Science.gov

Sample records for additional observational constraints

  1. The Probabilistic Admissible Region with Additional Constraints

    NASA Astrophysics Data System (ADS)

    Roscoe, C.; Hussein, I.; Wilkins, M.; Schumacher, P.

    The admissible region, in the space surveillance field, is defined as the set of physically acceptable orbits (e.g., orbits with negative energies) consistent with one or more observations of a space object. Given additional constraints on orbital semimajor axis, eccentricity, etc., the admissible region can be constrained, resulting in the constrained admissible region (CAR). Based on known statistics of the measurement process, one can replace hard constraints with a probabilistic representation of the admissible region. This results in the probabilistic admissible region (PAR), which can be used for orbit initiation in Bayesian tracking and prioritization of tracks in a multiple hypothesis tracking framework. The PAR concept was introduced by the authors at the 2014 AMOS conference. In that paper, a Monte Carlo approach was used to show how to construct the PAR in the range/range-rate space based on known statistics of the measurement, semimajor axis, and eccentricity. An expectation-maximization algorithm was proposed to convert the particle cloud into a Gaussian Mixture Model (GMM) representation of the PAR. This GMM can be used to initialize a Bayesian filter. The PAR was found to be significantly non-uniform, invalidating an assumption frequently made in CAR-based filtering approaches. Using the GMM or particle cloud representations of the PAR, orbits can be prioritized for propagation in a multiple hypothesis tracking (MHT) framework. In this paper, the authors focus on expanding the PAR methodology to allow additional constraints, such as a constraint on perigee altitude, to be modeled in the PAR. This requires re-expressing the joint probability density function for the attributable vector as well as the (constrained) orbital parameters and range and range-rate. The final PAR is derived by accounting for any interdependencies between the parameters. Noting that the concepts presented are general and can be applied to any measurement scenario, the idea

  2. Observational constraints on black hole accretion disks

    NASA Technical Reports Server (NTRS)

    Liang, Edison P.

    1994-01-01

    We review the empirical constraints on accretion disk models of stellar-mass black holes based on recent multiwavelength observational results. In addition to time-averaged emission spectra, the time evolutions of the intensity and spectrum provide critical information about the structure, stability, and dynamics of the disk. Using the basic thermal Keplerian disk paradigm, we consider in particular generalizations of the standard optically thin disk models needed to accommodate the extremely rich variety of dynamical phenomena exhibited by black hole candidates ranging from flares of electron-positron annihilations and quasiperiodic oscillations in the X-ray intensity to X-ray novae activity. These in turn provide probes of the disk structure and global geometry. The goal is to construct a single unified framework to interpret a large variety of black hole phenomena. This paper will concentrate on the interface between basic theory and observational data modeling.

  3. Observational constraints on undulant cosmologies

    SciTech Connect

    Barenboim, Gabriela; Mena Requejo, Olga; Quigg, Chris; /Fermilab

    2005-10-01

    In an undulant universe, cosmic expansion is characterized by alternating periods of acceleration and deceleration. We examine cosmologies in which the dark-energy equation of state varies periodically with the number of e-foldings of the scale factor of the universe, and use observations to constrain the frequency of oscillation. We find a tension between a forceful response to the cosmic coincidence problem and the standard treatment of structure formation.

  4. Observational Constraints on Changing Arctic Methane Emissions

    NASA Astrophysics Data System (ADS)

    Dlugokencky, E. J.; Bruhwiler, L.; Lang, P. M.; Masarie, K.; Crotwell, A. M.; Crotwell, M.; Lowry, D.; Fisher, R. E.; Nisbet, E. G.

    2012-12-01

    Methane (CH4) is the second-most important greenhouse gas influenced by human activities. Its chemistry results in additional indirect climate effects from production of tropospheric O3, which also affects air quality, and stratospheric H2O. Because methane's atmospheric lifetime is relatively short (~9 yr) and ~70% of its emissions are anthropogenic, reductions in its emissions provide a potential cost-effective opportunity to slow the rate of increase of radiative forcing. Some fraction of decreased anthropogenic emissions may be canceled by potentially strong feed-backs to natural emissions. Because natural emissions of CH4 are diffuse, relatively weak, and highly-variable in space and time, quantifying changes for large spatial regions is difficult from small-scale field studies alone. Atmosphere observations at well-chosen sites integrate these emissions over large zonal regions and can be particularly useful for detecting changes in emissions. Paleo-climate studies indicate that CH4 emissions from Arctic wetlands are sensitive to climate and may provide a strong positive feedback as the Arctic warms. Measurements of atmospheric CH4 from the NOAA Global Monitoring Division's, Global Cooperative Air Sampling Network began in 1983. These high-precision observations offer key constraints on changes in Arctic CH4 emissions. During 2007, the CH4 growth rate increased in the Arctic, but was nearly zero during 2008. Use of the data in a chemical transport model suggest anomalous emissions of about 2 Tg CH4 during 2007, but returning to long-term average emissions after that. Another potential source affected by climate is emissions from methane clathrates. Measurements of methane's isotopic composition in the Arctic have been useful in showing that CH4 enhancements in Arctic air result from wetlands, not clathrates. Both potential sources are also constrained by spatial patterns in observed CH4, which indicate that, so far, changes in emissions of Arctic CH4 over the

  5. Observational constraints on K-inflation models

    SciTech Connect

    Li, Sheng; Liddle, Andrew R. E-mail: a.liddle@sussex.ac.uk

    2012-10-01

    We extend the ModeCode software of Mortonson, Peiris and Easther [1] to enable numerical computation of perturbations in K-inflation models, where the scalar field no longer has a canonical kinetic term. Focussing on models where the kinetic and potential terms can be separated into a sum, we compute slow-roll predictions for various models and use these to verify the numerical code. A Markov chain Monte Carlo analysis is then used to impose constraints from WMAP7 data on the addition of a term quadratic in the kinetic energy to the Lagrangian of simple chaotic inflation models. For a quadratic potential, the data do not discriminate against addition of such a term, while for a quartic (λφ{sup 4}) potential inclusion of such a term is actually favoured. Overall, constraints on such a term from present data are found to be extremely weak.

  6. Placing Observational Constraints on Massive Star Models

    NASA Astrophysics Data System (ADS)

    Rosenfield, Philip

    2011-10-01

    The lives and deaths of massive stars are intricately linked to the evolution of galaxies. Yet, despite their integral importance to understanding galaxy evolution, models of massive stars are inconsistent with observations. These uncertainties can be traced to limited observational constraints available for improving massive star models. A sensitive test of the underlying physics of massive stars, e.g., convection, rotation, and mass loss is to measure the ratio of blue core helium burning stars {BHeB} to red core helium burning stars {RHeB}, 5-20Msun stars in the stage evolution immediately following the main sequence. Even the most sophisticated models cannot accurately predict the observed ratio over a range of metallicities, suggesting an insufficient understanding of the underlying physics. However, observational measurements of this ratio over a wide range of environments would provide substantial constraints on the physical parameters governing the evolution of all stars >5 Msun.We propose to place stringent observational constraints on the physics of massive star evolution by uniformly measuring the B/R HeB ratio in a wide range of galaxies. The HST archive contains high quality optical imaging of resolved stellar populations of dozens of nearby galaxies. From the ANGST program, we identified 38 galaxies, spanning 2 dex in metallicity that have significant BHeB and RHeB populations. Using this sample, we will empirically characterize the colors of the BHeB and RHeB sequences as a function of luminosity and metallicity, measure the B/R ratio, and constrain the lifetimes of the BHeB and RHeBs in the Padova stellar evolution models and the Cambridge STARS code.

  7. Observational constraints on assisted k-inflation

    SciTech Connect

    Ohashi, Junko; Tsujikawa, Shinji

    2011-05-15

    We study observational constraints on the assisted k-inflation models in which multiple scalar fields join an attractor characterized by an effective single field {phi}. This effective single-field system is described by the Lagrangian P=Xg(Y), where X is the kinetic energy of {phi}, {lambda} is a constant, and g is an arbitrary function in terms of Y=Xe{sup {lambda}{phi}}. Our analysis covers a wide variety of k-inflation models such as dilatonic ghost condensate, Dirac-Born-Infeld field, and tachyon, as well as the canonical field with an exponential potential. We place observational bounds on the parameters of each model from the WMAP 7yr data combined with baryon acoustic oscillations and the Hubble constant measurement. Using the observational constraints of the equilateral non-Gaussianity parameter f{sub NL}{sup equil}, we further restrict the allowed parameter space of dilatonic ghost condensate and Dirac-Born-Infeld models. We extend the analysis to more general models with several different choices of g(Y) and show that the models such as g(Y)=c{sub 0}+c{sub p}Y{sup p} (p{>=}3) are excluded by the joint data analysis of the scalar/tensor spectra and primordial non-Gaussianities.

  8. Weighting climate model projections using observational constraints

    PubMed Central

    Gillett, Nathan P.

    2015-01-01

    Projected climate change integrates the net response to multiple climate feedbacks. Whereas existing long-term climate change projections are typically based on unweighted individual climate model simulations, as observed climate change intensifies it is increasingly becoming possible to constrain the net response to feedbacks and hence projected warming directly from observed climate change. One approach scales simulated future warming based on a fit to observations over the historical period, but this approach is only accurate for near-term projections and for scenarios of continuously increasing radiative forcing. For this reason, the recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) included such observationally constrained projections in its assessment of warming to 2035, but used raw model projections of longer term warming to 2100. Here a simple approach to weighting model projections based on an observational constraint is proposed which does not assume a linear relationship between past and future changes. This approach is used to weight model projections of warming in 2081–2100 relative to 1986–2005 under the Representative Concentration Pathway 4.5 forcing scenario, based on an observationally constrained estimate of the Transient Climate Response derived from a detection and attribution analysis. The resulting observationally constrained 5–95% warming range of 0.8–2.5 K is somewhat lower than the unweighted range of 1.1–2.6 K reported in the IPCC AR5. PMID:26438283

  9. Venus surface mineralogy - Observational and theoretical constraints

    NASA Technical Reports Server (NTRS)

    Fegley, Bruce, Jr.; Treiman, Allan H.; Sharpton, Virgil L.

    1992-01-01

    Earth-based, earth-orbital, and spacecraft observations of the atmosphere and surface of Venus, thermodynamic models of atmosphere-lithosphere interactions, and where available kinetic data on relevant gas-solid reactions to place constraints on the mineralogy of the surface of Venus are used. Which minerals and mineral assemblages are stable on the surface of Venus and which, if any, of these minerals are involved in controlling the abundances of reactive gases in the atmosphere of Venus. It is concluded by identifying key issues facing us today about the mineralogy and geochemistry of the surface of Venus and suggest experimental, observational, and theoretical studies that can improve knowledge of these important questions are discussed.

  10. Observational Constraints on Stellar Flares and Prominences

    NASA Astrophysics Data System (ADS)

    Aarnio, Alicia

    2016-07-01

    Multi-wavelength surveys have catalogued a wealth of stellar flare data for stars representing a broad range of masses and ages. Young solar analogs inform our understanding of the Sun's evolution and the influence of its activity on early solar system formation, while field star observations allow us to place its current activity into context within a statistical ensemble of main-sequence G-type stars. At the same time, stellar observations probe a variety of interior and coronal conditions, providing constraints on models of equilibrium (and loss thereof!) for magnetic structures. In this review, I will focus on our current understanding of stellar flares, prominences, and coronal mass ejections as a function of stellar parameters. As our interpretation of stellar data relies heavily on solar-stellar analogy, I will explore how far into extreme stellar parameter spaces this comparison can be invoked.

  11. Observational constraints on finite scale factor singularities

    SciTech Connect

    Denkiewicz, Tomasz

    2012-07-01

    We discuss the combined constraints on a Finite Scale Factor Singularity (FSF) universe evolution scenario, which come from the shift parameter R, baryon acoustic oscillations (BAO) A, and from the type Ia supernovae. We show that observations allow existence of such singularities in the 2 × 10{sup 9} years in future (at 1σ CL) which is much farther than a Sudden Future Singularity (SFS), and that at the present moment of the cosmic evolution, one cannot differentiate between cosmological scenario which allow finite scale factor singularities and the standard ΛCDM dark energy models. We also show that there is an allowed value of m = 2/3 within 1σ CL, which corresponds to a dust-filled Einstein-de-Sitter universe limit of the early time evolution and so it is pasted into a standard early-time scenario.

  12. Disk Dispersal: Theoretical Understanding and Observational Constraints

    NASA Astrophysics Data System (ADS)

    Gorti, U.; Liseau, R.; Sándor, Z.; Clarke, C.

    2016-05-01

    Protoplanetary disks dissipate rapidly after the central star forms, on time-scales comparable to those inferred for planet formation. In order to allow the formation of planets, disks must survive the dispersive effects of UV and X-ray photoevaporation for at least a few Myr. Viscous accretion depletes significant amounts of the mass in gas and solids, while photoevaporative flows driven by internal and external irradiation remove most of the gas. A reasonably large fraction of the mass in solids and some gas get incorporated into planets. Here, we review our current understanding of disk evolution and dispersal, and discuss how these might affect planet formation. We also discuss existing observational constraints on dispersal mechanisms and future directions.

  13. Observational constraints on monomial warm inflation

    NASA Astrophysics Data System (ADS)

    Visinelli, Luca

    2016-07-01

    Warm inflation is, as of today, one of the best motivated mechanisms for explaining an early inflationary period. In this paper, we derive and analyze the current bounds on warm inflation with a monomial potential U propto phip, using the constraints from the PLANCK mission. In particular, we discuss the parameter space of the tensor-to-scalar ratio r and the potential coupling λ of the monomial warm inflation in terms of the number of e-folds. We obtain that the theoretical tensor-to-scalar ratio r ~ 10‑8 is much smaller than the current observational constrain r lesssim 0.12, despite a relatively large value of the field excursion Δ phi ~ 0.1MPl. Warm inflation thus eludes the Lyth bound set on the tensor-to-scalar ratio by the field excursion.

  14. Observational constraints to a unified cosmological model

    NASA Astrophysics Data System (ADS)

    Cuzinatto, Rodrigo R.; de Morais, Eduardo M.; Medeiros, Leo G.

    2016-01-01

    We propose a phenomenological unified model (UM) for dark matter and dark energy based on an equation of state parameter w that scales with the arctan of the redshift. The free parameters of the model are three constants: Ωb0, α and β. Parameter α dictates the transition rate between the matter dominated era and the accelerated expansion period. The ratio β/α gives the redshift of the equivalence between both regimes. Cosmological parameters are fixed by observational data from primordial nucleosynthesis (PN), supernovae of the type Ia (SNIa), gamma-ray bursts (GRBs) and baryon acoustic oscillations (BAOs). The calibration of the 138 GRB events is performed using the 580 SNIa of the Union2.1 data set and a new set of 79 high-redshift GRB is obtained. The various sets of data are used in different combinations to constraint the parameters through statistical analysis. The UM is compared to the ΛCDM model and their differences are emphasized.

  15. Constraint effects observed in crack initiation stretch

    SciTech Connect

    Lambert, D.M.; Ernst, H.A.

    1995-12-31

    The current paper characterizes constraint in fracture: J-modified resistance (Jr) curves were developed for two tough structural materials, 6061-T651 (aluminum) and IN718-STA1 (nickel-base superalloy). A wide variety of configurations was tested to consider load configurations from bending to tension including three specimen types (compact tension, center-crack tension, and single-edge notched tension), and a range of ligament lengths and thicknesses, as well as side-grooved and smooth-sided ligaments. The Jr curves exhibited an inflection point after some crack extension, and the data were excluded beyond the inflection. Qualified Jr curves for the two materials showed similar behavior, but R-curves were identical for equal ligament length-to-thickness ratio (RL), for the aluminum alloy, with increasing slope for increasing RL, while for the nickel, the resistance curves aligned for equal ligament thickness, B, and the slope increased for decreasing B. Displacements at the original crack tip (CToD) were recorded throughout the test for several specimens. CToD-versus-crack extension curves were developed, and data were excluded beyond the inflection point (as with the Jr curves). The data collapsed into two distinct curves, thought to represent the surface, plane stress effect and the central, plane strain effect. This was observed for both materials. A technique called profiling is presented for the aluminum alloy only, where the crack face displacements are recorded at the final point of the test as a function of the position throughout the crack cavity, along with an effort to extract the observations in a usable form. Displacements were consistent throughout the cross-section at and behind the original crack tip. In the region where the crack grew, this displacement was developed by a combination of stretch and crack growth. The stretch required to initiate crack extension was a function of the depth beneath the surface into the cross-section.

  16. Additional constraints on circumstellar disks in the Trapezium Cluster

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.; Prosser, Charles F.; Hartmann, Lee; Mccaughrean, Mark J.

    1994-01-01

    We discuss new constraints on the population of compact ionized sources in the Trapezium Cluster thought to arise from the ionization by the central OB stars of circumstellar disks around low-mass pre-main sequence stars. We present new HST Planetary Camera observations of two of these candidate disk sources, resolving extended nebulosity around them. One source shows a small-scale (greater than 100 AU) bow-shock structure, previously seen on larger scales by O'Dell et al. We show that the circumstellar disk model is the most likely one for the majority of sources, although it remains plausible that some of the larger objects could be equilibrium globules. We combine the most complete censuses of compact radio sources and stars in the core region to derive the fraction of the stellar population that may be associated with a circumstellar disk. Our estimate of 25-75 percent is comparable to that found for PMS stars in the Taurus-Auriga dark clouds, indicating that the dense cluster environment of the Trapezium has not drastically reduced the frequency of disks seen around pre-main sequence stars.

  17. EINSTEIN-ÆTHER Gravity:. Theory and Observational Constraints

    NASA Astrophysics Data System (ADS)

    Jacobson, Ted

    2008-03-01

    Einstein-æther theory is general relativity coupled to a dynamical unit timelike vector field. A brief review of current theoretical understanding and observational constraints on the four coupling parameters of the theory is given.

  18. Observational constraints on Tachyon and DBI inflation

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Liddle, Andrew R.

    2014-03-01

    We present a systematic method for evaluation of perturbation observables in non-canonical single-field inflation models within the slow-roll approximation, which allied with field redefinitions enables predictions to be established for a wide range of models. We use this to investigate various non-canonical inflation models, including Tachyon inflation and DBI inflation. The Lambert Script W function will be used extensively in our method for the evaluation of observables. In the Tachyon case, in the slow-roll approximation the model can be approximated by a canonical field with a redefined potential, which yields predictions in better agreement with observations than the canonical equivalents. For DBI inflation models we consider contributions from both the scalar potential and the warp geometry. In the case of a quartic potential, we find a formula for the observables under both non-relativistic (sound speed cs2 ~ 1) and relativistic behaviour (cs2 ll 1) of the scalar DBI inflaton. For a quadratic potential we find two branches in the non-relativistic cs2 ~ 1 case, determined by the competition of model parameters, while for the relativistic case cs2 → 0, we find consistency with results already in the literature. We present a comparison to the latest Planck satellite observations. Most of the non-canonical models we investigate, including the Tachyon, are better fits to data than canonical models with the same potential, but we find that DBI models in the slow-roll regime have difficulty in matching the data.

  19. Infrared spectroscopy of exoplanets: observational constraints.

    PubMed

    Encrenaz, Thérèse

    2014-04-28

    The exploration of transiting extrasolar planets is an exploding research area in astronomy. With more than 400 transiting exoplanets identified so far, these discoveries have made possible the development of a new research field, the spectroscopic characterization of exoplanets' atmospheres, using both primary and secondary transits. However, these observations have been so far limited to a small number of targets. In this paper, we first review the advantages and limitations of both primary and secondary transit methods. Then, we analyse what kind of infrared spectra can be expected for different types of planets and discuss how to optimize the spectral range and the resolving power of the observations. Finally, we propose a list of favourable targets for present and future ground-based observations. PMID:24664918

  20. Infrared spectroscopy of exoplanets: observational constraints

    PubMed Central

    Encrenaz, Thérèse

    2014-01-01

    The exploration of transiting extrasolar planets is an exploding research area in astronomy. With more than 400 transiting exoplanets identified so far, these discoveries have made possible the development of a new research field, the spectroscopic characterization of exoplanets' atmospheres, using both primary and secondary transits. However, these observations have been so far limited to a small number of targets. In this paper, we first review the advantages and limitations of both primary and secondary transit methods. Then, we analyse what kind of infrared spectra can be expected for different types of planets and discuss how to optimize the spectral range and the resolving power of the observations. Finally, we propose a list of favourable targets for present and future ground-based observations. PMID:24664918

  1. Observational constraints on Tachyon and DBI inflation

    SciTech Connect

    Li, Sheng; Liddle, Andrew R. E-mail: arl@roe.ac.uk

    2014-03-01

    We present a systematic method for evaluation of perturbation observables in non-canonical single-field inflation models within the slow-roll approximation, which allied with field redefinitions enables predictions to be established for a wide range of models. We use this to investigate various non-canonical inflation models, including Tachyon inflation and DBI inflation. The Lambert W function will be used extensively in our method for the evaluation of observables. In the Tachyon case, in the slow-roll approximation the model can be approximated by a canonical field with a redefined potential, which yields predictions in better agreement with observations than the canonical equivalents. For DBI inflation models we consider contributions from both the scalar potential and the warp geometry. In the case of a quartic potential, we find a formula for the observables under both non-relativistic (sound speed c{sub s}{sup 2} ∼ 1) and relativistic behaviour (c{sub s}{sup 2} || 1) of the scalar DBI inflaton. For a quadratic potential we find two branches in the non-relativistic c{sub s}{sup 2} ∼ 1 case, determined by the competition of model parameters, while for the relativistic case c{sub s}{sup 2} → 0, we find consistency with results already in the literature. We present a comparison to the latest Planck satellite observations. Most of the non-canonical models we investigate, including the Tachyon, are better fits to data than canonical models with the same potential, but we find that DBI models in the slow-roll regime have difficulty in matching the data.

  2. Observational Constraints on Submillimeter Dust Opacity

    NASA Astrophysics Data System (ADS)

    Shirley, Yancy L.; Huard, Tracy L.; Pontoppidan, Klaus M.; Wilner, David J.; Stutz, Amelia M.; Bieging, John H.; Evans, Neal J., II

    2011-02-01

    Infrared extinction maps and submillimeter dust continuum maps are powerful probes of the density structure in the envelope of star-forming cores. We make a direct comparison between infrared and submillimeter dust continuum observations of the low-mass Class 0 core, B335, to constrain the ratio of submillimeter to infrared opacity (κsmm/κir) and the submillimeter opacity power-law index (κ vprop λ-β). Using the average value of theoretical dust opacity models at 2.2 μm, we constrain the dust opacity at 850 and 450 μm. Using new dust continuum models based upon the broken power-law density structure derived from interferometric observations of B335 and the infall model derived from molecular line observations of B335, we find that the opacity ratios are \\frac{\\kappa _{850}}{\\kappa _{2.2}} = (3.21{--}4.80)^{+0.44}_{-0.30} \\times 10^{-4} and \\frac{\\kappa _{450}}{\\kappa _{2.2}} = (12.8{--}24.8)^{+2.4}_{-1.3} \\times 10^{-4}with a submillimeter opacity power-law index of βsmm = (2.18-2.58)+0.30 -0.30. The range of quoted values is determined from the uncertainty in the physical model for B335. For an average 2.2 μm opacity of 3800 ± 700 cm2 g-1, we find a dust opacity at 850 and 450 μm of κ850 = (1.18-1.77)+0.36 -0.24 and κ450 = (4.72-9.13)+1.9 -0.98 cm2 g-1 of dust. These opacities are from (0.65-0.97)κOH5 850 of the widely used theoretical opacities of Ossenkopf and Henning for coagulated ice grains with thin mantles at 850 μm.

  3. Primordial helium abundance from CMB: A constraint from recent observations and a forecast

    SciTech Connect

    Ichikawa, Kazuhide; Sekiguchi, Toyokazu; Takahashi, Tomo

    2008-08-15

    We studied a constraint on the primordial helium abundance Y{sub p} from current and future observations of CMB. Using the currently available data from WMAP, ACBAR, CBI, and BOOMERANG, we obtained the constraint as Y{sub p}=0.25{sub -0.07}{sup +0.10} at 68% confidence level. We also provide a forecast for the Planck experiment using the Markov chain Monte Carlo approach. In addition to forecasting the constraint on Y{sub p}, we investigate how assumptions for Y{sub p} affect constraints on the other cosmological parameters.

  4. Observational and Model Constraints on Glacial Erosion

    NASA Astrophysics Data System (ADS)

    Ehlers, T. A.; Enkelmann, E.; Yanites, B. J.

    2012-12-01

    Quantifying the controls on glacial erosion over geologic timescales is necessary to understand the role of Cenozoic climate change on the development of modern mountain belts. Unfortunately, understanding the spatial distribution of glacial erosion during repeated glaciations has proven difficult. We present results that integrate bedrock and detrital thermochronometer cooling ages with a glacial landscape evolution model. We use this to quantify the spatial distribution and temporal variability of glacial erosion in the Coast Mountains, British Columbia, Canada. A total of 100 apatite (U-Th)/He and 106 fission track single grain ages are presented from modern outwash of the Tiedemann Glacier whose catchment elevations range from 530-3960 m a.s.l.. Detrital thermochronometer ages utilize the tendency of thermochronometer cooling ages to increase with elevation and provide a sediment tracer for the elevation that eroded sediment is derived from. Bedrock ages used include 79 apatite (U-Th)/He ages collected in multiple catchments. Erosion rates derived from bedrock ages are compared to predicted erosion rates from a shallow-ice approximation glacial landscape evolution model of the region. Results from the observed distribution of detrital ages indicate that maximum glacial erosion occurs between elevations of 1200-1800m. Furthermore, near-uniform erosion is documented beneath the glacier with nearly all sediment derived from between elevations of 650- 3000 m a.s.l. Second, comparison of erosion rates derived from bedrock thermochronometer ages with the landscape evolution model suggest that a linear glacial sliding velocity is the primary control on erosion (r2=0.6). This result is important as it provides observational validation of the linear slide velocity erosion rule for million-year timescales. Finally, comparison of model and thermochronometer derived erosion rates reveals that active subglacial erosion occurs for only ~10-20% of a glacial-interglacial cycle

  5. Observational constraints on the composition of exoplanets

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Tinetti, G.; Swain, M. R.; Deroo, P.; Cunha, K.; Schuler, S.; Freedman, R.

    2011-10-01

    Two forms of exoplanetary spectra can be measured. The primary eclipse provides a transmission spectra of the exoplanet's limb as the planet passes in front of the star. The secondary eclipse measures the emission of mainly the planet's dayside atmosphere from the planet plus star's emission minus the emission of star alone, when it eclipses the planet. In the past 3 years, infrared transmission and emission spectroscopy have revealed the presence of the primary carbon and oxygen species (CH4, CO2, CO, and H2O). Yet, efforts to constrain the abundances of these molecules are hindered by degenerate effects of the temperature and composition in the emission spectra, and the composition and assumed radius in the transmission spectrum. These degeneracies lead to derived mixing ratios that span several orders of magnitude. This talk will discuss the correlations in the degenerate solutions that result from the radiative transfer analyses of both emission and transmission spectroscopy. We present an analysis of primary and secondary transit observations of HD209458b's optical to infrared spectra, and correlate the degenerate effects of the atmospheric parameters using a principal components analysis to better constrain the atmospheric composition of the exoplanet. The derived oxygen and carbon composition of the HD209458b's atmosphere are considered in conjunction with the primary star's composition in order to start to address questions regarding the evolution of the exoplanet.

  6. Observational constraints on the global atmospheric budget of ethanol

    NASA Astrophysics Data System (ADS)

    Naik, V.; Fiore, A. M.; Horowitz, L. W.; Singh, H. B.; Wiedinmyer, C.; Guenther, A.; de Gouw, J. A.; Millet, D. B.; Goldan, P. D.; Kuster, W. C.; Goldstein, A.

    2010-01-01

    Energy security and climate change concerns have led to the promotion of biomass-derived ethanol, an oxygenated volatile organic compound (OVOC), as a substitute for fossil fuels. Although ethanol is ubiquitous in the troposphere, our knowledge of its current atmospheric budget and distribution is limited. Here, for the first time we use a global chemical transport model in conjunction with atmospheric observations to place constraints on the ethanol budget, noting that additional measurements of ethanol (and its precursors) are still needed to enhance confidence in our estimated budget. Global sources of ethanol in the model include 5.0 Tg yr-1 from industrial sources and biofuels, 9.2 Tg yr-1 from terrestrial plants, ~0.5 Tg yr-1 from biomass burning, and 0.05 Tg yr-1 from atmospheric reactions of the ethyl peroxide radical (C2H5O2) with itself and with the methyl peroxide radical (CH3O2). The resulting atmospheric lifetime of ethanol in the model is 2.8 days. Gas-phase oxidation by hydroxyl radical (OH) is the primary global sink of ethanol in the model (65%), followed by dry deposition to land (25%), and wet deposition (10%). Over continental areas, ethanol concentrations predominantly reflect direct anthropogenic and biogenic emission sources. Uncertainty in the biogenic ethanol emissions estimated at a factor of three may contribute to the 50% model underestimate of observations in the North American boundary layer. Furthermore, current levels of ethanol measured in remote atmospheres are an order of magnitude larger than those explained by surface sources or by in-situ atmospheric production from observed precursor hydrocarbons in the model, suggesting a major gap in understanding. Stronger constraints on the budget and distribution of ethanol and other VOCs are a critical step towards assessing the impacts of increasing use of ethanol as a fuel.

  7. Observational constraints on the global atmospheric budget of ethanol

    NASA Astrophysics Data System (ADS)

    Naik, V.; Fiore, A. M.; Horowitz, L. W.; Singh, H. B.; Wiedinmyer, C.; Guenther, A.; de Gouw, J. A.; Millet, D. B.; Goldan, P. D.; Kuster, W. C.; Goldstein, A.

    2010-06-01

    Energy security and climate change concerns have led to the promotion of biomass-derived ethanol, an oxygenated volatile organic compound (OVOC), as a substitute for fossil fuels. Although ethanol is ubiquitous in the troposphere, our knowledge of its current atmospheric budget and distribution is limited. Here, for the first time we use a global chemical transport model in conjunction with atmospheric observations to place constraints on the ethanol budget, noting that additional measurements of ethanol (and its precursors) are still needed to enhance confidence in our estimated budget. Global sources of ethanol in the model include 5.0 Tg yr-1 from industrial sources and biofuels, 9.2 Tg yr-1 from terrestrial plants, ~0.5 Tg yr-1 from biomass burning, and 0.05 Tg yr-1 from atmospheric reactions of the ethyl peroxy radical (C2H5O2) with itself and with the methyl peroxy radical (CH3O2). The resulting atmospheric lifetime of ethanol in the model is 2.8 days. Gas-phase oxidation by the hydroxyl radical (OH) is the primary global sink of ethanol in the model (65%), followed by dry deposition (25%), and wet deposition (10%). Over continental areas, ethanol concentrations predominantly reflect direct anthropogenic and biogenic emission sources. Uncertainty in the biogenic ethanol emissions, estimated at a factor of three, may contribute to the 50% model underestimate of observations in the North American boundary layer. Current levels of ethanol measured in remote regions are an order of magnitude larger than those in the model, suggesting a major gap in understanding. Stronger constraints on the budget and distribution of ethanol and OVOCs are a critical step towards assessing the impacts of increasing the use of ethanol as a fuel.

  8. Dust Around Herbig Ae Stars: Additional Constraints from their Photometric and Polarimetric Variability

    NASA Technical Reports Server (NTRS)

    Krivova, N. A.; Ilin, V. B.; Fischer, O.

    1996-01-01

    For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul, etc), the effects of circumstellar dust include: excess infrared emission, anomalous ultraviolet extinction, the 'blueing' of the stars in minima accompanying by an increase of intrinsic polarization. Using a Monte-Carlo code for polarized radiation transfer we have simulated these effects and compared the results obtained for different models with the observational data available. We found that the photometric and polarimetric behavior of the stars provided essential additional constraints on the circumstellar dust models. The models with spheroidal shell geometry and compact (non-fluffy) dust grains do not appear to be able to explain all the data.

  9. Observational constraints on the energy scale of inflation

    NASA Astrophysics Data System (ADS)

    Guo, Zong-Kuan; Schwarz, Dominik J.; Zhang, Yuan-Zhong

    2011-04-01

    Determining the energy scale of inflation is crucial to understand the nature of inflation in the early universe. Assuming a power-law power spectrum of primordial curvature perturbations, we place observational constraints on the energy scale of the observable part of the inflaton potential by combining the 7-year Wilkinson Microwave Anisotropy Probe data with distance measurements from the baryon acoustic oscillations in the distribution of galaxies and the Hubble constant measurement. Our analysis provides an upper limit on this energy scale, 2.3×1016GeV at 95% confidence level. Moreover, we forecast the sensitivity and constraints achievable by the Planck experiment by performing Monte Carlo studies on simulated data. Planck could significantly improve the constraints on the energy scale of inflation and on the shape of the inflaton potential.

  10. Transition redshift in f (T ) cosmology and observational constraints

    NASA Astrophysics Data System (ADS)

    Capozziello, Salvatore; Luongo, Orlando; Saridakis, Emmanuel N.

    2015-06-01

    We extract constraints on the transition redshift ztr , determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of f (T ) gravity. In particular, employing cosmography we obtain bounds on the viable f (T ) forms and their derivatives. Since this procedure is model independent, as long as the scalar curvature is fixed, we are able to determine intervals for ztr . In this way we guarantee that the Solar-System constraints are preserved and, moreover, we extract bounds on the transition time and the free parameters of the scenario. We find that the transition redshifts predicted by f (T ) cosmology, although compatible with the standard Λ CDM predictions, are slightly smaller. Finally, in order to obtain observational constraints on f (T ) cosmology, we perform a Monte Carlo fitting using supernova data, involving the most recent Union 2.1 data set.

  11. Observational Constraints on the Global Budget of Ethanol

    NASA Astrophysics Data System (ADS)

    Naik, V.; Fiore, A. M.; Horowitz, L. W.; Singh, H. B.; Wiedinmyer, C.; Guenther, A. B.; de Gouw, J.; Millet, D.; Levy, H.; Oppenheimer, M.

    2007-12-01

    Ethanol, an oxygenated volatile organic compound (OVOC), is used extensively as a motor fuel and fuel additive to promote clean combustion. Ethanol can affect the oxidizing capacity and the ozone-forming potential of the atmosphere. Limited available atmospheric observations suggest a global background atmospheric ethanol mixing ratio of about 20 pptv, with values up to 3 ppbv near source regions; however, the atmospheric distribution and budget of ethanol remain poorly understood. Here, we use the global three-dimensional chemical transport model MOZART-4 to investigate the global ethanol distribution and budget, and place constraints on the budget by evaluating the model with atmospheric observations. We implement a global ethanol source of 14.7 Tg yr-1 in the model consisting of biogenic emissions (9.2 Tg yr-1), industrial/anthropogenic emissions (3.2 Tg yr-1), emissions from biofuels (1.8 Tg yr-1), biomass burning emissions (0.5 Tg yr-1), and a secondary source from atmospheric production (0.056 Tg yr-1). Gas-phase oxidation by the hydroxyl radical accounts for 66% of the global sink of ethanol in the model, dry deposition 9%, and wet scavenging 25%. The simulation yields a global mean ethanol burden of 0.11 Tg and an atmospheric lifetime of 3 days. The simulated boundary layer mean ethanol concentrations underestimate observations from field campaigns over the United States by 50%, downwind of Asia by 76% and over the remote Pacific Ocean by 86%. Because of the short lifetime of ethanol, the model discrepancy over remote tropical regions cannot be attributed to an underestimate of surface emissions over continents. In these regions, the dominant model source is secondary atmospheric production, from the reaction of the ethyl peroxy radical (C2H5O2) either with itself or with the methyl peroxy radical (CH3O2). A ~500-fold increase in this diffuse source (to ~30 Tg yr-1) distributed uniformly throughout the troposphere would largely correct the observation

  12. CMB topography and electrical conductivity as additional constraints for the lowermost mantle thermo-chemical structure

    NASA Astrophysics Data System (ADS)

    Deschamps, F.; Yin, Y.; Tackley, P. J.

    2013-12-01

    A variety of seismic observations, including tomographic models, indicate that the lowermost mantle is strongly heterogeneous. Seismic observations further support a thermo-chemical origin for the large scale heterogeneities. In particular, the large low-shear wave velocity provinces (LLSVP) observed by global tomographic images are better explained by a combination of thermal and chemical anomalies. Despite the accuracy of seismic information, uncertainties and trade-off still prevent the determination of a detailed lower mantle thermo-chemical structure. For instance, the nature of chemical heterogeneities and the exact role played by the post-perovskite phase transition are still debated. Additional constraints are needed to discriminate between the possible models of structure and dynamics of the lower mantle. Here, we consider two potential additional constraints, the electrical conductivity and the dynamic topography at the core-mantle boundary (CMB). Unlike density and seismic velocities, electrical conductivity increases with temperature. In addition, it strongly varies with the iron and silicate content. Using appropriate mineral physics data, we calculated a 3D distribution of electrical conductivity in lower mantle from the thermo-chemical structure inferred by probabilistic tomography, which maps iron and silicate excess in the LLSVP. In the lowermost mantle, we observe a belt of high conductivity, with maximum values around 20 S/m located in the LLSVP. Such a belt may trigger electric currents in the lowermost mantle and induce magnetic field variations with period of one year or more. It may thus be seen by global models of electrical conductivity. Unfortunately, such models do not sample yet regions deeper than 2000 km. A second, independent constraint we explored is the dynamic topography at the CMB. We used stagYY to calculate the dynamic topography associated with several models of thermo-chemical convection, and observe strong differences

  13. Molecular Observation of Constraint Release in Polymer Melts

    SciTech Connect

    Zamponi, M.; Wischnewski, A.; Monkenbusch, M.; Willner, L.; Richter, D.; Likhtman, A.E.; Kali, G.; Farago, B.

    2006-06-16

    The dynamics of binary polymer blends of few labeled long chains in successively shorter matrix chains has been investigated by neutron spin echo (NSE) spectroscopy. For the first time the effect of constraint release on the chain relaxation has been directly observed on a microscopic scale. Decreasing the matrix chain length reduces the topological confinement until unconfined Rouse motion is observed, when the matrix chains are too short to confine the long chain in a tube. Whereas an analytical description of the effect is not yet available, a new simulation based on the slip-link model shows perfect agreement with the NSE data over the full range of matrix molecular weights.

  14. Constraints on generalized dark energy from recent observations

    SciTech Connect

    Ichiki, Kiyotomo; Takahashi, Tomo

    2007-06-15

    Effects of a generalized dark energy fluid are investigated on cosmic density fluctuations such as a cosmic microwave background. As a general dark energy fluid, we take into consideration the possibility of the anisotropic stress for dark energy, which has not been discussed much in the literature. We comprehensively study its effects on the evolution of density fluctuations along with that of the nonadiabatic pressure fluctuation of dark energy, then give constraints on such a generalized dark energy from current observations. We show that, though we cannot find any stringent limits on the anisotropic stress or the nonadiabatic pressure fluctuation themselves, the constraints on the equation of state of dark energy can be affected in some cases by the nature of dark energy fluctuation characterized by these properties. This may have important implications in the strategy to study the nature of dark energy.

  15. Dense baryonic matter: Constraints from recent neutron star observations

    NASA Astrophysics Data System (ADS)

    Hell, Thomas; Weise, Wolfram

    2014-10-01

    Updated constraints from neutron star masses and radii impose stronger restrictions on the equation of state for baryonic matter at high densities and low temperatures. The existence of 2M⊙ neutron stars rules out many soft equations of state with prominent "exotic" compositions. The present work reviews the conditions required for the pressure as a function of baryon density to satisfy these constraints. Several scenarios for sufficiently stiff equations of state are evaluated. The common starting point is a realistic description of both nuclear and neutron matter based on a chiral effective field theory approach to the nuclear many-body problem. Possible forms of hybrid matter featuring a quark core in the center of the star are discussed using a three-flavor Polyakov-Nambu-Jona-Lasinio model. It is found that a conventional equation of state based on nuclear chiral dynamics meets the astrophysical constraints. Hybrid matter generally turns out to be too soft unless additional strongly repulsive correlations, e.g., through vector current interactions between quarks, are introduced. The extent to which strangeness can accumulate in the equation of state is also discussed.

  16. Constraints on cosmic distance duality relation from cosmological observations

    NASA Astrophysics Data System (ADS)

    Lv, Meng-Zhen; Xia, Jun-Qing

    2016-09-01

    In this paper, we use the model dependent method to revisit the constraint on the well-known cosmic distance duality relation (CDDR). By using the latest SNIa samples, such as Union2.1, JLA and SNLS, we find that the SNIa data alone cannot constrain the cosmic opacity parameter ε, which denotes the deviation from the CDDR, dL =dA(1 + z) 2 + ε, very well. The constraining power on ε from the luminosity distance indicator provided by SNIa and GRB is hardly to be improved at present. When we include other cosmological observations, such as the measurements of Hubble parameter, the baryon acoustic oscillations and the distance information from cosmic microwave background, we obtain the tightest constraint on the cosmic opacity parameter ε, namely the 68% C.L. limit: ε = 0.023 ± 0.018. Furthermore, we also consider the evolution of ε as a function of z using two methods, the parametrization and the principle component analysis, and do not find the evidence for the deviation from zero. Finally, we simulate the future SNIa and Hubble measurements and find the mock data could give very tight constraint on the cosmic opacity ε and verify the CDDR at high significance.

  17. Large Scale Constraints on Methane Emissions Determined from Observations

    NASA Astrophysics Data System (ADS)

    Dlugokencky, E. J.; Lang, P.; Masarie, K.; Crotwell, A. M.; Bruhwiler, L.

    2011-12-01

    Measurements of atmospheric CH4 from the NOAA Global Monitoring Division's, Global Cooperative Air Sampling Network began in 1983. These high-precision observations offer key constraints on CH4's budget including the global burden, the rate of increase, and the spatial distribution of CH4 at the surface. These observations allow estimates of total global CH4 emissions without using a chemical transport model. A surprising result of this analysis is that, if the CH4 lifetime has been constant, then total global emissions have been approximately constant since the mid-1980s. This result is difficult to reconcile with bottom-up inventories that report increasing anthropogenic emissions, unless natural emissions have decreased considerably. Analysis of anomalies in CH4 growth rate also allow us to test our understanding of the processes that affect the atmospheric CH4 burden. Large anomalies have been attributed to decreased CH4 sink after the eruption of Mt. Pinatubo in 1992, decreased emissions from wetlands because of cooler than normal temperatures in 1992, and increased emissions from biomass burning and wetlands in 1997/98. The most recent anomaly, starting in 2007 and continuing into early-2011 with an average rate of increase of ~6 ppb yr-1, is more persistent than previous ones and may indicate a permanent change to the global CH4 budget. Dlugokencky et al. [Geophys. Res. Lett., 36, 2009] attributed the increases in 2007 and 2008 to anomalously high temperatures in the Arctic (2007) and greater than average precipitation in the tropics (2007 and 2008). Continuing increases in 2009 and 2010 may be related to a very strong La Niña starting in 2010, the same climate pattern responsible for large positive precipitation anomalies in tropical wetland regions in 2007 and 2008. Indeed, strong precipitation anomalies were observed in SE Asia during 2010. This is a likely cause of continued CH4 increase, and it is consistent with the observation that the largest growth

  18. From interstellar dust to comets - A unification of observational constraints

    NASA Technical Reports Server (NTRS)

    Greenberg, J. Mayo; Hage, J. I.

    1990-01-01

    The interstellar dust model of comets is numerically worked out to satisfy simultaneously several basic constraints provided by observations of Comet Halley, and to derive the porosity of coma dust. The observational constraints are (1) the strengths of the 3.4 and 9.7 micron emission bands, (2) the shape of the 9.7 micron band, (3) the amount of silicates relative to organic materials, and (4) the mass distribution of the dust. The method used involves precise calculations of temperatures and the emission characteristics of porous aggregates of interstellar dust as a function of their mass, porosity, and distance to the sun and the wavelength. The results indicate that coma dust has a porosity in the range 0.93-0.975, i.e., a packing factor of 0.07 or less, consistent with independent observations of comet densities of 0.6 to 0.26 g/cu cm and meteor densities of less than 0.2 g/cu cm.

  19. From interstellar dust to comets - A unification of observational constraints

    SciTech Connect

    Greenberg, J.M.; Hage, J.I. )

    1990-09-01

    The interstellar dust model of comets is numerically worked out to satisfy simultaneously several basic constraints provided by observations of Comet Halley, and to derive the porosity of coma dust. The observational constraints are (1) the strengths of the 3.4 and 9.7 micron emission bands, (2) the shape of the 9.7 micron band, (3) the amount of silicates relative to organic materials, and (4) the mass distribution of the dust. The method used involves precise calculations of temperatures and the emission characteristics of porous aggregates of interstellar dust as a function of their mass, porosity, and distance to the sun and the wavelength. The results indicate that coma dust has a porosity in the range 0.93-0.975, i.e., a packing factor of 0.07 or less, consistent with independent observations of comet densities of 0.6 to 0.26 g/cu cm and meteor densities of less than 0.2 g/cu cm. 63 refs.

  20. Observational Constraints on n>2 Multiples in the Kuiper Belt

    NASA Astrophysics Data System (ADS)

    Noll, K. S.

    2006-12-01

    The discovery of two small satellites of the Pluto-Charon binary (Weaver et al. 2006, Nature 439, 943) clearly demonstrates that complex multiples can and do exist among the population of transneptunian objects. The discovery of a second companion to the main belt asteroid (87) Sylvia establishes the same existence proof for the inner solar system (Marchis et al. 2005, Nature 436, 822). The mode of formation for binaries and multiples remains to be unambiguously identified for any small body population in the solar system. Collisional models of binary formation show that some fraction of triples and higher order multiples can be expected to form as a natural consequence of chance capture of impact debris (Leinhardt and Richardson 2005, Icarus 176, 432). However, these models cannot be used to accurately predict the fraction of such systems in the absence of observational constraints. Likewise, capture models can, in principle, produce multiples, but quantitative work on this question has not been done. The large survey that we are carrying out with the Hubble Space Telescope is providing the most stringent observational constraints on the frequencies of binaries and higher order multiples to date. Of the roughly 20 binaries observed with the ACS/HRC, none has been found to have a third companion. The limits vary with the observations, but, generally speaking, most of the observations search several magnitudes fainter than the primary at separations of 50 milliarcsec or more. Future observations with HST have the capability to increase this limit by an order of magnitude by increasing the sample of known binaries.

  1. Observational constraints on cosmic neutrinos and dark energy revisited

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Meng, Xiao-Lei; Zhang, Tong-Jie; Shan, HuanYuan; Gong, Yan; Tao, Charling; Chen, Xuelei; Huang, Y. F.

    2012-11-01

    Using several cosmological observations, i.e. the cosmic microwave background anisotropies (WMAP), the weak gravitational lensing (CFHTLS), the measurements of baryon acoustic oscillations (SDSS+WiggleZ), the most recent observational Hubble parameter data, the Union2.1 compilation of type Ia supernovae, and the HST prior, we impose constraints on the sum of neutrino masses (mν), the effective number of neutrino species (Neff) and dark energy equation of state (w), individually and collectively. We find that a tight upper limit on mν can be extracted from the full data combination, if Neff and w are fixed. However this upper bound is severely weakened if Neff and w are allowed to vary. This result naturally raises questions on the robustness of previous strict upper bounds on mν, ever reported in the literature. The best-fit values from our most generalized constraint read mν = 0.556+0.231-0.288 eV, Neff = 3.839±0.452, and w = -1.058±0.088 at 68% confidence level, which shows a firm lower limit on total neutrino mass, favors an extra light degree of freedom, and supports the cosmological constant model. The current weak lensing data are already helpful in constraining cosmological model parameters for fixed w. The dataset of Hubble parameter gains numerous advantages over supernovae when w = -1, particularly its illuminating power in constraining Neff. As long as w is included as a free parameter, it is still the standardizable candles of type Ia supernovae that play the most dominant role in the parameter constraints.

  2. Observational constraints on cosmic neutrinos and dark energy revisited

    SciTech Connect

    Wang, Xin; Meng, Xiao-Lei; Zhang, Tong-Jie; Shan, HuanYuan; Tao, Charling; Gong, Yan; Chen, Xuelei; Huang, Y.F. E-mail: mlwx@mail.bnu.edu.cn E-mail: shanhuany@gmail.com E-mail: tao@cppm.in2p3.fr E-mail: hyf@nju.edu.cn

    2012-11-01

    Using several cosmological observations, i.e. the cosmic microwave background anisotropies (WMAP), the weak gravitational lensing (CFHTLS), the measurements of baryon acoustic oscillations (SDSS+WiggleZ), the most recent observational Hubble parameter data, the Union2.1 compilation of type Ia supernovae, and the HST prior, we impose constraints on the sum of neutrino masses (m{sub ν}), the effective number of neutrino species (N{sub eff}) and dark energy equation of state (w), individually and collectively. We find that a tight upper limit on m{sub ν} can be extracted from the full data combination, if N{sub eff} and w are fixed. However this upper bound is severely weakened if N{sub eff} and w are allowed to vary. This result naturally raises questions on the robustness of previous strict upper bounds on m{sub ν}, ever reported in the literature. The best-fit values from our most generalized constraint read m{sub ν} = 0.556{sup +0.231}{sub −0.288} eV, N{sub eff} = 3.839±0.452, and w = −1.058±0.088 at 68% confidence level, which shows a firm lower limit on total neutrino mass, favors an extra light degree of freedom, and supports the cosmological constant model. The current weak lensing data are already helpful in constraining cosmological model parameters for fixed w. The dataset of Hubble parameter gains numerous advantages over supernovae when w = −1, particularly its illuminating power in constraining N{sub eff}. As long as w is included as a free parameter, it is still the standardizable candles of type Ia supernovae that play the most dominant role in the parameter constraints.

  3. Observational Constraints on the White Dwarf Mass--Radius Relation

    NASA Astrophysics Data System (ADS)

    Oswalt, Terry D.; Dhital, Saurav; Mizusawa, Trisha; Holberg, Jay B.; Zhao, Jingkun

    2014-02-01

    We propose to measure gravitational redshifts for white dwarf stars that have distant, non-interacting main-sequence companions. With independent radius constraints obtained from parallaxes and surface gravity determinations obtained by fitting the Balmer series from our spectra, we will make improved estimates of white dwarf masses and radii that can be critically compared with theoretical mass-radius relations specific to each star. These observations will allow us to examine serious discrepancies between the theoretical and empirical measurements of the white dwarf mass-radius relation and extend the range of masses over which it has been tested, spanning 0.5-1.2 Msun. Currently, the measured radius for only a single WD matches its predicted value. Using the same spectra, we will also estimate the metallicity of the main-sequence companion and examine how the initial-final-mass ratio for WDs depends on metallicity. Thus, this project will put robust constraints on two fundamental relations that govern our understanding of white dwarfs: the mass-ratio and the initial-final-mass relations.

  4. Observational Constraints on the White Dwarf Mass-Radius Relation

    NASA Astrophysics Data System (ADS)

    Dhital, Saurav; Oswalt, Terry D.; Holberg, J. B.; Zhao, Jingkun

    2014-08-01

    We propose to measure gravitational redshifts for white dwarf stars that have distant, non-interacting main-sequence companions. With independent radius constraints obtained from parallaxes and surface gravity determinations obtained by fitting the Balmer series from our spectra, we will make improved estimates of white dwarf masses and radii that can be critically compared with theoretical mass-radius relations specific to each star. These observations will allow us to examine serious discrepancies between the theoretical and empirical measurements of the white dwarf mass-radius relation and extend the range of masses over which it has been tested, spanning 0.5-1.2 Msun. Currently, the measured radius for only a single WD matches its predicted value within 5%. With the expected precision of ≲5% for over half the sample, we will also distinguish whether the white dwarfs have ``thick'' or ``thin'' H envelopes. Using the same spectra, we will also estimate the metallicity of the main-sequence companion and examine how the initial-final-mass ratio for WDs depends on metallicity. Thus, this project will put robust constraints on two fundamental relations that govern our understanding of white dwarfs: the mass-ratio and the initial-final-mass relations.

  5. Constraints on neutrino masses from future cosmological observations

    SciTech Connect

    Hirano, Koichi

    2014-05-02

    Constraints on neutrino masses are estimated based on future observations of the cosmic microwave background (CMB) including the B-mode polarization produced by CMB lensing using the Planck satellite, and baryon acoustic oscillations distance scale and the galaxy power spectrum from all-sky galaxy redshift survey in the BigBOSS experiment. We estimate the error in the bound on the total neutrino mass to be Δ∑m{sub v} = 0.012 eV with a 68% confidence level. If the fiducial value of the total neutrino mass is ∑m{sub v} = 0.06 eV, this result implies that the neutrino mass hierarchy must be normal.

  6. Observational constraints on modified Chaplygin gas from cosmic growth

    SciTech Connect

    Paul, B.C.; Thakur, P. E-mail: prasenjit_thakur1@yahoo.co.in

    2013-11-01

    We investigate the linear growth function for the large scale structures of the universe considering modified Chaplygin gas as dark energy. Taking into account observational growth data for a given range of redshift from the Wiggle-Z measurements and rms mass fluctuations from Ly-α measurements we numerically analyze cosmological models to constrain the parameters of the MCG. The observational data of Hubble parameter with redshift z is also considered. The Wang-Steinhardt ansatz for growth index γ and growth function f (defined as f = Ω{sub m}{sup γ}(a)) are considered for the numerical analysis. The best-fit values of the equation of state parameters obtained here is employed to study the growth function (f), growth index (γ) and equation of state (ω) with redshift z. The observational constraints on MCG parameters obtained here are compared with that of the GCG model for viable cosmology. It is noted that MCG also satisfactorily accommodates an accelerating phase followed by a matter dominated phase of the universe.

  7. Constraints on PSC Particle Microphysics Derived From Lidar Observations

    NASA Technical Reports Server (NTRS)

    Liu, Li; Mishchenko, Michael I.

    2001-01-01

    Based on extensive T-matrix computations of light scattering by polydispersions of randomly oriented, rotationally symmetric nonspherical particles, we analyze existing lidar observations of polar stratospheric clouds (PSCs) and derive several constraints on PSC particle microphysical properties. We show that sharp-edged nonspherical particles (finite circular cylinders) exhibit less variability of lidar backscattering characteristics with particle size and aspect ratio than particles with smooth surfaces (spheroids). For PSC particles significantly smaller than the wavelength, the backscatter color index Alpha and the depolarization color index Beta are essentially shape-independent. Observations for type Ia PSCs can be reproduced by spheroids with aspect ratios larger than 1.2, oblate cylinders with diameter-to-length ratios greater than 1.6, and prolate cylinders with length-to-diameter ratios greater than 1.4. The effective equal-volume-sphere radius for type la PSCs is about 0.8 microns or larger. Type Ib PSCs are likely to be composed of spheres or nearly spherical particles with effective radii smaller than 0.8 microns. Observations for type II PSCs are consistent with large ice crystals (effective radius greater than 1 micron modeled as cylinders or prolate spheroids.

  8. Observational constraints on holographic dark energy with varying gravitational constant

    SciTech Connect

    Lu, Jianbo; Xu, Lixin; Saridakis, Emmanuel N.; Setare, M.R. E-mail: msaridak@phys.uoa.gr E-mail: lxxu@dlut.edu.cn

    2010-03-01

    We use observational data from Type Ia Supernovae (SN), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and observational Hubble data (OHD), and the Markov Chain Monte Carlo (MCMC) method, to constrain the cosmological scenario of holographic dark energy with varying gravitational constant. We consider both flat and non-flat background geometry, and we present the corresponding constraints and contour-plots of the model parameters. We conclude that the scenario is compatible with observations. In 1σ we find Ω{sub Λ0} = 0.72{sup +0.03}{sub −0.03}, Ω{sub k0} = −0.0013{sup +0.0130}{sub −0.0040}, c = 0.80{sup +0.19}{sub −0.14} and Δ{sub G}≡G'/G = −0.0025{sup +0.0080}{sub −0.0050}, while for the present value of the dark energy equation-of-state parameter we obtain w{sub 0} = −1.04{sup +0.15}{sub −0.20}.

  9. Type Ia Supernovae: Explosion Models versus Observational Constraints

    NASA Astrophysics Data System (ADS)

    Branch, David

    2005-04-01

    To have confidence in using Type Ia supernovae (SNe Ia) to determine the expansion history of the universe, and thereby probe the nature of the dark energy, we must advance our understanding of SN Ia physics. In the standard model a carbon--oxygen white dwarf accretes matter from a companion star, approaches the Chandrasekhar mass, ignites carbon fusion, encounters a thermonuclear instability, and explodes completely. The final kinetic energy of the ejected matter is the energy released by fusion minus the white--dwarf binding energy. The kinetic energy inferred from observations indicates that practically the whole white dwarf undergoes fusion. The peak luminosity depends on the mass of freshly synthesized ^56Ni, which provides a delayed release of energy while decaying through ^56Co to stable ^56Fe. The observed SN Ia luminosity requires that nearly half of the mass is synthesized to ^56Ni. Spectroscopic observations indicate that the composition structure of the ejected matter is radially stratified, with a core of iron--group elements surrounded by lighter elements such as calcium, silicon, and oxygen. Spherically symmetric (1D) nuclear-hydrodynamical explosion models that meet these requirements have been calculated, by parameterizing the velocity of the burning front. In recent years more self--consistent 3D models have been calculated. Deflagration models, in which the burning front remains subsonic, undergo insufficient fusion and lack the stratified composition structure. Delayed--detonation models, which invoke a transition to supersonic front propagation, fare better, although it is not known whether the transition really can occur. I will discuss the status of explosion models versus observational constraints (mostly spectroscopic), and the challenging task of relating the various observational manifestations of SN Ia diversity to their physical causes.

  10. Observational and modeling constraints on global anthropogenic enrichment of mercury.

    PubMed

    Amos, Helen M; Sonke, Jeroen E; Obrist, Daniel; Robins, Nicholas; Hagan, Nicole; Horowitz, Hannah M; Mason, Robert P; Witt, Melanie; Hedgecock, Ian M; Corbitt, Elizabeth S; Sunderland, Elsie M

    2015-04-01

    Centuries of anthropogenic releases have resulted in a global legacy of mercury (Hg) contamination. Here we use a global model to quantify the impact of uncertainty in Hg atmospheric emissions and cycling on anthropogenic enrichment and discuss implications for future Hg levels. The plausibility of sensitivity simulations is evaluated against multiple independent lines of observation, including natural archives and direct measurements of present-day environmental Hg concentrations. It has been previously reported that pre-industrial enrichment recorded in sediment and peat disagree by more than a factor of 10. We find this difference is largely erroneous and caused by comparing peat and sediment against different reference time periods. After correcting this inconsistency, median enrichment in Hg accumulation since pre-industrial 1760 to 1880 is a factor of 4.3 for peat and 3.0 for sediment. Pre-industrial accumulation in peat and sediment is a factor of ∼ 5 greater than the precolonial era (3000 BC to 1550 AD). Model scenarios that omit atmospheric emissions of Hg from early mining are inconsistent with observational constraints on the present-day atmospheric, oceanic, and soil Hg reservoirs, as well as the magnitude of enrichment in archives. Future reductions in anthropogenic emissions will initiate a decline in atmospheric concentrations within 1 year, but stabilization of subsurface and deep ocean Hg levels requires aggressive controls. These findings are robust to the ranges of uncertainty in past emissions and Hg cycling. PMID:25750991

  11. Carbon chemistry in dense molecular clouds: Theory and observational constraints

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    1990-01-01

    For the most part, gas phase models of the chemistry of dense molecular clouds predict the abundances of simple species rather well. However, for larger molecules and even for small systems rich in carbon these models often fail spectacularly. Researchers present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention is to the influence of the gas phase C/O ratio in molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from initially diffuse objects to denser cores with associated stellar and planetary formation. Recent spectral line surveys at centimeter and millimeter wavelengths along with selected observations in the submillimeter have now produced an accurate inventory of the gas phase carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly remain. The constraints these observations place on theoretical models of interstellar chemistry can be used to gain insights into why the models fail, and show also which neglected processes must be included in more complete analyses. Looking toward the future, larger molecules are especially difficult to study both experimentally and theoretically in such dense, cold regions, and some new methods are therefore outlined which may ultimately push the detectability of small carbon chains and rings to much heavier species.

  12. Observational constraints on a variable dark energy model

    SciTech Connect

    Movahed, M. Sadegh; Rahvar, Sohrab

    2006-04-15

    We study the effect of a phenomenological parameterized quintessence model on low, intermediate and high redshift observations. At low and intermediate redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently observed size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), to put constraint on the parameters of the quintessence model. At the high redshift, the same fitting procedure is done using WAMP data, comparing the location of acoustic peak with that obtain from the dark energy model. As a complementary analysis in a flat universe, we combine the results from the SNIa, CMB and SDSS. The best fit values for the model parameters are {omega}{sub m}=0.27{sub -0.02}{sup +0.02} (the present matter content) and w{sub 0}=-1.45{sub -0.60}{sup +0.35} (dark energy equation of state). Finally we calculate the age of universe in this model and compare it with the age of old stars and high redshift objects.

  13. Observational Constraints on a Pluto Torus of Circumsolar Neutral Gas

    NASA Astrophysics Data System (ADS)

    Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Smith, H. T.; Bagenal, F.; Brown, L. E.; Elliott, H. A.; Haggerty, D. K.; Horanyi, M.; Krimigis, S. M.; Kusterer, M. B.; Lisse, C. M.; McComas, D. J.; Piquette, M. R.; Sidrow, E. J.; Strobel, D. F.; Szalay, J.; Vandegriff, J. D.; Zirnstein, E.; Ennico Smith, K.; Olkin, C.; Weaver, H. A., Jr.; Young, L. A.; Stern, S. A.

    2015-12-01

    We present the concept of a neutral gas torus surrounding the Sun, aligned with Pluto's orbit, and place observational constraints based primarily on comparison of New Horizons (NH) measurements with a 3-D Monte Carlo model adapted from analogous satellite tori surrounding Saturn and Jupiter. Such a torus, or perhaps partial torus, should result from neutral N2 escaping from Pluto's exosphere. Unlike other more massive planets closer to the Sun, neutrals escape Pluto readily owing, e.g., to the high thermal speed relative to the escape velocity. Importantly, escaped neutrals have a long lifetime due to the great distance from the Sun, ~100 years for photoionization of N2 and ~180 years for photoionization of N, which results from disassociated N2. Despite the lengthy 248-year orbit, these long e-folding lifetimes may allow an enhanced neutral population to form an extended gas cloud that modifies the N2 spatial profile near Pluto. These neutrals are not directly observable by NH but once ionized N2+ or N+ are picked up by the solar wind, reaching ~50 keV, making these pickup ions (PUIs) detectable by NH's Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. PEPSSI observations analyzed to date may constrain the N2 density; the remaining ~95% of the encounter data, scheduled for downlink in August along with similarly anticipated data from the Solar Wind Around Pluto (SWAP) experiment, should help determine the Pluto outgassing rates. Measurements from SWAP include the solar wind speed, a quantity that greatly enhances PUI studies by enabling us to directly account for the PUI distribution's sensitive dependence on plasma speed. Note that anomalous cosmic ray Si observed at Voyager is overabundant by a factor of ~3000 relative to interstellar composition. This might be related to "outer source" PUIs, but the fact that N2 and Si are indistinguishable in many instruments could mean that N2 is actually driving this apparent Si discrepancy.

  14. Observational constraints on interannual variability projections in CMIP5

    NASA Astrophysics Data System (ADS)

    Borodina, Aleksandra; Fischer, Erich M.; Knutti, Reto

    2014-05-01

    Impacts of climate change are sensitive not only to changes in the mean state but also to potential changes in the internal variability of the climate system at diurnal to interannual and multi-decadal time scales. Internal variability arises from nonlinear interactions and complex feedbacks between ocean, sea ice, atmosphere and land surface without any external forcing. However, an external forcing may change both magnitude, spatial patterns and the time scales of these variations. It is crucial to understand whether and on what temporal and spatial scales internal variability will undergo changes under anthropogenic radiative forcing and to identify the underlying mechanisms. To address these questions, we here use model simulations of the Coupled Model Intercomparison Project Phase 5 database (CMIP5) with historical (1850-2005) - RCP8.5 (2006-2100) concentration pathway. First, we show over which latitudes CMIP5 models simulate robust changes in variability. Second, we explore whether models with low present-day internal variability project changes that substantially differ from those models with high present-day internal variability. Such an inter-model relationship is found over the high-latitudes of both hemispheres. For the regions and seasons, for which a relationship across the multi-model ensemble exists, we use observations and reanalyses, to constrain the model projections. This model constraint is based on the assumption that models with a more realistic representation of present-day variability yield more reliable projections. Once a relationship is identified, physical understanding becomes crucial because it must have a strong physical grounding to justify the constraint. We explore mechanisms that explain the inter-model correlation between current variability and its future change especially at high latitudes. We use a "joint projection" approach, which is based on the fact that multiple climate variables are correlated over different scales in

  15. Observational constraints on neutron star Masses and Radii

    NASA Astrophysics Data System (ADS)

    Heinke, Craig

    2016-07-01

    There are major uncertainties in the composition and structure of neutron star (NS) interiors, making measurements of the compactness and thermal properties of NSs quite valuable. Dozens of NSs have precisely measured masses (generally through radio timing of pulsars). However, current methods for precise measurement of radius, and thus compactness, generally suffer from conflicting interpretations of observable quantities. I will summarize the questions at issue, and the current state of the data. For instance, for quiescent low-mass X-ray binaries in globular clusters, these include issues of atmospheric composition, distance determination methods, and the possible presence of hot spots on the surface. The thermal properties of NSs, mostly set by neutrino emission from the core, divulge information about the core composition, and its superfluid properties. Young NSs appear to be well-described by "minimal cooling" (see Page's talk), while some old NSs in low-mass X-ray binaries show evidence for strongly enhanced neutrino core cooling. The young NS in Cassiopeia A has been reported to show rapid cooling, that has been interpreted as indicating that the neutrons in the core are transitioning to a superfluid state. The initial cooling measurement was too rapid; it is currently unclear whether the Cas A NS is cooling rapidly or not. I will conclude with some discussion of paths forward toward constraints in these directions, besides the NICER instrument.

  16. OBSERVATIONAL CONSTRAINTS ON THE DEGENERATE MASS-RADIUS RELATION

    SciTech Connect

    Holberg, J. B.; Oswalt, T. D.; Barstow, M. A. E-mail: toswalt@fit.edu

    2012-03-15

    The white dwarf mass-radius relationship is fundamental to modern astrophysics. It is central to routine estimation of DA white dwarf masses derived from spectroscopic temperatures and gravities. It is also the basis for observational determinations of the white dwarf initial-final-mass relation. Nevertheless, definitive and detailed observational confirmations of the mass-radius relation (MRR) remain elusive owing to a lack of sufficiently accurate white dwarf masses and radii. Current best estimates of masses and radii allow only broad conclusions about the expected inverse relation between masses and radii in degenerate stars. In this paper, we examine a restricted set of 12 DA white dwarf binary systems for which accurate (1) trigonometric parallaxes, (2) spectroscopic effective temperatures and gravities, and (3) gravitational redshifts are available. We consider these three independent constraints on mass and radius in comparison with an appropriate evolved MRR for each star. For the best-determined systems it is found that the DA white dwarfs conform to evolve theoretical MRRs at the 1{sigma} to 2{sigma} level. For the white dwarf 40 Eri B (WD 0413-077) we find strong evidence for the existence of a 'thin' hydrogen envelope. For other stars improved parallaxes will be necessary before meaningful comparisons are possible. For several systems current parallaxes approach the precision required for the state-of-the-art mass and radius determinations that will be obtained routinely from the Gaia mission. It is demonstrated here how these anticipated results can be used to firmly constrain details of theoretical mass-radius determinations.

  17. OBSERVATIONAL CONSTRAINTS ON RED AND BLUE HELIUM BURNING SEQUENCES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F.; Dolphin, Andrew E.; Holtzman, Jon

    2011-10-10

    We derive the optical luminosity, colors, and ratios of the blue and red helium burning (HeB) stellar populations from archival Hubble Space Telescope observations of nineteen starburst dwarf galaxies and compare them with theoretical isochrones from Padova stellar evolution models across metallicities from Z = 0.001 to 0.009. We find that the observational data and the theoretical isochrones for both blue and red HeB populations overlap in optical luminosities and colors and the observed and predicted blue to red HeB ratios agree for stars older than 50 Myr over the time bins studied. These findings confirm the usefulness of applying isochrones to interpret observations of HeB populations. However, there are significant differences, especially for the red HeB population. Specifically, we find (1) offsets in color between the observations and theoretical isochrones of order 0.15 mag (0.5 mag) for the blue (red) HeB populations brighter than M{sub V} {approx} -4 mag, which cannot be solely due to differential extinction; (2) blue HeB stars fainter than M{sub V} {approx} -3 mag are bluer than predicted; (3) the slope of the red HeB sequence is shallower than predicted by a factor of {approx}3; and (4) the models overpredict the ratio of the most luminous blue to red HeB stars corresponding to ages {approx}< 50 Myr. Additionally, we find that for the more metal-rich galaxies in our sample (Z {approx}> 0.5 Z{sub sun}), the red HeB stars overlap with the red giant branch stars in the color-magnitude diagrams, thus reducing their usefulness as indicators of star formation for ages {approx}> 100 Myr.

  18. Observational constraints on biogenic VOC emission model estimates (Invited)

    NASA Astrophysics Data System (ADS)

    Guenther, A. B.

    2013-12-01

    Chemistry and transport models require accurate estimates of biogenic volatile organic compound (BVOC) emissions in order to simulate the atmospheric constituents controlling air quality and climate, such as ozone and particles, and so the uncertainties associated with BVOC estimates may be limiting the development of effective air quality and climate management strategies. BVOC emission models include driving variables and algorithms that span scales from the leaf level to entire landscapes. While considerable effort has been made to improve BVOC emission models in the past decades, there have been relatively few attempts to quantify the uncertainties associated with these estimates or to rigorously assess emission modeling approaches. This presentation will summarize the availability of observations that can be used to constrain BVOC emission models including flux measurements (leaf enclosure, above canopy tower, and aircraft platforms) and ambient concentrations of BVOC and their products. Results from studies targeting specific BVOC emission processes (e.g., the response of isoprene emission to drought and the response of monoterpene emissions to bark beetle attack) will be shown and the application of these observations for BVOC model evaluation will be discussed. In addition, the results from multi-scale BVOC emission studies (leaf enclosure, whole canopy flux tower, regional aircraft eddy covariance) will be presented and a approach for incorporating these observations into a community model testbed will be described and used to evaluate regional BVOC emission models.

  19. Constraints on lower crust rheology from multi-parameter observations.

    NASA Astrophysics Data System (ADS)

    Sacks, S.; Linde, A.

    2003-04-01

    It is usually assumed that the lower crust is lower viscosity than the underlying mantle and further, that the lower crust does not store long-term strain energy. This is reasonable because the temperature of the mafic lower crust is closer to its melting point than is the underlying peridotitic mantle. However, recent observations and analyses suggest that this rheological assumption may not be right. Fault slip preceding a number of great shallow earthquakes seems to have started below what is normally considered to be the locked zone in the brittle upper crust and propagated slowly to the region which then fails at high rupture velocity. In addition, inversion of GPS determined crustal deformation data suggests that the lower crust has higher viscosity than the uppermost mantle. There also is a difference if crustal parameters are examined over century or million year time periods. Before the 1944 Tonankai and the 1946 Nankaido earthquakes, both greater than m=8, there were observations which could be interpreted as due to strain release on the downward extension of the fault. Unexpectedly large closure errors in a repeated leveling survey in the Kakegawa region starting a few days before the 1944 event and continuing for a few days after it, if interpreted as ground tilt signals, suggest slow slip on the Philippine Sea subduction thrust fault. Recent analysis by Linde and Sacks (2002) shows that all the leveling data is consistent with slip down dip of the seismic fault which starts 2 days before the earthquake and continues after it. In addition, water well changes before the 1946 Nankaido earthquake are also consistent similar slip down dip of the "seismic" fault. Other examples of down dip strain release before the great Chile earthquake of 1960 and the Japan Sea earthquake of 1983 have been described, (Linde and Silver, 1989. and Linde et al, 1987). The strain build up times for the above-mentioned earthquakes are of order one to a few centuries. Of course

  20. Observational constraints of Polar Ice Deposits on Mars Atmospheric GCMs

    NASA Astrophysics Data System (ADS)

    Teodoro, L. F. A.; Elphic, R. C.; Hollingsworth, J. L.; Haberle, R. M.; Kahre, M. A.; Eke, V. R.; Roush, T. L.; Marzo, G. A.; Brown, A. J.; Feldman, W. C.; Maurice, S.

    2012-04-01

    Much of our current knowledge about Mars' climate and atmospheric global circulation stems from measurements taken by landers and orbiters. Thus for many years the details of the atmospheric circulation were studied using numerical global circulation models (GCMs) that have been successful in reproducing most of the available observations [1]. More than ever, GCMs will play a central role in analyzing the existing data and in planning and execution of upcoming missions. The Mars Odyssey Neutron Spectrometer (MONS) has enabled a comprehensive study of the overall distribution of hydrogen in the surface of Mars [2]. Deposits ranging between 20% and 100% Water-Equivalent Hydrogen (WEH) by mass are found pole-ward of 55 deg. latitude, while less H-rich deposits are found at lower latitudes. These results assume that the H distribution is uniform in the top meter of the martian soil. The Mars Reconnaissance Orbiter-Compact Reconnaissance Imaging Spectrometer for Mars (MRO-CRISM) has identified numerous locations on Mars where hydrous minerals occur [3]. The information collected by MRO-CRISM samples the top few mm's to cm's of the surface. This independent information can impose additional constrains on the 3-D H distribution inferred from the MONS data. For instance, the absence of a correlation between WEH wt% drawn from the MONS and CRISM data at a location where the neutron data indicate high WEH implies the presence of a 3-D structure that is characterized by a top layer with a low abundance of water, either ice or hydrated minerals, and some buried layers where the concentration of H is higher than that expected in a uniformly mixed layer. However, the spatial resolution of MONS and MRO-CRISM are ~550 km and ~20-200m, respectively. Hence, one must assure the MRO-CRISM and MONS data are on the same scales. The MRO-CRISM data can be re-binned to lower resolution, but additionally the MONS instrumental smearing must be properly understood and removed. Usually, in the

  1. Observational constraints on dark energy with a fast varying equation of state

    SciTech Connect

    Felice, Antonio De; Nesseris, Savvas

    2012-05-01

    We place observational constraints on models with the late-time cosmic acceleration based on a number of parametrizations allowing fast transitions for the equation of state of dark energy. In addition to the model of Linder and Huterer where the dark energy equation of state w monotonically grows or decreases in time, we propose two new parametrizations in which w has an extremum. We carry out the likelihood analysis with the three parametrizations by using the observational data of supernovae type Ia, cosmic microwave background, and baryon acoustic oscillations. Although the transient cosmic acceleration models with fast transitions can give rise to the total chi square smaller than that in the Λ-Cold-Dark-Matter (ΛCDM) model, these models are not favored over ΛCDM when one uses the Akaike information criterion which penalizes the extra degrees of freedom present in the parametrizations.

  2. Constraints on dark matter annihilation from CMB observations before Planck

    SciTech Connect

    Lopez-Honorez, Laura; Mena, Olga; Palomares-Ruiz, Sergio; Vincent, Aaron C. E-mail: omena@ific.uv.es E-mail: vincent@ific.uv.es

    2013-07-01

    We compute the bounds on the dark matter (DM) annihilation cross section using the most recent Cosmic Microwave Background measurements from WMAP9, SPT'11 and ACT'10. We consider DM with mass in the MeV–TeV range annihilating 100% into either an e{sup +}e{sup −} or a μ{sup +}μ{sup −} pair. We consider a realistic energy deposition model, which includes the dependence on the redshift, DM mass and annihilation channel. We exclude the canonical thermal relic abundance cross section ((σv) = 3 × 10{sup −26}cm{sup 3}s{sup −1}) for DM masses below 30 GeV and 15 GeV for the e{sup +}e{sup −} and μ{sup +}μ{sup −} channels, respectively. A priori, DM annihilating in halos could also modify the reionization history of the Universe at late times. We implement a realistic halo model taken from results of state-of-the-art N-body simulations and consider a mixed reionization mechanism, consisting on reionization from DM as well as from first stars. We find that the constraints on DM annihilation remain unchanged, even when large uncertainties on the halo model parameters are considered.

  3. Integrated reservoir characterization: Improvement in heterogeneities stochastic modelling by integration of additional external constraints

    SciTech Connect

    Doligez, B.; Eschard, R.; Geffroy, F.

    1997-08-01

    The classical approach to construct reservoir models is to start with a fine scale geological model which is informed with petrophysical properties. Then scaling-up techniques allow to obtain a reservoir model which is compatible with the fluid flow simulators. Geostatistical modelling techniques are widely used to build the geological models before scaling-up. These methods provide equiprobable images of the area under investigation, which honor the well data, and which variability is the same than the variability computed from the data. At an appraisal phase, when few data are available, or when the wells are insufficient to describe all the heterogeneities and the behavior of the field, additional constraints are needed to obtain a more realistic geological model. For example, seismic data or stratigraphic models can provide average reservoir information with an excellent areal coverage, but with a poor vertical resolution. New advances in modelisation techniques allow now to integrate this type of additional external information in order to constrain the simulations. In particular, 2D or 3D seismic derived information grids, or sand-shale ratios maps coming from stratigraphic models can be used as external drifts to compute the geological image of the reservoir at the fine scale. Examples are presented to illustrate the use of these new tools, their impact on the final reservoir model, and their sensitivity to some key parameters.

  4. Can an energy balance model provide additional constraints on how to close the energy imbalance?

    PubMed

    Wohlfahrt, Georg; Widmoser, Peter

    2013-02-15

    Elucidating the causes for the energy imbalance, i.e. the phenomenon that eddy covariance latent and sensible heat fluxes fall short of available energy, is an outstanding problem in micrometeorology. This paper tests the hypothesis that the full energy balance, through incorporation of additional independent measurements which determine the driving forces of and resistances to energy transfer, provides further insights into the causes of the energy imbalance and additional constraints on energy balance closure options. Eddy covariance and auxiliary data from three different biomes were used to test five contrasting closure scenarios. The main result of our study is that except for nighttime, when fluxes were low and noisy, the full energy balance generally did not contain enough information to allow further insights into the causes of the imbalance and to constrain energy balance closure options. Up to four out of the five tested closure scenarios performed similarly and in up to 53% of all cases all of the tested closure scenarios resulted in plausible energy balance values. Our approach may though provide a sensible consistency check for eddy covariance energy flux measurements. PMID:24465072

  5. Observational constraint on Pluto's atmospheric CO with ASTE

    NASA Astrophysics Data System (ADS)

    Iino, Takahiro; Hirahara, Yasuhiro; Hidemori, Takehiro; Tsukagoshi, Takashi; Nakajima, Taku; Nakamoto, Satoru; Kato, Chihaya

    2016-02-01

    To confirm the previous observational results of Pluto's atmospheric CO in the J = 2-1 rotational transition, we conducted a new observation of CO (J = 3-2) in Pluto's atmosphere in 2014 August with the Atacama Submillimeter Telescope Experiment 10 m single-dish telescope. In contrast to the previous observational result obtained with the James Clerk Maxwell Telescope in 2009 and 2010 by using the J = 2-1 transition, no emission structure was observed near the rest frequency in our attempt. Possible explanations for the nondetection result of the J = 3-2 transition are discussed.

  6. Constraints provided by ground gravity observations on geocentre motions

    NASA Astrophysics Data System (ADS)

    Rogister, Y.; Mémin, A.; Rosat, S.; Hinderer, J.; Calvo, M.

    2016-06-01

    The geocentre motion is the motion of the centre of mass of the entire Earth, considered an isolated system, in a terrestrial system of reference. We first derive a formula relating the harmonic degree-1 Lagrangian variation of the gravity at a station to both the harmonic degree-1 vertical displacement of the station and the displacement of the whole Earth's centre of mass. The relationship is independent of the nature of the Earth deformation and is valid for any source of deformation. We impose no constraint on the system of reference, except that its origin must initially coincide with the centre of mass of the spherically-symmetric Earth model. Next, we consider the geocentre motion caused by surface loading. In a system of reference whose origin is the centre of mass of the solid Earth, we obtain a specific relationship between the gravity variation at the surface, the geocentre displacement and the load Love number h^' }_1, which demands the Earth's structure and rheological behaviour be known. For various networks of real or fictitious stations, we invert synthetic signals of surface gravity variations caused by atmospheric loading to retrieve the degree-1 variation of gravity. We then select 6 well distributed stations of the Global Geodynamics Project, which is a world network of superconducting gravimeters, to invert actual gravity data for the degree-1 variations and determine the geocentre displacement between the end of 2004 and the beginning of 2012, assuming it to be due to surface loading. We find annual and semi-annual displacements with amplitude 0.5 to 2.3 mm.

  7. Constraints provided by ground gravity observations on geocentre motions

    NASA Astrophysics Data System (ADS)

    Rogister, Y.; Mémin, A.; Rosat, S.; Hinderer, J.; Calvo, M.

    2016-08-01

    The geocentre motion is the motion of the centre of mass of the entire Earth, considered an isolated system, in a terrestrial system of reference. We first derive a formula relating the harmonic degree-1 Lagrangian variation of the gravity at a station to both the harmonic degree-1 vertical displacement of the station and the displacement of the whole Earth's centre of mass. The relationship is independent of the nature of the Earth deformation and is valid for any source of deformation. We impose no constraint on the system of reference, except that its origin must initially coincide with the centre of mass of the spherically symmetric Earth model. Next, we consider the geocentre motion caused by surface loading. In a system of reference whose origin is the centre of mass of the solid Earth, we obtain a specific relationship between the gravity variation at the surface, the geocentre displacement and the load Love number h^' }_1, which demands the Earth's structure and rheological behaviour be known. For various networks of real or fictitious stations, we invert synthetic signals of surface gravity variations caused by atmospheric loading to retrieve the degree-1 variation of gravity. We then select six well-distributed stations of the Global Geodynamics Project, which is a world network of superconducting gravimeters, to invert actual gravity data for the degree-1 variations and determine the geocentre displacement between the end of 2004 and the beginning of 2012, assuming it to be due to surface loading. We find annual and semi-annual displacements with amplitude 0.5-2.3 mm.

  8. Growth mechanism and additional constraints on FeNi metal condensation in the solar nebula

    NASA Astrophysics Data System (ADS)

    Meibom, Anders; Petaev, Mikhail I.; Krot, Alexander N.; Keil, Klaus; Wood, John A.

    2001-12-01

    Chemically zoned FeNi metal grains in the metal-rich chondrites QUE 94411 and Hammadah at Hamra 237 formed by gas-solid condensation in the temperature range from ~1500 to 1400 K during highly energetic thermal events in the solar nebula. We observe a linear correlation between the apparent diameter of the zoned FeNi metal grains and their inferred condensation temperature interval, which indicates that the grain growth rate was essentially constant. This lends strong support for a kinetic ``hit-and-stick'' growth model that yields growth timescales of ~20-85 hours and gas cooling rates of ~1-2 Kh-1 for six representative zoned metal grains studied in QUE 94411. In the core regions of the zoned metal grains the Ni concentration is systematically lower than the thermodynamically predicted values, suggesting that solid-state diffusion played an important role in shaping the zoning profiles. Combined with existing data, our observations provide a set of constraints on the physics and chemistry of large-scale, high-temperature processes in the earliest solar nebula, which present astrophysicists with profound challenges.

  9. Observational constraints on the global atmospheric CO sub 2 budget

    SciTech Connect

    Tans, P.P. ); Fung, I.Y. ); Takahashi, Taro )

    1990-03-23

    Observed atmospheric concentrations of CO{sub 2} and data on the partial pressures of CO{sub 2} in surface ocean waters are combined to identify globally significant sources and sinks of CO{sub 2}. The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO{sub 2} are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO{sub 2} in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO{sub 2}. Therefore, a large amount of the CO{sub 2} is apparently absorbed on the continents by terrestrial ecosystems. 39 refs., 5 figs., 4 tabs.

  10. Observational constraints on the global atmospheric CO2 budget

    NASA Technical Reports Server (NTRS)

    Tans, Pieter P.; Fung, Inez Y.; Takahashi, Taro

    1990-01-01

    Observed atmospheric concentrations of CO2 and data on the partial pressures of CO2 in surface ocean waters are combined to identify globally significant sources and sinks of CO2. The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO2 are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO2 in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO2. Therefore, a large amount of the CO2 is apparently absorbed on the continents by terrestrial ecosystems.

  11. Observational constraints in scalar tensor theory with tachyonic potential

    SciTech Connect

    Farajollahi, Hossein; Salehi, Amin; Shahabi, Asieh E-mail: a.salehi@guilan.ac.ir

    2011-10-01

    We study the dynamics of the scalar tensor cosmological model in the presence of tachyon field. In an alternative approach, in two exponential and power law form of the scalar field functions in the model, field equations are solved by simultaneously best fitting the model parameters with the most recent observational data. This approach gives us an observationally verified interpretation of the dynamics of the universe. We then discuss the best fitted of equation of state parameter, the statefinder parameters and the reconstructed scalar field in the model.

  12. Observational constraints for climate forcing by biomass burning aerosols

    NASA Astrophysics Data System (ADS)

    Penner, J. E.; Zhou, C.; Prather, M. J.; Xu, L.

    2012-12-01

    Estimates of sources of aerosols from open biomass burning vary to a significant extent, and those for pre-industrial emissions are even more uncertain. Previously, we showed how the use of a global chemical transport model together with TOMS satellite data for aerosol index and black carbon (BC) concentrations in ice-cores can be used to constrain present-day (PD) (year 2000) and pre-industrial (PI) (year 1870) emissions. The total aerosol forcing (direct and warm cloud indirect) from these emissions was estimated to be -0.065 W m-2, although values as large as -0.21 W m-2 could not be excluded. Here, we further examine the consistency between our estimates of biomass burning sources and observations of the spectrally varying AAOD from AERONET. We present adjusted estimates that also include these observations.

  13. The current status of observational constraints on cosmic strings

    SciTech Connect

    Caldwell, R.R.

    1993-10-01

    The observational restrictions on the cosmic string scenario for the formation of large scale structure are evaluated. this restrictions are due to the spectrum of gravitational radiation emitted by oscillating string loops, anisotropies in the cosmic microwave background caused by the strings, and evaporating black holes formed from collapsed cosmic string loops. It is shown that the only free parameter of the scenario, the cosmic string mass-per-unit-length, {mu}, is severely restricted.

  14. Observational Constraints of Humidity Climatology From GPS Radio Occultation measurements

    NASA Astrophysics Data System (ADS)

    Vergados, P.; Jiang, J. H.; Su, H.; Mannucci, A. J.

    2014-12-01

    Recent studies have shown large differences in the humidity climatology of the upper troposphere (UT) region between global models and observations. Such discrepancies can lead to large differences in the water vapor feedback estimations between models, reanalyses and satellite observations, and therefore climate projection uncertainties. Global Circulation Models (GCMs) could also mischaracterize the middle troposphere moist convection leading to erroneous conclusions about the water vapor vertical distribution and horizontal transport. We observationally constrain the UT humidity by employing high accuracy (<1.0%) and high vertical resolution (100-200 m) Global Positioning System Radio Occultation (GPSRO) refractivity measurements. Preliminary results from GPSRO reveal a significantly drier tropical boundary layer than both ECMWF and MERRA reanalyses. In the middle and upper troposphere, GPSRO is moister than ECMWF but drier than MERRA. These features are more pronounced at equatorial latitudes. These differences could have greater repercussions with regards to the water vapor feedback estimation. Also, zonally varying distributions of relative humidity (RH) from GPSRO, MERRA and ECMWF were also correlated with precipitation measurements from the Global Precipitation Climatology Project (GPCP). We found latitudinal differences between maxima of precipitation and RH, which could imply that large-scale horizontal transport in the boundary layer plays a critical role to governing the coupling strength between precipitation and RH. The application of GPSRO data in constraining the underlying model physics will be discussed.

  15. Revisiting the constraints on annihilating dark matter by the radio observational data of M31

    NASA Astrophysics Data System (ADS)

    Chan, Man Ho

    2016-07-01

    Recent gamma-ray observations and radio observations put strong constraints on the parameters of dark matter annihilation. In this article, we derive new constraints for six standard model annihilation channels by using the recent radio data of the M31 galaxy. The new constraints are generally tighter than the constraints obtained from 6 years of Fermi Large Area Telescope gamma-ray observations of the Milky Way dwarf spheroidal satellite galaxies. The conservative lower limits of dark matter mass annihilating via b b ¯, μ+μ- and τ+τ- channels are 90, 90 and 80 GeV respectively with the canonical thermal relic cross section and the Burkert profile being the dark matter density profile. Hence, our results do not favor the most popular models of the dark matter interpretation of the Milky Way GeV gamma-ray excess.

  16. Observational constraints on cosmological models with Chaplygin gas and quadratic equation of state

    NASA Astrophysics Data System (ADS)

    Sharov, G. S.

    2016-06-01

    Observational manifestations of accelerated expansion of the universe, in particular, recent data for Type Ia supernovae, baryon acoustic oscillations, for the Hubble parameter H(z) and cosmic microwave background constraints are described with different cosmological models. We compare the ΛCDM, the models with generalized and modified Chaplygin gas and the model with quadratic equation of state. For these models we estimate optimal model parameters and their permissible errors with different approaches to calculation of sound horizon scale rs(zd). Among the considered models the best value of χ2 is achieved for the model with quadratic equation of state, but it has 2 additional parameters in comparison with the ΛCDM and therefore is not favored by the Akaike information criterion.

  17. Properties of galactic dark matter: Constraints from astronomical observations

    SciTech Connect

    Burch, B.; Cowsik, R.

    2013-12-10

    The distributions of normal matter and of dark matter in the Galaxy are coupled to each other as they both move in the common gravitational potential. In order to fully exploit this interplay and to derive the various properties of dark matter relevant to their direct and indirect detection, we have comprehensively reviewed the astronomical observations of the spatial and velocity distributions of the components of normal matter. We then postulate that the phase-space distribution of dark matter follows a lowered-isothermal form and self-consistently solve Poisson's equation to construct several models for the spatial and velocity distributions of dark matter. In this paper, we compute the total gravitational potential of the normal and dark matter components and investigate their consistency with current observations of the rotation curve of the Galaxy and of the spatial and velocity distributions of blue horizontal-branch and blue straggler stars. Even with this demand of consistency, a large number of models with a range of parameters characterizing the dark matter distribution remain. We find that the best choice of parameters, within the range of allowed values for the surface density of the disk 55 M {sub ☉} pc{sup –2}, are the following: the dark matter density at the Galactic center ρ{sub DM,} {sub c} ≈ 100-250 GeV cm{sup –3}, the local dark matter density ρ{sub DM}(R {sub 0}) ≈ 0.56-0.72 GeV cm{sup –3}, and the rms speed of dark matter particles 〈v{sub DM}{sup 2}(R{sub 0})〉{sup 1/2}≈490−−550 km s{sup –1}. We also discuss possible astronomical observations that may further limit the range of the allowed models. The predictions of the allowed models for direct and indirect detection will be discussed separately in a companion paper.

  18. Rastall’s cosmology and its observational constraints

    SciTech Connect

    Fabris, Júulio C.; Piattella, Oliver F.; Rodrigues, Davi C.; Daouda, Mahamadou H.

    2015-03-26

    The Rastall’s theory is a modification of General Relativity touching one of the cornestone of gravity theory: the conservation laws. In Rastall’s theory, the energy-momentum tensor is not conserved anymore, depending now on the gradient of the Ricci curvature. In this sense, this theory can be seen as a classical implementation of quantum effects in a curved background space-time. We exploit this structure in order to reproduce some results of an effective theory of quantum loop cosmology. Later, we propose a model for the dark sector of the universe. In this case, the corresponding ΛCDM model appears as the only model consistent with observational data.

  19. OBSERVATIONAL CONSTRAINTS ON METHANOL PRODUCTION IN INTERSTELLAR AND PREPLANETARY ICES

    SciTech Connect

    Whittet, D. C. B.; Cook, A. M.; Herbst, Eric; Chiar, J. E.; Shenoy, S. S.

    2011-11-20

    Methanol (CH{sub 3}OH) is thought to be an important link in the chain of chemical evolution that leads from simple diatomic interstellar molecules to complex organic species in protoplanetary disks that may be delivered to the surfaces of Earthlike planets. Previous research has shown that CH{sub 3}OH forms in the interstellar medium predominantly on the surfaces of dust grains. To enhance our understanding of the conditions that lead to its efficient production, we assemble a homogenized catalog of published detections and limiting values in interstellar and preplanetary ices for both CH{sub 3}OH and the other commonly observed C- and O-bearing species, H{sub 2}O, CO, and CO{sub 2}. We use this catalog to investigate the abundance of ice-phase CH{sub 3}OH in environments ranging from dense molecular clouds to circumstellar envelopes around newly born stars of low and high mass. Results show that CH{sub 3}OH production arises during the CO freezeout phase of ice-mantle growth in the clouds, after an ice layer rich in H{sub 2}O and CO{sub 2} is already in place on the dust, in agreement with current astrochemical models. The abundance of solid-phase CH{sub 3}OH in this environment is sufficient to account for observed gas-phase abundances when the ices are subsequently desorbed in the vicinity of embedded stars. CH{sub 3}OH concentrations in the ices toward embedded stars show order-of-magnitude object-to-object variations, even in a sample restricted to stars of low mass associated with ices lacking evidence of thermal processing. We hypothesize that the efficiency of CH{sub 3}OH production in dense cores and protostellar envelopes is mediated by the degree of prior CO depletion.

  20. Constraints on Chariklo's rings from HST and VLT observations

    NASA Astrophysics Data System (ADS)

    Sicardy, Bruno; Buie, Marc W.; Benedetti-Rossi, Gustavo; Braga-Ribas, Felipe; Bueno de Camargo, Julio I.; Duffard, Rene; Ortiz, Jose Luis; Gratadour, Damien; Dumas, Christophe

    2015-11-01

    In June 2013, a stellar occultation revealed for the first time ever the presence of two dense and narrow rings around a small object of the solar system, the Centaur (10199) Chariklo (Braga-Ribas et al., Nature 508, 72, 2014). This body follows an eccentric orbit between Saturn and Uranus, with perihelion and aphelion distances of 13.1 and 18.5 AU. Due to Uranus perturbations, its orbit is unstable on the very short time scale of ~10 Myr (Horner at al. MNRAS 354, 798, 2004). The two rings (C1R and C2R, respectively) have orbital radii aC1R= 390.6±3.3 km and aC2R= 404.8±3.3 km, and typical widths WC1R ~6.5 km and WC2R ~2 km, optical depths τC1R ~ 0.4 and τC1R ~ 0.06, with a gap of ~9 km between the two. Chariklo's radius, RC~ 120 km (Duffard et al. AA 568, A79, 2014 Fornasier et al. AA 518, L11, 2014), implies that the ring system lies at 3.3-3.4 RC, farther away than the classical Roche limit of 2.4 RC that would be obtained for spherical ring particles with the same density as Chariklo.To better understand Chariklo's surroundings, and thus the origin of the rings, direct imaging of Chariklo has been performed using HST and VLT, with respectively 3 visits and 2 runs performed between April and August 2015. The HST images were obtained with the WFC3/UVIS camera with filters F300X (250-350 nm), F475X (400-650 nm) and F350LP (300-1000 nm), and typical PSF size of 30 milli-arcsec (mas), corresponding to about 300~km at Chariklo. Conversely, the SPHERE high contrast instrument at ESO VLT provided images in the near IR (Y, J and H bands), with typical expected PSF sizes of 30-40 mas (300-400~km at Chariklo). The main goals of those observations were: (1) obtain direct images of the rings, confirming their geometry and their orientation, (2) derive multi-wavelength photometry, thus constraining their composition (concerning in particular the presence of water ice), (3) perform a deep search of small satellites (down to a few km in diameter), (4) faint dusty rings

  1. Volcanic lightning: global observations and constraints on source mechanisms

    NASA Astrophysics Data System (ADS)

    McNutt, Stephen R.; Williams, Earle R.

    2010-12-01

    Lightning and electrification at volcanoes are important because they represent a hazard in their own right, they are a component of the global electrical circuit, and because they contribute to ash particle aggregation and modification within ash plumes. The role of water substance (water in all forms) in particular has not been well studied. Here data are presented from a comprehensive global database of volcanic lightning. Lightning has been documented at 80 volcanoes in association with 212 eruptions. The Volcanic Explosivity Index (VEI) could be determined for 177 eruptions. Eight percent of VEI = 3-5 eruptions have reported lightning, and 10% of VEI = 6, but less than 2% of those with VEI = 1-2. These findings suggest consistent reporting for larger eruptions but either less lightning or possible under-reporting for small eruptions. Ash plume heights (142 observations) show a bimodal distribution with main peaks at 7-12 km and 1-4 km. The former are similar to heights of typical thunderstorms and suggest involvement of water substance, whereas the latter suggest other factors contributing to electrical behavior closer to the vent. Reporting of lightning is more common at night (56%) and less common in daylight (44%). Reporting also varied substantially from year to year, suggesting that a more systematic observational strategy is needed. Several weak trends in lightning occurrence based on magma composition were found. The bimodal ash plume heights are obvious only for andesite to dacite; basalt and basaltic-andesite evenly span the range of heights; and rhyolites are poorly represented. The distributions of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes, which is generally flat with latitude. Meteorological lightning, on the other hand, is common in the tropics and decreases markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward. This finding

  2. Constraints on Cumulus Parameterization from Simulations of Observed MJO Events

    NASA Technical Reports Server (NTRS)

    Del Genio, Anthony; Wu, Jingbo; Wolf, Audrey B.; Chen, Yonghua; Yao, Mao-Sung; Kim, Daehyun

    2015-01-01

    Two recent activities offer an opportunity to test general circulation model (GCM) convection and its interaction with large-scale dynamics for observed Madden-Julian oscillation (MJO) events. This study evaluates the sensitivity of the Goddard Institute for Space Studies (GISS) GCM to entrainment, rain evaporation, downdrafts, and cold pools. Single Column Model versions that restrict weakly entraining convection produce the most realistic dependence of convection depth on column water vapor (CWV) during the Atmospheric Radiation Measurement MJO Investigation Experiment at Gan Island. Differences among models are primarily at intermediate CWV where the transition from shallow to deeper convection occurs. GCM 20-day hindcasts during the Year of Tropical Convection that best capture the shallow–deep transition also produce strong MJOs, with significant predictability compared to Tropical Rainfall Measuring Mission data. The dry anomaly east of the disturbance on hindcast day 1 is a good predictor of MJO onset and evolution. Initial CWV there is near the shallow–deep transition point, implicating premature onset of deep convection as a predictor of a poor MJO simulation. Convection weakly moistens the dry region in good MJO simulations in the first week; weakening of large-scale subsidence over this time may also affect MJO onset. Longwave radiation anomalies are weakest in the worst model version, consistent with previous analyses of cloud/moisture greenhouse enhancement as the primary MJO energy source. The authors’ results suggest that both cloud-/moisture-radiative interactions and convection–moisture sensitivity are required to produce a successful MJO simulation.

  3. An observational radiative constraint on hydrologic cycle intensification

    NASA Astrophysics Data System (ADS)

    Hall, A. D.; DeAngelis, A. M.; Qu, X.; Zelinka, M. D.

    2015-12-01

    Hydrologic cycle intensification is a key dimension of climate change, with significant impacts on human and natural systems. A basic measure of hydrologic cycle intensification, the increase in global-mean precipitation per unit surface warming, varies by a factor of three in current-generation climate models (~1-3 % K-1). We show that a substantial portion of this spread can be traced to intermodel variations in the atmospheric shortwave absorption response to greenhouse-gas-induced warming. As climate warms, increases in shortwave absorption suppress the precipitation increase by reducing the latent heating required to balance the atmospheric energy budget. Spread in the shortwave absorption response can be explained by differences in the sensitivity of solar absorption to variations in column precipitable water. An observational estimate suggests that in many models, this sensitivity is too small, and that the shortwave absorption response to warming is too weak. Spread in the simulated sensitivity of solar absorption to varying water vapor concentration is linked to differences in radiative transfer parameterizations. Attaining accurate shortwave absorption responses through radiative transfer scheme improvement could reduce spread in global precipitation increase per unit warming at the end of the 21st century by ~35%, and produce an ensemble-mean increase that is almost 40% smaller.

  4. Titan's Enigmatic Magnetized Ionosphere: Further Observational Constraints for Models

    NASA Astrophysics Data System (ADS)

    Luhmann, Janet; Ulusen, D.; Mandt, K.; Waite, J. H.; Wei, H.; Ma, Y.; Russell, C. T.; Cravens, T. E.

    2009-09-01

    Titan's ionospheric interaction with Saturn's magnetospheric plasma and field has since Voyager's first flyby been likened to the solar wind interaction with Venus. Indeed the Cassini observations of the ionosphere suggest a strong solar EUV control over the densities, with only modest magnetospheric ionization sources on a typical close flyby above 900 km. However the changing aspect of the incident, usually magnetospheric, plasma with respect to the subsolar ionosphere seems to produce a much more complicated behavior of the ionospheric magnetization than even that suggested by state-of-the-art simulations of the Titan- plasma interaction. Our study focuses on the simple question of whether the combined data sets from the Cassini Ion Neutral Mass Spectrometer and the Magnetometer reveal patterns of the ionospheric magnetization. We consider organizations by solar zenith angle, nominal corotating plasma ram angle, Titan longitude, and Saturn Local time, as well as combinations of these and other parameters. The variability of the external conditions of the external plasma and magnetic field seem to impair, but not completely mask, some anticipated features. The results raise the question of whether such patterns are now clearer as this current solar minimum has progressed, with its low solar wind pressure perhaps quieting the magnetospheric environment at 20 Rs.

  5. Direct observation of lubricant additives using tomography techniques

    NASA Astrophysics Data System (ADS)

    Chen, Yunyun; Sanchez, Carlos; Parkinson, Dilworth Y.; Liang, Hong

    2016-07-01

    Lubricants play important roles in daily activities such as driving, walking, and cooking. The current understanding of mechanisms of lubrication, particularly in mechanical systems, has been limited by the lack of capability in direct observation. Here, we report an in situ approach to directly observe the motion of additive particles in grease under the influence of shear. Using the K-edge tomography technique, it is possible to detect particular additives in a grease and observe their distribution through 3D visualization. A commercial grease as a reference was studied with and without an inorganic additive of Fe3O4 microparticles. The results showed that it was possible to identify these particles and track their movement. Under a shear stress, Fe3O4 particles were found to adhere to the edge of calcium complex thickeners commonly used in grease. Due to sliding, the grease formed a film with increased density. This approach enables in-line monitoring of a lubricant and future investigation in mechanisms of lubrication.

  6. Giant Planets in Open Clusters and Binaries: Observational Constraints on Migration

    NASA Astrophysics Data System (ADS)

    Quinn, Samuel N.; White, Russel J.; Latham, David W.; Buchhave, Lars A.; Torres, Guillermo

    2016-01-01

    Some giant planets migrate from their birthplace beyond the ice line to short-period orbits just a fraction of an AU from their host stars. Though many theories have been proposed, it is not yet clear which mechanism is most important for migration, and by extension, in which types of planetary system we can expect a greater prevalence of disruptive gas giant migration. One way to constrain this process is to observe the orbital properties of migrating planets, which are expected to be shaped according to the mode of migration: in general, interaction with the gas disk should produce circular, coplanar orbits, while multi-body processes stir up eccentricities and inclinations. Unfortunately, tidal and magnetic interactions between hot Jupiters and their host stars can obscure these differences by damping eccentricities and inclinations over time, so the most direct constraints will come from difficult-to-observe young systems. Additional constraints on migration can be obtained by observing the architectures of systems containing short-period giant planets: if an outer companion is often responsible for driving migration, there should be a higher incidence of massive companions on wide orbits in hot Jupiter systems than in systems not hosting a short-period giant planet. Further, the properties of these outer companions can help differentiate between multi-body migration mechanisms. We describe two complementary surveys that we have carried out to address these problems. The first, a precise radial-velocity survey in nearby adolescent (100-600 Myr) open clusters, characterizes the orbits of giant planets soon after migration. The second, an adaptive optics imaging survey of hot Jupiter host stars, constrains the population of wide companions in hot Jupiter systems. We present the results from these two surveys and discuss the orbital properties and system architectures of our discoveries in the context of giant planet migration.

  7. Observational constraints on atmospheric radiaitve feedbacks: absolute accuracy and next-generation observing systems

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Hanssen, L. M.; Mekhontsev, S.; Anderson, J.

    2012-12-01

    The central role of atmospheric radiative feedbacks to understanding and projecting climate change calls for a robust observational system. Recent studies have shown the value of space-based measurements for putting quantitative constraints on a range of radiative feedback processes through a fingerprinting method applied to long-term observational records. More recent work has suggested the value of demonstrably accurate measurements to disentangle model error from observational uncertainties within reanalysis systems, potentially yielding improved representations of feedback processes within just a few years. Both of these methods rely on space-based measurements that can be objectively tested for accuracy on-orbit. A new class of mission has been proposed that incorporates the same type of empirical tests for accuracy as used in the laboratory into a space-based sensor. One example of such a mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO), a new mission suggested by the 2006 National Research Council Decadal Survey. CLARREO includes three sensor types: thermal infrared, microwave, and reflected shortwave. This paper presents a laboratory demonstration of prototype systems for testing the on-orbit accuracy of a thermal infrared sensor for CLARREO. These systems utilize infrared lasers to provide monochromatic light sources to quantitatively determine the optical properties of materials. These infrared optical properties are major determinants of the on-orbit radiometric performance of a thermal infrared sensor. For this reason, reliable quantitative information (including uncertainty) that tracks any changes in relevant infrared materials over the mission lifetime is essential to objective assessment of instrument accuracy. The practicality of mid-infrared lasers for these applications is due to the availability and continued evolution of compact, high-efficiency Quantum Cascade Lasers (QCLs). These lasers can provide over 100 m

  8. Constraints on Lorentz Invariance Violation from Fermi -Large Area Telescope Observations of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Vasileiou, V.; Jacholkowska, A.; Piron, F.; Bolmont, J.; Courturier, C.; Granot, J.; Stecker, Floyd William; Cohen-Tanugi, J.; Longo, F.

    2013-01-01

    We analyze the MeV/GeV emission from four bright Gamma-Ray Bursts (GRBs) observed by the Fermi-Large Area Telescope to produce robust, stringent constraints on a dependence of the speed of light in vacuo on the photon energy (vacuum dispersion), a form of Lorentz invariance violation (LIV) allowed by some Quantum Gravity (QG) theories. First, we use three different and complementary techniques to constrain the total degree of dispersion observed in the data. Additionally, using a maximally conservative set of assumptions on possible source-intrinsic spectral-evolution effects, we constrain any vacuum dispersion solely attributed to LIV. We then derive limits on the "QG energy scale" (the energy scale that LIV-inducing QG effects become important, E(sub QG)) and the coefficients of the Standard Model Extension. For the subluminal case (where high energy photons propagate more slowly than lower energy photons) and without taking into account any source-intrinsic dispersion, our most stringent limits (at 95% CL) are obtained from GRB 090510 and are E(sub QG,1) > 7.6 times the Planck energy (E(sub Pl)) and E(sub QG,2) > 1.3×10(exp 11) GeV for linear and quadratic leading order LIV-induced vacuum dispersion, respectively. These limits improve the latest constraints by Fermi and H.E.S.S. by a factor of approx. 2. Our results disfavor any class of models requiring E(sub QG,1) < or approx. E(sub Pl)

  9. Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation

    NASA Technical Reports Server (NTRS)

    Brearley, A. J.

    1998-01-01

    There have been presented several intriguing observations suggesting evidence of fossil life in martian orthopyroxenite ALH 84001. These exciting and controversial observations have stimulated extensive debate over the origin and history of ALH 84001, but many issues still remain unresolved. Among the most important is the question of the temperature at which the carbonates, which host the putative microfossils, formed. Oxygen- isotopic data, while showing that the carbonates are generally out of isotopic equilibria with the host rock, cannot constrain their temperature of formation. Both low- and high-temperature scenarios are plausible depending on whether carbonate growth occurred in an open or closed system. Petrographic arguments have generally been used to support a high-temperature origin but these appear to be suspect because they assume equilibrium between carbonate compositions that are not in contact. Some observations appear to be consistent with shock mobilization and growth from immiscible silicate-carbonate melts at high temperatures. Proponents of a low-temperature origin for the carbonates are hampered by the fact that there is currently no evidence of hydrous phases that would indicate low temperatures and the presence of a hydrous fluid during the formation of the carbonates. However, the absence of hydrous phases does not rule out carbonate formation at low temperatures, because the carbonate forming fluids may have been extremely CO2 rich, such that hydrous phases would not have been stabilized. In this study, I have carried out additional Transmission electron microscopy (TEM) studies of ALH-84001 and have found evidence of very rare phyllosilicates, which appear to be convincingly of pre-terrestrial origin. At present these observations are limited to one occurrence: further studies are in progress to determine if the phyllosilicates are more widespread.

  10. Constraints on Deceleration Parameter of a 5D Bounce Cosmological Model from Recent Cosmic Observations

    NASA Astrophysics Data System (ADS)

    Li, Jie-Chao; Xu, Li-Xin; Lü, Jian-Bo; Chang, Bao-Rong; Liu, Hong-Ya

    2008-02-01

    We study the constraint on deceleration parameter q from the recent SNeIa Gold dataset and observational Hubble data by using a model-independent deceleration parameter q(z) = ½ a/(1 + z)b under the five-dimensional bounce cosmological model. For the cases of SNeIa Gold dataset, Hubble data, and their combination, the present results show that the constraints on transition redshift zT are 0.35+0.14-0.07, 0.68+1.47 0.58, and 0.55+0.18-0.09 with 1σ errors, respectively.

  11. Observational Constraints on Low-Mass Stellar Evolution and Planet Formation

    NASA Astrophysics Data System (ADS)

    Birkby, Jayne Louise

    2011-07-01

    Low-mass stars (? < 1.0M⊙) account for more than 70% of the galactic stellar population yet models describing the evolution of their fundamental properties lack stringent observational constraints, especially at early ages. Furthermore, recent observations indicate a significant discrepancy between model predictions and the precise (2 - 3%) observed, dynamical masses and radii measured using low-mass eclipsing binary systems (EBs). Additionally, the theory of planet formation via core accretion predicts notably less hot-Jupiter formation around M-dwarfs (Mdot ? ≤ 0.6M⊙), but as yet, no large enough study exists to robustly test it. Further still, it is predicted that the dynamic environment of stellar clusters, in which most stars are believed to form, hampers planet formation, but again, current null detections of planets in stellar clusters are not statistically significant to test the theory. More observations are required to cement both the theory of low-mass stellar evolution and planet formation. This thesis aims to provide the necessary constraints by uncovering new low-mass EBs and transiting exoplanets in time-series photometry and follow-up spectroscopy from the Monitor project, a photometric monitoring campaign of low-mass stars in nine young open clusters, and in the WFCAM Transit Survey (WTS), a photometric monitoring campaign of ∼10,000 field M-dwarfs. Chapters 3 and 4 present my study of the young (130 Myr) cluster, M 50. I confirm three EB candidates as cluster members, including evidence that one of these is in a triple system with a wide-separation, low-mass tertiary component. The derived masses and radii for this system and one further double-lined, non-cluster member are presented, but these objects required dedicated, single-slit spectroscopic follow-up to yield the accuracy required to test pre-main sequence models. My non-detection of planets in this cluster is consistent with the results of all other cluster transit surveys. The

  12. Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

    NASA Astrophysics Data System (ADS)

    Hernández-Martínez, L.; Carigi, L.; Peña, M.; Peimbert, M.

    2011-11-01

    Aims: Chemical evolution models are useful for understanding the formation and evolution of stars and galaxies. Model predictions will be more robust when more observational constraints are used. We present chemical evolution models for the dwarf irregular galaxy NGC 6822 using chemical abundances of old and young planetary nebulae (PNe) and H ii regions as observational constraints. We use two sets of chemical abundances, one derived from collisionally excited lines (CELs) and one from recombination lines (RLs). We use our models as a tool to distinguish between both procedures for abundance determinations. Methods: In our chemical evolution code the chemical contribution of low and intermediate mass stars is time-delayed, while for the massive stars the chemical contribution follows the instantaneous recycling approximation. Our models have two main free parameters: the mass-loss rate of a well-mixed outflow and the upper mass limit, Mup, of the initial mass function (IMF). To reproduce the gaseous mass and the present-day O/H value we need to vary the outflow rate and the Mup value. Results: We calculate two models with different Mup values that reproduce the constraints adequately. The abundances of old PNe agree with our models and support the star-formation history derived independently from photometric data. Both require an early well-mixed wind, lasting 5.3 Gyr, to reproduce the observed gaseous mass in the galaxy. In addition, by assuming a fraction of binaries producing SNIa of 1%, the models fit the Fe/H abundance ratio as derived from A supergiants. The first model (M4C), which assumes Mup = 40 M⊙, fits within errors smaller than 2σ the O/H, Ne/H, S/H, Ar/H and Cl/H abundances obtained from CELs for old and young PNe and H ii regions. The second model (M1R), which adopts Mup = 80 M⊙, reproduces within 2σ errors the O/H, C/H, Ne/H and S/H abundances adopted from RLs. Both models reproduce the increase of the O, Ne, S, and Ar elements during the

  13. Constraints on the Energy Content of the Universe from a Combination of Galaxy Cluster Observables

    NASA Technical Reports Server (NTRS)

    Molnar, Sandor M.; Haiman, Zoltan; Birkinshaw, Mark; Mushotzky, Richard F.

    2003-01-01

    We demonstrate that constraints on cosmological parameters from the distribution of clusters as a function of redshift (dN/dz) are complementary to accurate angular diameter distance (D(sub A)) measurements to clusters, and their combination significantly tightens constraints on the energy density content of the Universe. The number counts can be obtained from X-ray and/or SZ (Sunyaev-Ze'dovich effect) surveys, and the angular diameter distances can be determined from deep observations of the intra-cluster gas using their thermal bremsstrahlung X-ray emission and the SZ effect. We combine constraints from simulated cluster number counts expected from a 12 deg(sup 2) SZ cluster survey and constraints from simulated angular diameter distance measurements based on the X-ray/SZ method assuming a statistical accuracy of 10% in the angular diameter distance determination of 100 clusters with redshifts less than 1.5. We find that Omega(sub m), can be determined within about 25%, Omega(sub lambda) within 20% and w within 16%. We show that combined dN/dz+(sub lambda) constraints can be used to constrain the different energy densities in the Universe even in the presence of a few percent redshift dependent systematic error in D(sub lambda). We also address the question of how best to select clusters of galaxies for accurate diameter distance determinations. We show that the joint dN/dz+ D(lambda) constraints on cosmological parameters for a fixed target accuracy in the energy density parameters are optimized by selecting clusters with redshift upper cut-offs in the range 0.55 approx. less than 1. Subject headings: cosmological parameters - cosmology: theory - galaxies:clusters: general

  14. Progenitor constraints for core-collapse supernovae from Chandra X-ray observations

    NASA Astrophysics Data System (ADS)

    Heikkilä, T.; Tsygankov, S.; Mattila, S.; Eldridge, J. J.; Fraser, M.; Poutanen, J.

    2016-03-01

    The progenitors of hydrogen-poor core-collapse supernovae (SNe) of Types Ib, Ic and IIb are believed to have shed their outer hydrogen envelopes either by extremely strong stellar winds, characteristic of classical Wolf-Rayet stars, or by binary interaction with a close companion star. The exact nature of the progenitors and the relative importance of these processes are still open questions. One relatively unexplored method to constrain the progenitors is to search for high-mass X-ray binaries (HMXBs) at SN locations in pre-explosion X-ray observations. In an HMXB, one star has already exploded as a core-collapse SN, producing a neutron star or a stellar mass black hole. It is likely that the second star in the system will also explode as an SN, which should cause a detectable long-term change in the system's X-ray luminosity. In particular, a pre-explosion detection of an HMXB coincident with an SN could be informative about the progenitor's nature. In this paper, we analyse pre-explosion ACIS observations of 18 nearby Type Ib, Ic and IIb SNe from the Chandra X-ray observatory public archive. Two sources that could potentially be associated with the SN are identified in the sample. Additionally we make similar post-explosion measurements for 46 SNe. Although our modelling indicates that progenitor systems with compact binary companions are probably quite rare, studies of this type can in the future provide more stringent constraints as the number of discovered nearby SNe and suitable pre-explosion X-ray data are both increasing.

  15. Constraints on the Recent Rate of Lunar Regolith Accumulation from Diviner Observations

    NASA Technical Reports Server (NTRS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.

    2012-01-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances pre dicted to be covered by continuous ejecta. However, most of these sur faces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrar ed observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperat ures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highla nds), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth . Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differen ces in the thickness of accumulated regolith. However, away from youn g craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculat ed H values for young craters show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42, abstract 2437). This method could, in principle, be extended to other

  16. Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters

    SciTech Connect

    Dugger, Leanna; Profumo, Stefano; Jeltema, Tesla E. E-mail: tesla@ucolick.org

    2010-12-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results put strong constraints on the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as those from galaxy clusters, while still improving on previous constraints in some cases.

  17. Constraints on Lorentz Invariance Violation using integral/IBIS observations of GRB041219A

    NASA Astrophysics Data System (ADS)

    Laurent, P.; Götz, D.; Binétruy, P.; Covino, S.; Fernandez-Soto, A.

    2011-06-01

    One of the experimental tests of Lorentz invariance violation is to measure the helicity dependence of the propagation velocity of photons originating in distant cosmological obejcts. Using a recent determination of the distance of the gamma-ray burst GRB 041219A, for which a high degree of polarization is observed in the prompt emission, we are able to improve by four orders of magnitude the existing constraint on Lorentz invariance violation, arising from the phenomenon of vacuum birefringence.

  18. The Role of Additional Processing Time and Lexical Constraint in Spoken Word Recognition

    ERIC Educational Resources Information Center

    LoCasto, Paul C.; Connine, Cynthia M.; Patterson, David

    2007-01-01

    Three phoneme monitoring experiments examined the manner in which additional processing time influences spoken word recognition. Experiment 1a introduced a version of the phoneme monitoring paradigm in which a silent interval is inserted prior to the word-final target phoneme. Phoneme monitoring reaction time decreased as the silent interval…

  19. The Disciplinary Constraints of SLA and TESOL: Additive Bilingualism and Second Language Acquisition, Teaching and Learning

    ERIC Educational Resources Information Center

    May, Stephen

    2011-01-01

    For over 15 years now, various commentators have highlighted the 'monolingual bias' inherent in SLA and TESOL research, which invariably constructs bi/multilingualism in deficit terms. In contrast, these critics have advocated an additive bilingual approach to SLA and TESOL, albeit, not as yet to any great effect. In this paper, I explore why so…

  20. Observational constraints on the spectral index of the cosmological curvature perturbation

    NASA Astrophysics Data System (ADS)

    Lyth, David H.; Covi, Laura

    2000-11-01

    We evaluate the observational constraints on the spectral index n, in the context of the ΛCDM hypothesis which represents the simplest viable cosmology. We first take n to be practically scale independent. Ignoring reionization, we find at a nominal 2-σ level n~=1.0+/-0.1. If we make the more realistic assumption that reionization occurs when a fraction f~10-5 to 1 of the matter has collapsed, the 2-σ lower bound is unchanged while the 1-σ bound rises slightly. These constraints are compared with the prediction of various inflation models. Then we investigate the two-parameter scale-dependent spectral index, predicted by running-mass inflation models, and find that present data allow significant scale dependence of n, which occurs in a physically reasonable regime of parameter space.

  1. Constraints on the recent rate of lunar regolith accumulation from Diviner observations

    NASA Astrophysics Data System (ADS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.; Allen, C.; Paige, D. A.

    2012-12-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances predicted to be covered by continuous ejecta. However, most of these surfaces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrared observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperatures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highlands), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth. Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differences in the thickness of accumulated regolith. However, away from young craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculated H values for young craters (Giordano Bruno, Moore F, Byrgius A, Necho, Tycho, Jackson, King, and Copernicus) show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42

  2. Constraints on kinematic model from recent cosmic observations: SN Ia, BAO and observational Hubble data

    SciTech Connect

    Xu, Lixin; Li, Wenbo; Lu, Jianbo E-mail: liwenbo10@yahoo.com.cn

    2009-07-01

    In this paper, linear first order expansion of deceleration parameter q(z) = q{sub 0}+q{sub 1}(1−a) (M{sub 1}), constant jerk j = j{sub 0} (M{sub 2}) and third order expansion of luminosity distance (M{sub 3}) are confronted with cosmic observations: SCP 307 SN Ia, BAO and observational Hubble data (OHD). Likelihood is implemented to find the best fit model parameters. All these models give the same prediction of the evolution of the universe which is undergoing accelerated expansion currently and experiences a transition from decelerated expansion to accelerated expansion. But, the transition redshift depends on the concrete parameterized form of the model assumed. M{sub 1} and M{sub 2} give value of transition redshift about z{sub t} ∼ 0.6. M{sub 3} gives a larger one, say z{sub t} ∼ 1. The χ{sup 2}/dof implies almost the same goodness of the models. But, for its badness of evolution of deceleration parameter at high redshift z > 1, M{sub 3} can not be reliable. M{sub 1} and M{sub 2} are compatible with ΛCDM model at the 2σ and 1σ confidence levels respectively. M{sub 3} is not compatible with ΛCDM model at 2σ confidence level. From M{sub 1} and M{sub 2} models, one can conclude that the cosmic data favor a cosmological model having j{sub 0} < −1.

  3. Additional Observations for Quantifying Non-Darcian Flow (Invited)

    NASA Astrophysics Data System (ADS)

    Halford, K. J.

    2009-12-01

    Simulating non-Darcian flow in porous medium requires mathematical models that are mathematically more complex than Darcy's law and therefore require additional data for field-scale and regional characterization. Non-Darcian flow is affected by fluid velocity so flow logs and other geophysical tools are needed to identify flowing intervals and characterize mean pore diameter or fracture aperture. Flow-log interpretation often is complicated by vertical flow induced within and near the well by local contrasts in hydraulic conductivity. An effective wellbore analysis tool for simulating and evaluating complex well-aquifer system interaction is AnalyzeHOLE. In this analysis tool, the pumping well and adjacent aquifer system are simulated with an axisymmetric, radial geometry in a two-dimensional MODFLOW model. Non-Darcian flow occurs primarily in highly transmissive aquifers where environmental fluctuations can exceed drawdowns from pumping during aquifer tests. Attempts to accurately quantify drawdowns in highly transmissive aquifers must include a means to remove non-pumping fluctuations. Drawdown can be differentiated from environmental fluctuations by developing a synthetic response that simulates non-pumping water-level fluctuations during aquifer tests. The synthetic water-level response sums individual time-series of barometric pressure, tidal potential, and background water levels. Synthetic water levels are fit to measured water levels during unpumped conditions by adjusting the amplitude and phase of each component time series. Drawdowns of 0.01 m can be detected where environmental water-level fluctuations approach 1 m with the synthetic water-level approach, but continuous records are needed.

  4. Constraints on Solar Wind Acceleration Mechanisms from Ulysses Plasma Observations: The First Polar Pass

    NASA Technical Reports Server (NTRS)

    Barnes, Aaron; Gazis, Paul R.; Phillips, John L.

    1995-01-01

    The mass flux density and velocity of the solar wind at polar latitudes can provide strong constraints on solar wind acceleration mechanisms. We use plasma observations from the first polar passage of the Ulysses spacecraft to investigate this question. We find that the mass flux density and velocity are too high to reconcile with acceleration of the solar wind by classical thermal conduction alone. Therefore acceleration of the high-speed must involve extended deposition of energy by some other mechanism, either as heat or as a direct effective pressure, due possibly to waves and/or turbulence, or completely non-classical heat transport.

  5. Dynamical and observational constraints on satellites in the inner Pluto-Charon system

    NASA Technical Reports Server (NTRS)

    Stern, S. Alan; Parker, Joel William; Duncan, Martin J.; Snowdall, J. Clark, Jr.; Levison, Harold F.

    1994-01-01

    It is not known if Pluto has other satellites besides its massive partner Charon. In the past, searches for additional satellites in the Pluto-Charon system have extended from the solar-tidal stability boundary (approximately 90 arcsec from Pluto) inward to about 1 arcsec from Pluto. Here we further explore the inner (i.e., less than 10 arcsec) region of the Pluto-Charon system to determine where additional satellites might lie. In particular, we report on (1) dynamical simulations to delineate the region where unstable orbits lie around Charon, (2) dynamical simulations which use the low orbital eccentricity of Charon to constrain the mass of any third body near Pluto, and (3) analysis of Hubble Space Telescope (HST) archival images to search for satellites in the inner Pluto-Charon system. Although no objects were found, significant new constraints on bodies orbiting in the inner Pluto-Charon system were obtained.

  6. Integration of additional constraints to Inverse the differential kinematic model for a nonholonomic and redundant mobile manipulator

    NASA Astrophysics Data System (ADS)

    Akli, Isma; Achour, Noura

    2008-06-01

    This article presents a differential kinematic study for a car-like mobile system carrying a four degrees of freedom manipulator. The generalized coordinates and velocities of the mobile manipulator are required, when the position and the velocity of the end-effector are imposed in the cartesian space. Our approach consists of planning the motion of the mobile platform with make the onboard manipulator able to follow the cartesian trajectory. The resulted generalized coordinates are exploited to calculate the Forward Differential Kinematic Model. Since the mobile manipulator is redundant regarding to the task, we profit from the system characteristics to augment the jacobian matrix, while integrating additional constraints, to inverse the differential kinematic model.

  7. New observational constraints on the growth of the first supermassive black holes

    SciTech Connect

    Treister, E.; Schawinski, K.; Volonteri, M.; Natarajan, P.

    2013-12-01

    We constrain the total accreted mass density in supermassive black holes at z > 6, inferred via the upper limit derived from the integrated X-ray emission from a sample of photometrically selected galaxy candidates. Studying galaxies obtained from the deepest Hubble Space Telescope images combined with the Chandra 4 Ms observations of the Chandra Deep Field-South, we achieve the most restrictive constraints on total black hole growth in the early universe. We estimate an accreted mass density <1000 M {sub ☉} Mpc{sup –3} at z ∼ 6, significantly lower than the previous predictions from some existing models of early black hole growth and earlier prior observations. These results place interesting constraints on early black hole growth and mass assembly by accretion and imply one or more of the following: (1) only a fraction of the luminous galaxies at this epoch contain active black holes; (2) most black hole growth at early epochs happens in dusty and/or less massive—as yet undetected—host galaxies; (3) there is a significant fraction of low-z interlopers in the galaxy sample; (4) early black hole growth is radiatively inefficient, heavily obscured, and/or due to black hole mergers as opposed to accretion; or (5) the bulk of the black hole growth occurs at late times. All of these possibilities have important implications for our understanding of high-redshift seed formation models.

  8. Beyond the model democracy: observational constraints indicate risk of drying in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Shiogama, Hideo; Emori, Seita; Hanasaki, Naota; Abe, Manabu; Masutomi, Yuji; Takahashi, Kiyoshi; Nozawa, Toru

    2013-04-01

    Climate warming due to human activities will be accompanied by hydrological cycle changes. Economies, societies and ecosystems in South America (SA) are vulnerable to such water resource changes. Hence, water resource impact assessments for SA, and corresponding adaptation and mitigation policies, have attracted increased attention. However, substantial uncertainties remain in the current water resource assessments that are based on multiple coupled Atmosphere Ocean General Circulation models. This uncertainty varies from significant wetting to catastrophic drying. By applying a statistical method, we characterised the uncertainty and identified global-scale metrics for measuring the reliability of water resource assessments in SA. Here we show that, whereas the ensemble mean assessment suggested wetting across most of SA, the observational constraints indicate a higher probability of drying in the Amazon basin. Naive over-reliance on the consensus of models can lead to inappropriate decision making. Reference: Shiogama, H. et al. Observational constraints indicate risk of drying in the Amazon basin. Nature Communications 2:253 doi: 10.1038/ncomms1252 (2011).

  9. Constraints on the Intergalactic Magnetic Field with Gamma-Ray Observations of Blazars

    NASA Astrophysics Data System (ADS)

    Finke, Justin D.; Reyes, Luis C.; Georganopoulos, Markos; Reynolds, Kaeleigh; Ajello, Marco; Fegan, Stephen J.; McCann, Kevin

    2015-11-01

    Distant BL Lacertae objects emit γ-rays that interact with the extragalactic background light (EBL), creating electron-positron pairs, and reducing the flux measured by ground-based imaging atmospheric Cherenkov telescopes (IACTs) at very-high energies (VHE). These pairs can Compton-scatter the cosmic microwave background, creating a γ-ray signature at slightly lower energies that is observable by the Fermi Large Area Telescope (LAT). This signal is strongly dependent on the intergalactic magnetic field (IGMF) strength (B) and its coherence length (LB). We use IACT spectra taken from the literature for 5 VHE-detected BL Lac objects and combine them with LAT spectra for these sources to constrain these IGMF parameters. Low B values can be ruled out by the constraint that the cascade flux cannot exceed that observed by the LAT. High values of B can be ruled out from the constraint that the EBL-deabsorbed IACT spectrum cannot be greater than the LAT spectrum extrapolated into the VHE band, unless the cascade spectrum contributes a sizable fraction of the LAT flux. We rule out low B values (B ≲ 10-19 G for LB ≥ 1 Mpc) at >5σ in all trials with different EBL models and data selection, except when using >1 GeV spectra and the lowest EBL models. We were not able to constrain high values of B.

  10. Constraints on the Intergalactic Magnetic Field with Gamma-Ray Observations of Blazars

    NASA Astrophysics Data System (ADS)

    Finke, Justin D.; Reyes, Luis C.; Georganopoulos, Markos; Reynolds, Kaeleigh; Ajello, Marco; Fegan, Stephen J.; McCann, Kevin

    2015-11-01

    Distant BL Lacertae objects emit γ-rays that interact with the extragalactic background light (EBL), creating electron–positron pairs, and reducing the flux measured by ground-based imaging atmospheric Cherenkov telescopes (IACTs) at very-high energies (VHE). These pairs can Compton-scatter the cosmic microwave background, creating a γ-ray signature at slightly lower energies that is observable by the Fermi Large Area Telescope (LAT). This signal is strongly dependent on the intergalactic magnetic field (IGMF) strength (B) and its coherence length (LB). We use IACT spectra taken from the literature for 5 VHE-detected BL Lac objects and combine them with LAT spectra for these sources to constrain these IGMF parameters. Low B values can be ruled out by the constraint that the cascade flux cannot exceed that observed by the LAT. High values of B can be ruled out from the constraint that the EBL-deabsorbed IACT spectrum cannot be greater than the LAT spectrum extrapolated into the VHE band, unless the cascade spectrum contributes a sizable fraction of the LAT flux. We rule out low B values (B ≲ 10‑19 G for LB ≥ 1 Mpc) at >5σ in all trials with different EBL models and data selection, except when using >1 GeV spectra and the lowest EBL models. We were not able to constrain high values of B.

  11. New Constraints on Quantum Gravity from X-ray and Gamma-Ray Observationsα

    NASA Astrophysics Data System (ADS)

    Perlman, Eric S.; Rappaport, Saul A.; Christiansen, Wayne A.; Ng, Jack; DeVore, John; Pooley, David A.

    2016-01-01

    One aspect of the quantum nature of spacetime is its ``foaminess" at very small scales. Many models for spacetime foam are defined by the accumulation power α, which parameterizes the rate at which Planck-scale spatial uncertainties (and the phase shifts they produce) may accumulate over large path-lengths. Here α is defined by the expression for the path-length fluctuations, δl, of a source at distance l, where δl≈l1-α lP, with lP being the Planck length. We reassess previous proposals to use astronomical observations of distant quasars and AGN to test models of spacetime foam. We show explicitly how wavefront distortions on small scales cause the image intensity to decay to the point where distant objects become undetectable when the path-length fluctuations become comparable to the wavelength of the radiation. Chandra X-ray observations set a constraint α> 0.58, which rules out the random walk model (with α=1/2). Much firmer constraints can be set with Fermi detections of quasars at GeV energies, and at TeV energies with ground-based Cherenkov telescopes: α>0.67 and α>0.72, respectively. These limits seem to rule out α=2/3, the model of some physical interest.

  12. Constraints on the Source for Gamma-ray bursts from Observed X-Ray Afterglows

    NASA Astrophysics Data System (ADS)

    Mathews, Grant; Ruffini, Remo

    2015-04-01

    X-ray afterglows from long-duration gamma ray bursts (GRBs) are associated with energetic type Ic supernovae and the late time behavior of the afterglow from all GRBs follows the same universal normalization and power-law behavior at late times (~104 - 107 sec) when plotted relative to the time of the initial GRB trigger. We describe constraints from this afterglow on the engine for GRBs in the context of simple model for X-ray emission from accelerated relativistic electrons within an outgoing relativistic shock. We show that this universal scaling imposes 3 constraints: 1) The shock breakout energy is the same (~1051 ergs) for all bursts independently of the observed GRB luminosity; 2) After breakout, the shock propagates through an optically thin low-density (~ 1 - 10 g cm-3 medium; 3) The energy radiated by the shock is a small fraction of the total shock energy. These suggest that the late-time power-law afterglow emission derives from the underlying energetic supernova with a similar total shock energy. The correlation of the of the observed GRB energy with the luminosity of the plateau suggests a GRB engine occurring at different radii within the expanding SN consistent with the induced gravitational collapse paradigm. Work at the University of Notre Dame (GJM) supported by the U.S. Department of Energy under Nuclear Theory Grant DE-FG02-95-ER40934.

  13. HEATING OF THE MAGNETIC CHROMOSPHERE: OBSERVATIONAL CONSTRAINTS FROM Ca II {lambda}8542 SPECTRA

    SciTech Connect

    De la Cruz Rodriguez, J.; De Pontieu, B.; Carlsson, M.; Rouppe van der Voort, L. H. M.

    2013-02-10

    The heating of the Sun's chromosphere remains poorly understood. While progress has been made on understanding what drives the quiet-Sun internetwork chromosphere, chromospheric heating in strong magnetic field regions continues to present a difficult challenge, mostly because of a lack of observational constraints. We use high-resolution spectropolarimetric data from the Swedish 1 m Solar Telescope to identify the location and spatio-temporal properties of heating in the magnetic chromosphere. In particular, we report the existence of raised-core spectral line profiles in the Ca II {lambda}8542 line. These profiles are characterized by the absence of an absorption line core, showing a quasi-flat profile between {lambda} Almost-Equal-To {+-}0.5 A, and are abundant close to magnetic bright points and plage. Comparison with three-dimensional MHD simulations indicates that such profiles occur when the line of sight goes through an ''elevated temperature canopy'' associated with the expansion with height of the magnetic field of flux concentrations. This temperature canopy in the simulations is caused by ohmic dissipation where there are strong magnetic field gradients. The raised-core profiles are thus indicators of locations of increased chromospheric heating. We characterize the location and temporal and spatial properties of such profiles in our observations, thus providing much stricter constraints on theoretical models of chromospheric heating mechanisms than before.

  14. Constraints on the temperature of the intergalactic medium at z = 8.4 with 21-cm observations

    NASA Astrophysics Data System (ADS)

    Greig, Bradley; Mesinger, Andrei; Pober, Jonathan C.

    2016-02-01

    We compute robust lower limits on the spin temperature, TS, of the z = 8.4 intergalactic medium (IGM), implied by the upper limits on the 21-cm power spectrum recently measured by PAPER-64. Unlike previous studies which used a single epoch of reionization (EoR) model, our approach samples a large parameter space of EoR models: the dominant uncertainty when estimating constraints on TS. Allowing TS to be a free parameter and marginalizing over EoR parameters in our Markov Chain Monte Carlo code 21CMMC, we infer TS ≥ 3 K (corresponding approximately to 1σ) for a mean IGM neutral fraction of bar{x}_{HI}≳ 0.1. We further improve on these limits by folding-in additional EoR constraints based on: (i) the dark fraction in QSO spectra, which implies a strict upper limit of bar{x}_{HI}[z=5.9]≤ 0.06+0.05 (1σ ); and (ii) the electron scattering optical depth, τe = 0.066 ± 0.016 (1σ) measured by the Planck satellite. By restricting the allowed EoR models, these additional observations tighten the approximate 1σ lower limits on the spin temperature to TS ≥ 6 K. Thus, even such preliminary 21-cm observations begin to rule out extreme scenarios such as `cold reionization', implying at least some prior heating of the IGM. The analysis framework developed here can be applied to upcoming 21-cm observations, thereby providing unique insights into the sources which heated and subsequently reionized the very early Universe.

  15. Constraints on axions and axionlike particles from Fermi Large Area Telescope observations of neutron stars

    NASA Astrophysics Data System (ADS)

    Berenji, B.; Gaskins, J.; Meyer, M.

    2016-02-01

    We present constraints on the nature of axions and axionlike particles (ALPs) by analyzing gamma-ray data from neutron stars using the Fermi Large Area Telescope. In addition to axions solving the strong C P problem of particle physics, axions and ALPs are also possible dark matter candidates. We investigate axions and ALPs produced by nucleon-nucleon bremsstrahlung within neutron stars. We derive a phenomenological model for the gamma-ray spectrum arising from subsequent axion decays. By analyzing five years of gamma-ray data (between 60 and 200 MeV) for a sample of four nearby neutron stars, we do not find evidence for an axion or ALP signal; thus we obtain a combined 95% confidence level upper limit on the axion mass of 7.9 ×10-2 eV , which corresponds to a lower limit for the Peccei-Quinn scale fa of 7.6 ×107 GeV . Our constraints are more stringent than previous results probing the same physical process, and are competitive with results probing axions and ALPs by different mechanisms.

  16. New Constraints on Dark Energy from the ObservedGrowth of the Most X-ray Luminous Galaxy Clusters

    SciTech Connect

    Mantz, A.; Allen, S.W.; Ebeling, H.; Rapetti, D.

    2007-10-15

    We present constraints on the mean matter density, {Omega}{sub m}, normalization of the density fluctuation power spectrum, {sigma}{sub 8}, and dark energy equation of state parameter, w, obtained from the X-ray luminosity function of the Massive Cluster Survey (MACS) in combination with the local BCS and REFLEX galaxy cluster samples. Our analysis incorporates the mass function predictions of Jenkins et al. (2001), a mass-luminosity relation calibrated using the data of Reiprich and Bohringer (2002), and standard priors on the Hubble constant, H{sub 0}, and mean baryon density, {Omega}{sub b} h{sup 2}. We find {Omega}{sub m}=0.27 {sup +0.06} {sub -0.05} and {sigma}{sub 8}=0.77 {sup +0.07} {sub -0.06} for a spatially flat, cosmological constant model, and {Omega}{sub m}=0.28 {sup +0.08} {sub -0.06}, {sigma}{sub 8}=0.75 {+-} 0.08 and w=-0.97 {sup +0.20} {sub -0.19} for a flat, constant-w model. Our findings constitute the first precise determination of the dark energy equation of state from measurements of the growth of cosmic structure in galaxy clusters. The consistency of our result with w=-1 lends strong additional support to the cosmological constant model. The constraints are insensitive to uncertainties at the 10-20 percent level in the mass function and in the redshift evolution o the mass-luminosity relation; the constraint on dark energy is additionally robust against our choice of priors and known X-ray observational biases affecting the mass-luminosity relation. Our results compare favorably with those from recent analyses of type Ia supernovae, cosmic microwave background anisotropies, the X-ray gas mass fraction of relaxed galaxy clusters and cosmic shear. A simplified combination of the luminosity function data with supernova, cosmic microwave background and cluster gas fraction data using importance sampling yields the improved constraints {Omega}{sub m}=0.263 {+-} 0.014, {sigma}{sub 8}=0.79 {+-} 0.02 and w=-1.00 +- 0.05.

  17. Constraint on the early Universe by relic gravitational waves: From pulsar timing observations

    SciTech Connect

    Zhao Wen

    2011-05-15

    Recent pulsar timing observations by the Parkers Pulsar Timing Array (PPTA) and European Pulsar Timing Array (EPTA) teams obtained the constraint on the relic gravitational waves at the frequency f{sub *}=1/yr, which provides the opportunity to constrain H{sub *}, the Hubble parameter, when these waves crossed the horizon during inflation. In this paper, we investigate this constraint by considering the general scenario for the early Universe: we assume that the effective (average) equation-of-state w before the big bang nucleosynthesis stage is a free parameter. In the standard hot big-bang scenario with w=1/3, we find that the current PPTA result follows a bound H{sub *{<=}}1.15x10{sup -1}m{sub Pl}, and the EPTA result follows H{sub *{<=}}6.92x10{sup -2}m{sub Pl}. We also find that these bounds become much tighter in the nonstandard scenarios with w>1/3. When w=1, the bounds become H{sub *{<=}}5.89x10{sup -3}m{sub Pl} for the current PPTA and H{sub *{<=}}3.39x10{sup -3}m{sub Pl} for the current EPTA. In contrast, in the nonstandard scenario with w=0, the bound becomes H{sub *{<=}}7.76m{sub Pl} for the current PPTA.

  18. Moving object detection using motion field constraint with observer motion parameter

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroki; Ebine, Takumi; Hamada, Nozomu

    1999-10-01

    In this paper we propose a method for detecting moving objects in image sequence observed from a moving platform using optical flow. This problem is difficult because moving observer (i.e. camera) causes apparent motion in the image even for stationary environment. The method can be applied to many situations, such as a robot vision and an obstacle detection for an autonomous vehicle system. We assume that observer motion parameter (translation and rotation) is known and image system is modeled by perspective projection. For the problem, some methods have been proposed, in which the complex logarithm mapping, the estimation of Focus of Expansion and the depth of objects are used. For a given motion parameter of camera, we can formulate motion field constraint (MFC) in the image plane which is satisfied by the relative movement of stationary environment against camera motion. On the other hand, the motion vector in the image plane, which is called motion field, is estimated by the well-known optical flow constraint (OFC). Our main idea is to use the difference between two estimation results. One is the solution of minimizing least squared OFC subjected with MFC, and the other is the solution of that without MFC. For the stationary environment region, the difference between two is small and the difference tends to be large at the moving region. Therefore, the suitable criterion for these values will separate two regions precisely. In our study, two criteria are proposed and are investigated. One criterion uses squared residual of OFC with and without MFC. Another criterion uses directional error between two solutions. The validity of our method is shown through some examples, and the obtained results show the latter criterion gives more accurate estimation than the former one.

  19. Observational Constraints on the Nature of the First Supermassive Black Holes Seeds in the Early Universe

    NASA Astrophysics Data System (ADS)

    Treister, Ezequiel; Schawinski, Kevin; Natarajan, Priyamvada; Weigel, Anna

    2015-08-01

    We constrain the total accreted mass density in supermassive black holes at z>6, as inferred from the integrated X-ray emission in a sample of galaxy candidates selected using observed-frame optical and near-IR dropout techniques. Combining galaxy samples acquired in the Hubble Ultra Deep Field with recent deep Hubble observations of the CANDELS fields and Chandra 4 Msec observations we obtain the most restrictive current constraints on total black hole growth in the early Universe, estimating a mass density <1000M⊙Mpc-3. We further carry out a detailed study of all the individually-detected X-ray sources in the Chandra Deep Field South, finding that none of them is a good candidate to be at z>5.These results place interesting constraints on growth by accretion and imply one or more of the following: only ~20% luminous galaxies at this epoch are seeded with BHs - so seeding is inefficient; most black hole growth at early epochs happens in dusty - as yet undetected - host galaxies and/or in less-massive - also as yet undetected - galaxies; therefore a large fraction of the early black hole buildup is heavily obscured or that either most of the growth is due to radiatively inefficient accretion or due to black hole mergers at these early times. Not seeing a signal from growing black holes in high-redshift galaxies suggests that if their black holes are growing they are doing so in a veiled fashion, or they are simply not growing or perhaps most galaxies do not harbor black holes at their centers at all. These possibilities offer novel insights for high redshift seed formation models.Finally, we present the prospects to constrain the nature of the first black hole seeds in the early Universe using existing and planned space-based facilities.

  20. Initiation of deformation of the Eastern California Shear Zone: Constraints from Garlock fault geometry and GPS observations

    USGS Publications Warehouse

    Gan, Weijun; Zhang, P.; Shen, Z.-K.; Prescott, W.H.; Svarc, J.L.

    2003-01-01

    We suggest a 2-stage deformation model for the Eastern California Shear Zone (ECSZ) to explain the geometry of the Garlock fault trace. We assume the Garlock fault was originally straight and then was gradually curved by right-lateral shear deformation across the ECSZ. In our 2-stage deformation model, the first stage involves uniform shear deformation across the eastern part of the shear zone, and the second stage involves uniform shear deformation across the entire shear zone. In addition to the current shape of the Garlock fault, our model incorporates constraints on contemporary deformation rates provided by GPS observations. We find that the best fitting age for initiation of shear in eastern part of the ECSZ is about 5.0 ?? 0.4 Ma, and that deformation of the western part started about 1.6 Myr later.

  1. Seismic Properties of Partially Molten Rocks: Constraints from Experiments and Observations on Natural Rocks

    NASA Astrophysics Data System (ADS)

    Faul, U.; Jackson, I.; Garapic, G.

    2014-12-01

    The increasing resolution of seismic tomography studies as well as techniques that are sensitive to sharp, localized velocity changes indicate that melt is present in diverse tectonic settings in the upper mantle. Unresolved questions are the quantification of seismic velocities and attenuation to melt fraction, and the dynamic stability of this melt. Properties of partially molten rocks are generally sensitive to melt geometry. The melt geometry can be observed in experiments, but the experimental observations have to be extrapolated to mantle grain sizes. High resolution images of experimentally observed melt geometries (Garapic et al., 2013) indicate that the broad attenuation peak observed by forced torsional oscillation experiments (Jackson et al., 2004, Faul et al., 2004) are due to melt 'squirt'. Characterization of the inferred melt geometry in rocks recovered from mid-ocean ridges and peridotite massifs suggest that the experimental observations are applicable to the upper mantle. The data from the earlier seismic property experiments will be reprocessed with improved apparatus calibration and fitting strategies to provide a 'global' fit to the melt-bearing data as a function of grain size and melt fraction. This should allow quantification of the amount of melt imaged in seismic studies and therefore enable more accurate geodynamical models for example of arcs and backarcs, for which the highest resolution tomographic images exist. It should also provide more quantitative constraints on the amount of melt required to generate receiver functions and SS-bounces that suggest the presence of melt in the asthenosphere.

  2. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  3. Thrust-breakthrough of asymmetric anticlines: Observational constraints from surveys in the Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Jadamec, Margarete A.; Wallace, Wesley K.

    2014-05-01

    To gain insights into the processes governing the thrust-truncation of anticlines, we conducted a field study of the thrust-truncated folds in the remote Brooks Range of northern Alaska, where there is a transition in fold style from symmetric detachment folds to thrust-truncated asymmetric folds. In order to document the detailed geometry of the km-scale folds exposed in cliff-forming, largely inaccessible outcrops, a new surveying technique was developed that combines data from a theodolite and laser range finder. The field observations, survey profiles, and cross section reconstructions, indicate that late-stage thrust breakthrough of the anticlines within the mechanically competent Lisburne Group carbonates accommodated continued shortening when other mechanisms became unfeasible, including fold tightening, forelimb rotation, and parasitic folding in the anticline forelimbs. These results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold-and-thrust belts worldwide.

  4. Cosmology with hybrid expansion law: scalar field reconstruction of cosmic history and observational constraints

    SciTech Connect

    Akarsu, Özgür; Kumar, Suresh; Myrzakulov, R.; Sami, M.; Xu, Lixin E-mail: sukuyd@gmail.com E-mail: samijamia@gmail.com

    2014-01-01

    In this paper, we consider a simple form of expansion history of Universe referred to as the hybrid expansion law - a product of power-law and exponential type of functions. The ansatz by construction mimics the power-law and de Sitter cosmologies as special cases but also provides an elegant description of the transition from deceleration to cosmic acceleration. We point out the Brans-Dicke realization of the cosmic history under consideration. We construct potentials for quintessence, phantom and tachyon fields, which can give rise to the hybrid expansion law in general relativity. We investigate observational constraints on the model with hybrid expansion law applied to late time acceleration as well as to early Universe a la nucleosynthesis.

  5. New observational constraints on f(T) gravity from cosmic chronometers

    NASA Astrophysics Data System (ADS)

    Nunes, Rafael C.; Pan, Supriya; Saridakis, Emmanuel N.

    2016-08-01

    We use the local value of the Hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as Supernovae Type Ia and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f(T) gravity models, where T is the torsion scalar in teleparallel gravity. In particular, we consider three f(T) models with two parameters, out of which one is independent, and we quantify their deviation from ΛCDM cosmology through a sole parameter. Our analysis reveals that for one of the models a small but non-zero deviation from ΛCDM cosmology is slightly favored, while for the other models the best fit is very close to ΛCDM scenario. Clearly, f(T) gravity is consistent with observations, and it can serve as a candidate for modified gravity.

  6. A SEARCH FOR ADDITIONAL PLANETS IN THE NASA EPOXI OBSERVATIONS OF THE EXOPLANET SYSTEM GJ 436

    SciTech Connect

    Ballard, Sarah; Christiansen, Jessie L.; Charbonneau, David; Holman, Matthew J.; Fabrycky, Daniel; Deming, Drake; Barry, Richard K.; Kuchner, Marc J.; Livengood, Timothy A.; Hewagama, Tilak; A'Hearn, Michael F.; Wellnitz, Dennis D.; Sunshine, Jessica M.; Hampton, Don L.; Lisse, Carey M.; Seager, Sara; Veverka, Joseph F.

    2010-06-20

    We present time series photometry of the M dwarf transiting exoplanet system GJ 436 obtained with the Extrasolar Planet Observation and Characterization (EPOCh) component of the NASA EPOXI mission. We conduct a search of the high-precision time series for additional planets around GJ 436, which could be revealed either directly through their photometric transits or indirectly through the variations these second planets induce on the transits of the previously known planet. In the case of GJ 436, the presence of a second planet is perhaps indicated by the residual orbital eccentricity of the known hot Neptune companion. We find no candidate transits with significance higher than our detection limit. From Monte Carlo tests of the time series, we rule out transiting planets larger than 1.5 R{sub +} interior to GJ 436b with 95% confidence and larger than 1.25 R{sub +} with 80% confidence. Assuming coplanarity of additional planets with the orbit of GJ 436b, we cannot expect that putative planets with orbital periods longer than about 3.4 days will transit. However, if such a planet were to transit, we would rule out planets larger than 2.0 R{sub +} with orbital periods less than 8.5 days with 95% confidence. We also place dynamical constraints on additional bodies in the GJ 436 system, independent of radial velocity measurements. Our analysis should serve as a useful guide for similar analyses of transiting exoplanets for which radial velocity measurements are not available, such as those discovered by the Kepler mission. From the lack of observed secular perturbations, we set upper limits on the mass of a second planet as small as 10 M{sub +} in coplanar orbits and 1 M{sub +} in non-coplanar orbits close to GJ 436b. We present refined estimates of the system parameters for GJ 436. We find P = 2.64389579 {+-} 0.00000080 d, R{sub *} = 0.437 {+-} 0.016 R{sub sun}, and R{sub p} = 3.880 {+-} 0.147 R{sub +}. We also report a sinusoidal modulation in the GJ 436 light curve

  7. The depths of clouds on Jupiter: Observational constraints on the O/H ratio

    NASA Astrophysics Data System (ADS)

    Wong, Michael H.; Bjoraker, Gordon L.; de Pater, Imke; Ádámkovics, Máté

    2015-11-01

    The oxygen abundance in Jupiter is an important constraint on planet formation and conditions in protoplanetary disks. Oxygen, in the form of water, is also dynamically significant in Jupiter's atmosphere: as a tracer of circulation and as a carrier of latent heat.We have developed a technique to spectroscopically measure the depth of opaque cloud tops in Jupiter's atmosphere (Bjoraker et al. 2015, ApJ in press, arXiv:1508.04795). We measure resolved CH3D line shapes in the 5-micron window of Jupiter's spectrum to distinguish between cloud-top pressure levels of about 3 to 10 bars.We will use the retrieved cloud top pressure levels to place lower limits on the deep O/H ratio in Jupiter, based on Keck/NIRSPEC spectra acquired in January 2013. Since our spectra do not directly give the temperature/pressure profile in the cloud layer, constraining the O/H ratio requires independent atmospheric structure data. We will review observational and theoretical constraints on Jupiter's thermal structure, which lead to uncertainty bounds on the O/H ratio we derive. Preliminary work to date suggests that our technique may be able to determine whether or not the Galileo Probe Mass Spectrometer O/H measurement can be representative of the planet's bulk abundance, and whether O is supersolar in Jupiter like the other volatile elements C, N, and S. If we can distinguish between O/H lower limits of 10x and 3x solar, we will be able to test the hypothesis that Jupiter's volatiles must have been delivered via water ice clathrates.[This conference abstract is supported by NASA grant NNX11AM55G issued through the Outer Planets Research Program, and by grants NNX14AJ43G and NNX15AJ41G through the Planetary Astronomy and Solar System Observations Programs.

  8. Observational constraints to Ricci dark energy model by using: SN, BAO, OHD, fgas data sets

    SciTech Connect

    Xu, Lixin; Wang, Yuting E-mail: wangyuting0719@163.com

    2010-06-01

    We perform a global constraint on the Ricci dark energy model with both the flat case and the non-flat case, using the Markov Chain Monte Carlo (MCMC) method and the combined observational data from the cluster X-ray gas mass fraction, Supernovae of type Ia (397), baryon acoustic oscillations, current Cosmic Microwave Background, and the observational Hubble function. In the flat model, we obtain the best fit values of the parameters in 1σ,2σ regions: Ω{sub m0} = 0.2927{sup +0.0420+0.0542}{sub −0.0323−0.0388}, α = 0.3823{sup +0.0331+0.0415}{sub −0.0418−0.0541}, Age/Gyr = 13.48{sup +0.13+0.17}{sub −0.16−0.21}, H{sub 0} = 69.09{sup +2.56+3.09}{sub −2.37−3.39}. In the non-flat model, the best fit parameters are found in 1σ,2σ regions:Ω{sub m0} = 0.3003{sup +0.0367+0.0429}{sub −0.0371−0.0423}, α = 0.3845{sup +0.0386+0.0521}{sub −0.0474−0.0523}, Ω{sub k} = 0.0240{sup +0.0109+0.0133}{sub −0.0130−0.0153}, Age/Gyr = 12.54{sup +0.51+0.65}{sub −0.37−0.49}, H{sub 0} = 72.89{sup +3.31+3.88}{sub −3.05−3.72}. Compared to the constraint results in the ΛCDM model by using the same datasets, it is shown that the current combined datasets prefer the ΛCDM model to the Ricci dark energy model.

  9. Chemical cycling and deposition of atmospheric mercury: Global constraints from observations

    NASA Astrophysics Data System (ADS)

    Selin, Noelle E.; Jacob, Daniel J.; Park, Rokjin J.; Yantosca, Robert M.; Strode, Sarah; Jaeglé, Lyatt; Jaffe, Daniel

    2007-01-01

    We use a global 3-D model of atmospheric mercury (GEOS-Chem) to interpret worldwide observations of total gaseous mercury (TGM) and reactive gaseous mercury (RGM) in terms of the constraints they provide on the chemical cycling and deposition of mercury. Our simulation including a global mercury source of 7000 Mg yr-1 and a TGM lifetime of 0.8 years reproduces the magnitude and large-scale variability of TGM observations at land sites. However, it cannot capture observations of high TGM from ship cruises, implying a problem either in the measurements or in our fundamental understanding of mercury sources. Observed TGM seasonal variation at northern midlatitudes is consistent with a photochemical oxidation for Hg(0) partly balanced by photochemical reduction of Hg(II). Observations of increasing RGM with altitude imply a long lifetime of Hg(II) in the free troposphere. We find in the model that Hg(II) dominates over Hg(0) in the upper troposphere and stratosphere and that subsidence is the principal source of Hg(II) at remote surface sites. RGM observations at Okinawa Island (Japan) show large diurnal variability implying fast deposition, which we propose is due to RGM uptake by sea-salt aerosols. Observed mercury wet deposition fluxes in the United States show a maximum in the southeast, which we attribute to photochemical oxidation of the global Hg(0) pool. They also show a secondary maximum in the industrial Midwest due to regional emissions that is underestimated in the model, possibly because of excessive dry deposition relative to wet (dry deposition accounts for 68% of total mercury deposition in the United States in the model, but this is sensitive to the assumed phase of Hg(II)). We estimate that North American anthropogenic emissions contribute on average 20% to U.S. mercury deposition.

  10. Constraints to the Cold Classical KBO population from HST observations of faint objects

    NASA Astrophysics Data System (ADS)

    Penteado, Paulo F.; Trilling, David; Grundy, William

    2015-11-01

    The size distribution of the known Kuiper Belt Objects has been described by a double power law, with a break at R magnitude 25. There are two leading interpretations to this break: 1) It is the result of the collisional evolution among these KBOs, with the objects smaller than the break being the population most affected by collisional erosion. 2) The size distribution break is primordial, set during the Kuiper Belt formation.The low inclination Kuiper Belt Objects, the Cold Classical population, is thought to have been dynamically isolated since the formation of the Solar System, and thus only collisions between Cold Classicals would have affected their size distribution. If the size distribution is collisional, it probes parameters of the Kuiper Belt history: strengths of the bodies, impact energies and frequency, and the the number of objects. If the distribution is primordial, it reveals parameters of the Kuiper Belt accretion, as well as limits on its subsequent collisional history.In this work, we obtained new HST observations of 5 faint Cold Classicals, which we combine with previous HST observations, to examine the distribution of two properties of the smallest KBOs: colors and binary fraction. These two properties can differentiate between a primordial and a collisional origin of the size distribution break. If the smaller bodies have been through extensive collisional evolution, they will have exposed materials from their interiors, which has not been exposed to weathering, and thus should be bluer than the old surfaces of the larger bodies. An independent constraint can be derived from the fraction of binary objects: the angular momentum of the observed binaries is typically too high to result from collisions, thus a collisionally-evolved population would have a lower binary fraction, due to the easier separation of binaries, compared to the disruption of similar-sized bodies, and the easier disruption of the binary components, due to the smaller size

  11. Observational constraints on the progenitor metallicities of core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Anderson, J. P.; Covarrubias, R. A.; James, P. A.; Hamuy, M.; Habergham, S. M.

    2010-10-01

    We present constraints on the progenitor metallicities of core-collapse supernovae. To date, nearly all metallicity constraints have been inferred from indirect methods such as metallicity gradients in host galaxies, luminosities of host galaxies or derived global galaxy metallicities. Here, progenitor metallicities are derived from optical spectra taken at the sites of nearby supernovae, from the ratio of strong emission lines found in their host HII regions. We present results from the spectra of 74 host HII regions and discuss the implications that these have on the nature of core-collapse supernova progenitors. Overall, while we find that the mean metallicity of Type Ibc environments is higher than that of Type II events, this difference is smaller than observed in previous studies. There is only a 0.06 dex difference in the mean metallicity values, at a statistical significance of ~1.5σ, while using a Kolmogorov-Smirnov test we find that the two metallicity distributions are marginally consistent with being drawn from the same parent population (probability >10 per cent). This argues that progenitor metallicity is not a dominant parameter in deciding supernovae type, with progenitor mass and/or binarity playing a much more significant role. The mean derived oxygen metallicities [12+log(O/H)] for the different supernova types, on the Pettini & Pagel scale, are 8.580 (standard error on the mean of 0.027) for the 46 Type II supernovae (dominated by Type II plateau), 8.616 (0.040) for 10 Type Ib and 8.626 (0.039) for 14 Type Ic. Overall, the Type Ibc supernovae have a mean metallicity of 8.635 (0.026, 27 supernovae). Hence, we find a slight suggestion of a metallicity sequence, in terms of increasing progenitor metallicity going from Type II through Ib and finally Ic supernovae arising from the highest metallicity progenitors. Finally we discuss these results in the context of all current literature progenitor metallicity measurements, and discuss biases and

  12. Dwarf Novae in the Galactic Bulge Survey - Observational Constraints on X-ray/Recurrence Time Relations and Space Density

    NASA Astrophysics Data System (ADS)

    Britt, Christopher; Maccarone, T. J.; Hynes, R. I.; Jonker, P.; Torres, M.; Galactic Bulge Survey Collaboration

    2014-01-01

    The Galactic Bulge Survey is a shallow, wide-field X-ray survey of the Galactic Bulge made with the Chandra X-ray Observatory, covering 12 square degrees above and below the Galactic Plane, centered at |b|=1.5°. In 8 days of optical observations, made with the Mosaic-II instrument on the Blanco 4m telescope at CTIO with the purpose of identifying variable optical counterparts to the 1216 unique X-ray sources in the GBS, 8 dwarf novae (DN) outbursts were identified. 4 of the X-ray detected systems undergoing DN outbursts are within the 100 brightest X-ray sources. It is thought that X-ray flux in DN systems traces mass accretion, which is correlated with recurrence rate. With these observations, we can place observational constraints on the relationship between X-ray flux and recurrence rates. In addition, there are DN outbursts in our data set for which no X-ray detection was made. We can use our observations to independently estimate the space density of systems undergoing DN outbursts in the Milky Way.

  13. LV wall segmentation using the variational level set method (LSM) with additional shape constraint for oedema quantification

    NASA Astrophysics Data System (ADS)

    Kadir, K.; Gao, H.; Payne, A.; Soraghan, J.; Berry, C.

    2012-10-01

    In this paper an automatic algorithm for the left ventricle (LV) wall segmentation and oedema quantification from T2-weighted cardiac magnetic resonance (CMR) images is presented. The extent of myocardial oedema delineates the ischaemic area-at-risk (AAR) after myocardial infarction (MI). Since AAR can be used to estimate the amount of salvageable myocardial post-MI, oedema imaging has potential clinical utility in the management of acute MI patients. This paper presents a new scheme based on the variational level set method (LSM) with additional shape constraint for the segmentation of T2-weighted CMR image. In our approach, shape information of the myocardial wall is utilized to introduce a shape feature of the myocardial wall into the variational level set formulation. The performance of the method is tested using real CMR images (12 patients) and the results of the automatic system are compared to manual segmentation. The mean perpendicular distances between the automatic and manual LV wall boundaries are in the range of 1-2 mm. Bland-Altman analysis on LV wall area indicates there is no consistent bias as a function of LV wall area, with a mean bias of -121 mm2 between individual investigator one (IV1) and LSM, and -122 mm2 between individual investigator two (IV2) and LSM when compared to two investigators. Furthermore, the oedema quantification demonstrates good correlation when compared to an expert with an average error of 9.3% for 69 slices of short axis CMR image from 12 patients.

  14. CONSTRAINTS ON TYPE Ia SUPERNOVA PROGENITOR COMPANIONS FROM EARLY ULTRAVIOLET OBSERVATIONS WITH SWIFT

    SciTech Connect

    Brown, Peter J.; Dawson, Kyle S.; Harris, David W.; Olmstead, Matthew; Milne, Peter; Roming, Peter W. A.

    2012-04-10

    We compare early ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) with theoretical predictions for the brightness of the shock associated with the collision between SN ejecta and a companion star. Our simple method is independent of the intrinsic flux from the SN and treats the flux observed with the Swift/Ultra-Violet Optical Telescope as conservative upper limits on the shock brightness. Comparing this limit with the predicted flux for various shock models, we constrain the geometry of the SN progenitor-companion system. We find the model of a 1 M{sub Sun} red supergiant companion in Roche-lobe overflow to be excluded at a 95% confidence level for most individual SNe for all but the most unfavorable viewing angles. For the sample of 12 SNe taken together, the upper limits on the viewing angle are inconsistent with the expected distribution of viewing angles for red gaint stars as the majority of companions with high confidence. The separation distance constraints do allow main-sequence companions. A better understanding of the UV flux arising from the SN itself as well as continued UV observations of young SNe Ia will further constrain the possible progenitors of SNe Ia.

  15. Constraints of solar flare particle transport models from anisotropy observations at Voyager 1

    NASA Technical Reports Server (NTRS)

    Hamilton, D. C.; Mason, G. M.; Gloeckler, G.

    1985-01-01

    In general a particle transport model for energetic solar flare particles contains a number of free parameters which are determined by fitting various features of observed particle events. Frequently the parameter values are not uniquely determined. In order to place tighter constraints on the models, the anisotropy of 1 and 25 MeV/nuc protons and helium nuclei were examined during the 22 November 1977 solar particle event using data from the LECP experiment on Voyager 1 at 1.6 AU. These observations were combined with the time intensity profiles at Voyager 1 and at 1 AU from ISEE-1 and IMP-8 to determine the magnitude and radial dependence of the interplanetary diffusion coefficient and the required injection duration at the sun. The first order anisotropy amplitudes for both 1 MeV and 25 MeV protons are observed to decrease from maximum values (approx. 1) during the event onset at Voyager 1 to values consistent with convection in the solar wind at about 3 days into the event decay phase. The intensity and anisotropy profiles at 1.6 AU are consistent with predictions of diffusive transport with a modest mean free path (lambda = approx. 0.1 AU).

  16. Supersymmetry vis-à-vis Observation: Dark Matter Constraints, Global Fits and Statistical Issues

    NASA Astrophysics Data System (ADS)

    Akrami, Yashar

    2011-11-01

    Weak-scale supersymmetry is one of the most favoured theories beyond the Standard Model of particle physics that elegantly solves various theoretical and observational problems in both particle physics and cosmology. In this thesis, I describe the theoretical foundations of supersymmetry, issues that it can address and concrete supersymmetric models that are widely used in phenomenological studies. I discuss how the predictions of supersymmetric models may be compared with observational data from both colliders and cosmology. I show why constraints on supersymmetric parameters by direct and indirect searches of particle dark matter are of particular interest in this respect. Gamma-ray observations of astrophysical sources, in particular dwarf spheroidal galaxies, by the Fermi satellite, and recording nuclear recoil events and energies by future ton-scale direct detection experiments are shown to provide powerful tools in searches for supersymmetric dark matter and estimating supersymmetric parameters. I discuss some major statistical issues in supersymmetric global fits to experimental data. In particular, I further demonstrate that existing advanced scanning techniques may fail in correctly mapping the statistical properties of the parameter spaces even for the simplest supersymmetric models. Complementary scanning methods based on Genetic Algorithms are proposed.

  17. Interaction Between Dark Energy and Dark Matter: Observational Constraints from Ohd, BAO, CMB and SNe Ia

    NASA Astrophysics Data System (ADS)

    Cao, Shuo; Liang, Nan

    2013-12-01

    In order to test if there is energy transfer between dark energy (DE) and dark matter (DM), we investigate cosmological constraints on two forms of nontrivial interaction between the DM sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term Q = 3γHρ, i.e. the parameter γ to be a small number, |γ| ≈ 10-2. However, concerning the sign of the interaction parameter, we observe that γ > 0 when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling (γ < 0) is preferred by observations when the interaction term is proportional to DE density. We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem. Results suggest that the γmIDE model with a positive coupling may alleviate the coincidence problem, since its coincidence index C is smaller than that for the γdIDE model, the interacting quintessence and phantom models by four orders of magnitude.

  18. Constraints on Eurasian ship NOx emissions using OMI NO2 observations and GEOS-Chem

    NASA Astrophysics Data System (ADS)

    Vinken, Geert C. M.; Boersma, Folkert; van Donkelaar, Aaron; Zhang, Lin

    2013-04-01

    Ships emit large quantities of nitrogen oxides (NOx = NO + NO2), important precursors for ozone (O3) and particulate matter formation. Ships burn low-grade marine heavy fuel due to the limited regulations that exist for the maritime sector in international waters. Previous studies showed that global ship NOx emission inventories amount to 3.0-10.4 Tg N per year (15-30% of total NOx emissions), with most emissions close to land and affecting air quality in densely populated coastal regions. Bottom-up inventories depend on the extrapolation of a relatively small number of measurements that are often unable to capture annual emission changes and can suffer from large uncertainties. Satellites provide long-term, high-resolution retrievals that can be used to improve emission estimates. In this study we provide top-down constraints on ship NOx emissions in major European ship routes, using observed NO2 columns from the Ozone Monitoring Instrument (OMI) and NO2 columns simulated with the nested (0.5°×0.67°) version of the GEOS-Chem chemistry transport model. We use a plume-in-grid treatment of ship NOx emissions to account for in-plume chemistry in our model. We ensure consistency between the retrievals and model simulations by using the high-resolution GEOS-Chem NO2 profiles as a priori. We find evidence that ship emissions in the Mediterranean Sea are geographically misplaced by up to 150 km and biased high by a factor of 4 as compared to the most recent (EMEP) ship emission inventory. Better agreement is found over the shipping lane between Spain and the English Channel. We extend our approach and also provide constraints for major ship routes in the Red Sea and Indian Ocean. Using the full benefit of the long-term retrieval record of OMI, we present a new Eurasian ship emission inventory for the years 2005 to 2010, based on the EMEP and AMVER-ICOADS inventories, and top-down constraints from the satellite retrievals. Our work shows that satellite retrievals can

  19. Observables sensitive to absolute neutrino masses: Constraints and correlations from world neutrino data

    SciTech Connect

    Fogli, G.L.; Lisi, E.; Marrone, A.; Palazzo, A.; Melchiorri, A.; Serra, P.; Silk, J.

    2004-12-01

    In the context of three-flavor neutrino mixing, we present a thorough study of the phenomenological constraints applicable to three observables sensitive to absolute neutrino masses: The effective neutrino mass in Tritium beta-decay (m{sub {beta}}); the effective Majorana neutrino mass in neutrinoless double beta-decay (m{sub {beta}}{sub {beta}}); and the sum of neutrino masses in cosmology ({sigma}). We discuss the correlations among these variables which arise from the combination of all the available neutrino oscillation data, in both normal and inverse neutrino mass hierarchy. We set upper limits on m{sub {beta}} by combining updated results from the Mainz and Troitsk experiments. We also consider the latest results on m{sub {beta}}{sub {beta}} from the Heidelberg-Moscow experiment, both with and without the lower bound claimed by such experiment. We derive upper limits on {sigma} from an updated combination of data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite and the two degrees Fields (2dF) Galaxy Redshifts Survey, with and without Lyman-{alpha} forest data from the Sloan Digital Sky Survey (SDSS), in models with a nonzero running of the spectral index of primordial inflationary perturbations. The results are discussed in terms of two-dimensional projections of the globally allowed region in the (m{sub {beta}},m{sub {beta}}{sub {beta}},{sigma}) parameter space, which neatly show the relative impact of each data set. In particular, the (in)compatibility between {sigma} and m{sub {beta}}{sub {beta}} constraints is highlighted for various combinations of data. We also briefly discuss how future neutrino data (both oscillatory and nonoscillatory) can further probe the currently allowed regions.

  20. Space-based Observational Constraints for 1-D Plume Rise Models

    NASA Technical Reports Server (NTRS)

    Martin, Maria Val; Kahn, Ralph A.; Logan, Jennifer A.; Paguam, Ronan; Wooster, Martin; Ichoku, Charles

    2012-01-01

    We use a space-based plume height climatology derived from observations made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the NASA Terra satellite to evaluate the ability of a plume-rise model currently embedded in several atmospheric chemical transport models (CTMs) to produce accurate smoke injection heights. We initialize the plume-rise model with assimilated meteorological fields from the NASA Goddard Earth Observing System and estimated fuel moisture content at the location and time of the MISR measurements. Fire properties that drive the plume-rise model are difficult to estimate and we test the model with four estimates for active fire area and four for total heat flux, obtained using empirical data and Moderate Resolution Imaging Spectroradiometer (MODIS) re radiative power (FRP) thermal anomalies available for each MISR plume. We show that the model is not able to reproduce the plume heights observed by MISR over the range of conditions studied (maximum r2 obtained in all configurations is 0.3). The model also fails to determine which plumes are in the free troposphere (according to MISR), key information needed for atmospheric models to simulate properly smoke dispersion. We conclude that embedding a plume-rise model using currently available re constraints in large-scale atmospheric studies remains a difficult proposition. However, we demonstrate the degree to which the fire dynamical heat flux (related to active fire area and sensible heat flux), and atmospheric stability structure influence plume rise, although other factors less well constrained (e.g., entrainment) may also be significant. Using atmospheric stability conditions, MODIS FRP, and MISR plume heights, we offer some constraints on the main physical factors that drive smoke plume rise. We find that smoke plumes reaching high altitudes are characterized by higher FRP and weaker atmospheric stability conditions than those at low altitude, which tend to remain confined

  1. Constraints on binary neutron star merger product from short GRB observations

    NASA Astrophysics Data System (ADS)

    Gao, He; Zhang, Bing; Lü, Hou-Jun

    2016-02-01

    Binary neutron star (NS) mergers are strong gravitational-wave (GW) sources and the leading candidates to interpret short-duration gamma-ray bursts (SGRBs). Under the assumptions that SGRBs are produced by double neutron star mergers and that the x-ray plateau followed by a steep decay as observed in SGRB x-ray light curves marks the collapse of a supramassive neutron star to a black hole (BH), we use the statistical observational properties of Swift SGRBs and the mass distribution of Galactic double neutron star systems to place constraints on the neutron star equation of state (EoS) and the properties of the post-merger product. We show that current observations already impose the following interesting constraints. (1) A neutron star EoS with a maximum mass close to a parametrization of Mmax=2.37 M⊙(1 +1.58 ×10-10P-2.84) is favored. (2) The fractions for the several outcomes of NS-NS mergers are as follows: ˜40 % prompt BHs, ˜30 % supramassive NSs that collapse to BHs in a range of delay time scales, and ˜30 % stable NSs that never collapse. (3) The initial spin of the newly born supramassive NSs should be near the breakup limit (Pi˜1 ms ), which is consistent with the merger scenario. (4) The surface magnetic field of the merger products is typically ˜1015 G . (5) The ellipticity of the supramassive NSs is ɛ ˜(0.004 -0.007 ), so that strong GW radiation is released after the merger. (6) Even though the initial spin energy of the merger product is similar, the final energy output of the merger product that goes into the electromagnetic channel varies in a wide range from several 1049 to several 1052 erg , since a good fraction of the spin energy is either released in the form of GWs or falls into the black hole as the supramassive NS collapses.

  2. Investigations into Generalization of Constraint-Based Scheduling Theories with Applications to Space Telescope Observation Scheduling

    NASA Astrophysics Data System (ADS)

    Muscettola, Nicola; Smith, Steven S.

    1996-09-01

    This final report summarizes research performed under NASA contract NCC 2-531 toward generalization of constraint-based scheduling theories and techniques for application to space telescope observation scheduling problems. Our work into theories and techniques for solution of this class of problems has led to the development of the Heuristic Scheduling Testbed System (HSTS), a software system for integrated planning and scheduling. Within HSTS, planning and scheduling are treated as two complementary aspects of the more general process of constructing a feasible set of behaviors of a target system. We have validated the HSTS approach by applying it to the generation of observation schedules for the Hubble Space Telescope. This report summarizes the HSTS framework and its application to the Hubble Space Telescope domain. First, the HSTS software architecture is described, indicating (1) how the structure and dynamics of a system is modeled in HSTS, (2) how schedules are represented at multiple levels of abstraction, and (3) the problem solving machinery that is provided. Next, the specific scheduler developed within this software architecture for detailed management of Hubble Space Telescope operations is presented. Finally, experimental performance results are given that confirm the utility and practicality of the approach.

  3. Inverse optimization of the land surface model JSBACH using multiple constraints and long term observations

    NASA Astrophysics Data System (ADS)

    Carvalhais, N.; Zaehle, S.; Schürmann, G. J.; Beer, C.; Granier, A.; Loustau, D.; Papale, D.; Reick, C.; Reichstein, M.

    2012-04-01

    Terrestrial ecosystems play a key role in the global carbon cycle. The characterization and understanding of ecosystem level responses to climatic drivers is essential for diagnostic purposes as well as improving the representation of land-atmosphere feedbacks in climate projections of coupled carbon-cycle climate models. The combination of biogeochemical models with multiple observations of ecosystem carbon and water fluxes through a model-data integration framework enables the recognition of potential limitations of modeling approaches. Here, we evaluate the performance of the land surface scheme (JSBACH 2.0) of the Max Planck Institute Earth System Model (MPI-ESM) to simulate ecosystem carbon and water fluxes for two forest sites monitored using the eddy covariance technique since 1996: a beech (Hesse) and a pine (Le Bray) forest. An inverse optimization approach was performed considering daily carbon and water fluxes, as well as observations of vegetation and soil carbon stocks. Our results show that multiple-constraints approaches including information about ecosystem states and ecosystem carbon and water fluxes provide a significant support in evaluating model structures as opposed to assimilation approaches only considering ecosystem flux measurements. Further, this work emphasizes the relevance of long time series to address the model performance of inter annual variability.

  4. Social constraints from an observer's perspective: Coordinated actions make an agent's position more predictable.

    PubMed

    Yin, Jun; Xu, Haokui; Ding, Xiaowei; Liang, Junying; Shui, Rende; Shen, Mowei

    2016-06-01

    Action prediction, a crucial ability to support social activities, is sensitive to the individual goals of expected actions. This article reports a novel finding that the predictions of observed actions for a temporarily invisible agent are influenced, and even enhanced, when this agent has a joint/collective goal to implement coordinated actions with others (i.e., with coordination information). Specifically, we manipulated the coordination information by presenting two chasers and one common target to perform coordinated or individual chases, and subjects were required to predict the expected action (i.e., position) for one chaser after it became momentarily invisible. To control for possible low-level physical properties, we also established some intense paired controls for each type of chase, such as backward replay (Experiment 1), making the chasing target invisible (Experiment 2) and a direct manipulation of the goal-directedness of one chaser's movements to disrupt coordination information (Experiment 3). The results show that the prediction error for invisible chasers depends on whether the second chaser is coordinated with the first, and this effect vanishes when the chasers behaves with exactly the same motions, but without coordination information between them; furthermore, this influence results in enhancing the performance of action prediction. These findings extend the influential factors of action prediction to the level of observed coordination information, implying that the functional characteristic of mutual constraints of coordinated actions can be utilized by vision. PMID:26922896

  5. The death of massive stars - II. Observational constraints on the progenitors of Type Ibc supernovae

    NASA Astrophysics Data System (ADS)

    Eldridge, John J.; Fraser, Morgan; Smartt, Stephen J.; Maund, Justyn R.; Crockett, R. Mark

    2013-11-01

    The progenitors of many Type II core-collapse supernovae (SNe) have now been identified directly on pre-discovery imaging. Here, we present an extensive search for the progenitors of Type Ibc SNe in all available pre-discovery imaging since 1998. There are 12 Type Ibc SNe with no detections of progenitors in either deep ground-based or Hubble Space Telescope archival imaging. The deepest absolute BVR magnitude limits are between -4 and - 5 mag. We compare these limits with the observed Wolf-Rayet population in the Large Magellanic Cloud and estimate a 16 per cent probability that we have failed to detect such a progenitor by chance. Alternatively, the progenitors evolve significantly before core-collapse or we have underestimated the extinction towards the progenitors. Reviewing the relative rates and ejecta mass estimates from light-curve modelling of Ibc SNe, we find both incompatible with Wolf-Rayet stars with initial masses >25 M⊙ being the only progenitors. We present binary evolution models that fit these observational constraints. Stars in binaries with initial masses ≲ 20 M⊙ lose their hydrogen envelopes in binary interactions to become low-mass helium stars. They retain a low-mass hydrogen envelope until ≈104 yr before core-collapse; hence, it is not surprising that Galactic analogues have been difficult to identify.

  6. Investigations into Generalization of Constraint-Based Scheduling Theories with Applications to Space Telescope Observation Scheduling

    NASA Technical Reports Server (NTRS)

    Muscettola, Nicola; Smith, Steven S.

    1996-01-01

    This final report summarizes research performed under NASA contract NCC 2-531 toward generalization of constraint-based scheduling theories and techniques for application to space telescope observation scheduling problems. Our work into theories and techniques for solution of this class of problems has led to the development of the Heuristic Scheduling Testbed System (HSTS), a software system for integrated planning and scheduling. Within HSTS, planning and scheduling are treated as two complementary aspects of the more general process of constructing a feasible set of behaviors of a target system. We have validated the HSTS approach by applying it to the generation of observation schedules for the Hubble Space Telescope. This report summarizes the HSTS framework and its application to the Hubble Space Telescope domain. First, the HSTS software architecture is described, indicating (1) how the structure and dynamics of a system is modeled in HSTS, (2) how schedules are represented at multiple levels of abstraction, and (3) the problem solving machinery that is provided. Next, the specific scheduler developed within this software architecture for detailed management of Hubble Space Telescope operations is presented. Finally, experimental performance results are given that confirm the utility and practicality of the approach.

  7. Observational constraints on upper tropospheric NOx emissions, lifetime, and oxidative products

    NASA Astrophysics Data System (ADS)

    Nault, Benjamin Albert

    the thermal decomposition of CH3O2NO2 during sampling. I show that CH3O2NO2 is ubiquitous in the upper troposphere and is as important NOx oxidative product as HNO3. Then, using observations from one quasi-Lagrangian flight during DC3, I derive constraints on the daytime NOx oxidative rate constants for the reactions that remove upper tropospheric NOx. The reactions include the production of CH3O2NO 2, HO2NO2, PAN, PPN, alkyl and multifunctional nitrates, and HNO3. These constraints indicate that NOx lifetime is longer than currently believe due to the daytime HNO3 and HO2NO2 production rate constants being 30 -- 50% slower than currently assumed. Finally, the implications of the longer lifetime are used to show that lightning NOx emission rates are at least 33% larger than current estimates. As a consequence, model predictions indicate O3 in the upper troposphere increase by 5 -- 10% with a resulting increase in radiative forcing.

  8. Theoretical and observational constraints of viable f (R ) theories of gravity

    NASA Astrophysics Data System (ADS)

    de la Cruz-Dombriz, Álvaro; Dunsby, Peter K. S.; Kandhai, Sulona; Sáez-Gómez, Diego

    2016-04-01

    Modified gravity has attracted much attention over the last few years and remains a potential candidate for dark energy. In particular, the so-called viable f (R ) gravity theories, which are able to both recover general relativity and produce late-time cosmic acceleration, have been widely studied in recent literature. Nevertheless, extended theories of gravity suffer from several shortcomings which compromise their ability to provide realistic alternatives to the standard cosmological Λ CDM Concordance model. We address the existence of cosmological singularities and the conditions that guarantee late-time acceleration, assuming reasonable energy conditions for standard matter in the so-called Hu-Sawicki f (R ) model, currently among the most widely studied modifications to general relativity. Then using the supernovae Ia Union 2.1 catalogue, we further constrain the free parameters of this model. The combined analysis of both theoretical and observational constraints sheds some light on the viable parameter space of these models and the form of the underlying effective theory of gravity.

  9. Constraints on CME Evolution from in situ Observations of Ionic Charge States

    NASA Technical Reports Server (NTRS)

    Gruesbeck, Jacob R.; Lepri, Susan T.; Zurbuchen, Thomas H.; Antiochos, Spiro K.

    2010-01-01

    We present a novel procedure for deriving the physical properties of Coronal Mass Ejections (CMES) in the corona. Our methodology uses in-situ measurements of ionic charge states of C, O, Si and Fe in the heliosphere and interprets them in the context of a model for the early evolution of ICME plasma, between 2 - 5 R-solar. We find that the data can be fit only by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnect ion jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time-history and, therefore, provide important constraints for the heating and expansion time-scales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.

  10. Constraints on dark matter particles from theory, galaxy observations, and N-body simulations

    NASA Astrophysics Data System (ADS)

    Boyanovsky, D.; de Vega, H. J.; Sanchez, N. G.

    2008-02-01

    Mass bounds on dark matter (DM) candidates are obtained for particles that decouple in or out of equilibrium while ultrarelativistic with arbitrary isotropic and homogeneous distribution functions. A coarse grained Liouville invariant primordial phase-space density D is introduced which depends solely on the distribution function at decoupling. The density D is explicitly computed and combined with recent photometric and kinematic data on dwarf spheroidal satellite galaxies in the Milky Way (dShps) and the observed DM density today yielding upper and lower bounds on the mass, primordial phase-space densities, and velocity dispersion of the DM candidates. Combining these constraints with recent results from N-body simulations yields estimates for the mass of the DM particles in the range of a few keV. We establish in this way a direct connection between the microphysics of decoupling in or out of equilibrium and the constraints that the particles must fulfill to be suitable DM candidates. If chemical freeze-out occurs before thermal decoupling, light bosonic particles can Bose condense. We study such Bose-Einstein condensate (BEC) as a dark matter candidate. It is shown that, depending on the relation between the critical (Tc) and decoupling (Td) temperatures, a BEC light relic could act as cold DM but the decoupling scale must be higher than the electroweak scale. The condensate hastens the onset of the nonrelativistic regime and tightens the upper bound on the particle’s mass. A nonequilibrium scenario which describes particle production and partial thermalization, sterile neutrinos produced out of equilibrium, and other DM models is analyzed in detail and the respective bounds on mass, primordial phase-space density, and velocity dispersion are obtained. Thermal relics with m˜fewkeV that decouple when ultrarelativistic and sterile neutrinos produced resonantly or nonresonantly lead to a primordial phase-space density compatible with cored dShps and disfavor

  11. Constraints on ship NOx emissions in Europe using OMI NO2 observations

    NASA Astrophysics Data System (ADS)

    Vinken, G. C.; Boersma, F.; van Donkelaar, A.; Zhang, L.

    2012-12-01

    Strong emissions of gases and particulate matter by ships affect the composition of the marine boundary layer, with important consequences for climate change, air quality and public health. Because hardly any regulations for the maritime sector exist in international waters, ships are still allowed to burn low-grade marine heavy fuel. As a result, ships emit large quantities of nitrogen oxides (NO x = NO + NO 2), important precursors for ozone (O 3) and particulate matter formation. Previous studies showed that global ship NO x emission inventories amount to 3.0-10.4 Tg N per year (15-30% of total NO x emissions), with most of these emissions within 400 km of the densely populated coastal regions. However, as individual measurements of ship emissions are sparse, and these few measurements are extrapolated, these bottom-up inventories suffer from large uncertainties. In this study we provide top-down constraints on ship NO x emissions in major European ship routes, using observed NO 2 columns from the Ozone Monitoring Instrument (OMI) and NO 2 columns simulated with the nested (0.5o×0.67o) version of the GEOS-Chem chemistry transport model. Two simulations were performed using a plume-in-grid treatment of ship NO x emissions: (1) using EMEP and (2) using AMVER-ICOADS as ship emission inventory. We ensure consistency between the retrievals and model simulations by using the high-resolution GEOS-Chem NO 2 profiles as a priori. The OMI observations suggest that NO x emissions from the (2001) AMVER-ICOADS inventory are too low by a factor of 16 over the ship lane between Spain and the English Channel, and a factor of 10 over the lane between Cairo and Sicily. When comparing the OMI observations against the more recent (2005) EMEP inventory, our method unambiguously shows that ship emissions in the Mediterranean Sea are geographically misplaced by up to 150 km. EMEP emission totals however agree reasonably well with our OMI-constrained emissions over the eastern

  12. Isolating wetland CH4 emissions using the additional constraints of δ13CH4, and C2H6 in a inverse modeling framework

    NASA Astrophysics Data System (ADS)

    Guillermo Nuñez Ramirez, Tonatiuh; Marshall, Julia; Houweling, Sander; Dlugokencky, Edward J.; Worthy, Douglas E. J.; Vaughn, Bruce; Simpson, Isobel; White, James; Brand, Willi A.; Sasakawa, Motoki; Nichol, Silvia; Ramonet, Michel; Tyler, Stanley C.; Hueber, Jacques; Helmig, Detlev; Read, Katie; Punjabi, Schalini; Vanni Gatti, Luciana; Krummel, Paul; Heimann, Martin

    2015-04-01

    Wetlands are the largest single source of atmospheric methane (CH_4). However, estimates of their relative contribution to the atmospheric CH4 budget are highly uncertain. Models of CH4 fluxes from wetlands, which reflect our understanding of the processes driving these fluxes, disagree strongly in their estimates of the total contribution of wetlands to the CH4 budget and in the variability of the fluxes in space and time. Atmospheric CH4 observations can provide a top-down constraint on wetland CH4 flux estimates. Results from atmospheric inverse modeling studies highlight the importance of tropical wetlands in driving interannual variability of atmospheric CH_4. Nevertheless, atmospheric observations in the tropics are scarce, with large areas of strong emissions not covered by the atmospheric observation network. Furthermore, the Bayesian framework, often used in atmospheric inverse modeling, preferentially projects signals onto spatiotemporal regions with large a-priori uncertainty, which is the case of tropical wetlands. Since a large lack of knowledge exists as well for other non-wetland sources of atmospheric CH_4, signals from these could be wrongly allocated to tropical wetlands. The CH4 stable carbon isotope signal (δ13CH_4) and co-emitted species such as ethane (C_2H_6) can provide additional constraints which may be use to discriminate wetland from non-wetland CH4 emissions. We describe the set-up of an inverse modeling framework based on the Jena Inversion System and the TM3 transport model that optimizes CH4 fluxes to fit the observed atmospheric CH_4, δ13CH_4, and C_2H6 signals. The fluxes are optimized with the constraint that each source process was assigned a characteristic range of δ13CH4 signals and methane-to-ethane ratios (MERs). An additional characteristic of our set-up is that no seasonal or interannual variability was included in the wetland a-priori estimate to ensure that all variability is derived exclusively from observations. A

  13. Hořava Gravity in the Effective Field Theory formalism: From cosmology to observational constraints

    NASA Astrophysics Data System (ADS)

    Frusciante, Noemi; Raveri, Marco; Vernieri, Daniele; Hu, Bin; Silvestri, Alessandra

    2016-09-01

    We consider Hořava gravity within the framework of the effective field theory (EFT) of dark energy and modified gravity. We work out a complete mapping of the theory into the EFT language for an action including all the operators which are relevant for linear perturbations with up to sixth order spatial derivatives. We then employ an updated version of the EFTCAMB/EFTCosmoMC package to study the cosmology of the low-energy limit of Hořava gravity and place constraints on its parameters using several cosmological data sets. In particular we use cosmic microwave background (CMB) temperature-temperature and lensing power spectra by Planck 2013, WMAP low- ℓ polarization spectra, WiggleZ galaxy power spectrum, local Hubble measurements, Supernovae data from SNLS, SDSS and HST and the baryon acoustic oscillations measurements from BOSS, SDSS and 6dFGS. We get improved upper bounds, with respect to those from Big Bang Nucleosynthesis, on the deviation of the cosmological gravitational constant from the local Newtonian one. At the level of the background phenomenology, we find a relevant rescaling of the Hubble rate at all epoch, which has a strong impact on the cosmological observables; at the level of perturbations, we discuss in details all the relevant effects on the observables and find that in general the quasi-static approximation is not safe to describe the evolution of perturbations. Overall we find that the effects of the modifications induced by the low-energy Hořava gravity action are quite dramatic and current data place tight bounds on the theory parameters.

  14. SUBARU AND GEMINI OBSERVATIONS OF SS 433: NEW CONSTRAINT ON THE MASS OF THE COMPACT OBJECT

    SciTech Connect

    Kubota, K.; Ueda, Y.; Fabrika, S.; Barsukova, E. A.; Sholukhova, O.; Medvedev, A.; Goranskij, V. P.

    2010-02-01

    We present results of optical spectroscopic observations of the mass donor star in SS 433 with Subaru and Gemini, with an aim to best constrain the mass of the compact object. Subaru/Faint Object Camera and Spectrograph observations were performed on four nights of 2007 October 6-8 and 10, covering the orbital phase of phi = 0.96 - 0.26. We first calculate the cross-correlation function (CCF) of these spectra with that of the reference star HD 9233 in the wavelength range of 4740-4840 A. This region is selected to avoid 'strong' absorption lines accompanied with contaminating emission components, which most probably originate from the surroundings of the donor star, such as the wind and gas stream. The same analysis is applied to archive data of Gemini/GMOS taken at phi = 0.84 - 0.30 by Hillwig and Gies. From the Subaru and Gemini CCF results, the amplitude of the radial velocity curve of the donor star is determined to be 58.3 +- 3.8 km s{sup -1} with a systemic velocity of 59.2 +- 2.5 km s{sup -1}. Together with the radial velocity curve of the compact object, we derive the mass of the donor star and compact object to be M{sub O} = 12.4 +- 1.9 M{sub sun} and M{sub X} = 4.3 +- 0.6 M{sub sun}, respectively. We conclude, however, that these values should be taken as upper limits. From the analysis of the averaged absorption line profiles of strong lines (mostly ions) and weak lines (mostly neutrals) observed with Subaru, we find evidence for heating effects from the compact object. Using a simple model, we find that the true radial velocity amplitude of the donor star could be as low as 40 +- 5 km s{sup -1} in order to produce the observed absorption-line profiles. Taking into account the heating of the donor star may lower the derived masses to M{sub O} = 10.4{sup +2.3}{sub -1.9} M{sub sun} and M{sub X} = 2.5{sup +0.7}{sub -0.6} M{sub sun}. Our final constraint, 1.9 M{sub sun} <=M{sub X}<= 4.9 M{sub sun}, indicates that the compact object in SS 433 is most likely a

  15. Constraints on crystallization of basaltic magma: observations from Kilauea Iki lava lake, Hawaii

    NASA Astrophysics Data System (ADS)

    Helz, Rosalind

    2013-04-01

    Kilauea Iki lava lake is a picritic (average MgO = 15.5%) magma body, approximately 135 m thick, which underwent extensive internal differentiation as it cooled and crystallized from its formation during the eruption of 1959 until final solidification in the mid-nineties. Observations of its initial state include data on the stages of filling of the lava lake, plus the sequence and temperature of lava compositions erupted. Drilling and core recovery (from 1960 to 1988) have documented the state of the lake at specific times, showing that the rate of growth of the upper crust was nearly linear (~2.5 m per year between 1962 and 1979), and that the overall pattern of cooling of the lava lake is consistent with conductive heat loss. Recovery and analysis of partially molten drill core has provided a detailed view of the cooling and differentiation history of the melts and minerals within the lake. Observations that may be relevant to older systems include: (1) documentation of when and to what extent olivine settling occurred in the lake; (2) the observation that the most differentiated part of the lake, which lies within the upper crust at a depth of 20-40 m, had completely crystallized by 1975, and (3) the observation that the position of the last interstitial melt was at 80-85 m down, or 62% of the way down in the lake, as would be predicted from conductive cooling. The lava lake lost heat through its roof faster than through the floor, with the result that the position of most-differentiated horizon is grossly offset from the position of the final melt. Circulation patterns in Kilauea Iki were initially driven by lava input during the eruption plus extensive loss of volatiles. These processes significantly affected the location of foundered crust within the lake, as well as the accumulation of coarse, pre-existing olivine phenocrysts between 50 and 95 m. Subsequently, two other major differentiation processes within the lake were driven by upward movement of low

  16. Airborne observations of total RONO2: new constraints on the yield and lifetime of isoprene nitrates

    NASA Astrophysics Data System (ADS)

    Perring, A. E.; Bertram, T. H.; Wooldridge, P. J.; Fried, A.; Heikes, B. G.; Dibb, J.; Crounse, J. D.; Wennberg, P. O.; Blake, N. J.; Blake, D. R.; Brune, W. H.; Singh, H. B.; Cohen, R. C.

    2009-02-01

    Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments indicate that formation rates of isoprene nitrates are uncertain to a factor of 2-3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunctional nitrates (ΣANs), NO2, total peroxy nitrates (ΣPNs), HNO3, CH2O, isoprene and other VOC were obtained from the NASA DC-8 aircraft during summer 2004 over the continental US during the INTEX-NA campaign. These observations represent the first characterization of ΣANs over a wide range of land surface types and in the lower free troposphere. ΣANs were a significant, 12-20%, fraction of NOy throughout the experimental domain and ΣANs were more abundant when isoprene was high. We use the observed hydrocarbon species to calculate the relative contributions of ΣAN precursors to their production. These calculations indicate that isoprene represents at least three quarters of the ΣAN source in the summertime continental boundary layer of the US. An observed correlation between ΣANs and CH2O is used to place constraints on nitrate yields from isoprene oxidation, atmospheric lifetimes of the resulting nitrates and recycling efficiencies of nitrates during subsequent oxidation. We find reasonable fits to the data using sets of production rates, lifetimes and recycling efficiencies of INs as follows (4.4%, 16 h, 97%), (8%, 2.5 h, 79%) and (12%, 95 min, 67%). The analysis indicates that the lifetime of ΣANs as a pool of compounds is considerably longer than the lifetime of the individual isoprene nitrates to reaction with OH, implying that the organic nitrate

  17. Airborne observations of total RONO2: new constraints on the yield and lifetime of isoprene nitrates

    NASA Astrophysics Data System (ADS)

    Perring, A. E.; Bertram, T. H.; Wooldridge, P. J.; Fried, A.; Heikes, B. G.; Dibb, J.; Crounse, J. D.; Wennberg, P. O.; Blake, N. J.; Brune, W. H.; Blake, D. R.; Cohen, R. C.

    2008-06-01

    Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments indicate that formation rates of isoprene nitrates are uncertain to a factor of 2 3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunction nitrates (ΣANs), NO2, total peroxy nitrates (ΣPNs), HNO3, H2CO, isoprene and other VOC were obtained from the NASA DC-8 aircraft during summer 2004 over the continental US during the INTEX-NA campaign. These observations represent the first characterization of ΣANs over a wide range of land surface types and in the free troposphere. ΣANs were a significant, 12 20%, fraction of NOy throughout the experimental domain and ΣANs were more abundant when isoprene was high. We use the observed VOC to calculate the relative contributions of ΣAN precursors to their production. These calculations indicate that isoprene represents at least 76% of the ΣAN source in the summertime continental boundary layer of the US. An observed correlation between ΣANs and CH2O is used to place constraints on nitrate yields from isoprene oxidation, atmospheric lifetimes of the resulting nitrates and recycling efficiencies of nitrates during subsequent oxidation. We recommend sets of production rates, lifetimes and recycling efficiencies of INs as follows [4.4%, 5 h, 92%], [8%, 2.5 h, 84%] and [12%, 90 min, 74%]. The analysis indicates that the lifetime of ΣANs as a pool of compounds is considerably longer than the lifetime of the individual isoprene nitrates to reaction with OH, implying that the organic nitrate functionality is at least partially maintained through a second oxidation

  18. Constraints on ship NOx emissions in Europe using OMI NO2 observations

    NASA Astrophysics Data System (ADS)

    Vinken, G. C. M.; Boersma, K. F.

    2012-04-01

    About 90% of world trade is transported by oceangoing ships, and seaborne trade has been shown to have increased by about 5% per year in the past decade. Global ship traffic is currently not regulated under international treaties (e.g. Kyoto protocol) and ships are still allowed to burn low-grade bunker fuel. As a result, ships emit large quantities of nitrogen oxides (NOx = NO + NO2), important precursors for ozone (O3) and particulate matter formation. Previous studies indicated that the global NOx emissions from shipping are in the range 3.0-10.4 Tg N per year (15-30% of total global NOx emissions). Because most ships sail within 400 km of the coast, it is important to understand the contribution of ship emissions to atmospheric composition in the densely populated coastal regions. Chemistry Transport Models (CTMs), in combination with emission inventories, are used to simulate atmospheric concentrations of air pollutants to assess the impact of ship emissions. However, these bottom-up inventories, based on extrapolation of a few engine measurements and strong assumptions, suffer from large uncertainties. In this study we provide top-down constraints on ship NOx emissions in Europe using satellite observations of NO2 columns. We use the nested version of the GEOS-Chem model (0.5°-0.667°) to simulate tropospheric NO2 columns over Europe for the years 2005-2006, using our plume-in-grid treatment of ship NOx emissions. We improve the NO2 retrievals from the Ozone Monitoring Instrument (OMI v2.0) by replacing the coarse a priori (TM4) vertical NO2 profiles (2°-3°) with the high-resolution GEOS-Chem profiles. This ensures consistency between the retrievals and model simulations. GEOS-Chem simulations of tropospheric NO2 columns show remarkable quantitative agreement with the observed OMI columns over Europe (R2=0.89, RMS difference < 0.2-1015 molec. cm-2), providing confidence in the ability of the model to simulate NO2 pollution over the European mainland. We

  19. Potentials and constraints of different types of soil moisture observations for flood simulations in headwater catchments

    NASA Astrophysics Data System (ADS)

    Bronstert, A.; Creutzfeldt, B.; Graeff, T.; Hajnsek, I.; Heistermann, M.; Itzerott, S.; Jagdhuber, T.; Kneis, D.; Lück, E.; Reusser, D.; Zehe, E.

    2012-04-01

    Flood generation in mountainous headwater catchments is governed by rainfall intensities, by the spatial distribution of rainfall and by the state of the catchment prior to the rainfall, e.g. by the spatial pattern of the soil moisture, groundwater conditions, and possibly snow. The work presented here explores the limits and potentials of measuring soil moisture with different methods and in different scales and their potential use for flood simulation. These measurements were obtained in 2007 and 2008 within a comprehensive multi-scale experiment in the Weisseritz headwater catchment in the Ore-Mountains, Germany. The following technologies have been applied jointly thermogravimetric method, Frequency Domain Reflectometry (FDR) sensors, Spatial-Time Domain Reflectometry (STDR) cluster, Ground Penetrating Radar (GPR), airborne polarimetric synthetic aperture radar (polarimetric-SAR) and Advanced Synthetic Aperture Radar (ASAR) based on the satellite Envisat. We present exemplary soil measurement results, with spatial scales ranging from point scale, via hillslope and field scale to the catchment scale. Only the Spatial-TDR cluster was able to record continuous data. The other methods are limited to the date of over flights (airplane and satellite) or measurement campaigns on the ground. At a first glance, using soil moisture data to initiate better flood modelling (including flood forecasts) seems to be a rather straight forward approach. However, this approach bears several problems regarding the operational use of such data and the model parameterisation: 1) A main constraint is that the observation of spatially distributed soil moisture and the subsequent data processing are still far from an operational stage because continuous or quasi-continuous air-borne observation and processing of soil moisture is not available; 2) remote soil moisture sensors observe only a quite shallow soil depths, which are of restricted relevance for flood generation and water

  20. Subaru And Gemini Observations Of SS 433: New Constraint On The Mass Of The Compact Object

    NASA Astrophysics Data System (ADS)

    Kubota, K.; Ueda, Y.; Fabrika, S.; Medvedev, A.; Barsukova, E. A.; Sholukhova, O.; Goranskij, V. P.

    2010-02-01

    We present results of optical spectroscopic observations of the mass donor star in SS 433 with Subaru and Gemini, with an aim to best constrain the mass of the compact object. Subaru/Faint Object Camera and Spectrograph observations were performed on four nights of 2007 October 6-8 and 10, covering the orbital phase of phi = 0.96 - 0.26. We first calculate the cross-correlation function (CCF) of these spectra with that of the reference star HD 9233 in the wavelength range of 4740-4840 Å. This region is selected to avoid "strong" absorption lines accompanied with contaminating emission components, which most probably originate from the surroundings of the donor star, such as the wind and gas stream. The same analysis is applied to archive data of Gemini/GMOS taken at phi = 0.84 - 0.30 by Hillwig & Gies. From the Subaru and Gemini CCF results, the amplitude of the radial velocity curve of the donor star is determined to be 58.3 ± 3.8 km s-1 with a systemic velocity of 59.2 ± 2.5 km s-1. Together with the radial velocity curve of the compact object, we derive the mass of the donor star and compact object to be M O = 12.4 ± 1.9 M sun and M X = 4.3 ± 0.6 M sun, respectively. We conclude, however, that these values should be taken as upper limits. From the analysis of the averaged absorption line profiles of strong lines (mostly ions) and weak lines (mostly neutrals) observed with Subaru, we find evidence for heating effects from the compact object. Using a simple model, we find that the true radial velocity amplitude of the donor star could be as low as 40 ± 5 km s-1 in order to produce the observed absorption-line profiles. Taking into account the heating of the donor star may lower the derived masses to M O = 10.4+2.3 -1.9 M sun and M X = 2.5+0.7 -0.6 M sun. Our final constraint, 1.9 M sun <=M X<= 4.9 M sun, indicates that the compact object in SS 433 is most likely a low mass black hole, although the possibility of a massive neutron star cannot be firmly

  1. Observational constraints on star cluster formation theory. I. The mass-radius relation

    NASA Astrophysics Data System (ADS)

    Pfalzner, S.; Kirk, H.; Sills, A.; Urquhart, J. S.; Kauffmann, J.; Kuhn, M. A.; Bhandare, A.; Menten, K. M.

    2016-02-01

    Context. Stars form predominantly in groups usually denoted as clusters or associations. The observed stellar groups display a broad spectrum of masses, sizes, and other properties, so it is often assumed that there is no underlying structure in this diversity. Aims: Here we show that the assumption of an unstructured multitude of cluster or association types might be misleading. Current data compilations of clusters in the solar neighbourhood show correlations among cluster mass, size, age, maximum stellar mass, etc. In this first paper we take a closer look at the correlation of cluster mass and radius. Methods: We use literature data to explore relations in cluster and molecular core properties in the solar neighbourhood. Results: We show that for embedded clusters in the solar neighbourhood a clear correlation exists between cluster mass and half-mass radius of the form Mc = CRcγ with γ = 1.7 ± 0.2. This correlation holds for infrared K-band data, as well as for X-ray sources and clusters containing a hundred stars up to those consisting of a few tens of thousands of stars. The correlation is difficult to verify for clusters containing fewer than 30 stars owing to low-number statistics. Dense clumps of gas are the progenitors of the embedded clusters. We find almost the same slope for the mass-size relation of dense, massive clumps as for the embedded star clusters. This might point to a direct translation from gas to stellar mass: however, it is difficult to relate size measurements for clusters (stars) to those for gas profiles. Taking multiple paths for clump mass into cluster mass into account, we obtain an average star-formation efficiency of 18%+9.3-5.7 for the embedded clusters in the solar neighbourhood. Conclusions: The derived mass-radius relation gives constraints for the theory of clustered star formation. Analytical models and simulations of clustered star formation have to reproduce this relation in order to be realistic.

  2. Constraint on the velocity dependent dark matter annihilation cross section from Fermi-LAT observations of dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Bi, Xiao-Jun; Jia, Huan-Yu; Yin, Peng-Fei; Zhu, Feng-Rong

    2016-04-01

    The γ -ray observation of dwarf spheroidal satellites (dSph's) is an ideal approach for probing the dark matter (DM) annihilation signature. The latest Fermi-LAT dSph searches have set stringent constraints on the velocity independent annihilation cross section in the small DM mass range, which gives very strong constraints on the scenario to explain the AMS-02 positron excess by DM annihilation. However, the dSph constraints would change in the velocity dependent annihilation scenarios, because the velocity dispersion in the dSph's varies from that in the Milky Way. In this work, we use a likelihood map method to set constraints on the velocity dependent annihilation cross section from the Fermi-LAT observation of six dSph's. We consider three typical forms of the annihilation cross section, i.e. p-wave annihilation, Sommerfeld enhancement, and Breit-Wigner resonance. For the p-wave annihilation and Sommerfeld enhancement, the dSph limits would become much weaker and stronger compared with those for the velocity independent annihilation, respectively. For the Breit-Wigner annihilation, the dSph limits would vary depending on the model parameters. We show that the scenario to explain the AMS-02 positron excess by DM annihilation is still viable in the velocity dependent cases.

  3. An Exact Expression to Calculate the Derivatives of Position-Dependent Observables in Molecular Simulations with Flexible Constraints

    PubMed Central

    Echenique, Pablo; Cavasotto, Claudio N.; De Marco, Monica; Garca-Risueño, Pablo; Alonso, J.L.

    2011-01-01

    In this work, we introduce an algorithm to compute the derivatives of physical observables along the constrained subspace when flexible constraints are imposed on the system (i.e., constraints in which the constrained coordinates are fixed to configuration-dependent values). The presented scheme is exact, it does not contain any tunable parameter, and it only requires the calculation and inversion of a sub-block of the Hessian matrix of second derivatives of the function through which the constraints are defined. We also present a practical application to the case in which the sought observables are the Euclidean coordinates of complex molecular systems, and the function whose minimization defines the flexible constraints is the potential energy. Finally, and in order to validate the method, which, as far as we are aware, is the first of its kind in the literature, we compare it to the natural and straightforward finite-differences approach in a toy system and in three molecules of biological relevance: methanol, N-methyl-acetamide and a tri-glycine peptide. PMID:21931757

  4. Constraints on an exosphere at Ceres from Hubble Space Telescope observations

    NASA Astrophysics Data System (ADS)

    Roth, Lorenz; Ivchenko, Nickolay; Retherford, Kurt D.; Cunningham, Nathaniel J.; Feldman, Paul D.; Saur, Joachim; Spencer, John R.; Strobel, Darrell F.

    2016-03-01

    We report far ultraviolet observations of Ceres obtained with the Cosmic Origin Spectrograph (COS) of the Hubble Space Telescope in the search for atomic emissions from an exosphere. The derived brightnesses at the oxygen lines at 1304 Å and 1356 Å are consistent with zero signals within the 1σ propagated statistical uncertainties. The OI 1304 Å brightness of 0.12 ± 0.20 Rayleighs can be explained by solar resonant scattering from an atomic oxygen column density of (8.2 ± 13.4) × 1010 cm-2. Assuming that O is produced by photodissociation of H2O, we derive an upper limit for H2O abundance and compare it to previous observations. Our upper limit is well above the expected O brightness for a tenuous sublimated H2O exosphere, but it suggests that H2O production with a rate higher than 4 × 1026 molecules s-1 was not present at the time of the COS observation. Additionally, we derive an extremely low geometric albedo of ˜1% in the 1300 Å to 1400 Å range.

  5. Constraints on Common Envelope Magnetic Fields from Observations of Jets in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    De Marco, Orsola; Tocknell, J.; Wardle, M.

    2014-01-01

    The common envelope (CE) interaction describes the swallowing of a nearby companion by a growing, evolving star. CEs that take place during the asymptotic giant branch phase of the primary and may lead to the formation of a planetary nebula (PN) with a post-CE close binary in the middle. We have used published observations of masses and kinematics of jets in four post-CE PN to infer physical characteristics of the CE interaction. In three of the four systems studied, Abell 63, ETHOS 1 and the Necklace PN, the kinematics indicate that the jets were launched a few thousand years before the CE and we favour a scenario where this happened before Roche lobe overflow, although better models of wind accretion and wind Roche lobe overflow are needed. The magnetic fields inferred to launch pre-CE jets are of the order of a few Gauss. In the fourth case, NGC 6778, the kinematics indicate that the jets were launched about 3000 years after the CE interaction. Magnetic fields of the order of a few hundreds to a few thousands Gauss are inferred in this case, approximately in line with predictions of post-CE magnetic fields. However, we remark that in the case of this system, we cannot find a reasonable scenario for the formation of the two jet pairs observed: the small orbital separation would preclude the formation of even one accretion disk able to supply the necessary accretion rate to cause the observed jets. Additional and improved observations of post-CE PN will provide a powerful tool to constrain the CE interaction.

  6. New Constraints on Cosmic Polarization Rotation from the ACTPol Cosmic Microwave Background B-mode Polarization Observation and the BICEP2 Constraint Update

    NASA Astrophysics Data System (ADS)

    Mei, Hsien-Hao; Ni, Wei-Tou; Pan, Wei-Ping; Xu, Lixin; di Serego Alighieri, Sperello

    2015-06-01

    Recently, ACTPol measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB, and EB power spectra in the multipole range 225-8725. In our previous paper (Paper I), we jointly analyzed the results of three experiments on the CMB B-mode polarization—SPTpol, POLARBEAR, and BICEP2—to include in the model, in addition to the gravitational lensing and inflationary gravitational waves components, the fluctuation effects induced by cosmic polarization rotation (CPR) if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle < α > and its fluctuation < δ {{α }2}> from the new ACTPol data, and update our fitting of CPR fluctuations using the BICEP2 data taking the new Planck dust measurement results into consideration. We follow the same method used in Paper I. The mean CPR angle is constrained from the EB correlation power spectra to |< α > |\\lt 14 mrad (0.°8) and the fluctuation (rms) is constrained from the BB correlation power spectra to {{< δ {{α }2}> }1/2}\\lt 29.3 mrad (1.°68). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give < α > =1.0+/- 0\\buildrel{\\circ}\\over{.} 63. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. Using the new Planck dust measurement, we update our fits of the BICEP2 CPR fluctuation constraint to be 32.8 mrad (1.°88). The joint ACTPol-BICEP2-POLARBEAR CPR fluctuation constraint is 23.7 mrad (1.°36).

  7. New Constraints on Cosmic Polarization Rotation from the ACTPol Cosmic Microwave Background B-mode Polarization Observation and the BICEP2 Constraint Update

    NASA Astrophysics Data System (ADS)

    Mei, Hsien-Hao; Ni, Wei-Tou; Pan, Wei-Ping; Xu, Lixin; di Serego Alighieri, Sperello

    2015-06-01

    Recently, ACTPol measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB, and EB power spectra in the multipole range 225–8725. In our previous paper (Paper I), we jointly analyzed the results of three experiments on the CMB B-mode polarization—SPTpol, POLARBEAR, and BICEP2—to include in the model, in addition to the gravitational lensing and inflationary gravitational waves components, the fluctuation effects induced by cosmic polarization rotation (CPR) if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle < α > and its fluctuation < δ {{α }2}> from the new ACTPol data, and update our fitting of CPR fluctuations using the BICEP2 data taking the new Planck dust measurement results into consideration. We follow the same method used in Paper I. The mean CPR angle is constrained from the EB correlation power spectra to |< α > |\\lt 14 mrad (0.°8) and the fluctuation (rms) is constrained from the BB correlation power spectra to {{< δ {{α }2}> }1/2}\\lt 29.3 mrad (1.°68). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give < α > =1.0+/- 0\\buildrel{\\circ}\\over{.} 63. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. Using the new Planck dust measurement, we update our fits of the BICEP2 CPR fluctuation constraint to be 32.8 mrad (1.°88). The joint ACTPol-BICEP2-POLARBEAR CPR fluctuation constraint is 23.7 mrad (1.°36).

  8. Experimental observation of controllable kinetic constraints in a cold atomic gas

    NASA Astrophysics Data System (ADS)

    Valado, M. M.; Simonelli, C.; Hoogerland, M. D.; Lesanovsky, I.; Garrahan, J. P.; Arimondo, E.; Ciampini, D.; Morsch, O.

    2016-04-01

    Many-body systems relaxing to equilibrium can exhibit complex dynamics even if their steady state is trivial. In situations where relaxation requires highly constrained local particle rearrangements, such as in glassy systems, this dynamics can be difficult to analyze from first principles. The essential physical ingredients, however, can be captured by idealized lattice models with so-called kinetic constraints. While so far constrained dynamics has been considered mostly as an effective and idealized theoretical description of complex relaxation, here we experimentally realize a many-body system exhibiting manifest kinetic constraints and measure its dynamical properties. In the cold Rydberg gas used in our experiments, the nature of the kinetic constraints can be tailored through the detuning of the excitation lasers from resonance. The system undergoes a dynamics which is characterized by pronounced spatial correlations or anticorrelations, depending on the detuning. Our results confirm recent theoretical predictions, and highlight the analogy between the dynamics of interacting Rydberg gases and that of certain soft-matter systems.

  9. Constraints on energy release in solar flares from RHESSI and GOES X-ray observations. II. Energetics and energy partition

    NASA Astrophysics Data System (ADS)

    Warmuth, A.; Mann, G.

    2016-04-01

    Aims: We derive constraints on energy release, transport and conversion processes in solar flares based on a detailed characterization of the physical parameters of both the thermal plasma and the accelerated nonthermal electrons based on X-ray observations. In particular, we address the questions of whether the energy required to heat the thermal plasma can be supplied by nonthermal particles, and how the energetics derived from X-rays compare to the total bolometric radiated energy. Methods: Time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 were obtained using RHESSI hard X-ray observations. This has been supplemented by GOES soft X-ray fluxes. In our companion Paper I, we have used this data set to obtain the basic physical parameters for the thermal plasma (using the isothermal approximation) and the injected energetic electrons (assuming the thick-target model). Here, we used this data set to derive the flare energetics, including thermal energy, radiative and conductive energy loss, gravitational and flow energy of the plasma, and kinetic energy of the injected electrons. We studied how the thermal energies compare to the energy in nonthermal electrons, and how the various energetics and energy partition depend on flare importance. Results: All flare energetics show a good to excellent correlation with the peak GOES flux. The gravitational energy of the evaporated plasma and the kinetic energy of plasma flows can be neglected in the discussion of flare energetics. The radiative energy losses are comparable to the maximum thermal energy, while the conductive losses are considerably higher than the maximum thermal energy, especially in weaker flares. The total heating requirement of the hot plasma amounts to ≈50% of the total bolometric energy loss, with the conductive losses as a major contribution. The nonthermal energy input by energetic electrons is not sufficient to account for the total heating requirements of

  10. Physical properties of volcanic lightning: Constraints from magnetotelluric and video observations at Sakurajima volcano, Japan

    NASA Astrophysics Data System (ADS)

    Aizawa, Koki; Cimarelli, Corrado; Alatorre-Ibargüengoitia, Miguel A.; Yokoo, Akihiko; Dingwell, Donald B.; Iguchi, Masato

    2016-06-01

    The lightning generated by explosive volcanic eruptions is of interest not only as a promising technique for monitoring volcanic activity, but also for its broader implications and possible role in the origin of life on Earth, and its impact on the atmosphere and biosphere of the planet. However, at present the genetic mechanisms and physical properties of volcanic lightning remain poorly understood, as compared to our understanding of thundercloud lightning. Here, we present joint magnetotelluric (MT) data and video imagery that were used to investigate the physical properties of electrical discharges generated during explosive activity at Sakurajima volcano, Japan, and we compare these data with the characteristics of thundercloud lightning. Using two weeks of high-sensitivity, high-sample-rate MT data recorded in 2013, we detected weak electromagnetic signals radiated by volcanic lightning close to the crater. By carefully inspecting all MT waveforms that synchronized with visible flashes, and comparing with high-speed (3000 frame/s) and normal-speed (30 frame/s) videos, we identified two types of discharges. The first type consists of impulses (Type A) and is interpreted as cloud-to-ground (CG) lightning. The second type is characterized by weak electromagnetic variations with multiple peaks (Type B), and is interpreted as intra-cloud (IC) lightning. In addition, we observed a hybrid MT event wherein a continuous weak current accompanied Type A discharge. The observed features of volcanic lightning are similar to thunderstorm lightning, and the physical characteristics show that volcanic lightning can be treated as a miniature version of thunderstorm lightning in many respects. The overall duration, length, inter-stroke interval, peak current, and charge transfer all exhibit values 1-2 orders of magnitude smaller than those of thunderstorm lightning, thus suggesting a scaling relation between volcanic and thunderstorm lightning parameters that is independent of

  11. Constraints on the Compositions of Phobos and Deimos from Visible/Near Infrared Observations

    NASA Astrophysics Data System (ADS)

    Fraeman, Abigail; Murchie, S.; Clark, R.; Morris, R.; Arvidson, R.; Rivkin, A.; Vilas, F.

    2013-10-01

    Mapping of mineral absorptions on Phobos and Deimos using recently acquired visible and near infrared observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) shows that Fe2+ electronic absorptions diagnostic of olivine and pyroxene are absent, indicating the moons' surfaces are inconsistent with a composition like that of bulk Mars or Mars crustal material. There is a broad absorption centered around 0.65 µm within the redder spectral unit on Phobos and ubiquitously present on Deimos, and the occurrence of this feature is independently confirmed by telescopic spectra of Phobos collected from the Mayall 4-m telescope. A comparable 0.65 µm feature is also found to be present among numerous other low-albedo solar system bodies. Thermally corrected CRISM spectra additionally show a 2.7 μm feature present in spectra collected across all of Phobos and Deimos, and this feature is generally stronger in red unit material. The shape and position of the 2.7 μm band are consistent with an OH related feature. The origin of the 0.65 um feature is uncertain, and we will discuss evidence for or against it being one of several candidate phases including a mixture of microphase and nanophase metallic iron that may have formed on the moons' surfaces through space weathering, as has been proposed for dark material on Iapetus, or an Fe-bearing phyllosilicate, a common mineral in the moons' closest spectral analogs CM chrondrites. Overall, the CRISM observations indicate Phobos and Deimos most likely have a composition consistent with a primitive, hydroxyl-bearing material everywhere, with a variation in the phase that is responsible for the 0.65 µm band. Spectral data with a greater spectral range, including into the vacuum ultraviolet, could help further constrain the 0.65 µm phase, although in situ investigation will be necessary for definitive identification off the responsible material.

  12. Constraints on dark energy from new observations including Pan-STARRS

    SciTech Connect

    Zheng, Wei; Li, Si-Yu; Li, Hong; Xia, Jun-Qing; Li, Mingzhe; Lu, Tan E-mail: lisy@ihep.ac.cn E-mail: xiajq@ihep.ac.cn E-mail: t.lu@pmo.ac.cn

    2014-08-01

    In this paper, we set the new limits on the equation of state parameter (EoS) of dark energy with the observations of cosmic microwave background radiation (CMB) from Planck satellite, the type Ia supernovae from Pan-STARRS and the baryon acoustic oscillation (BAO). We consider two parametrization forms of EoS: a constant w and time evolving w(a)=w{sub 0}+w{sub a}(1-a). The results show that with a constant EoS, w=-1.141±0.075 68% C.L.), which is consistent with ΛCDM at about 2σ confidence level. For a time evolving w(a) model, we get w{sub 0}=-1.09{sup +0.16}{sub -0.18} 1σ C.L.), w{sub a}=-0.34{sup +0.87}{sub -0.51} 1σ C.L.), and in this case ΛCDM can be comparable with our observational data at 1σ confidence level. In order to do the parametrization independent analysis, additionally we adopt the so called principal component analysis (PCA) method, in which we divide redshift range into several bins and assume w as a constant in each redshift bin (bin-w). In such bin-w scenario, we find that for most of the bins cosmological constant can be comparable with the data, however, there exists few bins which give w deviating from ΛCDM at more than 2σ confidence level, which shows a weak hint for the time evolving behavior of dark energy. To further confirm this hint, we need more data with higher precision.

  13. Constraints on axino warm dark matter from X-ray observation at the Chandra telescope and SPI

    SciTech Connect

    Dey, Paramita; Mukhopadhyaya, Biswarup; Roy, Sourov; Vempati, Sudhir K. E-mail: biswarup@hri.res.in E-mail: vempati@cts.iisc.ernet.in

    2012-05-01

    A sufficiently long lived warm dark matter could be a source of X-rays observed by satellite based X-ray telescopes. We consider axinos and gravitinos with masses between 1 keV and 100 keV in supersymmetric models with small R-parity violation. We show that axino dark matter receives significant constraints from X-ray observations of Chandra and SPI, especially for the lower end of the allowed range of the axino decay constant f{sub a}, while the gravitino dark matter remains unconstrained.

  14. NuSTAR observations of the bullet cluster: constraints on inverse Compton emission

    SciTech Connect

    Wik, Daniel R.; Zhang, W. W.; Molendi, S.; Gastaldello, F.; Madejski, G.; Harrison, F. A.; Grefenstette, B. W.; Madsen, K. K.; Zoglauer, A.; Boggs, S. E.; Craig, W. W.; Kitaguchi, T.; Hailey, C. J.; Stern, D.

    2014-09-01

    The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Because all prior telescopes sensitive at E > 10 keV do not focus light and have degree-scale fields of view, their backgrounds are both high and difficult to characterize. The associated uncertainties result in lower sensitivity to IC emission and a greater chance of false detection. In this work, we present 266 ks NuSTAR observations of the Bullet cluster, which is detected in the energy range 3-30 keV. NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies, the background still dominates and must be well understood. To this end, we have developed a complete background model constructed of physically inspired components constrained by extragalactic survey field observations, the specific parameters of which are derived locally from data in non-source regions of target observations. Applying the background model to the Bullet cluster data, we find that the spectrum is well—but not perfectly—described as an isothermal plasma with kT = 14.2 ± 0.2 keV. To slightly improve the fit, a second temperature component is added, which appears to account for lower temperature emission from the cool core, pushing the primary component to kT ∼ 15.3 keV. We see no convincing need to invoke an IC component to describe the spectrum of the Bullet cluster, and instead argue that it is dominated at all energies by emission from purely thermal gas. The conservatively derived 90% upper limit on the IC flux of 1.1 × 10{sup –12} erg s{sup –1} cm{sup –2} (50-100 keV), implying a lower limit on B ≳ 0.2 μG, is barely consistent with detected fluxes previously reported. In addition to discussing the possible origin of this discrepancy, we remark on the

  15. Structural observations from the Canavese Fault west of Valle d'Ossola (Piemonte) and some time constraints

    NASA Astrophysics Data System (ADS)

    Pleuger, Jan; Mancktelow, Neil

    2010-05-01

    The Canavese Fault (CF) is the SW part of the most important fault system in the Alps, the Periadriatic Fault. The CF has a complex kinematic history involving an older stage of NW-side-up faulting and a younger stage of SE-side-up plus dextral faulting in the area of Valle d'Ossola (Schmid et al. 1987). There, shearing occurred under greenschist-facies conditions and the fault is a c. 1 km thick mylonite zone. Toward SW, faulting took place under progressively lower temperatures and the volume of rocks affected by S-side-up plus dextral shearing becomes larger at the expense of the N-side-up mylonites. S of Valle Sesia, brittle fault rocks dominate over mylonites. Still further SW, close to the Serra d'Ivrea, the CF splits into two branches, the Internal Canavese Fault (ICF) and the External Canavese Fault (ECF). S-side-up plus dextral faulting is localised along the ICF while the observed displacement senses at the ECF are mostly, though not always, N-side-up and sinistral. Age constraints for faulting along the CF are mostly derived from absolute ages of magmatic rocks exposed alongside or within the fault. In the section around Biella, NW-side-up faulting cannot have lasted longer than until 31±2 Ma (Scheuring et al. 1974) because this is the age of andesites overlying the basement of the Penninic Sesia Zone. However, some additional uplift of the Sesia Zone with respect to the South Alpine Ivrea Zone was accommodated by down-to-the-SE tilting of the Sesia zone around a roughly NNE-SSW-trending subhorizontal axis which is evidenced by palaeomagnetic data (Lanza 1977). As a result of that, the Early Oligocene Biella Pluton (c. 31 Ma, Romer et al. 1996) today occupies a similar altitude level as the andesites of the same age. Post-31-Ma uplift of the Ivrea Zone with respect to the andesites is evidenced by the Early Oligocene (29-33 Ma, Carraro & Ferrara 1968) Miagliano Pluton which is hosted by the Ivrea Zone rocks and exposed at the present topographic surface

  16. Constraints on the Detection of the Solar Nebula's Oxidation State Through Asteroid Observations

    NASA Technical Reports Server (NTRS)

    Abell, P. A.; Gaffey, M. J.; Hardersen, P. S.

    2005-01-01

    Introduction: Asteroids represent the only in situ surviving population of planetesimals from the formation of the inner solar system and therefore include materials from the very earliest stages of solar system formation. Hence, these bodies can provide constraints on the processes and conditions that were present during this epoch and can be used to test current models and theories describing the late solar nebula, the early solar system and subsequent planetary accretion. From detailed knowledge of asteroid mineralogic compositions the probable starting materials, thermal histories, and oxidation states of asteroid parent bodies can be inferred. If such data can be obtained from specific mainbelt source regions, then this information can be used to map out the formation conditions of the late solar nebula within the inner solar system and possibly distinguish any trends in oxidation state that may be present.

  17. Observational Constraints on the Nature of the Dark Energy: First Cosmological Results From the ESSENCE Supernova Survey

    SciTech Connect

    Wood-Vasey, W.Michael; Miknaitis, G.; Stubbs, C.W.; Jha, S.; Riess, A.G.; Garnavich, P.M.; Kirshner, R.P.; Aguilera, C.; Becker, A.C.; Blackman, J.W.; Blondin, S.; Challis, P.; Clocchiatti, A.; Conley, A.; Covarrubias, R.; Davis, T.M.; Filippenko, A.V.; Foley, R.J.; Garg, A.; Hicken, M.; Krisciunas, K.; /Harvard-Smithsonian Ctr. Astrophys. /Fermilab /Harvard U. /UC, Berkeley, Astron. Dept. /KIPAC, Menlo Park /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Notre Dame U. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Res. Sch. Astron. Astrophys., Weston Creek /Chile U., Catolica /Toronto U., Astron. Dept. /Bohr Inst. /Stockholm U. /Texas A-M /European Southern Observ. /NOAO, Tucson /Ohio State U., Dept. Astron. /Inst. Astron., Honolulu

    2007-01-05

    We present constraints on the dark energy equation-of-state parameter, w = P/({rho}c{sup 2}), using 60 Type Ia supernovae (SNe Ia) from the ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat Universe. By including constraints on ({Omega}{sub M}, w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1.05{sub -0.12}{sup +0.13} (stat 1{sigma}) {+-} 0.13 (sys) and {Omega}{sub M} = 0.274{sub -0.020}{sup +0.033} (stat 1{sigma}) with a best-fit {chi}{sup 2}/DoF of 0.96. These results are consistent with those reported by the Super-Nova Legacy Survey in a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic currently with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the SuperNova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1.07{sub -0.09}{sup +0.09} (stat 1{sigma}) {+-} 0.13 (sys), {Omega}{sub M} = 0.267{sub -0.018}{sup +0.028} (stat 1{sigma}) with a best-fit {chi}{sup 2}/DoF of 0.91. The current SNe Ia data are fully consistent with a cosmological constant.

  18. 40 CFR 26.304 - Additional protections for pregnant women and fetuses involved in observational research.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... research. The provisions of 45 CFR 46.204 are applicable to this section. ... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Additional protections for pregnant... Protections for Pregnant Women and Fetuses Involved as Subjects in Observational Research Conducted...

  19. Learning by observation in the macaque monkey under high experimental constraints.

    PubMed

    Isbaine, Faiçal; Demolliens, Marie; Belmalih, Abdelouahed; Brovelli, Andrea; Boussaoud, Driss

    2015-08-01

    While neuroscience research has tremendously advanced our knowledge about the neural mechanisms of individual learning, i.e. through trial-and-error, it is only recently that neuroscientists have begun to study observational learning, and thus little is known about its neural mechanisms. One limitation is that observational learning has been addressed under unconstrained experimental conditions, not compatible with neuronal recordings. This study examined observational learning in macaque monkeys under the constraining conditions of behavioral neurophysiology. Two animals sat in primate chairs facing each other, with their head fixed. A touch screen was placed face up between the chairs at arm's reach, and the monkeys were trained on an abstract visuomotor associative task. In one experiment, the monkeys alternated the roles of "actor" and "observer". The actor learned to associate visual cues with reaching targets, while the observer "watched" freely. Then, the observer was given the same cue-target associations just performed by the actor, or had to learn new, not previously observed ones. The results show that learning performance is better after observation. In experiment 2, one monkey learned from a human actor who performed the task with errors only, or with successes only in separate blocks. The monkey's gain in performance was higher after observation of errors than after successes. The findings suggest that observational learning can occur even under highly constraining conditions, and open the way for investigating the neuronal correlates of social learning using the methods of behavioral neurophysiology. PMID:25934491

  20. Modeling the chemistry of the dense interstellar clouds. I - Observational constraints for the chemistry

    NASA Technical Reports Server (NTRS)

    Federman, S. R.; Huntress, W. T., Jr.; Prasad, S. S.

    1990-01-01

    A search for correlations arising from molecular line data is made in order to place constraints on the chemical models of interstellar clouds. At 10 to the 21st H2/sq cm, N(CO) for dark clouds is a factor of six greater than the value for diffuse clouds. This implies that the strength of the UV radiation field where CO shields itself from dissociation is about one-half the strength of the average Galactic field. The dark cloud data indicate that the abundance of CO continues to increase with A(V) for directions with A(V) of 4 mag or less, although less steeply with N(H2) than for diffuse clouds. For H2CO, a quadratic relationship is obtained in plots versus H2 column density. The data suggest a possible turnover at the highest values for A(V). NH3 shows no correlation with H2, C(O-18), HC3N, or HC5N; a strong correlation is found between HC5N and HC3N, indicating a chemical link between the cyanopolyynes.

  1. New Constraints on Galaxy Cluster Evolution from Chandra Observations of SPT-Selected Clusters

    NASA Astrophysics Data System (ADS)

    McDonald, M.

    2014-07-01

    In the past 4 years, the number of known galaxy clusters at z>0.5 has grown by a factor of >5, thanks primarily to Sunyaev Zel'dovich surveys such as Planck, the Atacama Cosmology Telescope, and the South Pole Telescope (SPT). Here, I present several important results from the SPT 2500 deg^2 survey, which has discovered over 500 new galaxy clusters, more than 300 of which are at z>0.5. Using data primarily from the Chandra X-ray Observatory, we determine evolutionary trends in the central cluster galaxy (inner ˜20 kpc), the cluster core (inner ˜100 kpc), and cluster outskirts (>1 Mpc) over the past 8 Gyr, addressing such outstanding issues as the cooling flow problem, the effects of AGN feedback, and subhalo accretion, or clumping, at the virial radius. These studies are providing the most detailed constraints to date on the evolution of galaxy clusters on all physical scales, and will continue to improve with the next generation of surveys already upon us.

  2. Simulation of atmospheric N2O with GEOS-Chem and its adjoint: evaluation of observational constraints

    NASA Astrophysics Data System (ADS)

    Wells, K. C.; Millet, D. B.; Bousserez, N.; Henze, D. K.; Chaliyakunnel, S.; Griffis, T. J.; Luan, Y.; Dlugokencky, E. J.; Prinn, R. G.; O'Doherty, S.; Weiss, R. F.; Dutton, G. S.; Elkins, J. W.; Krummel, P. B.; Langenfelds, R.; Steele, L. P.; Kort, E. A.; Wofsy, S. C.; Umezawa, T.

    2015-10-01

    We describe a new 4D-Var inversion framework for nitrous oxide (N2O) based on the GEOS-Chem chemical transport model and its adjoint, and apply it in a series of observing system simulation experiments to assess how well N2O sources and sinks can be constrained by the current global observing network. The employed measurement ensemble includes approximately weekly and quasi-continuous N2O measurements (hourly averages used) from several long-term monitoring networks, N2O measurements collected from discrete air samples onboard a commercial aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container; CARIBIC), and quasi-continuous measurements from the airborne HIAPER Pole-to-Pole Observations (HIPPO) campaigns. For a 2-year inversion, we find that the surface and HIPPO observations can accurately resolve a uniform bias in emissions during the first year; CARIBIC data provide a somewhat weaker constraint. Variable emission errors are much more difficult to resolve given the long lifetime of N2O, and major parts of the world lack significant constraints on the seasonal cycle of fluxes. Current observations can largely correct a global bias in the stratospheric sink of N2O if emissions are known, but do not provide information on the temporal and spatial distribution of the sink. However, for the more realistic scenario where source and sink are both uncertain, we find that simultaneously optimizing both would require unrealistically small errors in model transport. Regardless, a bias in the magnitude of the N2O sink would not affect the a posteriori N2O emissions for the 2-year timescale used here, given realistic initial conditions, due to the timescale required for stratosphere-troposphere exchange (STE). The same does not apply to model errors in the rate of STE itself, which we show exerts a larger influence on the tropospheric burden of N2O than does the chemical loss rate over short (< 3 year) timescales. We use a

  3. Fermi-LAT constraints on dark matter annihilation cross section from observations of the Fornax cluster

    SciTech Connect

    Ando, Shin'ichiro; Nagai, Daisuke E-mail: daisuke.nagai@yale.edu

    2012-07-01

    We analyze 2.8-yr data of 1–100 GeV photons for clusters of galaxies, collected with the Large Area Telescope onboard the Fermi satellite. By analyzing 49 nearby massive clusters located at high Galactic latitudes, we find no excess gamma-ray emission towards directions of the galaxy clusters. Using flux upper limits, we show that the Fornax cluster provides the most stringent constraints on the dark matter annihilation cross section. Stacking a large sample of nearby clusters does not help improve the limit for most dark matter models. This suggests that a detailed modeling of the Fornax cluster is important for setting robust limits on the dark matter annihilation cross section based on clusters. We therefore perform the detailed mass modeling and predict the expected dark matter annihilation signals from the Fornax cluster, by taking into account effects of dark matter contraction and substructures. By modeling the mass distribution of baryons (stars and gas) around a central bright elliptical galaxy, NGC 1399, and using a modified contraction model motivated by numerical simulations, we show that the dark matter contraction boosts the annihilation signatures by a factor of 4. For dark matter masses around 10 GeV, the upper limit obtained on the annihilation cross section times relative velocity is (σν)∼<(2–3) × 10{sup −25} cm{sup 3} s{sup −1}, which is within a factor of 10 from the value required to explain the dark matter relic density. This effect is more robust than the annihilation boost due to substructure, and it is more important unless the mass of the smallest subhalos is much smaller than that of the Sun.

  4. Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations

    NASA Astrophysics Data System (ADS)

    Rickman, H.; Marchi, S.; A'Hearn, M. F.; Barbieri, C.; El-Maarry, M. R.; Güttler, C.; Ip, W.-H.; Keller, H. U.; Lamy, P.; Marzari, F.; Massironi, M.; Naletto, G.; Pajola, M.; Sierks, H.; Koschny, D.; Rodrigo, R.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Michalik, H.; Sabau, L.; Thomas, N.; Vincent, J.-B.; Wenzel, K.-P.

    2015-11-01

    Context. One of the main aims of the ESA Rosetta mission is to study the origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko at close range. Aims: In this paper we discuss the origin and evolution of comet 67P/Churyumov-Gerasimenko in relation to that of comets in general and in the framework of current solar system formation models. Methods: We use data from the OSIRIS scientific cameras as basic constraints. In particular, we discuss the overall bi-lobate shape and the presence of key geological features, such as layers and fractures. We also treat the problem of collisional evolution of comet nuclei by a particle-in-a-box calculation for an estimate of the probability of survival for 67P/Churyumov-Gerasimenko during the early epochs of the solar system. Results: We argue that the two lobes of the 67P/Churyumov-Gerasimenko nucleus are derived from two distinct objects that have formed a contact binary via a gentle merger. The lobes are separate bodies, though sufficiently similar to have formed in the same environment. An estimate of the collisional rate in the primordial, trans-planetary disk shows that most comets of similar size to 67P/Churyumov-Gerasimenko are likely collisional fragments, although survival of primordial planetesimals cannot be excluded. Conclusions: A collisional origin of the contact binary is suggested, and the low bulk density of the aggregate and abundance of volatile species show that a very gentle merger must have occurred. We thus consider two main scenarios: the primordial accretion of planetesimals, and the re-accretion of fragments after an energetic impact onto a larger parent body. We point to the primordial signatures exhibited by 67P/Churyumov-Gerasimenko and other comet nuclei as critical tests of the collisional evolution.

  5. OBSERVATIONAL CONSTRAINTS ON THE STELLAR RADIATION FIELD IMPINGING ON TRANSITIONAL DISK ATMOSPHERES

    SciTech Connect

    Szulagyi, Judit; Pascucci, Ilaria; Abraham, Peter; Moor, Attila; Apai, Daniel; Bouwman, Jeroen

    2012-11-01

    Mid-infrared atomic and ionic line ratios measured in spectra of pre-main-sequence stars are sensitive indicators of the hardness of the radiation field impinging on the disk surface. We present a low-resolution Spitzer IRS search for [Ar II] at 6.98 {mu}m, [Ne II] at 12.81 {mu}m, and [Ne III] 15.55 {mu}m lines in 56 transitional disks. These objects, characterized by reduced near-infrared but strong far-infrared excess emission, are ideal targets to set constraints on the stellar radiation field onto the disk, because their spectra are not contaminated by shock emission from jets/outflows or by molecular emission lines. After demonstrating that we can detect [Ne II] lines and recover their fluxes from the low-resolution spectra, here we report the first detections of [Ar II] lines toward protoplanetary disks. We did not detect [Ne III] emission in any of our sources. Our [Ne II]/[Ne III] line flux ratios combined with literature data suggest that a soft-EUV or X-ray spectrum produces these gas lines. Furthermore, the [Ar II]/[Ne II] line flux ratios point to a soft X-ray and/or soft-EUV stellar spectrum as the ionization source of the [Ar II] and [Ne II] emitting layer of the disk. If the soft X-ray component dominates over the EUV, then we would expect larger photoevaporation rates and, hence, a reduction of the time available to form planets.

  6. In situ observations of meteor smoke particles (MSP) during the Geminids 2010: constraints on MSP size, work function and composition

    NASA Astrophysics Data System (ADS)

    Rapp, M.; Plane, J. M. C.; Strelnikov, B.; Stober, G.; Ernst, S.; Hedin, J.; Friedrich, M.; Hoppe, U.-P.

    2012-12-01

    We present in situ observations of meteoric smoke particles (MSP) obtained during three sounding rocket flights in December 2010 in the frame of the final campaign of the Norwegian-German ECOMA project (ECOMA = Existence and Charge state Of meteoric smoke particles in the Middle Atmosphere). The flights were conducted before, at the maximum activity, and after the decline of the Geminids which is one of the major meteor showers over the year. Measurements with the ECOMA particle detector yield both profiles of naturally charged particles (Faraday cup measurement) as well as profiles of photoelectrons emitted by the MSPs due to their irradiation by photons of a xenon-flash lamp. The column density of negatively charged MSPs decreased steadily from flight to flight which is in agreement with a corresponding decrease of the sporadic meteor flux recorded during the same period. This implies that the sporadic meteors are a major source of MSPs while the additional influx due to the shower meteors apparently did not play any significant role. Surprisingly, the profiles of photoelectrons are only partly compatible with this observation: while the photoelectron current profiles obtained during the first and third flight of the campaign showed a qualitatively similar behaviour as the MSP charge density data, the profile from the second flight (i.e., at the peak of the Geminids) shows much smaller photoelectron currents. This may tentatively be interpreted as a different MSP composition (and, hence, different photoelectric properties) during this second flight, but at this stage we are not in a position to conclude that there is a cause and effect relation between the Geminids and this observation. Finally, the ECOMA particle detector used during the first and third flight employed three instead of only one xenon flash lamp where each of the three lamps used for one flight had a different window material resulting in different cut off wavelengths for these three lamp types

  7. Simulation of atmospheric N2O with GEOS-Chem and its adjoint: evaluation of observational constraints

    NASA Astrophysics Data System (ADS)

    Wells, K. C.; Millet, D. B.; Bousserez, N.; Henze, D. K.; Chaliyakunnel, S.; Griffis, T. J.; Luan, Y.; Dlugokencky, E. J.; Prinn, R. G.; O'Doherty, S.; Weiss, R. F.; Dutton, G. S.; Elkins, J. W.; Krummel, P. B.; Langenfelds, R.; Steele, L. P.; Kort, E. A.; Wofsy, S. C.; Umezawa, T.

    2015-07-01

    We describe a new 4D-Var inversion framework for N2O based on the GEOS-Chem chemical transport model and its adjoint, and apply this framework in a series of observing system simulation experiments to assess how well N2O sources and sinks can be constrained by the current global observing network. The employed measurement ensemble includes approximately weekly and quasi-continuous N2O measurements (hourly averages used) from several long-term monitoring networks, N2O measurements collected from discrete air samples aboard a commercial aircraft (CARIBIC), and quasi-continuous measurements from an airborne pole-to-pole sampling campaign (HIPPO). For a two-year inversion, we find that the surface and HIPPO observations can accurately resolve a uniform bias in emissions during the first year; CARIBIC data provide a somewhat weaker constraint. Variable emission errors are much more difficult to resolve given the long lifetime of N2O, and major parts of the world lack significant constraints on the seasonal cycle of fluxes. Current observations can largely correct a global bias in the stratospheric sink of N2O if emissions are known, but do not provide information on the temporal and spatial distribution of the sink. However, for the more realistic scenario where source and sink are both uncertain, we find that simultaneously optimizing both would require unrealistically small errors in model transport. Regardless, a bias in the magnitude of the N2O sink would not affect the a posteriori N2O emissions for the two-year timescale used here, given realistic initial conditions, due to the timescale required for stratosphere-troposphere exchange (STE). The same does not apply to model errors in the rate of STE itself, which we show exerts a larger influence on the tropospheric burden of N2O than does the chemical loss rate over short (< 3 year) timescales. We use a stochastic estimate of the inverse Hessian for the inversion to evaluate the spatial resolution of emission

  8. Supersymmetric constraints from B s → μ + μ - and B → K * μ + μ - observables

    NASA Astrophysics Data System (ADS)

    Mahmoudi, F.; Neshatpour, S.; Orloff, J.

    2012-08-01

    We study the implications of the recent LHCb limit and results on B s → μ + μ - and B → K * μ + μ - observables in the constrained SUSY scenarios. After discussing the Standard Model predictions and carefully estimating the theoretical errors, we show the constraining power of these observables in CMSSM and NUHM. The latest limit on BR( B s → μ + μ -), being very close to the SM prediction, constrains strongly the large tan β regime and we show that the various angular observables from B → K * μ + μ - decay can provide complementary information in particular for intermediate tan β values.

  9. Evaluating Observational Constraints on N2O Emissions via Information Content Analysis Using GEOS-Chem and its Adjoint

    NASA Astrophysics Data System (ADS)

    Wells, K. C.; Millet, D. B.; Bousserez, N.; Henze, D. K.; Chaliyakunnel, S.; Griffis, T. J.; Dlugokencky, E. J.; Prinn, R. G.; O'Doherty, S.; Weiss, R. F.; Dutton, G. S.; Elkins, J. W.; Krummel, P. B.; Langenfelds, R. L.; Steele, P.

    2015-12-01

    Nitrous oxide (N2O) is a long-lived greenhouse gas with a global warming potential approximately 300 times that of CO2, and plays a key role in stratospheric ozone depletion. Human perturbation of the nitrogen cycle has led to a rise in atmospheric N2O, but large uncertainties exist in the spatial and temporal distribution of its emissions. Here we employ a 4D-Var inversion framework for N2O based on the GEOS-Chem chemical transport model and its adjoint to derive new constraints on the space-time distribution of global land and ocean N2O fluxes. Based on an ensemble of global surface measurements, we find that emissions are overestimated over Northern Hemisphere land areas and underestimated in the Southern Hemisphere. Assigning these biases to particular land or ocean regions is more difficult given the long lifetime of N2O. To quantitatively evaluate where the current N2O observing network provides local and regional emission constraints, we apply a new, efficient information content analysis technique involving radial basis functions. The technique yields optimal state vector dimensions for N2O source inversions, with model grid cells grouped in space and time according to the resolution that can actually be provided by the network of global observations. We then use these optimal state vectors in an analytical inversion to refine current top-down emission estimates.

  10. Observational Constraints of Red-shift Parametrization Parameters of Dark Energy in Horava-Lifshitz Gravity

    NASA Astrophysics Data System (ADS)

    Biswas, Ritabrata; Debnath, Ujjal

    2015-02-01

    We have assumed that the FRW universe filled with baryonic matter, radiation and dark matter along with dark energy in the frame-work of Horava-Lifshitz gravity. Here three parameterizations like Linear, CPL and JBP for the dark energy have been assumed for the variations of EOS parameter w( z). The observational data analysis by χ 2 minimum test have been analyzed for our models. From Stern, Stern+BAO and Stern+BAO+CMB joint data analysis, we have obtained the bounds of the arbitrary parameters w 0 and w 1. The best fit values of the parameters w 0 and w 1 for these three models and the minimum values of χ 2 have been obtained by observational data analysis. Also the bounds of the parameters w 0 and w 1 are obtained by 66 %, 90 % and 99 % confidence levels for linear, CPL and JBP models. Next red shift-magnitude observational data points from type Ia supernovae have been considered and which contains 557 data points. From this observation, the distance modulus μ( z) against red shift z has been investigated for our predicted theoretical model (three DE models) for the best fit values of the parameters and the observed SNe Ia Union2 data sample. Finally, we have investigated that our predicted theoretical three models permitted the observational data sets.

  11. Additive Routes to Action Learning: Layering Experience Shapes Engagement of the Action Observation Network

    PubMed Central

    Kirsch, Louise P.; Cross, Emily S.

    2015-01-01

    The way in which we perceive others in action is biased by one's prior experience with an observed action. For example, we can have auditory, visual, or motor experience with actions we observe others perform. How action experience via 1, 2, or all 3 of these modalities shapes action perception remains unclear. Here, we combine pre- and post-training functional magnetic resonance imaging measures with a dance training manipulation to address how building experience (from auditory to audiovisual to audiovisual plus motor) with a complex action shapes subsequent action perception. Results indicate that layering experience across these 3 modalities activates a number of sensorimotor cortical regions associated with the action observation network (AON) in such a way that the more modalities through which one experiences an action, the greater the response is within these AON regions during action perception. Moreover, a correlation between left premotor activity and participants' scores for reproducing an action suggests that the better an observer can perform an observed action, the stronger the neural response is. The findings suggest that the number of modalities through which an observer experiences an action impacts AON activity additively, and that premotor cortical activity might serve as an index of embodiment during action observation. PMID:26209850

  12. Experimental model and analytic solution for real-time observation of vehicle's additional steer angle

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolong; Li, Liang; Pan, Deng; Cao, Chengmao; Song, Jian

    2014-03-01

    The current research of real-time observation for vehicle roll steer angle and compliance steer angle(both of them comprehensively referred as the additional steer angle in this paper) mainly employs the linear vehicle dynamic model, in which only the lateral acceleration of vehicle body is considered. The observation accuracy resorting to this method cannot meet the requirements of vehicle real-time stability control, especially under extreme driving conditions. The paper explores the solution resorting to experimental method. Firstly, a multi-body dynamic model of a passenger car is built based on the ADAMS/Car software, whose dynamic accuracy is verified by the same vehicle's roadway test data of steady static circular test. Based on this simulation platform, several influencing factors of additional steer angle under different driving conditions are quantitatively analyzed. Then ɛ-SVR algorithm is employed to build the additional steer angle prediction model, whose input vectors mainly include the sensor information of standard electronic stability control system(ESC). The method of typical slalom tests and FMVSS 126 tests are adopted to make simulation, train model and test model's generalization performance. The test result shows that the influence of lateral acceleration on additional steer angle is maximal (the magnitude up to 1°), followed by the longitudinal acceleration-deceleration and the road wave amplitude (the magnitude up to 0.3°). Moreover, both the prediction accuracy and the calculation real-time of the model can meet the control requirements of ESC. This research expands the accurate observation methods of the additional steer angle under extreme driving conditions.

  13. Constraints on the transient climate response from observed global temperature and ocean heat uptake

    NASA Astrophysics Data System (ADS)

    Knutti, Reto; Tomassini, Lorenzo

    2008-05-01

    Projections of future transient global temperature increase in climate models for a known forcing depend on the strength of the atmospheric feedbacks and the rate of transient ocean heat uptake. A Bayesian framework and an intermediate complexity climate model are used to calculate a probability density function (PDF) of the transient climate response (TCR), constrained by observations of global surface warming and ocean heat uptake. The PDF constrained by observations is wider than the TCR range of current climate models, and has a slightly lower mean. Uncertainties in the observed ocean warming are shown to potentially affect the TCR. It is proposed, however, that even if models were found to overestimate ocean heat uptake, correcting that bias would lead to revisions in surface temperature projections over the twenty-first century that are smaller than the uncertainties introduced by poorly quantified atmospheric feedbacks.

  14. Observations of the Li, Be, and B isotopes and Constraints on Cosmic-ray Propagation

    SciTech Connect

    de Nolfo, Georgia A.; Moskalenko, I.V.; Binns, W.R.; Christian, E.R.; Cummings, A.C.; Davis, A.J.; George, J.S.; Hink, P.L.; Israel, M.H.; Leske, R.A.; Lijowski, M.; Mewaldt, R.A.; Stone, E.C.; Strong, A.W.; von Rosenvinge, T.T.; Wiedenbeck, M.E.; Yanasak, N.E.; /NASA, Goddard /Stanford U., HEPL /Washington U., St. Louis /NASA, Headquarters /Caltech, SRL /Aerospace Corp. /Garching, Max Planck Inst., MPE /Caltech, JPL

    2006-11-15

    The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A {approx}15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

  15. Observations of the Li, Be, and B Isotopes and Constraints on Cosmic-ray Propagation

    NASA Technical Reports Server (NTRS)

    deNolfo, G. A.; Moskalenko, I. V.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; George, J. S.; Hink, P. L.; Israel, M. H.; Leske, R. A.; Lijowski, M.; Mewaldt, R. A.; Stone, E. C.; Strong, A. W.; vonRosenvinge, T. T.; Wiedenbeck, M. E.; Yanasak, N. E.

    2007-01-01

    The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A approx. 15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

  16. Observational constraints on a unified dark matter and dark energy model based on generalized Chaplygin gas

    SciTech Connect

    Park, Chan-Gyung; Hwang, Jai-chan; Park, Jaehong; Noh, Hyerim

    2010-03-15

    We study a generalized version of Chaplygin gas as unified model of dark matter and dark energy. Using realistic theoretical models and the currently available observational data from the age of the universe, the expansion history based on the type Ia supernovae, the matter power spectrum, the cosmic microwave background radiation anisotropy power spectra, and the perturbation growth factor we put the unified model under observational test. As the model has only two free parameters in the flat Friedmann background [{Lambda}CDM (cold dark matter) model has only one free parameter] we show that the model is already tightly constrained by currently available observations. The only parameter space extremely close to the {Lambda}CDM model is allowed in this unified model.

  17. OBSERVATIONAL CONSTRAINTS ON THE MOLECULAR GAS CONTENT IN NEARBY STARBURST DWARF GALAXIES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F.; Dolphin, Andrew E.; Cannon, John M.; Holtzman, Jon

    2012-06-01

    Using star formation histories derived from optically resolved stellar populations in 19 nearby starburst dwarf galaxies observed with the Hubble Space Telescope, we measure the stellar mass surface densities of stars newly formed in the bursts. By assuming a star formation efficiency (SFE), we then calculate the inferred gas surface densities present at the onset of the starbursts. Assuming an SFE of 1%, as is often assumed in normal star-forming galaxies, and assuming that the gas was purely atomic, translates to very high H I surface densities ({approx}10{sup 2}-10{sup 3} M{sub Sun} pc{sup -2}), which are much higher than have been observed in dwarf galaxies. This implies either higher values of SFE in these dwarf starburst galaxies or the presence of significant amounts of H{sub 2} in dwarfs (or both). Raising the assumed SFEs to 10% or greater (in line with observations of more massive starbursts associated with merging galaxies), still results in H I surface densities higher than observed in 10 galaxies. Thus, these observations appear to require that a significant fraction of the gas in these dwarf starbursts galaxies was in the molecular form at the onset of the bursts. Our results imply molecular gas column densities in the range 10{sup 19}-10{sup 21} cm{sup -2} for the sample. In the galaxies where CO observations have been made, these densities correspond to values of the CO-H{sub 2} conversion factor (X{sub CO}) in the range >(3-80) Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, or up to 40 Multiplication-Sign greater than Galactic X{sub CO} values.

  18. Structure and composition of the distant lunar exosphere: Constraints from ARTEMIS observations of ion acceleration in time-varying fields

    NASA Astrophysics Data System (ADS)

    Halekas, J. S.; Poppe, A. R.; Farrell, W. M.; McFadden, J. P.

    2016-06-01

    By analyzing the trajectories of ionized constituents of the lunar exosphere in time-varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two-probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time-dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes ~3000-5000 km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40 amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

  19. Additional Arctic observations improve weather and sea-ice forecasts for the Northern Sea Route

    PubMed Central

    Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime

    2015-01-01

    During ice-free periods, the Northern Sea Route (NSR) could be an attractive shipping route. The decline in Arctic sea-ice extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of sea ice could make ship navigation along the NSR difficult. Accurate forecasts of weather and sea ice are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and sea-ice forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The sea-ice forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven sea-ice advection along the NSR. PMID:26585690

  20. Additional Arctic observations improve weather and sea-ice forecasts for the Northern Sea Route

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime

    2015-11-01

    During ice-free periods, the Northern Sea Route (NSR) could be an attractive shipping route. The decline in Arctic sea-ice extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of sea ice could make ship navigation along the NSR difficult. Accurate forecasts of weather and sea ice are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and sea-ice forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The sea-ice forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven sea-ice advection along the NSR.

  1. Additional Arctic observations improve weather and sea-ice forecasts for the Northern Sea Route.

    PubMed

    Inoue, Jun; Yamazaki, Akira; Ono, Jun; Dethloff, Klaus; Maturilli, Marion; Neuber, Roland; Edwards, Patti; Yamaguchi, Hajime

    2015-01-01

    During ice-free periods, the Northern Sea Route (NSR) could be an attractive shipping route. The decline in Arctic sea-ice extent, however, could be associated with an increase in the frequency of the causes of severe weather phenomena, and high wind-driven waves and the advection of sea ice could make ship navigation along the NSR difficult. Accurate forecasts of weather and sea ice are desirable for safe navigation, but large uncertainties exist in current forecasts, partly owing to the sparse observational network over the Arctic Ocean. Here, we show that the incorporation of additional Arctic observations improves the initial analysis and enhances the skill of weather and sea-ice forecasts, the application of which has socioeconomic benefits. Comparison of 63-member ensemble atmospheric forecasts, using different initial data sets, revealed that additional Arctic radiosonde observations were useful for predicting a persistent strong wind event. The sea-ice forecast, initialised by the wind fields that included the effects of the observations, skilfully predicted rapid wind-driven sea-ice advection along the NSR. PMID:26585690

  2. A Practical Solution to Optimizing the Reliability of Teaching Observation Measures under Budget Constraints

    ERIC Educational Resources Information Center

    Meyer, J. Patrick; Liu, Xiang; Mashburn, Andrew J.

    2014-01-01

    Researchers often use generalizability theory to estimate relative error variance and reliability in teaching observation measures. They also use it to plan future studies and design the best possible measurement procedures. However, designing the best possible measurement procedure comes at a cost, and researchers must stay within their budget…

  3. Observational constraints on the nature of low redshift Lyα absorbers.

    NASA Astrophysics Data System (ADS)

    Le Brun, V.; Bergeron, J.; Boisse, P.

    1996-02-01

    We present results from a spectroscopic and imaging survey of galaxies in the fields of quasars from the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. The aim of this survey is to identify galaxies within 3.5' from the quasar sightline, to a limiting, integrated r-band magnitude m_r_=22.5. The data are then compared to the HST homogeneous sample of Lyα-only absorbers in order to put constraints on the nature of these absorbers, and in particular on their relation to galaxies. We have obtained spectra for 81 objects in three quasar fields and identified 66 galaxies (success rate of 81%) at redshifts in the range z=0.0500-0.7974, and at linear impact parameters to the quasar sightlines spanning D=57-2380h_50_^-1^kpc. Among these galaxies, 19 are at less than 750km/s from a Lyα absorber, and only one clearly does not give rise to any absorption. Three other galaxies are at the redshifts of metal-rich absorption systems, of which one belongs to a cluster with altogether 19 identified galaxies at the quasar redshift. The analysis of our sample combined with those of previous studies shows that: 1) the redshift agreements of the Lyα absorber-galaxy associations cannot be due to chance coincidence; 2) there is no clear anti-correlation between the Lyα rest-frame equivalent width and the impact parameter for the whole sample (w_r, min_=0.10A). When only the strongest lines are considered (w_r_>=0.24A), w_r_(Lyα) and D are marginally anti-correlated. Lanzetta et al. (1995) found a stronger anti-correlation which could be due, at least in part, to the existence of metal-rich absorbers in their sample. Our results suggest that most Lyα absorbers are not gaseous clouds that belong in a strict sense to galaxies, as is the case for MgII absorbers. The size of Lyα galactic halos can be inferred from the variation with D of the fraction of associations to the total number of galaxies at impact parameters < D. This fraction drops from 1 to ~0.65 at D~200h

  4. VLBA AND CHANDRA OBSERVATIONS OF JETS IN FRI RADIO GALAXIES: CONSTRAINTS ON JET EVOLUTION

    SciTech Connect

    Kharb, P.; O'Dea, C. P.; Tilak, A.; Baum, S. A.; Haynes, E.; Noel-Storr, J.; Fallon, C.; Christiansen, K.

    2012-07-20

    We present here the results from new Very Long Baseline Array (VLBA) observations at 1.6 and 5 GHz of 19 galaxies of a complete sample of 21 Uppasala General Catalog (UGC) Fanaroff-Riley type I (FRI) radio galaxies. New Chandra data of two sources, viz., UGC 00408 and UGC 08433, are combined with the Chandra archival data of 13 sources. The 5 GHz observations of 10 'core-jet' sources are polarization-sensitive, while the 1.6 GHz observations constitute second-epoch total intensity observations of nine 'core-only' sources. Polarized emission is detected in the jets of seven sources at 5 GHz, but the cores are essentially unpolarized, except in M87. Polarization is detected at the jet edges in several sources, and the inferred magnetic field is primarily aligned with the jet direction. This could be indicative of magnetic field 'shearing' due to jet-medium interaction, or the presence of helical magnetic fields. The jet peak intensity I{sub {nu}} falls with distance d from the core, following the relation, I{sub {nu}}{proportional_to}d{sup a} , where a is typically {approx} - 1.5. Assuming that adiabatic expansion losses are primarily responsible for the jet intensity 'dimming,' two limiting cases are considered: (1) the jet has a constant speed on parsec scales and is expanding gradually such that the jet radius r{proportional_to}d 0{sup .4}; this expansion is, however, unobservable in the laterally unresolved jets at 5 GHz, and (2) the jet is cylindrical and is accelerating on parsec scales. Accelerating parsec-scale jets are consistent with the phenomenon of 'magnetic driving' in Poynting-flux-dominated jets. While slow jet expansion as predicted by case (1) is indeed observed in a few sources from the literature that are resolved laterally, on scales of tens or hundreds of parsecs, case (2) cannot be ruled out in the present data, provided the jets become conical on scales larger than those probed by VLBA. Chandra observations of 15 UGC FRIs detect X-ray jets in

  5. BeppoSAX Observation of NGC 7582: Constraints on the X-Ray Absorber

    NASA Technical Reports Server (NTRS)

    Turner, T. J.; Fiore, F.; Perola, G. C.; Matt, G.; George, I. M.; Piro, L.; Bassani, L.

    1999-01-01

    This paper presents a BeppoSAX observation of NGC 7582 made during 1998 November and an optical spectrum taken in 1998 October. The new X-ray data reveal a previously unknown hard X-ray component in NGC 7582, peaking close to 20 keV. Rapid variability is observed with correlated changes in the 5-10 and 13-60 keV bands indicating that a single continuum component, produced by the active nucleus, provides the, dominant flux across both bands. Comparison between RXTE and BeppoSAX data reveals changes in the 2 - 10 keV flux on timescales of months. Changes in the nuclear X-ray flux appear unrelated to the gradual decline in optical flux noted since the high-state in 1998 July. The 0.5 - 2 keV flux of NGC 7582 is not significantly variable within the BeppoSAX observation, but has brightened by a factor of approximately 2 since the ASCA observation of 1994. While there is some concern about contamination from spatially-unresolved sources, the long-term variability in soft X-ray flux seems most likely associated with the nucleus or an event within the host galaxy of NGC 7582. The 2 - 100 keV spectrum is well fit by a powerlaw of photon index Gamma = 1.95(sup +0.09, sub -0.18) steeper by Delta.Gamma approximately equal 0.40 than the index during the 1994 ASCA observation. The X-ray continuum is attenuated by a thick absorber of N(H) approximately 1.6 x10(exp 24)/sq cm covering approximately 60(sup +10%, sub -14%) of the nucleus plus a screen with N(sub H) approximately 1.4 x 10(exp 23)/ sq cm covering the entire nucleus. Comparison of the BeppoSAX and ASCA spectra shows an increase in the full screen by Delta.N(sub H) approximately equal 7 x 10(exp 22)/sq cm since 1994, confirming the absorption variability found by Xue et al. The increase in soft X-ray flux between 1994 and 1998 is consistent with the appearance of holes in the full screen allowing approximately < 1% of the nuclear flux to escape, and producing some clear lines-of-sight to the broad-line-region. The data

  6. Overall observational constraints on the running parameter λ of Hořava-Lifshitz gravity

    SciTech Connect

    Dutta, Sourish; Saridakis, Emmanuel N. E-mail: msaridak@phys.uoa.gr

    2010-05-01

    We use observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB), along with requirements of Big Bang Nucleosynthesis (BBN), to constrain the running parameter λ of Hořava-Lifshitz gravity, which determines the flow between the Ultra-Violet and the Infra-Red. We consider both the detailed and non-detailed balance versions of the gravitational sector, and we include the matter and radiation sectors. Allowing for variation of all the parameters of the theory, we construct the likelihood contours and we conclude that in 1σ confidence λ is restricted to |λ−1|∼<0.02, while its best fit value is |λ{sub b.f}−1| ≈ 0.002. Although this observational analysis restricts the running parameter λ very close to its IR value 1, it does not enlighten the discussion about the theory's possible conceptual and theoretical problems.

  7. Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations

    NASA Technical Reports Server (NTRS)

    Zimmer, Christophe; Khurana, Krishan K.; Kivelson, Margaret G.

    2000-01-01

    Galileo measured the magnetic field perturbations of Europa and Callisto, which are consistent with dipole fields created by temporal variations of the surrounding jovian magnetospheric field. These fields almost match those expected for perfectly conducting moons. Using a simple shell model, we analyze the implications of these observations for the electrical structure for the interiors of the moons. It is discovered that Europa and Callisto must possess areas where the conductivity exceeds 0.06 and 0.02 S/m at a depth of no more than 200 and 300 km below the surface, respectively. This conductivity is not attainable in ice or silicates, unless large temperature gradients can be maintained below the ice or the ice layer is at least partially molten. A cloud of pick-up ions or an ionosphere are probably insufficiently conductive. Global Earth-like oceans under the surface of both moons could explain the observations if they are at least a few kilometers thick.

  8. Onset Times of Solar Particle Events Observed by MSL/RAD - Constraints on Particle Transport

    NASA Astrophysics Data System (ADS)

    Wimmer-Schweingruber, R. F.; Hassler, D. M.; Boettcher, S.; Martin, C.; Zeitlin, C.; Brinza, D.; Koehler, J.; Guo, J.; Posner, A.; Appel, J.

    2012-12-01

    En route to Mars, Mars Science Laboratory's (MSL's) Radiation Assessment Detector (RAD) was already operational and observed a number of solar particle events. These were also seen by an array of spacecraft in the heliosphere. This constellation provides an unique opportunity to investigate particle propagation in the ecliptic plane and thus constrain particle propagation models. RAD measures energetic ions up to approximately 100 MeV/nuc, but was buried deep inside the Mars Science Laboratory (MSL). Due to the significant shielding provided by the MSL cruise stage, back-shell, heat shield, and skycrane, RAD was sensitive to particles in a significantly higher and somewhat uncertain energy range. Even behind the aforementioned shielding, onset times of particle events can be clearly identified. In this work, we will provide them for the particle events observed by RAD in 2012. We will also relate them to other data and solar/interplanetary acceleration sites.

  9. Observational constraints of stellar collapse: Diagnostic probes of nature's extreme matter experiment

    SciTech Connect

    Fryer, Chris L. Even, Wesley; Grefenstette, Brian W.; Wong, Tsing-Wai

    2014-04-15

    Supernovae are Nature's high-energy, high density laboratory experiments, reaching densities in excess of nuclear densities and temperatures above 10 MeV. Astronomers have built up a suite of diagnostics to study these supernovae. If we can utilize these diagnostics, and tie them together with a theoretical understanding of supernova physics, we can use these cosmic explosions to study the nature of matter at these extreme densities and temperatures. Capitalizing on these diagnostics will require understanding a wide range of additional physics. Here we review the diagnostics and the physics neeeded to use them to learn about the supernova engine, and ultimate nuclear physics.

  10. Observational constraints on neutron star crust-core coupling during glitches

    NASA Astrophysics Data System (ADS)

    Newton, W. G.; Berger, S.; Haskell, B.

    2015-12-01

    We demonstrate that observations of glitches in the Vela pulsar can be used to investigate the strength of the crust-core coupling in a neutron star and provide a powerful probe of the internal structure of neutron stars. We assume that glitch recovery is dominated by the torque exerted by the mutual friction-mediated recoupling of superfluid components of the core that were decoupled from the crust during the glitch. Then we use the observations of the recoveries from two recent glitches in the Vela pulsar to infer the fraction of the core that is coupled to the crust during the glitch. We then analyse whether crustal neutrons alone are sufficient to drive glitches in the Vela pulsar, taking into account crustal entrainment. We use two sets of neutron star equations of state (EOSs) which span crust and core consistently and cover a conservative range of the slope of the symmetry energy at saturation density 30 < L < 120 MeV. The two sets differ in the stiffness of the high density EOS. We find that for medium to stiff EOSs, observations imply >70 per cent of the moment of inertia of the core is coupled to the crust during the glitch, though for softer EOSs L ≈ 30 MeV as little as 5 per cent could be coupled. We find that only by extending the region where superfluid vortices are strongly pinned into the core by densities at least 0.016 fm-3 above the crust-core transition density does any EOS reproduce the observed glitch activity.

  11. Constraints on the Mid-Continent Deformation Gravity Gradient Determined from Co-located GPS and Absolute Gravity Observations

    NASA Astrophysics Data System (ADS)

    James, T. S.; Mazzotti, S.; Mazzotti, S.; Lambert, A.

    2001-12-01

    The deformation gravity gradient (DGG) is the ratio of the time rate of change of surface gravity to vertical crustal velocity. Different processes generate different theoretical predictions of the DGG. Consequently, observational constraints on the DGG are necessary to link crustal uplift observations to satellite-derived observations of the time rate of change of the Earth's gravitational field, which will be generated by upcoming satellite missions such as GRACE. Larson and van Dam (2000) have compared secular gravity trends from 4 sites in interior North America to crustal uplift rates obtained from global point-positioning analyses of GPS observations, and found they agree, assuming a nominal DGG value appropriate to postglacial rebound of -0.15 μ Gal/mm (Wahr et al., 1995). Here we revisit and extend their analysis in order to determine the observational constraints on the DGG in mid-continent North America. We use recently published gravity rates derived from significantly more absolute gravity observations and a different GPS analysis scheme. Lambert et al. (2001) have published secular gravity rates for 7 sites in mid-continent North America, using all available absolute gravity observations and allowing for instrumental offsets. The sites, chosen to sample postglacial rebound, lie on a transect from Churchill, Manitoba, located on Hudson Bay, to North Liberty, Iowa. Four of these sites (Churchill, Flin Flon, Lac du Bonnet, and North Liberty) also feature a nearby GPS station. The GPS observations were analyzed using double differencing with Bernese 4.2, yielding 5 year time series for vertical position. The daily repeatabilities of 5 to 9 mm compare well to the weekly repeatabilities of 7-8 mm reported by Larson and van Dam (2000). A comparison of the vertical rates derived from these time series to the secular solid-surface gravity trends finds a DGG of -0.14 +/- 0.06 μ Gal/mm. This value is in good agreement with model predictions for postglacial

  12. Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations

    NASA Astrophysics Data System (ADS)

    Paulot, F.; Jacob, D. J.; Johnson, M. T.; Bell, T. G.; Baker, A. R.; Keene, W. C.; Lima, I. D.; Doney, S. C.; Stock, C. A.

    2015-08-01

    Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a-1, much lower than current literature values (7-23 TgN a-1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a-1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2-5 TgN a-1, comparable in magnitude to other natural sources from open fires and soils.

  13. Constraints on common envelope magnetic fields from observations of jets in planetary nebulae

    NASA Astrophysics Data System (ADS)

    Tocknell, James; De Marco, Orsola; Wardle, Mark

    2014-04-01

    The common envelope (CE) interaction describes the swallowing of a nearby companion by a growing, evolving star. CEs that take place during the asymptotic giant branch phase of the primary may lead to the formation of a planetary nebula (PN) with a post-CE close binary in the middle. We have used published observations of masses and kinematics of jets in four post-CE PN to infer physical characteristics of the CE interaction. In three of the four systems studied, Abell 63, ETHOS 1 and the Necklace PN, the kinematics indicate that the jets were launched a few thousand years before the CE and we favour a scenario where this happened before Roche lobe overflow, although better models of wind accretion and wind Roche lobe overflow are needed. The magnetic fields inferred to launch pre-CE jets are of the order of a few gauss. In the fourth case, NGC 6778, the kinematics indicate that the jets were launched about 3000 yr after the CE interaction. Magnetic fields of the order of a few hundreds to a few thousands gauss are inferred in this case, approximately in line with predictions of post-CE magnetic fields. However, we remark that in the case of this system, we have not been able to find a reasonable scenario for the formation of the two jet pairs observed: the small orbital separation may preclude the formation of even one accretion disc able to supply the necessary accretion rate to cause the observed jets.

  14. Constraints on the flux of Ultra-High Energy neutrinos from WSRT observations

    SciTech Connect

    Scholten, O; Bacelar, J; Braun, R; de Bruyn, A G; Falcke, H; Singh, K; Stappers, B; Strom, R G; al Yahyaoui, R

    2010-04-02

    Context. Ultra-high energy (UHE) neutrinos and cosmic rays initiate particle cascades underneath the Moon's surface. These cascades have a negative charge excess and radiate Cherenkov radio emission in a process known as the Askaryan effect. The optimal frequency window for observation of these pulses with radio telescopes on the Earth is around 150 MHz. Aims. By observing the Moon with the Westerbork Synthesis Radio Telescope array we are able to set a new limit on the UHEneutrino flux. Methods. The PuMa II backend is used to monitor the Moon in 4 frequency bands between 113 and 175 MHz with a sampling frequency of 40 MHz. The narrow band radio interference is digitally filtered out and the dispersive effect of the Earth?s ionosphere is compensated for. A trigger system is implemented to search for short pulses. By inserting simulated pulses in the raw data, the detection efficiency for pulses of various strength is calculated. Results. With 47.6 hours of observation time, we are able to set a limit on the UHE neutrino flux. This new limit is an order of magnitude lower than existing limits. In the near future, the digital radio array LOFAR will be used to achieve an even lower limit.

  15. Constraints on the flux of ultra-high energy neutrinos from Westerbork Synthesis Radio Telescope observations

    NASA Astrophysics Data System (ADS)

    Buitink, S.; Scholten, O.; Bacelar, J.; Braun, R.; de Bruyn, A. G.; Falcke, H.; Singh, K.; Stappers, B.; Strom, R. G.; Yahyaoui, R. Al

    2010-10-01

    Context. Ultra-high energy (UHE) neutrinos and cosmic rays initiate particle cascades underneath the Moon's surface. These cascades have a negative charge excess and radiate Cherenkov radio emission in a process known as the Askaryan effect. The optimal frequency window for observation of these pulses with radio telescopes on the Earth is around 150 MHz. Aims: By observing the Moon with the Westerbork Synthesis Radio Telescope array we are able to set a new limit on the UHE neutrino flux. Methods: The PuMa II backend is used to monitor the Moon in 4 frequency bands between 113 and 175 MHz with a sampling frequency of 40 MHz. The narrowband radio interference is digitally filtered out and the dispersive effect of the Earth's ionosphere is compensated for. A trigger system is implemented to search for short pulses. By inserting simulated pulses in the raw data, the detection efficiency for pulses of various strength is calculated. Results: With 47.6 hours of observation time, we are able to set a limit on the UHE neutrino flux. This new limit is an order of magnitude lower than existing limits. In the near future, the digital radio array LOFAR will be used to achieve an even lower limit.

  16. Observational Constraints on the Orbit and Location of Planet Nine in the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Brown, Michael E.; Batygin, Konstantin

    2016-06-01

    We use an extensive suite of numerical simulations to constrain the mass and orbit of Planet Nine, the recently proposed perturber in a distant eccentric orbit in the outer solar system. We compare our simulations to the observed population of aligned eccentric high semimajor axis Kuiper belt objects (KBOs) and determine which simulation parameters are statistically compatible with the observations. We find that only a narrow range of orbital elements can reproduce the observations. In particular, the combination of semimajor axis, eccentricity, and mass of Planet Nine strongly dictates the semimajor axis range of the orbital confinement of the distant eccentric KBOs. Allowed orbits, which confine KBOs with semimajor axis beyond 380 au, have perihelia roughly between 150 and 350 au, semimajor axes between 380 and 980 au, and masses between 5 and 20 Earth masses. Orbitally confined objects also generally have orbital planes similar to that of the planet, suggesting that the planet is inclined approximately 30°to the ecliptic. We compare the allowed orbital positions and estimated brightness of Planet Nine to previous and ongoing surveys which would be sensitive to the planet’s detection and use these surveys to rule out approximately two-thirds of the planet’s orbit. Planet Nine is likely near aphelion with an approximate brightness of 22\\lt V\\lt 25. At opposition, its motion, mainly due to parallax, can easily be detected within 24 hours.

  17. Operator constraints for twist-3 functions and Lorentz invariance properties of twist-3 observables

    DOE PAGESBeta

    Kanazawa, Koichi; Pitonyak, Daniel; Koike, Yuji; Metz, Andreas; Schlegel, Marc

    2016-03-14

    We investigate the behavior under Lorentz transformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, a priori, acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on light cone vectors which are introduced by the twist-3 factorization formulas and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relationsmore » for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the light cone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, ℓN→hX. Furthermore, with the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.« less

  18. Electron Energy Distributions at Relativistic Shock Sites: Observational Constraints from the Cygnus A Hotspots

    SciTech Connect

    Cheung, C.C.Teddy; Stawarz, L.; Harris, D.E.; Ostrowski, M.

    2007-10-15

    We report new detections of the hotspots in Cygnus A at 4.5 and 8.0 microns with the Spitzer Space Telescope. Together with detailed published radio observations and synchrotron self-Compton modeling of previous X-ray detections, we reconstruct the underlying electron energy spectra of the two brightest hotspots (A and D). The low-energy portion of the electron distributions have flat power-law slopes (s {approx} 1.5) up to the break energy which corresponds almost exactly to the mass ratio between protons and electrons; we argue that these features are most likely intrinsic rather than due to absorption effects. Beyond the break, the electron spectra continue to higher energies with very steep slopes s>3. Thus, there is no evidence for the 'canonical' s=2 slope expected in 1st order Fermi-type shocks within the whole observable electron energy range. We discuss the significance of these observations and the insight offered into high-energy particle acceleration processes in mildly relativistic shocks.

  19. Operator constraints for twist-3 functions and Lorentz invariance properties of twist-3 observables

    NASA Astrophysics Data System (ADS)

    Kanazawa, Koichi; Koike, Yuji; Metz, Andreas; Pitonyak, Daniel; Schlegel, Marc

    2016-03-01

    We investigate the behavior under Lorentz transformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, a priori, acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on light cone vectors which are introduced by the twist-3 factorization formulas and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relations for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the light cone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, ℓN →h X . With the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.

  20. Constraints on the progenitor system and the environs of SN 2014J from deep radio observations

    SciTech Connect

    Pérez-Torres, M. A.; Alberdi, A.; Beswick, R. J.; Muxlow, T. W. B.; Argo, M. K.; Paragi, Z.; Ryder, S.; Marcaide, J. M.; Ros, E.; Guirado, J. C.; Martí-Vidal, I.

    2014-09-01

    We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By combining data and a proper modeling of the radio emission, we constrain the mass-loss rate from the progenitor system of SN 2014J to M-dot ≲7.0×10{sup −10} M{sub ⊙} yr{sup −1} (for a wind speed of 100 km s{sup –1}). If the medium around the supernova is uniform, then n {sub ISM} ≲ 1.3 cm{sup –3}, which is the most stringent limit for the (uniform) density around a Type Ia SN. Our deep upper limits favor a double-degenerate (DD) scenario—involving two WD stars—for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate (SD) scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to an exploding WD, are ruled out by our observations. (While completing our work, we noticed that a paper by Margutti et al. was submitted to The Astrophysical Journal. From a non-detection of X-ray emission from SN 2014J, the authors obtain limits of M-dot ≲1.2×10{sup −9} M {sub ☉} yr{sup –1} (for a wind speed of 100 km s{sup –1}) and n {sub ISM} ≲ 3.5 cm{sup –3}, for the ρ∝r {sup –2} wind and constant density cases, respectively. As these limits are less constraining than ours, the findings by Margutti et al. do not alter our conclusions. The X-ray results are, however, important to rule out free-free and synchrotron self-absorption as a reason for the radio non-detections.) Our estimates on the limits on the gas density surrounding SN2011fe, using the flux density limits from Chomiuk et al., agree well with their results. Although we discuss the possibilities of an SD scenario passing observational tests, as well as uncertainties in the modeling of the radio emission, the

  1. XMM-Newton Observations of MBM 12: More Constraints on the Solar Wind Charge Exchange and Local Bubble Emissions

    NASA Technical Reports Server (NTRS)

    Koutroumpa, Dimitra; Smith, Randall K.; Edgar, Richard J.; Kuntz, Kip D.; Plucinsky, Paul P.; Snowden, Steven L.

    2010-01-01

    We present the first analysis of an XMM-Newton observation of the nearby molecular cloud MBM 12. We find that in the direction of MBM 12 the total O VII (0.57 keV) triplet emission is 1.8(+0.5/-0.6) photons/sq cm/s/sr (or Line Units - LU) while for the O VIII (0.65 keV) line emission we find a 3(sigma) upper limit of <1 LU. We also use a heliospheric model to calculate the O VII and O VIII emission generated by Solar Wind Charge-eXchange (SWCX) which we compare to the XMM-Newton observations. This comparison provides new constraints on the relative heliospheric and Local Bubble contributions to the local diffuse X-ray background. The heliospheric SWCX model predicts 0.82 LU for O VII, which accounts for approx. 46+/-15% of the observed value, and 0.33 LU for the O VIII line emission consistent with the XMM-Newton observed value. We discuss our results in combination with previous observations of the MBM 12 with CHANDRA and Suzaku.

  2. XMM-NEWTON OBSERVATIONS OF MBM 12: MORE CONSTRAINTS ON THE SOLAR WIND CHARGE EXCHANGE AND LOCAL BUBBLE EMISSIONS

    SciTech Connect

    Koutroumpa, Dimitra; Snowden, Steven L.; Kuntz, Kip D.

    2011-01-10

    We present the first analysis of an XMM-Newton observation of the nearby molecular cloud MBM 12. We find that in the direction of MBM 12 the total O VII (0.57 keV) triplet emission is 1.8{sup +0.5}{sub -0.6} photons cm{sup -2} s{sup -1} sr{sup -1} (or line units, LU) while for the O VIII (0.65 keV) line emission we find a 3{sigma} upper limit of <1 LU. We use a heliospheric model to calculate the O VII and O VIII emission generated by Solar Wind Charge-eXchange (SWCX) which we compare to the XMM-Newton observations. This comparison provides new constraints on the relative heliospheric and Local Bubble contributions to the local diffuse X-ray background. The heliospheric SWCX model predicts 0.82 LU for O VII, which accounts for {approx}46% {+-} 15% of the observed value, and 0.33 LU for the O VIII line emission consistent with the XMM-Newton observed value. We discuss our results in combination with previous observations of MBM 12 with Chandra and Suzaku.

  3. Redshift parametrizations of dark energy and observational constraint on their parameters: Galileon gravity as background

    NASA Astrophysics Data System (ADS)

    Rudra, Prabir; Ranjit, Chayan; Kundu, Sujata

    2015-08-01

    In this work, Friedmann-Robertson-Walker (FRW) universe filled with dark matter (DM) (perfect fluid with negligible pressure) along with dark energy (DE) in the background of Galileon gravity is considered. Four DE models with different equation of state (EoS) parametrizations have been employed namely, linear, Chevallier-Polarski-Lindler (CPL), Jassal-Bagla-Padmanabhan (JBP) and logarithmic parametrizations. From Stern, Stern+Baryonic Acoustic Oscillation (BAO) and Stern+BAO+Cosmic Microwave Background (CMB) joint data analysis, we have obtained the bounds of the arbitrary parameters ω0 and ω1 by minimizing the χ2 test. The best fit values and bounds of the parameters are obtained at 66%, 90% and 99% confidence levels which are shown by closed confidence contours in the figures. For the logarithmic model unbounded confidence contours are obtained and hence the model parameters could not be finitely constrained. The distance modulus μ(z) against redshift z has also been plotted for our predicted theoretical models for the best fit values of the parameters and compared with the observed Union2 data sample and SNe Type Ia 292 data and we have shown that our predicted theoretical models permits the observational datasets. From the data fitting it is seen that at lower redshifts (z < 0.3) the SNe Type Ia 292 data gives a better fit with our theoretical models compared to the Union2 data sample. So, from the data analysis, SNe Type Ia 292 data is the more favored data sample over its counterpart given the present choice of free parameters. From the study, it is also seen that the logarithmic parametrization model is less supported by the observational data. Finally, we have generated the plot for the deceleration parameter against the redshift parameter for all the theoretical models and compared the results with the work of Farooq et al., (2013).

  4. Observational constraints on the efficiency of dehydration mechanisms in the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Rollins, A. W.; Thornberry, T. D.; Gao, R. S.; Woods, S.; Lawson, R. P.; Bui, T. P.; Jensen, E. J.; Fahey, D. W.

    2016-03-01

    The efficiency of dehydration in the tropical tropopause layer (TTL) determines how closely water vapor will be reduced to the lowest saturation mixing ratio encountered along a trajectory to the stratosphere, thereby strongly influencing stratospheric humidity. The NASA Airborne Tropical Tropopause Experiment (ATTREX) provided an unprecedented number and quality of in situ observations to constrain the key mechanisms controlling this dehydration. Statistical analyses of the ATTREX data show that nucleation, growth, and sedimentation each result in TTL dehydration becoming increasingly inefficient at temperatures below 200 K. Because of these inefficiencies, models that ignore these mechanisms likely underestimate water vapor at the stratospheric entry point by ~10-20% at the lowest temperatures.

  5. New constraints on the motion of the Fairweather fault, Alaska, from GPS observations

    NASA Astrophysics Data System (ADS)

    Fletcher, Hilary J.; Freymueller, Jeffrey T.

    2003-02-01

    GPS velocities from sites near to the Fairweather fault in southern Alaska are combined with line length data from geodetic surveys by the U. S. Geological Survey (USGS) to estimate the slip rate and locking depth of the Fairweather fault using dislocation theory. We perform a weighted least-squares inversion of the geodetic data and obtain a best-fitting slip rate of 45.6 +/- 2.0 mm/yr and locking depth of 9.0 +/- 0.8 km. The slip rate we estimate is one of the highest observed across any strike slip fault. We also include the Dalton Creek segment of the Denali fault in our model and estimate a slip rate of 3.8 +/- 1.4 mm/yr for this section of the fault. This is substantially lower than the rate observed for the Denali fault segment to the northwest, which ruptured in the November 3, 2002 MW 7.9 Denali fault earthquake.

  6. New constraints on the CH4 vertical profile in Uranus and Neptune from Herschel observations

    NASA Astrophysics Data System (ADS)

    Lellouch, E.; Moreno, R.; Orton, G. S.; Feuchtgruber, H.; Cavalié, T.; Moses, J. I.; Hartogh, P.; Jarchow, C.; Sagawa, H.

    2015-07-01

    Dedicated line observations of CH4 rotational lines performed with Herschel/PACS and HIFI in 2009-2011 provide new inferences of the mean methane profile in the upper tropospheres and stratospheres of Uranus and Neptune. At Uranus, CH4 is found to be near saturation, with a ~9 × 10-4 tropopause/lower stratosphere mole fraction. This is nominally six times larger than inferred from Spitzer in 2007, although reconciliation may be possible if the CH4 abundance decreases sharply from ~100 to 2 mbar. This unexpected situation might reflect heterogeneous conditions in Uranus' stratosphere, with local CH4 depletions and heating associated with downwelling motions. Higher CH4 abundances compared to values inferred under solstitial conditions by Voyager in 1989 suggest that atmospheric mixing is effectively subdued at high latitudes and/or is time-variable. At Neptune, the mid-stratosphere CH4 abundance is (1.15 ± 0.10) × 10-3, in agreement with earlier determinations and indicative of either leakage through a warmer polar region or upwelling at low or middle latitudes. On both planets, spatially resolved observations of temperature and methane in the stratosphere are needed to further identify the physical processes at work. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  7. Observational constraints on the atmospheres of Uranus and Neptune from new measurements near 10 micrometers

    SciTech Connect

    Tokunaga, A.T.; Caldwell, J.

    1983-10-01

    Uranus was detected at 10.3, 11.6 and 12.5 micrometers approximately 1 micrometer spectral bandpasses, with respective brightness temperatures of 74.0 + 0.9 or -1.1, 67.6 + 0.5 or -0.7, and 65.5 + 0.6 or -0.7 K and the first detection of Neptune at 10.3 micrometers with a brightness temperature of 77.5 + 0.7 or -0.9 K. We also detected Neptune at 11.36 micrometers with 2 percent spectral resolution at 81.0 + 0.8 or -0.9 K. The 10 micrometers continuous of both Uranus and Neptune may in part be due to reflected solar radiation as well as thermal emission. If all of the observed flux is reflected light, then the maximum geometric albedo of Uranus is 0.115 + or - 0.020, and that of Neptune is 0.229 + or - 0.043. In the context of previous observations in this region, the maximum stratospheric C2H6 mixing ratio is found to be 3 x 10 to the -8 power for Uranus and 3 x 10 to the -6 power for Neptune. A value for the maximum mixing ratio in the stratosphere of Neptune on the order of 1 - 0.004 appears to be consistent with the available data. Previously announced in STAR as N83-29155.

  8. Observational constraints on the atmospheres of Uranus and Neptune from new measurements near 10 micron

    SciTech Connect

    Orton, G.S.; Tokunaga, A.T.

    1982-01-01

    Uranus was detected at 10.3, 11.6 and 12.5 micrometers approximately 1 micrometer spectral bandpasses, with respective brightness temperatures of 74.0 + 0.9 or -1.1, 67.6 + 0.5 or -0.7, and 65.5 + 0.6 or -0.7 K and the first detection of Neptune at 10.3 micrometers with a brightness temperature of 77.5 + 0.7 or -0.9 K. We also detected Neptune at 11.36 micrometers with 2% spectral resolution at 81.0 + 0.8 or -0.9 K. The 10 micrometers continuous of both Uranus and Neptune may in part be due to reflected solar radiation as well as thermal emission. If all of the observed flux is reflected light, then the maximum geometric albedo of Uranus is 0.115 + or - 0.020, and that of Neptune is 0.229 + or - 0.043. In the context of previous observations in this region, the maximum stratospheric C2H6 mixing ratio is found to be 3 x 10 to the -8 power for Uranus and 3 x 10 to the -6 power for Neptune. A value for the maximum mixing ratio in the stratosphere of Neptune on the order of 1 - 0.004 appears to be consistent with the available data.

  9. Observational and theoretical constraints for an Hα-halo around the Crab nebula

    NASA Astrophysics Data System (ADS)

    Tziamtzis, A.; Schirmer, M.; Lundqvist, P.; Sollerman, J.

    2009-04-01

    Aims: We searched for a fast moving Hα shell around the Crab nebula. Such a shell could account for this supernova remnant's missing mass, and carry enough kinetic energy to make SN 1054 a normal type II event. Methods: Deep Hα images were obtained with WFI at the 2.2 m MPG/ESO telescope and with MOSCA at the 2.56 m NOT. The data are compared with theoretical expectations derived from shell models with ballistic gas motion, constant temperature, constant degree of ionisation, and a power law for the density profile. Results: We reach a surface brightness limit of 5 × 10-8 erg s-1 cm-2 sr-1. A halo is detected, but at a much higher surface brightness than our models of recombination emission and dust scattering predict. Only collisional excitation of Lyβ with partial de-excitation to Hα could explain such amplitudes. We show that the halo seen is caused by PSF scattering and thus not related to a real shell. We also investigated the feasibility of a spectroscopic detection of high-velocity Hα gas towards the centre of the Crab nebula. Modelling the emission spectra shows that such gas easily evades detection in the complex spectral environment of the Hα-line. Conclusions: PSF scattering significantly contaminates our data, preventing a detection of the predicted fast shell. A real halo with observed peak flux of about 2 × 10-7 erg s-1 cm-2 sr-1 could still be accomodated within our error bars, but our models predict a factor 4 lower surface brightness. Eight meters class telescopes could detect such fluxes unambiguously, provided that a sufficiently accurate PSF model is available. Finally, we note that PSF scattering also affects other research areas where faint haloes are searched for around bright and extended targets. Based on observations made with ESO Telescopes at the La Silla and Paranal Observatories, Chile (ESO Programmes 66.D-0489, 68.D-0096 and 170.A-0519). Based on observations made with the Nordic Optical Telescope, operated on the island of La

  10. The deep structure of the Western Pyrenees: constraints from tomographic imaging, field and marine geological observations

    NASA Astrophysics Data System (ADS)

    Tugend, Julie; Manatschal, Gianreto; Chevrot, Sébastien; Mohn, Geoffroy

    2015-04-01

    Knowledge of magma-poor rifted margin architecture has significantly evolved over the past decades. Refraction seismic data combined with drill-hole observations unravelled the velocity structure and lithological assemblages of the most distal part of continental rifted margins. Present-day models of continental rifted margins include the occurrence of hyperextended domains consisting in extremely thinned continental crust and/or exhumed subcontinental mantle as described at many rifted margins. Studies in mountain belts revealed that remnants of hyperextended domains could also be identified in internal parts of collisional orogens. Integrating recent developments in the understanding of rifted margins in the study of mountain building processes, in particular the importance of the reactivation of inherited rift structures is therefore essential and may result in alternative interpretations of the lithospheric scale structure of collisional orogens. In this contribution, we focus on the western part of the Pyrenean orogen that resulted from the inversion of a complex Late Jurassic to Mid Cretaceous rift system. The transition from preserved oceanic and rift domains to the west (in the offshore Bay of Biscay) to their complete inversion in the east provides simultaneous access to seismically imaged and exposed parts of a hyperextended rift system. Based on a multi-scale dataset that combines sub-surface data (field and drill-hole observations) with tomographic imaging (PYROPE experiment) and integrating new concepts derived from the study of present-day rifted margins, we investigate the lithospheric-scale architecture of the Western Pyrenees. Our results suggest that the imaged north-dipping crustal root may correspond to the former exhumed mantle and hyperthinned domains that have been subducted/underthrust at the onset of convergence. This interpretation contrasts with the classical assumption that the crustal root is made of lower crustal rocks. This

  11. Observational constraints on mixed-phase clouds imply higher climate sensitivity.

    PubMed

    Tan, Ivy; Storelvmo, Trude; Zelinka, Mark D

    2016-04-01

    Global climate model (GCM) estimates of the equilibrium global mean surface temperature response to a doubling of atmospheric CO2, measured by the equilibrium climate sensitivity (ECS), range from 2.0° to 4.6°C. Clouds are among the leading causes of this uncertainty. Here we show that the ECS can be up to 1.3°C higher in simulations where mixed-phase clouds consisting of ice crystals and supercooled liquid droplets are constrained by global satellite observations. The higher ECS estimates are directly linked to a weakened cloud-phase feedback arising from a decreased cloud glaciation rate in a warmer climate. We point out the need for realistic representations of the supercooled liquid fraction in mixed-phase clouds in GCMs, given the sensitivity of the ECS to the cloud-phase feedback. PMID:27124459

  12. Constraints on seismic anisotropy of the innermost inner core from observations of antipode PKIIKP phases

    NASA Astrophysics Data System (ADS)

    Niu, F.

    2006-12-01

    While the existence of seismic anisotropy in the inner core is well accepted, its magnitude and depth variations are still debated. Besides seismic anisotropy, there is growing evidence that suggests the top several hundred kilometers of the inner core exhibits a hemispherical variation in both velocity (the isotropic wave speed and the magnitude of anisotropy) and attenuation structure. When the PKIKP wave propagates through the uppermost ~400 km of the inner core and reaches a distance less than ~155°, there are two other phases, PKiKP and PKPbc, which have mantle ray paths very close to it. The former is a P wave that reflects off the inner-core boundary (ICB) and the latter is P wave that travels above the ICB. These two phases are usually used as reference phases to infer the uppermost structure of the inner core. As the result, the top ~400 km of the inner core is relatively well studied and its structure is well known. On the other hand to study the deeper ~800 km of the inner core, one must use PKIKP arrivals observed at greater distances where there is no regular phase can be used as a suitable reference phase to remove mantle anomalies. PKPab is sometime used as the reference, but it is generally considered to be a poor reference phase as it has a very different ray path from PKIPK in the mantle and it also travels along the core-mantle boundary (CMB) where very strong lateral heterogeneities are known to exist. Another approach is to use a 3D global mantle velocity model to correct the mantle anomalies in the PKIKP travel time residuals. Using this approach Ishii and Dziewonski (2002) found that the innermost ~300 km exhibits a distinct seismic anisotropy from the rest of body, which they used to argue that the Earth's center might have a unique early history in the core's formation and evolution. Here we report on an observation of the PKIIKP phase, an underside reflected P wave at the ICB, for both the major- and minor-arc ray paths. The major

  13. Observational constraints on mixed-phase clouds imply higher climate sensitivity

    NASA Astrophysics Data System (ADS)

    Tan, Ivy; Storelvmo, Trude; Zelinka, Mark D.

    2016-04-01

    Global climate model (GCM) estimates of the equilibrium global mean surface temperature response to a doubling of atmospheric CO2, measured by the equilibrium climate sensitivity (ECS), range from 2.0° to 4.6°C. Clouds are among the leading causes of this uncertainty. Here we show that the ECS can be up to 1.3°C higher in simulations where mixed-phase clouds consisting of ice crystals and supercooled liquid droplets are constrained by global satellite observations. The higher ECS estimates are directly linked to a weakened cloud-phase feedback arising from a decreased cloud glaciation rate in a warmer climate. We point out the need for realistic representations of the supercooled liquid fraction in mixed-phase clouds in GCMs, given the sensitivity of the ECS to the cloud-phase feedback.

  14. Vertical Profiles as Observational Constraints on Nitrous Oxide (N2O) Emissions in an Agricultural Region

    NASA Astrophysics Data System (ADS)

    Pusede, S.; Diskin, G. S.

    2015-12-01

    We use diurnal variability in near-surface N2O vertical profiles to derive N2O emission rates. Our emissions estimates are ~3 times greater than are accounted for by inventories, a discrepancy in line with results from previous studies using different approaches. We quantify the surface N2O concentration's memory of local surface emissions on previous days to be 50-90%. We compare measured profiles both over and away from a dense N2O source region in the San Joaquin Valley, finding that profile shapes, diurnal variability, and changes in integrated near-surface column abundances are distinct according to proximity to source areas. To do this work, we use aircraft observations from the wintertime DISCOVER-AQ project in California's San Joaquin Valley, a region of intense agricultural activity.

  15. OBSERVATIONAL CONSTRAINTS ON THE CO-EVOLUTION OF SUPERMASSIVE BLACK HOLES AND GALAXIES

    SciTech Connect

    Zheng, X. Z.; Bell, E. F.; Somerville, R. S.; Rix, H.-W.; Jahnke, K.; Fontanot, F.; Meisenheimer, K.; Rieke, G. H.; Schiminovich, D.

    2009-12-20

    The star formation rate (SFR) and black hole accretion rate (BHAR) functions are measured to be proportional to each other at z approx< 3. This close correspondence between SF and BHA would naturally yield a BH mass-galaxy mass correlation, whereas a BH mass-bulge mass correlation is observed. To explore this apparent contradiction, we study the SF in spheroid-dominated galaxies between z = 1 and the present day. We use 903 galaxies from the COMBO-17 survey with M{sub *} > 2 x 10{sup 10} M{sub sun}, ultraviolet and infrared-derived SFRs from Spitzer and Galaxy Evolution Explorer, and morphologies from GEMS Hubble Space Telescope/Advanced Camera for Surveys imaging. Using stacking techniques, we find that <25% of all SF occurs in spheroid-dominated galaxies (Sersic index n > 2.5), while the BHAR that we would expect if the global scalings held is 3 times higher. This rules out the simplest picture of co-evolution, in which SF and BHA trace each other at all times. These results could be explained if SF and BHA occur in the same events, but offset in time, for example at different stages of a merger event. However, one would then expect to see the corresponding star formation activity in early-stage mergers, in conflict with observations. We conclude that the major episodes of SF and BHA occur in different events, with the bulk of SF happening in isolated disks and most BHA occurring in major mergers. The apparent global co-evolution results from the regulation of the BH growth by the potential well of the galactic spheroid, which includes a major contribution from disrupted disk stars.

  16. Surf's Still Up: UVCS/SOHO Observations as Strong Constraints on Coronal Heating Theories

    NASA Astrophysics Data System (ADS)

    Cranmer, S. R.; Kohl, J. L.

    2000-05-01

    In 1996, the Ultraviolet Coronagraph Spectrometer (UVCS) instrument aboard SOHO observed surprisingly broad line profiles of the O VI 1032, 1037 doublet in polar coronal holes. These measurements indicated perpendicular ion temperatures of at least 100--200 million K above two solar radii in the nascent high-speed solar wind. Since then, these observations have been supplemented by profiles of other ions, Doppler dimming measurements made possible by Spartan 201, and a great deal of theoretical work. This talk outlines the current state of understanding about coronal heating and solar wind acceleration that has been facilitated by UVCS. The most promising mechanism for heating and accelerating minor ions remains the dissipation of high-frequency (10 to 10,000 Hz) ion cyclotron waves, but heating the protons is a more open question. The physics of the ion cyclotron interaction in the corona has only begun to be explored, and we will discuss recent insights into the generation and damping of these waves. A self-consistent theory of wave damping and turbulent cascade ``replenishment'' would allow the question of proton heating to be answered more definitively. Also, a kinetic approach to ion cyclotron heating yields non-bi-Maxwellian ``resonant shell'' velocity distributions that could produce emission line profiles narrower than expected from their most probable speeds. Thus, the UVCS measurements of 100--200 million K ion temperatures may only be lower limits. This work is supported by the National Aeronautics and Space Administration under grant NAG5-7822 to the Smithsonian Astrophysical Observatory, by Agenzia Spaziale Italiana, and by the ESA PRODEX program (Swiss contribution).

  17. Observational Constraint of Aerosol Effects on the CMIP5 Inter-model Spread of Adjusted Forcings

    NASA Astrophysics Data System (ADS)

    Chen, J.; Wennberg, P. O.; Jiang, J. H.; Su, H.; Bordoni, S.

    2013-12-01

    The simulated global-mean temperature (GMT) change over the past 150 years is quite consistent across CMIP5 climate models and also consistent with the observations. However, the predicted future GMT under the identical CO2 forcing is divergent. This paradox is partly due to the errors in the predicted GMT produced by historical greenhouse gas (GHG) forcing being compensated by the parameterization of aerosol cloud radiative forcing. Historical increases in anthropogenic aerosols exert an overall (but highly uncertain) cooling effect in the climate system, which partially offsets the warming due to well mixed greenhouse gases (WMGHGs). Because aerosol concentrations are predicted to eventually decrease in future scenarios, climate change becomes dominated by warming due to the WMGHG. This change in the relative importance of forcing by aerosol versus WMGHG makes apparent the substantial differences in prediction of climate by WMGHG forcing. Here we investigate the role of aerosols in the context of adjusted forcing changes in the historical runs and the effect of aerosols on the cloud feedback. Our preliminary results suggest that models which are more sensitive to the increase in concentration of CO2 have a larger aerosol radiative cooling effect. By comparing the historicalMisc runs and historicalGHG runs, we find that aerosols exert a potential impact on the cloud adjusted forcings, especially shortwave cloud adjusted forcings. We use the CLIPSO, MISR and CERES data as the benchmark to evaluate the present aerosol simulations. Using satellite observations to assess the relative reliability of the different model responses and to constrain the simulated aerosol radiative forcing will contribute significantly to reducing the across model spread in future climate simulations and identifying some missing physical processes.

  18. The γ-ray binary LS 5039: mass and orbit constraints from MOST observations

    NASA Astrophysics Data System (ADS)

    Sarty, Gordon E.; Szalai, Tamás; Kiss, László L.; Matthews, Jaymie M.; Wu, Kinwah; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Rucinski, Slavek M.; Sasselov, Dimitar; Weiss, Werner W.; Huziak, Richard; Johnston, Helen M.; Phillips, Andre; Ashley, Michael C. B.

    2011-02-01

    The results of a coordinated space-based photometric and ground-based spectroscopic observing campaign on the enigmatic γ-ray binary LS 5039 are reported. 16 d of observations from the MOST satellite have been combined with high-resolution optical echelle spectroscopy from the 2.3-m ANU Telescope in Siding Spring, Australia. These observat ions were used to measure the orbital parameters of the binary and to study the properties of stellar wind from the O primary. We found that any broad-band optical photometric variability at the orbital period is below the 2 mmag level, supporting the scenario that the orbital eccentricity of the system is near the 0.24 ± 0.08 value implied by our spectroscopy, which is lower than values previously obtained by other workers. The low amplitude optical variability also implies the component masses are at the higher end of estimates based on the primary's O6.5V((f)) spectral type with a primary mass of ˜26 M⊙ and a mass for the compact star of at least 1.8 M⊙. The mass-loss rate from the O primary was determined to be 3.7 to 4.8 × 10-7 M⊙ yr-1. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Microsat Systems Canada Inc. (MSCI, formerly the space division of Dynacon Inc.), the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.

  19. The Formation of Massive Stars by Collisional Mergers: Theoretical Constraints and Observational Predictions

    NASA Astrophysics Data System (ADS)

    Zinnecker, Hans; Bally, John

    2004-08-01

    While accretional growth can lead to the formation of massive stars in isolation or in loose OB associations, collisional growth and mergers can only occur in high-density cluster environments. We will discuss the conditions in a very dense young star cluster under which the merger scenario of massive star formation may work, and whether these conditions are likely to occur somewhere in the our Galaxy (Orion BN/KL, NGC 3603, W3-IRS5), the Local Group (30 Dor, NGC 604), or other galaxies (NGC 5253, Henize 2-10, The Antennae clusters). We explore the observational consequences of the merger scenario. Protostellar mergers may produce high luminosity infrared flares. Mergers may be surrounded by thick tori of expanding debris, impulsive wide-angle outflows, shock-induced maser and radio continuum emission. The collision products are expected to have fast stellar rotation and a large multiplicity fraction. Massive stars growing by a series of mergers may produce eruptive bursts of wide-angle outflow activity with random orientations; the walls of the resulting outflow cavities may be observable as filaments of dense gas and dust pointing away from the massive star. The extremely rare merger of two stars close to the upper mass limit of the IMF may be a possible pathway to hypernova-generated gamma-ray bursters. We also speculate that the outflow "fingers" from the OMC1 core in the Orion molecular cloud were produced by a merger less than a thousand years ago (Bally and Zinnecker 2004, AJ submitted). Mergers may not occur in every dense young cluster, but certainly in some of them, especially those where dynamical mass segregation of massive stars has taken place (Freitag and Benz 2004, astro-ph 0403621).

  20. Observational and Modeling Constraints on Evapotranspiration and Water Vapor in the Upper Midwest, United States

    NASA Astrophysics Data System (ADS)

    Griffis, T. J.

    2014-12-01

    Increases in atmospheric water vapor concentrations and convective precipitation over land provide evidence of intensification of the global hydrologic cycle in response to surface warming. The extent to which terrestrial ecosystems modulate these two components of the hydrologic cycle is important to understanding biophysical feedbacks in the climate system and the availability of water resources. Here, we use a multi-year oxygen-18 and deuterium isotope record of liquid water (precipitation, soil, and plants), atmospheric vapor, tall tower flux measurements, and Stochastic Time-Inverted Lagrangian (STILT) modeling to constrain the importance of evapotranspiration, and other source terms, in the humidification of the planetary boundary layer (PBL). Using an isotope tracer approach we estimated that mid-continental water vapor in the PBL can be derived from as much as 75% local evaporation during the growing season. This result is supported using an inverse modeling approach for cases of extreme dew-point events that have a strong agricultural fingerprint. The isotope observations of water vapor and precipitation were combined with a Monte-Carlo simulation to help constrain a mixing model to estimate the fraction of evaporated terrestrial water in precipitation. The results indicate that growing season precipitation has a median recycling signature of about 30% and is used to help diagnose recycling ratios in mesoscale models. Our land surface modeling results highlight that regional evaporation has changed little over the last 50 years and that the expansion of agricultural crops in the US Midwest has likely reduced the local annual contribution to atmospheric water vapor. These findings are consistent with observed increases in the regional stream-flow data. The compressed growing season of agricultural crops and their high transpiration rates may amplify precipitation intensity and runoff.

  1. AMPLITUDES OF SOLAR-LIKE OSCILLATIONS: CONSTRAINTS FROM RED GIANTS IN OPEN CLUSTERS OBSERVED BY KEPLER

    SciTech Connect

    Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; Kallinger, Thomas; Basu, Sarbani; Mosser, BenoIt; Hekker, Saskia; Mathur, Savita; GarcIa, Rafael A.; Gilliland, Ronald L.; Verner, Graham A.; Chaplin, William J.; Elsworth, Yvonne P.; Meibom, Soeren; Molenda-Zakowicz, Joanna; Szabo, Robert

    2011-08-10

    Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsations. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition implies that the stellar parameters can be measured to much higher precision than what is usually achievable for single stars. This makes clusters ideal for exploring the relation between the mode amplitude of solar-like oscillations and the global stellar properties. We have analyzed data obtained with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a result we provide a new improved empirical relation which treats luminosity and mass separately. This relation turns out to also work remarkably well for main-sequence and subgiant stars. In addition, the measured amplitudes reveal the potential presence of a number of previously unknown unresolved binaries in the red clump in NGC 6791 and NGC 6819, pointing to an interesting new application for asteroseismology as a probe into the formation history of open clusters.

  2. Constraints on the pMSSM from LAT Observations of Dwarf Spheroidal Galaxies

    SciTech Connect

    Cotta, R.C.; Drlica-Wagner, A.; Murgia, S.; Bloom, E.D.; Hewett, J.L.; Rizzo, T.G.; /SLAC

    2012-03-15

    We examine the ability for the Large Area Telescope (LAT) to constrain Minimal Supersymmetric Standard Model (MSSM) dark matter through a combined analysis of Milky Way dwarf spheroidal galaxies. We examine the Lightest Supersymmetric Particles (LSPs) for a set of {approx}71k experimentally valid supersymmetric models derived from the phenomenological-MSSM (pMSSM). We find that none of these models can be excluded at 95% confidence by the current analysis; nevertheless, many lie within the predicted reach of future LAT analyses. With two years of data, we find that the LAT is currently most sensitive to light LSPs (mLSP < 50 GeV) annihilating into {tau}-pairs and heavier LSPs annihilating into b{bar b}. Additionally, we find that future LAT analyses will be able to probe some LSPs that form a sub-dominant component of dark matter. We directly compare the LAT results to direct detection experiments and show the complementarity of these search methods.

  3. Parity Violation Constraints Using Cosmic Microwave Background Polarization Spectra from 2006 and 2007 Observations by the QUaD Polarimeter

    SciTech Connect

    Wu, E. Y. S.; Church, S.; Hinderks, J.; Rusholme, B.; Thompson, K. L.; Ade, P.; Gear, W. K.; Gupta, S.; Rajguru, N.; Turner, A. H.; Bock, J.; Leitch, E.; Bowden, M.; Brown, M. L.; Cahill, G.; Murphy, J. A.; O'Sullivan, C.; Castro, P. G.; Culverhouse, T.; Friedman, R. B.

    2009-04-24

    We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiment's second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of cosmic microwave background photons. We measure the rotation angle due to such a possible 'cosmological birefringence' to be 0.55 deg. {+-}0.82 deg. (random) {+-}0.5 deg. (systematic) using QUaD's 100 and 150 GHz temperature-curl and gradient-curl spectra over the spectra over the multipole range 200constraint to date on electrodynamic parity violation on cosmological scales.

  4. Constraints from Cosmological Data on Expansion and Growth of Structure Observables in a Macroscopic Gravity Averaged Universe

    NASA Astrophysics Data System (ADS)

    Ishak-Boushaki, Mustapha B.; Wijenayake, Tharake

    2016-06-01

    We report recent results from investigating the effect of averaging inhomogeneities on cosmological distances and large-scale structure growth observables using the exact and covariant framework of Macroscopic Gravity (MG) averaging. For the MG formalism applied to the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, this gives an extra dynamical term encapsulated as an averaging density parameter denoted ΩA. We analyze constraints on this parameter and its correlations with other cosmological parameters from using the CMB (Planck), distances to supernovae, Baryon Acoustic Oscillations, Hubble constant measurements, and the CFHTLenS and other recent data. We compare the amplitude of this effect to other systematic effects considered for future high precision surveys.

  5. Gas expulsion in massive star clusters?. Constraints from observations of young and gas-free objects

    NASA Astrophysics Data System (ADS)

    Krause, Martin G. H.; Charbonnel, Corinne; Bastian, Nate; Diehl, Roland

    2016-03-01

    Context. Gas expulsion is a central concept in some of the models for multiple populations and the light-element anti-correlations in globular clusters. If the star formation efficiency was around 30 per cent and the gas expulsion happened on the crossing timescale, this process could preferentially expel stars born with the chemical composition of the proto-cluster gas, while stars with special composition born in the centre would remain bound. Recently, a sample of extragalactic, gas-free, young massive clusters has been identified that has the potential to test the conditions for gas expulsion. Aims: We investigate the conditions required for residual gas expulsion on the crossing timescale. We consider a standard initial mass function and different models for the energy production in the cluster: metallicity-dependent stellar winds, radiation, supernovae and more energetic events, such as hypernovae, which are related to gamma ray bursts. The latter may be more energetic than supernovae by up to two orders of magnitude. Methods: We computed a large number of thin-shell models for the gas dynamics, and calculated whether the Rayleigh-Taylor instability is able to disrupt the shell before it reaches the escape speed. Results: We show that the success of gas expulsion depends on the compactness index of a star cluster C5 ≡ (M∗/ 105 M⊙)/(rh/ pc), with initial stellar mass M∗ and half-mass radius rh. For given C5, a certain critical, local star formation efficiency is required to remove the rest of the gas. Common stellar feedback processes may not lead to gas expulsion with significant loss of stars above C5 ≈ 1. Considering pulsar winds and hypernovae, the limit increases to C5 ≈ 30. If successful, gas expulsion generally takes place on the crossing timescale. Some observed young massive clusters have 1

  6. Observational constraints for the circumstellar disk of the B[e] star CPD-52 9243

    NASA Astrophysics Data System (ADS)

    Cidale, L. S.; Borges Fernandes, M.; Andruchow, I.; Arias, M. L.; Kraus, M.; Chesneau, O.; Kanaan, S.; Curé, M.; de Wit, W. J.; Muratore, M. F.

    2012-12-01

    Context. The formation and evolution of gas and dust environments around B[e] supergiants are still open issues. Aims: We intend to study the geometry, kinematics and physical structure of the circumstellar environment (CE) of the B[e] supergiant CPD-52 9243 to provide further insights into the underlying mechanism causing the B[e] phenomenon. Methods: The influence of the different physical mechanisms acting on the CE (radiation pressure, rotation, bi-stability or tidal forces) is somehow reflected in the shape and kinematic properties of the gas and dust regions (flaring, Keplerian, accretion or outflowing disks). To investigate these processes we mainly used quasi-simultaneous observations taken with high spatial resolution optical long-baseline interferometry (VLTI/MIDI), near-IR spectroscopy of CO bandhead features (Gemini/Phoenix and VLT/CRIRES) and optical spectra (CASLEO/REOSC). Results: High angular resolution interferometric measurements obtained with VLTI/MIDI provide strong support for the presence of a dusty disk(ring)-like structure around CPD-52 9243, with an upper limit for its inner edge of ~8 mas (~27.5 AU, considering a distance of 3.44 kpc to the star). The disk has an inclination angle with respect to the line of sight of 46 ± 7°. The study of CO first overtone bandhead evidences a disk structure in Keplerian rotation. The optical spectrum indicates a rapid outflow in the polar direction. Conclusions: The IR emission (CO and warm dust) indicates Keplerian rotation in a circumstellar disk while the optical line transitions of various species are consistent with a polar wind. Both structures appear simultaneously and provide further evidence for the proposed paradigms of the mass-loss in supergiant B[e] stars. The presence of a detached cold CO ring around CPD-52 9243 could be due to a truncation of the inner disk caused by a companion, located possibly interior to the disk rim, clearing the center of the system. More spectroscopic and

  7. Melt Distribution in the Ethiopian Rift System: Constraints From Seismic Observations and Finite-Frequency Modelling

    NASA Astrophysics Data System (ADS)

    Angus, D.; Hammond, J. O.; Kendall, J.; Wookey, J.

    2008-12-01

    As part of the Ethiopian Afar Geoscientific Lithospheric Experiment (EAGLE) 79 seismic stations were deployed, for up to 18 months, in the Main Ethiopian Rift (MER). Many indicators of melt were observed leading to the idea that magma was driving the rifting process in this region. Some of the best evidence for melt came from observations of anisotropy in studies of surface waves and shear-wave splitting. The shear- wave splitting shows fast directions which change abruptly from being rift parallel on the rift flanks to magmatic-segment parallel in the rift valley. This was interpreted in terms of melt-induced anisotropy. The abrupt change in splitting parameters over small lateral distances suggests that the source of anisotropy is shallow. To further constrain the location of the anisotropy and study the ability of shear-wave splitting to identify sharp lateral changes in anisotropy, we model finite-frequency waveforms for a suite of model representations of the rift zone. This allows us to determine the lateral and vertical extent of the melt-induced anisotropy. The results show how a simple model with two regimes of anisotropy can explain the variability across the rift, in both delay time and shear-wave polarization, over short length scales of the order 20- 40 km. Our models have enabled us to constrain the anisotropic characteristics beneath the MER. Our best model has a 9% anisotropy on the western rift margin, with fast directions of 30°, a 100 km wide rift zone with fast direction of 20° inside the rift zone and with 9% anisotropy close to the western margin, 7% elsewhere, and 7% anisotropy on the eastern margin with fast directions of 30°. In all regions of the model we constrain anisotropy to begin at a depth of 90 km. The depth of anisotropy co-incides with the proposed depth of melt initiation beneath the region, based on geochemistry. Also the elevated splitting beneath the western margin supports evidence of low velocities and highly conductive

  8. Observational constraints and models for conjugate North Atlantic volcanic rifted margins formation

    NASA Astrophysics Data System (ADS)

    Huismans, R. S.; Faleide, J. I.; Planke, S.

    2009-12-01

    The amount of breakup-related magmatism in the northeast Atlantic cannot be explained by passive decompression melting of sub-lithospheric mantle with a normal potential temperature. Three competing end-member hypotheses are proposed for the formation of this excess magmatic activity: 1) excess magmatism results from elevated mantle potential temperatures associated with mantle plume processes, 2) rifting induced small scale convection at the base of the lithosphere enhances the flux of material through the melt window during rifting and mid-oceanic ridge spreading, and 3) mantle heterogeneities with lower melt temperatures of the melt source may produce larger than expected magmatic productivity. We review observations and present forward numerical models of passive margin formation including melt production. Key characteristics that require explanation include: 1) igneous crustal thickness versus mean igneous seismic velocity relationships for magmatic underplated bodies on the Norwegian-Greenland conjugate margins that indicate a cooling trend and seismic velocities that point to a moderate or non-existent mantle thermal anomaly during and after breakup; 2) rapid along margin variations in the observed igneous crustal thickness that suggest a local lithospheric control on melt productivity; 3) significant asymmetries in melt production existing between the Norwegian-Greenland conjugate margins; 4) post rift magmatic activity 30 my after breakup with igneous seismic velocity indicating normal mantle temperature; 5) anomalous low magmatic productivity in the oceanic Norway basin following moderate excess productivity that suggests anomalous low mantle temperatures following breakup, 6) anomalous mantle lithosphere thinning in the distal margin in the late syn-rift, 7) uplift and erosion of highly thinned crustal blocks in the distal margin. Forward numerical models of passive margin formation and melt productivity suggest the following key controls: 1) rifting

  9. Sprites and lightning in Venus: constraints for observations by the Planet-C mission

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Yair, Y.; Goto, Y.; Sentman, D.; Yoshida, J.; Sato, M.; Hoshino, N.

    2007-12-01

    Lightning activity in Venus has been mystery for long period, although many studies based on observations both by spacecrafts and by ground-based telescope have been carried out. This situation may be attributed to the ambiguity of these evidential measurements. In order to conclude this controversial subject, we are developing a new type of lightning detector, LAC (Lightning and Airglow Camera), which will be onboard Planet-C (Venus Climate Orbiter: VCO). PLanet-C will be launched in 2010 by JAXA. To distinguish optical lightning flash from other pulsing noises, high-speed sampling at 50kHz for each pixel, that enables us to investigate the time variation of each lightning flash phenomenon, is adopted. On the other hand, spatial resolution is not first priority. For this purpose we developed new type of APD (avalanche photo diode) array with a format of 8 x 8. Narrow band interference filter at wavelength of 777.4 nm (OI), which is expected lightning color based on laboratory discharge experiment, is chosen for lightning measurement. LAC detects lightning flash with an optical intensity of average of Earth's lightning or less at a distance of 3 Rv. We also present results of theoretical calculations of the expected occurrance heights and emissions of sprites above thunderstorms in the CO2 atmosphere of Venus and the Hydrogen-Helium atmospheres of Jupiter and Saturn. General detection methodology of sprites/lightning in planetary atmospheres by orbiting spacecraft will be discussed.

  10. InSAR observations of lake loading at Yangzhuoyong Lake, Tibet: Constraints on crustal elasticity

    NASA Astrophysics Data System (ADS)

    Zhao, Wenliang; Amelung, Falk; Doin, Marie-Pierre; Dixon, Timothy H.; Wdowinski, Shimon; Lin, Guoqing

    2016-09-01

    We use Envisat 2003-2010 InSAR imagery over Yangzhuoyong Lake in southeastern Tibet to study the elastic response of the Earth's crust to variations in lake level. The net lake level drop during our study period is ∼3 m with seasonal variations of more than 1 m. The time-series close to the lake center shows a high correlation with the lake level history. Near the lake center the unit response with respect to lake level change is 2.5 mm/m in radar line-of-sight direction, or ∼2.7 mm/yr in vertical direction, corresponding to a vertical response of ∼4.3 mm/Gt load change. We show that the observations are most sensitive to the elastic properties of the crust in the 5-15 km depth range and explain them with a layered elastic half-space model with a Young's modulus of 50 ± 9GPa Young's modulus in the top 15 km of the crust and using moduli inferred from seismology at greater depth. The inferred Young's modulus is ∼25% smaller than the seismic modulus, which we attribute to damaged rock and the presence of fluids.

  11. Dark matter and pulsar model constraints from Galactic center Fermi/LAT γ-ray observations

    NASA Astrophysics Data System (ADS)

    Gordon, Chris; Macias, Oscar

    2014-05-01

    Employing Fermi/LAT γ-ray observations, several independent groups have found excess extended γ-ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of ~ 103 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse Galactic background at the GC. We have performed a revaluation of these two models for the extended γ-ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsar population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of several thousand MSPs with parameters consistent with the average spectral shape of Fermi/LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ+τ- annihilation channel is not a good fit to the data. But a mixture of τ+τ- and bb with a <σ v> of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.

  12. Constraints on the origin of the Moon's atmosphere from observations during a lunar eclipse.

    PubMed

    Mendillo, M; Baumgardner, J

    1995-10-01

    The properties of the Moon's rarefied atmosphere, which can be traced through observations of sodium and potassium, provide important insights into the formation and maintenance of atmospheres on other primitive Solar System bodies. The lunar atmosphere is believed to be composed of atoms from the surface rocks and soil, which might have been sputtered by micrometeorites, by ions in the solar wind, or by photons. It might also form by the evaporation of atoms from the hot, illuminated surface. Here we report the detection of sodium emission from the Moon's atmosphere during a total lunar eclipse (which occurs when the Moon is full). The sodium atmosphere is considerably more extended at full Moon than expected--it extends to at least nine lunar radii--and its brightness distribution is incompatible with sources involving either solar-wind or micrometeorite sputtering. This leaves photon sputtering or thermal desorption as the preferred explanations for the lunar atmosphere, and suggests that sunlight might also be responsible for the transient atmospheres of other primitive bodies (such as Mercury). PMID:7566115

  13. Observational Constraints on the Oxidation of NOx in the Upper Troposphere.

    PubMed

    Nault, Benjamin A; Garland, Charity; Wooldridge, Paul J; Brune, William H; Campuzano-Jost, Pedro; Crounse, John D; Day, Douglas A; Dibb, Jack; Hall, Samuel R; Huey, L Gregory; Jimenez, José L; Liu, Xiaoxi; Mao, Jingqiu; Mikoviny, Tomas; Peischl, Jeff; Pollack, Ilana B; Ren, Xinrong; Ryerson, Thomas B; Scheuer, Eric; Ullmann, Kirk; Wennberg, Paul O; Wisthaler, Armin; Zhang, Li; Cohen, Ronald C

    2016-03-10

    NOx (NOx ≡ NO + NO2) regulates O3 and HOx (HOx ≡ OH + HO2) concentrations in the upper troposphere. In the laboratory, it is difficult to measure rates and branching ratios of the chemical reactions affecting NOx at the low temperatures and pressures characteristic of the upper troposphere, making direct measurements in the atmosphere especially useful. We report quasi-Lagrangian observations of the chemical evolution of an air parcel following a lightning event that results in high NOx concentrations. These quasi-Lagrangian measurements obtained during the Deep Convective Clouds and Chemistry experiment are used to characterize the daytime rates for conversion of NOx to different peroxy nitrates, the sum of alkyl and multifunctional nitrates, and HNO3. We infer the following production rate constants [in (cm(3)/molecule)/s] at 225 K and 230 hPa: 7.2(±5.7) × 10(-12) (CH3O2NO2), 5.1(±3.1) × 10(-13) (HO2NO2), 1.3(±0.8) × 10(-11) (PAN), 7.3(±3.4) × 10(-12) (PPN), and 6.2(±2.9) × 10(-12) (HNO3). The HNO3 and HO2NO2 rates are ∼ 30-50% lower than currently recommended whereas the other rates are consistent with current recommendations to within ±30%. The analysis indicates that HNO3 production from the HO2 and NO reaction (if any) must be accompanied by a slower rate for the reaction of OH with NO2, keeping the total combined rate for the two processes at the rate reported for HNO3 production above. PMID:26575342

  14. Satellite observational constraints on ozone radiative forcing in chemistry-climate models

    NASA Astrophysics Data System (ADS)

    Bowman, K. W.; Aghedo, A. M.; Worden, H. M.; Kulawik, S. S.; Shindell, D. T.; Lamarque, J.; Faluvegi, G.; Parrington, M.; Jones, D. B.; Rast, S.; Naik, V.; Horowitz, L. W.

    2010-12-01

    Tropospheric ozone radiative forcing is primarily driven by longwave absorption, and its accurate estimation is contingent on the ability of models to simulate the spatial and vertical distribution of ozone within the entire troposphere. Based on model calculations, the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC AR4) estimated tropospheric ozone radiative forcing as 0.35 Wm-2 (with a multi-model spread of 0.25 - 0.65 Wm-2), making the greenhouse effect of tropospheric ozone the third largest following carbon dioxide and methane. However since the IPCC second assessment report, the estimate has not changed substantially and the uncertainties have slightly increased. We demonstrate the application of Tropospheric Emission Spectrometer (TES) all-sky instantaneous radiative forcing (IRF) kernels as a new and unique way for an observationally constrained evaluation of ozone calculated by models. These IRF kernels are the changes in the top-of-the-atmosphere radiative flux due to vertical and spatial distribution of ozone. The discrepancies between TES and five state-of-the-art chemistry climate models, which are AM2-Chem, AM3-Chem, CAM-Chem, ECHAM5-MOZ and GISS-PUCCINI in August 2006 resulted in tropospheric IRF biases from -0.4 to +0.7 W/m2 over large regions within the tropics and mid-latitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper- troposphere lower-stratospheric region. The zonal mean IRF biases also range from -30 to +40 milli-Watts/m2 for the models with an ensemble mean total tropospheric IRF bias of less than 0.2 W/m2 within the entire troposphere.

  15. Volcanic Lightning: Update on New Global Observations and Constraints on Source Mechanisms

    NASA Astrophysics Data System (ADS)

    McNutt, S. R.; Venzke, E.; Williams, E. R.

    2014-12-01

    New data on volcanic lightning from the Smithsonian Volcano Reference File are added to an existing database and greatly expand the number of cases available for study. Lightning has now been documented at 154 volcanoes in association with over 400 eruptions, a significant increase from the earlier numbers of 89 volcanoes and 240 eruptions. Lightning and electrification at volcanoes are important because they represent a hazard in their own right, they are a component of the global electrical circuit, and because they contribute to ash particle aggregation and modification within ash plumes. The role of water substance (water in all forms) in particular has not been well studied. The Volcanic Explosivity Index (VEI) was determined for 177 eruptions. Eight percent of VEI=3-5 eruptions have reported lightning, and 10 percent of VEI=6, but less than 2 percent of those with VEI=1-2, suggesting consistent reporting for larger eruptions but either less lightning or under-reporting for small eruptions. Ash plume heights (142 observations) show a bimodal distribution with peaks at 7-12 km and 1-4 km. The former are similar to heights of typical thunderstorms and suggest involvement of water substance, whereas the latter suggest other factors contributing to electrical behavior near the vent. The distributions of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes; flat with latitude. Meteorological lightning, on the other hand, is common in the tropics and decreases markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward. This finding supports the idea that if lightning in large eruptions depends on water substance, then the origin of the water is primarily magma and not entrainment from the surrounding atmosphere.

  16. Slow slip pulses driven by thermal pressurization of pore fluid: theory and observational constraints

    NASA Astrophysics Data System (ADS)

    Garagash, D.

    2012-12-01

    We discuss recently developed solutions for steadily propagating self-healing slip pulses driven by thermal pressurization (TP) of pore fluid [Garagash, 2012] on a fault with a constant sliding friction. These pulses are characterized by initial stage of undrained weakening of the fault (when fluid/heat can not yet escape the frictionally heated shear zone), which gives way to partial restrengthening due to increasing hydrothermal diffusion under conditions of diminished rate of heating, leading to eventual locking of the slip. The rupture speed of these pulses is decreasing function of the thickness (h) of the principal shear zone. We find that "thick" shear zones, h >> hdyna, where hdyna = (μ/τ0) (ρc/fΛ)(4α/cs), can support aseismic TP pulses propagating at a fraction hdyna/h of the shear wave speed cs, while "thin" shear zones, h˜hdyna or thinner, can only harbor seismic slip. (Here μ - shear modulus, τ0 - the nominal fault strength, f - sliding friction, ρc - the heat capacity of the fault gouge, Λ - the fluid thermal pressurization factor, α - hydrothermal diffusivity parameter of the gouge). For plausible range of fault parameters, hdyna is between 10s to 100s of micrometers, suggesting that slow slip transients propagating at 1 to 10 km/day may occur in the form of a TP slip pulse accommodated by a meter-thick shear zone. We verify that this is, indeed, a possibility by contrasting the predictions for aseismic, small-slip TP pulses operating at seismologically-constrained, near-lithostatic pore pressure (effective normal stress ≈ 3 to 10 MPa) with the observations (slip duration at a given fault location ≈ week, propagation speed ≈ 15 km/day, and the inferred total slip ≈ 2 to 3 cm) for along-strike propagation of the North Cascadia slow slip events of '98-99 [Dragert et al., 2001, 2004]. Furthermore, we show that the effect of thermal pressurization on the strength of the subduction interface is comparable to or exceeds that of the rate

  17. Radar Observations of Near-Earth Asteroid (52760) 1998 ML14: Constraints from the 1998 and 2013 Apparitions

    NASA Astrophysics Data System (ADS)

    Sharkey, Benjamin N. L.; Taylor, Patrick A.; Nolan, Michael C.; Howell, Ellen S.

    2015-11-01

    Ostro et al. (Meteoritics & Planetary Science, 36, 1225-1236, 2001) produced a shape model of the approximately 1-km diameter near-Earth asteroid (52760) 1998 ML14 using radar images taken with the Arecibo and Goldstone planetary radar systems in 1998. However, the spin state (pole orientation and rotation period) was not well determined in their modelling. The published shape model was produced using a 14.83 h sidereal rotation period, consistent with the synodic period of 14.98 ± 0.06 h found by optical observations in 1998 (Hicks & Weissman, IAU Circular 6987, 1, 1998). Optical observations in 2013 found a faster period of 14.28 ± 0.01 h (Warner, The Minor Planet Bulletin, 41, 2, 113-124, 2014). Further radar observations at Arecibo in 2013 are inconsistent with the 14.83 h sidereal period. Use of Arecibo radar images from both apparitions, with resolution as fine as 15 m per pixel, are best fit by a sidereal period within 1% of 14.28 h and constrain the pole orientation to within approximately ten degrees. An updated shape model will be presented using this new information. These improved constraints illustrate the power of multiple apparitions for better determining the true shapes and spin states of near-Earth asteroids.

  18. Filaments in the southern giant lobe of Centaurus A: constraints on nature and origin from modelling and GMRT observations

    NASA Astrophysics Data System (ADS)

    Wykes, Sarka; Intema, Huib T.; Hardcastle, Martin J.; Achterberg, Abraham; Jones, Thomas W.; Jerjen, Helmut; Orrú, Emanuela; Lazarian, Alex; Shimwell, Timothy W.; Wise, Michael W.; Kronberg, Philipp P.

    2014-08-01

    We present results from imaging of the radio filaments in the southern giant lobe of Centaurus A using data from Giant Metrewave Radio Telescope observations at 325 and 235 MHz, and outcomes from filament modelling. The observations reveal a rich filamentary structure, largely matching the morphology at 1.4 GHz. We find no clear connection of the filaments to the jet. We seek to constrain the nature and origin of the vertex and vortex filaments associated with the lobe and their role in high-energy particle acceleration. We deduce that these filaments are at most mildly overpressured with respect to the global lobe plasma showing no evidence of large-scale efficient Fermi I-type particle acceleration, and persist for ˜2-3 Myr. We demonstrate that the dwarf galaxy KK 196 (AM 1318-444) cannot account for the features, and that surface plasma instabilities, the internal sausage mode and radiative instabilities are highly unlikely. An internal tearing instability and the kink mode are allowed within the observational and growth time constraints and could develop in parallel on different physical scales. We interpret the origin of the vertex and vortex filaments in terms of weak shocks from transonic magnetohydrodynamical turbulence or from a moderately recent jet activity of the parent AGN, or an interplay of both.

  19. Additive genetic variation in resistance traits of an exotic pine species: little evidence for constraints on evolution of resistance against native herbivores

    PubMed Central

    Moreira, X; Zas, R; Sampedro, L

    2013-01-01

    The apparent failure of invasions by alien pines in Europe has been explained by the co-occurrence of native pine congeners supporting herbivores that might easily recognize the new plants as hosts. Previous studies have reported that exotic pines show reduced tolerance and capacity to induce resistance to those native herbivores. We hypothesize that limited genetic variation in resistance to native herbivores and the existence of evolutionary trade-offs between growth and resistance could represent additional potential constraints on the evolution of invasiveness of exotic pines outside their natural range. In this paper, we examined genetic variation for constitutive and induced chemical defences (measured as non-volatile resin in the stem and total phenolics in the needles) and resistance to two major native generalist herbivores of pines in cafeteria bioassays (the phloem-feeder Hylobius abietis and the defoliator Thaumetopoea pityocampa) using half-sib families drawn from a sample of the population of Pinus radiata introduced to Spain in the mid-19th century. We found (i) significant genetic variation, with moderate-to-high narrow-sense heritabilities for both the production of constitutive non-volatile resin and induced total phenolics, and for constitutive resistance against T. pityocampa in bioassays, (ii) no evolutionary trade-offs between plant resistance and growth traits or between the production of different quantitative chemical defences and (iii) a positive genetic correlation between constitutive resistance to the two studied herbivores. Overall, results of our study indicate that the exotic pine P. radiata has limited genetic constraints on the evolution of resistance against herbivores in its introduced range, suggesting that, at least in terms of interactions with these enemies, this pine species has potential to become invasive in the future. PMID:23232833

  20. Additive genetic variation in resistance traits of an exotic pine species: little evidence for constraints on evolution of resistance against native herbivores.

    PubMed

    Moreira, X; Zas, R; Sampedro, L

    2013-05-01

    The apparent failure of invasions by alien pines in Europe has been explained by the co-occurrence of native pine congeners supporting herbivores that might easily recognize the new plants as hosts. Previous studies have reported that exotic pines show reduced tolerance and capacity to induce resistance to those native herbivores. We hypothesize that limited genetic variation in resistance to native herbivores and the existence of evolutionary trade-offs between growth and resistance could represent additional potential constraints on the evolution of invasiveness of exotic pines outside their natural range. In this paper, we examined genetic variation for constitutive and induced chemical defences (measured as non-volatile resin in the stem and total phenolics in the needles) and resistance to two major native generalist herbivores of pines in cafeteria bioassays (the phloem-feeder Hylobius abietis and the defoliator Thaumetopoea pityocampa) using half-sib families drawn from a sample of the population of Pinus radiata introduced to Spain in the mid-19th century. We found (i) significant genetic variation, with moderate-to-high narrow-sense heritabilities for both the production of constitutive non-volatile resin and induced total phenolics, and for constitutive resistance against T. pityocampa in bioassays, (ii) no evolutionary trade-offs between plant resistance and growth traits or between the production of different quantitative chemical defences and (iii) a positive genetic correlation between constitutive resistance to the two studied herbivores. Overall, results of our study indicate that the exotic pine P. radiata has limited genetic constraints on the evolution of resistance against herbivores in its introduced range, suggesting that, at least in terms of interactions with these enemies, this pine species has potential to become invasive in the future. PMID:23232833

  1. X-linked myotubular myopathy: clinical observations in ten additional cases.

    PubMed

    Joseph, M; Pai, G S; Holden, K R; Herman, G

    1995-11-01

    X-linked myotubular myopathy (XLMTM) is a recessively inherited disorder, lethal to males in the first months of life. Since the first report in 1969, at least 90 cases have been described in the literature. Diagnosis is confirmed by muscle biopsy. Linkage studies have localized the disorder to the Xq28 region, close to the loci for X-linked hydrocephalus and MASA syndrome. We report on 10 additional cases of XLMTM from six different families. In addition to classic clinical features of XLMTM, our patients showed interesting associated findings which included birth length > 90th centile and large head circumference with or without hydrocephalus in 70%, narrow, elongated face in 80%, and slender, long digits in 60% of cases. There was concordance in the occurrence and severity of hydrocephalus in most sib pairs. These features in a "floppy" male infant serve as clues for early clinical diagnosis of XLMTM, which can then be confirmed by muscle biopsy. Development of polyhydramnios was observed in the third trimester of an at-risk dizygotic twin gestation monitored by serial sonography with confirmation of XLMTM at birth. PMID:8588581

  2. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Hays, E.; Perkins, J. S.

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma ray flux upper limits between 500MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma ray background modeling, and assumed dark matter density profile.

  3. Addition of a channel for XCO observations to a portable FTIR spectrometer for greenhouse gas measurements

    NASA Astrophysics Data System (ADS)

    Hase, Frank; Frey, Matthias; Kiel, Matthäus; Blumenstock, Thomas; Harig, Roland; Keens, Axel; Orphal, Johannes

    2016-05-01

    The portable FTIR (Fourier transform infrared) spectrometer EM27/SUN, dedicated to the precise and accurate observation of column-averaged abundances of methane and carbon dioxide, has been equipped with a second detector channel, which allows the detection of additional species, especially carbon monoxide. This allows an improved characterisation of observed carbon dioxide enhancements and makes the extended spectrometer especially suitable as a validation tool of ESA's Sentinel 5 Precursor mission, as it now covers the same spectral region as used by the infrared channel of the TROPOMI (TROPOspheric Monitoring Instrument) sensor. The extension presented here does not rely on a dichroic, but instead a fraction of the solar beam is decoupled near the aperture stop of the spectrometer using a small plane mirror. This approach allows maintaining the camera-controlled solar tracker set-up, which is referenced to the field stop in front of the primary detector. Moreover, the upgrade of existing instruments can be performed without alterating the optical set-up of the primary channel and resulting changes of the instrumental characteristics of the original instrument.

  4. Constraints on values of biological parameters by observed turbulence in a quasi-2D phytoplankton model of the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hahn-Woernle, Lisa; Dijkstra, Henk A.; van der Woerd, Hans J.

    2013-04-01

    Constraints on values of biological parameters by observed turbulence in a quasi-2D phytoplankton model of the North Atlantic Session and Session Number: Scaling and complex Physical and Biogeophysical Processes in the Atmosphere, Ocean and climate (NP3.1) Preferred Mode of Presentation: Oral Lisa Hahn-Woernle¹, Henk A. Dijkstra¹ & Hans J. van der Woerd² 1. Institute for Marine and Atmospheric research Utrecht, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands. 2. Institute for Environmental Studies, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. During the STRATIPHYT cruises in Summer 2009 and Spring 2011 in-situ plankton and nutrient concentrations as well as upper-ocean turbulence characteristics were measured from Las Palmas to Reykjavik [1,2]. The measurements agree with previous findings that the incoming light intensity and the stratification of the upper ocean set important conditions for the initiation of the phytoplankton bloom close to the surface and also for a possible shift to a deep chlorophyll maximum below the mixed layer. These strong characteristic spatial patterns and temporal cycles of phytoplankton surface concentration are also observed in satellite images of chlorophyll-a concentration in the Northern Atlantic. To understand the meridional depth (upper 200 m) variation of the phytoplankton distributions, a quasi-2D phytoplankton model was used. The results indicate that with the given profiles of the turbulent vertical mixing coefficient, only a very limited interval for the biological model parameters leads to the observed depth of the phytoplankton maximum. [1] E. Jurado, H. van der Woerd and H. A. Dijkstra, Microstructure measurements along a quasi-meridional transect in the North Atlantic, J. Geophysical Res. Oceans, 117, C04016, doi:10.1029/2011JC007137, (2012). [2] E. Jurado, H. A. Dijkstra and H. van der Woerd, Microstructure observations during the spring 2011 STRATIPHYT-II cruise in the

  5. The efficacy of combining satellite water storage and soil moisture observations as constraints on water balance estimation

    NASA Astrophysics Data System (ADS)

    Tian, Siyuan; van Dijk, Albert; Renzullo, Luigi; Tregoning, Paul; Walker, Jeffrey; Pauwels, Valentijn

    2016-04-01

    improves estimation of the soil moisture profile (0 -1 m) but has little impact on TWS. The assimilation of TWS data significantly improves the deep soil moisture and groundwater dynamics, but causes a slight degradation of SSM estimation. Analysis showed that both observations can be jointly assimilated without imparting conflicting constraints and there is clear advantage in integrating them to ensure accurate estimates of both SSM and TWS.

  6. Observations and modelling of CO and [C i] in protoplanetary disks. First detections of [C i] and constraints on the carbon abundance

    NASA Astrophysics Data System (ADS)

    Kama, M.; Bruderer, S.; Carney, M.; Hogerheijde, M.; van Dishoeck, E. F.; Fedele, D.; Baryshev, A.; Boland, W.; Güsten, R.; Aikutalp, A.; Choi, Y.; Endo, A.; Frieswijk, W.; Karska, A.; Klaassen, P.; Koumpia, E.; Kristensen, L.; Leurini, S.; Nagy, Z.; Perez Beaupuits, J.-P.; Risacher, C.; van der Marel, N.; van Kempen, T. A.; van Weeren, R. J.; Wyrowski, F.; Yıldız, U. A.

    2016-04-01

    Context. The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, C0, and C+ can now be observed regularly in disks. Aims: The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the [C]/[H] ratio in a large sample of disks, and compile an overview of the strength of [C i] and warm CO emission. Methods: We carried out a survey of the CO 6-5 line and the [C i] 1-0 and 2-1 lines towards 37 disks with the APEX telescope, and supplemented it with [C ii] data from the literature. The data are interpreted using a grid of models produced with the DALI disk code. We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties. Results: The CO 6-5 line is detected in 13 out of 33 sources, [C i] 1-0 in 6 out of 12, and [C i] 2-1 in 1 out of 33. With separate deep integrations, the first unambiguous detections of the [C i] 1-0 line in disks are obtained, in TW Hya and HD 100546. Conclusions: Gas-phase carbon abundance reductions of a factor of 5-10 or more can be identified robustly based on CO and [C i] detections, assuming reasonable constraints on other parameters. The atomic carbon detection towards TW Hya confirms a factor of 100 reduction of [C]/[H]gas in that disk, while the data are consistent with an ISM-like carbon abundance for HD 100546. In addition, BP Tau, T Cha, HD 139614, HD 141569, and HD 100453 are either carbon-depleted or gas-poor disks. The low [C i] 2-1 detection rates in the survey mostly reflect insufficient sensitivity for T Tauri disks. The Herbig Ae/Be disks with CO and [C ii] upper limits below the models are debris-disk-like systems. An increase in sensitivity of roughly order of magnitude compared to our survey is required to obtain useful constraints on the gas-phase [C]/[H] ratio in most of the

  7. Use of Multiple-Angle Snow Camera (MASC) Observations as a Constraint on Radar-Based Retrievals of Snowfall Rate

    NASA Astrophysics Data System (ADS)

    Cooper, S.; Garrett, T. J.; Wood, N.; L'Ecuyer, T. S.

    2015-12-01

    We use a combination of Ka-band Zenith Radar (KaZR) and Multiple-Angle Snow Camera (MASC) observations at the ARM North Slope Alaska Climate Facility Site at Barrow to quantify snowfall. The optimal-estimation framework is used to combine information from the KaZR and MASC into a common retrieval scheme, where retrieved estimates of snowfall are compared to observations at a nearby NWS measurement site for evaluation. Modified from the operational CloudSat algorithm, the retrieval scheme returns estimates of the vertical profile of exponential PSD slope parameter with a constant number density. These values, in turn, can be used to calculate surface snowrate (liquid equivalent) given knowledge of snowflake microphysical properties and fallspeeds. We exploit scattering models for a variety of ice crystal shapes including aggregates developed specifically from observations of snowfall properties at high-latitudes, as well as more pristine crystal shapes involving sector plates, bullet rosettes, and hexagonal columns. As expected, initial retrievals suggest large differences (300% for some events) in estimated snowfall accumulations given the use of the different ice crystal assumptions. The complex problem of how we can more quantitatively link MASC snowflake images to specific radar scattering properties is an ongoing line of research. Here, however, we do quantify the use of MASC observations of fallspeed and PSD parameters as constraint on our optimal-estimation retrieval approach. In terms of fallspeed, we find differences in estimated snowfall of nearly 50% arising from the use of MASC observed fallspeeds relative to those derived from traditional fallspeed parameterizations. In terms of snowflake PSD, we find differences of nearly 25% arising from the use of MASC observed slope parameters relative to those derived from field campaign observations of high-altitude snow events. Of course, these different sources of error conspire to make the estimate of snowfall

  8. Bifunctional reactivity of amidoximes observed upon nucleophilic addition to metal-activated nitriles.

    PubMed

    Bolotin, Dmitrii S; Demakova, Marina Ya; Novikov, Alexander S; Avdontceva, Margarita S; Kuznetsov, Maxim L; Bokach, Nadezhda A; Kukushkin, Vadim Yu

    2015-04-20

    Treatment of the aromatic nitrile complexes trans-[PtCl2(RC6H4CN)2] (R = p-CF3 NC1, H NC2, o-Cl NC3) with the aryl amidoximes p-R'C6H4C(NH2)=NOH (R' = Me AO1, H AO2, Br AO3, CF3 AO4, NO2 AO5) in all combinations, followed by addition of 1 equiv of AgOTf and then 5 equiv of Et3N, leads to the chelates [PtCl{HN=C(RC6H4)ON=C(C6H4R'-p)NC(RC6H4)═NH}] (1-15; 15 examples; yields 71-88% after column chromatography) derived from the platinum(II)-mediated coupling between metal-activated nitriles and amidoximes. The mechanism of this reaction was studied experimentally by trapping and identification of the reaction intermediates, and it was also investigated theoretically at the DFT level of theory. The combined experimental and theoretical results indicate that the coupling with the nitrile ligands involves both the HON and monodeprotonated NH2 groups of the amidoximes, whereas in the absence of the base, the NH2 functionality is inactive toward the coupling. The observed reaction represents the first example of bifunctional nucleophilic behavior of amidoximes. The complexes 1-16 were characterized by elemental analyses (C, H, N), high-resolution ESI(+)-MS, FTIR, and (1)H NMR techniques, whereas unstable 17 was characterized by HRESI(+)-MS and FTIR. In addition, 8·C4H8O2, 12, and 16·CHCl3 were studied by single-crystal X-ray diffraction. PMID:25822628

  9. Observation of Emerging Photoinitiator Additives in Household Environment and Sewage Sludge in China.

    PubMed

    Liu, Runzeng; Lin, Yongfeng; Hu, Fanbao; Liu, Ruirui; Ruan, Ting; Jiang, Guibin

    2016-01-01

    Photoinitiators (PIs) are widely used additives in industrial polymerization process, the contamination of which through migration into foodstuffs has been subjected to increasing public scrutiny. Nevertheless, little attention has been paid to the PI residue levels and potential exposure pathways from other environmental compartments. In the present study, the occurrence of PI additives with discrete molecular structures, that is, nine benzophenones (BZPs), four thioxanthones (TXs), and eight amine co-initiators (ACIs), was investigated in commercial products, indoor dust and sewage sludge samples. Nine PI compounds were positively detected in ultraviolet curable resins with concentrations of ∑PIs (sum of the detected PIs) up to 2.51 × 10(4) ng/g, and 20 PIs can be found in food contact materials with concentrations of ∑PIs varying from 65.9 to 6.93 × 10(3) ng/g. The wide usage of PIs in commercial products led to the occurrence of 19 PIs in indoor dust, with concentrations of ∑PIs in the range of 245-5.68 × 10(3) ng/g. Meanwhile, all 21 targeted PIs could be identified in the sewage sludge, with concentrations from 67.6 to 2.03 × 10(3) ng/g. Distinct PI composition profiles were observed in different investigated compartments, and BZPs were the dominant homologues in all samples. Most of the target PIs were further identified as class III chemicals by toxic hazard estimation algorithm (Toxtree), which indicates the compounds might be of significant toxicity or have reactive functional groups. PMID:26649800

  10. Constraints on the Nature of the Lithosphere-Asthenosphere Boundary: Comparison of Observed Textural Evolution to Measured Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Hansen, L. N.; Qi, C.; Kumamoto, K.; Warren, J. M.; Katz, R. F.; Kohlstedt, D. L.

    2014-12-01

    The nature of the lithosphere-asthenosphere boundary (LAB) determines the mechanical and compositional coupling between rigid plates and underlying convecting mantle. Seismological studies reveal distinct reflectors in the uppermost oceanic mantle that are sometimes interpreted as the LAB. These reflectors roughly correlate with the location of vertical gradients in radial seismic anisotropy. However, these proxies for the LAB 1) do not exhibit the depth-age relationship predicted by thermal models and 2) are not detected consistently throughout the major ocean basins. In contrast, gradients in azimuthal anisotropy in oceanic upper mantle do appear to coincide with the predicted thermal structure. This overall seismic signature is suggested to arise both from melt-related processes at mid-ocean ridges and from "freezing in" anisotropy during changes in the direction of plate motion. We test recent interpretations of this upper-mantle seismic structure with measurements of crystallographic textures in experimentally and naturally deformed peridotites. Key observations: 1) Experimental deformation of nominally melt-free olivine aggregates reveals a protracted increase in texture strength and, therefore, in magnitude of elastic anisotropy with progressive deformation, 2) melt-rich systems attain a steady state at very low strain (<~1) with fast seismic directions normal to those in the melt-free case, and 3) textures measured in samples from peridotite massifs exhibit a cm- to m-scale compositional heterogeneity associated with melt production and extraction that could be a significant source of radial anisotropy. In conjunction with constraints on finite strain and melting extent from geodynamic simulations, we use textural observations to predict seismic structure in an oceanic setting. Comparison of our predictions to observed seismic anisotropy provide insight into the role of composition, melting, and rheology in defining the LAB.

  11. Spectroscopic analyses of subluminous B stars: observational constraints for the theory of stellar evolution, pulsation, and diffusion

    NASA Astrophysics Data System (ADS)

    Edelmann, Heinz

    2003-06-01

    This thesis deals with quantitative spectroscopic analyses of large samples of subluminous B stars in order to find constraints the theory of stellar evolution, pulsation, and diffusion. Subluminous B stars, also known as subdwarf B (sdB) stars, are very important in several respects: They dominate the population of faint blue stars in high galactic latitudes, and are found both in the field and in globular clusters. Therefore, sdB stars are important to understand the structure and evolution of our galaxy. From the cosmological point of view, they are candidate progenitors of supernovae of type Ia due to their membership in close binary systems. In the context of stellar astrophysics, subdwarf B stars play an important role because several of them are discovered to show non-radial pulsations, which allows to probe their interior by asteroseismology. Last but not least, sdB stars show very peculiar element abundance patterns, probably caused by diffusion processes. Subluminous B stars are generally considered to be core helium-burning stars with extremely thin hydrogen envelopes (< 0.02M) and masses around 0.5M. In the Hertzsprung-Russell diagram they populate a very narrow area which lies on a blue-ward extension of the horizontal branch (HB), the so called "Extreme Horizontal Branch" (EHB). Due to their thin hydrogen-rich envelope, they cannot sustain a hydrogen-burning shell. This means that the sdB stars cannot ascend the asymptotic giant branch after the end of the helium-core burning, but should evolve directly to the white dwarf graveyard. However, according to standard stellar evolution theory, subdwarf B stars should not exist. Their evolution is still unclear and several scenarios are under debate. For all these investigations, knowledge of the stellar parameters (effective temperature, gravity and chemical composition) is very important to verify or discard theoretical models and predictions. Numerous observing runs have been performed mostly by myself

  12. Constraints on the binary properties of mid- to late T dwarfs from Hubble space telescope WFC3 observations

    SciTech Connect

    Aberasturi, M.; Solano, E.; Burgasser, A. J.; Mora, A.; Martín, E. L.; Reid, I. N.; Looper, D.

    2014-12-01

    We used Hubble Space Telescope/Wide Field Camera 3 (WFC3) observations of a sample of 26 nearby (≤20 pc) mid- to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs (BDs). Tightly separated companions were searched for using a double point-spread-function-fitting algorithm. We also compared our detection limits based on simulations to other prior T5+ BD binary programs. No new wide or tight companions were identified, which is consistent with the number of known T5+ binary systems and the resolution limits of WFC3. We use our results to add new constraints to the binary fraction (BF) of T-type BDs. Modeling selection effects and adopting previously derived separation and mass ratio distributions, we find an upper limit total BF of <16% and <25% assuming power law and flat mass ratio distributions, respectively, which are consistent with previous results. We also characterize a handful of targets around the L/T transition.

  13. Constraints on Λ(t)CDM models as holographic and agegraphic dark energy with the observational Hubble parameter data

    SciTech Connect

    Zhai, Zhong-Xu; Liu, Wen-Biao; Zhang, Tong-Jie E-mail: tjzhang@bnu.edu.cn

    2011-08-01

    The newly released observational H(z) data (OHD) is used to constrain Λ(t)CDM models as holographic and agegraphic dark energy. By the use of the length scale and time scale as the IR cut-off including Hubble horizon (HH), future event horizon (FEH), age of the universe (AU), and conformal time (CT), we achieve four different Λ(t)CDM models which can describe the present cosmological acceleration respectively. In order to get a comparison between such Λ(t)CDM models and standard ΛCDM model, we use the information criteria (IC), Om(z) diagnostic, and statefinder diagnostic to measure the deviations. Furthermore, by simulating a larger Hubble parameter data sample in the redshift range of 0.1 < z < 2.0, we get the improved constraints and more sufficient comparison. We show that OHD is not only able to play almost the same role in constraining cosmological parameters as SNe Ia does but also provides the effective measurement of the deviation of the DE models from standard ΛCDM model. In the holographic and agegraphic scenarios, the results indicate that the FEH is more preferable than HH scenario. However, both two time scenarios show better approximations to ΛCDM model than the length scenarios.

  14. OT2_jalcolea_2: Additional Hpoint observations of large post-AGB sources from HIFIStars

    NASA Astrophysics Data System (ADS)

    Alcolea, J.

    2011-09-01

    One of the most spectacular phases in the evolution of intermediate mass stars takes place at the end of their lives. At the end of the AGB, the central star dashes across the HR diagram from the red giant to the blue dwarf region. At the same time, the spherically symmetric and slowly expanding circumstellar envelopes around AGB stars become planetary nebulae (PNe), displaying a large variety of shapes and structures far more complex. This transformation takes place at the very end of the AGB, and it is due to the interaction of fast and bipolar molecular winds with the fossil AGB circumstellar envelope. The origin of these post-AGB winds is still unclear, but we know that the resulting two-wind interactions are only active during a very short period of time, ~ 100 yr, but still they are able to strongly modify the kinematics of the nebulae and re-shape them. To better understand these processes we must study the warm molecular gas component of early post-AGB sources, both pre-planetary nebulae (pPNe) and young PNe. Herschel/HIFI is very well suited at this, because its spectral coverage, high velocity resolution, and superb sensitivity. For these reasons, 10 pPNe and young PNe were included in the KPGT HIFISTARS, were a large number of spectral lines are observed in a moderate number of frequency setups, but just at the central point. In many cases this is simply enough, since most post-AGB sources in HIFIStars are compact. However there are three cases in which the non spherically symmetric structures seen in the warm gas are larger than the telescope beam: OH231.8+4.2, NGC7027 and NGC6302. Therefore we propose to perform some additional points in these three sources in a selected sample of HIFISTARS frequency setups, were we have detected strong lines of CO, H2O, NH3 and OH. These observations are crucial to understand the kinematics and interactions traced by these warm gas probes, and gain insight in the intricate problem of the post-AGB dynamics.

  15. The Excitation of Extended Red Emission: New Constraints on Its Carrier from Hubble Space Telescope Observations of NGC 7023

    NASA Astrophysics Data System (ADS)

    Witt, Adolf N.; Gordon, Karl D.; Vijh, Uma P.; Sell, Paul H.; Smith, Tracy L.; Xie, Rui-Hua

    2006-01-01

    The carrier of the dust-associated photoluminescence process causing ERE in many dusty interstellar environments remains unidentified. Several competing models are more or less able to match the observed broad, unstructured ERE band. We now constrain the character of the ERE carrier further by determining the wavelengths of the radiation that initiates the ERE. Using the imaging capabilities of the HST, we have resolved the width of narrow ERE filaments appearing on the surfaces of externally illuminated molecular clouds in the bright reflection nebula NGC 7023 and compared them with the depth of penetration of radiation of known wavelengths into the same cloud surfaces. We identify photons with wavelengths shortward of 118 nm as the source of ERE initiation, not to be confused with ERE excitation, however. There are strong indications from the well-studied ERE in the Red Rectangle Nebula and in the high-|b| Galactic cirrus that the photon flux with wavelengths shortward of 118 nm is too small to actually excite the observed ERE, even with 100% quantum efficiency. We conclude, therefore, that ERE excitation results from a two-step process. The first, involving far-UV photons with E>10.5 eV, leads to the creation of the ERE carrier, most likely through photoionization or photodissociation of an existing precursor. The second, involving more abundant near-UV/optical photons, consists of the optical pumping of the previously created carrier, followed by subsequent deexcitation via photoluminescence. The latter process can occur many times for a single particle, depending upon the lifetime of the ERE carrier in its active state. While none of the previously proposed ERE models can match these new constraints, we note that under interstellar conditions most PAH molecules are ionized to the dication stage by photons with E>10.5 eV and that the electronic energy level structure of PAH dications is consistent with fluorescence in the wavelength band of the ERE. Therefore

  16. Constraints on interseismic locking along the southern Cascadia subduction zone from historic and recent leveling and sea level observations

    NASA Astrophysics Data System (ADS)

    Burgette, R. J.; Weldon, R. J.; Schmidt, D. A.; Williams, T. B.

    2012-12-01

    . We will also present our analysis of the existing NGS historical dataset on the southern edge of the subduction domain. Preliminary analysis of the major north-south and east-west leveling routes through northwestern California suggest that the Humboldt Bay area is experiencing tectonic subsidence at rates of up to 2 mm/yr. This is consistent with the rapid (~ 4 mm/yr) rate of relative sea level rise observed at the North Spit tide gauge. The northern California leveling data show a peak in uplift inland, in contrast to central and northern Cascadia, where the peak in uplift is near the coast or offshore. Interseismic subsidence of the coast in the Humboldt area is consistent with the locked zone extending east of the coastline, in contrast to what is observed in Oregon where the locked zone is offshore, and corresponds to an area of active onshore thrust faults. With a complete archive of the NGS data for this area, we will present refined estimates of vertical deformation rates tied to an absolute sea level reference at the North Spit tide gauge. These improved datasets will better resolve the distribution of locking along the Cascadia margin as we integrate the vertical observations with GPS-derived constraints of horizontal strain rates in an elastic model of interseismic subduction deformation.

  17. Far-UV Eclipse Observations of Ganymede's Atmosphere with New Horizons Alice: New Constraints to the Atomic Oxygen Component

    NASA Astrophysics Data System (ADS)

    Retherford, K. D.; Steffl, A. J.; Spencer, J. R.; Gladstone, R.; Roth, L.; Saur, J.; Strobel, D. F.; Stern, S. A.; Parker, J. W.; Versteeg, M. H.; Davis, M. W.; Cunningham, N. J.; McGrath, M. A.

    2014-12-01

    Ganymede's atmosphere is a surface-bounded-exosphere composed mainly of molecular oxygen. The bulk density of the O2 atmosphere is inferred from the diagnostic ratio between far-UV auroral emission line brightnesses observed with the Hubble Space Telescope (HST), but this measurement is relatively uncertain owing to a lack of information available for the energies of the electrons in Ganymede's magnetosphere that dissociatively excite the OI 130.4 nm and 135.6 nm emissions. Only a few other species such as H have been detected, and the abundance of atomic oxygen has been constrained only in relation to lower limits for the O2 density based on the line ratios. The New Horizons (NH) spacecraft observed Ganymede with the Pluto-Alice (P-Alice) instrument during the Jupiter flyby in spring of 2007. HST Advanced Camera for Surveys (ACS) far-UV images of Ganymede complement the P-Alice far-UV spectroscopy at this time. OI 130.4 nm and 135.6 nm emissions were detected in both data sets. The ACS Ganymede images are consistent with previous Space Telescope Imaging Spectrograph (STIS) imaging. P-Alice observed two Ganymede eclipse events, viewing the sunlit sub-Jupiter and nightside anti-Jupiter hemispheres, separately, from before ingress through after egress. Through comparisons of the P-Alice spectra in sunlight to those in eclipse we are able to disentangle the component of the OI 130.4 nm emission line brightness attributed to processes other than electron impact dissociation of O2, namely a combination of solar reflectance and solar resonant scattering by atomic oxygen atoms. The CII 133.5 nm solar emission feature in the sunlit hemisphere dataset also disappears in eclipse and was not detected in the nightside hemisphere spectra, as expected, providing distinct fits to the solar reflectance component. We thereby provide the first meaningful constraint on the atomic oxygen atmosphere revealed through the solar resonant scattering emission source. We briefly discuss the

  18. MAGIC observations of the February 2014 flare of 1ES 1011+496 and ensuing constraint of the EBL density

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, A.; Guberman, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Satalecka, K.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.

    2016-05-01

    Context. During February-March 2014, the MAGIC telescopes observed the high-frequency peaked BL Lac 1ES 1011+496 (z = 0.212) in flaring state at very-high energy (VHE, E> 100 GeV). The flux reached a level of more than ten times higher than any previously recorded flaring state of the source. Aims: To describe the characteristics of the flare presenting the light curve and the spectral parameters of the night-wise spectra and the average spectrum of the whole period. From these data we aim to detect the imprint of the extragalactic background light (EBL) in the VHE spectrum of the source, to constrain its intensity in the optical band. Methods: We analyzed the gamma-ray data from the MAGIC telescopes using the standard MAGIC software for the production of the light curve and the spectra. To constrain the EBL, we implement the method developed by the H.E.S.S. collaboration, in which the intrinsic energy spectrum of the source is modeled with a simple function (≤4 parameters), and the EBL-induced optical depth is calculated using a template EBL model. The likelihood of the observed spectrum is then maximized, including a normalization factor for the EBL opacity among the free parameters. Results: The collected data allowed us to describe the night-wise flux changes and also to produce differential energy spectra for all nights in the observed period. The estimated intrinsic spectra of all the nights could be fitted by power-law functions. Evaluating the changes in the fit parameters, we conclude that the spectral shape for most of the nights were compatible, regardless of the flux level, which enabled us to produce an average spectrum from which the EBL imprint could be constrained. The likelihood ratio test shows that the model with an EBL density 1.07 (-0.20, +0.24)stat+sys, relative to the one in the tested EBL template, is preferred at the 4.6σ level to the no-EBL hypothesis, with the assumption that the intrinsic source spectrum can be modeled as a log

  19. The binary near-Earth Asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution

    NASA Astrophysics Data System (ADS)

    Scheirich, P.; Pravec, P.; Jacobson, S. A.; Ďurech, J.; Kušnirák, P.; Hornoch, K.; Mottola, S.; Mommert, M.; Hellmich, S.; Pray, D.; Polishook, D.; Krugly, Yu. N.; Inasaridze, R. Ya.; Kvaratskhelia, O. I.; Ayvazian, V.; Slyusarev, I.; Pittichová, J.; Jehin, E.; Manfroid, J.; Gillon, M.; Galád, A.; Pollock, J.; Licandro, J.; Alí-Lagoa, V.; Brinsfield, J.; Molotov, I. E.

    2015-01-01

    Using our photometric observations taken between April 1996 and January 2013 and other published data, we derived properties of the binary near-Earth Asteroid (175706) 1996 FG3 including new measurements constraining evolution of the mutual orbit with potential consequences for the entire binary asteroid population. We also refined previously determined values of parameters of both components, making 1996 FG3 one of the most well understood binary asteroid systems. With our 17-year long dataset, we determined the orbital vector with a substantially greater accuracy than before and we also placed constraints on a stability of the orbit. Specifically, the ecliptic longitude and latitude of the orbital pole are 266 ° and - 83 ° , respectively, with the mean radius of the uncertainty area of 4 ° , and the orbital period is 16.1508 ± 0.0002 h (all quoted uncertainties correspond to 3σ). We looked for a quadratic drift of the mean anomaly of the satellite and obtained a value of 0.04 ± 0.20 deg /yr2 , i.e., consistent with zero. The drift is substantially lower than predicted by the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J., Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the tigidity and quality factor of μQ = 1.3 ×107 Pa using the theory that assumes an elastic response of the asteroid material to the tidal forces. This very low value indicates that the primary of 1996 FG3 is a 'rubble pile', and it also calls for a re-thinking of the tidal energy dissipation in close asteroid binary systems.

  20. Isotopic outcomes of N-body accretion simulations: Constraints on equilibration processes during large impacts from Hf/W observations

    NASA Astrophysics Data System (ADS)

    Nimmo, F.; Agnor, C. B.

    2006-03-01

    Most estimates of planetary core formation timescales using hafnium-tungsten (Hf-W) isotopes employ analytical expressions assuming either continuous planetary growth or instantaneous core formation. In contrast, dynamical modelling of planetary accretion suggests that the final stage of terrestrial planet formation is punctuated by multiple large and stochastic impacts. Such giant impacts have significant thermal and isotopic consequences. We present a framework for calculating the Hf-W isotope evolution of individual bodies based on the results of an N-body accretion simulation and assuming constant partition coefficients. The results show that smaller bodies exhibit a larger range in isotopic values than larger bodies, because the latter have suffered more impacts. The analytical core formation timescales calculated using these isotopic values can differ very significantly from the timing of the final giant impact each planet actually experiences. Simulations in which 1) even the largest impactors undergo re-equilibration with the target's mantle, rather than the cores merging directly, and 2) the original planetary embryos possessed radially variable iron : silicate ratios, produce results which are consistent with the observed physical and isotopic characteristics of inner solar system bodies. Varying W partition coefficients (due to changing mantle oxidation state) or initial planetesimal Hf / W ratios might produce similar isotopic outcomes, and potentially permit core mergers without violating the isotopic constraints. The style of re-equilibration required suggests that magma oceans were present on Mars-sized and larger bodies; an alternative for bodies of Mars-size and smaller is that the bulk of the mass was delivered as impactors much smaller than the target. For Mars we conclude that a prolonged (˜10 Myr) accretion process is both dynamically and isotopically plausible. We also predict likely Pd-Ag isotopic anomalies for Vesta-, Mars- and Earth

  1. The Beimarang mélange (southern Tibet) brings additional constraints in assessing the origin, metamorphic evolution and obduction processes of the Yarlung Zangbo ophiolite

    NASA Astrophysics Data System (ADS)

    Huot, François; Hébert, Réjean; Varfalvy, Véronika; Beaudoin, Georges; Wang, Chengshan; Liu, Zhifei; Cotten, Jo; Dostal, Jaroslav

    2002-12-01

    The Beimarang massif is one of many ophiolitic remnants which crop out discontinuously along the Yarlung Zangbo suture zone in southern Tibet. The southern contact of these remnants is marked by a highly sheared serpentinite mélange made up of blocks of serpentinites, diabases, gabbros and composite blocks of serpentinites and mafic injections. The Beimarang mélange has been investigated in order to bring additional constraints on the origin, metamorphic evolution and obduction processes of the Yarlung Zangbo ophiolite. Petrography and geochemical data suggest that the ultramafic components are similar to moderately depleted upper mantle peridotites. They may represent the already cooled and serpentinized Tethyan upper mantle which was trapped in a mantle wedge at the onset of a north-dipping Early Cretaceous intra-oceanic subduction zone located south of the Gangdese arc. These peridotites were then intruded by back-arc-like mafic magmas whose moderately depleted mantle source was affected by a subduction component. Ultramafic and mafic secondary mineral assemblages suggest that early low-( P/ T) metamorphic intra-oceanic conditions reached the amphibolite facies (>550 °C) before being retrograded down to the pumpellyite-prehnite facies (<280 °C). The Beimarang mélange, interpreted as an obduction mélange formed near a spreading ridge, was subjected to metamorphic conditions in the pumpellyite-prehnite facies which favored re-serpentinization of the peridotites and partial rodingitization of the mafic rocks. Unlike subduction-related mélanges and their associated lithological units found in the Ladakh area, we found no evidence of high-( P/ T) conditions in lithologies from the Beimarang mélange.

  2. Observational Constraints on the Progenitors of Core-Collapse Supernovae: The Case for Missing High-Mass Stars

    NASA Astrophysics Data System (ADS)

    Smartt, S. J.

    2015-04-01

    explodability for stars in the 8-120 M⊙ range.The observational constraints are quite consistent with the bulk of stars above M ≳ 18 M⊙ collapsing to form black holes with no visible supernovae.

  3. CONSTRAINTS ON LONG-PERIOD PLANETS FROM AN L'- AND M-BAND SURVEY OF NEARBY SUN-LIKE STARS: OBSERVATIONS

    SciTech Connect

    Heinze, A. N.; Hinz, Philip M.; Sivanandam, Suresh; Kenworthy, Matthew; Miller, Douglas; Meyer, Michael E-mail: phinz@as.arizona.ed E-mail: mkenworthy@as.arizona.ed E-mail: mmeyer@phys.ethz.c

    2010-05-10

    We present the observational results of an L'- and M-band adaptive optics imaging survey of 54 nearby, Sun-like stars for extrasolar planets, carried out using the Clio camera on the MMT. We have concentrated more strongly than all other planet-imaging surveys to date on very nearby F, G, and K stars, prioritizing stellar proximity higher than youth. Ours is also the first survey to include extensive observations in the M band, which supplement the primary L' observations. Models predict much better planet/star flux ratios at the L' and M bands than at more commonly used shorter wavelengths (i.e., the H band). We have carried out extensive blind simulations with fake planets inserted into the raw data to verify our sensitivity, and to establish a definitive relationship between source significance in {sigma} and survey completeness. We find 97% confident-detection completeness for 10{sigma} sources, but only 46% for 7{sigma} sources-raising concerns about the standard procedure of assuming high completeness at 5{sigma}, and demonstrating that blind sensitivity tests to establish the significance-completeness relation are an important analysis step for all planet-imaging surveys. We discovered a previously unknown {approx}0.15 M{sub sun} stellar companion to the F9 star GJ 3876, at a projected separation of about 80 AU. Twelve additional candidate faint companions are detected around other stars. Of these, 11 are confirmed to be background stars and one is a previously known brown dwarf. We obtained sensitivity to planetary-mass objects around almost all of our target stars, with sensitivity to objects below 3 M{sub Jup} in the best cases. Constraints on planet populations based on this null result are presented in our Modeling Results paper.

  4. The GC-MS Observation of Intermediates in a Stepwise Grignard Addition Reaction

    ERIC Educational Resources Information Center

    Latimer, Devin

    2007-01-01

    Preparation of phenylmagnesium bromide described by Eckert, addition of three equivalents of Grignard reagent to diethyl carbonate to form triphenylmethanol and a series of GC-MS procedures that form intermediates. The analysis is consistent with a gas chromatogram and mass spectrum for each of the expected intermediates and final product of the…

  5. Strong constraints on a super-Eddington accretion flow: XMM-Newton observations of an intermediate-mass black hole

    NASA Astrophysics Data System (ADS)

    Jin, Chichuan; Done, Chris; Ward, Martin

    2016-01-01

    RX J1140.1+0307 is a Narrow Line Seyfert 1 (NLS1) with one of the lowest black hole masses known in an AGN (M ≤ 106 M⊙). We show results from two new XMM-Newton observations, exhibiting soft 2-10 keV spectra, a strong excess at lower energies, and fast X-ray variability which is typical of this class of AGN. The soft excess can be equally well fit using either low-temperature Comptonization or highly smeared, ionized reflection models, but we additionally consider the fast X-ray variability to produce covariance, lag and coherence spectra to show that the low-temperature Comptonization model gives a better description of the break in variability properties between soft and hard X-rays. Both these models require an additional component at the softest energies, as expected from the accretion disc. However, standard disc models cannot connect this to the optical/UV emission from the outer disc unless the mass is underestimated by an order of magnitude. The variable optical and far UV emission instead suggests that L/LEdd ˜ 10 through the outer disc, in which case advection and/or wind losses are required to explain the observed broad-band spectral energy distribution. This implies that the accretion geometry close to the black hole is unlikely to be a flat disc as assumed in the recent X-ray reverberation mapping techniques.

  6. Early Additional Immune-Modulators for Mycoplasma pneumoniae Pneumonia in Children: An Observation Study

    PubMed Central

    Lee, Sung-Churl; Rhim, Jung-Woo; Shin, Myung-Seok; Kang, Jin-Han

    2014-01-01

    Background Mycoplasma pneumoniae (MP) pneumonia is a self-limiting disease, but some patients complain of progressive pneumonia, despite of appropriate antibiotic treatment. We aimed to introduce the role of immune-modulators (corticosteroid and/or intravenous immunoglobulin, IVIG) treatment for childhood MP pneumonia based on previous our experiences. Materials and Methods A retrospective case series analysis for 183 children with MP pneumonia was performed. MP pneumonia patients were diagnosed by two Immunoglobulin M (IgM) tests: the micro-particle agglutination method (≥1:40) and the cold agglutination test (≥1:4), and were examined twice at the initial admission and at discharge. Among 183 MP pneumonia patients, 90 patients with persistent fever for over 48 hours after admission or those with severe respiratory symptoms and signs received additional prednisolone (82 patients, 1 mg/kg/day) or intravenous methylprednisolone (8 patients, 5-10 mg/kg/day) with antibiotics. Four patients with aggravated clinical symptoms and chest radiographic findings after corticosteroid treatment received IVIG (1 g/kg/day, 1-2 doses). Results Mean age of 183 patients was 5.5 ± 3.2 years (6 months-15 years), and the male: female ratio was 1.1:1 (96:87). Fifty-seven patients (31%) were seroconverters and 126 seropositive patients showed increased diagnostic IgM antibody titres during admission (over 4 folds). The majority of the patients who received corticosteroids (86/90 cases) showed rapid defervescence within 48 hours with improved clinical symptoms, regardless of the used antibiotics. Also, 4 patients who received additional IVIG improved both clinically and radiographically within 2 days without adverse reaction. Conclusions In the era of macrolide-resistant MP strains, early additional immune-modulator therapy with antibiotics might prevent from the disease progression and reduce the disease morbidity without adverse reaction. PMID:25566403

  7. Recursive ideal observer detection of known M-ary signals in multiplicative and additive Gaussian noise.

    NASA Technical Reports Server (NTRS)

    Painter, J. H.; Gupta, S. C.

    1973-01-01

    This paper presents the derivation of the recursive algorithms necessary for real-time digital detection of M-ary known signals that are subject to independent multiplicative and additive Gaussian noises. The motivating application is minimum probability of error detection of digital data-link messages aboard civil aircraft in the earth reflection multipath environment. For each known signal, the detector contains one Kalman filter and one probability computer. The filters estimate the multipath disturbance. The estimates and the received signal drive the probability computers. Outputs of all the computers are compared in amplitude to give the signal decision. The practicality and usefulness of the detector are extensively discussed.

  8. Additional observations and notes on the natural history of the prairie rattlesnake (Crotalus viridis) in Colorado.

    PubMed

    Fitzgerald, Kevin T; Shipley, Bryon K; Newquist, Kristin L; Vera, Rebecca; Flood, Aryn A

    2013-11-01

    On account of their unique anatomy, physiology, natural history, ecology, and behavior, rattlesnakes make ideal subjects for a variety of different scientific disciplines. The prairie rattlesnake (Crotalus viridis) in Colorado was selected for investigation of its relationship to colonies of black-tailed prairie dogs (Cynomys ludovicianus) with regard to spatial ecology. A total of 31 snakes were anesthetized and had radiotransmitters surgically implanted. In addition, at the time of their capture, all snakes underwent the following: (1) they had bacterial culture taken from their mouths for potential isolation of pathogenic bacteria; (2) similarly, they had cloacal bacterial cultures taken to assess potentially harmful bacteria passed in the feces; and (3) they had blood samples drawn to investigate the presence of any zoonotic agents in the serum of the snakes. The results of the study and their implications are discussed here. Traditionally, a low incidence of bacterial wound infection has been reported following snakebite. Nevertheless, the oral cavity of snakes has long been known to house a wide variety of bacterial flora. In our study, 10 different bacterial species were isolated from the mouths of the rattlesnakes, 6 of which are capable of being zoonotic pathogens and inducing human disease. More studies are necessary to see why more rattlesnake bites do not become infected despite the presence of such pathogenic bacteria. The results of fecal bacteria isolated revealed 13 bacterial species, 12 of which can cause disease in humans. Of the snakes whose samples were cultured, 26% were positive for the presence of the pathogen Salmonella arizonae, one of the causative agents of reptile-related salmonellosis in humans. It has long been reported that captive reptiles have a much higher incidence than wild, free-ranging species. This study shows the incidence of Salmonella in a wild, free-ranging population of rattlesnakes. In addition, Stenotrophomonas

  9. Observations of mass addition to the shocked solar wind of the Venusian ionosheath

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.

    1982-01-01

    The present investigation constitutes a continuation of a study conducted by Mihalov et al. (1980) concerning the heavy ion component in the plasma observations downstream from Venus, taking into account data obtained with the aid of the plasma analyzer experiment on the Pioneer Venus Orbiter (PVO). The current study is based on analyses of the first season of PVO orbits with apoapsis in the tail and provides clear evidence for the presence of heavy ions. It is found that a heavy ion component was added to the ionosheath flow for a prolonged period on June 8 and 11, 1979 while the spacecraft was downstream from the planet. The heavy ions are identified as oxygen ions O(+). Heavy ions are detected on most of the orbits in the first season or apoapsis tail passages.

  10. New Constraints on Dark Energy from Chandra X-rayObservations of the Largest Relaxed Galaxy Clusters

    SciTech Connect

    Allen, S.W.; Rapetti, D.A.; Schmidt, R.W.; Ebeling, H.; Morris, G.; Fabian, A.C.; /Cambridge U., Inst. of Astron.

    2007-06-06

    We present constraints on the mean matter density, {Omega}{sub m}, dark energy density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and mean baryon density, {Omega}{sub b}h{sup 2}). Analyzing the data for all 42 clusters, employing only weak priors on H{sub 0} and {Omega}{sub b}h{sup 2}, we obtain a similar result on {Omega}{sub m} and detect the effects of dark energy on the distances to the clusters at {approx}99.99% confidence, with {Omega}{sub DE}=0.86{+-}0.21 for a non-flat LCDM model. The detection of dark energy is comparable in significance to recent SNIa studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the f{sub gas} data, despite a weighted mean statistical scatter in the distance measurements of only {approx}5%. For a flat cosmology with constant w, we measure {Omega}{sub m}=0.28{+-}0.06 and w=-1.14{+-}0.31. Combining the fgas data with independent constraints from CMB and SNIa studies removes the need for priors on {Omega}{sub b}h{sup 2} and H{sub 0} and leads to tighter constraints: {Omega}{sub m}=0.253{+-}0.021 and w=-0.98{+-}0.07 for the same constant-w model. More general analyses in which we relax the assumption of flatness and/or allow evolution in w remain consistent with the cosmological constant paradigm. Our analysis includes conservative allowances for systematic uncertainties. The small systematic scatter and tight constraints bode well for future dark energy studies using the f{sub gas} method.

  11. Observational Constraints on Terpene Oxidation with and without Anthropogenic Influence in the Amazon using Speciated Measurements from SV-TAG

    NASA Astrophysics Data System (ADS)

    Yee, L.; Isaacman, G. A.; Kreisberg, N. M.; Liu, Y.; McKinney, K. A.; de Sá, S. S.; Martin, S. T.; Alexander, M. L.; Palm, B. B.; Hu, W.; Campuzano Jost, P.; Day, D. A.; Jimenez, J. L.; Viegas, J.; Springston, S. R.; Wurm, F.; Ferreira De Brito, J.; Artaxo, P.; Manzi, A. O.; Machado, L.; Longo, K.; Oliveira, M. B.; Souza, R. A. F. D.; Hering, S. V.; Goldstein, A. H.

    2014-12-01

    Biogenic volatile organic compounds (BVOCs) from the Amazon forest represent the largest regional source of organic carbon emissions to the atmosphere. These BVOC emissions dominantly consist of volatile and semi-volatile terpenoid compounds that undergo chemical transformations in the atmosphere to form oxygenated condensable gases and secondary organic aerosol (SOA). However, the oxidation pathways of these compounds are still not well understood, and are expected to differ significantly between "pristine" conditions, as is common in Amazonia, and polluted conditions caused by emissions from growing cities. Our focus is to elucidate how anthropogenic emissions influence BVOC chemistry and BSOA formation through speciated measurements of their oxidation products. We have deployed the Semi-Volatile Thermal desorption Aerosol Gas Chromatograph (SV-TAG) at the rural T3 site located west of the urban center of Manaus, Brazil as part of the Green Ocean Amazon (GoAmazon) 2014 field campaign to measure hourly concentrations of semi-volatile BVOCs and their oxidation products during the wet and dry seasons. Primary BVOC concentrations measured by the SV-TAG include sesquiterpenes and diterpenes, which have rarely been speciated with high time-resolution. We observe sesquiterpenes to be anti-correlated with ozone, indicative of sesquiterpene oxidation playing a major role in the regional oxidant budget. The role of sesquiterpenes in atmospheric SOA formation are of interest due to their high aerosol yields and high reactivity with ozone, relative to more commonly measured BVOCs (e.g. monoterpenes). We explore relative concentrations of sesquiterpenes and monoterpenes and their roles as precursors to SOA formation by combining SV-TAG measurements with those from an additional suite of VOC and particle measurements deployed in the Amazon. We also report the first ever hourly observations of the gas-particle partitioning of speciated terpene oxidation products in the Amazon

  12. Observational Constraints on Atmospheric and Oceanic Cross-Equatorial Heat Transports: Revisiting the Precipitation Asymmetry Problem in Climate Models

    NASA Astrophysics Data System (ADS)

    Loeb, N. G.; Wang, H.; Cheng, A.; Kato, S.; Fasullo, J.; Xu, K. M.; Allan, R. P.

    2015-12-01

    Recent studies have shown strong linkages between hemispheric asymmetries in atmospheric and oceanic energy budgets, tropical precipitation and the mean position of the Intertropical Convergence Zone (ITCZ). The energetics framework has been used to explain why the mean position of the ITCZ is in the Northern Hemisphere and to study large-scale circulation and precipitation responses to changes in the hemispheric distribution of heating. Here, we expand upon these earlier studies by also considering estimates of hemispheric asymmetry in surface and atmospheric radiation budget derived from satellite observations, which enables a decomposition of cross-equatorial heat transport in terms of radiative and non-radiative (i.e., combined latent and sensible heat) components. Satellite observations of top-of-atmosphere (TOA) and surface radiation budget from the Clouds and the Earth's Radiation Budget (CERES) are combined with mass corrected vertically integrated atmospheric energy divergence from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Observed radiative and combined sensible and latent heat contributions to atmospheric and oceanic cross-equatorial heat transports are compared with simulations from 30 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results show that most CMIP5 models that overestimate tropical precipitation in the SH have too much net downward surface radiation and combined latent and sensible heat flux in the SH relative to the NH. In addition, many of the models also underestimate atmospheric radiative cooling in the SH compared to the NH. Consequently, the models have excessive heating of the SH atmosphere and anomalous SH to NH cross-equatorial heat transport. The anomalous northward heat transport occurs via the upper branch of the northern Hadley Cell, while anomalous NH to SH moisture transport occurs in the lower branch of the northern

  13. Constraints on energy release in solar flares from RHESSI and GOES X-ray observations. I. Physical parameters and scalings

    NASA Astrophysics Data System (ADS)

    Warmuth, A.; Mann, G.

    2016-04-01

    component (≈10-25 MK) that is generated by chromospheric evaporation caused by a nonthermal electron beam. In addition, a hotter component (≥25 MK) is only detected by RHESSI; this component is more consistent with direct in situ heating of coronal plasma. With the exception of the early impulsive phase, RHESSI observes a combination of the evaporated and the directly heated component.

  14. Additional spectroscopic observations and Swift monitoring of the M31 nova iPTF16bqy (ASASSN-16hf)

    NASA Astrophysics Data System (ADS)

    Chinetti, K.; Darnley, M. J.; Page, K. L.; Williams, S. C.

    2016-08-01

    We report additional spectroscopic observations of the M31 nova, iPTF16bqy (ASASSN-16hf, ATels #9245, #9248). iPTF16bqy was initially classified as a Fe II nova based on spectra obtained 2016 July 14 and 15 (ATel #9248), about two days after discovery.

  15. Foreland segmentation along an active convergent margin: New constraints in southeastern Sicily (Italy) from seismic and geodetic observations

    NASA Astrophysics Data System (ADS)

    Musumeci, Carla; Scarfì, Luciano; Palano, Mimmo; Patanè, Domenico

    2014-09-01

    We performed an in-depth analysis of the ongoing tectonics of a large sector of southern Sicily, including the Hyblean Foreland and the front of the Maghrebian Chain, as well as the Ionian Sea offshore, through the integration of seismic and GPS observations collected in the nearly two decades. In particular, a dataset consisting of more than 1100 small-to moderate-magnitude earthquakes (1.0 ≤ ML ≤ 4.6) has been used for local earthquake tomography in order to trace the characteristics of the faulting systems, and for focal mechanisms computation to resolve the current local stress field and to characterise the faulting regime of the investigated area. In addition, GPS measurements, carried out on both episodic and continuous stations, allowed us to infer the main features of the current crustal deformation pattern. Main results evidence that the Hyblean Plateau is subject to a general strike-slip faulting regime, with a maximum horizontal stress axis NW-SE to NNW-SSE oriented, in agreement with the Eurasia-Nubia direction of convergence. The Plateau is separated into two different tectonic crustal blocks by the left-lateral strike-slip Scicli-Ragusa Fault System. The western block moves in agreement with central Sicily while the eastern one accommodates part of the contraction arising from the main Eurasia-Nubia convergence. Furthermore, we provided evidences leading to consider the Hyblean-Maltese Escarpment Fault System as an active boundary characterised by a left-lateral strike-slip motion, separating the eastern block of the Plateau from the Ionian basin. All these evidences lend credit to a crustal segmentation of the southeastern Sicily.

  16. CONSTRAINTS ON THE GALACTIC POPULATION OF TeV PULSAR WIND NEBULAE USING FERMI LARGE AREA TELESCOPE OBSERVATIONS

    SciTech Connect

    Acero, F.; Brandt, T. J.; Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Buehler, R.; Baldini, L.; Ballet, J.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bonamente, E.; Brigida, M.; Bruel, P. E-mail: joshualande@gmail.com E-mail: rousseau@cenbg.in2p3.fr [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS and others

    2013-08-10

    Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV {gamma}-ray emitters. Since launch, the Fermi Large Area Telescope (LAT) has identified five high-energy (100 MeV < E < 100 GeV) {gamma}-ray sources as PWNe and detected a large number of PWN candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV {gamma}-ray unidentified (UNID) sources are the best candidates for finding new PWNe. Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58 TeV PWNe and UNIDs within 5 Degree-Sign of the Galactic plane to establish new constraints on PWN properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their {gamma}-ray fluxes for energies above 10 GeV. The spectral energy distributions and upper limits, in the multi-wavelength context, also provide new information on the source nature and can help distinguish between emission scenarios, i.e., between classification as a pulsar candidate or as a PWN candidate. Six new GeV PWN candidates are described in detail and compared with existing models. A population study of GeV PWN candidates as a function of the pulsar/PWN system characteristics is presented.

  17. Cosmological constraints from the observed angular cross-power spectrum between Sunyaev-Zel'dovich and X-ray surveys

    NASA Astrophysics Data System (ADS)

    Hurier, G.; Douspis, M.; Aghanim, N.; Pointecouteau, E.; Diego, J. M.; Macias-Perez, J. F.

    2015-04-01

    We present the first detection of the cross-correlation angular power spectrum between the thermal Sunyaev-Zel'dovich (tSZ) effect and the X-ray emission over the full sky. The tSZ effect and X-rays are produced by the same hot gas within groups and clusters of galaxies, which creates a naturally strong correlation between them that can be used to boost the joint signal and derive cosmological parameters. We computed the correlation between the ROSAT All Sky Survey in the 0.5-2 keV energy band and the tSZ effect reconstructed from six Planck all-sky frequency maps between 70 and 545 GHz. We detect a significant correlation over a wide range of angular scales. In the range 50 <ℓ< 2000, the cross-correlation of X-rays to tSZ is detected at an overall significance of 28σ. As part of our systematic study, we performed a multi-frequency modelling of the AGN contamination and the correlation between cosmic infra-red background and X-rays. Taking advantage of the strong dependence of the cross-correlation signal on the amplitude of the power spectrum, we constrained σ8 = 0.804 ± 0.037, where modelling uncertainties dominate statistical and systematic uncertainties. We also derived constraints on the mass indices of scaling relations between the halo mass and X-ray luminosity, L500 - M500, and SZ signal, Y500 - M500, asz + ax = 3.37 ± 0.09, and on the indices of the extra-redshift evolution, βsz + βx = 0.4+0.4_{-0.5}.

  18. Highly irregular quantum constraints

    NASA Astrophysics Data System (ADS)

    Klauder, John R.; Little, J. Scott

    2006-05-01

    Motivated by a recent paper of Louko and Molgado, we consider a simple system with a single classical constraint R(q) = 0. If ql denotes a generic solution to R(q) = 0, our examples include cases where R'(ql) ≠ 0 (regular constraint) and R'(ql) = 0 (irregular constraint) of varying order as well as the case where R(q) = 0 for an interval, such as a <= q <= b. Quantization of irregular constraints is normally not considered; however, using the projection operator formalism we provide a satisfactory quantization which reduces to the constrained classical system when planck → 0. It is noteworthy that irregular constraints change the observable aspects of a theory as compared to strictly regular constraints.

  19. One component metal sintering additive for {beta}-SiC based on thermodynamic calculation and experimental observations

    SciTech Connect

    Noviyanto, Alfian; Yoon, Dang-Hyok

    2011-08-15

    Graphical abstract: . Standard Gibbs formation free energies vs. temperature for various metal carbides. The heavy line represents the standard Gibbs free energy for {beta}-SiC. The hatched area denotes the typical liquid phase hot pressing temperature of {beta}-SiC (1973-2123 K). Highlights: {yields} Various metal elements were examined as a sintering additive for {beta}-SiC. {yields} Al and Mg enhanced the density significantly without decomposing {beta}-SiC, as predicted by thermodynamic simulation. {yields} Cr, Fe, Ta, Ti, V and W additives formed metal carbide and/or silicide compounds by decomposing {beta}-SiC. {yields} This approach would be useful for selecting effective sintering additive for high temperature ceramics. -- Abstract: Various types of metals were examined as sintering additives for {beta}-SiC by considering the standard Gibbs formation free energy and vapor pressure under hot pressing conditions (1973-2123 K), particularly for applications in nuclear reactors. Metallic elements having the low long-term activation under neutron irradiation condition, such as Cr, Fe, Ta, Ti, V and W, as well as widely used elements, Al, Mg and B, were considered. The conclusions drawn from thermodynamic considerations were compared with the experimental observations. Al and Mg were found to be effective sintering additives, whereas the others were not due to the formation of metal carbides or silicides from the decomposition of SiC under hot pressing conditions.

  20. Lunar Pickup Ions Observed by ARTEMIS: Spatial and Temporal Distribution and Constraints on Species and Source Locations

    NASA Technical Reports Server (NTRS)

    Halekas, Jasper S.; Poppe, A. R.; Delory, G. T.; Sarantos, M.; Farrell, W. M.; Angelopoulos, V.; McFadden, J. P.

    2012-01-01

    ARTEMIS observes pickup ions around the Moon, at distances of up to 20,000 km from the surface. The observed ions form a plume with a narrow spatial and angular extent, generally seen in a single energy/angle bin of the ESA instrument. Though ARTEMIS has no mass resolution capability, we can utilize the analytically describable characteristics of pickup ion trajectories to constrain the possible ion masses that can reach the spacecraft at the observation location in the correct energy/angle bin. We find that most of the observations are consistent with a mass range of approx. 20-45 amu, with a smaller fraction consistent with higher masses, and very few consistent with masses below 15 amu. With the assumption that the highest fluxes of pickup ions come from near the surface, the observations favor mass ranges of approx. 20-24 and approx. 36-40 amu. Although many of the observations have properties consistent with a surface or near-surface release of ions, some do not, suggesting that at least some of the observed ions have an exospheric source. Of all the proposed sources for ions and neutrals about the Moon, the pickup ion flux measured by ARTEMIS correlates best with the solar wind proton flux, indicating that sputtering plays a key role in either directly producing ions from the surface, or producing neutrals that subsequently become ionized.

  1. Paraná-Etendeka lithosphere modeling according to GOCE observations and geophysical constraints: improvement of PERLA project

    NASA Astrophysics Data System (ADS)

    Mariani, Patrizia; Braitenberg, Carla

    2015-04-01

    mineral samples. Also the age of the mantle is included, according to the standard petrological classification of mantle with the percentages of four lead minerals: Olivine, Orthopyroxene, Clinopyroxene and Garnet. Studying the GOCE gravimetric data with the integration of geophysical and also petrological constraints is useful to investigate the lithosphere and to improve the geodynamics of complex geologic areas like LIPs.

  2. Constraints on the Upper Crustal Magma Reservoir Beneath Yellowstone Lake Inferred From Lake-Seiche Induced Strain Observations

    NASA Astrophysics Data System (ADS)

    Luttrell, K. M.; Mencin, D.; Francis, O.; Hurwitz, S.; Hodgkinson, K. M.; Kinsey, S.

    2012-12-01

    Periodic seiches with an ~80-minute period and wave heights up to 10 cm are observed in Yellowstone Lake. Though small, these water level variations act as a load on the solid earth that has been observed on highly sensitive borehole strainmeters throughout Yellowstone National Park. In particular, we observe no time delay (five minutes or less) between the appearance of a seiche signal at a close strainmeter (100 m from the lake edge) and a distant strainmeter (20 km away). The amplitude, timing, and spatial distribution of the observed strain response relative to the observed water load can be used to infer the mechanical characteristics of the subsurface. We calculate the strain field induced by the load of Yellowstone Lake seiches using an elastic half-space model that represents the upper few kilometers of solid crust. We determine that the predicted far-field strain response is much smaller (by more than an order of magnitude) than the measured strain at locations that are distant from the lake. This indicates that far-field strain induced by lake seiches may be sensitive to the location and composition of the crustal magma reservoir. To constrain the depth and viscosity of this reservoir, we calculate the strain field induced in a layered viscoelastic half-space using a semi-analytic model. We find that a magma reservoir must be at least 4 km deep with a Maxwell viscosity of less than 1011 Pa s. The best-fitting depth to the top of an idealized magma chamber is 5-6 km. These new strain observations provide independent evidence for the likely presence of a partially molten body at shallow depth. Continuing observations can provide a valuable contribution to the monitoring and improved understanding of the Yellowstone magmatic system.

  3. Constraints on the upper crustal magma reservoir beneath Yellowstone Caldera inferred from lake-seiche induced strain observations

    USGS Publications Warehouse

    Luttrell, Karen; Mencin, David; Francis, Oliver; Hurwitz, Shaul

    2013-01-01

    Seiche waves in Yellowstone Lake with a ~78-minute period and heights 11 Pa s. These strain observations and models provide independent evidence for the presence of partially molten material in the upper crust, consistent with seismic tomography studies that inferred 10%–30% melt fraction in the upper crust.

  4. GEOPHYSICS, ASTRONOMY AND ASTROPHYSICS: Observational constraints on the accelerating universe in the framework of a 5D bounce cosmological model

    NASA Astrophysics Data System (ADS)

    Lü, Jian-Bo; Xu, Li-Xin; Liu, Mo-Lin; Gui, Yuan-Xing

    2009-04-01

    In the framework of a five-dimensional (5D) bounce cosmological model, a useful function f(z) is obtained by giving a concrete expression of deceleration parameter Then using the obtained Hubble parameter H(z) according to the function f(z), we constrain the accelerating universe from recent cosmic observations: the 192 ESSENCE SNe Ia and the 9 observational H(z) data. The best fitting values of transition redshift ZT and current deceleration parameter qo are given as . Furthermore, in the 5D bounce model it can be seen that the evolution of equation of state (EOS) for dark energy wde can cross over -1 at about z = 0.23 and the current value w0de = -1.15 < -1. On the other hand, by giving a concrete expression of model-independent EOS of dark energy wde, in the 5D bounce model we obtain the best fitting values from the recently observed data: the 192 ESSENCE SNe Ia, the observational H(z) data, the 3-year Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Sky Survey (SDSS) baryon acoustic peak and the x-ray gas mass fraction in clusters.

  5. Regional and Local Influences on Surface O3 over Beijing: Constraints from Integrated Surface observations and Modeling

    NASA Astrophysics Data System (ADS)

    Wang, Y.; McElroy, M. B.; Munger, W.; Hao, J.; Ma, H.; Chen, Y.

    2007-05-01

    Beijing, the Chinese capital, faces the challenge of improving its atmospheric environment while seeing an annual growth rate of 15% in the number of personal vehicles on the road. Among many pollutants, surface ozone is of particular concern for Beijing as it will host the "green" Olympics Games in summer 2008. Continuous measurements of surface O3 and CO at Miyun (a rural site 50km northeast of Beijing) in 2006 are analyzed using a 3-dimensional chemical transport model (GEOS-Chem) to improve our understanding of regional and local factors contributing to changes in tropospheric O3 in the Beijing area. The location of the site was selected to sample both clean continental air and pollution included in the plume from Beijing. To our knowledge, this is the first station in mainland China providing continuous measurements of O3 and related species (CO and CO2) over a relatively long period (years). Observations show that O3 peaks in June and September, while CO has a broad maximum in winter. Using updated emissions for China, the model successfully reproduces the seasonal variability in O3, CO, and their correlations observed at Miyun. Regional O3 levels representative of north China are identified from observations using concurrent measurements of CO. Events with daytime peak O3 concentrations exceeding 100 ppb were observed mainly in summer (JJA) and in September. A major discrepancy of the model is an overestimate of O3 in July. Observations show a decrease of 16 ppb in mean (median) O3 from June to July, presumably associated with enhanced precipitation and cloudiness in July. Implications of high levels of O3 for crop production will be discussed.

  6. Quasi-periodic oscillations in accreting magnetic white dwarfs. I. Observational constraints in X-ray and optical

    NASA Astrophysics Data System (ADS)

    Bonnet-Bidaud, J. M.; Mouchet, M.; Busschaert, C.; Falize, E.; Michaut, C.

    2015-07-01

    Quasi-periodic oscillations (QPOs) are observed in the optical flux of some polars with typical periods of 1 to 3 s but none have been observed yet in X-rays where a significant part of the accreting energy is released. QPOs are expected and predicted from shock oscillations. Most of the polars have been observed by the XMM-Newton satellite. We made use of the homogeneous set of observations of the polars by XMM-Newton to search for the presence of QPOs in the (0.5-10 keV) energy range and to set significant upper limits for the brightest X-ray polars. We extracted high time-resolution X-ray light curves by taking advantage of the 0.07 s resolution of the EPIC-PN camera. Among the 65 polars observed with XMM-Newton from 1998 to 2012, a sample of 24 sources was selected on the basis of their counting rate in the PN instrument to secure significant limits. We searched for QPOs using Fast Fourier Transform (FFT) methods and defined limits of detection using statistical tools. Among the sample surveyed, none shows QPOs at a significant level. Upper limits to the fractional flux in QPOs range from 7% to 71%. These negative results are compared to the detailed theoretical predictions of numerical simulations based on a 2D hydrodynamical code presented in Paper II. Cooling instabilities in the accretion column are expected to produce shock quasi-oscillations with a maximum amplitude reaching ~40% in the bremsstrahlung (0.5-10 keV) X-ray emission and ~20% in the optical cyclotron emission. The absence of X-ray QPOs imposes an upper limit of ~(5-10) g cm-2 s-1 on the specific accretion rate but this condition is found inconsistent with the value required to account for the amplitudes and frequencies of the observed optical QPOs. This contradiction outlines probable shortcomings with the shock instability model. Figures 1-3 are available in electronic form at http://www.aanda.org

  7. Dust variations in the diffuse interstellar medium: constraints on Milky Way dust from Planck-HFI observations

    NASA Astrophysics Data System (ADS)

    Ysard, N.; Köhler, M.; Jones, A.; Miville-Deschênes, M.-A.; Abergel, A.; Fanciullo, L.

    2015-05-01

    Context. The Planck-HFI all-sky survey from 353 to 857 GHz combined with the IRAS data at 100 μm (3000 GHz, IRIS version of the data) show that the dust properties vary from line of sight to line of sight in the diffuse interstellar medium (ISM) at high Galactic latitude (1019 ≤ NH ≤ 2.5 × 1020 H/cm2, for a sky coverage of ~12%). Aims: These observations contradict the usual thinking of uniform dust properties, even in the most diffuse areas of the sky. Thus, our aim is to explain these variations with changes in the ISM properties and with evolution of the grain properties. Methods: Our starting point is the latest core-mantle dust model. This model consists of small aromatic-rich carbon grains, larger amorphous carbonaceous grains with an aliphatic-rich core and an aromatic-rich mantle, and amorphous silicates (mixture of olivine and pyroxene types) with Fe/FeS nano-inclusions covered by aromatic-rich carbon mantles. We explore whether variations in the radiation field or in the gas density distribution in the diffuse ISM could explain the observed variations. The dust properties are also varied in terms of their mantle thickness, metallic nano-inclusions, carbon abundance locked in the grains, and size distributions. Results: We show that variations in the radiation field intensity and gas density distribution cannot explain variations observed with Planck-HFI but that radiation fields harder than the standard ISRF may participate in creating part of the observed variations. We further show that variations in the mantle thickness on the grains coupled with changes in their size distributions can reproduce most of the observations. We concurrently put a limit on the mantle thickness of the silicates, which should not exceed ~ 10 to 15 nm, and find that aromatic-rich mantles are definitely needed for the carbonaceous grain population with a thickness of at least 5 to 7.5 nm. We also find that changes in the carbon cosmic abundance included in the grains

  8. Geophysical observations of Kilauea Volcano, Hawaii, 2. Constraints on the magma supply during November 1975-September 1977

    USGS Publications Warehouse

    Dzurisin, D.; Anderson, L.A.; Eaton, G.P.; Koyanagi, R.Y.; Lipman, P.W.; Lockwood, J.P.; Okamura, R.T.; Puniwai, G.S.; Sako, M.K.; Yamashita, K.M.

    1980-01-01

    Following a 22-month hiatus in eruptive activity, Kilauea volcano extruded roughly 35 ?? 106 m3 of tholeiitic basalt from vents along its middle east rift zone during 13 September-1 October, 1977. The lengthy prelude to this eruption began with a magnitude 7.2 earthquake on 29 November, 1975, and included rapid summit deflation episodes in June, July, and August 1976 and February 1977. Synthesis of seismic, geodetic, gravimetric, and electrical self-potential observations suggests the following model for this atypical Kilauea eruptive cycle. Rapid summit deflation initiated by the November 1975 earthquake reflected substantial migration of magma from beneath the summit region of Kilauea into the east and southwest rift zones. Simultaneous leveling and microgravity observations suggest that 40-90 ?? 106 m3 of void space was created within the summit magma chamber as a result of the earthquake. If this volume was filled by magma from depth before the east rift zone intrusive event of June 1976, the average rate of supply was 6-13 ?? 106 m3/month, a rate that is consistent with the value of 9 ?? 106 m3/month suggested from observations of long-duration Kilauea eruptions. Essentially zero net vertical change was recorded at the summit during the 15-month period beginning with the June 1976 intrusion and ending with the September 1977 eruption. This fact suggests that most magma supplied from depth during this interval was eventually delivered to the east rift zone, at least in part during four rapid summit deflation episodes. Microearthquake epicenters migrated downrift to the middle east rift zone for the first time during the later stages of the February 1977 intrusion, an occurrence presumably reflecting movement of magma into the eventual eruptive zone. This observation was confirmed by tilt surveys in May 1977 that revealed a major inflation center roughly 30 km east of the summit in an area of anomalous steaming and forest kill first noted in March 1976. ?? 1980.

  9. A Deep Chandra Observation of NGC 1404: the Best Constraints on the Transport Processes in the Intracluster Medium

    NASA Astrophysics Data System (ADS)

    Kraft, Ralph P.; Su, Yuanyuan; Nulsen, Paul; Roediger, Elke; Forman, William R.; Churazov, Eugene; Jones, Christine; Randall, Scott W.; Machacek, Marie E.

    2016-04-01

    The intracluster medium, as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics. We present results from the Chandra X-ray observation of NGC 1404, a bright elliptical galaxy falling through the ICM of the Fornax Cluster. The hot, gaseous corona surrounding NGC 1404 is characterized by a sharp upstream edge and a downstream gaseous tail. We resolve the scales of contact discontinuities down to an unprecedented level due to the combination of the proximity of NGC 1404, the superb spatial resolution of Chandra, and a very deep (670 ksec) exposure. We observed Kelvin-Helmholtz instability (KHI) rolls and put an upper limit on the viscosity of hot cluster plasma. We also observed a mixing between the hot cluster gas and the cold galaxy gas in the downstream stripped tail, providing further support of a low viscosity plasma. Across the upstream front, we measured a discontinuity smaller than the mean free path. The magnetic field is strong enough to suppress electron diffusions but weak enough to allow KHI rolls unsuppressed. Our simulation, tailored to the specific scenario, will provide further insight into the details of the transport process.

  10. Constraints from the CMB temperature and other common observational data sets on variable dark energy density models

    NASA Astrophysics Data System (ADS)

    Jetzer, Philippe; Tortora, Crescenzo

    2011-08-01

    The thermodynamic and dynamical properties of a variable dark energy model with density scaling as ρx∝(1+z)m, z being the redshift, are discussed following the outline of Jetzer et al. [P. Jetzer, D. Puy, M. Signore, and C. Tortora, Gen. Relativ. Gravit. 43, 1083 (2011).GRGVA80001-770110.1007/s10714-010-1091-4]. These kinds of models are proven to lead to the creation/disruption of matter and radiation, which affect the cosmic evolution of both matter and radiation components in the Universe. In particular, we have concentrated on the temperature-redshift relation of radiation, which has been constrained using a very recent collection of cosmic microwave background (CMB) temperature measurements up to z˜3. For the first time, we have combined this observational probe with a set of independent measurements (Supernovae Ia distance moduli, CMB anisotropy, large-scale structure and observational data for the Hubble parameter), which are commonly adopted to constrain dark energy models. We find that, within the uncertainties, the model is indistinguishable from a cosmological constant which does not exchange any particles with other components. Anyway, while temperature measurements and Supernovae Ia tend to predict slightly decaying models, the contrary happens if CMB data are included. Future observations, in particular, measurements of CMB temperature at large redshift, will allow to give firmer bounds on the effective equation of state parameter weff of this kind of dark energy model.

  11. Robust constraint on a drifting proton-to-electron mass ratio at z=0.89 from methanol observation at three radio telescopes.

    PubMed

    Bagdonaite, J; Daprà, M; Jansen, P; Bethlem, H L; Ubachs, W; Muller, S; Henkel, C; Menten, K M

    2013-12-01

    A limit on a possible cosmological variation of the proton-to-electron mass ratio μ is derived from methanol (CH3OH) absorption lines in the benchmark PKS1830-211 lensing galaxy at redshift z=0.89 observed with the Effelsberg 100-m radio telescope, the Institute de Radio Astronomie Millimétrique 30-m telescope, and the Atacama Large Millimeter/submillimeter Array. Ten different absorption lines of CH3OH covering a wide range of sensitivity coefficients K(μ) are used to derive a purely statistical 1σ constraint of Δμ/μ=(1.5±1.5)×10(-7) for a lookback time of 7.5 billion years. Systematic effects of chemical segregation, excitation temperature, frequency dependence, and time variability of the background source are quantified. A multidimensional linear regression analysis leads to a robust constraint of Δμ/μ=(-1.0±0.8(stat)±1.0(sys))×10(-7). PMID:24476248

  12. Constraints on the nucleus of comet C/2012 S1 (ISON) from the Hubble Space Telescope observations

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Toth, I.; Li, J.; Weaver, H.

    2014-07-01

    Comet C/2012 S1 (ISON) was both a dynamically new comet, visiting the inner solar system for the first time since being scattered and deeply frozen in the Oort Cloud, and a sungrazing comet. This unique combination made it an attractive target for the Hubble Space Telescope. It was observed on 10 April 2013 when the comet was 4.15 au from the Sun, 4.24 au from the Earth, and at a phase angle of 13.7°, henceforth well before C/ISON crossed the ''snow line'' (2.5--3 au), avoiding strong activity driven by water-ice sublimation and, thus, potentially increasing the chance of detecting its nucleus. The observations were performed over three separate orbits spanning a time interval of 18 hours using the Wide Field Camera 3 (WFC3) UVIS detector to image C/ISON through two broadband filters, the ''wide-V'' F606W and ''blue'' F438W filters (Li at al. 2013). The twelve images obtained with the F606W filter were analyzed using our well-proven technique of fitting a parametric model of the expected surface brightness to the observed images (e.g., Lamy et al. 2006). The model consists of an unresolved point source and a coma specified by a power law, both convolved with the point spread function of the telescope. The nucleus is basically undetected, which imposes an upper limit of its radius of ˜0.3 km. However, the analysis is complicated by the so-called ''breathing'' of the WFC3 camera, an uncontrolled slight defocus which distorts the PSF. We investigated this question in detail and considered various cases of defocus. We will report on this effort and the resulting robust upper limit which we can put on the size of the nucleus of C/ISON.

  13. Constraints on the inclination and masses of the HDE 226868/Cygnus X-1 system from the observations

    NASA Technical Reports Server (NTRS)

    Davis, R.; Hartmann, L.

    1983-01-01

    Analyses of two high-dispersions IUE spectra of HDE 226868 (the optical counterpart of Cygnus X-1) are combined with studies of low-dispersion IUE spectra to provide a more accurate determination of the variation of C IV stellar wind absorption as a function of orbital phase. By incorporating these observational results into an analysis of the structure of the X-ray ionization cavity in the stellar wind, it is found that the orbital inclination must lie between 36 and 67 deg, leading to a mass for the compact object between 5.7 and 11.2 solar masses.

  14. Observational Constraints on Glyoxal Production from Isoprene Oxidation and Its Contribution to Organic Aerosol Over the Southeast United States

    NASA Astrophysics Data System (ADS)

    Li, J.; Mao, J.; Min, K. E.; Washenfelder, R. A.; Brown, S. S.; Kaiser, J.; Keutsch, F. N.; Wolfe, G. M.; Hanisco, T. F.; Pollack, I. B.; Ryerson, T. B.; Graus, M.; Gilman, J.; Lerner, B. M.; Warneke, C.; De Gouw, J. A.; Middlebrook, A. M.; Henderson, B. H.; Paulot, F.; Horowitz, L. W.; Liao, J.; Welti, A.

    2015-12-01

    We use observations from the NOAA Southeast Nexus (SENEX) aircraft campaign, evaluated with a nudged global chemistry-climate model, to better understand the sources and sinks of glyoxal over the Southeast United States. We find that the model with an isoprene oxidation mechanism that does not account for δ-hydroxyl peroxy radicals (δ-ISOPO2), can better reproduce the observed vertical profiles of glyoxal and HCHO, as well as their correlation (RGF) in the continental boundary layer. The suppression of δ-ISOPO2 is consistent with recent theoretical and laboratory studies, reflecting different fates of δ-ISOPO2 under chamber conditions (NO > 100 ppbv) vs. ambient conditions (NO ~ 0.1 ppbv). By including a reactive uptake of glyoxal in the model (γglyx=2.9×10-3), we find that this improves modeled glyoxal in the surface layer but leads to an underestimate of glyoxal above the surface. We estimate an upper limit (1.0 μg/m3) for SOA contributed by glyoxal uptake by aerosols and clouds in the boundary layer of this region. Our work highlights several uncertainties in current chemical mechanisms on glyoxal production from isoprene oxidation under high and low NOx conditions, which may lead to large biases in the estimates of its contribution to SOA formation. Further investigation on these pathways is warranted to quantify the sources and sinks of glyoxal in regional and global scales.

  15. A very Deep Chandra Observation of NGC 1404: the Best Constraints on the Transport Processes in the Intracluster Medium

    NASA Astrophysics Data System (ADS)

    Su, Yuanyuan; Kraft, Ralph P.; Roediger, Elke; Nulsen, Paul; Forman, William R.; Churazov, Eugene; Jones, Christine; Machacek, Marie E.; Randall, Scott W.

    2016-01-01

    The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics. We present results from the Chandra X-ray observation of NGC 1404, a bright elliptical galaxy falling through the ICM of the Fornax Cluster. The hot, gaseous corona surrounding NGC 1404 is characterized by a sharp upstream edge, 8 kpc from the galaxy center, and a downstream gaseous tail, extending 15 kpc behind the galaxy center. We resolve the scales of contact discontinuities down to an unprecedented level due to the combination of the proximity of NGC 1404, the superb spatial resolution of Chandra, and a very deep (670 ksec) exposure. In particular, we measure a temperature discontinuity over a spatial scale of ~ 300 pc (1.5") across the upstream front. We also observe mixing of the downstream tail with the surrounding ICM. We will discuss the implications for ICM transport processes and the interplay between the dynamic motion of the ICM flows and the magnetic fields. Our simulation, tailored to the specific scenario, will provide further insight into the details of the merger process.

  16. Could a 1755-like tsunami reach the French Atlantic coastline? Constraints from 20th century observations and numerical modeling.

    NASA Astrophysics Data System (ADS)

    Allgeyer, S.; Daubord, C.; Hébert, H.; Loevenbruck, A.; Schindelé, F.; Madariaga, R.

    2012-04-01

    The tsunami generated by the 1st November 1755 (Mw ~8.5) earthquake off Portugal affected mainly the coasts of the Iberian Peninsula and Northwest Morocco, and was observed in some places on the North Atlantic coasts, towards the West Indies, but also towards Ireland and the Great Britain, in Cornwall. However, no evidence of observation were found along French Atlantic coastline so far. In a first step, to determine whether there could be effects due to tsunamis on the French coastline, we conducted a study to search for actual tsunamis signals in all historical tide gauge stations of the French Atlantic coast available during the 20th century, specifically for the 1969 and 1975 tsunamis that were well observed in Portugal. Because many recordings are available from the French Hydrographic Service in La Rochelle (west French Atlantic coastline), we focus our study on this harbor. The analysis of these historical tide gauge data shows no evidence for tsunamis in La Rochelle, neither in 1969 or in 1975. Then, to confirm this lack of tsunami, we simulate the tsunamis from the 1969 and 1975 sources, using non linear shallow water equations and a series of imbricated bathymetric grids focusing to the French coastline, and then towards the harbor of La Rochelle: the modeling results confirm unnoticeable amplitudes. In the following step, tsunamis from three different scenarios for the 1755 earthquake have been similarly modeled to estimate the impact of such a tsunami on the French Atlantic coast, with a focus on La Rochelle harbor. The results show that, while the harbor is well protected (amplitudes computed on a synthetic tide gage in the harbor do not exceed 20 to 30 cm crest-to-trough) several areas may have undergone a more important, yet moderate impact, from 0.5 to 1 m, especially in the western part of the island of Ré and the northern coast of the island of Oléron. This may have caused possible local inundations in lowland areas, all the more since the tide

  17. Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

    NASA Technical Reports Server (NTRS)

    Luppino, G. A.; Gioia, I. M.

    1995-01-01

    During the course of a gravitational lensing survey of distant, X-ray selected Einstein Observatory Extended Medium Sensitivity Survey (EMSS) clusters of galaxies, we have studied six X-ray-luminous (L(sub x) greater than 5 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) clusters at redshifts exceeding z = 0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z approximately 0.6 exhibit gravitationally lensed arcs. Furthermore, the highest redshift cluster in our sample, MS 1054-0321 at z = 0.826, is both extremely X-ray luminous (L(sub 0.3-3.5keV)=9.3 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) and exceedingly rich with an optical richness comparable to an Abell Richness Class 4 cluster. In this Letter, we discuss the cosmological implications of the very existence of these clusters for hierarchical structure formation theories such as standard Omega = 1 CDM (cold dark matter), hybrid Omega = 1 C + HDM (hot dark matter), and flat, low-density Lambda + CDM models.

  18. Observational and energetics constraints on the non-conservation of potential/Conservative Temperature and implications for ocean modelling

    NASA Astrophysics Data System (ADS)

    Tailleux, Rémi

    2015-04-01

    This paper seeks to elucidate the fundamental differences between the nonconservation of potential temperature and that of Conservative Temperature, in order to better understand the relative merits of each quantity for use as the heat variable in numerical ocean models. The main result is that potential temperature is found to behave similarly to entropy, in the sense that its nonconservation primarily reflects production/destruction by surface heat and freshwater fluxes; in contrast, the nonconservation of Conservative Temperature is found to reflect primarily the overall compressible work of expansion/contraction. This paper then shows how this can be exploited to constrain the nonconservation of potential temperature and entropy from observed surface heat fluxes, and the nonconservation of Conservative Temperature from published estimates of the mechanical energy budgets of ocean numerical models. Finally, the paper shows how to modify the evolution equation for potential temperature so that it is exactly equivalent to using an exactly conservative evolution equation for Conservative Temperature, as was recently recommended by IOC et al. (2010). This result should in principle allow ocean modellers to test the equivalence between the two formulations, and to indirectly investigate to what extent the budget of derived nonconservative quantities such as buoyancy and entropy can be expected to be accurately represented in ocean models.

  19. CONSTRAINTS ON THE SYNCHROTRON SHOCK MODEL FOR THE FERMI GRB 090820A OBSERVED BY GAMMA-RAY BURST MONITOR

    SciTech Connect

    Burgess, J. Michael; Preece, Robert D.; Briggs, Michael S.; Connaughton, Valerie; Guiriec, Sylvain; Paciesas, William S.; Bhat, P. N.; Chaplin, Vandiver; Goldstein, Adam; Baring, Matthew G.; Meegan, Charles A.; Bissaldi, Elisabetta; Diehl, Roland; Greiner, Jochen; Gruber, David; Fishman, Gerald J.; Gibby, Melissa; Giles, Misty E-mail: baring@rice.edu

    2011-11-01

    Discerning the radiative dissipation mechanism for prompt emission in gamma-ray bursts (GRBs) requires detailed spectroscopic modeling that straddles the {nu}F{sub {nu}} peak in the 100 keV-1 MeV range. Historically, empirical fits such as the popular Band function have been employed with considerable success in interpreting the observations. While extrapolations of the Band parameters can provide some physical insight into the emission mechanisms responsible for GRBs, these inferences do not provide a unique way of discerning between models. By fitting physical models directly, this degeneracy can be broken, eliminating the need for empirical functions; our analysis here offers a first step in this direction. One of the oldest, and leading, theoretical ideas for the production of the prompt signal is the synchrotron shock model. Here we explore the applicability of this model to a bright Fermi gamma-ray burst monitor (GBM) burst with a simple temporal structure, GRB 090820A. Our investigation implements, for the first time, thermal and non-thermal synchrotron emissivities in the RMFIT forward-folding spectral analysis software often used in GBM burst studies. We find that these synchrotron emissivities, together with a blackbody shape, provide at least as good a match to the data as the Band GRB spectral fitting function. This success is achieved in both time-integrated and time-resolved spectral fits.

  20. Constraints on the Synchrotron Shock Model for the Fermi GRB 090820A Observed by Gamma-Ray Burst Monitor

    NASA Astrophysics Data System (ADS)

    Burgess, J. Michael; Preece, Robert D.; Baring, Matthew G.; Briggs, Michael S.; Connaughton, Valerie; Guiriec, Sylvain; Paciesas, William S.; Meegan, Charles A.; Bhat, P. N.; Bissaldi, Elisabetta; Chaplin, Vandiver; Diehl, Roland; Fishman, Gerald J.; Fitzpatrick, Gerard; Foley, Suzanne; Gibby, Melissa; Giles, Misty; Goldstein, Adam; Greiner, Jochen; Gruber, David; van der Horst, Alexander J.; von Kienlin, Andreas; Kippen, Marc; Kouveliotou, Chryssa; McBreen, Sheila; Rau, Arne; Tierney, Dave; Wilson-Hodge, Colleen

    2011-11-01

    Discerning the radiative dissipation mechanism for prompt emission in gamma-ray bursts (GRBs) requires detailed spectroscopic modeling that straddles the νF ν peak in the 100 keV-1 MeV range. Historically, empirical fits such as the popular Band function have been employed with considerable success in interpreting the observations. While extrapolations of the Band parameters can provide some physical insight into the emission mechanisms responsible for GRBs, these inferences do not provide a unique way of discerning between models. By fitting physical models directly, this degeneracy can be broken, eliminating the need for empirical functions; our analysis here offers a first step in this direction. One of the oldest, and leading, theoretical ideas for the production of the prompt signal is the synchrotron shock model. Here we explore the applicability of this model to a bright Fermi gamma-ray burst monitor (GBM) burst with a simple temporal structure, GRB 090820A. Our investigation implements, for the first time, thermal and non-thermal synchrotron emissivities in the RMFIT forward-folding spectral analysis software often used in GBM burst studies. We find that these synchrotron emissivities, together with a blackbody shape, provide at least as good a match to the data as the Band GRB spectral fitting function. This success is achieved in both time-integrated and time-resolved spectral fits.

  1. Observational constraints on atmospheric and oceanic cross-equatorial heat transports: revisiting the precipitation asymmetry problem in climate models

    NASA Astrophysics Data System (ADS)

    Loeb, Norman G.; Wang, Hailan; Cheng, Anning; Kato, Seiji; Fasullo, John T.; Xu, Kuan-Man; Allan, Richard P.

    2016-05-01

    Satellite based top-of-atmosphere (TOA) and surface radiation budget observations are combined with mass corrected vertically integrated atmospheric energy divergence and tendency from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Hemispheric contrasts in the energy budget terms are used to determine the radiative and combined sensible and latent heat contributions to the cross-equatorial heat transports in the atmosphere (AHTEQ) and ocean (OHTEQ). The contrast in net atmospheric radiation implies an AHTEQ from the northern hemisphere (NH) to the southern hemisphere (SH) (0.75 PW), while the hemispheric difference in sensible and latent heat implies an AHTEQ in the opposite direction (0.51 PW), resulting in a net NH to SH AHTEQ (0.24 PW). At the surface, the hemispheric contrast in the radiative component (0.95 PW) dominates, implying a 0.44 PW SH to NH OHTEQ. Coupled model intercomparison project phase 5 (CMIP5) models with excessive net downward surface radiation and surface-to-atmosphere sensible and latent heat transport in the SH relative to the NH exhibit anomalous northward AHTEQ and overestimate SH tropical precipitation. The hemispheric bias in net surface radiative flux is due to too much longwave surface radiative cooling in the NH tropics in both clear and all-sky conditions and excessive shortwave surface radiation in the SH subtropics and extratropics due to an underestimation in reflection by clouds.

  2. Constraints on hot star X-ray source characteristics from combinded analysis of X-ray and UV observations

    NASA Technical Reports Server (NTRS)

    Macfarlane, J. J.

    1994-01-01

    Results from wind ionization calculations are presented which show how the P-Cygni profiles of 'superionized' species such as O VI can provide information about the X-ray source characteristics of early-type stars. Using detailed radiative and atomic physics models, we find that a significant source of X-ray emission from zeta Pup comes from a region in the wind located within rougly 1 to 2 stellar radii of the photosphere. Our results suggest that X-rays sources in which emission occurs exclusively at large radii (r greater than or approximately equal to a few R(sub *)) are inconsistent with UV P-Cygni profiles for O VI. Instead, we find that X-ray emission from shocks distributed throughout the lower regions of the wind (r approximately equal to 1-2 R(sub *)) is consistent with both X-ray and UV data, as well as mass loss rates deduced from radio and H-alpha observations.

  3. Constraints on the minor merging and star formation history of the Wolf-Rayet galaxy NGC 5430 through observations

    NASA Astrophysics Data System (ADS)

    Pan, Hsi-An; Kuno, Nario; Sorai, Kazuo; Umei, Michiko

    2015-12-01

    We used multi-wavelength analysis of the newly observed molecular gas [12CO and 13CO(1-0)] with interferometer CARMA and archival star formation tracers to constrain the interaction, merging, and star formation history of an off-center minor merger, a three-spiral barred galaxy NGC 5430 and its satellite embedded in the bar. Morphology of the molecular gas in the bar of NGC 5430 shows minimal signs of recent interactions with our resolution. The apparent morphological remnant of the past galaxy interaction is an asymmetric spiral arm, containing more molecular gas and exhibiting higher star formation rate (SFR) surface density than the two primary arms. Rotation curve analysis suggests that NGC 5430 collided with its satellite several Gyr ago. History of star formation was constrained by using SFRs that trace different timescales (infrared, radio continuum, and Hα). The collision occurred 5-10 Myr ago, triggering a transient off-center starburst of Wolf-Rayet stars at the eastern bar end. In the past, the global SFR during the Wolf-Rayet starburst peaked at 35 M⊙ yr-1. At present, the merger-driven starburst is rapidly decaying and the current global SFR has decreased to the Galactic value. The SFR will continue to decay as suggested by the present amount of dense gas [traced by HCN(1-0)]. Nonetheless, the global SFR is still dominated by the Wolf-Rayet region rather than the circumnuclear region. Compared with other barred galaxies, the circumnuclear region exhibits a particularly low dense gas fraction, low star formation activity, and high concentration of gas. Physical properties of the molecular gas are inferred by using the large velocity gradient calculations. The initial mass ratio of NGC 5430 to its satellite is suggested to be in an intermediate ratio range of 7:1-20:1.

  4. Could a 1755-Like Tsunami Reach the French Atlantic Coastline? Constraints from Twentieth Century Observations and Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Allgeyer, S.; Daubord, C.; Hébert, H.; Loevenbruck, A.; Schindelé, F.; Madariaga, R.

    2013-09-01

    The tsunami generated by the 1 November, 1755 earthquake off the coast of Portugal affected mainly the coastlines of the Iberian Peninsula and Northwest Morocco, but was also observed in some places along the North Atlantic coasts. To determine whether the event could have effected the French coastline, we conducted a study to search for signs of the tsunami in historical records from all tide gauge stations off the French Atlantic coast during the twentieth century, specifically for the 28 February, 1969 and the 26 May, 1975 tsunamis that were recorded by the Portuguese tide gauge network. Because many recordings are available in La Rochelle (located on the southwest coast of France), we focused our study on this harbor. The analysis of the tide gauge data shows no evidence for tsunamis in La Rochelle, neither in 1969 nor in 1975. To confirm this lack of tsunami signals, we used nonlinear, shallow water equations to compute the tsunami propagation to the French Atlantic coastline for both 1969 and 1975 events. Results obtained from these simulations confirm otherwise unnoticeable wave amplitudes at La Rochelle harbor. In a second step, tsunamis from three different scenarios for the 1755 earthquake were modeled to estimate the impact of such a tsunami on the French Atlantic coast, with a focus on La Rochelle harbor. A comparison of the functions of tide configuration was made in order to analyse the difference in impact. The results show that, while the harbor is poorly impacted, several areas (western part of the island of Ré and northern coast of the island of Oléron) may have experienced a moderate impact from 0.5 to 1 m, especially since the tide was high at the time of arrival, possibly causing local inundations in lowland areas.

  5. Interplanetary dust particles collected in the stratosphere: observations of atmospheric heating and constraints on their interrelationships and sources.

    PubMed

    Sandford, S A; Bradley, J P

    1989-01-01

    The majority of the interplanetary dust particles (IDPs) collected in the stratosphere belong to one of three major classes, the first two dominated by the anhydrous minerals olivine and pyroxene, and the third by hydrous layer-lattice silicates. Infrared spectroscopy and transmission electron microscopy studies show that the different IDP classes represent different types of dust that exist as individual particles in interplanetary space. The majority of the collected IDPs smaller than 30 micrometers in diameter in the layer-lattice silicate and pyroxene classes appear not to have been heated to temperatures above 600 degrees C during atmospheric entry. The relatively low maximum temperatures experienced by these IDPs during atmospheric entry imply that they arrive at the top of the atmosphere with low geocentric encounter velocities. This limits the possible encounter trajectories for these particles to relatively circular, prograde orbits. As a result, it is unlikely that these IDPs are from Earth-crossing comets or asteroids. Asteroids, and comets having low inclinations and perihelia outside 1.2 AU, appear to be the best candidates for the parent bodies of the pyroxene and layer-lattice silicate particles. Chemical and mineralogical information suggests that the pyroxene-rich IDPs are from comets and the layer-lattice silicate-rich IDPs are from asteroids. The collected IDPs dominated by olivine appear to include a larger fraction of particles heating above 600 degrees C, suggesting that these particles were captured from more eccentric orbits. This, and the observation of the infrared spectral features of olivine in several comets suggest these particles have a cometary origin. Since much of the collected dust has apparently been captured from nearly circular, prograde orbits and since there are no appropriate parent bodies presently in such orbits, these results provide an experimental confirmation that the Poynting-Robertson effect exists as a

  6. Cosmological Constraints from Sunyaev-Zel'dovich-selected Clusters with X-Ray Observations in the First 178 deg2 of the South Pole Telescope Survey

    NASA Astrophysics Data System (ADS)

    Benson, B. A.; de Haan, T.; Dudley, J. P.; Reichardt, C. L.; Aird, K. A.; Andersson, K.; Armstrong, R.; Ashby, M. L. N.; Bautz, M.; Bayliss, M.; Bazin, G.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Clocchiatti, A.; Crawford, T. M.; Crites, A. T.; Desai, S.; Dobbs, M. A.; Foley, R. J.; Forman, W. R.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Harrington, N.; High, F. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Jones, C.; Joy, M.; Keisler, R.; Knox, L.; Lee, A. T.; Leitch, E. M.; Liu, J.; Lueker, M.; Luong-Van, D.; Mantz, A.; Marrone, D. P.; McDonald, M.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Mocanu, L.; Mohr, J. J.; Montroy, T. E.; Murray, S. S.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Rest, A.; Ruel, J.; Ruhl, J. E.; Saliwanchik, B. R.; Saro, A.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Song, J.; Spieler, H. G.; Stalder, B.; Staniszewski, Z.; Stark, A. A.; Story, K.; Stubbs, C. W.; Suhada, R.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.

    2013-02-01

    We use measurements from the South Pole Telescope (SPT) Sunyaev-Zel'dovich (SZ) cluster survey in combination with X-ray measurements to constrain cosmological parameters. We present a statistical method that fits for the scaling relations of the SZ and X-ray cluster observables with mass while jointly fitting for cosmology. The method is generalizable to multiple cluster observables, and self-consistently accounts for the effects of the cluster selection and uncertainties in cluster mass calibration on the derived cosmological constraints. We apply this method to a data set consisting of an SZ-selected catalog of 18 galaxy clusters at z > 0.3 from the first 178 deg2 of the 2500 deg2 SPT-SZ survey, with 14 clusters having X-ray observations from either Chandra or XMM-Newton. Assuming a spatially flat ΛCDM cosmological model, we find the SPT cluster sample constrains σ8(Ω m /0.25)0.30 = 0.785 ± 0.037. In combination with measurements of the cosmic microwave background (CMB) power spectrum from the SPT and the seven-year Wilkinson Microwave Anisotropy Probe data, the SPT cluster sample constrains σ8 = 0.795 ± 0.016 and Ω m = 0.255 ± 0.016, a factor of 1.5 improvement on each parameter over the CMB data alone. We consider several extensions beyond the ΛCDM model by including the following as free parameters: the dark energy equation of state (w), the sum of the neutrino masses (Σm ν), the effective number of relativistic species (N eff), and a primordial non-Gaussianity (f NL). We find that adding the SPT cluster data significantly improves the constraints on w and Σm ν beyond those found when using measurements of the CMB, supernovae, baryon acoustic oscillations, and the Hubble constant. Considering each extension independently, we best constrain w = -0.973 ± 0.063 and the sum of neutrino masses Σm ν < 0.28 eV at 95% confidence, a factor of 1.25 and 1.4 improvement, respectively, over the constraints without clusters. Assuming a ΛCDM model with a

  7. Constraints on the Surface Magnetic Fields and Age of a Cool Hypergiant: XMM-Newton X-Ray Observations of VY CMa

    NASA Astrophysics Data System (ADS)

    Montez, Rodolfo, Jr.; Kastner, Joel H.; Humphreys, Roberta M.; Turok, Rebecca L.; Davidson, Kris

    2015-02-01

    The complex circumstellar ejecta of highly evolved, cool hypergiants are indicative of multiple, asymmetric mass-loss events. To explore whether such episodic, non-isotropic mass loss may be driven by surface magnetic activity, we have observed the archetypical cool hypergiant VY CMa with the XMM-Newton X-ray satellite observatory. The hypergiant itself is not detected in these observations. From the upper limit on the X-ray flux from VY CMa at the time of our observations (F X, UL ≈ 8 × 10-14 erg cm-2 s-1, corresponding to log LX /L bol <= -8), we estimate an average surface magnetic field strength fB <= 2 × 10-3 G (where f is the filling factor of magnetically active surface regions). These X-ray results for VY CMa represent the most stringent constraints to date on the magnetic field strength near the surface of a hypergiant. VY CMa's mass loss is episodic, however, and the hypergiant may have been in a state of low surface magnetic activity during the XMM observations. The XMM observations also yield detections of more than 100 X-ray sources within ~15' of VY CMa, roughly 50 of which have near-infrared counterparts. Analysis of X-ray hardness ratios and IR colors indicates that some of these field sources may be young, late-type stars associated with VY CMa, its adjacent molecular cloud complex, and the young cluster NGC 2362. Further study of the VY CMa field is warranted, given the potential to ascertain the evolutionary timescale of this enigmatic, massive star.

  8. Multi-point gradient calculation with constraints

    NASA Astrophysics Data System (ADS)

    de Keyser, Johan

    Multi-spacecraft missions resolve the space-time ambiguity inherent in single-spacecraft in situ measurements. One particularly useful technique is the computation of the gradients (spaceand time-derivatives) from multi-point observations of scalar and vector fields. Given the diffi- culties inherent in computing derivatives, we propose to improve the determination of gradients by imposing additional information in the form of constraints. We discuss geometric constraints on the orientation of the gradient vectors and physically-motivated constraints. For instance, imposing the divergence-free condition for the magnetic field leads to an improved curlometer. We describe the usefulness of such constrained least-squares gradient techniques as applied to magnetic field and plasma density observations by Cluster.

  9. A Framework for Dynamic Constraint Reasoning Using Procedural Constraints

    NASA Technical Reports Server (NTRS)

    Jonsson, Ari K.; Frank, Jeremy D.

    1999-01-01

    Many complex real-world decision and control problems contain an underlying constraint reasoning problem. This is particularly evident in a recently developed approach to planning, where almost all planning decisions are represented by constrained variables. This translates a significant part of the planning problem into a constraint network whose consistency determines the validity of the plan candidate. Since higher-level choices about control actions can add or remove variables and constraints, the underlying constraint network is invariably highly dynamic. Arbitrary domain-dependent constraints may be added to the constraint network and the constraint reasoning mechanism must be able to handle such constraints effectively. Additionally, real problems often require handling constraints over continuous variables. These requirements present a number of significant challenges for a constraint reasoning mechanism. In this paper, we introduce a general framework for handling dynamic constraint networks with real-valued variables, by using procedures to represent and effectively reason about general constraints. The framework is based on a sound theoretical foundation, and can be proven to be sound and complete under well-defined conditions. Furthermore, the framework provides hybrid reasoning capabilities, as alternative solution methods like mathematical programming can be incorporated into the framework, in the form of procedures.

  10. Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition.

    PubMed

    Yao, Maoqing; Cong, Sen; Arab, Shermin; Huang, Ningfeng; Povinelli, Michelle L; Cronin, Stephen B; Dapkus, P Daniel; Zhou, Chongwu

    2015-11-11

    Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due to their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates to achieve monolithic integration of solar cell materials that are not lattice-matched. Here, we report the first realization of nanowire-on-Si tandem cells with the observation of voltage addition of the GaAs nanowire top cell and the Si bottom cell with an open circuit voltage of 0.956 V and an efficiency of 11.4%. Our simulation showed that the current-matching condition plays an important role in the overall efficiency. Furthermore, we characterized GaAs nanowire arrays grown on lattice-mismatched Si substrates and estimated the carrier density using photoluminescence. A low-resistance connecting junction was obtained using n(+)-GaAs/p(+)-Si heterojunction. Finally, we demonstrated tandem solar cells based on top GaAs nanowire array solar cells grown on bottom planar Si solar cells. The reported nanowire-on-Si tandem cell opens up great opportunities for high-efficiency, low-cost multijunction solar cells. PMID:26502060

  11. Killing symmetries as Hamiltonian constraints

    NASA Astrophysics Data System (ADS)

    Lusanna, Luca

    2016-02-01

    The existence of a Killing symmetry in a gauge theory is equivalent to the addition of extra Hamiltonian constraints in its phase space formulation, which imply restrictions both on the Dirac observables (the gauge invariant physical degrees of freedom) and on the gauge freedom. When there is a time-like Killing vector field only pure gauge electromagnetic fields survive in Maxwell theory in Minkowski space-time, while in ADM canonical gravity in asymptotically Minkowskian space-times only inertial effects without gravitational waves survive.

  12. Understanding the origin of CMB constraints on dark energy

    NASA Astrophysics Data System (ADS)

    Jassal, H. K.; Bagla, J. S.; Padmanabhan, T.

    2010-07-01

    We study the observational constraints of cosmic microwave background (CMB) temperature and polarization anisotropies on models of dark energy, with special focus on models with variation in properties of dark energy with time. We demonstrate that the key constraint from CMB observations arises from the location of acoustic peaks. An additional constraint arises from the limits on ΩNR from the relative amplitudes of acoustic peaks. Further, we show that the distance to the last scattering surface is not how the CMB observations constrain the combination of parameters for models of dark energy. We also use constraints from supernova observations and show that unlike the gold and silver samples, the Supernova Legacy Survey (SNLS) sample prefers a region of parameter space that has a significant overlap with the region preferred by the CMB observations. This is a verification of a conjecture made by us in an earlier work. We discuss combined constraints from Wilkinson Microwave Anisotropy Probe 5-yr and SNLS observations. We find that models with w ~= - 1 are preferred for models with a constant equation-of-state parameters. In case of models with a time-varying dark energy, we show that constraints on evolution of dark energy density are almost independent of the type of variation assumed for the equation-of-state parameter. This makes it easy to get approximate constraints from CMB observations on arbitrary models of dark energy. Constraints on models with a time-varying dark energy are predominantly due to CMB observations, with supernova constraints playing only a marginal role.

  13. Multiwavelength analysis for interferometric (sub-)mm observations of protoplanetary disks. Radial constraints on the dust properties and the disk structure

    NASA Astrophysics Data System (ADS)

    Tazzari, M.; Testi, L.; Ercolano, B.; Natta, A.; Isella, A.; Chandler, C. J.; Pérez, L. M.; Andrews, S.; Wilner, D. J.; Ricci, L.; Henning, T.; Linz, H.; Kwon, W.; Corder, S. A.; Dullemond, C. P.; Carpenter, J. M.; Sargent, A. I.; Mundy, L.; Storm, S.; Calvet, N.; Greaves, J. A.; Lazio, J.; Deller, A. T.

    2016-04-01

    Context. The growth of dust grains from sub-μm to mm and cm sizes is the first step towards the formation of planetesimals. Theoretical models of grain growth predict that dust properties change as a function of disk radius, mass, age, and other physical conditions. High angular resolution observations at several (sub-)mm wavelengths constitute the ideal tool with which to directly probe the bulk of dust grains and to investigate the radial distribution of their properties. Aims: We lay down the methodology for a multiwavelength analysis of (sub-)mm and cm continuum interferometric observations to self-consistently constrain the disk structure and the radial variation of the dust properties. The computational architecture is massively parallel and highly modular. Methods: The analysis is based on the simultaneous fit in the uv-plane of observations at several wavelengths with a model for the disk thermal emission and for the dust opacity. The observed flux density at the different wavelengths is fitted by posing constraints on the disk structure and on the radial variation of the grain size distribution. Results: We apply the analysis to observations of three protoplanetary disks (AS 209, FT Tau, DR Tau) for which a combination of spatially resolved observations in the range ~0.88 mm to ~10 mm is available from SMA, CARMA, and VLA. In these disks we find evidence of a decrease in the maximum dust grain size, amax, with radius. We derive large amax values up to 1 cm in the inner disk 15 AU ≤ R ≤ 30 AU and smaller grains with amax ~ 1 mm in the outer disk (R ≳ 80 AU). Our analysis of the AS 209 protoplanetary disk confirms previous literature results showing amax decreasing with radius. Conclusions: Theoretical studies of planetary formation through grain growth are plagued by the lack of direct information on the radial distribution of the dust grain size. In this paper we develop a multiwavelength analysis that will allow this missing quantity to be

  14. Constraints on the mantle and lithosphere dynamics from the observed geoid with the effect of visco-elasto-plastic rheology in the upper 300 km

    NASA Astrophysics Data System (ADS)

    Osei Tutu, Anthony; Steinberger, Bernhard; Rogozhina, Irina; Sobolev, Stephan

    2015-04-01

    Over the past decades rheological properties of the Earth's mantle and lithosphere have been extensively studied using numerical models calibrated versus a range of surface observations (e.g., free-air-gravity anomaly/geoid, dynamic topography, plate velocity, etc.).The quality of model predictions however strongly depends on the simplifying assumptions, spatial resolution and parameterizations adopted by numerical models. The geoid is largely (Hager & Richards, 1989) determined by both the density anomalies driving the mantle flow and the dynamic topography at the Earth surface and the core-mantle boundary. This is the effect of the convective processes within the Earth's mantle. The remainder is mostly due to strong heterogeneities in the lithospheric mantle and the crust, which also need to be taken into account. The surface topography caused by density anomalies both in the sub-lithospheric mantle and within the lithosphere also depends on the lithosphere rheology. Here we investigate the effects of complex lithosphere rheology on the modelled dynamic topography, geoid and plate motion using a spectral mantle flow code (Hager & O'Connell, 1981) considering radial viscosity distribution and a fully coupled code of the lithosphere and mantle accounting for strong heterogeneities in the upper mantle rheology in the 300 km depths (Popov & Sobolev, 2008). This study is the first step towards linking global mantle dynamics with lithosphere dynamics using the observed geoid as a major constraint. Here we present the results from both codes and compare them with the observed geoid, dynamic topography and plate velocities from GPS measurements. This method allows us to evaluate the effects of plate rheology (e.g., strong plate interiors and weak plate margins) and stiff subducted lithosphere on these observables (i.e. geoid, topography, plate boundary stresses) as well as on plate motion. This effort will also serve as a benchmark of the two existing numerical methods

  15. Tectonomagmatic evolution of the final stages of rifting along the deep conjugate Australian-Antarctic magma-poor rifted margins: Constraints from seismic observations

    NASA Astrophysics Data System (ADS)

    Gillard, Morgane; Autin, Julia; Manatschal, Gianreto; Sauter, Daniel; Munschy, Marc; Schaming, Marc

    2015-04-01

    The processes related to hyperextension, exhumed mantle domains, lithospheric breakup, and formation of first unequivocal oceanic crust at magma-poor rifted margins are yet poorly understood. In this paper, we try to bring new constraints and new ideas about these latest deformation stages by studying the most distal Australian-Antarctic rifted margins. We propose a new interpretation, linking the sedimentary architectures to the nature and type of basement units, including hyperextended crust, exhumed mantle, embryonic, and steady state oceanic crusts. One major implication of our study is that terms like prerift, synrift, and postrift cannot be used in such polyphase settings, which also invalidates the concept of breakup unconformity. Integration and correlation of all available data, particular seismic and potential field data, allows us to propose a new model to explain the evolution of magma-poor distal rifted margins involving multiple and complex detachment systems. We propose that lithospheric breakup occurs after a phase of proto-oceanic crust formation, associated with a substantial magma supply. First steady state oceanic crust may therefore not have been emplaced before ~53.3 Ma corresponding to magnetic anomaly C24. Observations of magma amount and its distribution along the margins highlight a close magma-fault relationship during the development of these margins.

  16. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    NASA Astrophysics Data System (ADS)

    Hofmann, F.; Sanders, J. S.; Nandra, K.; Clerc, N.; Gaspari, M.

    2016-08-01

    Context. Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter (DM) candidate. Aims: We aim to put constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing angle in a 7.1 keV sterile neutrino DM scenario. Methods: For a sample of 33 high-mass clusters of galaxies, we merge all observations from the Chandra data archive. Each cluster has more than 100 ks of combined exposure. The resulting high signal-to-noise spectra are used to constrain the flux of an unidentified line emission at 3.55 keV in the individual spectra and a merged spectrum of all clusters. Results: We obtained very detailed spectra around the 3.55 keV range and limits on an unidentified emission line. Assuming all DM were made of 7.1 keV sterile neutrinos, the upper limits on the mixing angle are sin2(2Θ) < 10.1×10-11 from ACIS-I and < 40.3×10-11 from ACIS-S data at 99.7 per cent confidence level. Conclusions: We do not find evidence for an unidentified emission line at 3.55 keV. The sample extends the list of objects searched for an emission line at 3.55 keV and will help to identify the best targets for future studies of the potential DM decay line with upcoming X-ray observatories like Hitomi (Astro-H), eROSITA, and Athena.

  17. Constraints on long-lived remnants of neutron star binary mergers from late-time radio observations of short duration gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Bower, Geoffrey C.

    2014-01-01

    The coalescence of a binary neutron star (NS) system (an `NS merger' or NSM) may in some cases produce a massive NS remnant that is long lived and, potentially, indefinitely stable to gravitational collapse. Such a remnant has been proposed as an explanation for the late-X-ray emission observed following some short-duration gamma-ray bursts (GRBs) and as possible electromagnetic counterparts to the gravitational wave chirp. A stable NS merger remnant necessarily possesses a large rotational energy ≳1052 erg, the majority of which is ultimately deposited into the surrounding circumburst medium (CBM) at mildly relativistic velocities. We present Very Large Array radio observations of seven short GRBs, some of which possessed temporally extended X-ray emission, on time-scales of ˜1-3 yr following the initial burst. No radio sources were detected, with typical upper limits ˜0.3 mJy at ν = 1.4 GHz. A basic model for the synchrotron emission from the blast wave is used to constrain the presence of a long-lived NSM remnant in each system. Depending on the GRB, our non-detections translate into upper limits on the CBM density n ≲ 3 × 10- 2-3 cm-3 required for consistency with the remnant hypothesis. Our upper limits rule out a long-lived remnant in GRB 050724 and 060505, but cannot rule out such a remnant in other systems due to their lower inferred CMB densities based on afterglow modelling or the lack of such constraints.

  18. Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-ray Observations of the Coma Cluster of Galaxies with VERITAS and FERMI

    NASA Technical Reports Server (NTRS)

    Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Perkins, J. S.

    2012-01-01

    Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E greater than100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99 confidence level were measured to be on the order of (2-5) x 10(sup -8) photons m(sup -2) s(sup -1) (VERITAS,greater than 220 GeV) and approximately 2 x 10(sup -6) photons m(sup -2) s(sup -1) (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be less than 16% from VERITAS data and less than 1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be 50. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of approximately (2-5.5)microG, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark

  19. CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI

    SciTech Connect

    Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Byrum, K.; Cannon, A.; Collins-Hughes, E.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Cui, W.; Feng, Q.; Finley, J. P.; Dumm, J.; Falcone, A.; Federici, S. E-mail: christoph.pfrommer@h-its.org; and others

    2012-10-01

    Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) Multiplication-Sign 10{sup -8} photons m {sup -2} s {sup -1} (VERITAS, >220 GeV) and {approx}2 Multiplication-Sign 10{sup -6} photons m {sup -2} s {sup -1} (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be <16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of {approx}(2-5.5) {mu}G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM

  20. Constraints on emissions of hydrocarbons and combustion tracers in the Colorado Front Range using observations of 14CO2 at the Boulder Atmospheric Observatory (BAO)

    NASA Astrophysics Data System (ADS)

    LaFranchi, B. W.; Petron, G.; Miller, J. B.; Lehman, S. J.; Andrews, A. E.; Dlugokencky, E. J.; Miller, B. R.; Montzka, S. A.; Turnbull, J. C.; Tans, P. P.; Guilderson, T. P.

    2011-12-01

    Bottom-up inventories of trace gases formed as a byproduct of fossil fuel combustion have significant uncertainty associated with them because of the difficulty in quantifying the relationship between the mass of fuel consumed and the mass emitted; this is in contrast to the near stoichiometric production of CO2 from the combustion of hydrocarbons. Emissions of species such as CO, CH4, acetylene, and benzene depend greatly on a number of variables including fuel type, combustion temperature, oxidant-to-fuel ratio, and post-combustion tail-pipe or flue-stack "scrubbing". Given the impact of many of these combustion by-products on air quality, human health, and climate, atmospheric observations are necessary in order to critically evaluate bottom-up emissions estimates. Atmospheric radiocarbon (14C) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the near absence of 14C in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14C analysis has greatly increased the potential for using such measurements to verify bottom-up emissions inventories of fossil fuel CO2 (CO2ff), as well as other co-emitted species. Here we use observations of 14CO2 and a series of hydrocarbons and combustion tracers from the Boulder Atmospheric Observatory (BAO; Lat: 40.050o, Lon: -105.004o) to derive emission ratios of each species to CO2. From these emission ratios, we estimate absolute emission fluxes of these species by using an existing CO2ff inventory. Among the species considered are CO, CH4, acetylene (C2H2), benzene (C6H6), and C3-C5 alkanes. Comparisons of top-down emissions estimates are made to existing inventories of these species for the region, where available, as well as to previous efforts to estimate emissions from atmospheric observations in the Colorado Front Range.We find that CO is overestimated in the NEI 2008 by a factor of ~2; a

  1. Constraints on emissions of carbon monoxide, methane, and a suite of hydrocarbons in the Colorado Front Range using observations of 14CO2

    NASA Astrophysics Data System (ADS)

    LaFranchi, B. W.; Pétron, G.; Miller, J. B.; Lehman, S. J.; Andrews, A. E.; Dlugokencky, E. J.; Miller, B. R.; Montzka, S. A.; Hall, B.; Neff, W.; Sweeney, C.; Turnbull, J. C.; Wolfe, D. E.; Tans, P. P.; Gurney, K. R.; Guilderson, T. P.

    2013-01-01

    Atmospheric radiocarbon (14CO) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the absence of 14CO in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14CO analysis has greatly increased the potential for using such measurements to evaluate bottom-up emissions inventories of fossil fuel CO2 (CO2ff), as well as those for other co-emitted species. Here we use observations of 14CO2 and a series of hydrocarbons and combustion tracers from discrete air samples collected between June 2009 and September 2010 at the National Oceanic and Atmospheric Administration Boulder Atmospheric Observatory (BAO; Lat: 40.050° N, Lon: 105.004° W) to derive emission ratios of each species to CO2ff. From these emission ratios, we estimate emissions of these species by using the Vulcan CO2ff high resolution data product as a reference. The species considered in this analysis are carbon monoxide (CO), methane (CH4), acetylene (C2H2), benzene (C6H6), and C3-C5 alkanes. Comparisons of top-down emissions estimates are made to existing inventories of these species for Denver and adjacent counties, as well as to previous efforts to estimate emissions from atmospheric observations over the same area. We find that CO is overestimated in the 2008 National Emissions Inventory (NEI, 2008) by a factor of ~2. A close evaluation of the inventory suggests that the ratio of CO emitted per unit fuel burned from on-road gasoline vehicles is likely over-estimated by a factor of 2.5. The results also suggest that while the oil and gas sector is the largest contributor to the CH4 signal in air arriving from the north and east, it is very likely that other sources, including agricultural sources, contribute to this signal and must be accounted for when attributing these signals to oil and gas industry activity from a top-down perspective. Our results are consistent

  2. Constraint algebra in bigravity

    SciTech Connect

    Soloviev, V. O.

    2015-07-15

    The number of degrees of freedom in bigravity theory is found for a potential of general form and also for the potential proposed by de Rham, Gabadadze, and Tolley (dRGT). This aim is pursued via constructing a Hamiltonian formalismand studying the Poisson algebra of constraints. A general potential leads to a theory featuring four first-class constraints generated by general covariance. The vanishing of the respective Hessian is a crucial property of the dRGT potential, and this leads to the appearance of two additional second-class constraints and, hence, to the exclusion of a superfluous degree of freedom—that is, the Boulware—Deser ghost. The use of a method that permits avoiding an explicit expression for the dRGT potential is a distinctive feature of the present study.

  3. Additional photoelectric observations and analysis of the variability of the beta Cephei stars 12 and 16 Lacertae

    NASA Astrophysics Data System (ADS)

    Jarzebowski, T.; Jerzykiewicz, M.; Rios Herrera, M.; Rios Berumen, M.

    1980-04-01

    We present photoelectric observations of two Cephei variables - 12 and 16 Lacertae- made in 1977 in the Observatory of Zacatecas. The results of a frequency analysis made with these data and with the data obtained in the same year at the San Pedro Martir, Chiran and Bialkow Observatories are also given.

  4. Addition of Escherichia coli K-12 Growth Observation and Gene Essentiality Data to the EcoCyc Database

    PubMed Central

    Mackie, Amanda; Paley, Suzanne; Keseler, Ingrid M.; Shearer, Alexander; Paulsen, Ian T.

    2014-01-01

    The sets of compounds that can support growth of an organism are defined by the presence of transporters and metabolic pathways that convert nutrient sources into cellular components and energy for growth. A collection of known nutrient sources can therefore serve both as an impetus for investigating new metabolic pathways and transporters and as a reference for computational modeling of known metabolic pathways. To establish such a collection for Escherichia coli K-12, we have integrated data on the growth or nongrowth of E. coli K-12 obtained from published observations using a variety of individual media and from high-throughput phenotype microarrays into the EcoCyc database. The assembled collection revealed a substantial number of discrepancies between the high-throughput data sets, which we investigated where possible using low-throughput growth assays on soft agar and in liquid culture. We also integrated six data sets describing 16,119 observations of the growth of single-gene knockout mutants of E. coli K-12 into EcoCyc, which are relevant to antimicrobial drug design, provide clues regarding the roles of genes of unknown function, and are useful for validating metabolic models. To make this information easily accessible to EcoCyc users, we developed software for capturing, querying, and visualizing cellular growth assays and gene essentiality data. PMID:24363340

  5. Additional observations on Rhynchosperma quinnii (Medullosaceae): a permineralized ovule from the Chesterian (Upper Mississippian) Fayetteville Formation of Arkansas.

    PubMed

    Dunn, Michael T; Rothwell, Gar W; Mapes, Gene

    2002-11-01

    New ovules from the Fayetteville Formation (Upper Mississippian) of Arkansas expand our knowledge of the morphology and anatomy of Rhynchosperma and suggest it was produced by a medullosan seed fern. Rhynchosperma has been described as radially symmetrical with a two-layered integument and vascularization in the integument only. The apical portion of the integument is ribbed; the nucellus is fused to the integument and apically differentiated into a dome-shaped pollen chamber. The vascular system is incompletely known and apparently restricted to the base of the integument. The new specimens are like Rhynchosperma in external shape, size, number of ribs, and numerous histological features. However, new data reveal that the nucellus is vascularized by a sheath of tracheids, the integument is vascularized by discrete bundles, the pollen chamber has a nucellar beak, and the nucellus is attached to the integument for a variable distance from the base. In addition, the integument is tripartite with an elaborate apical region; ribs formed by the integument are more pronounced at the apex; and internally open, hollow lobes form a stellate micropylar canal. The presence of a tripartite integument, the nature of the vascular system, the nucellus-integument attachment, the pollen chamber structure, symmetry, and the association with medullosan vegetative remains suggest medullosan affinity for these ovules and strengthens the evidence for the origin of the family before the end of the Lower Carboniferous. PMID:21665608

  6. Additional Features of the Plasma Environment in the Heliosheath and Outer Heliosphere: Further Examination of the Voyager 2 Plasma Observations

    NASA Astrophysics Data System (ADS)

    Intriligator, D. S.; Intriligator, J.; Miller, W.; Webber, W. R.

    2009-12-01

    We continue our examination of the plasma distributions obtained by the MIT plasma probe on Voyager 2 in 2007. Last year we presented an identification of High Energy Ions (HEIs) in the plasma data in the vicinity of the termination shock. These HEIs are reminiscent of the multiple reflected gyrating and pickup protons observed in the vicinity of planetary foreshocks. We continue to examine some of the details of the MIT plasma data and to compare these plasma data with other in-situ spacecraft measurements including with the enhanced signals in the plasma wave subsystem. We also evaluate our findings in terms of theoretical expectations. Our detailed analyses show that in 2007, in the vicinity of Voyager 2, the characteristics of the outer heliosphere and heliosheath were quite complex with variations occurring on many scales and indicating the need for further theoretical and empirical study. This work is sponsored by NASA Grant NNX08AE40G and by Carmel Research Center. We are grateful to John Richardson for providing the Voyager 2 MIT plasma data.

  7. Constraints on short-term mantle rheology from the J2 observation and the dispersion of the 18.6 y tidal Love number

    NASA Technical Reports Server (NTRS)

    Sabadini, R.; Yuen, D. A.; Widmer, R.

    1985-01-01

    Information derived from data recently acquired from the LAGEOS satellite is used to place some constraints on the rheological parameters of short-term mantle rheology. The validity of Lambeck and Nakiboglu's (1983) rheological model is assessed by formally developing an expression for the transformed shear modulus using a truncated retardation spectrum. This analytical formula is used to show that the parameters of the above mentioned model are not consistent at all with the amount of anelastic dispersion expected in the Chandler wobble and with the attenuation of seismic normal modes. The feasibility of a standard linear solid (SLS) rheology operating over intermediate timescales between 1 and 100 yr is investigated to determine whether the tidal dispersion at 18.6 yr can be explained by this model. An attempt is made to place some constraints on the parameters of the SLS model and the nature of short-term mantle rheology for timescales of less than 100 yr is discussed.

  8. (abstract) The Distribution of Carbon in the Outer Solar System: New Constraints on Planetary Formation Mechanisms from Groundbased Spectroscopic Observations of Uranus and Neptune

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Mickelson, M. E.; Larson, L. E.

    1994-01-01

    New limits on the methane mixing ratio within the well-mixed tropospheres of Uranus and Neptune place significant constraints on planetary formation mechanisms within the outer solar system. Our results support the conclusion of other researchers that a nontrivial amount of methane in the outer solar system was incorporated into the planets by dissolution of carbon-bearing planetesimals during the early evolutionary stages of both Uranus and Neptune.

  9. Constraint Handling in Transmission Network Expansion Planning

    NASA Astrophysics Data System (ADS)

    Mallipeddi, R.; Verma, Ashu; Suganthan, P. N.; Panigrahi, B. K.; Bijwe, P. R.

    Transmission network expansion planning (TNEP) is a very important and complex problem in power system. Recently, the use of metaheuristic techniques to solve TNEP is gaining more importance due to their effectiveness in handling the inequality constraints and discrete values over the conventional gradient based methods. Evolutionary algorithms (EAs) generally perform unconstrained search and require some additional mechanism to handle constraints. In EA literature, various constraint handling techniques have been proposed. However, to solve TNEP the penalty function approach is commonly used while the other constraint handling methods are untested. In this paper, we evaluate the performance of different constraint handling methods like Superiority of Feasible Solutions (SF), Self adaptive Penalty (SP),E-Constraint (EC), Stochastic Ranking (SR) and the ensemble of constraint handling techniques (ECHT) on TNEP. The potential of different constraint handling methods and their ensemble is evaluated using an IEEE 24 bus system with and without security constraints.

  10. Genetic constraints predict evolutionary divergence in Dalechampia blossoms

    PubMed Central

    Bolstad, Geir H.; Hansen, Thomas F.; Pélabon, Christophe; Falahati-Anbaran, Mohsen; Pérez-Barrales, Rocío; Armbruster, W. Scott

    2014-01-01

    If genetic constraints are important, then rates and direction of evolution should be related to trait evolvability. Here we use recently developed measures of evolvability to test the genetic constraint hypothesis with quantitative genetic data on floral morphology from the Neotropical vine Dalechampia scandens (Euphorbiaceae). These measures were compared against rates of evolution and patterns of divergence among 24 populations in two species in the D. scandens species complex. We found clear evidence for genetic constraints, particularly among traits that were tightly phenotypically integrated. This relationship between evolvability and evolutionary divergence is puzzling, because the estimated evolvabilities seem too large to constitute real constraints. We suggest that this paradox can be explained by a combination of weak stabilizing selection around moving adaptive optima and small realized evolvabilities relative to the observed additive genetic variance. PMID:25002700

  11. Genetic constraints predict evolutionary divergence in Dalechampia blossoms.

    PubMed

    Bolstad, Geir H; Hansen, Thomas F; Pélabon, Christophe; Falahati-Anbaran, Mohsen; Pérez-Barrales, Rocío; Armbruster, W Scott

    2014-08-19

    If genetic constraints are important, then rates and direction of evolution should be related to trait evolvability. Here we use recently developed measures of evolvability to test the genetic constraint hypothesis with quantitative genetic data on floral morphology from the Neotropical vine Dalechampia scandens (Euphorbiaceae). These measures were compared against rates of evolution and patterns of divergence among 24 populations in two species in the D. scandens species complex. We found clear evidence for genetic constraints, particularly among traits that were tightly phenotypically integrated. This relationship between evolvability and evolutionary divergence is puzzling, because the estimated evolvabilities seem too large to constitute real constraints. We suggest that this paradox can be explained by a combination of weak stabilizing selection around moving adaptive optima and small realized evolvabilities relative to the observed additive genetic variance. PMID:25002700

  12. REDUCTION OF CONSTRAINTS FOR COUPLED OPERATIONS

    SciTech Connect

    Raszewski, F.; Edwards, T.

    2009-12-15

    The homogeneity constraint was implemented in the Defense Waste Processing Facility (DWPF) Product Composition Control System (PCCS) to help ensure that the current durability models would be applicable to the glass compositions being processed during DWPF operations. While the homogeneity constraint is typically an issue at lower waste loadings (WLs), it may impact the operating windows for DWPF operations, where the glass forming systems may be limited to lower waste loadings based on fissile or heat load limits. In the sludge batch 1b (SB1b) variability study, application of the homogeneity constraint at the measurement acceptability region (MAR) limit eliminated much of the potential operating window for DWPF. As a result, Edwards and Brown developed criteria that allowed DWPF to relax the homogeneity constraint from the MAR to the property acceptance region (PAR) criterion, which opened up the operating window for DWPF operations. These criteria are defined as: (1) use the alumina constraint as currently implemented in PCCS (Al{sub 2}O{sub 3} {ge} 3 wt%) and add a sum of alkali constraint with an upper limit of 19.3 wt% ({Sigma}M{sub 2}O < 19.3 wt%), or (2) adjust the lower limit on the Al{sub 2}O{sub 3} constraint to 4 wt% (Al{sub 2}O{sub 3} {ge} 4 wt%). Herman et al. previously demonstrated that these criteria could be used to replace the homogeneity constraint for future sludge-only batches. The compositional region encompassing coupled operations flowsheets could not be bounded as these flowsheets were unknown at the time. With the initiation of coupled operations at DWPF in 2008, the need to revisit the homogeneity constraint was realized. This constraint was specifically addressed through the variability study for SB5 where it was shown that the homogeneity constraint could be ignored if the alumina and alkali constraints were imposed. Additional benefit could be gained if the homogeneity constraint could be replaced by the Al{sub 2}O{sub 3} and sum of

  13. Exploiting simultaneous observational constraints on mass and absorption to estimate the global direct radiative forcing of black carbon and brown carbon

    NASA Astrophysics Data System (ADS)

    Wang, X.; Heald, C. L.; Ridley, D. A.; Schwarz, J. P.; Spackman, J. R.; Perring, A. E.; Coe, H.; Liu, D.; Clarke, A. D.

    2014-10-01

    Atmospheric black carbon (BC) is a leading climate warming agent, yet uncertainties on the global direct radiative forcing (DRF) remain large. Here we expand a global model simulation (GEOS-Chem) of BC to include the absorption enhancement associated with BC coating and separately treat both the aging and physical properties of fossil-fuel and biomass-burning BC. In addition we develop a global simulation of brown carbon (BrC) from both secondary (aromatic) and primary (biomass burning and biofuel) sources. The global mean lifetime of BC in this simulation (4.4 days) is substantially lower compared to the AeroCom I model means (7.3 days), and as a result, this model captures both the mass concentrations measured in near-source airborne field campaigns (ARCTAS, EUCAARI) and surface sites within 30%, and in remote regions (HIPPO) within a factor of 2. We show that the new BC optical properties together with the inclusion of BrC reduces the model bias in absorption aerosol optical depth (AAOD) at multiple wavelengths by more than 50% at AERONET sites worldwide. However our improved model still underestimates AAOD by a factor of 1.4 to 2.8 regionally, with the largest underestimates in regions influenced by fire. Using the RRTMG model integrated with GEOS-Chem we estimate that the all-sky top-of-atmosphere DRF of BC is +0.13 Wm-2 (0.08 Wm-2 from anthropogenic sources and 0.05 Wm-2 from biomass burning). If we scale our model to match AERONET AAOD observations we estimate the DRF of BC is +0.21 Wm-2, with an additional +0.11 Wm-2 of warming from BrC. Uncertainties in size, optical properties, observations, and emissions suggest an overall uncertainty in BC DRF of -80%/+140%. Our estimates are at the lower end of the 0.2-1.0 Wm-2 range from previous studies, and substantially less than the +0.6 Wm-2 DRF estimated in the IPCC 5th Assessment Report. We suggest that the DRF of BC has previously been overestimated due to the overestimation of the BC lifetime (including the

  14. Exploiting simultaneous observational constraints on mass and absorption to estimate the global direct radiative forcing of black carbon and brown carbon

    NASA Astrophysics Data System (ADS)

    Wang, X.; Heald, C. L.; Ridley, D. A.; Schwarz, J. P.; Spackman, J. R.; Perring, A. E.; Coe, H.; Liu, D.; Clarke, A. D.

    2014-06-01

    Atmospheric black carbon (BC) is a leading climate warming agent, yet uncertainties on the global direct radiative forcing (DRF) remain large. Here we expand a global model simulation (GEOS-Chem) of BC to include the absorption enhancement associated with BC coating and separately treat both the aging and physical properties of fossil fuel and biomass burning BC. In addition we develop a global simulation of Brown Carbon (BrC) from both secondary (aromatic) and primary (biomass burning and biofuel) sources. The global mean lifetime of BC in this simulation (4.4 days) is substantially lower compared to the AeroCom I model means (7.3 days), and as a result, this model captures both the mass concentrations measured in near-source airborne field campaigns (ARCTAS, EUCAARI) and surface sites within 30%, and in remote regions (HIPPO) within a factor of two. We show that the new BC optical properties together with the inclusion of BrC reduces the model bias in Absorption Aerosol Optical Depth (AAOD) at multiple wavelengths by more than 50% at AERONET sites worldwide. However our improved model still underestimates AAOD by a factor of 1.4 to 2.8 regionally, with largest underestimates in regions influenced by fire. Using the RRTMG model integrated with GEOS-Chem we estimate that the all-sky top-of-atmosphere DRF of BC is +0.13 W m-2 (0.08 W m-2 from anthropogenic sources and 0.05 W m-2 from biomass burning). If we scale our model to match AERONET AAOD observations we estimate the DRF of BC is +0.21 W m-2, with an additional +0.11 W m-2 of warming from BrC. Uncertainties in size, optical properties, observations, and emissions suggest an overall uncertainty in BC DRF of -80% / +140%. Our estimates are at the lower end of the 0.2-1.0 W m-2 range from previous studies, and substantially less than the +0.6 W m-2 DRF estimated in the IPCC 5th Assessment Report. We suggest that the DRF of BC has previously been overestimated due to the overestimation of the BC lifetime and the

  15. Hubble Space Telescope NICMOS Observations of the Embedded Cluster in NGC 2024: Constraints on the Initial Mass Function and Binary Fraction

    NASA Astrophysics Data System (ADS)

    Liu, Wilson M.; Meyer, Michael R.; Cotera, Angela S.; Young, Erick T.

    2003-10-01

    We present an analysis of NICMOS observations of the embedded cluster associated with NGC 2024. An analysis of the cluster color-magnitude diagram (CMD) using the models of D'Antona & Mazzitelli and Baraffe et al. (published in 1997 and 1998, respectively) indicates that the ratio of intermediate-mass (1.0-10.0 Msolar) to low-mass (0.1-1.0 Msolar) stars is consistent with the stellar initial mass function (IMF) for the field. In addition to the CMD analysis, we present results on the multiplicity of stars in the region. Three companions (in a sample of 95 potential primaries) were found, with angular separations between 0.4" and 1.0", translating to a projected linear separation of 184-460 AU for an estimated distance of 460 pc. The completeness of binary detections is assessed using recovery fractions calculated by a series of tests using artificially generated companions to potential primaries in the data frames. We find that the binary fraction in NGC 2024 is consistent with that of Duquennoy & Mayor (published in 1991) for solar neighborhood stars over the range of separations and companion masses appropriate for our survey.

  16. Constraints on olivine-rich rock types on the Moon as observed by Diviner and M3: Implications for the formation of the lunar crust

    NASA Astrophysics Data System (ADS)

    Arnold, J. A.; Glotch, T. D.; Lucey, P. G.; Song, E.; Thomas, I. R.; Bowles, N. E.; Greenhagen, B. T.

    2016-07-01

    We place upper limits on lunar olivine abundance using midinfrared (5-25 µm) data from the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment (Diviner) along with effective emissivity spectra of mineral mixtures in a simulated lunar environment. Olivine-bearing, pyroxene-poor lithologies have been identified on the lunar surface with visible-near-infrared (VNIR) observations. Since the Kaguya Spectral Profiler (SP) VNIR survey of olivine-rich regions is the most complete to date, we focus this work on exposures identified by that study. We first confirmed the locations with VNIR data from the Moon Mineralogy Mapper (M3) instrument. We then developed a Diviner olivine index from our laboratory data which, along with M3 and Lunar Reconnaissance Orbiter Camera wide-angle camera data, was used to select the geographic area over which Diviner emissivity data were extracted. We calculate upper limits on olivine abundance for these areas using laboratory emissivity spectra of anorthite-forsterite mixtures acquired under lunar-like conditions. We find that these exposures have widely varying olivine content. In addition, after applying an albedo-based space weathering correction to the Diviner data, we find that none of the areas are unambiguously consistent with concentrations of forsterite exceeding 90 wt %, in contrast to the higher abundance estimates derived from VNIR data.

  17. New Constraints on ΩM, ΩΛ, and w from an Independent Set of 11 High-Redshift Supernovae Observed with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Knop, R. A.; Aldering, G.; Amanullah, R.; Astier, P.; Blanc, G.; Burns, M. S.; Conley, A.; Deustua, S. E.; Doi, M.; Ellis, R.; Fabbro, S.; Folatelli, G.; Fruchter, A. S.; Garavini, G.; Garmond, S.; Garton, K.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I.; Howell, D. A.; Kim, A. G.; Lee, B. C.; Lidman, C.; Mendez, J.; Nobili, S.; Nugent, P. E.; Pain, R.; Panagia, N.; Pennypacker, C. R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schaefer, B.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Sullivan, M.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2003-11-01

    We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z=0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM=0.25+0.07-0.06(statistical)+/-0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ=0.75+0.06-0.07(statistical)+/-0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w=-1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w=-1.05+0.15-0.20(statistical)+/-0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ>0)>0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution. Based in part on

  18. METAL-POOR STARS OBSERVED WITH THE MAGELLAN TELESCOPE. I. CONSTRAINTS ON PROGENITOR MASS AND METALLICITY OF AGB STARS UNDERGOING s-PROCESS NUCLEOSYNTHESIS

    SciTech Connect

    Placco, Vinicius M.; Rossi, Silvia; Frebel, Anna; Beers, Timothy C.; Karakas, Amanda I.; Kennedy, Catherine R.; Christlieb, Norbert; Stancliffe, Richard J.

    2013-06-20

    We present a comprehensive abundance analysis of two newly discovered carbon-enhanced metal-poor (CEMP) stars. HE 2138-3336 is a s-process-rich star with [Fe/H] = -2.79, and has the highest [Pb/Fe] abundance ratio measured thus far, if non-local thermodynamic equilibrium corrections are included ([Pb/Fe] = +3.84). HE 2258-6358, with [Fe/H] = -2.67, exhibits enrichments in both s- and r-process elements. These stars were selected from a sample of candidate metal-poor stars from the Hamburg/ESO objective-prism survey, and followed up with medium-resolution (R {approx} 2000) spectroscopy with GEMINI/GMOS. We report here on derived abundances (or limits) for a total of 34 elements in each star, based on high-resolution (R {approx} 30, 000) spectroscopy obtained with Magellan-Clay/MIKE. Our results are compared to predictions from new theoretical asymptotic giant branch (AGB) nucleosynthesis models of 1.3 M{sub Sun} with [Fe/H] = -2.5 and -2.8, as well as to a set of AGB models of 1.0 to 6.0 M{sub Sun} at [Fe/H] = -2.3. The agreement with the model predictions suggests that the neutron-capture material in HE 2138-3336 originated from mass transfer from a binary companion star that previously went through the AGB phase, whereas for HE 2258-6358, an additional process has to be taken into account to explain its abundance pattern. We find that a narrow range of progenitor masses (1.0 {<=} M(M{sub Sun }) {<=} 1.3) and metallicities (-2.8 {<=} [Fe/H] {<=}-2.5) yield the best agreement with our observed elemental abundance patterns.

  19. Superresolution via sparsity constraints

    NASA Technical Reports Server (NTRS)

    Donoho, David L.

    1992-01-01

    The problem of recovering a measure mu supported on a lattice of span Delta is considered under the condition that measurements are only available concerning the Fourier Transform at frequencies of Omega or less. If Omega is much smaller than the Nyquist frequency pi/Delta and the measurements are noisy, then stable recovery of mu is generally impossible. It is shown here that if, in addition, it is known that mu satisfies certain sparsity constraints, then stable recovery is possible. This finding validates practical efforts in spectroscopy, seismic prospecting, and astronomy to provide superresolution by imposing support limitations in reconstruction.

  20. An Unexpected Observation Concerning the Effect of Anionic Additives on the Retention Behavior of Basic Drugs and Peptides in Reversed-Phase Liquid Chromatography

    PubMed Central

    Wang, Xiaoli; Carr, Peter W.

    2011-01-01

    Anionic species with ion pair forming ability are commonly used to enhance the retention and efficiency of basic analytes in RPLC separations. However, little is known about the interactions between organic mobile phase modifiers and such ion pairing anions. In this work, we measured the magnitude of the retention increase of basic drugs and peptides upon addition of strong inorganic ion pairing anions (e.g. perchlorate) as a function of the volume fraction of modifier in acidic water-acetonitrile mobile phases on two different stationary phases. We found that the increase in retention upon addition of various salts depended strongly on the eluent strength. In general, larger retention increases upon addition of the anion were observed at higher organic fractions. Regression of retention against the volume fraction of organic modifier indicated that the ion pair forming anions substantially decreased S values while only slightly changing ln k’w values. The decrease in S is the major cause of the retention increase of basic drugs and peptides when such anions are added to the mobile phase. PMID:17448482

  1. Constraints on cosmic ray production from broad-band observations and modeling of the supernova remnant G347.3-0.5

    NASA Astrophysics Data System (ADS)

    Ellison, D.; Slane, P.; Gaensler, M. B.

    2001-08-01

    The supernova remnant G347.3 0.5 emits a featureless power-law in X-rays, thought to indicate shock-acceleration of electrons to high energies. We here produce a broad-band spectrum of the bright NW limb of this source by combin-ing radio observations from the Australia Telescope Compact Array (ATCA), X-ray observations from the Advanced Satellite for Cosmology and Astro-physics (ASCA), and TeV γ-ray observations from the CANGAROO imaging Cerenkov telescope. We assume this emission is produced by an electron popu-lation generated by diffusive shock acceleration at the remnant forward shock. The nonlinear aspects of the particle acceleration force a connection between the widely different wavelength bands and between the electrons and the unseen ions, presumably accelerated simultaneously with the electrons. This allows us to infer the relativistic proton spectrum and estimate ambient parameters such as the supernova explosion energy, magnetic field, matter density, and efficiency of the shock acceleration process. We find convincing evidence that the shock acceleration is efficient, placing > 20% of the shock kinetic energy ux into rel-ativistic ions. However, we find that the maximum electron and proton energies depend somewhat on assumptions for the compression of the magnetic field in the shock, but are generally well below the observed knee at ˜ 1015 eV in the galactic cosmic-ray spectrum. We discuss implications of this for theories of cosmic-ray origin.

  2. Photometric Constraints on the Redshift of z ~ 10 Candidate UDFj-39546284 from Deeper WFC3/IR+ACS+IRAC Observations over the HUDF

    NASA Astrophysics Data System (ADS)

    Bouwens, R. J.; Oesch, P. A.; Illingworth, G. D.; Labbé, I.; van Dokkum, P. G.; Brammer, G.; Magee, D.; Spitler, L. R.; Franx, M.; Smit, R.; Trenti, M.; Gonzalez, V.; Carollo, C. M.

    2013-03-01

    Ultra-deep WFC3/IR observations on the HUDF from the HUDF09 program revealed just one plausible z ~ 10 candidate, UDFj-39546284. UDFj-39546284 had all the properties expected of a galaxy at z ~ 10 showing (1) no detection in the deep ACS+WFC3 imaging data blueward of the F160W band, exhibiting (2) a blue spectral slope redward of the break, and showing (3) no prominent detection in deep IRAC observations. The new, similarly deep WFC3/IR HUDF12 F160W observations over the HUDF09/XDF allow us to further assess this candidate. These observations show that this candidate, previously only detected at ~5.9σ in a single band, clearly corresponds to a real source. It is detected at ~5.3σ in the new H 160-band data and at ~7.8σ in the full 85-orbit H 160-band stack. Interestingly, the non-detection of the source (<1σ) in the new F140W observations suggests a higher redshift. Formally, the best-fit redshift of the source utilizing all the WFC3+ACS (and IRAC+Ks -band) observations is 11.8 ± 0.3. However, we consider the z ~ 12 interpretation somewhat unlikely, since the source would either need to be ~20× more luminous than expected or show very high-EW Lyα emission (which seems improbable given the extensive neutral gas prevalent early in the reionization epoch). Lower-redshift solutions fail if only continuum models are allowed. Plausible lower-redshift solutions require that the H 160-band flux be dominated by line emission such as Hα or [O III] with extreme EWs. The tentative detection of line emission at 1.6 μm in UDFj-39546284 in a companion paper suggests that such emission may have already been found. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained by the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  3. Data assimilation with inequality constraints

    NASA Astrophysics Data System (ADS)

    Thacker, W. C.

    If values of variables in a numerical model are limited to specified ranges, these restrictions should be enforced when data are assimilated. The simplest option is to assimilate without regard for constraints and then to correct any violations without worrying about additional corrections implied by correlated errors. This paper addresses the incorporation of inequality constraints into the standard variational framework of optimal interpolation with emphasis on our limited knowledge of the underlying probability distributions. Simple examples involving only two or three variables are used to illustrate graphically how active constraints can be treated as error-free data when background errors obey a truncated multi-normal distribution. Using Lagrange multipliers, the formalism is expanded to encompass the active constraints. Two algorithms are presented, both relying on a solution ignoring the inequality constraints to discover violations to be enforced. While explicitly enforcing a subset can, via correlations, correct the others, pragmatism based on our poor knowledge of the underlying probability distributions suggests the expedient of enforcing them all explicitly to avoid the computationally expensive task of determining the minimum active set. If additional violations are encountered with these solutions, the process can be repeated. Simple examples are used to illustrate the algorithms and to examine the nature of the corrections implied by correlated errors.

  4. PHOTOMETRIC CONSTRAINTS ON THE REDSHIFT OF z {approx} 10 CANDIDATE UDFj-39546284 FROM DEEPER WFC3/IR+ACS+IRAC OBSERVATIONS OVER THE HUDF

    SciTech Connect

    Bouwens, R. J.; Labbe, I.; Franx, M.; Smit, R.; Oesch, P. A.; Illingworth, G. D.; Magee, D.; Gonzalez, V.; Brammer, G.; Spitler, L. R.; Trenti, M.; Carollo, C. M.

    2013-03-01

    Ultra-deep WFC3/IR observations on the HUDF from the HUDF09 program revealed just one plausible z {approx} 10 candidate, UDFj-39546284. UDFj-39546284 had all the properties expected of a galaxy at z {approx} 10 showing (1) no detection in the deep ACS+WFC3 imaging data blueward of the F160W band, exhibiting (2) a blue spectral slope redward of the break, and showing (3) no prominent detection in deep IRAC observations. The new, similarly deep WFC3/IR HUDF12 F160W observations over the HUDF09/XDF allow us to further assess this candidate. These observations show that this candidate, previously only detected at {approx}5.9{sigma} in a single band, clearly corresponds to a real source. It is detected at {approx}5.3{sigma} in the new H{sub 160}-band data and at {approx}7.8{sigma} in the full 85-orbit H{sub 160}-band stack. Interestingly, the non-detection of the source (<1{sigma}) in the new F140W observations suggests a higher redshift. Formally, the best-fit redshift of the source utilizing all the WFC3+ACS (and IRAC+K{sub s} -band) observations is 11.8 {+-} 0.3. However, we consider the z {approx} 12 interpretation somewhat unlikely, since the source would either need to be {approx}20 Multiplication-Sign more luminous than expected or show very high-EW Ly{alpha} emission (which seems improbable given the extensive neutral gas prevalent early in the reionization epoch). Lower-redshift solutions fail if only continuum models are allowed. Plausible lower-redshift solutions require that the H{sub 160}-band flux be dominated by line emission such as H{alpha} or [O III] with extreme EWs. The tentative detection of line emission at 1.6 {mu}m in UDFj-39546284 in a companion paper suggests that such emission may have already been found.

  5. Spatially resolving methane emissions in California: constraints from the CalNex aircraft campaign and from present (GOSAT, TES) and future (TROPOMI, geostationary) satellite observations

    NASA Astrophysics Data System (ADS)

    Wecht, K. J.; Jacob, D. J.; Sulprizio, M. P.; Santoni, G. W.; Wofsy, S. C.; Parker, R.; Bösch, H.; Worden, J.

    2014-02-01

    We apply a continental-scale inverse modeling system for North America based on the GEOS-Chem model to optimize California methane emissions at 1/2° × 2/3° horizontal resolution using atmospheric observations from the CalNex aircraft campaign (May-June 2010) and from satellites. Inversion of the CalNex data yields a best estimate for total California methane emissions of 2.86 ± 0.21 Tg yr-1, compared with 1.92 Tg yr-1 in the EDGAR v4.2 emission inventory used as a priori and 1.51 Tg yr-1 in the California Air Resources Board (CARB) inventory used for state regulations of greenhouse gas emissions. These results are consistent with a previous Lagrangian inversion of the CalNex data. Our inversion provides 12 independent pieces of information to constrain the geographical distribution of emissions within California. Attribution to individual source types indicates dominant contributions to emissions from landfills/wastewater (1.1 Tg yr-1), livestock (0.87 Tg yr-1), and gas/oil (0.64 Tg yr-1). EDGAR v4.2 underestimates emissions from livestock while CARB underestimates emissions from landfills/wastewater and gas/oil. Current satellite observations from GOSAT can constrain methane emissions in the Los Angeles Basin but are too sparse to constrain emissions quantitatively elsewhere in California (they can still be qualitatively useful to diagnose inventory biases). Los Angeles Basin emissions derived from CalNex and GOSAT inversions are 0.42 ± 0.08 and 0.31 ± 0.08, respectively. An observation system simulation experiment (OSSE) shows that the future TROPOMI satellite instrument (2015 launch) will be able to constrain California methane emissions at a detail comparable to the CalNex aircraft campaign. Geostationary satellite observations offer even greater potential for constraining methane emissions in the future.

  6. Mid-J CO shock tracing observations of infrared dark clouds. II. Low-J CO constraints on excitation, depletion, and kinematics

    NASA Astrophysics Data System (ADS)

    Pon, A.; Johnstone, D.; Caselli, P.; Fontani, F.; Palau, A.; Butler, M. J.; Kaufman, M.; Jiménez-Serra, I.; Tan, J. C.

    2016-03-01

    Infrared dark clouds are kinematically complex molecular structures in the interstellar medium that can host sites of massive star formation. We present maps measuring 4 square arcminutes of the 12CO, 13CO, and C18O J = 3 to 2 lines from selected locations within the C and F (G028.37+00.07 and G034.43+00.24) infrared dark clouds (IRDCs), as well as single pointing observations of the 13CO and C18O J = 2 to 1 lines towards three cores within these clouds. We derive CO gas temperatures throughout the maps and find that CO is significantly frozen out within these IRDCs. We find that the CO depletion tends to be the highest near column density peaks with maximum depletion factors between 5 and 9 in IRDC F and between 16 and 31 in IRDC C. We also detect multiple velocity components and complex kinematic structure in both IRDCs. Therefore, the kinematics of IRDCs seem to point to dynamically evolving structures yielding dense cores with considerable depletion factors. Based on observations carried out with the JCMT and IRAM 30 m Telescopes. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).IRAM CO observations are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A96

  7. Constraint monitoring in TOSCA

    NASA Technical Reports Server (NTRS)

    Beck, Howard

    1992-01-01

    The Job-Shop Scheduling Problem (JSSP) deals with the allocation of resources over time to factory operations. Allocations are subject to various constraints (e.g., production precedence relationships, factory capacity constraints, and limits on the allowable number of machine setups) which must be satisfied for a schedule to be valid. The identification of constraint violations and the monitoring of constraint threats plays a vital role in schedule generation in terms of the following: (1) directing the scheduling process; and (2) informing scheduling decisions. This paper describes a general mechanism for identifying constraint violations and monitoring threats to the satisfaction of constraints throughout schedule generation.

  8. Spatially resolving methane emissions in California: constraints from the CalNex aircraft campaign and from present (GOSAT, TES) and future (TROPOMI, geostationary) satellite observations

    NASA Astrophysics Data System (ADS)

    Wecht, K. J.; Jacob, D. J.; Sulprizio, M. P.; Santoni, G. W.; Wofsy, S. C.; Parker, R.; Bösch, H.; Worden, J.

    2014-08-01

    We apply a continental-scale inverse modeling system for North America based on the GEOS-Chem model to optimize California methane emissions at 1/2° × 2/3° horizontal resolution using atmospheric observations from the CalNex aircraft campaign (May-June 2010) and from satellites. Inversion of the CalNex data yields a best estimate for total California methane emissions of 2.86 ± 0.21 Tg a-1, compared with 1.92 Tg a-1 in the EDGAR v4.2 emission inventory used as a priori and 1.51 Tg a-1 in the California Air Resources Board (CARB) inventory used for state regulations of greenhouse gas emissions. These results are consistent with a previous Lagrangian inversion of the CalNex data. Our inversion provides 12 independent pieces of information to constrain the geographical distribution of emissions within California. Attribution to individual source types indicates dominant contributions to emissions from landfills/wastewater (1.1 Tg a-1), livestock (0.87 Tg a-1), and gas/oil (0.64 Tg a-1). EDGAR v4.2 underestimates emissions from livestock, while CARB underestimates emissions from landfills/wastewater and gas/oil. Current satellite observations from GOSAT can constrain methane emissions in the Los Angeles Basin but are too sparse to constrain emissions quantitatively elsewhere in California (they can still be qualitatively useful to diagnose inventory biases). Los Angeles Basin emissions derived from CalNex and GOSAT inversions are 0.42 ± 0.08 and 0.31 ± 0.08 Tg a-1 that the future TROPOMI satellite instrument (2015 launch) will be able to constrain California methane emissions at a detail comparable to the CalNex aircraft campaign. Geostationary satellite observations offer even greater potential for constraining methane emissions in the future.

  9. Constraints on holographic cosmologies from strong lensing systems

    SciTech Connect

    Cárdenas, Víctor H.; Bonilla, Alexander; Motta, Verónica; Campo, Sergio del E-mail: alex.bonilla@uv.cl E-mail: sdelcamp@ucv.cl

    2013-11-01

    We use strongly gravitationally lensed (SGL) systems to put additional constraints on a set of holographic dark energy models. Data available in the literature (redshift and velocity dispersion) is used to obtain the Einstein radius and compare it with model predictions. We found that the ΛCDM is the best fit to the data. Although a preliminary statistical analysis seems to indicate that two of the holographic models studied show interesting agreement with observations, a stringent test lead us to the result that neither of the holographic models are competitive with the ΛCDM. These results highlight the importance of Strong Lensing measurements to provide additional observational constraints to alternative cosmological models, which are necessary to shed some light into the dark universe.

  10. New constraints on the sulfur reservoir in the dense interstellar medium provided by Spitzer observations of S I in shocked gas

    SciTech Connect

    Anderson, Dana E.; Bergin, Edwin A.; Maret, Sébastien

    2013-12-20

    We present observations of fine-structure line emission of atomic sulfur, iron, and rotational lines of molecular hydrogen in shocks associated with several Class 0 protostars obtained with the Infrared Spectrograph of the Spitzer Space Telescope. We use these observations to investigate the 'missing sulfur problem', that significantly less sulfur is found in dense regions of the interstellar medium (ISM) than in diffuse regions. For sources where the sulfur fine-structure line emission is co-spatial with the detected molecular hydrogen emission and in the presence of weak iron emission, we derive sulfur and H{sub 2} column densities for the associated molecule-dominated C-shocks. We find the S I abundance to be ≳5%-10% of the cosmic sulfur abundance, indicating that atomic sulfur is a major reservoir of sulfur in shocked gas. This result suggests that in the quiescent dense ISM sulfur is present in some form that is released from grains as atoms, perhaps via sputtering, within the shock.

  11. CO (J = 1-0) Observation of the cD Galaxy of AWM 7: Constraints on the Evaporation of Molecular Gas

    NASA Astrophysics Data System (ADS)

    Fujita, Yutaka; Tosaki, Tomoka; Nakamichi, Akika; Kuno, Nario

    2000-04-01

    We have searched for molecular gas in the cD galaxy of a poor cluster of galaxies, AWM 7, using the Nobeyama 45 m telescope. We did not detect CO emission in the galaxy. Our limit of molecular gas in the inner 7.5 kpc is M_H_2< 4times 108 MO . We estimate the total mass of molecular gas left in the cD galaxy when the gas deposited by a cooling flow once becomes molecular gas and the molecular gas is continuously evaporated by the ambient hot gas. The observational limit of molecular gas requires f>~ 10-3, where f is the ratio of the heat conduction rate to that of Spitzer. However, this contradicts recent X-ray observations showing f<10-5. Thus, the non-detection of CO cannot be explained by evaporation, and most of the cooled gas predicted by a cooling flow model may not change into molecular gas in the cD galaxy. Moreover, we estimate the evaporation time of molecular clouds brought to a cD galaxy through the capture of gas-rich galaxies and find that these clouds should not be evaporated if f<~ 10-3-10-4. Therefore, the non-detection of CO in a cD galaxy could constrain the total mass of the molecular clouds brought into it.

  12. Effects of Ag addition on FePt L10 ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Gao, Tenghua; Yu, Youxing

    2015-12-01

    FePt and (FePt)91.2Ag8.8 alloy films were deposited by magnetron sputtering. The average coercivity of (FePt)91.2Ag8.8 films reaches 8.51 × 105 A/m, which is 0.63 × 105 A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L10 ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution reveals more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L10 ordering transition.

  13. Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

    NASA Astrophysics Data System (ADS)

    Turner, Jake D.; Pearson, Kyle A.; Biddle, Lauren I.; Smart, Brianna M.; Zellem, Robert T.; Teske, Johanna K.; Hardegree-Ullman, Kevin K.; Griffith, Caitlin C.; Leiter, Robin M.; Cates, Ian T.; Nieberding, Megan N.; Smith, Carter-Thaxton W.; Thompson, Robert M.; Hofmann, Ryan; Berube, Michael P.; Nguyen, Chi H.; Small, Lindsay C.; Guvenen, Blythe C.; Richardson, Logan; McGraw, Allison; Raphael, Brandon; Crawford, Benjamin E.; Robertson, Amy N.; Tombleson, Ryan; Carleton, Timothy M.; Towner, Allison P. M.; Walker-LaFollette, Amanda M.; Hume, Jeffrey R.; Watson, Zachary T.; Jones, Christen K.; Lichtenberger, Matthew J.; Hoglund, Shelby R.; Cook, Kendall L.; Crossen, Cory A.; Jorgensen, Curtis R.; Romine, James M.; Thompson, Alejandro R.; Villegas, Christian F.; Wilson, Ashley A.; Sanford, Brent; Taylor, Joanna M.; Henz, Triana N.

    2016-06-01

    Transits of exoplanets observed in the near-UV have been used to study the scattering properties of their atmospheres and possible star-planet interactions. We observed the primary transits of 15 exoplanets (CoRoT-1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-16b, HAT-P-22b, TrES-2b, TrES-4b, WASP-1b, WASP-12b, WASP-33b, WASP-36b, WASP-44b, WASP-48b, and WASP-77Ab) in the near-UV and several optical photometric bands to update their planetary parameters, ephemerides, search for a wavelength dependence in their transit depths to constrain their atmospheres, and determine if asymmetries are visible in their light curves. Here, we present the first ground-based near-UV light curves for 12 of the targets (CoRoT-1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-1b, WASP-33b, WASP-36b, WASP-48b, and WASP-77Ab). We find that none of the near-UV transits exhibit any non-spherical asymmetries, this result is consistent with recent theoretical predictions by Ben-Jaffel et al. and Turner et al. The multiwavelength photometry indicates a constant transit depth from near-UV to optical wavelengths in 10 targets (suggestive of clouds), and a varying transit depth with wavelength in 5 targets (hinting at Rayleigh or aerosol scattering in their atmospheres). We also present the first detection of a smaller near-UV transit depth than that measured in the optical in WASP-1b and a possible opacity source that can cause such radius variations is currently unknown. WASP-36b also exhibits a smaller near-UV transit depth at 2.6σ. Further observations are encouraged to confirm the transit depth variations seen in this study.

  14. Constraints on the presence of a 3.5 keV dark matter emission line from Chandra observations of the Galactic centre

    NASA Astrophysics Data System (ADS)

    Riemer-Sørensen, Signe

    2016-05-01

    Context. Recent findings of line emission at 3.5 keV in both individual and stacked X-ray spectra of galaxy clusters have been speculated to have dark matter origin. Aims: If the origin is indeed dark matter, the emission line is expected to be detectable from the Milky Way dark matter halo. Methods: We perform a line search in public Chandra X-ray observations of the region near Sgr A*. We derive upper limits on the line emission flux for the 2.0-9.0 keV energy interval and discuss their potential physical interpretations including various scenarios of decaying and annihilating dark matter. Results: While we find no clear evidence for its presence, the upper flux limits are not inconsistent with the recent detections for conservative mass profiles of the Milky Way. Conclusions: The results depend mildly on the spectral modelling, and strongly on the choice of dark matter profile.

  15. Seeing red in M32: Constraints on the stellar content from near- and mid-infrared observations and applications for studies of more distant galaxies {sup ,} {sup ,}

    SciTech Connect

    Davidge, T. J.

    2014-08-10

    The properties of asymptotic giant branch (AGB) stars in the Local Group galaxy M32 are investigated using ground- and space-based observations that span the 1-8 μm wavelength interval, with the goal of demonstrating the utility of infrared observations as probes of stellar content. Comparisons with isochrones indicate that the brightest resolved stars in M32 have ages of a few gigayears and are younger on average than AGB stars with the same intrinsic brightness in the outer disk of M31. Accounting for stellar variability is shown to be essential for modeling AGB luminosity functions (LFs). Model LFs that assume the star-forming history measured by Monachesi et al. and the variability properties of Galactic AGB stars match both the K and [5.8] LFs of M32. Models also suggest that the slope of the [5.8] LF between M{sub [5.8]} = –8.5 and –10.0 is sensitive to the mix of stellar ages, and a sizeable fraction of the stars in M32 must have an age older than 7 Gyr in order to match the [5.8] LF. The structural properties of M32 in the infrared are also investigated. The effective radii that are computed from near-infrared and mid-infrared isophotes are similar to those measured at visible wavelengths, suggesting that the stellar content of M32 is well mixed. However, isophotes at radii >16'' (>60 pc) in the near- and mid-infrared are flatter than those at visible wavelengths. The coefficient of the fourth-order cosine term in the Fourier expansion of isophotes changes from 'boxy' values at r < 16'' to 'disky' values at r > 48''in [3.6] and [4.5]. The mid-infrared colors near the center of M32 do not vary systematically with radius, providing evidence of a well mixed stellar content in this part of the galaxy.

  16. New constraints on micro-seismicity and stress state in the western part of the North Anatolian Fault Zone: Observations from a dense seismic array

    NASA Astrophysics Data System (ADS)

    Altuncu Poyraz, Selda; Teoman, M. Uğur; Türkelli, Niyazi; Kahraman, Metin; Cambaz, Didem; Mutlu, Ahu; Rost, Sebastian; Houseman, Gregory A.; Thompson, David A.; Cornwell, David; Utkucu, Murat; Gülen, Levent

    2015-08-01

    With the aim of extensively investigating the crustal structure beneath the western segment of the North Anatolian Fault Zone where it splays into northern and southern branches, a temporary seismic network (dense array for North Anatolia-DANA) consisting of 70 stations was deployed in early May 2012 and operated for 18 months in the Sakarya region during the FaultLab experiment. Out of 2437 events contaminated by explosions, we extracted 1371 well located earthquakes. The enhanced station coverage having a nominal station spacing of 7 km, lead to a minimum magnitude calculation of 0.1. Horizontal and vertical location uncertainties within the array do not exceed 0.8 km and 0.9 km, respectively. We observe considerable seismic activity along both branches of the fault where the depth of the seismogenic zone was mostly confined to 15 km. Using our current earthquake catalog we obtained a b-value of 1. We also mapped the b-value variation with depth and observed a gradual decrease. Furthermore, we determined the source parameters of 41 earthquakes with magnitudes greater than 1.8 using P-wave first motion polarity method. Regional Moment Tensor Inversion method was also applied to earthquakes with magnitudes greater than 3.0. Focal mechanism solutions confirm that Sakarya and its vicinity is stressed by a compressional regime showing a primarily oblique-slip motion character. Stress tensor analysis indicates that the maximum principal stress is aligned in WNW-ESE direction and the tensional axis is aligned in NNE-SSW direction.

  17. Optimality criteria design and stress constraint processing

    NASA Technical Reports Server (NTRS)

    Levy, R.

    1982-01-01

    Methods for pre-screening stress constraints into either primary or side-constraint categories are reviewed; a projection method, which is developed from prior cycle stress resultant history, is introduced as an additional screening parameter. Stress resultant projections are also employed to modify the traditional stress-ratio, side-constraint boundary. A special application of structural modification reanalysis is applied to the critical stress constraints to provide feasible designs that are preferable to those obtained by conventional scaling. Sample problem executions show relatively short run times and fewer design cycle iterations to achieve low structural weights; those attained are comparable to the minimum values developed elsewhere.

  18. Keck and VLT Observations of Super-Damped Lyman-Alpha Absorbers at z 2- 2.5: Constraints on Chemical Compositions and Physical Conditions

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varsha P.; Som, Debopam; Morrison, Sean; Péroux, Celine; Quiret, Samuel; York, Donald G.

    2015-12-01

    We report Keck/Echellette Spectrograph and Imager and Very Large Telescope/Ultraviolet-Visual Echelle Spectrograph observations of three super-damped Lyα quasar absorbers with H i column densities log NH i ≥ 21.7 at redshifts 2 ≲ z ≲ 2.5. All three absorbers show similar metallicities (˜-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other damped Lyα a absorbers (DLAs) to examine trends between NH i, metallicity, and dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H] = 20.59 - log NH i in the metallicity versus NH i plot, compared to the less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Unfortunately, our data for Q0230-0334 and Q0743+1421 do not cover H2 absorption lines. For Q1418+0718, some H2 lines are covered, but not detected. CO is not detected in any of our absorbers. For DLAs with log NH i < 21.7, we confirm strong correlation between metallicity and Fe depletion, and find a correlation between metallicity and Si depletion. For super-DLAs, these correlations are weaker or absent. The absorbers toward Q0230-0334 and Q1418+0718 show potential detections of weak Lyα emission, implying star formation rates of ˜1.6 and ˜0.7 M⊙ yr-1, respectively (ignoring dust extinction). Upper limits on the electron densities from C ii*/C ii or Si ii*/Si ii are low, but are higher than the median values in less gas-rich DLAs. Finally, systems with log NH i > 21.7 may have somewhat narrower velocity dispersions Δv90 than the less gas-rich DLAs, and may arise in cooler and/or less turbulent gas. Includes observations collected during program ESO 93.A-0422 at the European Southern Observatory (ESO) Very Large Telescope (VLT) with the Ultraviolet-Visual Echelle Spectrograph (UVES) on the 8.2 m telescopes operated at the Paranal Observatory, Chile. Some of the data presented herein were

  19. Seeing Red in M32: Constraints on the Stellar Content from Near- and Mid-infrared Observations and Applications for Studies of More Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2014-08-01

    The properties of asymptotic giant branch (AGB) stars in the Local Group galaxy M32 are investigated using ground- and space-based observations that span the 1-8 μm wavelength interval, with the goal of demonstrating the utility of infrared observations as probes of stellar content. Comparisons with isochrones indicate that the brightest resolved stars in M32 have ages of a few gigayears and are younger on average than AGB stars with the same intrinsic brightness in the outer disk of M31. Accounting for stellar variability is shown to be essential for modeling AGB luminosity functions (LFs). Model LFs that assume the star-forming history measured by Monachesi et al. and the variability properties of Galactic AGB stars match both the K and [5.8] LFs of M32. Models also suggest that the slope of the [5.8] LF between M [5.8] = -8.5 and -10.0 is sensitive to the mix of stellar ages, and a sizeable fraction of the stars in M32 must have an age older than 7 Gyr in order to match the [5.8] LF. The structural properties of M32 in the infrared are also investigated. The effective radii that are computed from near-infrared and mid-infrared isophotes are similar to those measured at visible wavelengths, suggesting that the stellar content of M32 is well mixed. However, isophotes at radii >16'' (>60 pc) in the near- and mid-infrared are flatter than those at visible wavelengths. The coefficient of the fourth-order cosine term in the Fourier expansion of isophotes changes from "boxy" values at r < 16'' to "disky" values at r > 48''in [3.6] and [4.5]. The mid-infrared colors near the center of M32 do not vary systematically with radius, providing evidence of a well mixed stellar content in this part of the galaxy. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  20. Gamma-ray observational constraints on the origin of the optical continuum emission from the white-light flare of 1980 July 1

    NASA Technical Reports Server (NTRS)

    Ryan, J. M.; Chupp, E. L.; Forrest, D. J.; Matz, S. M.; Rieger, E.; Reppin, C.; Kanbach, G.; Share, G. H.

    1983-01-01

    Results are presented for the flare of July 1, 1980, which started at approximately 1627 UT and in which simultaneous measurements were made of X-ray, gamma-ray, and optical continuum emission for the entire duration of the flare. The X-ray and gamma-ray observations were made by the Gamma-Ray Spectrometer on the Solar Maximum Mission satellite. The optical measurements were taken at the Sacramento Peak Observatory and the Big Bear Solar Observatory (Zirin and Neidig, 1981). It is found that the major white-light emission that occurs in the late phase of the flare could not have been due to heating by electron or ion precipitation. This conclusion derives from the fact that the X-ray and gamma-ray flux peaks approximately 1 minute before the maximum of the optical continuum mission emission. It is also found that approximately 73 percent of the optical continuum emission, representing a spatially and temporally distinct bright point, follows this maximum with little or no X-ray or gamma-ray emission in the same period.

  1. HST-COS Observations of AGNs. III. Spectral Constraints in the Lyman Continuum from Composite COS/G140L Data

    NASA Astrophysics Data System (ADS)

    Tilton, Evan M.; Stevans, Matthew L.; Shull, J. Michael; Danforth, Charles W.

    2016-01-01

    The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well characterized with composite spectra at wavelengths greater than 912 Å, the shorter-wavelength extreme-UV (EUV) remains poorly studied. In this third paper in a series on the spectra of AGNs, we combine 11 new spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope with archival spectra to characterize the typical EUV spectral slope of AGNs from λrest ˜ 850 Å down to λrest ˜ 425 Å. Parameterizing this slope as a power law, we obtain Fν ∝ ν-0.72±0.26, but we also discuss the limitations and systematic uncertainties of this model. We identify broad emission features in this spectral region, including emission due to ions of O, Ne, Mg, and other species, and we limit the intrinsic He i 504 Å photoelectric absorption edge opacity to τHe i < 0.047. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  2. Shear wave splitting observations across the Juan de Fuca plate system: Ridge- to-trench constraints on mantle flow from 2 years of Cascadia Initiative OBS data

    NASA Astrophysics Data System (ADS)

    Bodmer, M.; Toomey, D. R.; Hooft, E. E. E.

    2014-12-01

    We present SKS splitting measurements for the first two years of data collected by the Cascadia Initiative (CI) amphibious array. Our analysis includes observations from over 100 ocean bottom seismometers (OBS), as well as 31 onshore stations, and spans both the Juan de Fuca and Gorda plates. The CI dataset is unique in that it includes several regions that can distinctly influence anisotropic fabric development such as: the upwelling mantle beneath the Juan de Fuca and Gorda ridges, the young evolving oceanic lithosphere of the plate interior, the Blanco transform fault, and the Cascadia subduction zone. For the first time, we are able to analyze these regions with a single dataset, and using a common methodology. Splitting measurements are routinely done on land sites, but have been completed on relatively few OBS stations. This is largely due to the low signal to noise present in OBS data, which can obscure the splitting results. To address that nearly all the OBS data exceeds the global high noise limit at the frequencies used for splitting, we implement a rigorous quality control scheme. Our method specifically takes into account the response of common splitting methods to high noise data and addresses known issues such as cycle skipping, false minima, low transverse energy, and near-null measurements. Individual measurements are filtered at 0.03-0.1 Hz, manually checked for quality, and stacked. Preliminary results show trench perpendicular onshore measurements consistent with previous studies. Oceanic measurements in the plate interior show a coherent fast axis roughly aligned with absolute plate motion. Several measurements near the ridge and trench appear to be rotated in the ridge and trench parallel directions. Continuing work will integrate splitting measurements from the final two years of the CI with these findings, which will be used to characterize the ridge-to-trench mantle flow across the Juan de Fuca plate system.

  3. The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A: Constraints on Abundances in the Accreting Material

    NASA Technical Reports Server (NTRS)

    Markowitz, A.; Takahashi, T.A; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J. N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-01-01

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  4. The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-time Observations, First-light Time, Distance to NGC 4666, and Progenitor Constraints

    NASA Astrophysics Data System (ADS)

    Shappee, B. J.; Piro, A. L.; Holoien, T. W.-S.; Prieto, J. L.; Contreras, C.; Itagaki, K.; Burns, C. R.; Kochanek, C. S.; Stanek, K. Z.; Alper, E.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Conseil, E.; Danilet, A. B.; Dong, Subo; Falco, E.; Grupe, D.; Hsiao, E. Y.; Kiyota, S.; Morrell, N.; Nicolas, J.; Phillips, M. M.; Pojmanski, G.; Simonian, G.; Stritzinger, M.; Szczygieł, D. M.; Taddia, F.; Thompson, T. A.; Thorstensen, J.; Wagner, M. R.; Woźniak, P. R.

    2016-08-01

    On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or “Assassin”) discovered ASASSN-14lp just ∼2 days after first light using a global array of 14 cm diameter telescopes. ASASSN-14lp went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ({{Δ }}{m}15(B)=0.80+/- 0.05), a B-band maximum at 2457015.82 ± 0.03, a rise time of {16.94}-0.10+0.11 days, and moderate host-galaxy extinction (E{(B-V)}{host}=0.33+/- 0.06). Using ASASSN-14lp, we derive a distance modulus for NGC 4666 of μ =30.8+/- 0.2, corresponding to a distance of 14.7 ± 1.5 Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 {R}ȯ .

  5. GOCE observations and geophysical constraints to better understand the lithosphere and geodynamical processes under the Paraná-Etendeka region: preliminary results of PERLA project

    NASA Astrophysics Data System (ADS)

    Mariani, Patrizia; Braitenberg, Carla

    2014-05-01

    In the light of the considerable progress made by the modern geodetic satellite mission GOCE, one of the challenges of the European Space Agency (ESA) is to improve knowledge of physical properties and geodynamic processes of the lithosphere and the Earth deep interior, and their relationship to Earth-surface changes. In this context we propose a study that aims to understand the two pieces of lithosphere underlying the Paraná-Etendeka conjugate margins (Brazil, and Angola-Namibia). It is essential to collect the geological and geophysical information about the thickness and the density of sedimentary layers, crustal thickness and mantle inhomogeneities. Our methodology integrates the geophysical database with the GOCE data, product of the innovative gravity satellite mission, that was concluded November 2013. Crustal thickness was obtained from all available seismological datasets. The density-depth relation of the shallow layers is modeled by geophysical data collected from literature and from the on-shore and off-shore drilling programs. Several compaction laws are used to estimate the density of each layer. This information is necessary to reduce the observations considering the gravity effect of all intracrustal known layers, to resolve the deep crustal structures (e.g. Moho and intracrustal bodies). A positive gravity anomaly is expected due to the magmatic activity of the Paraná-Etendeka province. The smaller-scale and shallow gravity anomaly should be due to the occurrence of the volcanic activity close to the alkaline-carbonatite complexes, while the large-scale anomaly is expected from the underplating of a wide denser body at the depth of the crustal mantle boundary. In the present work some preliminary results of the inversion of the residual gravity anomaly in terms of densities in the middle and shallow lithosphere under the Paraná-Etendeka region will be presented and interpreted.

  6. The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-time Observations, First-light Time, Distance to NGC 4666, and Progenitor Constraints

    NASA Astrophysics Data System (ADS)

    Shappee, B. J.; Piro, A. L.; Holoien, T. W.-S.; Prieto, J. L.; Contreras, C.; Itagaki, K.; Burns, C. R.; Kochanek, C. S.; Stanek, K. Z.; Alper, E.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Conseil, E.; Danilet, A. B.; Dong, Subo; Falco, E.; Grupe, D.; Hsiao, E. Y.; Kiyota, S.; Morrell, N.; Nicolas, J.; Phillips, M. M.; Pojmanski, G.; Simonian, G.; Stritzinger, M.; Szczygieł, D. M.; Taddia, F.; Thompson, T. A.; Thorstensen, J.; Wagner, M. R.; Woźniak, P. R.

    2016-08-01

    On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or “Assassin”) discovered ASASSN-14lp just ˜2 days after first light using a global array of 14 cm diameter telescopes. ASASSN-14lp went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ({{Δ }}{m}15(B)=0.80+/- 0.05), a B-band maximum at 2457015.82 ± 0.03, a rise time of {16.94}-0.10+0.11 days, and moderate host-galaxy extinction (E{(B-V)}{host}=0.33+/- 0.06). Using ASASSN-14lp, we derive a distance modulus for NGC 4666 of μ =30.8+/- 0.2, corresponding to a distance of 14.7 ± 1.5 Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 {R}ȯ .

  7. The Suzaku Observation of the Nucleus of theRadio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

    SciTech Connect

    Markowitz, A.; Takahashi, T.; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J.N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-06-27

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The net exposure times after screening were: 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X-ray Detector (HXD) PIN, and 17.1 ks for the HXD-GSO. The hard X-rays are fit by two power-laws of the same slope, absorbed by columns of 1.5 and 7 x 10{sup 23} cm{sup -2} respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature vapec model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The Fe K{alpha} line width yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  8. Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

    NASA Astrophysics Data System (ADS)

    He, Cenlin; Li, Qinbin; Liou, Kuo-Nan; Qi, Ling; Tao, Shu; Schwarz, Joshua P.

    2016-03-01

    We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation, coagulation, and heterogeneous chemical oxidation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate (excluding chemical oxidation aging) explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The chemical oxidation aging is tested in the sensitivity simulation. The microphysical aging rate is ˜ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than 5-fold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally, BC microphysical aging is dominated by condensation, while coagulation contribution is largest over eastern China, India, and central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ˜ 3, particularly in the middle and upper troposphere. It also leads to a 3-fold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC

  9. Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

    NASA Astrophysics Data System (ADS)

    He, C.; Li, Q.; Liou, K. N.; Qi, L.; Tao, S.; Schwarz, J. P.

    2015-11-01

    We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation and coagulation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The resulting aging rate is ∼ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than fivefold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally BC microphysical aging is dominated by condensation, while coagulation contribution is largest over East China, India, and Central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ∼ 3, particularly in the middle and upper troposphere. It also leads to a threefold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC deposition. We find that in source regions the microphysical aging rate is insensitive to aerosol size distribution, condensation threshold, and

  10. GEOS-Chem Modeling of Volcanic Aerosol Radiative Forcing: Constraint from OMI SO2 Data and Assessment with NASA's A-Train Satellite Observations

    NASA Astrophysics Data System (ADS)

    Park, S.; Wang, J.; Yang, K.; Carn, S. A.

    2011-12-01

    The volcanic SO2 amount and injection height are key uncertainties for understanding the volcanic aerosol radiative forcing. In the past, many volcanic SO2 emission inventories were based on ground measurements, and the injection height was specified according to volcanic eruption index (VEI), which is a combination of many factors and often does not necessarily reflect eruption altitude. To reduce these uncertainties in the estimate of the volcanic aerosol radiative forcing, we emphasize the use of satellite data to constrain the model simulation, and illustrate our method with a case study of the August 2008 Kasatochi eruption. A 3D global chemical transport model (GEOS-Chem) is initialized by an improved volcanic SO2 emission inventory retrieved from the Ozone Monitoring Instrument (OMI) Iterative Spectral Fitting (ISF) technique that provides accurate amount and injection height of volcanic SO2. The simulations show that the modeled volcanic SO2 plume and sulfate aerosol optical depth are in good agreement with satellite observations both spatially and temporally. GEOS's cloud water path are compared against the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products, and are found to often have a positive bias, indicating that oxidation rate of SO2 in GEOS-Chem model sometimes is too fast. Overall, however, the simulated 9-day e-folding time of the erupted SO2 is consistent with the OMI's stand-alone assessment, suggesting no systematic bias in modeled atmospheric loading of volcanic SO2 and sulfate aerosols. Furthermore, the simulated volcanic sulfate aerosols in the stratosphere are also comparable with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements of aerosols in their vertical distributions. Sulfate aerosol radiative forcing calculated from a four-stream radiative transfer model indicated that the volcanic aerosols were able to impact the shortwave radiative fluxes at the top of the entire Northern Hemispheric

  11. Neural constraints on learning

    PubMed Central

    Sadtler, Patrick T.; Quick, Kristin M.; Golub, Matthew D.; Chase, Steven M.; Ryu, Stephen I.; Tyler-Kabara, Elizabeth C.; Yu, Byron M.; Batista, Aaron P.

    2014-01-01

    Motor, sensory, and cognitive learning require networks of neurons to generate new activity patterns. Because some behaviors are easier to learn than others1,2, we wondered if some neural activity patterns are easier to generate than others. We asked whether the existing network constrains the patterns that a subset of its neurons is capable of exhibiting, and if so, what principles define the constraint. We employed a closed-loop intracortical brain-computer interface (BCI) learning paradigm in which Rhesus monkeys controlled a computer cursor by modulating neural activity patterns in primary motor cortex. Using the BCI paradigm, we could specify and alter how neural activity mapped to cursor velocity. At the start of each session, we observed the characteristic activity patterns of the recorded neural population. These patterns comprise a low-dimensional space (termed the intrinsic manifold, or IM) within the high-dimensional neural firing rate space. They presumably reflect constraints imposed by the underlying neural circuitry. We found that the animals could readily learn to proficiently control the cursor using neural activity patterns that were within the IM. However, animals were less able to learn to proficiently control the cursor using activity patterns that were outside of the IM. This result suggests that the existing structure of a network can shape learning. On the timescale of hours, it appears to be difficult to learn to generate neural activity patterns that are not consistent with the existing network structure. These findings offer a network-level explanation for the observation that we are more readily able to learn new skills when they are related to the skills that we already possess3,4. PMID:25164754

  12. Neural constraints on learning.

    PubMed

    Sadtler, Patrick T; Quick, Kristin M; Golub, Matthew D; Chase, Steven M; Ryu, Stephen I; Tyler-Kabara, Elizabeth C; Yu, Byron M; Batista, Aaron P

    2014-08-28

    Learning, whether motor, sensory or cognitive, requires networks of neurons to generate new activity patterns. As some behaviours are easier to learn than others, we asked if some neural activity patterns are easier to generate than others. Here we investigate whether an existing network constrains the patterns that a subset of its neurons is capable of exhibiting, and if so, what principles define this constraint. We employed a closed-loop intracortical brain-computer interface learning paradigm in which Rhesus macaques (Macaca mulatta) controlled a computer cursor by modulating neural activity patterns in the primary motor cortex. Using the brain-computer interface paradigm, we could specify and alter how neural activity mapped to cursor velocity. At the start of each session, we observed the characteristic activity patterns of the recorded neural population. The activity of a neural population can be represented in a high-dimensional space (termed the neural space), wherein each dimension corresponds to the activity of one neuron. These characteristic activity patterns comprise a low-dimensional subspace (termed the intrinsic manifold) within the neural space. The intrinsic manifold presumably reflects constraints imposed by the underlying neural circuitry. Here we show that the animals could readily learn to proficiently control the cursor using neural activity patterns that were within the intrinsic manifold. However, animals were less able to learn to proficiently control the cursor using activity patterns that were outside of the intrinsic manifold. These results suggest that the existing structure of a network can shape learning. On a timescale of hours, it seems to be difficult to learn to generate neural activity patterns that are not consistent with the existing network structure. These findings offer a network-level explanation for the observation that we are more readily able to learn new skills when they are related to the skills that we already

  13. Constraints on the winds of hot subdwarf stars from X-ray observations of two sdB binaries with compact companions: CD -30° 11223 and PG 1232-136

    NASA Astrophysics Data System (ADS)

    Mereghetti, S.; La Palombara, N.; Esposito, P.; Gastaldello, F.; Tiengo, A.; Heber, U.; Geier, S.; Wilms, J.

    2014-07-01

    Little observational data are available on the weak stellar winds of hot subdwarf stars of B spectral type (sdB). Close binary systems composed of an sdB star and a compact object (white dwarf, neutron star or black hole) could be detected as accretion-powered X-ray sources. The study of their X-ray emission can probe the properties of line-driven winds of sdB stars that cannot be derived directly from spectroscopy because of the low luminosity of these stars. Here we report on the first sensitive X-ray observations of two sdB binaries with compact companions. CD -30° 11223 is the sdB binary with the shortest known orbital period (1.2 h) and its companion is certainly a white dwarf. PG 1232-136 is an sdB binary considered the best candidate to host a black hole companion. We observed these stars with XMM-Newton in 2013 August for 50 ks and in 2009 July for 36 ks, respectively. None of them was detected and we derived luminosity upper limits of ˜1.5 × 1029 erg s-1 for CD -30° 11223 and ˜5 × 1029 erg s-1 for PG 1232-136. The corresponding mass-loss rate for PG 1232-136 is poorly constrained, owing to the unknown efficiency for black hole accretion. On the other hand, in the case of CD -30° 11223 we could derive, under reasonable assumptions, an upper limit of ˜3 × 10-13 M⊙ yr-1 on the wind mass-loss rate from the sdB star. This is one of the few observational constraints on the weak winds expected in this class of low-mass hot stars. We also report the results on the X-ray emission from a cluster of galaxies serendipitously discovered in the field of CD -30° 11223.

  14. Meteoritic and Asteroidal Constraints on the Identification and Collisional Evolution of Asteroid Families

    NASA Technical Reports Server (NTRS)

    Gaffey, Michael J.; Kelley, Michael S.; Hardersen, Paul S.

    2002-01-01

    Studies of meteorites and observations of asteroids can provide important constraints on the formation and evolution of asteroid families. The iron meteorites alone require the disruption of 85 differentiated asteroids, and the potential formation of 85 families. Additional information is contained in the original extended abstract.

  15. Astrophysical and cosmological constraints to neutrino properties

    NASA Technical Reports Server (NTRS)

    Kolb, Edward W.; Schramm, David N.; Turner, Michael S.

    1989-01-01

    The astrophysical and cosmological constraints on neutrino properties (masses, lifetimes, numbers of flavors, etc.) are reviewed. The freeze out of neutrinos in the early Universe are discussed and then the cosmological limits on masses for stable neutrinos are derived. The freeze out argument coupled with observational limits is then used to constrain decaying neutrinos as well. The limits to neutrino properties which follow from SN1987A are then reviewed. The constraint from the big bang nucleosynthesis on the number of neutrino flavors is also considered. Astrophysical constraints on neutrino-mixing as well as future observations of relevance to neutrino physics are briefly discussed.

  16. Temporal Constraint Reasoning With Preferences

    NASA Technical Reports Server (NTRS)

    Khatib, Lina; Morris, Paul; Morris, Robert; Rossi, Francesca

    2001-01-01

    A number of reasoning problems involving the manipulation of temporal information can naturally be viewed as implicitly inducing an ordering of potential local decisions involving time (specifically, associated with durations or orderings of events) on the basis of preferences. For example. a pair of events might be constrained to occur in a certain order, and, in addition. it might be preferable that the delay between them be as large, or as small, as possible. This paper explores problems in which a set of temporal constraints is specified, where each constraint is associated with preference criteria for making local decisions about the events involved in the constraint, and a reasoner must infer a complete solution to the problem such that, to the extent possible, these local preferences are met in the best way. A constraint framework for reasoning about time is generalized to allow for preferences over event distances and durations, and we study the complexity of solving problems in the resulting formalism. It is shown that while in general such problems are NP-hard, some restrictions on the shape of the preference functions, and on the structure of the preference set, can be enforced to achieve tractability. In these cases, a simple generalization of a single-source shortest path algorithm can be used to compute a globally preferred solution in polynomial time.

  17. Maslov complex germ method for systems with second-class constraints

    NASA Astrophysics Data System (ADS)

    Shvedov, O. Yu.

    2016-03-01

    We study the semiclassical mechanics of systems with second-class constraints. We assume that the quantum mechanics of such a system is constructed by the Batalin-Fradkin-Tyutin method, where some additional coordinates and momenta are introduced and second-class constraints are converted into firstclass constraints. We also assume that the algebraic quantization method is used to quantize the extended system. To construct the semiclassical approximation, we use the Maslov complex germ theory. We study the semiclassical states of a system with second-class constraints, their scalar product, and the action of semiclassical observables in the first order of the semiclassical expansion. We consider the transformation of semiclassical states in the course of evolution.

  18. Food additives

    MedlinePlus

    Food additives are substances that become part of a food product when they are added during the processing or making of that food. "Direct" food additives are often added during processing to: Add nutrients ...

  19. Creating Positive Task Constraints

    ERIC Educational Resources Information Center

    Mally, Kristi K.

    2006-01-01

    Constraints are characteristics of the individual, the task, or the environment that mold and shape movement choices and performances. Constraints can be positive--encouraging proficient movements or negative--discouraging movement or promoting ineffective movements. Physical educators must analyze, evaluate, and determine the effect various…

  20. Constraint Reasoning Over Strings

    NASA Technical Reports Server (NTRS)

    Koga, Dennis (Technical Monitor); Golden, Keith; Pang, Wanlin

    2003-01-01

    This paper discusses an approach to representing and reasoning about constraints over strings. We discuss how many string domains can often be concisely represented using regular languages, and how constraints over strings, and domain operations on sets of strings, can be carried out using this representation.

  1. Credit Constraints in Education

    ERIC Educational Resources Information Center

    Lochner, Lance; Monge-Naranjo, Alexander

    2012-01-01

    We review studies of the impact of credit constraints on the accumulation of human capital. Evidence suggests that credit constraints have recently become important for schooling and other aspects of households' behavior. We highlight the importance of early childhood investments, as their response largely determines the impact of credit…

  2. Constraints in Quantum Geometrodynamics

    NASA Astrophysics Data System (ADS)

    Gentle, Adrian P.; George, Nathan D.; Miller, Warner A.; Kheyfets, Arkady

    We compare different treatments of the constraints in canonical quantum gravity. The standard approach on the superspace of 3-geometries treats the constraints as the sole carriers of the dynamic content of the theory, thus rendering the traditional dynamical equations obsolete. Quantization of the constraints in both the Dirac and ADM square root Hamiltonian approaches leads to the well known problems of time evolution. These problems of time are of both an interpretational and technical nature. In contrast, the geometrodynamic quantization procedure on the superspace of the true dynamical variables separates the issues of quantization from the enforcement of the constraints. The resulting theory takes into account states that are off-shell with respect to the constraints, and thus avoids the problems of time. We develop, for the first time, the geometrodynamic quantization formalism in a general setting and show that it retains all essential features previously illustrated in the context of homogeneous cosmologies.

  3. Constraints on Local-­to-­Regional Anthropogenic CO2 from Satellite Retrievals of Combustion-­related Trace Gases: Initial Assessment Using Observing System Simulation Experiments (OSSEs)

    NASA Astrophysics Data System (ADS)

    Arellano, A. F.

    2014-12-01

    Quantifying anthropogenic sources of CO2 is imperative yet challenging. Here, we present data assimilation experiments to assess the information gain in using current satellite observations of atmospheric constituents that are co-­emitted during a combustion process. In particular, OSSEs will be conducted to investigate synergistic information from GOSAT (and OCO-2) CO2, MOPITT (and IASI) CO and OMI NO2 retrievals in constraining sources of anthropogenic combustion at city, state, and regional spatiotemporal scales. These experiments will be carried out using ensemble-­-based data assimilation (DA) system comprising of a regional air quality/weather model, WRF-­Chem, global climate/chemistry model, CAM-Chem, and a data assimilation software package, DART. The ensemble-based DA system, which mimics a numerical weather prediction with chemistry, provides a means to statistically estimate local sensitivities across modeled meteorological and chemical states (CO2, CO, NO2, and related species) and parameters (including surface fluxes) using the ensemble statistics derived from dynamical, physical, and chemical perturbations in the model. We take advantage of these sensitivities in fully exploiting the synergistic information provided by the enhancement ratios that are indicative of combustion characteristic for a given location sampled by these space-­based observations. Here, we introduce a two-­step approach in optimizing anthropogenic CO2. This includes: 1) analysis of atmospheric CO2 distribution using multi-­-species DA, and 2) Bayesian synthesis time-independent inversion using the CO2 analysis as observational constraints. We evaluate the performance of this approach within an OSSE framework, where one realization of simulated atmosphere is assumed to be the 'truth'. Synthetic observations are then derived from this atmosphere using sampling and error characteristics of the retrievals. The assimilation of these synthetic observations will be evaluated

  4. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  5. REPRODUCING THE OBSERVED ABUNDANCES IN RCB AND HdC STARS WITH POST-DOUBLE-DEGENERATE MERGER MODELS-CONSTRAINTS ON MERGER AND POST-MERGER SIMULATIONS AND PHYSICS PROCESSES

    SciTech Connect

    Menon, Athira; Herwig, Falk; Denissenkov, Pavel A.; Clayton, Geoffrey C.; Staff, Jan; Pignatari, Marco; Paxton, Bill

    2013-07-20

    The R Coronae Borealis (RCB) stars are hydrogen-deficient, variable stars that are most likely the result of He-CO WD mergers. They display extremely low oxygen isotopic ratios, {sup 16}O/{sup 18}O {approx_equal} 1-10, {sup 12}C/{sup 13}C {>=} 100, and enhancements up to 2.6 dex in F and in s-process elements from Zn to La, compared to solar. These abundances provide stringent constraints on the physical processes during and after the double-degenerate merger. As shown previously, O-isotopic ratios observed in RCB stars cannot result from the dynamic double-degenerate merger phase, and we now investigate the role of the long-term one-dimensional spherical post-merger evolution and nucleosynthesis based on realistic hydrodynamic merger progenitor models. We adopt a model for extra envelope mixing to represent processes driven by rotation originating in the dynamical merger. Comprehensive nucleosynthesis post-processing simulations for these stellar evolution models reproduce, for the first time, the full range of the observed abundances for almost all the elements measured in RCB stars: {sup 16}O/{sup 18}O ratios between 9 and 15, C-isotopic ratios above 100, and {approx}1.4-2.35 dex F enhancements, along with enrichments in s-process elements. The nucleosynthesis processes in our models constrain the length and temperature in the dynamic merger shell-of-fire feature as well as the envelope mixing in the post-merger phase. s-process elements originate either in the shell-of-fire merger feature or during the post-merger evolution, but the contribution from the asymptotic giant branch progenitors is negligible. The post-merger envelope mixing must eventually cease {approx}10{sup 6} yr after the dynamic merger phase before the star enters the RCB phase.

  6. Seismological Constraints on Geodynamics

    NASA Astrophysics Data System (ADS)

    Lomnitz, C.

    2004-12-01

    Earth is an open thermodynamic system radiating heat energy into space. A transition from geostatic earth models such as PREM to geodynamical models is needed. We discuss possible thermodynamic constraints on the variables that govern the distribution of forces and flows in the deep Earth. In this paper we assume that the temperature distribution is time-invariant, so that all flows vanish at steady state except for the heat flow Jq per unit area (Kuiken, 1994). Superscript 0 will refer to the steady state while x denotes the excited state of the system. We may write σ 0=(J{q}0ṡX{q}0)/T where Xq is the conjugate force corresponding to Jq, and σ is the rate of entropy production per unit volume. Consider now what happens after the occurrence of an earthquake at time t=0 and location (0,0,0). The earthquake introduces a stress drop Δ P(x,y,z) at all points of the system. Response flows are directed along the gradients toward the epicentral area, and the entropy production will increase with time as (Prigogine, 1947) σ x(t)=σ 0+α {1}/(t+β )+α {2}/(t+β )2+etc A seismological constraint on the parameters may be obtained from Omori's empirical relation N(t)=p/(t+q) where N(t) is the number of aftershocks at time t following the main shock. It may be assumed that p/q\\sim\\alpha_{1}/\\beta times a constant. Another useful constraint is the Mexican-hat geometry of the seismic transient as obtained e.g. from InSAR radar interferometry. For strike-slip events such as Landers the distribution of \\DeltaP is quadrantal, and an oval-shaped seismicity gap develops about the epicenter. A weak outer triggering maxiμm is found at a distance of about 17 fault lengths. Such patterns may be extracted from earthquake catalogs by statistical analysis (Lomnitz, 1996). Finally, the energy of the perturbation must be at least equal to the recovery energy. The total energy expended in an aftershock sequence can be found approximately by integrating the local contribution over

  7. Observation of the Effectiveness of Drama Method in Helping to Acquire the Addition-Subtraction Skills by Children at Preschool Phase

    ERIC Educational Resources Information Center

    Soydan, Sema; Quadir, Seher Ersoy

    2013-01-01

    Principal aim of this study is to show the effectiveness of the program prepared by researchers in order to enable 6 year-old children attending pre-school educational institutions to effectively gain addition subtraction skills through a drama-related method. The work group in the research comprised of 80 kids who continued their education in…

  8. Flux Transfer Events Simultaneously Observed by Polar and Cluster: Flux Rope in the Subsolar Region and Flux Tube Addition to the Polar Cusp

    NASA Technical Reports Server (NTRS)

    Le, G.; Zheng, Y.; Russell, C. T.; Pfaff, R. F.; Lin, N.; Slavin, J. A.; Parks, G.; Wilber, M.; Petrinec, S. M.; Lucek, E. A.; Reme, H.

    2007-01-01

    The phenomenon called flux transfer events (FTEs) is widely accepted as the manifestation of time-dependent reconnection. In this paper, we present observational evidence of a flux transfer event observed simultaneously at low-latitude by Polar and at high-latitude by Cluster. This event occurs on March 21, 2002, when both Cluster and Polar are located near local noon but with a large latitudinal separation. During the event, Cluster is moving outbound from the polar cusp to the magnetosheath, and Polar is in the magnetosheath near the equatorial magnetopause. The observations show that a flux transfer event occurs between the equator and the northern cusp. Polar and Cluster observe the FTE s two open flux tubes: Polar encounters the southward moving flux tube near the equator; and Cluster the northward moving flux tube at high latitude. The low latitude FTE appears to be a flux rope with helical magnetic field lines as it has a strong core field and the magnetic field component in the boundary normal direction exhibits a strong bi-polar variation. Unlike the low-latitude FTE, the high-latitude FTE observed by Cluster does not exhibit the characteristic bi-polar perturbation in the magnetic field. But the plasma data clearly reveal its open flux tube configuration. It shows that the magnetic field lines have straightened inside the FTE and become more aligned to the neighboring flux tubes as it moves to the cusp. Enhanced electrostatic fluctuations have been observed within the FTE core, both at low- and high-latitudes. This event provides a unique opportunity to understand high-latitude FTE signatures and the nature of time-varying reconnection.

  9. A Convenient Synthesis of γ–Amino-Ynamides via Additions of Lithiated Ynamides to Aryl Imines. Observation of an Aza-Meyer-Schuster Rearrangement.†

    PubMed Central

    Qi, Rui; Wang, Xiao-Na; Wang, Chao-Chao; Li, Qian; Li, Hui; Lv, Ming-Can; Yu, Qing

    2013-01-01

    Efforts in developing an expeditious and convenient method for synthesizing γ–amino-ynamides via nucleophilic addition of lithiated ynamides to aryl imines are described. This work also features an aza-variant of a Meyer-Schuster rearrangement of γ–amino-ynamides and the synthetic utility of γ–amino-ynamides in an intramolecular ketenimine-[2 + 2] cycloaddition. PMID:23976795

  10. Constraint Based Modeling Going Multicellular

    PubMed Central

    Martins Conde, Patricia do Rosario; Sauter, Thomas; Pfau, Thomas

    2016-01-01

    Constraint based modeling has seen applications in many microorganisms. For example, there are now established methods to determine potential genetic modifications and external interventions to increase the efficiency of microbial strains in chemical production pipelines. In addition, multiple models of multicellular organisms have been created including plants and humans. While initially the focus here was on modeling individual cell types of the multicellular organism, this focus recently started to switch. Models of microbial communities, as well as multi-tissue models of higher organisms have been constructed. These models thereby can include different parts of a plant, like root, stem, or different tissue types in the same organ. Such models can elucidate details of the interplay between symbiotic organisms, as well as the concerted efforts of multiple tissues and can be applied to analyse the effects of drugs or mutations on a more systemic level. In this review we give an overview of the recent development of multi-tissue models using constraint based techniques and the methods employed when investigating these models. We further highlight advances in combining constraint based models with dynamic and regulatory information and give an overview of these types of hybrid or multi-level approaches. PMID:26904548

  11. Constraints on primordial gravitational waves with variable sound speed from current CMB data

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Huang, Qing-Guo; Li, Xiao-Dong; Ma, Yin-Zhe

    2012-12-01

    We make a comprehensive investigation of the observational effect of the inflation consistency relation. We focus on the general single-field inflation model with the consistency relation r=-8csnt, and investigate the observational constraints of sound speed cs by using the seven-year WMAP data, the background imaging of cosmic extragalactic polarization tensor power spectrum data, and the constraints on non-Gaussian parameters fNLequil and fNLorth from the five-year WMAP observations. We find that the constraints on the tensor-to-scalar ratio r is much tighter if cs is small, since a large tilt nt is strongly constrained by the observations. We obtain r<0.37, 0.27, and 0.09 (dns/dln⁡k=0) for cs=1, 0.1, and 0.01 models at 95.4% confidence level (CL). When taking smaller values of cs, the positive correlation between r and ns also leads to a slightly tighter constraint on the upper bound of ns, while the running of scalar spectral index dns/dln⁡k is generally unaffected. For the sound speed cs, it is not well constrained if only the cosmic microwave background power spectrum data is used, while the constraints are obtainable by taking fNLequil and fNLorth priors into account. With the constraining data of fNLequil and fNLorth, we find that, cs≲0.01 region is excluded at 99.7% CL, and the cs=1 case (the single-field slow-roll inflation) is slightly disfavored at 68.3% CL. In addition, the inclusion of fNLequil. and fNLorth. into the analysis can improve the constraints on r and ns. We further discuss the implications of our constraints on the test of inflation models.

  12. A Two Magnetron Sputter Deposition Chamber Equipped with an Additional Ion Gun for in situ Observation of Thin Film Growth and Surface Modification by Synchrotron Radiation Scattering

    SciTech Connect

    Schell, Norbert; Borany, Johannes von; Hauser, Jens

    2007-01-19

    We report the design of a sputter deposition chamber for the in situ study of film growth and modification by synchrotron x-ray diffraction and reflectivity. The chamber is sealed with four Be-windows allowing unhindered scattering access of -2 up to +50 degrees off-plane and -2.9 up to +65 degrees in-plane, respectively. The chamber fits into a standard six-circle diffractometer from HUBER which is relatively widespread in synchrotron laboratories. Two commercial miniature magnetrons with additional gas inlets allow for the deposition of compound films and multilayers. Substrate heating up to 950 deg. C and different substrate bias voltages are possible. An additional ion gun up to 6 keV and 10 {mu}A allows post-deposition ion irradiation with light atoms or energetic ion bombardment during sputter deposition. The performance of the chamber was tested with the deposition of MAX phase Ti2AlN and with the off-sputtering of a thin Pt film.

  13. Food additives.

    PubMed

    Berglund, F

    1978-01-01

    The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI

  14. Effects of Rhenium Addition on the Temporal Evolution of the Nanostructure and Chemistry of a Model Ni-Cr-Al Superalloy. 1; Experimental Observations

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    The temporal evolution of the nanostructure and chemistry of a model Ni-8.5 at.% Cr-10 at. % Al alloy, with the addition of 2 at.% Re, aged at 1073 K from 0.25 to 264 h, was studied. Transmission electron microscopy and atom-probe tomography were used to measure the number density and mean radius of the gamma prime (L1(sub 2) structure)-precipitates and the chemistry of the gamma prime-precipitates and the gamma (face-centered cubic)-matrix, including the partitioning behavior of all alloying elements between the gamma- and gamma prime-phases and the segregation behavior at gamma/gamma prime interfaces. The precipitates remained spheroidal for an aging time of up to 264 h and, unlike commercial nickel-based superalloys containing Re, there was not confined (nonmonotonic) Re segregation at the gamma/gamma prime interfaces.

  15. Constraint-based Attribute and Interval Planning

    NASA Technical Reports Server (NTRS)

    Jonsson, Ari; Frank, Jeremy

    2013-01-01

    In this paper we describe Constraint-based Attribute and Interval Planning (CAIP), a paradigm for representing and reasoning about plans. The paradigm enables the description of planning domains with time, resources, concurrent activities, mutual exclusions among sets of activities, disjunctive preconditions and conditional effects. We provide a theoretical foundation for the paradigm, based on temporal intervals and attributes. We then show how the plans are naturally expressed by networks of constraints, and show that the process of planning maps directly to dynamic constraint reasoning. In addition, we de ne compatibilities, a compact mechanism for describing planning domains. We describe how this framework can incorporate the use of constraint reasoning technology to improve planning. Finally, we describe EUROPA, an implementation of the CAIP framework.

  16. Isocurvature constraints on portal couplings

    NASA Astrophysics Data System (ADS)

    Kainulainen, Kimmo; Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo; Vaskonen, Ville

    2016-06-01

    We consider portal models which are ultraweakly coupled with the Standard Model, and confront them with observational constraints on dark matter abundance and isocurvature perturbations. We assume the hidden sector to contain a real singlet scalar s and a sterile neutrino ψ coupled to s via a pseudoscalar Yukawa term. During inflation, a primordial condensate consisting of the singlet scalar s is generated, and its contribution to the isocurvature perturbations is imprinted onto the dark matter abundance. We compute the total dark matter abundance including the contributions from condensate decay and nonthermal production from the Standard Model sector. We then use the Planck limit on isocurvature perturbations to derive a novel constraint connecting dark matter mass and the singlet self coupling with the scale of inflation: mDM/GeV lesssim 0.2λs3/8 (H*/1011 GeV)‑3/2. This constraint is relevant in most portal models ultraweakly coupled with the Standard Model and containing light singlet scalar fields.

  17. Animal movement constraints improve resource selection inference in the presence of telemetry error.

    PubMed

    Brost, Brian M; Hooten, Mevin B; Hanks, Ephraim M; Small, Robert J

    2015-10-01

    Multiple factors complicate the analysis of animal telemetry location data. Recent advancements address issues such as temporal autocorrelation and telemetry measurement error, but additional challenges remain. Difficulties introduced by complicated error structures or barriers to animal movement can weaken inference. We propose an approach for obtaining resource selection inference from animal location data that accounts for complicated error structures, movement constraints, and temporally autocorrelated observations. We specify a model for telemetry data observed with error conditional on unobserved true locations that reflects prior knowledge about constraints in the animal movement process. The observed telemetry data are modeled using a flexible distribution that accommodates extreme errors and complicated error structures. Although constraints to movement are often viewed as a nuisance, we use constraints to simultaneously estimate and account for telemetry error. We apply the model to simulated data, showing that it outperforms common ad hoc approaches used when confronted with measurement error and movement constraints. We then apply our framework to an Argos satellite telemetry data set on harbor seals (Phoca vitulina) in the Gulf of Alaska, a species that is constrained to move within the marine environment and adjacent coastlines. PMID:26649380

  18. Animal movement constraints improve resource selection inference in the presence of telemetry error

    USGS Publications Warehouse

    Brost, Brian M.; Hooten, Mevin B.; Hanks, Ephraim M.; Small, Robert J.

    2016-01-01

    Multiple factors complicate the analysis of animal telemetry location data. Recent advancements address issues such as temporal autocorrelation and telemetry measurement error, but additional challenges remain. Difficulties introduced by complicated error structures or barriers to animal movement can weaken inference. We propose an approach for obtaining resource selection inference from animal location data that accounts for complicated error structures, movement constraints, and temporally autocorrelated observations. We specify a model for telemetry data observed with error conditional on unobserved true locations that reflects prior knowledge about constraints in the animal movement process. The observed telemetry data are modeled using a flexible distribution that accommodates extreme errors and complicated error structures. Although constraints to movement are often viewed as a nuisance, we use constraints to simultaneously estimate and account for telemetry error. We apply the model to simulated data, showing that it outperforms common ad hoc approaches used when confronted with measurement error and movement constraints. We then apply our framework to an Argos satellite telemetry data set on harbor seals (Phoca vitulina) in the Gulf of Alaska, a species that is constrained to move within the marine environment and adjacent coastlines.

  19. Neutron Star Observations and the Equation of State

    SciTech Connect

    Lattimer, James M.

    2009-05-07

    This talk reviews limits to the properties of neutron stars established from physical considerations such as causality and stability. In addition, it summarizes recent attempts to determine realistic bounds to the equation of state (EOS) from a simultaneous measurement of a neutron star's mass and radius. Observational constraints on the neutron star radius from thermal emission, seismology, spin-orbit coupling, and tidal effects in mergers are discussed. Possible constraints from neutron star cooling, including neutrino emissions, are discussed.

  20. Anaplastic Thyroid Cancer: The Addition of Systemic Chemotherapy to Radiotherapy Led to an Observed Improvement in Survival—A Single Centre Experience and Review of the Literature

    PubMed Central

    Lowe, Natalie M.; Loughran, Sean; Slevin, Nicholas J.; Yap, Beng K.

    2014-01-01

    Introduction. Anaplastic thyroid carcinoma (ATC) is rare yet accounts for up to 50% of all thyroid cancer deaths. This study reviews outcomes of patients with confirmed ATC referred to a tertiary oncology centre plus reviews the literature to explore how poor outcomes may be improved. Materials and Methods. The management and outcomes of 20 patients with ATC were reviewed. Results. Median age at diagnosis was 69.5 years. 19 patients died due to ATC, 40% of whom died from asphyxiation. Median survival for all cases was 59 days. Patients who had previous surgery prior to other treatment modalities had a longer median survival overall compared to those who had not had previous surgery (142 days compared to 59 days) and produced the one long-term survivor. Chemotherapy followed by radiotherapy (without previous surgery) was associated with longer median survival (220 days). Palliative radiotherapy alone did not decrease the rate of death by asphyxiation when compared to other single modality treatments. Conclusion. Multimodality treatment including surgery when feasible remains the best strategy to improve survival and prevent death from asphyxiation in the management of ATC. The addition of chemotherapy to our institutional protocol led to improved survival but prognosis remains very poor. PMID:25184150

  1. Reconnaissance observations of long-term natural vegetation recovery in the Cape Thompson region, Alaska, and additions to the checklist of flora

    SciTech Connect

    Everett, K.R.; Murray, B.M.; Murray, D.F.; Johnson, A.W.; Linkins, A.E.; Webber, P.J.

    1985-06-01

    The diversity of disturbance types, landforms, vegetation and soils, together with the large, well-documented flora, makes Cape Thompson an ideal site to study long-term (20-year) environmental adjustments after impact. Man-caused disturbances there between 1958 and 1962 fall into three categories: runways, excavations and off-road vehicle trails. In addition, natural disturbance by frost action creates scars. Reestablished vegetation after 20 years consisted of species found in adjacent undisturbed landscapes. Vegetation on excavations and cut-and-fill surfaces consisted of 3 to 5% vascular plants, of which Deschampsia cespitosa and Sagina nivalis are the most important (in terms of cover and frequency) of the 33 species identified. Cryptogams generally made up less than 1% of the vegetation, with lichens showing the least reestablishment. Vehicle trails crossing both alkaline and acidic fell-fields are still visible. Dryas octopetala, dominant in the adjacent undisturbed tundra, has not been effective in either recolonizing the track areas or extending into the trail from either the center or sides. The tundra at Ogotoruk Creek has shown considerable resiliency in terms of reestablishment of vegetation, especially in the moister sites where bank slumping and lateral migration of vegetation is effective. On the more-exposed, better-drained sites, as on frost scars, the continuing interplay between physical and biological forces has prevented directional or progressive plant succession. 33 figs., 13 tabs.

  2. Constraints in Genetic Programming

    NASA Technical Reports Server (NTRS)

    Janikow, Cezary Z.

    1996-01-01

    Genetic programming refers to a class of genetic algorithms utilizing generic representation in the form of program trees. For a particular application, one needs to provide the set of functions, whose compositions determine the space of program structures being evolved, and the set of terminals, which determine the space of specific instances of those programs. The algorithm searches the space for the best program for a given problem, applying evolutionary mechanisms borrowed from nature. Genetic algorithms have shown great capabilities in approximately solving optimization problems which could not be approximated or solved with other methods. Genetic programming extends their capabilities to deal with a broader variety of problems. However, it also extends the size of the search space, which often becomes too large to be effectively searched even by evolutionary methods. Therefore, our objective is to utilize problem constraints, if such can be identified, to restrict this space. In this publication, we propose a generic constraint specification language, powerful enough for a broad class of problem constraints. This language has two elements -- one reduces only the number of program instances, the other reduces both the space of program structures as well as their instances. With this language, we define the minimal set of complete constraints, and a set of operators guaranteeing offspring validity from valid parents. We also show that these operators are not less efficient than the standard genetic programming operators if one preprocesses the constraints - the necessary mechanisms are identified.

  3. Plant Functional Diversity Can Be Independent of Species Diversity: Observations Based on the Impact of 4-Yrs of Nitrogen and Phosphorus Additions in an Alpine Meadow

    PubMed Central

    Li, Wei; Cheng, Ji-Min; Yu, Kai-Liang; Epstein, Howard E.; Guo, Liang; Jing, Guang-Hua; Zhao, Jie; Du, Guo-Zhen

    2015-01-01

    Past studies have widely documented the decrease in species diversity in response to addition of nutrients, however functional diversity is often independent from species diversity. In this study, we conducted a field experiment to examine the effect of nitrogen and phosphorus fertilization ((NH4)2 HPO4) at 0, 15, 30 and 60 g m-2 yr-1 (F0, F15, F30 and F60) after 4 years of continuous fertilization on functional diversity and species diversity, and its relationship with productivity in an alpine meadow community on the Tibetan Plateau. To this purpose, three community-weighted mean trait values (specific leaf area, SLA; mature plant height, MPH; and seed size, SS) for 30 common species in each fertilization level were determined; three components of functional diversity (functional richness, FRic; functional evenness, FEve; and Rao’s index of quadratic entropy, FRao) were quantified. Our results showed that: (i) species diversity sharply decreased, but functional diversity remained stable with fertilization; (ii) community-weighted mean traits (SLA and MPH) had a significant increase along the fertilization level; (iii) aboveground biomass was not correlated with functional diversity, but it was significantly correlated with species diversity and MPH. Our results suggest that decreases in species diversity due to fertilization do not result in corresponding changes in functional diversity. Functional identity of species may be more important than functional diversity in influencing aboveground productivity in this alpine meadow community, and our results also support the mass ratio hypothesis; that is, the traits of the dominant species influenced the community biomass production. PMID:26295345

  4. Constraints complicate centrifugal compressor depressurization

    SciTech Connect

    Key, B. ); Colbert, F.L. )

    1993-05-10

    Blowdown of a centrifugal compressor is complicated by process constraints that might require slowing the depressurization rate and by mechanical constraints for which a faster rate might be preferred. The paper describes design constraints such as gas leaks; thrust-bearing overload; system constraints; flare extinguishing; heat levels; and pressure drop.

  5. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  6. Phosphazene additives

    SciTech Connect

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  7. QPO Constraints on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Miller, M. Coleman

    2005-01-01

    The kilohertz frequencies of QPOs from accreting neutron star systems imply that they are generated in regions of strong gravity, close to the star. This suggests that observations of the QPOs can be used to constrain the properties of neutron stars themselves, and in particular to inform us about the properties of cold matter beyond nuclear densities. Here we discuss some relatively model-insensitive constraints that emerge from the kilohertz QPOs, as well as recent developments that may hint at phenomena related to unstable circular orbits outside neutron stars.

  8. Trajectory constraints in qualitative simulation

    SciTech Connect

    Brajnik, G.; Clancy, D.J.

    1996-12-31

    We present a method for specifying temporal constraints on trajectories of dynamical systems and enforcing them during qualitative simulation. This capability can be used to focus a simulation, simulate non-autonomous and piecewise-continuous systems, reason about boundary condition problems and incorporate observations into the simulation. The method has been implemented in TeQSIM, a qualitative simulator that combines the expressive power of qualitative differential equations with temporal logic. It interleaves temporal logic model checking with the simulation to constrain and refine the resulting predicted behaviors and to inject discontinuous changes into the simulation.

  9. An Eight-Eyed Version of Hawkins and Shohet's Clinical Supervision Model: The Addition of the Cognitive Analytic Therapy Concept of the "Observing Eye/I" as the "Observing Us"

    ERIC Educational Resources Information Center

    Darongkamas, Jurai; John, Christopher; Walker, Mark James

    2014-01-01

    This paper proposes incorporating the concept of the "observing eye/I", from cognitive analytic therapy (CAT), to Hawkins and Shohet's seven modes of supervision, comprising their transtheoretical model of supervision. Each mode is described alongside explicit examples relating to CAT. This modification using a key idea from CAT (in…

  10. Reduction of Constraints: Applicability of the Homogeneity Constraint for Macrobatch 3

    SciTech Connect

    Peeler, D.K.

    2001-02-15

    The Product Composition Control System (PCCS) is used to determine the acceptability of each batch of Defense Waste Processing Facility (DWPF) melter feed in the Slurry Mix Evaporator (SME). This control system imposes several constraints on the composition of the contents of the SME to define acceptability. These constraints relate process or product properties to composition via prediction models. A SME batch is deemed acceptable if its sample composition measurements lead to acceptable property predictions after accounting for modeling, measurement and analytic uncertainties. The baseline document guiding the use of these data and models is ''SME Acceptability Determination for DWPF Process Control (U)'' by Brown and Postles [1996]. A minimum of three PCCS constraints support the prediction of the glass durability from a given SME batch. The Savannah River Technology Center (SRTC) is reviewing all of the PCCS constraints associated with durability. The purpose of this review is to revisit these constraints in light of the additional knowledge gained since the beginning of radioactive operations at DWPF and to identify any supplemental studies needed to amplify this knowledge so that redundant or overly conservative constraints can be eliminated or replaced by more appropriate constraints.

  11. Covariant constraints in ghost free massive gravity

    SciTech Connect

    Deffayet, C.; Mourad, J.; Zahariade, G. E-mail: mourad@apc.univ-paris7.fr

    2013-01-01

    We show that the reformulation of the de Rham-Gabadadze-Tolley massive gravity theory using vielbeins leads to a very simple and covariant way to count constraints, and hence degrees of freedom. Our method singles out a subset of theories, in the de Rham-Gabadadze-Tolley family, where an extra constraint, needed to eliminate the Boulware Deser ghost, is easily seen to appear. As a side result, we also introduce a new method, different from the Stuckelberg trick, to extract kinetic terms for the polarizations propagating in addition to those of the massless graviton.

  12. ECOLOGICAL AND EVOLUTIONARY CONSTRAINTS TO HERBIVORE RESISTANCE IN A NATIVE PLANT-MULTIPLE HERBIVORE COMMUNITY

    EPA Science Inventory

    This research project will reveal that novel constraints on resistance emerge with a consideration of more than one herbivore species. These constraints include genetic correlations in resistance to different herbivores, ecological interactions among the herbivores, non-addit...

  13. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1991-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint-based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all the inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocation for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its application to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  14. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1993-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint-based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all the inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocation for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its application to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  15. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1991-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocations for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its applications to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  16. A Constraint-based Attribute and Interval Planning

    NASA Technical Reports Server (NTRS)

    Frank, Jeremy; Jonsson, Ari; Clancy, Daniel (Technical Monitor)

    2001-01-01

    In this paper we introduce Constraint-based Attribute and Interval Planning (CAIP), a new paradigm for representing and reasoning about plans. The paradigm enables the description of planning domains with time, resources, concurrent activities, mutual exclusions among sets of activities, disjunctive preconditions and conditional effects. We provide a theoretical foundation for the paradigm using a mapping to first order logic. We also show that CAIP plans are naturally expressed by networks of constraints, and that planning maps directly to dynamic constraint reasoning. In addition, we show how constraint templates are used to provide a compact mechanism for describing planning domains.

  17. Structure Constraints in a Constraint-Based Planner

    NASA Technical Reports Server (NTRS)

    Pang, Wan-Lin; Golden, Keith

    2004-01-01

    In this paper we report our work on a new constraint domain, where variables can take structured values. Earth-science data processing (ESDP) is a planning domain that requires the ability to represent and reason about complex constraints over structured data, such as satellite images. This paper reports on a constraint-based planner for ESDP and similar domains. We discuss our approach for translating a planning problem into a constraint satisfaction problem (CSP) and for representing and reasoning about structured objects and constraints over structures.

  18. Compact location problems with budget and communication constraints

    SciTech Connect

    Krumke, S.O.; Noltemeier, H.; Ravi, S.S.; Marathe, M.V.

    1995-05-01

    We consider the problem of placing a specified number p of facilities on the nodes of a given network with two nonnegative edge-weight functions so as to minimize the diameter of the placement with respect to the first distance function under diameter or sum-constraints with respect to the second weight function. Define an ({alpha}, {beta})-approximation algorithm as a polynomial-time algorithm that produces a solution within a times the optimal function value, violating the constraint with respect to the second distance function by a factor of at most {beta}. We observe that in general obtaining an ({alpha}, {beta})-approximation for any fixed {alpha}, {beta} {ge} 1 is NP-hard for any of these problems. We present efficient approximation algorithms for the case, when both edge-weight functions obey the triangle inequality. For the problem of minimizing the diameter under a diameter Constraint with respect to the second weight-function, we provide a (2,2)-approximation algorithm. We. also show that no polynomial time algorithm can provide an ({alpha},2 {minus} {var_epsilon})- or (2 {minus} {var_epsilon},{beta})-approximation for any fixed {var_epsilon} > 0 and {alpha},{beta} {ge} 1, unless P = NP. This result is proved to remain true, even if one fixes {var_epsilon}{prime} > 0 and allows the algorithm to place only 2p/{vert_bar}VI{vert_bar}/{sup 6 {minus} {var_epsilon}{prime}} facilities. Our techniques can be extended to the case, when either the objective or the constraint is of sum-type and also to handle additional weights on the nodes of the graph.

  19. Cognitive constraints on motor imagery.

    PubMed

    Dahm, Stephan F; Rieger, Martina

    2016-03-01

    Executed bimanual movements are prepared slower when moving to symbolically different than when moving to symbolically same targets and when targets are mapped to target locations in a left/right fashion than when they are mapped in an inner/outer fashion [Weigelt et al. (Psychol Res 71:238-447, 2007)]. We investigated whether these cognitive bimanual coordination constraints are observable in motor imagery. Participants performed fast bimanual reaching movements from start to target buttons. Symbolic target similarity and mapping were manipulated. Participants performed four action conditions: one execution and three imagination conditions. In the latter they indicated starting, ending, or starting and ending of the movement. We measured movement preparation (RT), movement execution (MT) and the combined duration of movement preparation and execution (RTMT). In all action conditions RTs and MTs were longer in movements towards different targets than in movements towards same targets. Further, RTMTs were longer when targets were mapped to target locations in a left/right fashion than when they were mapped in an inner/outer fashion, again in all action conditions. RTMTs in imagination and execution were similar, apart from the imagination condition in which participants indicated the start and the end of the movement. Here MTs, but not RTs, were longer than in the execution condition. In conclusion, cognitive coordination constraints are present in the motor imagery of fast (<1600 ms) bimanual movements. Further, alternations between inhibition and execution may prolong the duration of motor imagery. PMID:25758054

  20. Hard and Soft Constraints in Reliability-Based Design Optimization

    NASA Technical Reports Server (NTRS)

    Crespo, L.uis G.; Giesy, Daniel P.; Kenny, Sean P.

    2006-01-01

    This paper proposes a framework for the analysis and design optimization of models subject to parametric uncertainty where design requirements in the form of inequality constraints are present. Emphasis is given to uncertainty models prescribed by norm bounded perturbations from a nominal parameter value and by sets of componentwise bounded uncertain variables. These models, which often arise in engineering problems, allow for a sharp mathematical manipulation. Constraints can be implemented in the hard sense, i.e., constraints must be satisfied for all parameter realizations in the uncertainty model, and in the soft sense, i.e., constraints can be violated by some realizations of the uncertain parameter. In regard to hard constraints, this methodology allows (i) to determine if a hard constraint can be satisfied for a given uncertainty model and constraint structure, (ii) to generate conclusive, formally verifiable reliability assessments that allow for unprejudiced comparisons of competing design alternatives and (iii) to identify the critical combination of uncertain parameters leading to constraint violations. In regard to soft constraints, the methodology allows the designer (i) to use probabilistic uncertainty models, (ii) to calculate upper bounds to the probability of constraint violation, and (iii) to efficiently estimate failure probabilities via a hybrid method. This method integrates the upper bounds, for which closed form expressions are derived, along with conditional sampling. In addition, an l(sub infinity) formulation for the efficient manipulation of hyper-rectangular sets is also proposed.

  1. Constraints on the tensor-to-scalar ratio for non-power-law models

    SciTech Connect

    Vázquez, J. Alberto; Bridges, M.; Ma, Yin-Zhe; Hobson, M.P. E-mail: mb435@mrao.cam.ac.uk E-mail: mph@mrao.cam.ac.uk

    2013-08-01

    Recent cosmological observations hint at a deviation from the simple power-law form of the primordial spectrum of curvature perturbations. In this paper we show that in the presence of a tensor component, a turn-over in the initial spectrum is preferred by current observations, and hence non-power-law models ought to be considered. For instance, for a power-law parameterisation with both a tensor component and running parameter, current data show a preference for a negative running at more than 2.5σ C.L. As a consequence of this deviation from a power-law, constraints on the tensor-to-scalar ratio r are slightly broader. We also present constraints on the inflationary parameters for a model-independent reconstruction and the Lasenby and Doran (LD) model. In particular, the constraints on the tensor-to-scalar ratio from the LD model are: r{sub LD} = 0.11±0.024. In addition to current data, we show expected constraints from Planck-like and CMB-Pol sensitivity experiments by using Markov-Chain-Monte-Carlo sampling chains. For all the models, we have included the Bayesian Evidence to perform a model selection analysis. The Bayes factor, using current observations, shows a strong preference for the LD model over the standard power-law parameterisation, and provides an insight into the accuracy of differentiating models through future surveys.

  2. Constraints on the tensor-to-scalar ratio for non-power-law models

    NASA Astrophysics Data System (ADS)

    Vázquez, J. Alberto; Bridges, M.; Ma, Yin-Zhe; Hobson, M. P.

    2013-08-01

    Recent cosmological observations hint at a deviation from the simple power-law form of the primordial spectrum of curvature perturbations. In this paper we show that in the presence of a tensor component, a turn-over in the initial spectrum is preferred by current observations, and hence non-power-law models ought to be considered. For instance, for a power-law parameterisation with both a tensor component and running parameter, current data show a preference for a negative running at more than 2.5σ C.L. As a consequence of this deviation from a power-law, constraints on the tensor-to-scalar ratio r are slightly broader. We also present constraints on the inflationary parameters for a model-independent reconstruction and the Lasenby & Doran (LD) model. In particular, the constraints on the tensor-to-scalar ratio from the LD model are: rLD = 0.11±0.024. In addition to current data, we show expected constraints from Planck-like and CMB-Pol sensitivity experiments by using Markov-Chain-Monte-Carlo sampling chains. For all the models, we have included the Bayesian Evidence to perform a model selection analysis. The Bayes factor, using current observations, shows a strong preference for the LD model over the standard power-law parameterisation, and provides an insight into the accuracy of differentiating models through future surveys.

  3. Nonparametric instrumental regression with non-convex constraints

    NASA Astrophysics Data System (ADS)

    Grasmair, M.; Scherzer, O.; Vanhems, A.

    2013-03-01

    This paper considers the nonparametric regression model with an additive error that is dependent on the explanatory variables. As is common in empirical studies in epidemiology and economics, it also supposes that valid instrumental variables are observed. A classical example in microeconomics considers the consumer demand function as a function of the price of goods and the income, both variables often considered as endogenous. In this framework, the economic theory also imposes shape restrictions on the demand function, such as integrability conditions. Motivated by this illustration in microeconomics, we study an estimator of a nonparametric constrained regression function using instrumental variables by means of Tikhonov regularization. We derive rates of convergence for the regularized model both in a deterministic and stochastic setting under the assumption that the true regression function satisfies a projected source condition including, because of the non-convexity of the imposed constraints, an additional smallness condition.

  4. Astrophysical Constraints of Dark Matter Properties

    NASA Astrophysics Data System (ADS)

    Moustakas, Leonidas A.; Abel, Tom; Brooks, Alyson; Buckley, Matthew; Bullock, James; Collins, Michelle; Cyr-Racine, Francis-Yan; Dawson, William; Drlica-Wagner, Alex; Gaskins, Jennifer; Kaplinghat, Manoj; Keeton, Charles R.; Kim, Stacy; Peter, Annika; Read, Justin; Simon, Joshua D.; Somerville, Rachel S.; Tollerud, Erik Jon; Treu, Tommaso; Wechsler, Risa H.

    2016-01-01

    The nature of the dark matter that fills the universe remains a profound puzzle in physics and astrophysics. Modern astronomical observations have the potential to produce constraints or measurements on properties of dark matter that may have real power for insights into its particle nature. The key lies with understanding what those constraints may be in a way that is interpretable for both the astronomical and particle physics communities, and establishing a community consensus of how diverse astronomical paths can use a common language. The AAS Special Session on the "Astrophysical constraints of dark matter properties" focuses on framing these questions with concrete proposals for astronomical dark matter metrics and potentially figures of merit, and through a series of presentations that serve as points of departure for discussion, ultimately to reach a community consensus that will be useful for current and future pursuits on this topic.

  5. Asteroseismic constraints for Gaia

    NASA Astrophysics Data System (ADS)

    Creevey, O. L.; Thévenin, F.

    2012-12-01

    Distances from the Gaia mission will no doubt improve our understanding of stellar physics by providing an excellent constraint on the luminosity of the star. However, it is also clear that high precision stellar properties from, for example, asteroseismology, will also provide a needed input constraint in order to calibrate the methods that Gaia will use, e.g. stellar models or GSP_Phot. For solar-like stars (F, G, K IV/V), asteroseismic data delivers at the least two very important quantities: (1) the average large frequency separation < Δ ν > and (2) the frequency corresponding to the maximum of the modulated-amplitude spectrum ν_{max}. Both of these quantities are related directly to stellar parameters (radius and mass) and in particular their combination (gravity and density). We show how the precision in < Δ ν >, ν_{max}, and atmospheric parameters T_{eff} and [Fe/H] affect the determination of gravity (log g) for a sample of well-known stars. We find that log g can be determined within less than 0.02 dex accuracy for our sample while considering precisions in the data expected for V˜12 stars from Kepler data. We also derive masses and radii which are accurate to within 1σ of the accepted values. This study validates the subsequent use of all of the available asteroseismic data on solar-like stars from the Kepler field (>500 IV/V stars) in order to provide a very important constraint for Gaia calibration of GSP_Phot} through the use of log g. We note that while we concentrate on IV/V stars, both the CoRoT and Kepler fields contain asteroseismic data on thousands of giant stars which will also provide useful calibration measures.

  6. Emergent Constraints for Cloud Feedbacks and Climate Sensitivity

    DOE PAGESBeta

    Klein, Stephen A.; Hall, Alex

    2015-10-26

    Emergent constraints are physically explainable empirical relationships between characteristics of the current climate and long-term climate prediction that emerge in collections of climate model simulations. With the prospect of constraining long-term climate prediction, scientists have recently uncovered several emergent constraints related to long-term cloud feedbacks. We review these proposed emergent constraints, many of which involve the behavior of low-level clouds, and discuss criteria to assess their credibility. With further research, some of the cases we review may eventually become confirmed emergent constraints, provided they are accompanied by credible physical explanations. Because confirmed emergent constraints identify a source of model errormore » that projects onto climate predictions, they deserve extra attention from those developing climate models and climate observations. While a systematic bias cannot be ruled out, it is noteworthy that the promising emergent constraints suggest larger cloud feedback and hence climate sensitivity.« less

  7. Emergent Constraints for Cloud Feedbacks and Climate Sensitivity

    SciTech Connect

    Klein, Stephen A.; Hall, Alex

    2015-10-26

    Emergent constraints are physically explainable empirical relationships between characteristics of the current climate and long-term climate prediction that emerge in collections of climate model simulations. With the prospect of constraining long-term climate prediction, scientists have recently uncovered several emergent constraints related to long-term cloud feedbacks. We review these proposed emergent constraints, many of which involve the behavior of low-level clouds, and discuss criteria to assess their credibility. With further research, some of the cases we review may eventually become confirmed emergent constraints, provided they are accompanied by credible physical explanations. Because confirmed emergent constraints identify a source of model error that projects onto climate predictions, they deserve extra attention from those developing climate models and climate observations. While a systematic bias cannot be ruled out, it is noteworthy that the promising emergent constraints suggest larger cloud feedback and hence climate sensitivity.

  8. Practical Cleanroom Operations Constraints

    NASA Technical Reports Server (NTRS)

    Hughes, David; Ginyard, Amani

    2007-01-01

    This viewgraph presentation reviews the GSFC Cleanroom Facility i.e., Spacecraft Systems Development and Integration Facility (SSDIF) with particular interest in its use during the development of the Wide Field Camera 3 (WFC3). The SSDIF is described and a diagram of the SSDIF is shown. A Constraint Table was created for consistency within Contamination Control Team. This table is shown. Another table that shows the activities that were allowed during the integration under given WFC3 condition and activity location is presented. Three decision trees are shown for different phases of the work: (1) Hardware Relocation, Hardware Work, and Contamination Control Operations.

  9. Global constraints on heavy neutrino mixing

    NASA Astrophysics Data System (ADS)

    Fernandez-Martinez, Enrique; Hernandez-Garcia, Josu; Lopez-Pavon, Jacobo

    2016-08-01

    We derive general constraints on the mixing of heavy Seesaw neutrinos with the SM fields from a global fit to present flavour and electroweak precision data. We explore and compare both a completely general scenario, where the heavy neutrinos are integrated out without any further assumption, and the more constrained case were only 3 additional heavy states are considered. The latter assumption implies non-trivial correlations in order to reproduce the correct neutrino masses and mixings as observed by oscillation data and thus some qualitative differences can be found with the more general scenario. The relevant processes analyzed in the global fit include searches for Lepton Flavour Violating (LFV) decays, probes of the universality of weak interactions, CKM unitarity bounds and electroweak precision data. In particular, a comparative and detailed study of the present and future sensitivity of the different LFV experiments is performed. We find a mild 1-2σ preference for non-zero heavy neutrino mixing of order 0.03-0.04 in the electron and tau sectors. At the 2σ level we derive bounds on all mixings ranging from 0.1 to 0.01 with the notable exception of the e - μ sector with a more stringent bound of 0.005 from the μ → eγ process.

  10. Induced seismicity constraints on subsurface geological structure, Paradox Valley, Colorado

    NASA Astrophysics Data System (ADS)

    Block, Lisa V.; Wood, Christopher K.; Yeck, William L.; King, Vanessa M.

    2015-02-01

    Precise relative hypocentres of seismic events induced by long-term fluid injection at the Paradox Valley Unit (PVU) brine disposal well provide constraints on the subsurface geological structure and compliment information available from deep seismic reflection and well data. We use the 3-D spatial distribution of the hypocentres to refine the locations, strikes, and throws of subsurface faults interpre­ted previously from geophysical surveys and to infer the existence of previously unidentified subsurface faults. From distinct epicentre lineations and focal mechanism trends, we identify a set of conjugate fracture orientations consistent with shear-slip reactivation of late-Palaeozoic fractures over a widespread area, as well as an additional fracture orientation present only near the injection well. We propose simple Mohr-Coulomb fracture models to explain these observations. The observation that induced seismicity preferentially occurs along one of the identified conjugate fracture orientations can be explained by a rotation in the direction of the regional maximum compressive stress from the time when the fractures were formed to the present. Shear slip along the third fracture orientation observed near the injection well is inconsistent with the current regional stress field and suggests a local rotation of the horizontal stresses. The detailed subsurface model produced by this analysis provides important insights for anticipating spatial patterns of future induced seismicity and for evaluation of possible additional injection well sites that are likely to be seismically and hydrologically isolated from the current well. In addition, the interpreted fault patterns provide constraints for estimating the maximum magnitude earthquake that may be induced, and for building geomechanical models to simulate pore pressure diffusion, stress changes and earthquake triggering.

  11. Higher derivative theories with constraints: exorcising Ostrogradski's ghost

    SciTech Connect

    Chen, Tai-jun; Lim, Eugene A.; Fasiello, Matteo; Tolley, Andrew J. E-mail: matte@case.edu E-mail: andrew.j.tolley@case.edu

    2013-02-01

    We prove that the linear instability in a non-degenerate higher derivative theory, the Ostrogradski instability, can only be removed by the addition of constraints if the original theory's phase space is reduced.

  12. Symbolic Constraint Maintenance Grid

    NASA Technical Reports Server (NTRS)

    James, Mark

    2006-01-01

    Version 3.1 of Symbolic Constraint Maintenance Grid (SCMG) is a software system that provides a general conceptual framework for utilizing pre-existing programming techniques to perform symbolic transformations of data. SCMG also provides a language (and an associated communication method and protocol) for representing constraints on the original non-symbolic data. SCMG provides a facility for exchanging information between numeric and symbolic components without knowing the details of the components themselves. In essence, it integrates symbolic software tools (for diagnosis, prognosis, and planning) with non-artificial-intelligence software. SCMG executes a process of symbolic summarization and monitoring of continuous time series data that are being abstractly represented as symbolic templates of information exchange. This summarization process enables such symbolic- reasoning computing systems as artificial- intelligence planning systems to evaluate the significance and effects of channels of data more efficiently than would otherwise be possible. As a result of the increased efficiency in representation, reasoning software can monitor more channels and is thus able to perform monitoring and control functions more effectively.

  13. Observation Scheduling System

    NASA Technical Reports Server (NTRS)

    Chien, Steve A.; Tran, Daniel Q.; Rabideau, Gregg R.; Schaffer, Steven R.

    2011-01-01

    Software has been designed to schedule remote sensing with the Earth Observing One spacecraft. The software attempts to satisfy as many observation requests as possible considering each against spacecraft operation constraints such as data volume, thermal, pointing maneuvers, and others. More complex constraints such as temperature are approximated to enable efficient reasoning while keeping the spacecraft within safe limits. Other constraints are checked using an external software library. For example, an attitude control library is used to determine the feasibility of maneuvering between pairs of observations. This innovation can deal with a wide range of spacecraft constraints and solve large scale scheduling problems like hundreds of observations and thousands of combinations of observation sequences.

  14. Relative constraints and evolution

    NASA Astrophysics Data System (ADS)

    Ochoa, Juan G. Diaz

    2014-03-01

    Several mathematical models of evolving systems assume that changes in the micro-states are constrained to the search of an optimal value in a local or global objective function. However, the concept of evolution requires a continuous change in the environment and species, making difficult the definition of absolute optimal values in objective functions. In this paper, we define constraints that are not absolute but relative to local micro-states, introducing a rupture in the invariance of the phase space of the system. This conceptual basis is useful to define alternative mathematical models for biological (or in general complex) evolving systems. We illustrate this concept with a modified Ising model, which can be useful to understand and model problems like the somatic evolution of cancer.

  15. Nontrivial Ghosts and Second-Class Constraints

    NASA Astrophysics Data System (ADS)

    Chishtie, Farrukh; McKeon, D. G. C.

    In a model in which a vector gauge field Wμ a is coupled to an antisymmetric tensor field φ μ ν a possessing a pseudoscalar mass, it has been shown that all physical degrees of freedom reside in the vector field. Upon quantizing this model using the Faddeev-Popov procedure, explicit calculation of the two-point functions <ϕϕ> and at one-loop order seems to have yielded the puzzling result that the effective action generated by radiative effects has more physical degrees of freedom than the original classical action. In this paper we point out that this is not in fact a real effect, but rather appears to be a consequence of having ignored a "ghost" field arising from the contribution to the measure in the path integral arising from the presence of nontrivial second-class constraints. These ghost fields couple to the fields Wμ a and φ μ ν a, which makes them distinct from other models involving ghosts arising from second-class constraints (such as massive Yang-Mills (YM) models) that have been considered, as in these other models such ghosts decouple. As an alternative to dealing with second-class constraints, we consider introducing a "Stueckelberg field" to eliminate second-class constraints in favor of first-class constraints and examine if it is possible to then use the Faddeev-Popov quantization procedure. In the Proca model, introduction of the Stueckelberg vector is equivalent to the Batalin-Fradkin-Tyutin (BFT) approach to converting second-class constraints to being first-class through the introduction of new variables. However, introduction of a Stueckelberg vector is not equivalent to the BFT approach for the vector-tensor model. In an appendix, the BFT procedure is applied to the pure tensor model and a novel gauge invariance is found. In addition, we also consider extending the Hamiltonian so that half of the second-class constraints become first-class and the other half become associated gauge conditions. We also find for this tensor

  16. Planck 2015 constraints on reionization history

    NASA Astrophysics Data System (ADS)

    Tristram, Matthieu

    2015-08-01

    On behalf of the Planck collaboration, we will show the tightest constraints on cosmic reionization extracted from the CMB polarization at low multipole by Planck.The CMB large scales polarization data can gives strong constraints on the reionization history through the measurement of the reionization optical depth. The Thomson optical depth measured is significantly smaller than previously estimated from CMB polarization data. This result reduces the tension between CMB based analyses and constraints from other astrophysical sources. It highlights the necessity of a deep revision of our view on the history of reionization and the dark age. We also combine constraints from low and high l, in particular from the amplitude of the kinetic Sunyaev Zeld’ovitch effect (kSZ), to derive the time and duration of the reionization epoch. In addition, using both a new two-stage parametrization of the ionization fraction, closer to recent self-regulated simulations, and a non parametric reconstruction, we estimate a more realistic beginning, end, and duration of Reionization.

  17. Redshift drift constraints on f( T) gravity

    NASA Astrophysics Data System (ADS)

    Geng, Jia-Jia; Guo, Rui-Yun; He, Dong-Ze; Zhang, Jing-Fei; Zhang, Xin

    2015-10-01

    We explore the impact of the Sandage-Loeb (SL) test on the precision of cosmological constraints for f( T) gravity theories. The SL test is an important supplement to current cosmological observations because it measures the redshift drift in the Lyman-α forest in the spectra of distant quasars, covering the "redshift desert" of 2 ≤ z ≤ 5. To avoid data inconsistency, we use the best-fit models based on current combined observational data as fiducial models to simulate 30 mock SL test data. We quantify the impact of these SL test data on parameter estimation for f( T) gravity theories. Two typical f( T) models are considered, the power-law model f( T) PL and the exponential-form model f( T) EXP . The results show that the SL test can effectively break the existing strong degeneracy between the present-day matter density Ω m and the Hubble constant H 0 in other cosmological observations. For the considered f( T) models, a 30-year observation of the SL test can improve the constraint precision of Ω m and H 0 enormously but cannot effectively improve the constraint precision of the model parameters.

  18. Statistical and constraint factors in cleavage initiation

    SciTech Connect

    Odette, G.R.; Edsinger, K.V.; Lucas, G.E.

    1997-12-31

    The size dependence of effective cleavage initiation toughness K{sub e}(T) (defined by the load-displacement conditions at initiation) of steels are mediated by both statistical and constraint factors. Statistical effects are controlled by the total high stress volume even under plane strain, small scale yielding, e.g., K{sub Ic} {proportional_to} 1/B{sup {minus}1/4}. Constraint loss and reductions in the stress fields occurs for shallow cracks, large scale yielding and deviations from plane strain. The interplay between these factors is examined by analyzing the observed K{sub e}(T) behavior for specimens with different W, B and a/W using FEM simulations of the crack tip fields and confocal microscopy, fracture reconstruction and SEM characterization of the sequence-of-fracture-events. Observed versus actual sequences and complications such as crack tip strain, the transition to ductile tearing and ultimate loss of specimen capacity are discussed.

  19. Credit Constraints for Higher Education

    ERIC Educational Resources Information Center

    Solis, Alex

    2012-01-01

    This paper exploits a natural experiment that produces exogenous variation on credit access to determine the effect on college enrollment. The paper assess how important are credit constraints to explain the gap in college enrollment by family income, and what would be the gap if credit constraints are eliminated. Progress in college and dropout…

  20. On Constraints in Assembly Planning

    SciTech Connect

    Calton, T.L.; Jones, R.E.; Wilson, R.H.

    1998-12-17

    Constraints on assembly plans vary depending on product, assembly facility, assembly volume, and many other factors. Assembly costs and other measures to optimize vary just as widely. To be effective, computer-aided assembly planning systems must allow users to express the plan selection criteria that appIy to their products and production environments. We begin this article by surveying the types of user criteria, both constraints and quality measures, that have been accepted by assembly planning systems to date. The survey is organized along several dimensions, including strategic vs. tactical criteria; manufacturing requirements VS. requirements of the automated planning process itself and the information needed to assess compliance with each criterion. The latter strongly influences the efficiency of planning. We then focus on constraints. We describe a framework to support a wide variety of user constraints for intuitive and efficient assembly planning. Our framework expresses all constraints on a sequencing level, specifying orders and conditions on part mating operations in a number of ways. Constraints are implemented as simple procedures that either accept or reject assembly operations proposed by the planner. For efficiency, some constraints are supplemented with special-purpose modifications to the planner's algorithms. Fast replanning enables an interactive plan-view-constrain-replan cycle that aids in constraint discovery and documentation. We describe an implementation of the framework in a computer-aided assembly planning system and experiments applying the system to a number of complex assemblies, including one with 472 parts.

  1. Fixed Costs and Hours Constraints

    ERIC Educational Resources Information Center

    Johnson, William R.

    2011-01-01

    Hours constraints are typically identified by worker responses to questions asking whether they would prefer a job with more hours and more pay or fewer hours and less pay. Because jobs with different hours but the same rate of pay may be infeasible when there are fixed costs of employment or mandatory overtime premia, the constraint in those…

  2. Varying alpha: New constraints from seasonal variations

    SciTech Connect

    Barrow, John D.; Shaw, Douglas J.

    2008-09-15

    We analyze the constraints obtained from new atomic clock data on the possible time variation of the fine structure 'constant' and the electron-proton mass ratio, and show how they are strengthened when the seasonal variation of the Sun's gravitational field at the Earth's surface is taken into account. We compare these bounds with those obtainable from tests of the weak equivalence principle and high redshift observations of quasar absorption spectra.

  3. JIMWLK and beyond: From concepts to observables

    NASA Astrophysics Data System (ADS)

    Weigert, Heribert; Lappi, Tuomas; Ramnath, Andrecia; Rummukainen, Kari

    2016-03-01

    The Color Glass Condensate and its associated evolution equation, the JIMWLK equation have applications to many observables far beyond totally inclusive observables. The phenomenology is so rich that little has been done to explore beyond scaling behavior of correlators. We show first examples that exemplify the considerations necessary to access additional information both experimentally and theoretically and demonstrate that the Wilson line correlators appearing throughout make it imperative to consistently take into account that one is dealing with correlators of group elements and demonstrate how this imposes physical and phenomenological constraints. Similar considerations apply also to jet observables at finite Nc.

  4. Optimizing selection with several constraints in poultry breeding.

    PubMed

    Chapuis, H; Pincent, C; Colleau, J J

    2016-02-01

    Poultry breeding schemes permanently face the need to control the evolution of coancestry and some critical traits, while selecting for a main breeding objective. The main aims of this article are first to present an efficient selection algorithm adapted to this situation and then to measure how the severity of constraints impacted on the degree of loss for the main trait, compared to BLUP selection on the main trait, without any constraint. Broiler dam and sire line schemes were mimicked by simulation over 10 generations and selection was carried out on the main trait under constraints for coancestry and for another trait, antagonistic with the main trait. The selection algorithm was a special simulated annealing (adaptative simulated annealing (ASA)). It was found to be rapid and able to meet constraints very accurately. A constraint on the second trait was found to induce an impact similar to or even greater than the impact of the constraint on coancestry. The family structure of selected poultry populations made it easy to control the evolution of coancestry at a reasonable cost but was not as useful for reducing the cost of controlling evolution of the antagonistic traits. Multiple constraints impacted almost additively on the genetic gain for the main trait. Adding constraints for several traits would therefore be justified in real life breeding schemes, possibly after evaluating their impact through simulated annealing. PMID:26220593

  5. A Critical Reevaluation of Radio Constraints on Annihilating Dark Matter

    SciTech Connect

    Cholis, Ilias; Hooper, Dan; Linden, Tim

    2015-04-03

    A number of groups have employed radio observations of the Galactic center to derive stringent constraints on the annihilation cross section of weakly interacting dark matter. In this paper, we show that electron energy losses in this region are likely to be dominated by inverse Compton scattering on the interstellar radiation field, rather than by synchrotron, considerably relaxing the constraints on the dark matter annihilation cross section compared to previous works. Strong convective winds, which are well motivated by recent observations, may also significantly weaken synchrotron constraints. After taking these factors into account, we find that radio constraints on annihilating dark matter are orders of magnitude less stringent than previously reported, and are generally weaker than those derived from current gamma-ray observations.

  6. Further Constraints on Electron Acceleration in Solar Noise Storms

    NASA Astrophysics Data System (ADS)

    Subramanian, Prasad; Becker, Peter A.

    2006-08-01

    We reexamine the energetics of nonthermal-electron acceleration in solar noise storms. A new result is obtained for the minimum nonthermal-electron number density required to produce a Langmuir-wave population of sufficient intensity to power the noise-storm emission. We combine this constraint with the stochastic electron acceleration formalism developed by Subramanian and Becker (2005) to derive a rigorous estimate for the efficiency of the overall noise-storm emission process, beginning with nonthermal-electron acceleration and culminating in the observed radiation. We also calculate separate efficiencies for the electron acceleration Langmuir wave generation stage and the Langmuir wave noise-storm production stage. In addition, we obtain a new theoretical estimate for the energy density of the Langmuir waves in noise-storm continuum sources.

  7. QCD constraints on the equation of state for compact stars

    NASA Astrophysics Data System (ADS)

    Fraga, E. S.; Kurkela, A.; Schaffner-Bielich, J.; Vuorinen, A.

    2016-01-01

    In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount - or even presence - of quark matter inside the stars. In this framework, we also present a simple effective equation of state for cold quark matter that consistently incorporates the effects of interactions and furthermore includes a built-in estimate of the inherent systematic uncertainties. This goes beyond the MIT bag model description in a crucial way, yet leads to an equation of state that is equally straightforward to use.

  8. Transverse gravity versus observations

    SciTech Connect

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J.J. E-mail: anton.fernandez@uam.es

    2009-07-01

    Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂{sub μ}ξ{sup μ} = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

  9. Transverse gravity versus observations

    NASA Astrophysics Data System (ADS)

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J. J.

    2009-07-01

    Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂μξμ = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

  10. Constraints and stability in vector theories with spontaneous Lorentz violation

    SciTech Connect

    Bluhm, Robert; Gagne, Nolan L.; Potting, Robertus; Vrublevskis, Arturs

    2008-06-15

    Vector theories with spontaneous Lorentz violation, known as bumblebee models, are examined in flat spacetime using a Hamiltonian constraint analysis. In some of these models, Nambu-Goldstone modes appear with properties similar to photons in electromagnetism. However, depending on the form of the theory, additional modes and constraints can appear that have no counterparts in electromagnetism. An examination of these constraints and additional degrees of freedom, including their nonlinear effects, is made for a variety of models with different kinetic and potential terms, and the results are compared with electromagnetism. The Hamiltonian constraint analysis also permits an investigation of the stability of these models. For certain bumblebee theories with a timelike vector, suitable restrictions of the initial-value solutions are identified that yield ghost-free models with a positive Hamiltonian. In each case, the restricted phase space is found to match that of electromagnetism in a nonlinear gauge.

  11. Probabilistic Constraint Logic Programming. Formal Foundations of Quantitative and Statistical Inference in Constraint-Based Natural Language Processing

    NASA Astrophysics Data System (ADS)

    Riezler, Stefan

    2000-08-01

    In this thesis, we present two approaches to a rigorous mathematical and algorithmic foundation of quantitative and statistical inference in constraint-based natural language processing. The first approach, called quantitative constraint logic programming, is conceptualized in a clear logical framework, and presents a sound and complete system of quantitative inference for definite clauses annotated with subjective weights. This approach combines a rigorous formal semantics for quantitative inference based on subjective weights with efficient weight-based pruning for constraint-based systems. The second approach, called probabilistic constraint logic programming, introduces a log-linear probability distribution on the proof trees of a constraint logic program and an algorithm for statistical inference of the parameters and properties of such probability models from incomplete, i.e., unparsed data. The possibility of defining arbitrary properties of proof trees as properties of the log-linear probability model and efficiently estimating appropriate parameter values for them permits the probabilistic modeling of arbitrary context-dependencies in constraint logic programs. The usefulness of these ideas is evaluated empirically in a small-scale experiment on finding the correct parses of a constraint-based grammar. In addition, we address the problem of computational intractability of the calculation of expectations in the inference task and present various techniques to approximately solve this task. Moreover, we present an approximate heuristic technique for searching for the most probable analysis in probabilistic constraint logic programs.

  12. A constraint-based search algorithm for parameter identification of environmental models

    NASA Astrophysics Data System (ADS)

    Gharari, S.; Shafiei, M.; Hrachowitz, M.; Kumar, R.; Fenicia, F.; Gupta, H. V.; Savenije, H. H. G.

    2014-12-01

    Many environmental systems models, such as conceptual rainfall-runoff models, rely on model calibration for parameter identification. For this, an observed output time series (such as runoff) is needed, but frequently not available (e.g., when making predictions in ungauged basins). In this study, we provide an alternative approach for parameter identification using constraints based on two types of restrictions derived from prior (or expert) knowledge. The first, called parameter constraints, restricts the solution space based on realistic relationships that must hold between the different model parameters while the second, called process constraints requires that additional realism relationships between the fluxes and state variables must be satisfied. Specifically, we propose a search algorithm for finding parameter sets that simultaneously satisfy such constraints, based on stepwise sampling of the parameter space. Such parameter sets have the desirable property of being consistent with the modeler's intuition of how the catchment functions, and can (if necessary) serve as prior information for further investigations by reducing the prior uncertainties associated with both calibration and prediction.

  13. Evolutionary constraints or opportunities?

    PubMed Central

    Sharov, Alexei A.

    2014-01-01

    Natural selection is traditionally viewed as a leading factor of evolution, whereas variation is assumed to be random and non-directional. Any order in variation is attributed to epigenetic or developmental constraints that can hinder the action of natural selection. In contrast I consider the positive role of epigenetic mechanisms in evolution because they provide organisms with opportunities for rapid adaptive change. Because the term “constraint” has negative connotations, I use the term “regulated variation” to emphasize the adaptive nature of phenotypic variation, which helps populations and species to survive and evolve in changing environments. The capacity to produce regulated variation is a phenotypic property, which is not described in the genome. Instead, the genome acts as a switchboard, where mostly random mutations switch “on” or “off” preexisting functional capacities of organism components. Thus, there are two channels of heredity: informational (genomic) and structure-functional (phenotypic). Functional capacities of organisms most likely emerged in a chain of modifications and combinations of more simple ancestral functions. The role of DNA has been to keep records of these changes (without describing the result) so that they can be reproduced in the following generations. Evolutionary opportunities include adjustments of individual functions, multitasking, connection between various components of an organism, and interaction between organisms. The adaptive nature of regulated variation can be explained by the differential success of lineages in macro-evolution. Lineages with more advantageous patterns of regulated variation are likely to produce more species and secure more resources (i.e., long-term lineage selection). PMID:24769155

  14. Infrared Kuiper Belt Constraints

    SciTech Connect

    Teplitz, V.L.; Stern, S.A.; Anderson, J.D.; Rosenbaum, D.; Scalise, R.J.; Wentzler, P.

    1999-05-01

    We compute the temperature and IR signal of particles of radius {ital a} and albedo {alpha} at heliocentric distance {ital R}, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of {ital COBE} DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance {ital R}, particle radius {ital a}, and particle albedo {alpha}. We then apply these results to a recently developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40{lt}R{lt}50{endash}90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the solar system of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally, we compare Kuiper belt IR spectra for various parameter values. Results of this work include: (1) numerical limits on Kuiper belt dust as a function of ({ital R}, {ital a}, {alpha}) on the basis of four alternative sets of constraints, including those following from recent discovery of the cosmic IR background by Hauser et al.; (2) application to the two-sector Kuiper belt model, finding mass limits and spectrum shape for different values of relevant parameters including dependence on time elapsed since last passage through a molecular cloud cleared the outer solar system of dust; and (3) potential use of spectral information to determine time since last passage of the Sun through a giant molecular cloud. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  15. Compilation of non-contemporaneous constraints

    SciTech Connect

    Wray, R.E. III; Laird, J.E.; Jones, R.M.

    1996-12-31

    Hierarchical execution of domain knowledge is a useful approach for intelligent, real-time systems in complex domains. In addition, well-known techniques for knowledge compilation allow the reorganization of knowledge hierarchies into more efficient forms. However, these techniques have been developed in the context of systems that work in static domains. Our investigations indicate that it is not straightforward to apply knowledge compilation methods for hierarchical knowledge to systems that generate behavior in dynamic environments. One particular problem involves the compilation of non-contemporaneous constraints. This problem arises when a training instance dynamically changes during execution. After defining the problem, we analyze several theoretical approaches that address non-contemporaneous constraints. We have implemented the most promising of these alternatives within Soar, a software architecture for performance and learning. Our results demonstrate that the proposed solutions eliminate the problem in some situations and suggest that knowledge compilation methods are appropriate for interactive environments.

  16. Constraints on muon-specific dark forces

    NASA Astrophysics Data System (ADS)

    Karshenboim, Savely G.; McKeen, David; Pospelov, Maxim

    2014-10-01

    The recent measurement of the Lamb shift in muonic hydrogen allows for the most precise extraction of the charge radius of the proton which is currently in conflict with other determinations based on e-p scattering and hydrogen spectroscopy. This discrepancy could be the result of some new muon-specific force with O(1-100) MeV force carrier—in this paper we concentrate on vector mediators. Such an explanation faces challenges from the constraints imposed by the g-2 of the muon and electron as well as precision spectroscopy of muonic atoms. In this work we complement the family of constraints by calculating the contribution of hypothetical forces to the muonium hyperfine structure. We also compute the two-loop contribution to the electron parity-violating amplitude due to a muon loop, which is sensitive to the muon axial-vector coupling. Overall, we find that the combination of low-energy constraints favors the mass of the mediator to be below 10 MeV and that a certain degree of tuning is required between vector and axial-vector couplings of new vector particles to muons in order to satisfy constraints from muon g-2. However, we also observe that in the absence of a consistent standard model embedding high-energy weak-charged processes accompanied by the emission of new vector particles are strongly enhanced by (E/mV)2, with E a characteristic energy scale and mV the mass of the mediator. In particular, leptonic W decays impose the strongest constraints on such models completely disfavoring the remainder of the parameter space.

  17. A Hybrid Constraint Representation and Reasoning Framework

    NASA Technical Reports Server (NTRS)

    Golden, Keith; Pang, Wan-Lin

    2003-01-01

    This paper introduces JNET, a novel constraint representation and reasoning framework that supports procedural constraints and constraint attachments, providing a flexible way of integrating the constraint reasoner with a run- time software environment. Attachments in JNET are constraints over arbitrary Java objects, which are defined using Java code, at runtime, with no changes to the JNET source code.

  18. Effects of Ag addition on FePt L1{sub 0} ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

    SciTech Connect

    Wang, Lei; Yu, Youxing; Gao, Tenghua

    2015-12-21

    FePt and (FePt){sub 91.2}Ag{sub 8.8} alloy films were deposited by magnetron sputtering. The average coercivity of (FePt){sub 91.2}Ag{sub 8.8} films reaches 8.51 × 10{sup 5} A/m, which is 0.63 × 10{sup 5} A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L1{sub 0} ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution reveals more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L1{sub 0} ordering transition.

  19. Direct observation of an anisotropic in-plane residual stress induced by B addition as an origin of high magnetic anisotropy field of Ru/FeCoB film

    NASA Astrophysics Data System (ADS)

    Hirata, Ken-ichiro; Gomi, Shunsuke; Mashiko, Yasuhiro; Nakagawa, Shigeki

    2010-05-01

    Although boron-free FeCo films prepared on a Ru underlayer exhibits isotropic in-plane magnetic property, boron added FeCoB films prepared on Ru underlayer revealed large in-plane magnetic anisotropy with a high anisotropy field of 500 Oe. The effect of boron addition on the in-plane anisotropic residual stress in FeCoB film was investigated using sin2 ψ method of x-ray diffraction analysis. Large isotropic compressive stress was