermal radiation is transmitted through an optical fiber. The key element in the device is a high temperature optical fiber made of single-crystal alumina (sapphire), which remains transparent and nonemitting in the optical and near infrared at temperatures up to its melting point, 2345 K. On one end of the fiber a thin film of platinum or other high temperature alloy serves as a thermal radiator. The other end of the high temperature fiber is connected to a photodetector through a conventional fused silica fiber. In operation, thermal radiation from the metallic thin film is collected by the high-temperature fiber and transmitted through the conventional optical fiber to a detector assembly. The radiation is then transmitted through a band pass filter, and the intensity is measured using a photodetector. The system is calibrated to account for the emissivity of the thin-film tip, the responsivity of the detector and the gain of the amplifier. The frequency response of the fiberoptic probe is inherently superior to that of fine-wire thermocouples, because the output of the fiberoptic device depends only on the surface temperature of the probe. The output of a thermocouple depends on the internal temperature of the wire. As a result, the transfer function that relates gas temperature to probe temperature decreases 3 db per octave at high frequency rather than 6 db per octave characteristic of thermocouples. Experimental results demonstrate the capability of measuring temperature fluctuations up to 14 KHz in combustor exhaust gases.

  10. The Impact of Fluctuations in Precipitation and Temperature on the Seasonal Snowpack

    NASA Astrophysics Data System (ADS)

    Woods, R. A.

    2015-12-01

    The development and melting of the seasonal snowpack depends on complex interactions among climate elements. Previous work (Woods 2009, Adv. Wat. Res.) showed how the typical seasonal variation of temperature and precipitation rate influence snowpack development. Results were expressed in terms of three dimensionless variables for: seasonal temperature regime; seasonality of precipitation; and depth of the snowpack relative to the energy available for melting. However, that theory does not take account of sub-seasonal fluctuations in temperature and precipitation, and as a consequence, makes poor predictions of snow storage in some climates. Here we write a stochastic differential equation for snow storage, and then derive an equation for time variation of the probability distribution (pdf) of snow water equivalent (SWE). This provides a detailed but compact understanding of how temperature and precipitation interact to influence the seasonal accumulation and melt of snow. From this equation, we can estimate statistics such as the mean and standard deviation of SWE on any day of the year, and the mean residence time of snow, and see how they are related to climate characteristics. To develop the equation, we first describe temperature and precipitation with 4 parameters each, defining the mean, seasonal amplitude, seasonal timing, and sub-seasonal fluctuations. To simulate the response of the snowpack to climate, we use a temperature index model with two parameters: a degree-day melt factor and a threshold temperature. By writing the equation for snow storage in dimensionless form, we reduce the problem to five dimensionless parameters, three of them the same as found by Woods (2009), plus one each for the sub-seasonal fluctuations in precipitation and temperature. In the special case of no fluctuations in temperature and precipitation, the new equation reduces to the deterministic case of Woods (2009). We verify by Monte Carlo simulation that that the probability

  11. The Impact of Fluctuations in Precipitation and Temperature on the Seasonal Snowpack

    NASA Astrophysics Data System (ADS)

    Woods, Ross

    2016-04-01

    The development and melting of the seasonal snowpack depends on complex interactions among climate elements. Previous work (Woods 2009, Adv. Wat. Res.) showed how the typical seasonal variation of temperature and precipitation rate influence snowpack development. Results were expressed in terms of three dimensionless variables for: seasonal temperature regime; seasonality of precipitation; and depth of the snowpack relative to the energy available for melting. However, that theory does not take account of sub-seasonal fluctuations in temperature and precipitation, and as a consequence, makes poor predictions of snow storage in some climates. Here we write a stochastic differential equation for point-scale snow water equivalent (SWE), and then derive an equation for time variation of the probability distribution (pdf) of SWE. This provides a detailed but compact understanding of how temperature and precipitation interact to influence the seasonal accumulation and melt of snow. From this equation, we can estimate statistics such as the mean and standard deviation of SWE on any day of the year, and the mean residence time of snow, and see how they are related to climate characteristics. To develop the equation, we first describe temperature and precipitation with 4 parameters each, defining the mean, seasonal amplitude, seasonal timing, and sub-seasonal fluctuations. To simulate the response of the snowpack to climate, we use a temperature index model with two parameters: a degree-day melt factor and a threshold temperature. By writing the equation for snow storage in dimensionless form, we reduce the problem to five dimensionless parameters, three of them the same as found by Woods (2009), plus one each for the sub-seasonal fluctuations in precipitation and temperature. In the special case of no fluctuations in temperature and precipitation, the new equation reduces to the deterministic case of Woods (2009). We verify by Monte Carlo simulation that that the

  12. Thermal fluctuations of haemoglobin from different species: adaptation to temperature via conformational dynamics.

    PubMed

    Stadler, A M; Garvey, C J; Bocahut, A; Sacquin-Mora, S; Digel, I; Schneider, G J; Natali, F; Artmann, G M; Zaccai, G

    2012-11-01

    Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the β-subunits. PMID:22696485

  13. Trends in temperature extremes in association with weather-intraseasonal fluctuations in eastern China

    NASA Astrophysics Data System (ADS)

    Qian, Cheng; Yan, Zhongwei; Wu, Zhaohua; Fu, Congbin; Tu, Kai

    2011-03-01

    Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, warm nights and cold nights) with respect to a modulated annual cycle (MAC), and those associated exclusively with weather-intraseasonal fluctuations (WIF) in eastern China were investigated based on an updated homogenized daily maximum and minimum temperature dataset for 1960-2008. The Ensemble Empirical Mode Decomposition (EEMD) method was used to isolate the WIF, MAC, and longer-term components from the temperature series. The annual, winter and summer occurrences of warm (cold) nights were found to have increased (decreased) significantly almost everywhere, while those of warm (cold) days have increased (decreased) in northern China (north of 40°N). However, the four temperature extremes associated exclusively with WIF for winter have decreased almost everywhere, while those for summer have decreased in the north but increased in the south. These characteristics agree with changes in the amplitude of WIF. In particular, winter WIF of maximum temperature tended to weaken almost everywhere, especially in eastern coastal areas (by 10%-20%); summer WIF tended to intensify in southern China by 10%-20%. It is notable that in northern China, the occurrence of warm days has increased, even where that associated with WIF has decreased significantly. This suggests that the recent increasing frequency of warm extremes is due to a considerable rise in the mean temperature level, which surpasses the effect of the weakening weather fluctuations in northern China.

  14. Rapid fluctuations of the air and surface temperature in the city of Bucharest (Romania)

    NASA Astrophysics Data System (ADS)

    Cheval, Sorin; Dumitrescu, Alexandru; Hustiu, Mihaita-Cristinel

    2016-04-01

    Urban areas derive significant changes of the ambient temperature generating specific challenges for society and infrastructure. Extreme temperature events, heat and cold waves affect the human comfort, increase the health risk, and require specific building regulations and emergency preparedness, strongly related to the magnitude and frequency of the thermal hazards. Rapid changes of the temperature put a particular stress for the urban settlements, and the topic has been approached constantly in the scientific literature. Due to its geographical position in a plain area with a temperate climate and noticeable continental influence, the city of Bucharest (Romania) deals with high seasonal and daily temperature variations. However, rapid fluctuations also occur at sub-daily scale caused by cold or warm air advections or by very local effects (e.g. radiative heat exchange, local precipitation). For example, in the area of Bucharest, the cold fronts of the warm season may trigger temperature decreasing up to 10-15 centigrades / hour, while warm advections lead to increasing of 1-2 centigrades / hour. This study focuses on the hourly and sub-hourly temperature variations over the period November 2014 - February 2016, using air temperature data collected from urban sensors and meteorological stations of the national network, and land surface temperature data obtained from satellite remote sensing. The analysis returns different statistics, such as magnitude, intensity, frequency, simultaneous occurrence and areal coverage of the rapid temperature fluctuations. Furthermore, the generating factors for each case study are assessed, and the results are used to define some preliminary patterns and enhance the urban temperature forecast at fine scale. The study was funded by the Romanian Programme Partnership in Priority Domains, PN - II - PCCA - 2013 - 4 - 0509 - Reducing UHI effects to improve urban comfort and balance energy consumption in Bucharest (REDBHI).

  15. Temperature dependence of universal fluctuations in the two-dimensional harmonic XY model

    NASA Astrophysics Data System (ADS)

    Palma, G.

    2006-04-01

    We compute exact analytical expressions for the skewness and kurtosis in the two-dimensional harmonic XY model. These quantities correspond to the third and fourth normalized moments of the probability density function (PDF) of the magnetization of the model. From their behavior, we conclude that they depend explicitly on the system temperature even in the thermodynamic limit, and hence the PDF itself must depend on it. Our results correct the hypothesis called universal fluctuations, they confirm and extend previous results which showed a T dependence of the PDF, including perturbative expansions within the XY model up to first order in temperature.

  16. Effect of gravity wave temperature fluctuations on homogeneous ice nucleation in the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Dinh, T.; Podglajen, A.; Hertzog, A.; Legras, B.; Plougonven, R.

    2016-01-01

    The impact of high-frequency fluctuations of temperature on homogeneous nucleation of ice crystals in the vicinity of the tropical tropopause is investigated using a bin microphysics scheme for air parcels. The imposed temperature fluctuations come from measurements during isopycnic balloon flights near the tropical tropopause. The balloons collected data at high frequency, guaranteeing that gravity wave signals are well resolved.With the observed temperature time series, the numerical simulations with homogeneous freezing show a full range of ice number concentration (INC) as previously observed in the tropical upper troposphere. In particular, a low INC may be obtained if the gravity wave perturbations produce a non-persistent cooling rate (even with large magnitude) such that the absolute change in temperature remains small during nucleation. This result is explained analytically by a dependence of the INC on the absolute drop in temperature (and not on the cooling rate). This work suggests that homogeneous ice nucleation is not necessarily inconsistent with observations of low INCs.

  17. Thermal analysis of optical reference cavities for low sensitivity to environmental temperature fluctuations.

    PubMed

    Dai, Xiaojiao; Jiang, Yanyi; Hang, Chao; Bi, Zhiyi; Ma, Longsheng

    2015-02-23

    The temperature stability of optical reference cavities is significant in state-of-the-art ultra-stable narrow-linewidth laser systems. In this paper, the thermal time constant and thermal sensitivity of reference cavities are analyzed when reference cavities respond to environmental perturbations via heat transfer of thermal conduction and thermal radiation separately. The analysis as well as simulation results indicate that a reference cavity enclosed in multiple layers of thermal shields with larger mass, higher thermal capacity and lower emissivity is found to have a larger thermal time constant and thus a smaller sensitivity to environmental temperature perturbations. The design of thermal shields for reference cavities may vary according to experimentally achievable temperature stability and the coefficient of thermal expansion of reference cavities. A temperature fluctuation-induced length instability of reference cavities as low as 6 × 10(-16) on a day timescale can be achieved if a two-layer thermal shield is inserted between a cavity with the coefficient of thermal expansion of 1 × 10(-10) /K and an outer vacuum chamber with temperature fluctuation amplitude of 1 mK and period of 24 hours. PMID:25836547

  18. Limits to the thermal tolerance of corals adapted to a highly fluctuating, naturally extreme temperature environment

    PubMed Central

    Schoepf, Verena; Stat, Michael; Falter, James L.; McCulloch, Malcolm T.

    2015-01-01

    Naturally extreme temperature environments can provide important insights into the processes underlying coral thermal tolerance. We determined the bleaching resistance of Acropora aspera and Dipsastraea sp. from both intertidal and subtidal environments of the naturally extreme Kimberley region in northwest Australia. Here tides of up to 10 m can cause aerial exposure of corals and temperatures as high as 37 °C that fluctuate daily by up to 7 °C. Control corals were maintained at ambient nearshore temperatures which varied diurnally by 4-5 °C, while treatment corals were exposed to similar diurnal variations and heat stress corresponding to ~20 degree heating days. All corals hosted Symbiodinium clade C independent of treatment or origin. Detailed physiological measurements showed that these corals were nevertheless highly sensitive to daily average temperatures exceeding their maximum monthly mean of ~31 °C by 1 °C for only a few days. Generally, Acropora was much more susceptible to bleaching than Dipsastraea and experienced up to 75% mortality, whereas all Dipsastraea survived. Furthermore, subtidal corals, which originated from a more thermally stable environment compared to intertidal corals, were more susceptible to bleaching. This demonstrates that while highly fluctuating temperatures enhance coral resilience to thermal stress, they do not provide immunity to extreme heat stress events. PMID:26627576

  19. Limits to the thermal tolerance of corals adapted to a highly fluctuating, naturally extreme temperature environment.

    PubMed

    Schoepf, Verena; Stat, Michael; Falter, James L; McCulloch, Malcolm T

    2015-01-01

    Naturally extreme temperature environments can provide important insights into the processes underlying coral thermal tolerance. We determined the bleaching resistance of Acropora aspera and Dipsastraea sp. from both intertidal and subtidal environments of the naturally extreme Kimberley region in northwest Australia. Here tides of up to 10 m can cause aerial exposure of corals and temperatures as high as 37 °C that fluctuate daily by up to 7 °C. Control corals were maintained at ambient nearshore temperatures which varied diurnally by 4-5 °C, while treatment corals were exposed to similar diurnal variations and heat stress corresponding to ~20 degree heating days. All corals hosted Symbiodinium clade C independent of treatment or origin. Detailed physiological measurements showed that these corals were nevertheless highly sensitive to daily average temperatures exceeding their maximum monthly mean of ~31 °C by 1 °C for only a few days. Generally, Acropora was much more susceptible to bleaching than Dipsastraea and experienced up to 75% mortality, whereas all Dipsastraea survived. Furthermore, subtidal corals, which originated from a more thermally stable environment compared to intertidal corals, were more susceptible to bleaching. This demonstrates that while highly fluctuating temperatures enhance coral resilience to thermal stress, they do not provide immunity to extreme heat stress events. PMID:26627576

  20. Limits to the thermal tolerance of corals adapted to a highly fluctuating, naturally extreme temperature environment

    NASA Astrophysics Data System (ADS)

    Schoepf, Verena; Stat, Michael; Falter, James L.; McCulloch, Malcolm T.

    2015-12-01

    Naturally extreme temperature environments can provide important insights into the processes underlying coral thermal tolerance. We determined the bleaching resistance of Acropora aspera and Dipsastraea sp. from both intertidal and subtidal environments of the naturally extreme Kimberley region in northwest Australia. Here tides of up to 10 m can cause aerial exposure of corals and temperatures as high as 37 °C that fluctuate daily by up to 7 °C. Control corals were maintained at ambient nearshore temperatures which varied diurnally by 4-5 °C, while treatment corals were exposed to similar diurnal variations and heat stress corresponding to ~20 degree heating days. All corals hosted Symbiodinium clade C independent of treatment or origin. Detailed physiological measurements showed that these corals were nevertheless highly sensitive to daily average temperatures exceeding their maximum monthly mean of ~31 °C by 1 °C for only a few days. Generally, Acropora was much more susceptible to bleaching than Dipsastraea and experienced up to 75% mortality, whereas all Dipsastraea survived. Furthermore, subtidal corals, which originated from a more thermally stable environment compared to intertidal corals, were more susceptible to bleaching. This demonstrates that while highly fluctuating temperatures enhance coral resilience to thermal stress, they do not provide immunity to extreme heat stress events.

  1. Molecular Rayleigh Scattering Diagnostic for Measurement of High Frequency Temperature Fluctuations

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.

    2005-01-01

    A novel technique for measurement of high frequency temperature fluctuations in unseeded gas flows using molecular Rayleigh scattering is investigated. The spectrum of laser light scattered from molecules in a gas flow is resolved using a Fabry-Perot interferometer. The width of the spectral peak is broadened by thermal motion of the molecules and hence is related to gas temperature. The interference fringe pattern containing spectral information is divided into four concentric regions using a series of mirrors angled with respect to one another. Light from each of these regions is directed towards photomultiplier tubes and sampled at 10 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows measurement of gas temperature. Independently monitoring the total scattered intensity provides a measure of gas density. This technique also has the potential to simultaneously measure a single component of flow velocity by monitoring the spectral peak location. Measurements of gas temperature and density are demonstrated using a low speed heated air jet surrounded by an unheated air co-flow. Mean values of temperature and density are shown for radial scans across the jet flow at a fixed axial distance from the jet exit plane. Power spectra of temperature and density fluctuations at several locations in the jet are also shown. The instantaneous measurements have fairly high uncertainty; however, long data records provide highly accurate statistically quantities, which include power spectra. Mean temperatures are compared with thermocouple measurements as well as the temperatures derived from independent density measurements. The accuracy for mean temperature measurements was +/- 7 K.

  2. Investigation of Temperature Fluctuations Caused by Steam-Water Two-Phase Flow in Pressurizer Spray Piping

    NASA Astrophysics Data System (ADS)

    Miyoshi, Koji; Nakamura, Akira; Takenaka, Nobuyuki; Oumaya, Toru

    In a PWR plant, a steam-water two-phase flow may possibly exist in the pressurizer spray pipe under a normal operating condition since the flow rate of the spray water is not sufficient to fill the horizontal section of the pipe completely. Initiation of high cycle fatigue cracks is suspected to occur under such thermally stratified two phase flow conditions due to cyclic thermal stress fluctuations caused by oscillations of the water surface. Such oscillations cannot be detected by the measurement of temperature on outer surface of the pipe. In order to clarify the flow and thermal conditions in the pressurizer spray pipe and assess their impact on the pipe structure, an experiment was conducted for a steam-water flow at a low flow rate using a mock-up pressurizer spray pipe. The maximum temperature fluctuation of about 0.2 times of the steam-water temperature difference was observed at the inner wall around water surface in the test section. Visualization tests were conducted to investigate the temperature fluctuation phenomena. It was shown that the fluid temperature fluctuations were not caused by the waves on the water surface, but were caused by liquid temperature fluctuations in water layer below the interface. The influence of small amount of non-condensable gas dissolved in the reactor coolant on the liquid temperature fluctuation phenomena was investigated by injecting air into the experimental loop. The air injection attenuated the liquid temperature fluctuations in the water layer since the condensation was suppressed by the non- condensable gas. It is not expected that wall temperature fluctuation in the actual PWR plant may exceed the temperature equivalent to the fatigue limit stress amplitude when it is assumed to be proportional to the steam-water temperature difference.

  3. Density fluctuations and radiated noise for a high-temperature supersonic jet

    NASA Technical Reports Server (NTRS)

    Parthasarathy, S. P.; Massier, P. F.; Cuffel, R. F.; Radbill, J. R.

    1975-01-01

    Experimental data on density fluctuations were obtained by the laser Schlieren method in a supersonic jet which at the nozzle exit had a Mach number of 1.43 and a stagnation temperature of about 1090 K. The jet emerged into the ambient atmosphere in an anechoic chamber, correctly expanded from a nozzle which had an exit diameter of 10.8 cm. Using the information on the density fluctuations and the mean shear obtained by probes, the autocorrelation of the radiated noise was calculated by a theory that is suitable for Mach wave emission. This theory is a modification of that developed by Ffowcs Williams and Maidanik (1965). The calculated noise field agrees well with that obtained by using microphones outside the jet.

  4. ECE Temperature Fluctuations associated with EDA H-Mode discharges in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Phillips, P. E.; Lynn, A. G.

    2006-10-01

    Alcator C-Mod exhibits an ELM-free H-mode with ``enhanced,,lpha'' emission accompanied by a quasi-coherent mode (QCM) edge relaxation mechanism. This steady state H-mode lowers the peak heat load to the diverters which is advantageous for reactor operations. A high-resolution heterodyne electron-cyclotron-emission (ECE) radiometer with 32 channels (δR˜7mm) and a bandwidth up to 1MHz covering the full radius of C-Mod has observed spatial resolved temperature fluctuations that are highly correlated with the edge QCM mode. The QCM mode is also directly observed by the edge ECE channels though the changes in optical depth due to the large density fluctuations in the QCM (˜30%). Details of these measurements will be presented in this poster.

  5. Low-temperature magnetic fluctuations in the Kondo insulator SmB6

    NASA Astrophysics Data System (ADS)

    Biswas, P. K.; Salman, Z.; Neupert, T.; Morenzoni, E.; Pomjakushina, E.; von Rohr, F.; Conder, K.; Balakrishnan, G.; Hatnean, M. Ciomaga; Lees, M. R.; Paul, D. McK.; Schilling, A.; Baines, C.; Luetkens, H.; Khasanov, R.; Amato, A.

    2014-04-01

    We present the results of a systematic investigation of the magnetic properties of the three-dimensional Kondo topological insulator SmB6 using magnetization and muon-spin relaxation/rotation (μSR) measurements. The μSR measurements exhibit magnetic field fluctuations in SmB6 below ˜15 K due to electronic moments present in the system. However, no evidence for magnetic ordering is found down to 19 mK. The observed magnetism in SmB6 is homogeneous in nature throughout the full volume of the sample. Bulk magnetization measurements on the same sample show consistent behavior. The agreement between μSR, magnetization, and NMR results strongly indicate the appearance of intrinsic bulk magnetic in-gap states associated with fluctuating magnetic fields in SmB6 at low temperature.

  6. New correlation electron cyclotron emission temperature fluctuation diagnositc for Alcator C-mod

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A. E.; Irby, J.; Peebles, W. A.; Nguyen, X.

    2011-10-01

    A new Correlation Electron Cyclotron Emission (CECE) system for the measurement of electron temperature fluctuation is planned for Alcator C-mod. The multi-channel CECE radiometer will use the spectral decorrelation technique to measure turbulent fluctuations that are below thermal noise levels. The design of the optics and Intermediate Frequency (IF) section was constrained using predictions from nonlinear gyrokinetic turbulence simulations using the GYRO code. A Gaussian optical system will provide high poloidal spatial resolution (ω0 < 0 . 5 cm) needed to measure long-wavelength core turbulence at C-Mod, kθρs < 0 . 5 . The IF section will employ tunable band-pass filters to optimize turbulence measurements. We will present details of the new CECE system design and laboratory tests of the optics and IF section.

  7. Influence of melt-temperature fluctuations on striation formation in large-scale Czochralski Si growth systems

    NASA Astrophysics Data System (ADS)

    Kanda, Tadashi; Hourai, Masataka; Miki, Shinichiro; Shigematsu, Tatsuhiko; Tomokage, Hajime; Miyano, Takaya; Morita, Hiroshi; Shintani, Akira

    1996-09-01

    The effects of melt-temperature fluctuations on growth striations in crystals grown in a commercial-scale growth system were studied by an analysis of the fast-Fourier-transform (FFT) method applied to the melt-temperature fluctuations and to the growth striations as evaluated by X-ray topography and spreading-resistance (SR) methods. The period of the growth striations observed in crystals corresponded exactly to that of temperature fluctuations in the melt; however, the amplitude of these growth striations decreased when temperature fluctuations with a constant amplitude occurred rapidly. This phenomenon results from a delay in the response of the microscopic growth rate to rapid temperature fluctuations. The amplitude of melt-temperature fluctuations and the peak height of the FFT power spectra were observed to decrease in the radial direction toward the crystal center, and this trend was also observed for growth striations. It was concluded that temporal thermal fluctuations caused by melt convection are preserved in growth striations for crystals grown in large growth systems.

  8. Spatio-statistical analysis of temperature fluctuation using Mann-Kendall and Sen's slope approach

    NASA Astrophysics Data System (ADS)

    Atta-ur-Rahman; Dawood, Muhammad

    2016-04-01

    This article deals with the spatio-statistical analysis of temperature trend using Mann-Kendall trend model (MKTM) and Sen's slope estimator (SSE) in the eastern Hindu Kush, north Pakistan. The climate change has a strong relationship with the trend in temperature and resultant changes in rainfall pattern and river discharge. In the present study, temperature is selected as a meteorological parameter for trend analysis and slope magnitude. In order to achieve objectives of the study, temperature data was collected from Pakistan Meteorological Department for all the seven meteorological stations that falls in the eastern Hindu Kush region. The temperature data were analysed and simulated using MKTM, whereas for the determination of temperature trend and slope magnitude SSE method have been applied to exhibit the type of fluctuations. The analysis reveals that a positive (increasing) trend in mean maximum temperature has been detected for Chitral, Dir and Saidu Sharif met stations, whereas, negative (decreasing) trend in mean minimum temperature has been recorded for met station Saidu Sharif and Timergara. The analysis further reveals that the concern variation in temperature trend and slope magnitude is attributed to climate change phenomenon in the region.

  9. Rayleigh Scattering Diagnostic for Measurement of Temperature, Velocity, and Density Fluctuation Spectra

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.; Sung, Chih-Jen; Panda, Jayanta

    2006-01-01

    A molecular Rayleigh scattering technique is developed to measure dynamic gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 10 kHz. A high power CW laser beam is focused at a point in a heated air jet plume and Rayleigh scattered light is collected and spectrally resolved. The spectrum of the light, which contains information about the temperature, velocity, and density of the flow, is analyzed using a Fabry-Perot interferometer. The circular interference fringe pattern is divided into four concentric regions and sampled at 1 and 10 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows for measurement of gas temperature and velocity. Independently monitoring the total scattered light intensity provides a measure of gas density. Power spectral density calculations of temperature, velocity, and density fluctuations, as well as mean and fluctuating quantities are demonstrated for various radial locations in the jet flow at a fixed axial distance from the jet exit plane. Results are compared with constant current anemometry and pitot probe measurements at the same locations.

  10. Quasi-linear theory of electron density and temperature fluctuations with application to MHD generators and MPD arc thrusters

    NASA Technical Reports Server (NTRS)

    Smith, M.

    1972-01-01

    Fluctuations in electron density and temperature coupled through Ohm's law are studied for an ionizable medium. The nonlinear effects are considered in the limit of a third order quasi-linear treatment. Equations are derived for the amplitude of the fluctuation. Conditions under which a steady state can exist in the presence of the fluctuation are examined and effective transport properties are determined. A comparison is made to previously considered second order theory. The effect of third order terms indicates the possibility of fluctuations existing in regions predicted stable by previous analysis.

  11. Quasi-linear theory of electron density and temperature fluctuations with application to MHD generators and MPD arc thrusters.

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1972-01-01

    Fluctuations in electron density and temperature coupled through Ohm's law are studied for an ionizable medium. The nonlinear effects are considered in the limit of a third order quasi-linear treatment. Equations are derived for the amplitude of the fluctuation. Conditions under which a steady state can exist in the presence of the fluctuation are examined and effective transport properties are determined. A comparison is made to previously considered second order theory. The effect of third order terms indicates the possibility of fluctuations existing in regions predicted stable by previous analysis.

  12. Assay conditions in laboratory experiments: is the use of constant rather than fluctuating temperatures justified when investigating temperature-induced plasticity?

    PubMed

    Fischer, Klaus; Kölzow, Nadine; Höltje, Henriette; Karl, Isabell

    2011-05-01

    Temperature is an important selective agent in nature. Consequently, temperature-induced plasticity which may help buffering detrimental effects of temperature variation has received considerable attention over recent decades. Laboratory studies have almost exclusively used constant temperatures, while in nature, temperature typically shows pronounced daily fluctuations. Using a factorial design with constant versus fluctuating temperatures and a higher versus a lower mean temperature, we here investigate in the butterfly Lycaena tityrus whether the use of constant temperatures is justified. Fluctuating compared to constant temperatures caused shorter development times, increased heat but decreased cold stress resistance, decreased heat-shock protein expression, and increased immunocompetence. Thus, overall, fluctuating temperatures were more beneficial to the butterflies compared to constant ones. However, despite substantial variation across temperature regimes, the ranking of trait values among treatments remained largely unaffected (e.g. lower constant as well as fluctuating temperatures caused increased pupal mass). Thus, we tentatively conclude that there is no general reason for concern about using constant temperatures in studies investigating phenotypic plasticity, which seem to comprise a fair proxy. However, substantial differences in mean values as well as interactive effects suggest that one needs to be cautious. We further demonstrate negative effects of high temperatures on butterfly immune function, which seem to result from a trade-off between the latter and the heat shock response. PMID:21286923

  13. Studies of Electron Temperature Fluctuations in the Core of Alcator C-Mod Plasmas via Correlation ECE

    NASA Astrophysics Data System (ADS)

    Oi, C.; Sung, C.; Howard, N.; White, A. E.; Irby, J.; Leccacorvi, R.; Vieira, R.; Rice, J.; Gao, C.

    2012-10-01

    A correlation electron cyclotron emission (CECE) diagnostic has been designed and installed at the Alcator C-Mod tokamak to measure long wavelength fluctuations in electron temperature [C. Sung, this conference, C-Mod oral session]. It is important to characterize turbulent fluctuations in the plasma in order to better understand and predict transport, since the cross-magnetic field transport of particles and energy in fusion plasmas exceeds the values predicted by neoclassical theory. The first electron temperature fluctuation data collected from Alcator C-Mod ohmic plasmas has shown that as the ohmic confinement regime transitions from Linear Ohmic Confinement (LOC) to Saturated Ohmic Confinement (SOC) there is a decrease in the core electron temperature fluctuation level. The edge electron temperature fluctuations are similar between the two modes, suggesting that mainly the core turbulence characteristics change when there is a shift between LOC and SOC regimes. In both ohmic and ICRH plasmas, the measured spectrum is seen to broaden in response to increases in plasma rotation; and fluctuation level increases with radius. A description of the C-Mod CECE diagnostic will be presented, along with the initial measurements of turbulent electron temperature fluctuations.

  14. Diurnal temperature fluctuation effects on potatoes grown with 12 hr photoperiods

    NASA Technical Reports Server (NTRS)

    Bennett, S. M.; Tibbitts, T. W.; Cao, W.

    1991-01-01

    This study was designed to characterize the growth responses of potato (Solanum tuberosum L.) to diurnal temperature fluctuations. Potato plants of two cultivars, Norland and Denali, were grown for 90 days under 12 hr photoperiod in walk-in growth rooms at the University of Wisconsin Biotron. The alternating temperature was 22 C light/14 C dark and compared to a constant 18 C as control. At all temperature regimes vapor pressure deficit was maintained at 0.62 kPa (70% relative humidity [correction of humdidity] at 18 C). Plant height, plant dry weight, tuber dry weight, and harvest index were overall greater under the warm light/cool dark alternating temperatures than under the constant temperature. The differences between temperature treatments were greater for Denali than for Norland. Alternating temperatures increased Denali tuber weights by 25%, but no significant increase was found with Norland. Also the total plant weight was increased over 20% with Denali, but increased with Norland in only one of the two replications of the experiment. This study documents that alternating temperatures are a benefit to some cultivars but may not be of benefit to all cultivars.

  15. Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D

    SciTech Connect

    White, A. E.; Schmitz, L.; Peebles, W. A.; Rhodes, T. L.; Carter, T. A.; McKee, G. R.; Shafer, M. W.; Staebler, G. M.; Burrell, K. H.; DeBoo, J. C.; Prater, R.

    2010-02-15

    New measurements show that long-wavelength (k{sub t}hetarho{sub s}<0.5) electron temperature fluctuations can play an important role in determining electron thermal transport in low-confinement mode (L-mode) tokamak plasmas. In neutral beam-heated L-mode tokamak plasmas, electron thermal transport and the amplitude of long-wavelength electron temperature fluctuations both increase in cases where local electron cyclotron heating (ECH) is used to modify the plasma profiles. In contrast, the amplitude of simultaneously measured long-wavelength density fluctuations does not significantly increase. Linear stability analysis indicates that the ratio of the trapped electron mode (TEM) to ion temperature gradient (ITG) mode growth rates increases in the cases with ECH. The increased importance of the TEM drive relative to the ITG mode drive in the cases with ECH may be associated with the increases in electron thermal transport and electron temperature fluctuations.

  16. Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

    NASA Astrophysics Data System (ADS)

    Gierens, K. M.; Schumann, U.; Smit, H. G. J.; Helten, M.; Zängl, G.

    1997-08-01

    Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model.

  17. Spin-fluctuation mechanism of anomalous temperature dependence of magnetocrystalline anisotropy in itinerant magnets

    SciTech Connect

    Zhuravlev, I. A.; Antropov, V. P.; Belashchenko, K. D.

    2015-11-16

    The origins of the anomalous temperature dependence of magnetocrystalline anisotropy in (Fe1–xCox)2B alloys are elucidated using first-principles calculations within the disordered local moment model. Excellent agreement with experimental data is obtained. The anomalies are associated with the changes in band occupations due to Stoner-like band shifts and with the selective suppression of spin-orbit “hot spots” by thermal spin fluctuations. Under certain conditions, the anisotropy can increase, rather than decrease, with decreasing magnetization. These peculiar electronic mechanisms are in stark contrast to the assumptions of the existing models.

  18. Spin-fluctuation mechanism of anomalous temperature dependence of magnetocrystalline anisotropy in itinerant magnets

    DOE PAGESBeta

    Zhuravlev, I. A.; Antropov, V. P.; Belashchenko, K. D.

    2015-11-16

    The origins of the anomalous temperature dependence of magnetocrystalline anisotropy in (Fe1–xCox)2B alloys are elucidated using first-principles calculations within the disordered local moment model. Excellent agreement with experimental data is obtained. The anomalies are associated with the changes in band occupations due to Stoner-like band shifts and with the selective suppression of spin-orbit “hot spots” by thermal spin fluctuations. Under certain conditions, the anisotropy can increase, rather than decrease, with decreasing magnetization. These peculiar electronic mechanisms are in stark contrast to the assumptions of the existing models.

  19. Feasibility of measuring temperature and density fluctuations in air using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Massey, G. A.; Lemon, C. J.

    1984-01-01

    A tunable line-narrowed ArF laser can selectively excite several rotation al lines of the Schumann-Runge band system of O2 in air. The resulting ultraviolet fluorescence can be monitored at 90 deg to the laser beam axis, permitting space and time resolved observation of density and temperature fluctuations in turbulence. Experiments and calculations show that + or - 1 K, + or - 1 percent density, 1 cu mm spatial, and 1 microsecond temporal resolution can be achieved simultaneously under some conditions.

  20. Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array.

    PubMed

    Schubert, M; Endler, M; Thomsen, H

    2007-05-01

    Stationary Langmuir probe measurements of ion saturation current and floating potential in a plasma cannot give direct information on density and plasma potential fluctuations in the presence of temperature fluctuations. This problem can be avoided if the probe bias voltage is continuously swept faster than the fluctuation time scale, recording the current-voltage characteristic. This article reports the development of a spatiotemporal highly resolving Langmuir probe array with 15 fast swept tips, operating in the strongly magnetized, collisionless edge plasma of the Wendelstein 7-AS stellarator [Plasma Phys. Controlled Fusion 31, 1579 (1989)]. The probe tips are aligned in the poloidal direction, the tip spacing is 2 mm, and the sweeping frequency is 1.4 MHz. Current and voltage data are sampled with 50 MHz. The high bandwidth of the measurement is achieved by placing miniaturized differential amplifiers close to the probe tips in order to do an impedance transform. The surface-mounting technology and an additional inverse feedback module are utilized, allowing for an input voltage range of +/-100 V, and a common mode rejection rate of 55 dB at 4 MHz, which is sufficient to resolve the nonlinear probe characteristic. For the evaluation of the data, a fit model for stationary probes is employed and found adequate. Changes of the plasma parameters during one voltage sweep are taken into account by a linear interpolation of the fit parameters. Spatio-temporal fluctuation data gained by a fast swept Langmuir probe array, which can be relevant for the turbulent radial transport of particles and energy, are presented. PMID:17552818

  1. Observational Strategies of Cosmic Microwave Background Temperature and Polarization Interferometry Experiments

    NASA Astrophysics Data System (ADS)

    Park, Chan-Gyung; Ng, Kin-Wang; Park, Changbom; Liu, Guo-Chin; Umetsu, Keiichi

    2003-05-01

    We have simulated the interferometric observation of the cosmic microwave background (CMB) temperature and polarization fluctuations. We have constructed data pipelines from the time-ordered raw visibility samples to the CMB power spectra that utilize the methods of data compression, maximum likelihood analysis, and optimal subspace filtering. They are customized for three observational strategies: the single pointing, the mosaicking, and the drift-scanning. For each strategy, derived are the optimal strategy parameters that yield band power estimates with minimum uncertainty. The results are general and can be applied to any close-packed array on a single platform such as the CBI and the forthcoming AMiBA experiments. We have also studied the effect of rotation of the array platform on the band power correlation by simulating the CBI single-pointing observation. It is found that the band power anticorrelations can be reduced by rotating the platform and thus densely sampling the visibility plane. This enables us to increase the resolution of the power spectrum in the l-space down to the limit of the sampling theorem (Δl=226~π/θ), which is narrower by a factor of about sqrt(2) than the resolution limit (Δl~300) used in the recent CBI single-pointing observation. The validity of this idea is demonstrated for a two-element interferometer that samples visibilities uniformly in the uv-annulus. From the fact that the visibilities are the Fourier modes of the CMB field convolved with the beam, a fast unbiased estimator (FUE) of the CMB power spectra is developed and tested. It is shown that the FUE gives results very close to those from the quadratic estimator method without requiring large computer resources even though uncertainties in the results increase.

  2. Measurements of core electron temperature and density fluctuations in DIII-D and comparison to nonlinear gyrokinetic simulations

    SciTech Connect

    White, A. E.; Schmitz, L.; Peebles, W. A.; Carter, T. A.; Doyle, E. J.; Rhodes, T. L.; Wang, G.; McKee, G. R.; Shafer, M. W.; Holland, C.; Tynan, G. R.; Austin, M. E.; Burrell, K. H.; Candy, J.; DeBoo, J. C.; Prater, R.; Staebler, G. M.; Waltz, R. E.; Makowski, M. A.

    2008-05-15

    For the first time, profiles (0.3<{rho}<0.9) of electron temperature and density fluctuations in a tokamak have been measured simultaneously and the results compared to nonlinear gyrokinetic simulations. Electron temperature and density fluctuations measured in neutral beam-heated, sawtooth-free low confinement mode (L-mode) plasmas in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] are found to be similar in frequency and normalized amplitude, with amplitude increasing with radius. The measured radial profile of two fluctuation fields allows for a new and rigorous comparison with gyrokinetic results. Nonlinear gyrokinetic flux-tube simulations predict that electron temperature and density fluctuations have similar normalized amplitudes in L-mode. At {rho}=0.5, simulation results match experimental heat diffusivities and density fluctuation amplitude, but overestimate electron temperature fluctuation amplitude and particle diffusivity. In contrast, simulations at {rho}=0.75 do not match either the experimentally derived transport properties or the measured fluctuation levels.

  3. Electron Temperature Fluctuations Associated with the Weakly Coherent Mode in the Edge of I-mode Plasmas

    NASA Astrophysics Data System (ADS)

    White, A. E.; Phillips, P.; Whyte, D. G.; Hubbard, A. E.; Sung, C.; Hughes, J. W.; Dominguez, A.; Terry, J.; Cziegler, I.

    2012-03-01

    New measurements of electron temperature fluctuations associated with the weakly coherent mode (WCM) during improved mode, or I-mode plasmas at Alcator C-Mod are presented in this poster [A. E. White, et al. Nuclear Fusion, 51, 113005 (2011)]. The measurements are made with a 32-channel, high-resolution profile ECE radiometer. The WCM electron temperature fluctuations are localized to a 1 cm region inside the last closed flux surface. The WCM electron temperature fluctuation level is measured in several different I-mode discharges and is in the range 1-2%, which is up to an order of magnitude smaller than the WCM density fluctuation level. The WCM edge fluctuations observed in I-mode are believed to play a role in increasing particle transport but not energy transport in the edge of I-mode plasmas. The large difference between normalized density and electron temperature fluctuation amplitudes provides new evidence that the WCM fluctuations can separately affect energy and particle transport.

  4. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    SciTech Connect

    Yung Moo Huh

    2001-05-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H{parallel}c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T{sub c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T{sub c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La{sub 2-x}Sr{sub x}CuO{sub 4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T{sub c}. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance {zeta}{sub c} becomes comparable to the spacing between adjacent CuO{sub 2} layers s at sufficiently high magnetic fields near H{sub c2}.

  5. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    SciTech Connect

    Douglas K. Finnemore

    2001-06-25

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H {parallel} c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T{sub c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T{sub c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La{sub 2-x}Sr{sub x}CuO{sub 4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T{sub c}. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance {xi}{sub c} becomes comparable to the spacing between adjacent CuO{sub 2} layers s at sufficiently high magnetic field near H{sub c2}.

  6. Note: Demonstration of an external-cavity diode laser system immune to current and temperature fluctuations.

    PubMed

    Miao, Xinyu; Yin, Longfei; Zhuang, Wei; Luo, Bin; Dang, Anhong; Chen, Jingbiao; Guo, Hong

    2011-08-01

    We demonstrate an external-cavity laser system using an anti-reflection coated laser diode as gain medium with about 60 nm fluorescence spectrum, and a Rb Faraday anomalous dispersion optical filter (FADOF) as frequency-selecting element with a transmission bandwidth of 1.3 GHz. With 6.4% optical feedback, a single stable longitudinal mode is obtained with a linewidth of 69 kHz. The wavelength of this laser is operating within the center of the highest transmission peak of FADOF over a diode current range from 55 mA to 142 mA and a diode temperature range from 15 °C to 35 °C, thus it is immune to the fluctuations of current and temperature. PMID:21895284

  7. Pressure and temperature fluctuation simulation of J-PARC cryogenic hydrogen system

    NASA Astrophysics Data System (ADS)

    Tatsumoto, H.; Ohtsu, K.; Aso, T.; Kawakami, Y.

    2015-12-01

    The J-PARC cryogenic hydrogen system provides supercritical cryogenic hydrogen to the moderators at a pressure of 1.5 MPa and temperature of 18 K and removes 3.8 kW of nuclear heat from the 1 MW proton beam operation. We prepared a heater for thermal compensation and an accumulator, with a bellows structure for volume control, to mitigate the pressure fluctuation caused by switching the proton beam on and off. In this study, a 1-D simulation code named DiSC-SH2 was developed to understand the propagation of pressure and temperature propagations through the hydrogen loop due to on and off switching of the proton beam. We confirmed that the simulated dynamic behaviors in the hydrogen loop for 300-kW and 500-kW proton beam operations agree well with the experimental data under the same conditions.

  8. Measurement of temperature and density fluctuations in turbulence using an ultraviolet laser

    NASA Technical Reports Server (NTRS)

    Massey, G. A.

    1984-01-01

    Noninvasive measurement of density and temperature fluctuations in turbulent air flow was examined. The approach used fluorescence of oxygen molecules which are selectively excited by a tunable vacuum ultraviolet laser beam. The strength of the fluorescence signal and its dependence on laser wavelength vary with the density and temperature of the air in the laser beam. Because fluorescence can be detected at 90 degrees from the beam propagation direction, spatial resolution in three dimensions, rather than path-integrated measurements can be achieved. With spatial resolutions of the order of a millimeter and at supersonic air velocities it is necessary to perform each measurement in a time of the order of a microsecond; this is possible by by using laser pulses of ten nanosecond duration. In this method atmospheric O2 is excited by the emission of a tunable ArF excimer laser, and the fluorescence, which spans the 210 to 420 range, is detected by an ultraviolet phototube.

  9. Temperature-dependent fluctuations in the two-dimensional XY model

    NASA Astrophysics Data System (ADS)

    Banks, S. T.; Bramwell, S. T.

    2005-06-01

    We present a detailed investigation of the probability density function (PDF) of order parameter fluctuations in the finite two-dimensional XY (2dXY) model. In the low-temperature critical phase of this model, the PDF approaches a universal non-Gaussian limit distribution in the limit T → 0. Our analysis resolves the question of temperature dependence of the PDF in this regime, for which conflicting results have been reported. We show analytically that a weak temperature dependence results from the inclusion of multiple loop graphs in a previously derived graphical expansion. This is confirmed by numerical simulations on two controlled approximations to the 2dXY model: the harmonic and 'harmonic XY' models. The harmonic model has no Kosterlitz-Thouless-Berezinskiĭ (KTB) transition and the PDF becomes progressively less skewed with increasing temperature until it closely approximates a Gaussian function above T ap 4π. Near to that temperature, we find some evidence of a phase transition, although our observations appear to exclude a thermodynamic singularity.

  10. Cross-correlating Cosmic IR and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources

    NASA Technical Reports Server (NTRS)

    Cappelluti, N.; Kashlinsky, A.; Arendt, R. G.; Comastri, A.; Fazio, G. G.; Finoguenov, A.; Hasinger, G.; Mather, J. C.; Miyaji, T; Moseley, S. H.

    2013-01-01

    In order to understand the nature of the sources producing the recently uncovered cosmic infrared background (CIB) fluctuations, we study cross-correlations between the fluctuations in the source-subtracted CIB from Spitzer/IRAC data and the unresolved cosmic X-ray background from deep Chandra observations. Our study uses data from the EGS/AEGIS field, where both data sets cover an approx = 8' x 45' region of the sky. Our measurement is the cross-power spectrum between the IR and X-ray data. The cross-power signal between the IRAC maps at 3.6 micron and 4.5 micron and the Chandra [0.5-2] keV data has been detected, at angular scales approx >20'', with an overall significance of approx = 3.8 sigma and approx. = 5.6 sigma, respectively. At the same time we find no evidence of significant cross-correlations at the harder Chandra bands. The cross-correlation signal is produced by individual IR sources with 3.6 micron and 4.5 micron magnitudes m(sub AB) approx. > 25-26 and [0.5-2] keV X-ray fluxes << 7 × 10(exp -177 erg sq. cm/ s. We determine that at least 15%-25% of the large scale power of the CIB fluctuations is correlated with the spatial power spectrum of the X-ray fluctuations. If this correlation is attributed to emission from accretion processes at both IR and X-ray wavelengths, this implies a much higher fraction of accreting black holes than among the known populations. We discuss the various possible origins for the cross-power signal and show that neither local foregrounds nor the known remaining normal galaxies and active galactic nuclei can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations. local foregrounds, nor the known remaining normal galaxies and active galactic nuclei (AGN) can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations

  11. Measurement of electron temperature fluctuations using a tunable correlation electron cyclotron emission system on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Howard, N. T.; Sung, C.; White, A. E.

    2014-11-01

    A tunable correlation electron cyclotron (CECE) system was recently installed on the Alcator C-Mod tokamak to provide local, quantitative measurement of electron temperature fluctuations in the tokamak core. This system represents a significant upgrade from the original CECE system, expanding the measurement capabilities from 4 to 8 total channels, including 2 remotely tunable YIG filters (6-18 GHz; 200 MHz bandwidth). Additional upgrades were made to the optical system to provide enhanced poloidal resolution and allow for measurement of turbulent fluctuations below kθρs < 0.3. These expanded capabilities allow for single shot measurement of partial temperature fluctuation profiles in the region ρ = 0.7 - 0.9 (square root of normalized toroidal flux) in a wide variety of plasma conditions. These measurements are currently being used to provide stringent tests of the gyrokinetic model in ongoing model validation efforts. Details of the hardware upgrades, turbulent fluctuation measurements, and ongoing comparisons with simulations are presented.

  12. Modelling spoilage of fresh turbot and evaluation of a time-temperature integrator (TTI) label under fluctuating temperature.

    PubMed

    Nuin, Maider; Alfaro, Begoña; Cruz, Ziortza; Argarate, Nerea; George, Susie; Le Marc, Yvan; Olley, June; Pin, Carmen

    2008-10-31

    Kinetic models were developed to predict the microbial spoilage and the sensory quality of fresh fish and to evaluate the efficiency of a commercial time-temperature integrator (TTI) label, Fresh Check(R), to monitor shelf life. Farmed turbot (Psetta maxima) samples were packaged in PVC film and stored at 0, 5, 10 and 15 degrees C. Microbial growth and sensory attributes were monitored at regular time intervals. The response of the Fresh Check device was measured at the same temperatures during the storage period. The sensory perception was quantified according to a global sensory indicator obtained by principal component analysis as well as to the Quality Index Method, QIM, as described by Rahman and Olley [Rahman, H.A., Olley, J., 1984. Assessment of sensory techniques for quality assessment of Australian fish. CSIRO Tasmanian Regional Laboratory. Occasional paper n. 8. Available from the Australian Maritime College library. Newnham. Tasmania]. Both methods were found equally valid to monitor the loss of sensory quality. The maximum specific growth rate of spoilage bacteria, the rate of change of the sensory indicators and the rate of change of the colour measurements of the TTI label were modelled as a function of temperature. The temperature had a similar effect on the bacteria, sensory and Fresh Check kinetics. At the time of sensory rejection, the bacterial load was ca. 10(5)-10(6) cfu/g. The end of shelf life indicated by the Fresh Check label was close to the sensory rejection time. The performance of the models was validated under fluctuating temperature conditions by comparing the predicted and measured values for all microbial, sensory and TTI responses. The models have been implemented in a Visual Basic add-in for Excel called "Fish Shelf Life Prediction (FSLP)". This program predicts sensory acceptability and growth of spoilage bacteria in fish and the response of the TTI at constant and fluctuating temperature conditions. The program is freely

  13. Optical measurements of fluctuating temperatures in a supersonic turbulent flow using one- and two-photon, laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Gross, K. P.; Mckenzie, R. L.

    1984-01-01

    A laser-induced fluorescence technique was developed that provides a practical means of nonintrusively measuring the instantaneous temperatures in low-temperature turbulent flows. The capabilities of the method are reviewed, and its application to a simple, two-dimensional, turbulent boundary-layer flow at Mach 2 is reported. Measurements of the average temperature distribution through the boundary layer and the magnitudes of temperature fluctuations about their average values are presented.

  14. Effect of Diurnal Fluctuating versus Constant Temperatures on Germination of 445 Species from the Eastern Tibet Plateau

    PubMed Central

    Liu, Kun; Baskin, Jerry M.; Baskin, Carol C.; Bu, Haiyan; Du, Guozhen; Ma, Miaojun

    2013-01-01

    Germination response to fluctuating temperatures is a mechanism by which seeds detect gaps in vegetation canopies and depth of burial in soil, and it is very important for plants. Thus, studies on the effect of fluctuating temperature on germination at the community level are valuable for understanding community structure and biodiversity maintenance. We determined the effects of two alternating temperatures (5/25°C and 10/20°C) and one constant temperature (15°C) on seed germination of 445 species in a grassland community on the eastern Tibet Plateau. Seed mass was determined for each species, and data on habitat, type of life cycle, altitudinal distribution and functional group (graminoids or forbs) were obtained from the literature. Taking all species into account, alternating temperatures increased germination percentages regardless of amplitude. Overall, species growing in disturbed ground showed a significant germination response to temperature fluctuation, but those living in Alpine/subalpine meadow, forest margin /scrub, marshland and dry sunny slope habitats did not. Species distributed only at high elevations (>2000m) did not show a significant germination response to temperature fluctuation, whereas those occurring at both high and low elevations had a significant positive response. Germination of annuals/biennials was significantly promoted by 5/25°C, but not by 10/20°C, whereas germination of perennials was significantly promoted by both 5/25°C and 10/20°C. Small-seeded species were more likely than large-seeded species to respond positively to fluctuating temperatures. Germination of forbs had a positive response to temperature fluctuation, but germination of graminoids did not. Regeneration ability by seeds for about 36% of the species studied in the grassland can be increased by temperature fluctuation. The differential response among species to alternating vs. constant temperatures helps maintain community structure and biodiversity. A

  15. Damage Evolution in Al Wire Bonds Subjected to a Junction Temperature Fluctuation of 30 K

    NASA Astrophysics Data System (ADS)

    Agyakwa, Pearl A.; Yang, Li; Arjmand, Elaheh; Evans, Paul; Corfield, Martin R.; Johnson, C. Mark

    2016-07-01

    Ultrasonically bonded heavy Al wires subjected to a small junction temperature fluctuation under power cycling from 40°C to 70°C were investigated using a non-destructive three-dimensional (3-D) x-ray tomography evaluation approach. The occurrence of irreversible deformation of the microstructure and wear-out under such conditions were demonstrated. The observed microstructures consist of interfacial and inter-granular cracks concentrated in zones of stress intensity, i.e., near heels and emanating from interface precracks. Interfacial voids were also observed within the bond interior. Degradation rates of `first' and `stitch' bonds are compared and contrasted. A correlative microscopy study combining perspectives from optical microscopy with the x-ray tomography results clarifies the damage observed. An estimation of lifetime is made from the results and discussed in the light of existing predictions.

  16. Damage Evolution in Al Wire Bonds Subjected to a Junction Temperature Fluctuation of 30 K

    NASA Astrophysics Data System (ADS)

    Agyakwa, Pearl A.; Yang, Li; Arjmand, Elaheh; Evans, Paul; Corfield, Martin R.; Johnson, C. Mark

    2016-04-01

    Ultrasonically bonded heavy Al wires subjected to a small junction temperature fluctuation under power cycling from 40°C to 70°C were investigated using a non-destructive three-dimensional (3-D) x-ray tomography evaluation approach. The occurrence of irreversible deformation of the microstructure and wear-out under such conditions were demonstrated. The observed microstructures consist of interfacial and inter-granular cracks concentrated in zones of stress intensity, i.e., near heels and emanating from interface precracks. Interfacial voids were also observed within the bond interior. Degradation rates of `first' and `stitch' bonds are compared and contrasted. A correlative microscopy study combining perspectives from optical microscopy with the x-ray tomography results clarifies the damage observed. An estimation of lifetime is made from the results and discussed in the light of existing predictions.

  17. Measurement of Turbulent Pressure and Temperature Fluctuations in a Gas Turbine Combustor

    NASA Technical Reports Server (NTRS)

    Povinelli, Louis (Technical Monitor); LaGraff, John E.; Bramanti, Cristina; Pldfield, Martin; Passaro, Andrea; Biagioni, Leonardo

    2004-01-01

    The report summarizes the results of the redesign efforts directed towards the gas-turbine combustor rapid-injector flow diagnostic probe developed under sponsorship of NASA-GRC and earlier reported in NASA-CR-2003-212540. Lessons learned during the theoretical development, developmental testing and field-testing in the previous phase of this research were applied to redesign of both the probe sensing elements and of the rapid injection device. This redesigned probe (referred to herein as Turboprobe) has been fabricated and is ready, along with the new rapid injector, for field-testing. The probe is now designed to capture both time-resolved and mean total temperatures, total pressures and, indirectly, one component of turbulent fluctuations.

  18. Information entropy of activation process: Application for low-temperature fluctuations of a myoglobin molecule

    NASA Astrophysics Data System (ADS)

    Stepanov, A. V.

    2015-11-01

    Activation process for unimolecular reaction has been considered by means of radiation theory. The formulae of information entropy of activation have been derived for the Boltzmann-Arrhenius model and the activation process model (APM). The physical meaning of this entropy has been determined. It is a measure of conversion of thermal radiation energy to mechanical energy that moves atoms in a molecule during elementary activation act. It is also a measure of uncertainty of this energy conversion. The uncertainty is due to unevenness of distribution function representing the activation process. It has been shown that Arrhenius dependence is caused by the entropy change. Efficiency comparison of the two models under consideration for low-temperature fluctuations of a myoglobin molecule structure shows that the APM should be favored over the Boltzmann-Arrhenius one.

  19. Pressure dependence of critical temperature of bulk FeSe from spin fluctuation theory

    NASA Astrophysics Data System (ADS)

    Hirschfeld, Peter; Kreisel, Andreas; Wang, Yan; Tomic, Milan; Jeschke, Harald; Jacko, Anthony; Valenti, Roser; Maier, Thomas; Scalapino, Douglas

    2013-03-01

    The critical temperature of the 8K superconductor FeSe is extremely sensitive to pressure, rising to a maximum of 40K at about 10GPa. We test the ability of the current generation of fluctuation exchange pairing theories to account for this effect, by downfolding the density functional theory electronic structure for each pressure to a tight binding model. The Fermi surface found in such a procedure is then used with fixed Hubbard parameters to determine the pairing strength using the random phase approximation for the spin singlet pairing vertex. We find that the evolution of the Fermi surface captured by such an approach is alone not sufficient to explain the observed pressure dependence, and discuss alternative approaches. PJH, YW, AK were supported by DOE DE-FG02-05ER46236, the financial support of MT, HJ, and RV from the DFG Schwerpunktprogramm 1458 is kindly acknowledged.

  20. The effects of eggshell temperature fluctuations during incubation on welfare status and gait score of broilers.

    PubMed

    Ipek, A; Sozcu, A

    2016-06-01

    The aim of the current study was to determine the effects of different eggshell temperatures (EST); low (33.3 to 36.7°C), control (37.8 to 38.2°C), and high (38.9 to 40.0°C) during 10 to 18 days of incubation on welfare status including foot pad dermatitis (FPD), hock dermatitis (HD) and feathering status, and gait score in broilers. Score 2, 4, and 5 of FPD were found to be similar among the treatment groups, whereas a score of 3 was found to be higher in the control and high EST groups (27.7% and 29.2%) compred to the low EST group (16.9%). The eggshell temperature fluctuations were significantly affected the incidence of HD, whereas broiler sex did not. All of the broilers in the high EST group had HD with various scores, while a percentage of 21.1% and 6.9% of broilers had the score 1 of HD in the low and control EST groups, respectively. Feathering status showed a difference between body parts including wing, neck, back, and vent and also a general mean score of broilers from low EST treatment had the highest score for feathering. A higher incidence of gait score was observed in broilers from the control EST treatment than low and high EST groups. This can be attributed to a higher live weight of broilers from the control EST group. On the other hand, the incidence of a gait score of 3 and 4 was found for broilers from control and high EST treatment groups. Male and female broilers from the high EST group had the higher gait score. In conclusion, gait score and welfare status of broilers were affected by fluctuations in EST between 10 and 18 days of incubation. PMID:26944961

  1. A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature

    PubMed Central

    Potyrailo, Radislav A.; Surman, Cheryl

    2013-01-01

    Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

  2. A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature.

    PubMed

    Potyrailo, Radislav A; Surman, Cheryl

    2013-08-01

    Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

  3. Binary homogeneous nucleation: Temperature and relative humidity fluctuations and non-linearity

    SciTech Connect

    Easter, R.C.; Peters, L.K.

    1993-01-01

    This report discusses binary homogeneous nucleation involving H{sub 2}SO{sub 4} and water vapor is thought to be the primary mechanism for new particle formation in the marine boundary layer. Temperature, relative humidity, and partial pressure of H{sub 2}SO{sub 4} vapor are the most important parameters in fixing the binary homogeneous nucleation rate in the H{sub 2}SO{sub 4}/H{sub 2}O system. The combination of thermodynamic calculations and laboratory experiments indicates that this rate varies roughly as the tenth power of the saturation ratio of H{sub 2}SO{sub 4} vapor. Furthermore, the vapor pressure of H{sub 2}SO{sub 4} is a function of temperature, and similar dependencies of the binary homogeneous nucleation rate on relative humidity can be noted as well. These factors thus introduce strong non-linearities into the system, and fluctuations of temperature, relative humidity, and H{sub 2}SO{sub 4} vapor concentrations about mean values may strongly influence the nucleation rate measured in the atmosphere.

  4. 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.

  5. Measurement of Turbulent Pressure and Temperature Fluctuations in a Gas Turbine Combustor

    NASA Technical Reports Server (NTRS)

    Passaro, Andrea; LaGraff, John E.; Oldfield, Martin L. G.; Biagioni, Leonardo; Moss, Roger W.; Battelle, Ryan T.; Povinelli, Louis A. (Technical Monitor)

    2003-01-01

    The present research concerns the development of high-frequency pressure and temperature probes and related instrumentation capable of performing spectral characterization of unsteady pressure and temperature fluctuations over the 0.05 20 kHz range, at the exit of a gas turbine combustor operating at conditions close to nominal ones for large power generation turbomachinery. The probes used a transient technique pioneered at Oxford University; in order to withstand exposure to the harsh environment the probes were fitted on a rapid injection and cooling system jointly developed by Centrospazio CPR and Syracuse University. The experimental runs were performed on a large industrial test rig being operated by ENEL Produzione. The achieved results clearly show the satisfactory performance provided by this diagnostic tool, even though the poor location of the injection port prevented the tests from yielding more insight of the core flow turbulence characteristics. The pressure and temperature probes survived several dozen injections in the combustor hot jet, while consistently providing the intended high frequency performance. The apparatus was kept connected to the combustor during long duration firings, operating as an unobtrusive, self contained, piggy-back experiment: high frequency flow samplings were remotely recorded at selected moments corresponding to different combustor operating conditions.

  6. Effects of fast-acting high-frequency compression on the intelligibility of speech in steady and fluctuating background sounds.

    PubMed

    Stone, M A; Moore, B C; Wojtczak, M; Gudgin, E

    1997-08-01

    This study examines whether speech intelligibility in background sounds can be improved for persons with loudness recruitment by the use of fast-acting compression applied at high frequencies, when the overall level of the sounds is held constant by means of a slow-acting automatic gain control (AGC) system and when appropriate frequency-response shaping is applied. Two types of fast-acting compression were used in the high-frequency channel of a two-channel system: a compression limiter with a 10:1 compression ratio and with a compression threshold about 9 dB below the peak level of the signal in the high-frequency channel; and a wide dynamic range compressor with a 2:1 compression ratio and with the compression threshold about 24 dB below the peak level of the signal in the high-frequency channel. A condition with linear processing in the high-frequency channel was also used. Speech reception thresholds (SRTs) were measured for two background sounds: a steady speech-shaped noise and a single male talker. All subjects had moderate-to-severe sensorineural hearing loss. Three different types of speech material were used: the adaptive sentence lists (ASL), the Bamford-Kowal-Bench (BKB) sentence lists and the Boothroyd word lists. For the steady background noise, the compression generally led to poorer performance than for the linear condition, although the deleterious effect was only significant for the 10:1 compression ratio. For the background of a single talker, the compression had no significant effect except for the ASL sentences, where the 10:1 compression gave significantly better performance than the linear condition. Overall, the results did not show any clear benefits of the fast-acting compression, possibly because the slow-acting AGC allowed the use of gains in the linear condition that were markedly higher than would normally be used with linear hearing aids. PMID:9307821

  7. Amplitude-frequency fluctuations of the seasonal cycle, temperature anomalies, and long-range persistence of climate records

    NASA Astrophysics Data System (ADS)

    Vecchio, A.; Carbone, V.

    2010-12-01

    The presence of long-term persistence of climate records on scales from 2 to 15 yr has been reported in the literature, even if the universality of this result is controversial. In the present paper results from monthly temperature records measured for about 250 yr in Prague and Milan are reported. Because of the nonlinear and nonstationary character of temperature time series the seasonal contribution has been identified through the empirical mode decomposition. We find that the seasonal component of the climate records is characterized by some time scales showing both amplitude and phase fluctuations. By using a more suitable definition of temperature anomalies, and thus excluding persistence effects due to seasonal oscillations and trends, the occurrence of long-term persistence has been investigated through the detrended fluctuation analysis. Our results indicate persistence on scales from 3 to 10 yr with similar values for the detrended fluctuation analysis indices.

  8. Limb Looking: The effects of background subtraction on the temperature of SXT loops.

    NASA Astrophysics Data System (ADS)

    Medlin, D. A.; Blevins, H. T.; Schmelz, J. T.

    2003-05-01

    Knowing the temperature distribution along a loop is one possible test for the coronal heating models. The matter of how background subtraction may or may not affect the temperature distribution of loops could also play a crucial role in this analysis. Several instruments are currently available for loop studies, and numerous techniques are used to determine the temperature distributions along the loops. This has lead to many different, and mostly conflicting temperature results. We have chosen the Soft X-ray Telescope (SXT), aboard the Japanese satellite Yohkoh, for this study. The SXT data archives were searched for possible loop candidates. A set of loops on the limb, as well as a set of loops on the disk, were chosen for analysis. Temperature maps were generated for each loop with and without background subtraction. For each loop, we used both a uniform background subtraction as well as a pixel-by-pixel background subtraction. Once the temperature as a function of arc length has been found, it is then compared to the predictions made by different models. The Solar physics research at the University of Memphis is supported by NASA grants NAG5-9783 and NAG5-12096.

  9. A high speed data acquisition and analysis system for transonic velocity, density, and total temperature fluctuations

    NASA Technical Reports Server (NTRS)

    Clukey, Steven J.

    1988-01-01

    The high speed Dynamic Data Acquisition System (DDAS) is described which provides the capability for the simultaneous measurement of velocity, density, and total temperature fluctuations. The system of hardware and software is described in context of the wind tunnel environment. The DDAS replaces both a recording mechanism and a separate data processing system. The data acquisition and data reduction process has been combined within DDAS. DDAS receives input from hot wires and anemometers, amplifies and filters the signals with computer controlled modules, and converts the analog signals to digital with real-time simultaneous digitization followed by digital recording on disk or tape. Automatic acquisition (either from a computer link to an existing wind tunnel acquisition system, or from data acquisition facilities within DDAS) collects necessary calibration and environment data. The generation of hot wire sensitivities is done in DDAS, as is the application of sensitivities to the hot wire data to generate turbulence quantities. The presentation of the raw and processed data, in terms of root mean square values of velocity, density and temperature, and the processing of the spectral data is accomplished on demand in near-real-time- with DDAS. A comprehensive description of the interface to the DDAS and of the internal mechanisms will be prosented. A summary of operations relevant to the use of the DDAS will be provided.

  10. Similar metabolic rate-temperature relationships after acclimation at constant and fluctuating temperatures in caterpillars of a sub-Antarctic moth.

    PubMed

    Chown, Steven L; Haupt, Tanya M; Sinclair, Brent J

    2016-02-01

    Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate - temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0-10 °C, 5-15 °C, and 10-20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3-14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q10 of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5-15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic. PMID:26592773

  11. The role of spatial scale and background climate in the latitudinal temperature response to deforestation

    NASA Astrophysics Data System (ADS)

    Li, Y.; de Noblet-Ducoudré, N.; Davin, E. L.; Zeng, N.; Motesharrei, S.; Li, S. C.; Kalnay, E.

    2015-10-01

    Previous modeling and empirical studies have shown that the biophysical impact of deforestation is to warm the tropics and cool the extra-tropics. In this study, we use an earth system model to investigate how deforestation at various spatial scales affects ground temperature, with an emphasis on the latitudinal temperature response and its underlying mechanisms. Results show that the latitudinal pattern of temperature response depends non-linearly on the spatial extent of deforestation and the fraction of vegetation change. Compared with regional deforestation, temperature change in global deforestation is greatly amplified in temperate and boreal regions, but is dampened in tropical regions. Incremental forest removal leads to increasingly larger cooling in temperate and boreal regions, while the temperature increase saturates in tropical regions. The latitudinal and spatial patterns of the temperature response are driven by two processes with competing temperature effects: decreases in absorbed shortwave radiation due to increased albedo and decreases in evapotranspiration. These changes in the surface energy balance reflect the importance of the background climate on modifying the deforestation impact. Shortwave radiation and precipitation have an intrinsic geographical distribution that constrains the effects of biophysical changes and therefore leads to temperature changes that are spatially varying. For example, wet (dry) climate favors larger (smaller) evapotranspiration change, thus warming (cooling) is more likely to occur. Further analysis on the contribution of individual biophysical factors (albedo, roughness, and evapotranspiration efficiency) reveals that the latitudinal signature embodied in the temperature change probably result from the background climate conditions rather than the initial biophysical perturbation.

  12. The cosmic microwave background radiation temperature at a redshift of 2.34.

    PubMed

    Srianand, R; Petitjean, P; Ledoux, C

    The existence of the cosmic microwave background radiation is a fundamental prediction of hot Big Bang cosmology, and its temperature should increase with increasing redshift. At the present time (redshift z = 0), the temperature has been determined with high precision to be T(CMBR)(0) = 2.726 +/- 0.010 K. In principle, the background temperature can be determined using measurements of the relative populations of atomic fine-structure levels, which are excited by the background radiation. But all previous measurements have achieved only upper limits, thus still formally permitting the radiation temperature to be constant with increasing redshift. Here we report the detection of absorption lines from the first and second fine-structure levels of neutral carbon atoms in an isolated cloud of gas at z = 2.3371. We also detected absorption due to several rotational transitions of molecular hydrogen, and fine-structure lines of singly ionized carbon. These constraints enable us to determine that the background radiation was indeed warmer in the past: we find that T(CMBR)(z = 2.3371) is between 6.0 and 14 K. This is in accord with the temperature of 9.1 K predicted by hot Big Bang cosmology. PMID:11140672

  13. Simulated Seasonal Photoperiods and Fluctuating Temperatures Have Limited Effects on Blood Feeding and Life History in Aedes triseriatus (Diptera: Culicidae).

    PubMed

    Westby, K M; Juliano, S A

    2015-09-01

    Biotic and abiotic factors change seasonally and impact life history in temperate-zone ectotherms. Temperature and photoperiod are factors that change in predictable ways. Most studies testing for effects of temperature on vectors use constant temperatures and ignore potential correlated effects of photoperiod. In two experiments, we tested for effects of larval rearing environments creating ecologically relevant temperatures and photoperiods simulating early and late season conditions (June and August), or constant temperatures (cool and warm) with the June or August photoperiods, respectively. We determined effects on survivorship, development, size, and a composite performance index in a temperate-zone population of Aedes triseriatus (Say). We followed cohorts of resulting females, all held under the same environmental conditions, to assess carry-over effects of rearing conditions for larvae on longevity, blood feeding, and egg production. Larval survivorship was affected by treatment in one experiment. Development time was greater in the June and cool treatments, but the constant and fluctuating temperatures did not differ. Significantly larger mosquitoes were produced in fluctuating versus constant temperature treatments. There were no significant treatment effects on the composite performance index. Adult female longevity was lower after rearing at constant versus fluctuating temperature, but there was no difference between June and August, nor did size affect longevity. There was no effect of treatments on blood feeding and a limited effect on egg production. We conclude that seasonal temperatures and photoperiods during development have limited effects on this population of A. triseriatus and find little evidence of strong effects of fluctuating versus constant temperatures. PMID:26336255

  14. Geometrical aspects and connections of the energy-temperature fluctuation relation

    NASA Astrophysics Data System (ADS)

    Velazquez, L.; Curilef, S.

    2009-08-01

    Recently, we have derived a generalization of the known canonical fluctuation relation kBC = β2langδU2rang between heat capacity C and energy fluctuations, which can account for the existence of macrostates with negative heat capacities C < 0. In this work, we present a panoramic overview of direct implications and connections of this fluctuation theorem with other developments of statistical mechanics, such as the extension of canonical Monte Carlo methods, the geometric formulations of fluctuation theory and the relevance of a geometric extension of the Gibbs canonical ensemble that has been recently proposed in the literature.

  15. [IR spectral-analysis-based range estimation for an object with small temperature difference from background].

    PubMed

    Fu, Xiao-Ning; Wang, Jie; Yang, Lin

    2013-01-01

    It is a typical passive ranging technology that estimation of distance of an object is based on transmission characteristic of infrared radiation, it is also a hotspot in electro-optic countermeasures. Because of avoiding transmitting energy in the detection, this ranging technology will significantly enhance the penetration capability and infrared conceal capability of the missiles or unmanned aerial vehicles. With the current situation in existing passive ranging system, for overcoming the shortage in ranging an oncoming target object with small temperature difference from background, an improved distance estimation scheme was proposed. This article begins with introducing the concept of signal transfer function, makes clear the working curve of current algorithm, and points out that the estimated distance is not unique due to inherent nonlinearity of the working curve. A new distance calculation algorithm was obtained through nonlinear correction technique. It is a ranging formula by using sensing information at 3-5 and 8-12 microm combined with background temperature and field meteorological conditions. The authors' study has shown that the ranging error could be mainly kept around the level of 10% under the condition of the target and background apparent temperature difference equal to +/- 5 K, and the error in estimating background temperature is no more than +/- 15 K. PMID:23586223

  16. Electron temperature fluctuations changes associated with ELM suppression by RMP in DIII-D

    NASA Astrophysics Data System (ADS)

    Sung, C.; Wang, G.; Rhodes, T.; Peebles, W.

    2015-11-01

    New results in this presentation show an increase in broadband electron temperature fluctuations (T~e) during ELM suppression by resonant magnetic perturbations (RMP). This measurement is obtained via correlation ECE (CECE) near the top of the pedestal (ρ ~ 0.9 - 0.96). This T~e increase is significant, (>40%), and occurs after the ELM suppression but not between ELMS. This may imply an increase in thermal transport facilitated by the increased T~e levels. Considering that the changes in gradient scale length during ELMs with RMP are complicated, it is possible that the mechanism responsible for changing T~e is different compared to previously observed changes in ñe [G. R. McKee et al NF 2013]. This possibility, and the nature of the T~e , will be studied through profile analysis and linear gyrokinetic analysis using TGLF [J. E. Kinsey et al PoP 2008]. In addition, the relation between the T~e and an observed low frequency coherent mode will be investigated. Work supported by the US DOE under DE-FG02-08ER54984 and DE-FC02-04ER54698.

  17. A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Foy, E.; Ronan, G.; Chinitz, W.

    1982-01-01

    A principal element to be derived from modeling turbulent reacting flows is an expression for the reaction rates of the various species involved in any particular combustion process under consideration. A temperature-derived most-likely probability density function (pdf) was used to describe the effects of temperature fluctuations on the Arrhenius reaction rate constant. A most-likely bivariate pdf described the effects of temperature and species concentrations fluctuations on the reaction rate. A criterion is developed for the use of an "appropriate" temperature pdf. The formulation of models to calculate the mean turbulent Arrhenius reaction rate constant and the mean turbulent reaction rate is considered and the results of calculations using these models are presented.

  18. Thermal Fluctuations in a Layer of Liquid CS2 Subjected to Temperature Gradients with and without the Influence of Gravity

    NASA Astrophysics Data System (ADS)

    Takacs, Christopher J.; Vailati, Alberto; Cerbino, Roberto; Mazzoni, Stefano; Giglio, Marzio; Cannell, David S.

    2011-06-01

    We report data for nonequilibrium density fluctuations in a layer of liquid CS2 subjected to temperature gradients on Earth and in a satellite. The structure factor S(q) was measured using a calibrated shadowgraph. Upon removing gravity, S(q) increased dramatically at small wave vector, until the fluctuations generated by thermal noise were limited only by the 3 mm sample thickness. The results agree with theory to within a few percent on Earth and are ˜14% below theory in microgravity, demonstrating that the use of equilibrium Langevin forces is appropriate in this nonequilibrium situation.

  19. Quark number fluctuations at finite temperature and finite chemical potential via the Dyson-Schwinger equation approach

    NASA Astrophysics Data System (ADS)

    Xin, Xian-yin; Qin, Si-xue; Liu, Yu-xin

    2014-10-01

    We investigate the quark number fluctuations up to the fourth order in the matter composed of two light flavor quarks with isospin symmetry and at finite temperature and finite chemical potential using the Dyson-Schwinger equation approach of QCD. In order to solve the quark gap equation, we approximate the dressed quark-gluon vertex with the bare one and adopt both the Maris-Tandy model and the infrared constant (Qin-Chang) model for the dressed gluon propagator. Our results indicate that the second, third, and fourth order fluctuations of net quark number all diverge at the critical endpoint (CEP). Around the CEP, the second order fluctuation possesses obvious pump while the third and fourth order ones exhibit distinct wiggles between positive and negative. For the Maris-Tandy model and the Qin-Chang model, we give the pseudocritical temperature at zero quark chemical potential as Tc=146 MeV and 150 MeV, and locate the CEP at (μEq,TE)=(120,124) MeV and (124,129) MeV, respectively. In addition, our results manifest that the fluctuations are insensitive to the details of the model, but the location of the CEP shifts to low chemical potential and high temperature as the confinement length scale increases.

  20. The role of spatial scale and background climate in the latitudinal temperature response to deforestation

    NASA Astrophysics Data System (ADS)

    Li, Yan; De Noblet-Ducoudré, Nathalie; Davin, Edouard L.; Motesharrei, Safa; Zeng, Ning; Li, Shuangcheng; Kalnay, Eugenia

    2016-03-01

    Previous modeling and empirical studies have shown that the biophysical impact of deforestation is to warm the tropics and cool the extratropics. In this study, we use an earth system model of intermediate complexity to investigate how deforestation on various spatial scales affects ground temperature, with an emphasis on the latitudinal temperature response and its underlying mechanisms. Results show that the latitudinal pattern of temperature response depends nonlinearly on the spatial extent of deforestation and the fraction of vegetation change. Compared with regional deforestation, temperature change in global deforestation is greatly amplified in temperate and boreal regions but is dampened in tropical regions. Incremental forest removal leads to increasingly larger cooling in temperate and boreal regions, while the temperature increase saturates in tropical regions. The latitudinal and spatial patterns of the temperature response are driven by two processes with competing temperature effects: decrease in absorbed shortwave radiation due to increased albedo and decrease in evapotranspiration. These changes in the surface energy balance reflect the importance of the background climate in modifying the deforestation impact. Shortwave radiation and precipitation have an intrinsic geographical distribution that constrains the effects of biophysical changes and therefore leads to temperature changes that are spatially varying. For example, wet (dry) climate favors larger (smaller) evapotranspiration change; thus, warming (cooling) is more likely to occur. Our analysis reveals that the latitudinal temperature change largely results from the climate conditions in which deforestation occurs and is less influenced by the magnitude of individual biophysical changes such as albedo, roughness, and evapotranspiration efficiency.

  1. Ultra-fast charge exchange spectroscopy for turbulent ion temperature fluctuation measurements on the DIII-D tokamak (invited).

    PubMed

    Uzun-Kaymak, I U; Fonck, R J; McKee, G R

    2012-10-01

    A novel two-channel, high throughput, high efficiency spectrometer system has been developed to measure impurity ion temperature and toroidal velocity fluctuations associated with long-wavelength turbulence and other plasma instabilities. The spectrometer observes the emission of the n = 8-7 hydrogenic transition of C(+5) ions (λ(air) = 529.06 nm) resulting from charge exchange reactions between deuterium heating beams and intrinsic carbon. Novel features include a large, prism-coupled high-dispersion, volume-phase-holographic transmission grating and high-quantum efficiency, high-gain, low-noise avalanche photodiode detectors that sample emission at 1 MHz. This new diagnostic offers an order-of-magnitude increase in sensitivity compared to earlier ion thermal turbulence measurements. Increased sensitivity is crucial for obtaining enough photon statistics from plasmas with much less impurity content. The irreducible noise floor set by photon statistics sets the ultimate sensitivity to plasma fluctuations. Based on the measured photon flux levels for the entire spectral line, photon noise levels for T̃(i)/T(i) and Ṽ(i)/V(i) of ~1% are expected, while statistical averaging over long data records enables reduction in the detectable plasma fluctuation levels to values less than that. Broadband ion temperature fluctuations are observed to near 200 kHz in an L-mode discharge. Cross-correlation with the local beam emission spectroscopy measurements demonstrates a strong coupling of the density and temperature fields, and enables the cross-phase measurements between density and ion temperature fluctuations. PMID:23126866

  2. Ultra-fast charge exchange spectroscopy for turbulent ion temperature fluctuation measurements on the DIII-D tokamak (invited)

    SciTech Connect

    Uzun-Kaymak, I. U.; Fonck, R. J.; McKee, G. R.

    2012-10-15

    A novel two-channel, high throughput, high efficiency spectrometer system has been developed to measure impurity ion temperature and toroidal velocity fluctuations associated with long-wavelength turbulence and other plasma instabilities. The spectrometer observes the emission of the n= 8-7 hydrogenic transition of C{sup +5} ions ({lambda}{sub air}= 529.06 nm) resulting from charge exchange reactions between deuterium heating beams and intrinsic carbon. Novel features include a large, prism-coupled high-dispersion, volume-phase-holographic transmission grating and high-quantum efficiency, high-gain, low-noise avalanche photodiode detectors that sample emission at 1 MHz. This new diagnostic offers an order-of-magnitude increase in sensitivity compared to earlier ion thermal turbulence measurements. Increased sensitivity is crucial for obtaining enough photon statistics from plasmas with much less impurity content. The irreducible noise floor set by photon statistics sets the ultimate sensitivity to plasma fluctuations. Based on the measured photon flux levels for the entire spectral line, photon noise levels for T(tilde sign){sub i}/T{sub i} and V(tilde sign){sub i}/V{sub i} of {approx}1% are expected, while statistical averaging over long data records enables reduction in the detectable plasma fluctuation levels to values less than that. Broadband ion temperature fluctuations are observed to near 200 kHz in an L-mode discharge. Cross-correlation with the local beam emission spectroscopy measurements demonstrates a strong coupling of the density and temperature fields, and enables the cross-phase measurements between density and ion temperature fluctuations.

  3. Measurement of the dispersion of thermal ion-acoustic fluctuations in high-temperature laser plasmas using multiple-wavelength Thomson scattering.

    PubMed

    Froula, D H; Davis, P; Divol, L; Ross, J S; Meezan, N; Price, D; Glenzer, S H; Rousseaux, C

    2005-11-01

    The dispersion of ion-acoustic fluctuations has been measured using a novel technique that employs multiple color Thomson-scattering diagnostics to measure the frequency spectrum for two separate thermal ion-acoustic fluctuations with significantly different wave vectors. The plasma fluctuations are shown to become dispersive with increasing electron temperature. We demonstrate that this technique allows a time resolved local measurement of electron density and temperature in inertial confinement fusion plasmas. PMID:16383991

  4. Probing environment fluctuations by two-dimensional electronic spectroscopy of molecular systems at temperatures below 5 K

    SciTech Connect

    Rancova, Olga; Abramavicius, Darius; Jankowiak, Ryszard

    2015-06-07

    Two-dimensional (2D) electronic spectroscopy at cryogenic and room temperatures reveals excitation energy relaxation and transport, as well as vibrational dynamics, in molecular systems. These phenomena are related to the spectral densities of nuclear degrees of freedom, which are directly accessible by means of hole burning and fluorescence line narrowing approaches at low temperatures (few K). The 2D spectroscopy, in principle, should reveal more details about the fluctuating environment than the 1D approaches due to peak extension into extra dimension. By studying the spectral line shapes of a dimeric aggregate at low temperature, we demonstrate that 2D spectra have the potential to reveal the fluctuation spectral densities for different electronic states, the interstate correlation of static disorder and, finally, the time scales of spectral diffusion with high resolution.

  5. Fast cosmic microwave background power spectrum estimation of temperature and polarization with Gabor transforms

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.

    2003-08-01

    We extend the analysis of Gabor transforms on a cosmic microwave background temperature map to polarization. We study the temperature and polarization power spectra on the cut sky, the so-called pseudo-power spectra. The transformation kernels relating the full-sky polarization power spectra and the polarization pseudo-power spectra are found to be similar to the kernel for the temperature power spectrum. This fact is used to construct a fast power spectrum estimation algorithm using the pseudo-power spectrum of temperature and polarization as data vectors in a maximum-likelihood approach. Using the pseudo-power spectra as input to the likelihood analysis solves the problem of having to invert huge matrices, which makes the standard likelihood approach infeasible.

  6. Measurement of electron temperature fluctuations using a tunable correlation electron cyclotron emission system on Alcator C-Mod

    SciTech Connect

    Howard, N. T.; Sung, C.; White, A. E.

    2014-11-15

    A tunable correlation electron cyclotron (CECE) system was recently installed on the Alcator C-Mod tokamak to provide local, quantitative measurement of electron temperature fluctuations in the tokamak core. This system represents a significant upgrade from the original CECE system, expanding the measurement capabilities from 4 to 8 total channels, including 2 remotely tunable YIG filters (6–18 GHz; 200 MHz bandwidth). Additional upgrades were made to the optical system to provide enhanced poloidal resolution and allow for measurement of turbulent fluctuations below k{sub θ}ρ{sub s} < 0.3. These expanded capabilities allow for single shot measurement of partial temperature fluctuation profiles in the region ρ = 0.7 − 0.9 (square root of normalized toroidal flux) in a wide variety of plasma conditions. These measurements are currently being used to provide stringent tests of the gyrokinetic model in ongoing model validation efforts. Details of the hardware upgrades, turbulent fluctuation measurements, and ongoing comparisons with simulations are presented.

  7. Measurement of electron temperature fluctuations using a tunable correlation electron cyclotron emission system on Alcator C-Mod.

    PubMed

    Howard, N T; Sung, C; White, A E

    2014-11-01

    A tunable correlation electron cyclotron (CECE) system was recently installed on the Alcator C-Mod tokamak to provide local, quantitative measurement of electron temperature fluctuations in the tokamak core. This system represents a significant upgrade from the original CECE system, expanding the measurement capabilities from 4 to 8 total channels, including 2 remotely tunable YIG filters (6-18 GHz; 200 MHz bandwidth). Additional upgrades were made to the optical system to provide enhanced poloidal resolution and allow for measurement of turbulent fluctuations below kθρs < 0.3. These expanded capabilities allow for single shot measurement of partial temperature fluctuation profiles in the region ρ = 0.7 - 0.9 (square root of normalized toroidal flux) in a wide variety of plasma conditions. These measurements are currently being used to provide stringent tests of the gyrokinetic model in ongoing model validation efforts. Details of the hardware upgrades, turbulent fluctuation measurements, and ongoing comparisons with simulations are presented. PMID:25430224

  8. Fluid-inclusion evidence for past temperature fluctuations in the Kilauea East Rift Zone geothermal area, Hawaii

    USGS Publications Warehouse

    Bargar, K.E.; Keith, T.E.C.; Trusdell, F.A.

    1995-01-01

    Heating and freezing data were obtained for fluid inclusions in hydrothermal quartz, calcite, and anhydrite from several depths in three scientific observation holes drilled along the lower East Rift Zone of Kilauea volcano, Hawaii. Comparison of measured drill-hole temperatures with fluid-inclusion homogenization-temperature (Th) data indicates that only about 15% of the fluid inclusions could have formed under the present thermal conditions. The majority of fluid inclusions studied must have formed during one or more times in the past when temperatures fluctuated in response to the emplacement of nearby dikes and their subsequent cooling. -from Authors

  9. Changes in core electron temperature fluctuations across the ohmic energy confinement transition in Alcator C-Mod plasmas

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A. E.; Howard, N. T.; Oi, C. Y.; Rice, J. E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Mikkelsen, D.; Ernst, D.; Walk, J.; Hughes, J. W.; Irby, J.; Kasten, C.; Hubbard, A. E.; Greenwald, M. J.; the Alcator C-Mod Team

    2013-08-01

    The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge.

  10. Bacterial responses to fluctuations and extremes in temperature and brine salinity at the surface of Arctic winter sea ice.

    PubMed

    Ewert, Marcela; Deming, Jody W

    2014-08-01

    Wintertime measurements near Barrow, Alaska, showed that bacteria near the surface of first-year sea ice and in overlying saline snow experience more extreme temperatures and salinities, and wider fluctuations in both parameters, than bacteria deeper in the ice. To examine impacts of such conditions on bacterial survival, two Arctic isolates with different environmental tolerances were subjected to winter-freezing conditions, with and without the presence of organic solutes involved in osmoprotection: proline, choline, or glycine betaine. Obligate psychrophile Colwellia psychrerythraea strain 34H suffered cell losses under all treatments, with maximal loss after 15-day exposure to temperatures fluctuating between -7 and -25 °C. Osmoprotectants significantly reduced the losses, implying that salinity rather than temperature extremes presents the greater stress for this organism. In contrast, psychrotolerant Psychrobacter sp. strain 7E underwent miniaturization and fragmentation under both fluctuating and stable-freezing conditions, with cell numbers increasing in most cases, implying a different survival strategy that may include enhanced dispersal. Thus, the composition and abundance of the bacterial community that survives in winter sea ice may depend on the extent to which overlying snow buffers against extreme temperature and salinity conditions and on the availability of solutes that mitigate osmotic shock, especially during melting. PMID:24903191

  11. Long dephasing time and high-temperature conductance fluctuations in an open InGaAs quantum dot

    NASA Astrophysics Data System (ADS)

    Hackens, B.; Delfosse, F.; Faniel, S.; Gustin, C.; Boutry, H.; Wallart, X.; Bollaert, S.; Cappy, A.; Bayot, V.

    2002-12-01

    We measure the electron phase-coherence time τφ up to 18 K using universal fluctuations in the low-temperature magnetoconductance of an open InGaAs quantum dot. The temperature dependence of τφ is quantitatively consistent with the two-dimensional model of electron-electron interactions in disordered systems. In our sample, τφ is two to four times larger than previously reported in GaAs quantum dots. We attribute this enhancement to a larger value of the Fermi energy and the lower electron effective mass in our sample. We also observe a distinct type of conductance fluctuation due to ballistic electron focusing inside the dot up to 204 K.

  12. Theoretical Description of the Superconducting State of Nanostructures at Intermediate Temperatures: A Combined Treatment of Collective Modes and Fluctuations

    NASA Astrophysics Data System (ADS)

    Ribeiro, Pedro; García-García, Antonio M.

    2012-03-01

    A rigorous treatment of the combined effect of thermal and quantum fluctuations in a zero-dimensional superconductor is considered one of the most relevant and still-unsolved problems in the theory of nanoscale superconductors. In this Letter, we notice that the divergences that plagued previous calculations are avoided by identifying and treating nonperturbatively a low-energy collective mode. In this way, we obtain for the first time closed expressions for the partition function and the superconducting order parameter which include both types of fluctuation and are valid at any temperature and to leading order in δ/Δ0, where δ is the mean level spacing and Δ0 is the bulk energy gap. Our results pave the way for a quantitative description of superconductivity in nanostructures at finite temperature and pairing in hot nuclei.

  13. A high speed data acquisition system for the analysis of velocity, density, and total temperature fluctuations at transonic speeds

    NASA Technical Reports Server (NTRS)

    Clukey, Steven J.; Jones, Gregory S.; Stainback, P. Calvin

    1988-01-01

    The use of a high-speed Dynamic Data Acquisition System (DDAS) to measure simultaneously velocity, density, and total temperature fluctuations is described. The DDAS is used to automate the acquisition of hot-wire calibration data. The data acquisition, data handling, and data reporting techiques used by DDAS are described. Sample data are used to compare results obtained with the DDAS with those obtained from the FM tape and post-test digitization method.

  14. 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.

  15. Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A. E.; Mikkelsen, D. R.; Greenwald, M.; Holland, C.; Howard, N. T.; Churchill, R.; Theiler, C.

    2016-04-01

    Long wavelength turbulent electron temperature fluctuations (kyρs < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (kyρs ≲ 1.7) performed at r/a ˜ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the "Transport Shortfall" [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].

  16. 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. M.; Hosea, J. C.; LeBlanc, B. P.; Wilson, J. R.; Ryan, P. M.; Domier, C. W.; Luhmann, N. C. Jr.; Yuh, H.; Lee, W.; Park, H.

    2008-08-15

    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{sub perpendicular}{rho}{sub 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.

  17. Short-scale turbulent fluctuations driven by the electron-temperature gradient in the national spherical torus experiment.

    PubMed

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

    2008-08-15

    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 perpendicular rho(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. PMID:18764544

  18. Mosselbay environmental conditions and sea-surface temperature fluctuations during the Late Holocene

    NASA Astrophysics Data System (ADS)

    Hahn, Annette; Andò, Sergio; Frenzel, Peter; Kugel, Martin; Mollenhauer, Gesine; Schefuß, Enno; Zabel, Matthias

    2016-04-01

    our current stage of research, we attribute this to a southward shift of the SHW and a strengthening in Aghulas current speed during this period. Cohen, A.L. and Tyson, P.D., 1995. Sea-surface temperature fluctuations during the Holocene off the south coast of Africa: implications for terrestrial climate and rainfall. The Holocene 5 (3), 304-312.

  19. ON MEASURING THE COSMIC MICROWAVE BACKGROUND TEMPERATURE AT REDSHIFT 0.89

    SciTech Connect

    Sato, M.; Menten, K. M.; Reid, M. J.; Carilli, C. L.

    2013-02-20

    We report on a measurement of the temperature of the cosmic microwave background radiation field, T {sub CMB}, at z = 0.88582 by imaging HC{sub 3}N(3 <- 2) and (5 <- 4) absorption in the foreground galaxy of the gravitationally lens magnified radio source PKS 1830-211 using the Very Long Baseline Array and the phased Very Large Array. Low-resolution imaging of the data yields a value of T {sub rot} = 5.6{sup +2.5} {sub -0.9} K for the rotational temperature, T {sub rot}, which is consistent with the temperature of the cosmic microwave background at the absorber's redshift of 2.73(1 + z) K. However, our high-resolution imaging reveals that the absorption peak position of the foreground gas is offset from the continuum peak position of the synchrotron radiation from PKS 1830-211SW, which indicates that the absorbing cloud is covering only part of the emission from PKS 1830-211, rather than the entire core-jet region. This changes the line-to-continuum ratios, and we find T {sub rot} between 1.1 and 2.5 K, which is lower than the expected value. This shows that previous T {sub rot} measurements could be biased due to unresolved structure.

  20. The effects of cosmic microwave background (CMB) temperature uncertainties on cosmological parameter estimation

    SciTech Connect

    Hamann, Jan; Wong, Yvonne Y Y E-mail: ywong@mppmu.mpg.de

    2008-03-15

    We estimate the effect of the experimental uncertainty in the measurement of the temperature of the cosmic microwave background (CMB) on the extraction of cosmological parameters from future CMB surveys. We find that even for an ideal experiment limited only by cosmic variance up to l=2500 for both the temperature and polarization measurements, the projected cosmological parameter errors are remarkably robust against the uncertainty of 1 mK in the firas CMB temperature monopole measurement. The maximum degradation in sensitivity is 20%, for the baryon density estimate, relative to the case in which the monopole is known infinitely well. While this degradation is acceptable, we note that reducing the uncertainty in the current temperature measurement by a factor of five will bring it down to {approx}1%. We also estimate the effect of the uncertainty in the dipole temperature measurement. Assuming the overall calibration of the data to be dominated by the dipole error of 0.2% from firas, the sensitivity degradation is insignificant and does not exceed 10% in any parameter direction.

  1. A precise measurement of the cosmic microwave background temperature from optical observations of interstellar CN

    NASA Technical Reports Server (NTRS)

    Meyer, D. M.; Jura, M.

    1985-01-01

    Very precise observations (with S/N greater than 2000) of the 3874-angstrom band of interstellar CN toward zeta Per and omicron Per are presented. In the zeta Oph, zeta Per, and omicron Per lines of sight, the saturation-corrected CN line strengths yield respective excitation temperatures of 2.72 plus or minus 0.05 K, 2.76 plus or minus 0.05 K, and 2.78 plus or minus 0.07 K for the J = 0-1 rotational transition at 2.64 mm. By confirming the blackbody character of the cosmic microwave background spectrum at wavelengths near the peak of its flux, the simplest explanation of the background as primeval fireball radiation from a hot bang is reinforced.

  2. Fluctuations at Finite Temperature and Thermodynamics of Mesoscopic RLC Circuit Calculated by Using Generalized Thermal Vacuum State

    NASA Astrophysics Data System (ADS)

    Yuan, Hong-Chun; Xu, Xue-Xiang; Xu, Xue-Fen; Fan, Hong-Yi

    By using the partial trace method and the technique of integration within an ordered product of operators we obtain the explicit expression of the generalized thermal vacuum state (GTVS) for an RLC circuit instead of using the Takahashi-Umezawa approach. According to thermal field dynamics (TFD), namely, the expectation value of physical observables in this GTVS is equivalent to their ensemble average, based on GTVS we successfully derive the quantum fluctuations at nonzero temperature and the thermodynamical relations for the mesoscopic RLC circuit. Our results show that the higher the temperature is, the more quantum noise the RLC circuit exhibits.

  3. Precise measurement of the cosmic microwave background temperature from optical observations of interstellar CN

    SciTech Connect

    Meyer, D.M.; Jura, M.

    1985-10-01

    We present very precise (S/N > 2000) observations of the 3874 A band of interstellar CN toward zeta Per and o Per. In the zeta Oph, zeta Per, and o Per lines of sight, the saturation-corrected CN line strengths yield respective excitation temperatures of 2.72 +- 0.05 K, 2.76 +- 0.05 K, and 2.78 +- 0.07 K for the J = 0--1 rotational transition at 2.64 mm. The excellent agreement among these temperatures confirms the expectation that the cosmic microwave background radiation (CMB) is primarily responsible for populating the excited rotational levels of interstellar CN. With small corrections for the local CN excitation due to electron impact, the J = 0--1 excitation temperatures toward zeta Oph, zeta Per, and o Per are all consistent with a CMB brightness temperature of 2.70 +- 0.04 K at 2.64 mm. This value represents the most precise determination to date of the CMB intensity at any wavelength. In addition, the CN J = 1--2 excitation temperatures toward these objects indicate a CMB temperature of 2.76 +- 0.20 K at 1.32 mm. Our temperatures at 2.64 mm and 1.32 mm are thus consistent with a 2.7 K blackbody spectrum for the CMB and do not support the spectral distortions observed near these wavelengths by Woody and Richards. Indeed, by confirming the blackbody character of the CMB spectrum at wavelengths near the peak of its flux, we have reinforced the simplest explanation of the CMB as primeval fireball radiation from a hot big bang.

  4. Ultrasonic thermometry simulation in a random fluctuating medium: Evidence of the acoustic signature of a one-percent temperature difference.

    PubMed

    Nagaso, M; Moysan, J; Benjeddou, S; Massacret, N; Ploix, M A; Komatitsch, D; Lhuillier, C

    2016-05-01

    We study the development potential of ultrasonic thermometry in a liquid fluctuating sodium environment similar to that present in a Sodium-cooled Fast Reactor, and thus investigate if and how ultrasonic thermometry could be used to monitor the sodium flow at the outlet of the reactor core. In particular we study if small temperature variations in the sodium flow of e.g. about 1% of the sodium temperature, i.e., about 5°C, can have a reliably-measurable acoustic signature. Since to our knowledge no experimental setups are available for such a study, and considering the practical difficulties of experimentation in sodium, we resort to a numerical technique for full wave propagation called the spectral-element method, which is a highly accurate finite-element method owing to the high-degree basis functions it uses. We obtain clear time-of-flight variations in the case of a small temperature difference of one percent in the case of a static temperature gradient as well as in the presence of a random fluctuation of the temperature field in the turbulent flow. The numerical simulations underline the potential of ultrasonic thermometry in such a context. PMID:26921558

  5. Low-Temperature Blackbodies for IR Calibrations in a Medium-Background Environment

    NASA Astrophysics Data System (ADS)

    Ogarev, S. A.; Samoylov, M. L.; Parfentyev, N. A.; Sapritsky, V. I.

    2009-02-01

    Utilization of Earth remote-sensing data to solve scientific and engineering problems within such fields as meteorology and climatology requires precise radiometric calibration of space-borne instruments. High-accuracy calibration equipment in the thermal-IR wavelength range ought to be combined during calibration procedures with the simulation of environmental conditions for space orbit (high vacuum, medium background). For more than 35 years, VNIIOFI has developed and manufactured standard radiation sources in the form of precision blackbodies (BB) functioning within wide ranges of wavelengths and working temperatures. These BBs are the spectral radiance and irradiance calibration devices in the world’s leading space research institutions, such as SDL (USA), DLR (Germany), Keldysh Space Center (Russia), RNIIKP/RISDE (Russia), NEC Toshiba Space Systems (Japan), etc. The paper contains a detailed description of low-temperature precision BBs developed at VNIIOFI. The characteristics of variable-temperature (100 K to 400 K) research-grade extended-area (up to 350 mm) BB models BB100-V1 and BB-80/350 are described (they are intended for radiometric calibrations by comparison with a primary standard source), as well as those that can be used as sources for high-accuracy IR calibration of space-borne and other systems not requiring a vacuum environment. The temperature nonuniformity and stability of these BBs are (0.05 to 0.1) K (cavity-type BB100-V1), and 0.1 % for the (1.5 to 15) μm wavelength region under cryo-vacuum conditions of a medium-background environment.

  6. Constraining the Redshift Evolution of the Cosmic Microwave Background Blackbody Temperature with PLANCK Data.

    NASA Astrophysics Data System (ADS)

    de Martino, I.; Génova-Santos, R.; Atrio-Barandela, F.; Ebeling, H.; Kashlinsky, A.; Kocevski, D.; Martins, C. J. A. P.

    2015-08-01

    We constrain the deviation of adiabatic evolution of the universe using the data on the cosmic microwave background (CMB) temperature anisotropies measured by the Planck satellite and a sample of 481 X-ray selected clusters with spectroscopically measured redshifts. To avoid antenna beam effects, we bring all of the maps to the same resolution. We use a CMB template to subtract the cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ) anisotropies; next, we remove galactic foreground emissions around each cluster and we mask out all known point sources. If the CMB blackbody temperature scales with redshift as T{(z)={T}0(1+z)}1-α , we constrain deviations of adiabatic evolution to be α = -0.007 ± 0.013, consistent with the temperature-redshift relation of the standard cosmological model. This result could suffer from a potential bias δα associated with the CMB template. We quantify it to be | δ α | ≤slant 0.02, with the same sign as the measured value of α. Our result is free from those biases associated with using TSZ selected clusters; it represents the best constraint to date of the temperature-redshift relation of the Big Bang model using only CMB data, confirming previous results.

  7. A real time dynamic data acquisition and processing system for velocity, density, and total temperature fluctuation measurements

    NASA Technical Reports Server (NTRS)

    Clukey, Steven J.

    1991-01-01

    The real time Dynamic Data Acquisition and Processing System (DDAPS) is described which provides the capability for the simultaneous measurement of velocity, density, and total temperature fluctuations. The system of hardware and software is described in context of the wind tunnel environment. The DDAPS replaces both a recording mechanism and a separate data processing system. DDAPS receives input from hot wire anemometers. Amplifiers and filters condition the signals with computer controlled modules. The analog signals are simultaneously digitized and digitally recorded on disk. Automatic acquisition collects necessary calibration and environment data. Hot wire sensitivities are generated and applied to the hot wire data to compute fluctuations. The presentation of the raw and processed data is accomplished on demand. The interface to DDAPS is described along with the internal mechanisms of DDAPS. A summary of operations relevant to the use of the DDAPS is also provided.

  8. Effect of fluctuations on time-averaged multi-line NO-LIF thermometry measurements of the gas-phase temperature

    NASA Astrophysics Data System (ADS)

    Feroughi, Omid M.; Kronemayer, Helmut; Dreier, Thomas; Schulz, Christof

    2015-09-01

    Multi-line NO laser-induced fluorescence (LIF) thermometry enables accurate gas-phase temperature imaging in combustion systems through least-squares fitting of excitation spectra. The required excitation wavelength scan takes several minutes which systematic biases the results in case of temperature fluctuations. In this work, the effect of various types (linear, Gaussian and bimodal) and amplitudes of temperature fluctuations is quantified based on simulated NO-LIF excitation spectra. Temperature fluctuations of less than ±5 % result in a negligible error of less than ±1 % in temperature for all cases. Bimodal temperature distributions have the largest effect on the determined temperature. Symmetric temperature fluctuations around 900 K have a negligible effect. At lower mean temperatures, fluctuations cause a positive bias leading to over-predicted mean temperatures, while at higher temperatures the bias is negative. The results of the theoretical analysis were applied as a guide for interpreting experimental multi-line NO-LIF temperature measurements in a mildly turbulent pilot-plant scale flame reactor dedicated for nanoparticle synthesis.

  9. An Analysis of Recent Measurements of the Temperature of the Cosmic Microwave Background Radiation

    DOE R&D Accomplishments Database

    Smoot, G.; Levin, S. M.; Witebsky, C.; De Amici, G.; Rephaeli, Y.

    1987-07-01

    This paper presents an analysis of the results of recent temperature measurements of the cosmic microwave background radiation (CMBR). The observations for wavelengths longer than 0.1 cum are well fit by a blackbody spectrum at 2.74{+ or -}0.0w K; however, including the new data of Matsumoto et al. (1987) the result is no longer consistent with a Planckian spectrum. The data are described by a Thomson-distortion parameter u=0.021{+ or -}0.002 and temperature 2.823{+ or -}0.010 K at the 68% confidence level. Fitting the low-frequency data to a Bose-Einstein spectral distortion yields a 95% confidence level upper limit of 1.4 x 10{sup -2} on the chemical potential mu{sub 0}. These limits on spectral distortions place restrictions on a number of potentially interesting sources of energy release to the CMBR, including the hot intergalactic medium proposed as the source of the X-ray background.

  10. Marshall N. Rosenbluth Outstanding Doctoral Thesis Award Talk: Simultaneous Measurement of Electron Temperature and Density Fluctuations in the Core of DIII-D Plasmas

    NASA Astrophysics Data System (ADS)

    White, A. E.

    2009-11-01

    Multi-field fluctuation measurements provide opportunities for rigorous comparison between experiment and nonlinear gyrokinetic turbulence simulations. A unique set of diagnostics on DIII-D allows for simultaneous study of local, long-wavelength (0 < kθρs< 0.5) electron temperature and density fluctuations in the core plasma (0.4 < ρ< 0.8). Previous experiments in L-mode indicate that normalized electron temperature fluctuation levels (40 < f < 400,kHz) increase with radius from ˜0.4% at ρ= 0.5 to ˜2% at ρ=0.8, similar to simultaneously measured density fluctuations. Electron cyclotron heating (ECH) is used to increase Te, which increases electron temperature fluctuation levels and electron heat transport in the experiments. In contrast, long wavelength density fluctuation levels change very little. The different responses are consistent with increased TEM drive relative to ITG-mode drive. A new capability at DIII-D is the measurement of phase angle between electron temperature and density fluctuations using coupled correlation electron cyclotron emission radiometer and reflectometer diagnostics. Linear and nonlinear GYRO runs have been used to design validation experiments that focus on measurements of the phase angle. GYRO shows that if Te and ∇Te increase 50% in a beam-heated L-mode plasma (ρ=0.5), then the phase angle between electron temperature and density fluctuations decreases 30%-50% and electron temperature fluctuation levels increase a factor of two more than density fluctuations. Comparisons between these predictions and experimental results will be presented.