Optimization of a Focusable and Rotatable Shear-Wave Periodic Permanent Magnet Electromagnetic Acoustic Transducers for Plates Inspection.

PubMed

Song, Xiaochun; Qiu, Gongzhe

2017-11-24

Due to the symmetry of conventional periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs), two shear (SH) waves can be generated and propagated simultaneously in opposite directions, which makes the signal recognition and interpretation complicatedly. Thus, this work presents a new SH wave PPM EMAT design, rotating the parallel line sources to realize the wave beam focusing in a single-direction. The theoretical model of distributed line sources was deduced firstly, and the effects of some parameters, such as the inner coil width, adjacent line sources spacing and the angle between parallel line sources, on SH wave focusing and directivity were studied mainly with the help of 3D FEM. Employing the proposed PPM EMATs, some experiments are carried out to verify the reliability of FEM simulation. The results indicate that rotating the parallel line sources can strength the wave on the closing side of line sources, decreasing the inner coil width and the adjacent line sources spacing can improve the amplitude and directivity of signals excited by transducers. Compared with traditional PPM EMATs, both the capacity of unidirectional excitation and directivity of the proposed PPM EMATs are improved significantly.

A line-source method for aligning on-board and other pinhole SPECT systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-12-15

Purpose: In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system—to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)—is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems.Methods: An alignment model consisting of multiple alignmentmore » parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot.Results: In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist.Conclusions: Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC.« less

A line-source method for aligning on-board and other pinhole SPECT systems

PubMed Central

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-01-01

Purpose: In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system—to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)—is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems. Methods: An alignment model consisting of multiple alignment parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot. Results: In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist. Conclusions: Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC. PMID:24320537

A line-source method for aligning on-board and other pinhole SPECT systems.

PubMed

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-12-01

In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system-to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)-is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems. An alignment model consisting of multiple alignment parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot. In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist. Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC.

Dual-Source Linear Energy Prediction (LINE-P) Model in the Context of WSNs.

PubMed

Ahmed, Faisal; Tamberg, Gert; Le Moullec, Yannick; Annus, Paul

2017-07-20

Energy harvesting technologies such as miniature power solar panels and micro wind turbines are increasingly used to help power wireless sensor network nodes. However, a major drawback of energy harvesting is its varying and intermittent characteristic, which can negatively affect the quality of service. This calls for careful design and operation of the nodes, possibly by means of, e.g., dynamic duty cycling and/or dynamic frequency and voltage scaling. In this context, various energy prediction models have been proposed in the literature; however, they are typically compute-intensive or only suitable for a single type of energy source. In this paper, we propose Linear Energy Prediction "LINE-P", a lightweight, yet relatively accurate model based on approximation and sampling theory; LINE-P is suitable for dual-source energy harvesting. Simulations and comparisons against existing similar models have been conducted with low and medium resolutions (i.e., 60 and 22 min intervals/24 h) for the solar energy source (low variations) and with high resolutions (15 min intervals/24 h) for the wind energy source. The results show that the accuracy of the solar-based and wind-based predictions is up to approximately 98% and 96%, respectively, while requiring a lower complexity and memory than the other models. For the cases where LINE-P's accuracy is lower than that of other approaches, it still has the advantage of lower computing requirements, making it more suitable for embedded implementation, e.g., in wireless sensor network coordinator nodes or gateways.

Line-source simulation for shallow-seismic data. Part 2: full-waveform inversion—a synthetic 2-D case study

NASA Astrophysics Data System (ADS)

Schäfer, M.; Groos, L.; Forbriger, T.; Bohlen, T.

2014-09-01

Full-waveform inversion (FWI) of shallow-seismic surface waves is able to reconstruct lateral variations of subsurface elastic properties. Line-source simulation for point-source data is required when applying algorithms of 2-D adjoint FWI to recorded shallow-seismic field data. The equivalent line-source response for point-source data can be obtained by convolving the waveforms with √{t^{-1}} (t: traveltime), which produces a phase shift of π/4. Subsequently an amplitude correction must be applied. In this work we recommend to scale the seismograms with √{2 r v_ph} at small receiver offsets r, where vph is the phase velocity, and gradually shift to applying a √{t^{-1}} time-domain taper and scaling the waveforms with r√{2} for larger receiver offsets r. We call this the hybrid transformation which is adapted for direct body and Rayleigh waves and demonstrate its outstanding performance on a 2-D heterogeneous structure. The fit of the phases as well as the amplitudes for all shot locations and components (vertical and radial) is excellent with respect to the reference line-source data. An approach for 1-D media based on Fourier-Bessel integral transformation generates strong artefacts for waves produced by 2-D structures. The theoretical background for both approaches is presented in a companion contribution. In the current contribution we study their performance when applied to waves propagating in a significantly 2-D-heterogeneous structure. We calculate synthetic seismograms for 2-D structure for line sources as well as point sources. Line-source simulations obtained from the point-source seismograms through different approaches are then compared to the corresponding line-source reference waveforms. Although being derived by approximation the hybrid transformation performs excellently except for explicitly back-scattered waves. In reconstruction tests we further invert point-source synthetic seismograms by a 2-D FWI to subsurface structure and evaluate its ability to reproduce the original structural model in comparison to the inversion of line-source synthetic data. Even when applying no explicit correction to the point-source waveforms prior to inversion only moderate artefacts appear in the results. However, the overall performance is best in terms of model reproduction and ability to reproduce the original data in a 3-D simulation if inverted waveforms are obtained by the hybrid transformation.

Apportionment of urban aerosol sources in Chongqing (China) using synergistic on-line techniques

NASA Astrophysics Data System (ADS)

Chen, Yang; Yang, Fumo

2016-04-01

The sources of ambient fine particulate matter (PM2.5) during wintertime at a background urban location in Chongqing (southwestern China) have been determined. Aerosol chemical composition analyses were performed using multiple on-line techniques, such as single particle aerosol mass spectrometer (SPAMS) for single particle chemical composition, on-line elemental carbon-organic carbon analyzer (on-line OC-EC), on-line X-ray fluorescence (XRF) for elements, and in-situ Gas and Aerosol Compositions monitor (IGAC) for water-soluble ions in PM2.5. All the datasets from these techniques have been adjusted to a 1-h time resolution for receptor model input. Positive matrix factorization (PMF) has been used for resolving aerosol sources. At least six sources, including domestic coal burning, biomass burning, dust, traffic, industrial and secondary/aged factors have been resolved and interpreted. The synergistic on-line techniques were helpful for identifying aerosol sources more clearly than when only employing the results from the individual techniques. This results are useful for better understanding of aerosol sources and atmospheric processes.

Scattering in infrared radiative transfer: A comparison between the spectrally averaging model JURASSIC and the line-by-line model KOPRA

NASA Astrophysics Data System (ADS)

Griessbach, Sabine; Hoffmann, Lars; Höpfner, Michael; Riese, Martin; Spang, Reinhold

2013-09-01

The viability of a spectrally averaging model to perform radiative transfer calculations in the infrared including scattering by atmospheric particles is examined for the application of infrared limb remote sensing measurements. Here we focus on the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the European Space Agency's Envisat. Various spectra for clear air and cloudy conditions were simulated with a spectrally averaging radiative transfer model and a line-by-line radiative transfer model for three atmospheric window regions (825-830, 946-951, 1224-1228 cm-1) and compared to each other. The results are rated in terms of the MIPAS noise equivalent spectral radiance (NESR). The clear air simulations generally agree within one NESR. The cloud simulations neglecting the scattering source term agree within two NESR. The differences between the cloud simulations including the scattering source term are generally below three and always below four NESR. We conclude that the spectrally averaging approach is well suited for fast and accurate infrared radiative transfer simulations including scattering by clouds. We found that the main source for the differences between the cloud simulations of both models is the cloud edge sampling. Furthermore we reasoned that this model comparison for clouds is also valid for atmospheric aerosol in general.

On the Non-Equilibrium Population Distribution of E-Methanol in Dark Clouds

NASA Astrophysics Data System (ADS)

Wollman, Emma

2007-12-01

The goal of this project was to determine the typical distribution of rotational level populations in the k=0 ladder of E-methanol in dark clouds in order to provide another observational test for theoretical models of pumping. We used our own observations of several sources with the 12-m ARO telescope on Kitt Peak as well as the published observational results by Slysh et al. (1999). The relative level populations (excitation temperatures) were determined from the measured intensity ratios of a series of the J(0)-J(-1) transitions of E-methanol under the assumption of spontaneous, optically thin emission. We observed the J(0)-J(-1) lines in six sources: W75N, DR21N, DR21, and three positions at DR21OH. The J=1 to J=5 lines were observed for all sources and the J=7 line was observed for W75N, DR21N, and one position in DR21OH. We also used Slysh et al.'s results for the J=1 through 4 lines in 52 sources, for the J=5 line in 50 sources, for the J=6 line in 15 sources, and for the J=7 and 8 lines in 2 sources. We determined the excitation temperatures of the involved levels in the k=0 ladder relative to the 1(0) level for each source and averaged the results over the sources. The average excitation temperatures demonstrate strong evidence of overcooling in the k=0 ladder - the excitation temperature increases linearly with increasing energy, from 8 K to 35 K. Our observations confirm this tendency of overcooling. We will discuss the agreement of these results with the predictions of the current models of methanol pumping. The author thanks the technical staff of the 12-m ARO telescope for help with the observations. This project was supported by the NSF/REU grant AST-0354056 and the Nantucket Maria Mitchell Association.

Body and Surface Wave Modeling of Observed Seismic Events. Part 2.

DTIC Science & Technology

1987-05-12

is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical S coordinates in an asymptotic form which...using line source (2-D) theory. It is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical...generating synthetic point-source seismograms for shear dislocation sources using line source (2-D) theory. It is based on expanding the complete three

Object localization through the lateral line system of fish: theory and experiment.

PubMed

Goulet, Julie; Engelmann, Jacob; Chagnaud, Boris P; Franosch, Jan-Moritz P; Suttner, Maria D; van Hemmen, J Leo

2008-01-01

Fish acquire information about their aquatic environment by means of their mechanosensory lateral-line system. This system consists of superficial and canal neuromasts that sense perturbations in the water surrounding them. Based on a hydrodynamic model presented here, we propose a mechanism through which fish can localize the source of these perturbations. In doing so we include the curvature of the fish body, a realistic lateral line canal inter-pore distance for the lateral-line canals, and the surface boundary layer. Using our model to explore receptor behavior based on experimental data of responses to dipole stimuli we suggest that superficial and canal neuromasts employ the same mechanism, hence provide the same type of input to the central nervous system. The analytical predictions agree well with spiking responses recorded experimentally from primary lateral-line nerve fibers. From this, and taking into account the central organization of the lateral-line system, we present a simple biophysical model for determining the distance to a source.

Sodium D-line emission from Io - Comparison of observed and theoretical line profiles

NASA Technical Reports Server (NTRS)

Carlson, R. W.; Matson, D. L.; Johnson, T. V.; Bergstralh, J. T.

1978-01-01

High-resolution spectra of the D-line profiles have been obtained for Io's sodium emission cloud. These lines, which are produced through resonance scattering of sunlight, are broad and asymmetric and can be used to infer source and dynamical properties of the sodium cloud. In this paper we compare line profile data with theoretical line shapes computed for several assumed initial velocity distributions corresponding to various source mechanisms. We also examine the consequences of source distributions which are nonuniform over the surface of Io. It is found that the experimental data are compatible with escape of sodium atoms from the leading hemisphere of Io and with velocity distributions characteristic of sputtering processes. Thermal escape and simple models of plasma sweeping are found to be incompatible with the observations.

Chandra and XMM Observations of the ADC Source 0921-630

NASA Technical Reports Server (NTRS)

Kallman, T. R.; Angelini, L.; Boroson, B.; Cottam, J.; White, Nicholas E. (Technical Monitor)

2002-01-01

We analyze observations of the low mass X-ray binary 2S0921-63 obtained with the gratings and CCDs on Chandra and XMM. This object is a high inclination system showing evidence for an accretion disk corona (ADC). Such a corona has the potential to constrain the properties of the heated accretion disk in this system, and other LMXBs by extension. We find evidence for line emission which is generally consistent with that found by previous experiments, although we are able to detect more lines. For the first time in this source, we find that the iron K line has multiple components. We set limits on the line widths and velocity offsets, and we fit the spectra to photoionization models and discuss the implications for accretion disk corona models. For the first time in any ADC source we use these fits, together with density constraints based on the O VII line ratio, in order to constrain the flux in the medium-ionization region of the ADC. Under various assumptions about the source luminosity this constrains the location of the emitting region. These estimates, together with estimates for the emission measure, favor a scenario in which the intrinsic luminosity of the source is comparable to what we observe.

Dual-Source Linear Energy Prediction (LINE-P) Model in the Context of WSNs

PubMed Central

Ahmed, Faisal

2017-01-01

Energy harvesting technologies such as miniature power solar panels and micro wind turbines are increasingly used to help power wireless sensor network nodes. However, a major drawback of energy harvesting is its varying and intermittent characteristic, which can negatively affect the quality of service. This calls for careful design and operation of the nodes, possibly by means of, e.g., dynamic duty cycling and/or dynamic frequency and voltage scaling. In this context, various energy prediction models have been proposed in the literature; however, they are typically compute-intensive or only suitable for a single type of energy source. In this paper, we propose Linear Energy Prediction “LINE-P”, a lightweight, yet relatively accurate model based on approximation and sampling theory; LINE-P is suitable for dual-source energy harvesting. Simulations and comparisons against existing similar models have been conducted with low and medium resolutions (i.e., 60 and 22 min intervals/24 h) for the solar energy source (low variations) and with high resolutions (15 min intervals/24 h) for the wind energy source. The results show that the accuracy of the solar-based and wind-based predictions is up to approximately 98% and 96%, respectively, while requiring a lower complexity and memory than the other models. For the cases where LINE-P’s accuracy is lower than that of other approaches, it still has the advantage of lower computing requirements, making it more suitable for embedded implementation, e.g., in wireless sensor network coordinator nodes or gateways. PMID:28726745

Cyclotron Line Measurements with INTEGRAL

NASA Technical Reports Server (NTRS)

Pottschmidt, K.; Kreykenbohm, I.; Caballero, I.; Fritz, S.; Schoenherr, G.; Kretschmar, P.; Wilms, J.; McBride, V. A.; Suchy, S.; Rothschild, R. E.

2008-01-01

Due to its broadband energy coverage, INTEGRAL has made important contributions to observing and interpreting cyclotron lines, which are present in the 10-100 keV range of a sample of accreting pulsars. In these systems photons with energies fulfilling the resonance condition inelastically Compton scatter off electrons quantized in the accretion column above the neutron star's magnetic pole(s). This process gives rise to the broad, absorption-like lines or 'cyclotron resonant scattering features' (CRSF). The observed lines allow to directly measure the B-fields of these sources, resulting in values of a few times 1E12G. In this overview I will present recent highlights regarding CRSF observations as well as discuss current ideas and models for the physical conditions in the accretion column. Among the former are the stability of the spectrum of Vela X-1 during giant flares in 2003, the observation of three cyclotron lines during the 2004 outburst of V0332+53, the confirmation of the fundamental line at approximately 45 keV during a 2005 normal outburst of A0535-26, and the simultaneous detection of the two lines in the dipping source 4U 1907+09 (for which also a torque reversal was detected for the first time). Through these and other observations it has become increasingly apparent that two types of observations can potentially be used to constrain the accretion column geometry: the determination of energy ratios for multiple harmonic lines (only two sources with greater than 2 lines are known), was well as the evolution of the fundamental line centroid, which, for different sources, may or may not be correlated with flux. Furthermore, first steps have been taken away from the usual phenomenological description of the lines, towards a physical approach based on self-consistent CRSF modeling. Initial applications are presented.

Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes

NASA Technical Reports Server (NTRS)

T.Dauser; Garcia, J.; Wilms, J.; Boeck, M.; Brenneman, L. W.; Falanga, M.; Fukumura, Keigo; Reynolds, C. S.

2013-01-01

X-ray irradiation of the accretion disc leads to strong reflection features, which are then broadened and distorted by relativistic effects. We present a detailed, general relativistic approach to model this irradiation for different geometries of the primary X-ray source. These geometries include the standard point source on the rotational axis as well as more jet-like sources, which are radially elongated and accelerating. Incorporating this code in the RELLINE model for relativistic line emission, the line shape for any configuration can be predicted. We study how different irradiation geometries affect the determination of the spin of the black hole. Broad emission lines are produced only for compact irradiating sources situated close to the black hole. This is the only case where the black hole spin can be unambiguously determined. In all other cases the line shape is narrower, which could either be explained by a low spin or an elongated source. We conclude that for those cases and independent of the quality of the data, no unique solution for the spin exists and therefore only a lower limit of the spin value can be given

Investigation of structural heterogeneity at the SPE site using combined P–wave travel times and Rg phase velocities

DOE PAGES

Rowe, Charlotte A.; Patton, Howard J.

2015-10-01

Here, we present analyses of the 2D seismic structure beneath Source Physics Experiments (SPE) geophone lines that extended radially at 100 m spacing from 100 to 2000 m from the source borehole. With seismic sources at only one end of the geophone lines, standard refraction profiling methods cannot resolve seismic velocity structures unambiguously. In previous work, we demonstrated overall agreement between body-wave refraction modeling and Rg dispersion curves for the least complex of the five lines. A more detailed inspection supports a 2D reinterpretation of the structure. We obtained Rg phase velocity measurements in both the time and frequency domains,more » then used iterative adjustment of the initial 1D body-wave model to predict Rg dispersion curves to fit the observed values. Our method applied to the most topographically severe of the geophone lines is supplemented with a 2D ray-tracing approach, whose application to P-wave arrivals supports the Rg analysis. In addition, midline sources will allow us to refine our characterization in future work.« less

NLTE Model Atmospheres for Super-Soft X-ray Sources

NASA Astrophysics Data System (ADS)

Rauch, Thomas; Werner, Klaus

2009-09-01

Spectral analysis by means of fully line-blanketed Non-LTE model atmospheres has arrived at a high level of sophistication. The Tübingen NLTE Model Atmosphere Package (TMAP) is used to calculate plane-parallel NLTE model atmospheres which are in radiative and hydrostatic equilibrium. Although TMAP is not especially designed for the calculation of burst spectra of novae, spectral energy distributions (SEDs) calculated from TMAP models are well suited e.g. for abundance determinations of Super Soft X-ray Sources like nova V4743 Sgr or line identifications in observations of neutron stars with low magnetic fields in low-mass X-ray binaries (LMXBs) like EXO 0748-676.

A coronal magnetic field model with horizontal volume and sheet currents

NASA Technical Reports Server (NTRS)

Zhao, Xuepu; Hoeksema, J. Todd

1994-01-01

When globally mapping the observed photospheric magnetic field into the corona, the interaction of the solar wind and magnetic field has been treated either by imposing source surface boundary conditions that tacitly require volume currents outside the source surface or by limiting the interaction to thin current sheets between oppositely directed field regions. Yet observations and numerical Magnetohydrodynamic (MHD) calculations suggest the presence of non-force-free volume currents throughout the corona as well as thin current sheets in the neighborhoods of the interfaces between closed and open field lines or between oppositely directed open field lines surrounding coronal helmet-streamer structures. This work presents a model including both horizontal volume currents and streamer sheet currents. The present model builds on the magnetostatic equilibria developed by Bogdan and Low and the current-sheet modeling technique developed by Schatten. The calculation uses synoptic charts of the line-of-sight component of the photospheric magnetic field measured at the Wilcox Solar Observatory. Comparison of an MHD model with the calculated model results for the case of a dipole field and comparison of eclipse observations with calculations for CR 1647 (near solar minimum) show that this horizontal current-current-sheet model reproduces polar plumes and axes of corona streamers better than the source-surface model and reproduces polar plumes and axes of corona streamers better than the source-surface model and reproduces coro nal helmet structures better than the current-sheet model.

Cell sources for in vitro human liver cell culture models.

PubMed

Zeilinger, Katrin; Freyer, Nora; Damm, Georg; Seehofer, Daniel; Knöspel, Fanny

2016-09-01

In vitro liver cell culture models are gaining increasing importance in pharmacological and toxicological research. The source of cells used is critical for the relevance and the predictive value of such models. Primary human hepatocytes (PHH) are currently considered to be the gold standard for hepatic in vitro culture models, since they directly reflect the specific metabolism and functionality of the human liver; however, the scarcity and difficult logistics of PHH have driven researchers to explore alternative cell sources, including liver cell lines and pluripotent stem cells. Liver cell lines generated from hepatomas or by genetic manipulation are widely used due to their good availability, but they are generally altered in certain metabolic functions. For the past few years, adult and pluripotent stem cells have been attracting increasing attention, due their ability to proliferate and to differentiate into hepatocyte-like cells in vitro However, controlling the differentiation of these cells is still a challenge. This review gives an overview of the major human cell sources under investigation for in vitro liver cell culture models, including primary human liver cells, liver cell lines, and stem cells. The promises and challenges of different cell types are discussed with a focus on the complex 2D and 3D culture approaches under investigation for improving liver cell functionality in vitro Finally, the specific application options of individual cell sources in pharmacological research or disease modeling are described. © 2016 by the Society for Experimental Biology and Medicine.

Cell sources for in vitro human liver cell culture models

PubMed Central

Freyer, Nora; Damm, Georg; Seehofer, Daniel; Knöspel, Fanny

2016-01-01

In vitro liver cell culture models are gaining increasing importance in pharmacological and toxicological research. The source of cells used is critical for the relevance and the predictive value of such models. Primary human hepatocytes (PHH) are currently considered to be the gold standard for hepatic in vitro culture models, since they directly reflect the specific metabolism and functionality of the human liver; however, the scarcity and difficult logistics of PHH have driven researchers to explore alternative cell sources, including liver cell lines and pluripotent stem cells. Liver cell lines generated from hepatomas or by genetic manipulation are widely used due to their good availability, but they are generally altered in certain metabolic functions. For the past few years, adult and pluripotent stem cells have been attracting increasing attention, due their ability to proliferate and to differentiate into hepatocyte-like cells in vitro. However, controlling the differentiation of these cells is still a challenge. This review gives an overview of the major human cell sources under investigation for in vitro liver cell culture models, including primary human liver cells, liver cell lines, and stem cells. The promises and challenges of different cell types are discussed with a focus on the complex 2D and 3D culture approaches under investigation for improving liver cell functionality in vitro. Finally, the specific application options of individual cell sources in pharmacological research or disease modeling are described. PMID:27385595

Finite-Length Line Source Superposition Model (FLLSSM)

NASA Astrophysics Data System (ADS)

1980-03-01

A linearized thermal conduction model was developed to economically determine media temperatures in geologic repositories for nuclear wastes. Individual canisters containing either high level waste or spent fuel assemblies were represented as finite length line sources in a continuous media. The combined effects of multiple canisters in a representative storage pattern were established at selected points of interest by superposition of the temperature rises calculated for each canister. The methodology is outlined and the computer code FLLSSM which performs required numerical integrations and superposition operations is described.

Where are the Fermi lines coming from?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Kanishka; Whiteson, Daniel, E-mail: krao@uci.edu, E-mail: daniel@uci.edu

2013-03-01

We estimate the spatial locations of sources of the the observed features in the Fermi-LAT photon spectrum at E{sub γ} = 110 and E{sub γ} = 130 GeV. We determine whether they are consistent with emission from a single source, as would be expected in their interpretation as γγ and γZ lines from dark matter annhiliation, as well as whether they are consistent with a dark matter halo positioned at the center of the galaxy. We take advantage of the per-photon measured incident angle in reconstructing the line features. In addition, we use a data-driven background model rather than makingmore » the assumption of a feature-less background. We localize the sources of the features at 110 and 130 GeV. Assuming an Einasto (NFW) density model we find the 130 GeV line to be offset from the Galactic center by 285 (280) pc, the 110 GeV line by 60 (30) pc with a large relative separation of 220 (240) pc. However, we find this displacement of each source from the Galactic center, as well as their relative displacement to be statistically consistent with a single Einasto or NFW dark matter halo at the center of the galaxy.« less

Computationally efficient thermal-mechanical modelling of selective laser melting

NASA Astrophysics Data System (ADS)

Yang, Yabin; Ayas, Can

2017-10-01

The Selective laser melting (SLM) is a powder based additive manufacturing (AM) method to produce high density metal parts with complex topology. However, part distortions and accompanying residual stresses deteriorates the mechanical reliability of SLM products. Modelling of the SLM process is anticipated to be instrumental for understanding and predicting the development of residual stress field during the build process. However, SLM process modelling requires determination of the heat transients within the part being built which is coupled to a mechanical boundary value problem to calculate displacement and residual stress fields. Thermal models associated with SLM are typically complex and computationally demanding. In this paper, we present a simple semi-analytical thermal-mechanical model, developed for SLM that represents the effect of laser scanning vectors with line heat sources. The temperature field within the part being build is attained by superposition of temperature field associated with line heat sources in a semi-infinite medium and a complimentary temperature field which accounts for the actual boundary conditions. An analytical solution of a line heat source in a semi-infinite medium is first described followed by the numerical procedure used for finding the complimentary temperature field. This analytical description of the line heat sources is able to capture the steep temperature gradients in the vicinity of the laser spot which is typically tens of micrometers. In turn, semi-analytical thermal model allows for having a relatively coarse discretisation of the complimentary temperature field. The temperature history determined is used to calculate the thermal strain induced on the SLM part. Finally, a mechanical model governed by elastic-plastic constitutive rule having isotropic hardening is used to predict the residual stresses.

Investigation of hydraulic transmission noise sources

NASA Astrophysics Data System (ADS)

Klop, Richard J.

Advanced hydrostatic transmissions and hydraulic hybrids show potential in new market segments such as commercial vehicles and passenger cars. Such new applications regard low noise generation as a high priority, thus, demanding new quiet hydrostatic transmission designs. In this thesis, the aim is to investigate noise sources of hydrostatic transmissions to discover strategies for designing compact and quiet solutions. A model has been developed to capture the interaction of a pump and motor working in a hydrostatic transmission and to predict overall noise sources. This model allows a designer to compare noise sources for various configurations and to design compact and inherently quiet solutions. The model describes dynamics of the system by coupling lumped parameter pump and motor models with a one-dimensional unsteady compressible transmission line model. The model has been verified with dynamic pressure measurements in the line over a wide operating range for several system structures. Simulation studies were performed illustrating sensitivities of several design variables and the potential of the model to design transmissions with minimal noise sources. A semi-anechoic chamber has been designed and constructed suitable for sound intensity measurements that can be used to derive sound power. Measurements proved the potential to reduce audible noise by predicting and reducing both noise sources. Sound power measurements were conducted on a series hybrid transmission test bench to validate the model and compare predicted noise sources with sound power.

Predicting air quality near roadways through the application of a Gaussian Puff Model to moving sources

DOT National Transportation Integrated Search

2000-06-19

The Environmental Protection Agency (EPA) currently recommends the use of CALINE3 or CAL3QHC for modeling the dispersion of carbon monoxide (CO) near roadways. These models treat vehicles as part of a line source such that the emissions are homogeneo...

Seismoelectric imaging of shallow targets

USGS Publications Warehouse

Haines, S.S.; Pride, S.R.; Klemperer, S.L.; Biondi, B.

2007-01-01

We have undertaken a series of controlled field experiments to develop seismoelectric experimental methods for near-surface applications and to improve our understanding of seismoelectric phenomena. In a set of off-line geometry surveys (source separated from the receiver line), we place seismic sources and electrode array receivers on opposite sides of a man-made target (two sand-filled trenches) to record separately two previously documented seismoelectric modes: (1) the electromagnetic interface response signal created at the target and (2) the coseismic electric fields located within a compressional seismic wave. With the seismic source point in the center of a linear electrode array, we identify the previously undocumented seismoelectric direct field, and the Lorentz field of the metal hammer plate moving in the earth's magnetic field. We place the seismic source in the center of a circular array of electrodes (radial and circumferential orientations) to analyze the source-related direct and Lorentz fields and to establish that these fields can be understood in terms of simple analytical models. Using an off-line geometry, we create a multifold, 2D image of our trenches as dipping layers, and we also produce a complementary synthetic image through numerical modeling. These images demonstrate that off-line geometry (e.g., crosswell) surveys offer a particularly promising application of the seismoelectric method because they effectively separate the interface response signal from the (generally much stronger) coseismic and source-related fields. ?? 2007 Society of Exploration Geophysicists.

Spectral Simulations and Abundance Determinations in the Interstellar Medium of Active Galaxies

NASA Astrophysics Data System (ADS)

Ferguson, Jason W.

The narrow emission line spectra of gas illuminated by the nuclear region of active galaxies cannot be described by models involving simple photoionization calculations. In this project we develop the numerical tools necessary to accurately simulate observed spectra from such regions. We begin by developing a compact model hydrogen atom, and show that a moderate number of atomic levels can reproduce the emission of much larger, definitive calculations. We discuss the excitation mechanism of the gas, that is, whether the emission we see is a result of either local shock excitation or direct photoionization by the central source. We show that photoionization plus continuum fluorescence can mimic excitation by shocks, and we suggest an observational test to distinguish between photoionization due to shocks and the central source. We extend to the narrow line region of active galaxies the 'locally optimally-emitting cloud' (LOC) model, wherein the observed spectra are predominantly determined by a simple, yet powerful selection effect. Namely, nature provides the emitting line region with clouds of a vast ensemble of properties, and we observe emission lines from those clouds that are most efficient at emitting them. We have calculated large grids of photoionization models of narrow line clouds for a wide range of gas density and distances from the ionizing source. We show that when coupled to a simple Keplerian velocity field, the LOC naturally reproduces the line width - critical density correlation observed in many narrow line objects. In addition, we calculate classical diagnostic line ratios and use simple LOC integrations over gas density to simulate the radial emission of the narrow lines and compare with observations. The effects of including dust in the simulations is discussed and we show that the more neutral gas is likely to be dusty, while the more highly ionized gas is dust-free. This implies a variety of cloud origins.

Development of an on-line source-tagged model for sulfate, nitrate and ammonium: A modeling study for highly polluted periods in Shanghai, China.

PubMed

Wu, Jian-Bin; Wang, Zifa; Wang, Qian; Li, Jie; Xu, Jianming; Chen, HuanSheng; Ge, Baozhu; Zhou, Guangqiang; Chang, Luyu

2017-02-01

An on-line source-tagged model coupled with an air quality model (Nested Air Quality Prediction Model System, NAQPMS) was applied to estimate source contributions of primary and secondary sulfate, nitrate and ammonium (SNA) during a representative winter period in Shanghai. This source-tagged model system could simultaneously track spatial and temporal sources of SNA, which were apportioned to their respective primary precursors in a simulation run. The results indicate that in the study period, local emissions in Shanghai accounted for over 20% of SNA contributions and that Jiangsu and Shandong were the two major non-local sources. In particular, non-local emissions had higher contributions during recorded pollution periods. This suggests that the transportation of pollutants plays a key role in air pollution in Shanghai. The temporal contributions show that the emissions from the "current day" (emission contribution from the current day during which the model was simulating) contributed 60%-70% of the sulfate and ammonium concentrations but only 10%-20% of the nitrate concentration, while the previous days' contributions increased during the recorded pollution periods. Emissions that were released within three days contributed over 85% averagely for SNA in January 2013. To evaluate the source-tagged model system, the results were compared by sensitivity analysis (emission perturbation of -30%) and backward trajectory analysis. The consistency of the comparison results indicated that the source-tagged model system can track sources of SNA with reasonable accuracy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Probabilistic drug connectivity mapping

PubMed Central

2014-01-01

Background The aim of connectivity mapping is to match drugs using drug-treatment gene expression profiles from multiple cell lines. This can be viewed as an information retrieval task, with the goal of finding the most relevant profiles for a given query drug. We infer the relevance for retrieval by data-driven probabilistic modeling of the drug responses, resulting in probabilistic connectivity mapping, and further consider the available cell lines as different data sources. We use a special type of probabilistic model to separate what is shared and specific between the sources, in contrast to earlier connectivity mapping methods that have intentionally aggregated all available data, neglecting information about the differences between the cell lines. Results We show that the probabilistic multi-source connectivity mapping method is superior to alternatives in finding functionally and chemically similar drugs from the Connectivity Map data set. We also demonstrate that an extension of the method is capable of retrieving combinations of drugs that match different relevant parts of the query drug response profile. Conclusions The probabilistic modeling-based connectivity mapping method provides a promising alternative to earlier methods. Principled integration of data from different cell lines helps to identify relevant responses for specific drug repositioning applications. PMID:24742351

A Near-Road Modeling System for Community-Scale Assessments of Traffic-Related AirPollution in the United States

EPA Science Inventory

The Community Line Source (C-LINE) modeling system estimates emissions and dispersion of toxic air pollutants for roadways within the continental United States. It accesses publicly available traffic and meteorological datasets, and is optimized for use on community-sized areas (...

Cost Effectiveness of On-Line Retrieval System.

ERIC Educational Resources Information Center

King, Donald W.; Neel, Peggy W.

A recently developed cost-effectiveness model for on-line retrieval systems is discussed through use of an example utilizing performance results collected from several independent sources and cost data derived for a recently completed study for the American Psychological Association. One of the primary attributes of the model rests in its great…

Reduced-form air quality modeling for community-scale ...

EPA Pesticide Factsheets

Transportation plays an important role in modern society, but its impact on air quality has been shown to have significant adverse effects on public health. Numerous reviews (HEI, CDC, WHO) summarizing findings of hundreds of studies conducted mainly in the last decade, conclude that exposures to traffic emissions near roads are a public health concern. The Community LINE Source Model (C-LINE) is a web-based model designed to inform the community user of local air quality impacts due to roadway vehicles in their region of interest using a simplified modeling approach. Reduced-form air quality modeling is a useful tool for examining what-if scenarios of changes in emissions, such as those due to changes in traffic volume, fleet mix, or vehicle speed. Examining various scenarios of air quality impacts in this way can identify potentially at-risk populations located near roadways, and the effects that a change in traffic activity may have on them. C-LINE computes dispersion of primary mobile source pollutants using meteorological conditions for the region of interest and computes air-quality concentrations corresponding to these selected conditions. C-LINE functionality has been expanded to model emissions from port-related activities (e.g. ships, trucks, cranes, etc.) in a reduced-form modeling system for local-scale near-port air quality analysis. This presentation describes the Community modeling tools C-LINE and C-PORT that are intended to be used by local gove

X-ray reflection from cold white dwarfs in magnetic cataclysmic variables

NASA Astrophysics Data System (ADS)

Hayashi, Takayuki; Kitaguchi, Takao; Ishida, Manabu

2018-02-01

We model X-ray reflection from white dwarfs (WDs) in magnetic cataclysmic variables (mCVs) using a Monte Carlo simulation. A point source with a power-law spectrum or a realistic post-shock accretion column (PSAC) source irradiates a cool and spherical WD. The PSAC source emits thermal spectra of various temperatures stratified along the column according to the PSAC model. In the point-source simulation, we confirm the following: a source harder and nearer to the WD enhances the reflection; higher iron abundance enhances the equivalent widths (EWs) of fluorescent iron Kα1, 2 lines and their Compton shoulder, and increases the cut-off energy of a Compton hump; significant reflection appears from an area that is more than 90° apart from the position right under the point X-ray source because of the WD curvature. The PSAC simulation reveals the following: a more massive WD basically enhances the intensities of the fluorescent iron Kα1, 2 lines and the Compton hump, except for some specific accretion rate, because the more massive WD makes a hotter PSAC from which higher-energy X-rays are preferentially emitted; a larger specific accretion rate monotonically enhances the reflection because it makes a hotter and shorter PSAC; the intrinsic thermal component hardens by occultation of the cool base of the PSAC by the WD. We quantitatively estimate the influences of the parameters on the EWs and the Compton hump with both types of source. We also calculate X-ray modulation profiles brought about by the WD spin. These depend on the angles of the spin axis from the line of sight and from the PSAC, and on whether the two PSACs can be seen. The reflection spectral model and the modulation model involve the fluorescent lines and the Compton hump and can directly be compared to the data, which allows us to estimate these geometrical parameters with unprecedented accuracy.

Spectral properties of X-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero-Colmenero, E.

1998-03-01

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (<= 2e-15 ergs cm-2 s-1), thus suggesting that NELGs are important contributors to the residual soft (<2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (alpha~0.4, 1-10 keV) is harder than that of AGN (alpha~1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha~0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to constitute it. Furthermore, by combining both samples of NELGs, I find a tendency for sources at lower fluxes to display harder slopes (95% confidence level), further strengthening the case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (Halpha, Hbeta, [NII]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines, this is at variance with what is observed in broad line AGN. The FWHM of the Balmer lines is also correlated to the FWHM of the forbidden lines, indicating that they must originate in regions of similar velocity fields. Unfortunately, the number of sources uniquely classified is not sufficient to investigate these relationships on a source type basis. The optical emission line ratios of a bright RIXOS source (aka Arp 185, NGC 6217), classified as a starburst galaxy in the literature, indicate that this is in fact a weak-[OI] LINER, powered either by emission from hot O stars or by hot stars together with a non-stellar continuum. Spatially resolved spectroscopic analysis suggests that the Balmer emission lines are concentrated in the inner regions of the nucleus, while the forbidden lines arise from a more extended region. Line ratios do not indicate a change in the ionizing continuum of this source with distance from the centre.

Spectral properties of x-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero Colmenero, Encarnacion

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha ~ 1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for NH. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law spectral slope of the average NELG is S = 0.45 +/- 0.09, whilst that of the AGN is S = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (< 2 x 10-15erg cm-2 s -1), thus suggesting that NELGs are important contributors to the residual soft (< 2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (S ~ 0.4, 1-10 keV) is harder than that of AGN (S ~ 1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha ~ 0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to constitute it. Furthermore, by combining both samples of NELGs, I find a tendency for sources at lower fluxes to display harder slopes (95% confidence level), further strengthening the case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (H, [NH]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines, this at variance with what is observed in broad line AGN. The FWHM of the Balmer lines is also correlated to the FWHM of the forbidden lines, indicating that they must originate in regions of similar velocity fields. Unfortunately, the number of sources uniquely classified is not sufficient to investigate these relationships on a source type basis. The optical emission line ratios of a bright RIXOS source (aka Arp 185, NGC 6217), classified as a starburst galaxy in the literature, indicate that this is in fact a weak-[OI] LINER, powered either by emission from hot O stars or by hot stars together with a non-stellar continuum. Spatially resolved spectroscopic analysis suggests that the Balmer emission lines are concentrated in the inner regions of the nucleus, while the forbidden lines arise from a more extended region. Line ratios do not indicate a change in the ionizing continuum of this source with distance from the centre.

Two methods for transmission line simulation model creation based on time domain measurements

NASA Astrophysics Data System (ADS)

Rinas, D.; Frei, S.

2011-07-01

The emission from transmission lines plays an important role in the electromagnetic compatibility of automotive electronic systems. In a frequency range below 200 MHz radiation from cables is often the dominant emission factor. In higher frequency ranges radiation from PCBs and their housing becomes more relevant. Main sources for this emission are the conducting traces. The established field measurement methods according CISPR 25 for evaluation of emissions suffer from the need to use large anechoic chambers. Furthermore measurement data can not be used for simulation model creation in order to compute the overall fields radiated from a car. In this paper a method to determine the far-fields and a simulation model of radiating transmission lines, esp. cable bundles and conducting traces on planar structures, is proposed. The method measures the electromagnetic near-field above the test object. Measurements are done in time domain in order to get phase information and to reduce measurement time. On the basis of near-field data equivalent source identification can be done. Considering correlations between sources along each conductive structure in model creation process, the model accuracy increases and computational costs can be reduced.

A spatial analysis of the dispersion of transportation induced carbon monoxide using the Gaussian line source method

NASA Astrophysics Data System (ADS)

Tarigan, A. P. M.; Suryati, I.; Gusrianti, D.

2018-03-01

The Purpose of this study is to model the spatial distribution of transportation induced carbon monoxide (CO) from a street, i.e. Jl. Singamangaraja, in Medan City using the gaussian line source method with GIS. It is observed that the traffic volume on the Jl. Singamangaraja is 7,591 units/hour in the morning and 7,433 units/hour in the afternoon. The amount emission rate is 49,171.7 µg/m.s in the morning and 46,943.1 µg/m.s in the afternoon. Based on the gaussian line source method, the highest CO concentration is found at the roadside, i.e. 20,340 µg/Nm3 in the morning and 18,340 µg/Nm3 in the afternoon, which are fairly in agreement with those measured in situ. Using GIS, the CO spatial distribution can visually be modeled to observe the affected area.

New Maximum Tsunami Inundation Maps for Use by Local Emergency Planners in the State of California, USA

NASA Astrophysics Data System (ADS)

Wilson, R. I.; Barberopoulou, A.; Miller, K. M.; Goltz, J. D.; Synolakis, C. E.

2008-12-01

A consortium of tsunami hydrodynamic modelers, geologic hazard mapping specialists, and emergency planning managers is producing maximum tsunami inundation maps for California, covering most residential and transient populated areas along the state's coastline. The new tsunami inundation maps will be an upgrade from the existing maps for the state, improving on the resolution, accuracy, and coverage of the maximum anticipated tsunami inundation line. Thirty-five separate map areas covering nearly one-half of California's coastline were selected for tsunami modeling using the MOST (Method of Splitting Tsunami) model. From preliminary evaluations of nearly fifty local and distant tsunami source scenarios, those with the maximum expected hazard for a particular area were input to MOST. The MOST model was run with a near-shore bathymetric grid resolution varying from three arc-seconds (90m) to one arc-second (30m), depending on availability. Maximum tsunami "flow depth" and inundation layers were created by combining all modeled scenarios for each area. A method was developed to better define the location of the maximum inland penetration line using higher resolution digital onshore topographic data from interferometric radar sources. The final inundation line for each map area was validated using a combination of digital stereo photography and fieldwork. Further verification of the final inundation line will include ongoing evaluation of tsunami sources (seismic and submarine landslide) as well as comparison to the location of recorded paleotsunami deposits. Local governmental agencies can use these new maximum tsunami inundation lines to assist in the development of their evacuation routes and emergency response plans.

A resonant absorption line in the ASCA spectrum of NGC 985?

NASA Astrophysics Data System (ADS)

Nicastro, F.; Fiore, F.; Brandt, N.; Reynolds, C. S.

1999-01-01

We present timing and spectral analyses of the ASCA observation of the Seyfert 1 galaxy NGC 985. The 0.6-10keV spectrum of this source is complex: large residuals are evident below 1keV when fitting the spectrum with a power-law model. Fitting a warm absorber model to the 0.6-2.5keV spectrum gives α=1.12+/-0.04, LogNWAH=21.97+/-0.08 and LogU=0.06+/-0.09, but the residuals continue to show a deficit of counts between 0.9 and 1keV. Adding an absorption line improves the fit, and the energy of the line is consistent with that of Kα NeIX-X resonant absorption lines. Hence, we confirm the presence of an ionized absorber along the line of sight to this source and interpret the further 1keV spectral feature as the first detection of a strong resonant absorption line associated with this system. The extrapolation of this model above 2.5keV produces large positive residuals above 3-4keV. Fitting the data with a broken power law plus warm absorber model gives an acceptable χ2 and Δα~0.5. A narrow iron line at 6.4keV (quasar frame) of equivalent width 138+64-110eV is also present in the ASCA data.

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strom, Daniel J.; Cerra, Frank

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3)more » a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow “pencil” beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source, or b) during the traversal of a point source, is a unifying concept. The “universal source strength” of air kerma rate at a meter from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.« less

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners.

PubMed

Strom, Daniel J; Cerra, Frank

2016-06-01

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3) a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow "pencil" beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source or b) during the traversal of a point source is a unifying concept. The "universal source strength" of air kerma rate at 1 m from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.

Imaging dipole flow sources using an artificial lateral-line system made of biomimetic hair flow sensors

PubMed Central

Dagamseh, Ahmad; Wiegerink, Remco; Lammerink, Theo; Krijnen, Gijs

2013-01-01

In Nature, fish have the ability to localize prey, school, navigate, etc., using the lateral-line organ. Artificial hair flow sensors arranged in a linear array shape (inspired by the lateral-line system (LSS) in fish) have been applied to measure airflow patterns at the sensor positions. Here, we take advantage of both biomimetic artificial hair-based flow sensors arranged as LSS and beamforming techniques to demonstrate dipole-source localization in air. Modelling and measurement results show the artificial lateral-line ability to image the position of dipole sources accurately with estimation error of less than 0.14 times the array length. This opens up possibilities for flow-based, near-field environment mapping that can be beneficial to, for example, biologists and robot guidance applications. PMID:23594816

Analysis of an entrainment model of the jet in a crossflow

NASA Technical Reports Server (NTRS)

Chang, H. S.; Werner, J. E.

1972-01-01

A theoretical model has been proposed for the problem of a round jet in an incompressible cross-flow. The method of matched asymptotic expansions has been applied to this problem. For the solution to the flow problem in the inner region, the re-entrant wake flow model was used with the re-entrant flow representing the fluid entrained by the jet. Higher order corrections are obtained in terms of this basic solution. The perturbation terms in the outer region was found to be a line distribution of doublets and sources. The line distribution of sources represents the combined effect of the entrainment and the displacement.

Non-LTE profiles of the Al I autoionization lines. [for solar model atmospheres

NASA Technical Reports Server (NTRS)

Finn, G. D.; Jefferies, J. T.

1974-01-01

A non-LTE formulation is given for the transfer of radiation in the autoionizing lines of neutral aluminum at 1932 and 1936 A through both the Bilderberg and Harvard-Smithsonian model atmospheres. Numerical solutions for the common source function of these lines and their theoretical line profiles are calculated and compared with the corresponding LTE profiles. The results show that the non-LTE profiles provide a better match with the observations. They also indicate that the continuous opacity of the standard solar models should be increased in this wavelength region if the center-limb variations of observed and theoretical profiles of these lines are to be in reasonable agreement.

Herschel GASPS spectral observations of T Tauri stars in Taurus. Unraveling far-infrared line emission from jets and discs

NASA Astrophysics Data System (ADS)

Alonso-Martínez, M.; Riviere-Marichalar, P.; Meeus, G.; Kamp, I.; Fang, M.; Podio, L.; Dent, W. R. F.; Eiroa, C.

2017-07-01

Context. At early stages of stellar evolution young stars show powerful jets and/or outflows that interact with protoplanetary discs and their surroundings. Despite the scarce knowledge about the interaction of jets and/or outflows with discs, spectroscopic studies based on Herschel and ISO data suggests that gas shocked by jets and/or outflows can be traced by far-IR (FIR) emission in certain sources. Aims: We want to provide a consistent catalogue of selected atomic ([OI] and [CII]) and molecular (CO, H2O, and OH) line fluxes observed in the FIR, separate and characterize the contribution from the jet and the disc to the observed line emission, and place the observations in an evolutionary picture. Methods: The atomic and molecular FIR (60-190 μm) line emission of protoplanetary discs around 76 T Tauri stars located in Taurus are analysed. The observations were carried out within the Herschel key programme Gas in Protoplanetary Systems (GASPS). The spectra were obtained with the Photodetector Array Camera and Spectrometer (PACS). The sample is first divided in outflow and non-outflow sources according to literature tabulations. With the aid of archival stellar/disc and jet/outflow tracers and model predictions (PDRs and shocks), correlations are explored to constrain the physical mechanisms behind the observed line emission. Results: Outflow sources exhibit brighter atomic and molecular emission lines and higher detection rates than non-outflow sources. The line detection fractions decrease with SED evolutionary status (from Class I to Class III). We find correlations between [OI] 63.18 μm and [OI] 6300 Å, o-H2O 78.74 μm, CO 144.78 μm, OH 79.12+79.18 μm, and the continuum flux at 24 μm. The atomic line ratios can be explain either by fast (Vshock > 50 km s-1) dissociative J-shocks at low densities (n 103 cm-3) occurring along the jet and/or PDR emission (G0 > 102, n 103-106 cm-3). To account for the [CII] absolute fluxes, PDR emission or UV irradiation of shocks is needed. In comparison, the molecular emission is more compact and the line ratios are better explained with slow (Vshock < 40 km s-1) C-type shocks with high pre-shock densities (104-106 cm-3), with the exception of OH lines, that are better described by J-type shocks. Disc models alone fail to reproduce the observed molecular line fluxes, but a contribution to the line fluxes from UV-illuminated discs and/or outflow cavities is expected. Far-IR lines dominate disc cooling at early stages and weaken as the star+disc system evolves from Class I to Class III, with an increasing relative disc contribution to the line fluxes. Conclusions: Models which take into account jets, discs, and their mutual interaction are needed to disentangle the different components and study their evolution. The much higher detection rate of emission lines in outflow sources and the compatibility of line ratios with shock model predictions supports the idea of a dominant contribution from the jet/outflow to the line emission, in particular at earlier stages of the stellar evolution as the brightness of FIR lines depends in large part on the specific evolutionary stage. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

A simple 2-d thermal model for GMA welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matteson, M.A.; Franke, G.L.; Vassilaros, M.G.

1996-12-31

The Rosenthal model of heat distribution from a moving source has been used in many applications to predict the temperature distribution during welding. The equation has performed well in its original form or as modified. The expression has a significant limitation for application to gas metal arc welds (GMAW) that have a papilla extending from the root of the weld bead. The shape of the fusion line between the papilla and the plate surface has a concave shape rather than the expected convex shape. However, at some distance from the fusion line the heat affected zone (HAZ) made visible bymore » etching has the expected convex shape predicted by the Rosenthal expression. This anomaly creates a limitation to the use of the Rosenthal expression for predicting GMAW bead shapes or HAZ temperature histories. Current research at the Naval Surface Warfare Center--Carderock Division (NSWC--CD) to develop a computer based model to predict the microstructure of multi-pass GMAW requires a simple expression to predict the fusion line and temperature history of the HAZ for each weld pass. The solution employed for the NSWC--CD research is a modified Rosenthal expression that has a dual heat source. One heat source is a disk source above the plate surface supplying the majority of the heat. The second heat source is smaller and below the surface of the plate. This second heat source helps simulate the penetration power of many GMAW welds that produces the papilla. The assumptions, strengths and limitations of the model are presented along with some applications.« less

First Detections of the [NII] 122 Micrometer Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

NASA Technical Reports Server (NTRS)

Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

2011-01-01

We report the first detections of the [NIl] 122 {\\mu} m line from a high redshift galaxy. The line was strongly (> 6{\\sigma}) detected from SMMJ02399-0136, and HI413+ 117 (the Cloverleaf QSO) using the Redshift(z) and Early Universe Spectrometer (ZEUS) on the CSO. The lines from both sources are quite bright with line-to-FIR continuum luminosity ratios that are approx.7.0x10(exp -4) (Cloverleaf) and 2.1x10(exp -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line-to-continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8 to 17% of the molecular gas mass. The [OIII]/[NII] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an AGN. Using our previous detection of the [01II] 88 {\\mu}m line, the [OIII]/ [NIl] line ratio for SMMJ02399-0136 indicates the dominant source of the line emission is either stellar HII regions ionized by 09.5 stars, or the NLR of the AGN with ionization parameter 10g(U) = -3.3 to -4.0. A composite system, where 30 to 50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82like starbursts accounting for all of the FIR emission and 43% of the [NIl] line. The remainder may come from the NLR. This work demonstrates the utility of the [NIl] and [OIII] lines in constraining properties of the ionized medium.

Localization of source with unknown amplitude using IPMC sensor arrays

NASA Astrophysics Data System (ADS)

Abdulsadda, Ahmad T.; Zhang, Feitian; Tan, Xiaobo

2011-04-01

The lateral line system, consisting of arrays of neuromasts functioning as flow sensors, is an important sensory organ for fish that enables them to detect predators, locate preys, perform rheotaxis, and coordinate schooling. Creating artificial lateral line systems is of significant interest since it will provide a new sensing mechanism for control and coordination of underwater robots and vehicles. In this paper we propose recursive algorithms for localizing a vibrating sphere, also known as a dipole source, based on measurements from an array of flow sensors. A dipole source is frequently used in the study of biological lateral lines, as a surrogate for underwater motion sources such as a flapping fish fin. We first formulate a nonlinear estimation problem based on an analytical model for the dipole-generated flow field. Two algorithms are presented to estimate both the source location and the vibration amplitude, one based on the least squares method and the other based on the Newton-Raphson method. Simulation results show that both methods deliver comparable performance in source localization. A prototype of artificial lateral line system comprising four ionic polymer-metal composite (IPMC) sensors is built, and experimental results are further presented to demonstrate the effectiveness of IPMC lateral line systems and the proposed estimation algorithms.

Faraday Rotation and Models for the Plasma Structure of the Solar Corona

NASA Astrophysics Data System (ADS)

Mancuso, Salvatore; Spangler, Steven R.

2000-08-01

Faraday rotation observations of polarized radiation from natural radio sources are unique among remote diagnostics of the solar corona in that they provide information on the coronal magnetic field. Dual frequency radio polarization measurements yield the rotation measure, a quantity that is proportional to the integral along the line of sight of the product of the electron density and the line-of-sight component of the magnetic field. We made linear polarization observations with the NRAO Very Large Array of 13 polarized radio sources occulted by the solar corona. The observations were made at frequencies of 1465 and 1665 MHz on four days in 1997 May and cover a 20 day period, sampling elongations ranging from about 5 to 14 Rsolar. The magnitudes of the rotation measures observed range from about 11 to 0 rad m-2. The relatively low values for the rotation measures are due to the solar minimum configuration of the corona at the time of the observations, with the lines of sight to the sources generally not crossing sector boundaries. The largest rotation measure was observed for the extended radio source 3C 79 on 1997 May 11 and corresponds to a case in which the line of sight passed next to the streamer belt at small solar elongations. We have developed a three-dimensional model of the solar corona that is in excellent agreement with the observed rotation measures, as well as being completely consistent with other coronal diagnostics such as coronagraph images. In particular, our observations support the coronal magnetic field model of Pätzold et al. (1987) they would be inconsistent with coronal magnetic fields significantly weaker or stronger than this model. The plasma density distribution in the corona is successfully modeled by a dense streamer belt component and a more tenuous coronal hole component. Details of these models are given in § 3 of this paper. The principal disagreement between the model and observations occurs for three lines of sight for which the model predicts nearly zero rotation measure but for which we measure small but significant values of -1 to -2 rad m-2. These lines of sight passed over the solar polar regions. We discuss the possibility that these residual rotation measures are due to static coronal plasma structures, not described by global coronal models, or to very long wavelength coronal Alfvén waves. Fluctuations in the rotation measure on timescales of a few hours were observed for some sources and not others. When detected, they were of order 1-2 rad m-2 and occurred on timescales of several hours.

Issues concerning centralized versus decentralized power deployment

NASA Technical Reports Server (NTRS)

Metcalf, Kenneth J.; Harty, Richard B.; Robin, James F.

1991-01-01

The results of a study of proposed lunar base architectures to identify issues concerning centralized and decentralized power system deployment options are presented. The power system consists of the energy producing system (power plant), the power conditioning components used to convert the generated power into the form desired for transmission, the transmission lines that conduct this power from the power sources to the loads, and the primary power conditioning hardware located at the user end. Three power system architectures, centralized, hybrid, and decentralized, were evaluated during the course of this study. Candidate power sources were characterized with respect to mass and radiator area. Two electrical models were created for each architecture to identify the preferred method of power transmission, dc or ac. Each model allowed the transmission voltage level to be varied at assess the impact on power system mass. The ac power system models also permitted the transmission line configurations and placements to determine the best conductor construction and installation location. Key parameters used to evaluate each configuration were power source and power conditioning component efficiencies, masses, and radiator areas; transmission line masses and operating temperatures; and total system mass.

Seismic Sources and Recurrence Rates as Adopted by USGS Staff for the Production of the 1982 and 1990 Probabilistic Ground Motion Maps for Alaska and the Conterminous United States

USGS Publications Warehouse

Hanson, Stanley L.; Perkins, David M.

1995-01-01

The construction of a probabilistic ground-motion hazard map for a region follows a sequence of analyses beginning with the selection of an earthquake catalog and ending with the mapping of calculated probabilistic ground-motion values (Hanson and others, 1992). An integral part of this process is the creation of sources used for the calculation of earthquake recurrence rates and ground motions. These sources consist of areas and lines that are representative of geologic or tectonic features and faults. After the design of the sources, it is necessary to arrange the coordinate points in a particular order compatible with the input format for the SEISRISK-III program (Bender and Perkins, 1987). Source zones are usually modeled as a point-rupture source. Where applicable, linear rupture sources are modeled with articulated lines, representing known faults, or a field of parallel lines, representing a generalized distribution of hypothetical faults. Based on the distribution of earthquakes throughout the individual source zones (or a collection of several sources), earthquake recurrence rates are computed for each of the sources, and a minimum and maximum magnitude is assigned. Over a period of time from 1978 to 1980 several conferences were held by the USGS to solicit information on regions of the United States for the purpose of creating source zones for computation of probabilistic ground motions (Thenhaus, 1983). As a result of these regional meetings and previous work in the Pacific Northwest, (Perkins and others, 1980), California continental shelf, (Thenhaus and others, 1980), and the Eastern outer continental shelf, (Perkins and others, 1979) a consensus set of source zones was agreed upon and subsequently used to produce a national ground motion hazard map for the United States (Algermissen and others, 1982). In this report and on the accompanying disk we provide a complete list of source areas and line sources as used for the 1982 and later 1990 seismic hazard maps for the conterminous U.S. and Alaska. These source zones are represented in the input form required for the hazard program SEISRISK-III, and they include the attenuation table and several other input parameter lines normally found at the beginning of an input data set for SEISRISK-III.

Time dependent emission line profiles in the radially streaming particle model of Seyfert galaxy nuclei and quasi-stellar objects

NASA Technical Reports Server (NTRS)

Hubbard, R.

1974-01-01

The radially-streaming particle model for broad quasar and Seyfert galaxy emission features is modified to include sources of time dependence. The results are suggestive of reported observations of multiple components, variability, and transient features in the wings of Seyfert and quasi-stellar emission lines.

Growth and Identification of Bacteria in N-Halamine Dental Unit Waterline Tubing Using an Ultrapure Water Source

PubMed Central

Porteous, Nuala; Luo, Jie; Hererra, Monica; Schoolfield, John; Sun, Yuyu

2011-01-01

This study examined bacterial growth and type on biofilm-controlling dental unit waterline (DUWL) tubing (T) and control manufacturer's tubing (C) in a laboratory DUWL model using ultrapure source water that was cycled through the lines. Sections of tubing lines were detached and examined for biofilm growth using SEM imaging at six sampling periods. Bacteria from inside surfaces of T and C, source unit, and reservoir were cultured and enumerated. At six months, organisms were molecularly identified from the alignment matches obtained from the top three BLAST searches for the 16S region. There was a 1–3 log increase in organism growth in a clean, nonsterile reservoir within an hour. Biofilm was established on the inside surfaces of C within three weeks, but not on T. Proteobacteria, and Sphingomonas spp. were identified in the source reservoir and C line, and a variation of the genera was found in T line. PMID:22220171

Non-line-of-sight ultraviolet link loss in noncoplanar geometry.

PubMed

Wang, Leijie; Xu, Zhengyuan; Sadler, Brian M

2010-04-15

Various path loss models have been developed for solar blind non-line-of-sight UV communication links under an assumption of coplanar source beam axis and receiver pointing direction. This work further extends an existing single-scattering coplanar analytical model to noncoplanar geometry. The model is derived as a function of geometric parameters and atmospheric characteristics. Its behavior is numerically studied in different noncoplanar geometric settings.

VUV spectroscopic observations on the SABRE applied-B ion diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filuk, A.B.; Nash, T.J.; Noack, D.D.

We are using VUV spectroscopy to study the ion source region on the SABRE applied-B extraction ion diode. The VUV diagnostic views the anode-cathode gap perpendicular to the ion acceleration direction, and images a region 0--1 mm from the anode onto the entrance slit of a I m normal-incidence spectrometer. Time resolution is obtained by gating multiple striplines of a CuI- or MgF{sub 2} -coated micro-channel plate intensifier. We report on results with a passive proton/carbon ion source. Lines of carbon and oxygen are observed over 900--1600 {angstrom}. The optical depths of most of the lines are less than ormore » of order 1. Unfolding the Doppler broadening of the ion lines in the source plasma, we calculate the contribution of the source to the accelerated C IV ion micro-divergence as 4 mrad at peak power. Collisional-radiative modeling of oxygen line intensities provides the source plasma average electron density of 7{times}10{sup 16} cm{sup {minus}3} and temperature of 10 eV Measurements are planned with a lithium ion source and with VUV absorption spectroscopy.« less

Resolved atomic lines reveal outflows in two ultraluminous X-ray sources.

PubMed

Pinto, Ciro; Middleton, Matthew J; Fabian, Andrew C

2016-05-05

Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in galaxies, and have X-ray luminosities in excess of 3 × 10(39) ergs per second. They are thought to be powered by accretion onto a compact object. Possible explanations include accretion onto neutron stars with strong magnetic fields, onto stellar-mass black holes (of up to 20 solar masses) at or in excess of the classical Eddington limit, or onto intermediate-mass black holes (10(3)-10(5) solar masses). The lack of sufficient energy resolution in previous analyses has prevented an unambiguous identification of any emission or absorption lines in the X-ray band, thereby precluding a detailed analysis of the accretion flow. Here we report the presence of X-ray emission lines arising from highly ionized iron, oxygen and neon with a cumulative significance in excess of five standard deviations, together with blueshifted (about 0.2 times light velocity) absorption lines of similar significance, in the high-resolution X-ray spectra of the ultraluminous X-ray sources NGC 1313 X-1 and NGC 5408 X-1. The blueshifted absorption lines must occur in a fast-outflowing gas, whereas the emission lines originate in slow-moving gas around the source. We conclude that the compact object in each source is surrounded by powerful winds with an outflow velocity of about 0.2 times that of light, as predicted by models of accreting supermassive black holes and hyper-accreting stellar-mass black holes.

New methods for interpretation of magnetic vector and gradient tensor data I: eigenvector analysis and the normalised source strength

NASA Astrophysics Data System (ADS)

Clark, David A.

2012-09-01

Acquisition of magnetic gradient tensor data is likely to become routine in the near future. New methods for inverting gradient tensor surveys to obtain source parameters have been developed for several elementary, but useful, models. These include point dipole (sphere), vertical line of dipoles (narrow vertical pipe), line of dipoles (horizontal cylinder), thin dipping sheet, and contact models. A key simplification is the use of eigenvalues and associated eigenvectors of the tensor. The normalised source strength (NSS), calculated from the eigenvalues, is a particularly useful rotational invariant that peaks directly over 3D compact sources, 2D compact sources, thin sheets and contacts, and is independent of magnetisation direction. In combination the NSS and its vector gradient determine source locations uniquely. NSS analysis can be extended to other useful models, such as vertical pipes, by calculating eigenvalues of the vertical derivative of the gradient tensor. Inversion based on the vector gradient of the NSS over the Tallawang magnetite deposit obtained good agreement between the inferred geometry of the tabular magnetite skarn body and drill hole intersections. Besides the geological applications, the algorithms for the dipole model are readily applicable to the detection, location and characterisation (DLC) of magnetic objects, such as naval mines, unexploded ordnance, shipwrecks, archaeological artefacts, and buried drums.

High-excitation lines of molecular hydrogen: A discriminant between shock models

NASA Technical Reports Server (NTRS)

Burton, M.; Brand, P.; Moorhouse, A.; Geballe, T.

1989-01-01

The results of column densities of molecular hydrogen, calculated from nineteen infrared line intensities, are discussed. They were measured at peak 1 of the outflow of the Orion molecular cloud OMC-1. The 1-0 O(7) and 0-0 S(13) lines of H2, at 3.8 microns, are mapped over the source. Their intensity ratio is found to be independent of position in the outflow. These observations are well fitted by a simple cooling-flow model of the line emitting region, but seem to be at variance with predictions of C-shocks current in the literature.

Relativistically Skewed Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

NASA Technical Reports Server (NTRS)

Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Kouveliotou, C.; Lewin, W. H. G.

2000-01-01

We report evidence for an Fe K-alpha fluorescence line feature in the Very High, High, and Low state X-ray spectra of the galactic microquasar XTE JI748-288 during its June 1998 outburst. Spectral analyses were made on observations spread across the outburst, gathered with the Rossi X-ray Timing Explorer. Gaussian line. disk emission line, relativistic disk emission line, and disk reflection models are fit to the data. In the Very High State, the line profile is strongly redshifted and consistent with emission from the innermost radius of a maximally rotating Kerr black hole, 1.235 R(sub g). The line profile is less redshifted in the High State, but increasingly prominent. In the Low State, the line profile is very strong and centered af approx. 6.7 keV; disk line emission models constrain the inner edge of the disk to fluctuate between approx.20 and approx.59 R(sub g). We trace the disk reflection fraction across the full outburst of this source, and find well-constrained fractions below those observed in AGN in the Very High and High States, but consistent with other galactic sources in the Low State. We discuss the possible implications for black hole X-ray binary system dynamics and accretion flow geometry.

X-ray intensity and source size characterizations for the 25 kV upgraded Manson source at Sandia National Laboratories

NASA Astrophysics Data System (ADS)

Loisel, G.; Lake, P.; Gard, P.; Dunham, G.; Nielsen-Weber, L.; Wu, M.; Norris, E.

2016-11-01

At Sandia National Laboratories, the x-ray generator Manson source model 5 was upgraded from 10 to 25 kV. The purpose of the upgrade is to drive higher characteristics photon energies with higher throughput. In this work we present characterization studies for the source size and the x-ray intensity when varying the source voltage for a series of K-, L-, and M-shell lines emitted from Al, Y, and Au elements composing the anode. We used a 2-pinhole camera to measure the source size and an energy dispersive detector to monitor the spectral content and intensity of the x-ray source. As the voltage increases, the source size is significantly reduced and line intensity is increased for the three materials. We can take advantage of the smaller source size and higher source throughput to effectively calibrate the suite of Z Pulsed Power Facility crystal spectrometers.

New Constraints on the Geometry and Kinematics of Matter Surrounding the Accretion Flow in X-Ray Binaries from Chandra High-Energy Transmission Grating X-Ray Spectroscopy

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Yaqoob, T.

2018-01-01

The narrow, neutral Fe Ka fluorescence emission line in X-ray binaries (XRBs) is a powerful probe of the geometry, kinematics, and Fe abundance of matter around the accretion flow. In a recent study it has been claimed, using Chandra High-Energy Transmission Grating (HETG) spectra for a sample of XRBs, that the circumnuclear material is consistent with a solar-abundance, uniform, spherical distribution. It was also claimed that the Fe Ka line was unresolved in all cases by the HETG. However, these conclusions were based on ad hoc models that did not attempt to relate the global column density to the Fe Ka line emission. We revisit the sample and test a self-consistent model of a uniform, spherical X-ray reprocessor against HETG spectra from 56 observations of 14 Galactic XRBs. We find that the model is ruled out in 13/14 sources because a variable Fe abundance is required. In two sources a spherical distribution is viable, but with nonsolar Fe abundance. We also applied a solar-abundance Compton-thick reflection model, which can account for the spectra that are inconsistent with a spherical model, but spectra with a broader bandpass are required to better constrain model parameters. We also robustly measured the velocity width of the Fe Ka line and found FWHM values of up to approx. 5000 km/s. Only in some spectra was the Fe Ka line unresolved by the HETG.

C III spectra in WC Wolf-Rayet stars - Does collisional excitation dominate?

NASA Technical Reports Server (NTRS)

Kastner, S. O.; Bhatia, A. K.

1993-01-01

A direct comparison of the spectra emitted by an improved collisionally excited C III atomic model, with observations of C III spectra in Wolf-Rayet WC stars, shows agreement for UV, visible, and near-infrared lines including lines usually considered to be recombination lines. The agreement implies high-density and temperature source conditions corresponding to log (Ne Te) is greater than 16 as a lower limit, whereas most current modeling assumes log (Ne Te) is less than 15.5. This raises questions concerning the photoionization/recombination assumptions on which most WR modeling is based. Recent models are discussed from this point of view.

Evaluation of discrete frequency sound in closed-test-section wind tunnels

NASA Technical Reports Server (NTRS)

Mosher, Marianne

1990-01-01

The principal objective of this study is to assess the adequacy of linear acoustic theory with an impedance wall boundary condition for modeling the detailed sound field of an acoustic source in a duct. This study compares measurements and calculations of a simple acoustic source in a rectangular concrete duct lined with foam on the walls and anechoic end terminations. Measuring acoustic pressure for 12 wave numbers provides variation in frequency and absorption characteristics of the duct walls. The cases in this study contain low frequencies and low wall absorptions corresponding to measurements of low-frequency helicopter noise in a lined wind tunnel. This regime is particularly difficult to measure in wind tunnels due to high levels of the reverberant field relatively close to the source. Close to the source, where the interference of wall reflections is minimal, correlation is very good. Away from the source, correlation degrades, especially for the lower frequencies. Sensitivity studies show little effect on the predicted results for changes in impedance boundary condition values, source location, measurement location, temperature, and source model for variations spanning the expected measurement error.

R-LINE: A Line Source Dispersion Model for Near-Surface Releases

EPA Science Inventory

Based on Science Advisory Board and the National Research Councilrecommendations, EPA-ORD initiated research on near-road air quality andhealth effects. Field measurements indicated that exposures to traffic-emitted air pollutants near roads can be influenced by complexities of r...

"Dispersion modeling approaches for near road | Science ...

EPA Pesticide Factsheets

Roadway design and roadside barriers can have significant effects on the dispersion of traffic-generated pollutants, especially in the near-road environment. Dispersion models that can accurately simulate these effects are needed to fully assess these impacts for a variety of applications. For example, such models can be useful for evaluating the mitigation potential of roadside barriers in reducing near-road exposures and their associated adverse health effects. Two databases, a tracer field study and a wind tunnel study, provide measurements used in the development and/or validation of algorithms to simulate dispersion in the presence of noise barriers. The tracer field study was performed in Idaho Falls, ID, USA with a 6-m noise barrier and a finite line source in a variety of atmospheric conditions. The second study was performed in the meteorological wind tunnel at the US EPA and simulated line sources at different distances from a model noise barrier to capture the effect on emissions from individual lanes of traffic. In both cases, velocity and concentration measurements characterized the effect of the barrier on dispersion.This paper presents comparisons with the two datasets of the barrier algorithms implemented in two different dispersion models: US EPA’s R-LINE (a research dispersion modelling tool under development by the US EPA’s Office of Research and Development) and CERC’s ADMS model (ADMS-Urban). In R-LINE the physical features reveal

Immortalized N/TERT keratinocytes as an alternative cell source in 3D human epidermal models.

PubMed

Smits, Jos P H; Niehues, Hanna; Rikken, Gijs; van Vlijmen-Willems, Ivonne M J J; van de Zande, Guillaume W H J F; Zeeuwen, Patrick L J M; Schalkwijk, Joost; van den Bogaard, Ellen H

2017-09-19

The strong societal urge to reduce the use of experimental animals, and the biological differences between rodent and human skin, have led to the development of alternative models for healthy and diseased human skin. However, the limited availability of primary keratinocytes to generate such models hampers large-scale implementation of skin models in biomedical, toxicological, and pharmaceutical research. Immortalized cell lines may overcome these issues, however, few immortalized human keratinocyte cell lines are available and most do not form a fully stratified epithelium. In this study we compared two immortalized keratinocyte cell lines (N/TERT1, N/TERT2G) to human primary keratinocytes based on epidermal differentiation, response to inflammatory mediators, and the development of normal and inflammatory human epidermal equivalents (HEEs). Stratum corneum permeability, epidermal morphology, and expression of epidermal differentiation and host defence genes and proteins in N/TERT-HEE cultures was similar to that of primary human keratinocytes. We successfully generated N/TERT-HEEs with psoriasis or atopic dermatitis features and validated these models for drug-screening purposes. We conclude that the N/TERT keratinocyte cell lines are useful substitutes for primary human keratinocytes thereby providing a biologically relevant, unlimited cell source for in vitro studies on epidermal biology, inflammatory skin disease pathogenesis and therapeutics.

A brief compendium of correlations and analytical formulae for the thermal field generated by a heat source embedded in porous and purely-conductive media

NASA Astrophysics Data System (ADS)

Conti, P.; Testi, D.; Grassi, W.

2017-11-01

This work reviews and compares suitable models for the thermal analysis of forced convection over a heat source in a porous medium. The set of available models refers to an infinite medium in which a fluid moves over different three heat source geometries: i.e. the moving infinite line source, the moving finite line source, and the moving infinite cylindrical source. In this perspective, the present work presents a plain and handy compendium of the above-mentioned models for forced external convection in porous media; besides, we propose a dimensionless analysis to figure out the reciprocal deviation among available models, helping the selection of the most suitable one in the specific case of interest. Under specific conditions, the advection term becomes ineffective in terms of heat transfer performances, allowing the use of purely-conductive models. For that reason, available analytical and numerical solutions for purely-conductive media are also reviewed and compared, again, by dimensionless criteria. Therefore, one can choose the simplest solution, with significant benefits in terms of computational effort and interpretation of the results. The main outcomes presented in the paper are: the conditions under which the system can be considered subject to a Darcy flow, the minimal distance beyond which the finite dimension of the heat source does not affect the thermal field, and the critical fluid velocity needed to have a significant contribution of the advection term in the overall heat transfer process.

Airborne spectrophotometry of Eta Carinae from 4.5 to 7.5 microns and a model for source morphology

NASA Technical Reports Server (NTRS)

Russell, Ray W.; Lynch, David K.; Hackwell, John A.; Rudy, Richard J.; Rossano, George S.; Castelaz, M. W.

1987-01-01

Spectrophotometric observations of Eta Car between 4.5 and 7.5 microns show a featureless thermal-like spectrum with no fine-structure lines or broad emission or absorption features. The color temperature of the spectrum is approximately 375 K. High spatial resolution maps at 3.5, 4.8, and 10 microns obtained from the ground are used to discuss the dust distribution and temperature structure, and to present a model for general source morphology. The upper limit to the brightness of the forbidden Ar II fine-structure emission line at 6.98 microns is less than 7 x 10 to the -16th W/sq cm, which still allows for a significant overabundance of argon and is consistent with the evolved nature of the source.

Power Balance and Impurity Studies in TCS

NASA Astrophysics Data System (ADS)

Grossnickle, J. A.; Pietrzyk, Z. A.; Vlases, G. C.

2003-10-01

A "zero-dimension" power balance model was developed based on measurements of absorbed power, radiated power, absolute D_α, temperature, and density for the TCS device. Radiation was determined to be the dominant source of power loss for medium to high density plasmas. The total radiated power was strongly correlated with the Oxygen line radiation. This suggests Oxygen is the dominant radiating species, which was confirmed by doping studies. These also extrapolate to a Carbon content below 1.5%. Determining the source of the impurities is an important question that must be answered for the TCS upgrade. Preliminary indications are that the primary sources of Oxygen are the stainless steel end cones. A Ti gettering system is being installed to reduce this Oxygen source. A field line code has been developed for use in tracking where open field lines terminate on the walls. Output from this code is also used to generate grids for an impurity tracking code.

White Dwarf Model Atmospheres: Synthetic Spectra for Supersoft Sources

NASA Astrophysics Data System (ADS)

Rauch, Thomas

2013-01-01

The Tübingen NLTE Model-Atmosphere Package (TMAP) calculates fully metal-line blanketed white dwarf model atmospheres and spectral energy distributions (SEDs) at a high level of sophistication. Such SEDs are easily accessible via the German Astrophysical Virtual Observatory (GAVO) service TheoSSA. We discuss applications of TMAP models to (pre) white dwarfs during the hottest stages of their stellar evolution, e.g. in the parameter range of novae and supersoft sources.

Observations of Scorpius X-1 with IUE - Ultraviolet results from a multiwavelength campaign

NASA Technical Reports Server (NTRS)

Vrtilek, S. D.; Raymond, J. C.; Penninx, W.; Verbunt, F.; Hertz, P.

1991-01-01

IUE UV results are presented for the low-mass X-ray binary Sco X-1. Models that predict UV continuum emission from the X-ray-heated surface from the companion star and from an X-ray illuminated accretion disk are adjusted for parameters intrinsic to Sco X-1, and fitted to the data. X-ray heating is found to be the dominant source of UV emission; the mass-accretion rate increases monotonically along the 'Z-shaped' curve in an X-ray color-color diagram. UV emission lines from He, C, N, O, and Si were detected; they all increase in intensity from the HB to the FB state. A model in which emission lines are due to outer-disk photoionization by the X-ray source is noted to give good agreement with line fluxes observed in each state.

First Detections of the [N II] 122 micron Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

NASA Technical Reports Server (NTRS)

Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

2011-01-01

We report the first detections of the [N II] 122 micron line from a high-redshift galaxy. The line was strongly (>6(sigma)) detected from SMMJ02399-0136, and H1413 + 117 (the Cloverleaf QSO) using the Redshift (zeta) and Early Universe Spectrometer on the Caltech Submillimeter Observatory. The lines from both sources are quite bright with line to far-infrared (FIR) continuum luminosity ratios that are approx.7.0 x 10(exp -4) (Cloverleaf) and 2.1 x 10(exo -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line to continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8%-17% of the molecUlar gas mass. The [O III]/[N II] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an active galactic nucleus (AGN). Using Our previous detection of the [O III] 88 micron line, the [O III]/[N II]line ratio for SMMJ02399-0136 indicates that the dominant source of the line emission is either stellar H II regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = -3.3 to -4.0. A composite system, where 30%-50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82-like starbursts accounting for all of the FIR emission and 43% of the [N II]line. The remainder may come from the NLR. This war!< demonstrates the utility of the [N II] and [O III] lines in constraining properties of the ionized medium.

Copper content in lake sediments as a tracer of urban emissions: evaluation through a source-transport-storage model.

PubMed

Cui, Qing; Brandt, Nils; Sinha, Rajib; Malmström, Maria E

2010-06-01

A coupled source-transport-storage model was developed to determine the origin and path of copper from materials/goods in use in the urban drainage area and the fate of copper in local recipient lakes. The model was applied and tested using five small lakes in Stockholm, Sweden. In the case of the polluted lakes Råcksta Träsk, Trekanten and Långsjön, the source strengths of copper identified by the model were found to be well linked with independently observed copper contents in the lake sediments through the model. The model results also showed that traffic emissions, especially from brake linings, dominated the total load in all five cases. Sequential sedimentation and burial proved to be the most important fate processes of copper in all lakes, except Råcksta Träsk, where outflow dominated. The model indicated that the sediment copper content can be used as a tracer of the urban diffuse copper source strength, but that the response to changes in source strength is fairly slow (decades). Major uncertainties in the source model were related to management of stormwater in the urban area, the rate of wear of brake linings and weathering of copper roofs. The uncertainty of the coupled model is in addition affected mainly by parameters quantifying the sedimentation and bury processes, such as particulate fraction, settling velocity of particles, and sedimentation rate. As a demonstration example, we used the model to predict the response of the sediment copper level to a decrease in the copper load from the urban catchment in one of the case study lakes. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Mathematical Constraints on the Use of Transmission Line Models for Simulating Initial Breakdown Pulses in Lightning Discharges

NASA Astrophysics Data System (ADS)

da Silva, C. L.; Merrill, R. A.; Pasko, V. P.

2015-12-01

A significant portion of the in-cloud lightning development is observed as a series of initial breakdown pulses (IBPs) that are characterized by an abrupt change in the electric field at a remote sensor. Recent experimental and theoretical studies have attributed this process to the stepwise elongation of an initial lightning leader inside the thunderstorm [da Silva and Pasko, JGR, 120, 4989-5009, 2015, and references therein]. Attempts to visually observe these events are hampered due to the fact that clouds are opaque to optical radiation. Due to this reason, throughout the last decade, a number of researchers have used the so-called transmission line models (also commonly referred to as engineering models), widely employed for return stroke simulations, to simulate the waveshapes of IBPs, and also of narrow bipolar events. The transmission line (TL) model approach is to prescribe the source current dynamics in a certain manner to match the measured E-field change waveform, with the purpose of retrieving key information about the source, such as its height, peak current, size, speed of charge motion, etc. Although the TL matching method is not necessarily physics-driven, the estimated source characteristics can give insights on the dominant length- and time-scales, as well as, on the energetics of the source. This contributes to better understanding of the environment where the onset and early stages of lightning development takes place.In the present work, we use numerical modeling to constrain the number of source parameters that can be confidently inferred from the observed far-field IBP waveforms. We compare different modified TL models (i.e., with different attenuation behaviors) to show that they tend to produce similar waveforms in conditions where the channel is short. We also demonstrate that it is impossible to simultaneously retrieve the speed of source current propagation and channel length from an observed IBP waveform, in contrast to what has been previously done in the literature. Finally, we demonstrate that the simulated field-to-current conversion factor in IBP sources can vary by more than one order of magnitude, making peak current estimates for intracloud lightning processes a challenging task.

Improved alternating gradient transport and focusing of neutral molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalnins, Juris; Lambertson, Glen; Gould, Harvey

2001-12-02

Polar molecules, in strong-field seeking states, can be transported and focused by an alternating sequence of electric field gradients that focus in one transverse direction while defocusing in the other. We show by calculation and numerical simulation, how one may greatly improve the alternating gradient transport and focusing of molecules. We use a new optimized multipole lens design, a FODO lattice beam transport line, and lenses to match the beam transport line to the beam source and the final focus. We derive analytic expressions for the potentials, fields, and gradients that may be used to design these lenses. We describemore » a simple lens optimization procedure and derive the equations of motion for tracking molecules through a beam transport line. As an example, we model a straight beamline that transports a 560 m/s jet-source beam of methyl fluoride molecules 15 m from its source and focuses it to 2 mm diameter. We calculate the beam transport line acceptance and transmission, for a beam with velocity spread, and estimate the transmitted intensity for specified source conditions. Possible applications are discussed.« less

Targeted versus statistical approaches to selecting parameters for modelling sediment provenance

NASA Astrophysics Data System (ADS)

Laceby, J. Patrick

2017-04-01

One effective field-based approach to modelling sediment provenance is the source fingerprinting technique. Arguably, one of the most important steps for this approach is selecting the appropriate suite of parameters or fingerprints used to model source contributions. Accordingly, approaches to selecting parameters for sediment source fingerprinting will be reviewed. Thereafter, opportunities and limitations of these approaches and some future research directions will be presented. For properties to be effective tracers of sediment, they must discriminate between sources whilst behaving conservatively. Conservative behavior is characterized by constancy in sediment properties, where the properties of sediment sources remain constant, or at the very least, any variation in these properties should occur in a predictable and measurable way. Therefore, properties selected for sediment source fingerprinting should remain constant through sediment detachment, transportation and deposition processes, or vary in a predictable and measurable way. One approach to select conservative properties for sediment source fingerprinting is to identify targeted tracers, such as caesium-137, that provide specific source information (e.g. surface versus subsurface origins). A second approach is to use statistical tests to select an optimal suite of conservative properties capable of modelling sediment provenance. In general, statistical approaches use a combination of a discrimination (e.g. Kruskal Wallis H-test, Mann-Whitney U-test) and parameter selection statistics (e.g. Discriminant Function Analysis or Principle Component Analysis). The challenge is that modelling sediment provenance is often not straightforward and there is increasing debate in the literature surrounding the most appropriate approach to selecting elements for modelling. Moving forward, it would be beneficial if researchers test their results with multiple modelling approaches, artificial mixtures, and multiple lines of evidence to provide secondary support to their initial modelling results. Indeed, element selection can greatly impact modelling results and having multiple lines of evidence will help provide confidence when modelling sediment provenance.

Effects of Kerr space-time on spectral features from X-ray illuminated accretion discs

NASA Astrophysics Data System (ADS)

Martocchia, A.; Karas, V.; Matt, G.

2000-03-01

We performed detailed calculations of the relativistic effects acting on both the reflection continuum and the iron line from accretion discs around rotating black holes. Fully relativistic transfer of both illuminating and reprocessed photons has been considered in Kerr space-time. We calculated overall spectra, line profiles and integral quantities, and present their dependences on the black hole angular momentum. We show that the observed EW of the lines is substantially enlarged when the black hole rotates rapidly and/or the source of illumination is near above the hole. Therefore, such calculations provide a way to distinguish between different models of the central source.

service line analytics in the new era.

PubMed

Spence, Jay; Seargeant, Dan

2015-08-01

To succeed under the value-based business model, hospitals and health systems require effective service line analytics that combine inpatient and outpatient data and that incorporate quality metrics for evaluating clinical operations. When developing a framework for collection, analysis, and dissemination of service line data, healthcare organizations should focus on five key aspects of effective service line analytics: Updated service line definitions. Ability to analyze and trend service line net patient revenues by payment source. Access to accurate service line cost information across multiple dimensions with drill-through capabilities. Ability to redesign key reports based on changing requirements. Clear assignment of accountability.

Conical Current Sheets in a Source-Surface Model of the Heliosphere

NASA Astrophysics Data System (ADS)

Schulz, M.

2007-12-01

Different methods of modeling the coronal and heliospheric magnetic field are conveniently visualized and intercompared by applying them to ideally axisymmetric field models. Thus, for example, a dipolar B field with its moment parallel to the Sun's rotation axis leads to a flat heliospheric current sheet. More general solar B fields (still axisymmetric about the solar rotation axis for simplicity) typically lead to cone-shaped current sheets beyond the source surface (and presumably also in MHD models). As in the dipolar case [Schulz et al., Solar Phys., 60, 83-104, 1978], such conical current sheets can be made realistically thin by taking the source surface to be non-spherical in a way that reflects the underlying structure of the Sun's main B field. A source surface that seems to work well in this respect [Schulz, Ann. Geophysicae, 15, 1379-1387, 1997] is a surface of constant F = (1/r)kB, where B is the scalar strength of the Sun's main magnetic field and k (~ 1.4) is a shape parameter. This construction tends to flatten the source surface in regions where B is relatively weak. Thus, for example, the source surface for a dipolar B field is shaped somewhat like a Rugby football, whereas the source surface for an axisymmetric quadrupolar B field is similarly elongated but somewhat flattened (as if stuffed into a cone) at mid-latitudes. A linear combination of co-axial dipolar and quadrupolar B fields generates a somewhat pear-shaped (but still convex) source surface. If the region surrounded by the source surface is regarded as current-free, then the source surface itself should be (as nearly as possible) an equipotential surface for the corresponding magnetic scalar potential (expanded, for example, in spherical harmonics). The solar wind should then flow not quite radially, but rather in a straight line along the outward normal to the source surface, and the heliospheric B field should follow a corresponding generalization of Parker's spiral [Levine et al., Solar Phys., 77, 363-392, 1982]. In particular, heliospheric current sheets (of which there are two if the underlying solar B field is mainly quadrupolar) should emanate from neutral lines on the corresponding source surface. However, because the source surface is relatively flattened in regions where such neutral lines tend to appear, the radial component of the heliospheric B field at r ~} 1 AU and beyond is much more nearly latitude-independent in absolute value than one would expect from models based on a spherical source surface.

New Constraints on the Geometry and Kinematics of Matter Surrounding the Accretion Flow in X-Ray Binaries from Chandra High-energy Transmission Grating X-Ray Spectroscopy

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Yaqoob, T.

2018-03-01

The narrow, neutral Fe Kα fluorescence emission line in X-ray binaries (XRBs) is a powerful probe of the geometry, kinematics, and Fe abundance of matter around the accretion flow. In a recent study it has been claimed, using Chandra High-Energy Transmission Grating (HETG) spectra for a sample of XRBs, that the circumnuclear material is consistent with a solar-abundance, uniform, spherical distribution. It was also claimed that the Fe Kα line was unresolved in all cases by the HETG. However, these conclusions were based on ad hoc models that did not attempt to relate the global column density to the Fe Kα line emission. We revisit the sample and test a self-consistent model of a uniform, spherical X-ray reprocessor against HETG spectra from 56 observations of 14 Galactic XRBs. We find that the model is ruled out in 13/14 sources because a variable Fe abundance is required. In two sources a spherical distribution is viable, but with nonsolar Fe abundance. We also applied a solar-abundance Compton-thick reflection model, which can account for the spectra that are inconsistent with a spherical model, but spectra with a broader bandpass are required to better constrain model parameters. We also robustly measured the velocity width of the Fe Kα line and found FWHM values of up to ∼5000 km s‑1. Only in some spectra was the Fe Kα line unresolved by the HETG.

Proceedings from the Workshop on Research Needs for Assessment and Management of Non-Point Air Emissions from Department of Defense Activities held in Research Triangle Park, North Carolina on 19-21 February 2008

DTIC Science & Technology

2008-10-01

Chow, J.C. (2006). Feasibility of soil dust source apportionment by the pyrolysis-gas chromatography/mass spectrometry method. J. Air Waste Manage...receptor-oriented source apportionment models. • Develop monitoring methods to determine source and fence line amounts of fugitive dust emissions for...offsite impact, including evaluation with receptor- oriented source apportionment models 76 8.8.1 Background 76 8.8.2 Significance 77 8.8.3

The Variable Warm Absorber in Circinus X-1

NASA Astrophysics Data System (ADS)

Schulz, N. S.; Kallman, T. E.; Galloway, D. K.; Brandt, W. N.

2008-01-01

We observed Circinus X-1 twice during a newly reached low-flux phase near zero orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS) onboard Chandra. In both observations the source did not show the P Cygni lines we observed during the high-flux phases of the source in 2000 and 2001. During the prezero phase the source did not exhibit significant variability but did exhibit an emission-line spectrum rich in H- and He-like lines from high-Z elements such as Si, S, Ar, and Ca. The light curve in the postdip observation showed quiescent and flaring episodes. Only in these flaring episodes was the source luminosity significantly higher than observed during the prezero phase. We analyzed all high-resolution X-ray spectra by fitting photoionization and absorption models from the most recent version of the XSTAR code. The prezero-phase spectrum could be fully modeled with a very hot photoionized plasma with an ionization parameter of log ξ = 3.0, down from log ξ = 4.0 in the high-flux state. The ionization balances we measure from the spectra during the postzero-phase episodes are significantly different. Both episodes feature absorbers with variable high columns, ionization parameters, and luminosity. While cold absorption remains at levels quite similar to that observed in previous years, the new observations show unprecedented levels of variable warm absorption. The line emissivities also indicate that the observed low source luminosity is inconsistent with a static hot accretion disk corona (ADC), an effect that seems common to other near-edge-on ADC sources as well. We conclude that unless there exists some means of coronal heating other than X-rays, the true source luminosity is likely much higher, and we observe obscuration in analogy to the extragalactic Seyfert 2 sources. We discuss possible consequences and relate cold, lukewarm, warm, and hot absorbers to dynamic accretion scenarios.

Evidence for a Broad Relativistic Iron Line from the Neutron Star LMXB Ser X-1

NASA Technical Reports Server (NTRS)

Bhattacharyya, Sudip; Strohmayer, Tod E.

2007-01-01

We report on an analysis of XMM-Newton data from the neutron star low mass X-ray binary (LMXB) Serpens X-1 (Ser X-1). Spectral analysis of EPIC PN data indicates that the previously known broad iron Ka emission line in this source has a significantly skewed structure with a moderately extended red wing. The asymmetric shape of the line is well described with the laor and diskline models in XSPEC, which strongly supports an inner accretion disk origin of the line. To our knowledge this is the first strong evidence for a relativistic line in a neutron star LMXB. This finding suggests that the broad lines seen in other neutron star LMXBs likely originate from the inner disk as well. Detailed study of such lines opens up a new way to probe neutron star parameters and their strong gravitational fields. The laor model describes the line from Ser X-1 somewhat better than diskline, and suggests that the inner accretion disk radius is less than 6GM/c(exp 2). This is consistent with the weak magnetic fields of LMXBs, and may point towards a high compactness and rapid spin of the neutron star. Finally, the inferred source inclination angle in the approximate range 50-60 deg is consistent with the lack of dipping from Ser X-1.

The nature of the [O III] emission line system in the black hole hosting globular cluster RZ2109

NASA Astrophysics Data System (ADS)

Steele, Matthew M.

This work, focused on the description and understanding of the nature of a [O III] emission line source associated with an accreting stellar mass black hole in a globlar cluster, is comprised of three papers. In the first paper, we present a multi-facility study of the optical spectrum of the extra- galactic globular cluster RZ2109, which hosts a bright black hole X-ray source. The optical spectrum of RZ2109 shows strong and very broad [O III]lambdalambda4959,5007 emission in addition to the stellar absorption lines typical of a globular cluster. We use observations over an extended period of time to constrain the variability of these [O III] emission lines. We find that the equivalent width of the lines is similar in all of the datasets; the change in L[O III]lambda5007 is ≤ 10% between the first and last observations, which were separated by 467 days. The velocity profile of the line also shows no significant variability over this interval. Using a simple geometric model we demonstrate that the observed [O III]lambda5007 line velocity structure can be described by a two component model with most of the flux contributed by a bipolar conical outflow of about 1,600 km s -1 , and the remainder from a Gaussian component with a FWHM of several hundred km s-1 . In the second paper, we present an analysis of the elemental composition of the emission line system associated with the black hole hosting globular cluster RZ2109 located in NGC4472. From medium resolution GMOS optical spectroscopy we find a [O III]lambda5007/Hbeta emission line ratio of 106 for a 3200 km s-1 measurement aperture covering the full velocity width of the [O III]lambda5007 line, with a 95% confidence level lower and upper limits of [O III]lambda5007/Hbeta > 35.7 and < -110 (Hbeta absorption). For a narrower 600 km s-1 aperture covering the highest luminosity velocity structure in the line complex, we find [O III]lambda5007/Hbeta = 62, with corresponding 95% confidence lower and upper limits of > 30.2 and < -364. The measured [O III]lambda5007/Hbeta ratios are significantly higher than can be produced in radiative models of the emission line region with solar composition, and the confidence interval limits exclude all but the most extremely massive models. Therefore, we conclude that the region from which the [O III]lambda5007 emission originates must be hydrogen depleted relative to solar composition gas. This finding is consistent with emission from an accretion powered outflow driven by a hydrogen depleted donor star, such as a white dwarf, being accreted onto a black hole. In the third paper, we examine the variability of the [O III]lambdalambda4959,5007 emission line source in the NGC 4472 black hole hosting globular cluster RZ2109. Our continuing multi-facility monitoring program finds the strong emission line source had decreased 24+/-2 percent from the 2007-2010 mean levels in 2011 and 40+/-5 percent from the earlier mean in 2012. An analysis of the variability of the emission line velocity profile finds that the flux ratio of higher velocity 1600 km s-1 component to the lower velocity 300 km s-1 component has decreased 30 percent from 2009 to 2011, and the asymmetry between the red and blue wings of the profile has decreased 17 percent. We compare this variability to predictions of photoionized nova ejecta models of the emission line region, and discuss its implications for an accretion powered outflow from a CO WD-BH binary model.

Atoms in carbon cages as a source of interstellar diffuse lines

NASA Technical Reports Server (NTRS)

Ballester, J. L.; Antoniewicz, P. R.; Smoluchowski, R.

1990-01-01

A model to describe the resonance absorption lines of various atoms trapped in closed carbon cages is presented. These systems may be responsible for some of the as yet unexplained diffuse interstellar bands. Model potentials for possible atom-C60 systems are obtained and used to calculate the resonance lines. The trapped atoms considered are O, N, Si, Mg, Al, Na, and S, and in all cases the resonance lines are shifted toward the red as compared to the isolated atoms. The calculated wavelengths are compared to the range of wavelengths observed for the diffuse interstellar bands, and good agreement is found for Mg and Si resonance lines. Other lines may be caused by other than resonance transitions or by trapped molecules. The oscillator strengths and the abundances are evaluated and compared with observation. Mechanisms to explain the observed band width of the lines and the existence of certain correlated pairs of lines are discussed.

Balmer line profiles for infalling T Tauri envelopes

NASA Technical Reports Server (NTRS)

Calvet, Nuria; Hartmann, Lee

1992-01-01

The possibility that the Balmer emission lines of T Tauri stars arise in infalling envelopes rather than winds is considered. Line profiles for the upper Balmer lines are presented for models with cone geometry, intended to simulate the basic features of magnetospheric accretion from a circumstellar disk. An escape probability treatment is used to determine line source functions in nonspherically symmetric geometry. Thermalization effects are found to produce nearly symmetric H-alpha line profiles at the same time the higher Balmer series lines exhibit inverse P Cygni profiles. The infall models produce centrally peaked emission line wings, in good agreement with observations of many T Tauri stars. It is suggested that the Balmer emission of many T Tauri stars may be produced in an infalling envelope, with blue shifted absorption contributed by an overlying wind. Some of the observed narrow absorption components with small blueshifts may also arise in the accretion column.

Next Generation Emission Measurements for Fugitive, Area Source, and Fence Line Applications?

EPA Science Inventory

Next generation emissions measurements (NGEM) is an EPA term for the rapidly advancing field of air pollutant sensor technologies, data integration concepts, and associated geospatial modeling strategies for source emissions measurements. Ranging from low coat sensors to satelli...

Linear Power-Flow Models in Multiphase Distribution Networks: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernstein, Andrey; Dall'Anese, Emiliano

This paper considers multiphase unbalanced distribution systems and develops approximate power-flow models where bus-voltages, line-currents, and powers at the point of common coupling are linearly related to the nodal net power injections. The linearization approach is grounded on a fixed-point interpretation of the AC power-flow equations, and it is applicable to distribution systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. The proposed linear models can facilitate the development of computationally-affordable optimization and control applications -- frommore » advanced distribution management systems settings to online and distributed optimization routines. Performance of the proposed models is evaluated on different test feeders.« less

X-ray intensity and source size characterizations for the 25 kV upgraded Manson source at Sandia National Laboratories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loisel, G., E-mail: gploise@sandia.gov; Lake, P.; Gard, P.

2016-11-15

At Sandia National Laboratories, the x-ray generator Manson source model 5 was upgraded from 10 to 25 kV. The purpose of the upgrade is to drive higher characteristics photon energies with higher throughput. In this work we present characterization studies for the source size and the x-ray intensity when varying the source voltage for a series of K-, L-, and M-shell lines emitted from Al, Y, and Au elements composing the anode. We used a 2-pinhole camera to measure the source size and an energy dispersive detector to monitor the spectral content and intensity of the x-ray source. As themore » voltage increases, the source size is significantly reduced and line intensity is increased for the three materials. We can take advantage of the smaller source size and higher source throughput to effectively calibrate the suite of Z Pulsed Power Facility crystal spectrometers.« less

On the Nature of Orion Source I

NASA Astrophysics Data System (ADS)

Báez-Rubio, A.; Jiménez-Serra, I.; Martín-Pintado, J.; Zhang, Q.; Curiel, S.

2018-01-01

The Kleinmann–Low nebula in Orion, the closest region of massive star formation, harbors Source I, whose nature is under debate. Knowledge of this source may have profound implications for our understanding of the energetics of the hot core in Orion KL since it might be the main heating source in the region. The spectral energy distribution of this source in the radio is characterized by a positive spectral index close to 2, which is consistent with (i) thermal bremsstrahlung emission of ionized hydrogen gas produced by a central massive protostar, or (ii) photospheric bremsstrahlung emission produced by electrons when deflected by the interaction with neutral and molecular hydrogen like Mira-like variable stars. If ionized hydrogen gas were responsible for the observed continuum emission, its modeling would predict detectable emission from hydrogen radio recombination lines (RRLs). However, our SMA observations were obtained with a high enough sensitivity to rule out that the radio continuum emission arises from a dense hypercompact H II region because the H26α line would have been detected, in contrast with our observations. To explain the observational constraints, we investigate further the nature of the radio continuum emission from source I. We have compared available radio continuum data with the predictions from our upgraded non-LTE 3D radiative transfer model, MOdel for REcombination LInes, to show that radio continuum fluxes and sizes can only be reproduced by assuming both dust and bremsstrahlung emission from neutral gas. The dust emission contribution is significant at ν ≥ 43 GHz. In addition, our RRL peak intensity predictions for the ionized metals case are consistent with the nondetection of Na and K RRLs at millimeter and submillimeter wavelengths.

Modeling the mesozoic-cenozoic structural evolution of east texas

USGS Publications Warehouse

Pearson, Ofori N.; Rowan, Elisabeth L.; Miller, John J.

2012-01-01

The U.S. Geological Survey (USGS) recently assessed the undiscovered technically recoverable oil and gas resources within Jurassic and Cretaceous strata of the onshore coastal plain and State waters of the U.S. Gulf Coast. Regional 2D seismic lines for key parts of the Gulf Coast basin were interpreted in order to examine the evolution of structural traps and the burial history of petroleum source rocks. Interpretation and structural modeling of seismic lines from eastern Texas provide insights into the structural evolution of this part of the Gulf of Mexico basin. Since completing the assessment, the USGS has acquired additional regional seismic lines in east Texas; interpretation of these new lines, which extend from the Texas-Oklahoma state line to the Gulf Coast shoreline, show how some of the region's prominent structural elements (e.g., the Talco and Mount Enterprise fault zones, the East Texas salt basin, and the Houston diapir province) vary along strike. The interpretations also indicate that unexplored structures may lie beneath the current drilling floor. Structural restorations based upon interpretation of these lines illustrate the evolution of key structures and show the genetic relation between structural growth and movement of the Jurassic Louann Salt. 1D thermal models that integrate kinetics and burial histories were also created for the region's two primary petroleum source rocks, the Oxfordian Smackover Formation and the Cenomanian-Turonian Eagle Ford Shale. Integrating results from the thermal models with the structural restorations provides insights into the distribution and timing of petroleum expulsion from the Smackover Formation and Eagle Ford Shale in eastern Texas.

Detecting Weak Spectral Lines in Interferometric Data through Matched Filtering

NASA Astrophysics Data System (ADS)

Loomis, Ryan A.; Öberg, Karin I.; Andrews, Sean M.; Walsh, Catherine; Czekala, Ian; Huang, Jane; Rosenfeld, Katherine A.

2018-04-01

Modern radio interferometers enable observations of spectral lines with unprecedented spatial resolution and sensitivity. In spite of these technical advances, many lines of interest are still at best weakly detected and therefore necessitate detection and analysis techniques specialized for the low signal-to-noise ratio (S/N) regime. Matched filters can leverage knowledge of the source structure and kinematics to increase sensitivity of spectral line observations. Application of the filter in the native Fourier domain improves S/N while simultaneously avoiding the computational cost and ambiguities associated with imaging, making matched filtering a fast and robust method for weak spectral line detection. We demonstrate how an approximate matched filter can be constructed from a previously observed line or from a model of the source, and we show how this filter can be used to robustly infer a detection significance for weak spectral lines. When applied to ALMA Cycle 2 observations of CH3OH in the protoplanetary disk around TW Hya, the technique yields a ≈53% S/N boost over aperture-based spectral extraction methods, and we show that an even higher boost will be achieved for observations at higher spatial resolution. A Python-based open-source implementation of this technique is available under the MIT license at http://github.com/AstroChem/VISIBLE.

Detection of a new extended soft X-ray source H1538-32 - A possible old supernova remnant

NASA Technical Reports Server (NTRS)

Riegler, G. R.; Agrawal, P. C.; Gull, S. F.

1980-01-01

The discovery in the Lupus region of a new, extended soft X-ray source, H1538-32, is reported, having a distance of approximately 340 pc, and a luminosity of 1 to 2 x 10 to the 34th ergs/sec. The observed energy spectrum of the source is well fitted either by a thermal bremsstrahlung spectrum with Gaunt factor but without line emission, or by a coronal plasma model which includes the X-ray emission lines of various elements and the continuum as outlined by Raymond and Smith (1977). On the basis of the extended nature of the source and its thermal spectrum, it is suggested that H1538-32 may be an old supernova remnant.

X-shooter spectroscopy of young stellar objects. VI. H I line decrements

NASA Astrophysics Data System (ADS)

Antoniucci, S.; Nisini, B.; Giannini, T.; Rigliaco, E.; Alcalá, J. M.; Natta, A.; Stelzer, B.

2017-03-01

Context. Hydrogen recombination emission lines commonly observed in accreting young stellar objects represent a powerful tracer for the gas conditions in the circumstellar structures (accretion columns, and winds or jets). Aims: Here we perform a study of the H I decrements and line profiles, from the Balmer and Paschen H I lines detected in the X-shooter spectra of a homogeneous sample of 36 T Tauri objects in Lupus, the accretion and stellar properties of which were already derived in a previous work. We aim to obtain information on the H I gas physical conditions to delineate a consistent picture of the H I emission mechanisms in pre-main sequence low-mass stars (M∗< 2 M⊙). Methods: We have empirically classified the sources based on their H I line profiles and decrements. We identified four Balmer decrement types (which we classified as 1, 2, 3, and 4) and three Paschen decrement types (A, B, and C), characterised by different shapes. We first discussed the connection between the decrement types and the source properties and then compared the observed decrements with predictions from recently published local line excitation models. Results: We identify a few groups of sources that display similar H I properties. One third of the objects show lines with narrow symmetric profiles, and present similar Balmer and Paschen decrements (straight decrements, types 2 and A). Lines in these sources are consistent with optically thin emission from gas with hydrogen densities of order 109 cm-3 and 5000 < T < 15 000 K. These objects are associated with low mass accretion rates. Type 4 (L-shaped) Balmer and type B Paschen decrements are found in conjunction with very wide line profiles and are characteristic of strong accretors, with optically thick emission from high-density gas (log nH > 11 cm-3). Type 1 (curved) Balmer decrements are observed only in three sub-luminous sources viewed edge-on, so we speculate that these are actually type 2 decrements that are reddened because of neglecting a residual amount of extinction in the line emission region. About 20% of the objects present type 3 Balmer decrements (bumpy), which, however, cannot be reproduced with current models. Based on observations collected at the European Southern Observatory at Paranal, Chile, under programmes 084.C-0269(A), 085.C-238(A), 086.C-0173(A), 087.C-0244(A), and 089.C-0143(A).

“RLINE: A Line Source Dispersion Model for Near-Surface Releases”

EPA Science Inventory

Growing concern about human exposure and related adverse health effects near roadways initiated an effort by the U. S. Environmental Protection Agency to reexamine the dispersion of mobile source related pollutants. These adverse effects, in combination with the fact that a signi...

A Gemini view of the galaxy cluster RXC J1504-0248: insights on the nature of the central gaseous filaments

NASA Astrophysics Data System (ADS)

Soja, A. C.; Sodré, L.; Monteiro-Oliveira, R.; Cypriano, E. S.; Lima Neto, G. B.

2018-07-01

We revisit the galaxy cluster RXC J1504-0248, a remarkable example of a structure with a strong cool core in a near redshift (z = 0.216). We performed a combined analysis using photometric and spectroscopic data obtained at Gemini South Telescope. We estimated the cluster mass through gravitational lensing, obtaining M200 = 5.3 ± 0.4 × 1014 h_{70}^{-1} M⊙ within R200 = 1.56 ± 0.04 h^{-1}_{70} Mpc, in agreement with a virial mass estimate. This cluster presents a prominent filamentary structure associated with its brightest cluster galaxy, located mainly along its major axis and aligned with the X-ray emission. A combined study of three emission line diagnostic diagrams has shown that the filament emission falls in the so-called transition region of these diagrams. Consequently, several ionizing sources should be playing a meaningful role. We have argued that old stars, often invoked to explain low-ionization nuclear emission-line region emission, should not be the major source of ionization. We have noticed that most of the filamentary emission has line ratios consistent with the shock excitation limits obtained from shock models. We also found that line fluxes are related to gas velocities (here estimated from line widths) by power laws with slopes in the range expected from shock models. These models also show, however, that only ˜10 per cent of H α luminosity can be explained by shocks. We conclude that shocks probably associated with the cooling of the intracluster gas in a filamentary structure may indeed be contributing to the filament nebular emission, but cannot be the major source of ionizing photons.

Numerical demonstration of surfactant concentration-dependent capillarity and viscosity effects on infiltration from a constant flux line source

NASA Astrophysics Data System (ADS)

Henry, Eric J.; Smith, James E.

2006-09-01

SummarySurface infiltration line sources can deliver surfactant solutions for agricultural purposes or for use in subsurface remediation. Though the prediction of water distribution below a line source has received considerable attention in the scientific literature, little has been has been reported on how infiltration of surfactant solution from a line source differs from water infiltration. Few numerical models are capable of simulating surfactant-induced changes in moisture characteristic and hydraulic conductivity properties of unsaturated soil, so it is difficult to assess the importance of these effects when designing surfactant application schemes. We investigated surfactant infiltration behavior by using the variably-saturated flow and transport model HYDRUS-2D [Simunek, J., Sejna, M., van Genuchten, M.Th., 1999. The HYDRUS-2D software package for simulating the two-dimensional movement of water, heat, and multiple solutes in variably-saturated media, Version 2.0. IGWMC-TPS-53C. International Ground Water Modeling Center, Colorado School of Mines, Golden, CO] which was modified by [Henry, E.J., Smith, J.E., Warrick, A.W., 2002. Two-dimensional modeling of flow and transport in the vadose zone with surfactant-induced flow. Water Resour. Res. 38. DOI: doi:10.1029/2001WR000674] to incorporate surfactant effects on unsaturated flow. Significant differences were found between pure water and surfactant solution infiltration into a fine sand that was initially at residual moisture content. The surfactant solution wetted a larger area, both horizontally and vertically, relative to water, while the distribution of water within the wetted zone was more uniform than in the surfactant system. The surfactant system exhibited transient localized drainage and rewetting caused by surfactant-induced capillary pressure gradients within the wetting front. A standard unsaturated flow model (i.e., one that does not include surfactant effects on flow) is not capable of capturing the transient flow behavior. However, our results show that by using an effective scaled media (ESM) approach a standard model can be used to simulate later-time hydraulic conditions in a surfactant system.

Dusty starburst galaxies in the early Universe as revealed by gravitational lensing.

PubMed

Vieira, J D; Marrone, D P; Chapman, S C; De Breuck, C; Hezaveh, Y D; Weiβ, A; Aguirre, J E; Aird, K A; Aravena, M; Ashby, M L N; Bayliss, M; Benson, B A; Biggs, A D; Bleem, L E; Bock, J J; Bothwell, M; Bradford, C M; Brodwin, M; Carlstrom, J E; Chang, C L; Crawford, T M; Crites, A T; de Haan, T; Dobbs, M A; Fomalont, E B; Fassnacht, C D; George, E M; Gladders, M D; Gonzalez, A H; Greve, T R; Gullberg, B; Halverson, N W; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Hunter, T R; Keisler, R; Lee, A T; Leitch, E M; Lueker, M; Luong-Van, D; Malkan, M; McIntyre, V; McMahon, J J; Mehl, J; Menten, K M; Meyer, S S; Mocanu, L M; Murphy, E J; Natoli, T; Padin, S; Plagge, T; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Sharon, K; Schaffer, K K; Shaw, L; Shirokoff, E; Spilker, J S; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Vanderlinde, K; Welikala, N; Williamson, R

2013-03-21

In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.

A Seismic Source Model for Central Europe and Italy

NASA Astrophysics Data System (ADS)

Nyst, M.; Williams, C.; Onur, T.

2006-12-01

We present a seismic source model for Central Europe (Belgium, Germany, Switzerland, and Austria) and Italy, as part of an overall seismic risk and loss modeling project for this region. A separate presentation at this conference discusses the probabilistic seismic hazard and risk assessment (Williams et al., 2006). Where available we adopt regional consensus models and adjusts these to fit our format, otherwise we develop our own model. Our seismic source model covers the whole region under consideration and consists of the following components: 1. A subduction zone environment in Calabria, SE Italy, with interface events between the Eurasian and African plates and intraslab events within the subducting slab. The subduction zone interface is parameterized as a set of dipping area sources that follow the geometry of the surface of the subducting plate, whereas intraslab events are modeled as plane sources at depth; 2. The main normal faults in the upper crust along the Apennines mountain range, in Calabria and Central Italy. Dipping faults and (sub-) vertical faults are parameterized as dipping plane and line sources, respectively; 3. The Upper and Lower Rhine Graben regime that runs from northern Italy into eastern Belgium, parameterized as a combination of dipping plane and line sources, and finally 4. Background seismicity, parameterized as area sources. The fault model is based on slip rates using characteristic recurrence. The modeling of background and subduction zone seismicity is based on a compilation of several national and regional historic seismic catalogs using a Gutenberg-Richter recurrence model. Merging the catalogs encompasses the deletion of double, fake and very old events and the application of a declustering algorithm (Reasenberg, 2000). The resulting catalog contains a little over 6000 events, has an average b-value of -0.9, is complete for moment magnitudes 4.5 and larger, and is used to compute a gridded a-value model (smoothed historical seismicity) for the region. The logic tree weighs various completeness intervals and minimum magnitudes. Using a weighted scheme of European and global ground motion models together with a detailed site classification map for Europe based on Eurocode 8, we generate hazard maps for recurrence periods of 200, 475, 1000 and 2500 yrs.

New observations and models of circumstellar CO line emission of AGB stars in the Herschel SUCCESS programme

NASA Astrophysics Data System (ADS)

Danilovich, T.; Teyssier, D.; Justtanont, K.; Olofsson, H.; Cerrigone, L.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Castro-Carrizo, A.; García-Lario, P.; Marston, A.

2015-09-01

Context. Asymptotic giant branch (AGB) stars are in one of the latest evolutionary stages of low to intermediate-mass stars. Their vigorous mass loss has a significant effect on the stellar evolution, and is a significant source of heavy elements and dust grains for the interstellar medium. The mass-loss rate can be well traced by carbon monoxide (CO) line emission. Aims: We present new Herschel/HIFI and IRAM 30 m telescope CO line data for a sample of 53 galactic AGB stars. The lines cover a fairly large range of excitation energy from the J = 1 → 0 line to the J = 9 → 8 line, and even the J = 14 → 13 line in a few cases. We perform radiative transfer modelling for 38 of these sources to estimate their mass-loss rates. Methods: We used a radiative transfer code based on the Monte Carlo method to model the CO line emission. We assume spherically symmetric circumstellar envelopes that are formed by a constant mass-loss rate through a smoothly accelerating wind. Results: We find models that are consistent across a broad range of CO lines for most of the stars in our sample, i.e., a large number of the circumstellar envelopes can be described with a constant mass-loss rate. We also find that an accelerating wind is required to fit, in particular, the higher-J lines and that a velocity law will have a significant effect on the model line intensities. The results cover a wide range of mass-loss rates (~10-8 to 2 × 10-5 M⊙ yr-1) and gas expansion velocities (2 to 21.5 km s-1) , and include M-, S-, and C-type AGB stars. Our results generally agree with those of earlier studies, although we tend to find slightly lower mass-loss rates by about 40%, on average. We also present "bonus" lines detected during our CO observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Appendices are available in electronic form at http://www.aanda.org

Spectral Analysis of the Accretion Flow in NGC 1052 with Suzaku

NASA Technical Reports Server (NTRS)

Brenneman, L. W.; Weaver, K. A.; Kadler, M.; Tueller, J.; Marscher, A.; Ros, E.; Zensus,A.; Kovalev, Y. Y.; Aller, M.; Aller, H.;

A Fe K Line in GRB 970508

NASA Astrophysics Data System (ADS)

Protassov, R.; van Dyk, D.; Connors, A.; Kashyap, V.; Siemiginowska, A.

2000-12-01

We examine the x-ray spectrum of the afterglow of GRB 970508, analyzed for Fe line emission by Piro et al (1999, ApJL, 514, L73). This is a difficult and extremely important measurement: the detection of x-ray afterglows from γ -ray bursts is at best a tricky business, relying on near-real satellite time response to unpredictable events; and a great deal of luck in catching a burst bright enough for a useful spectral analysis. Detecting a clear atomic (or cyclotron) line in the generally smooth and featureless afterglow (or burst) emission not only gives one of the few very specific keys to the physics local to the emission region, but also provides clues or confirmation of its distance (via redshift). Unfortunately, neither the likelihood ratio test or the related F-statistic commonly used to detect spectral lines adhere to their nominal Chi square and F-distributions. Thus we begin by calibrating the F-statistic used in Piro et al (1999, ApJL, 514, L73) via a simulation study. The simulation study relies on a completely specified source model, i.e. we do Monte Carlo simulations with all model parameters fixed (so--called ``parametric bootstrapping''). Second, we employ the method of posterior predictive p-values to calibrate a LRT statistic while accounting for the uncertainty in the parameters of the source model. Our analysis reveals evidence for the Fe K line.

Gyrokinetic continuum simulation of turbulence in a straight open-field-line plasma

DOE PAGES

Shi, E. L.; Hammett, G. W.; Stoltzfus-Dueck, T.; ...

2017-05-29

Here, five-dimensional gyrokinetic continuum simulations of electrostatic plasma turbulence in a straight, open-field-line geometry have been performed using a full- discontinuous-Galerkin approach implemented in the Gkeyll code. While various simplifications have been used for now, such as long-wavelength approximations in the gyrokinetic Poisson equation and the Hamiltonian, these simulations include the basic elements of a fusion-device scrape-off layer: localised sources to model plasma outflow from the core, cross-field turbulent transport, parallel flow along magnetic field lines, and parallel losses at the limiter or divertor with sheath-model boundary conditions. The set of sheath-model boundary conditions used in the model allows currentsmore » to flow through the walls. In addition to details of the numerical approach, results from numerical simulations of turbulence in the Large Plasma Device, a linear device featuring straight magnetic field lines, are presented.« less

Performance evaluation of air quality models for predicting PM10 and PM2.5 concentrations at urban traffic intersection during winter period.

PubMed

Gokhale, Sharad; Raokhande, Namita

2008-05-01

There are several models that can be used to evaluate roadside air quality. The comparison of the operational performance of different models pertinent to local conditions is desirable so that the model that performs best can be identified. Three air quality models, namely the 'modified General Finite Line Source Model' (M-GFLSM) of particulates, the 'California Line Source' (CALINE3) model, and the 'California Line Source for Queuing & Hot Spot Calculations' (CAL3QHC) model have been identified for evaluating the air quality at one of the busiest traffic intersections in the city of Guwahati. These models have been evaluated statistically with the vehicle-derived airborne particulate mass emissions in two sizes, i.e. PM10 and PM2.5, the prevailing meteorology and the temporal distribution of the measured daily average PM10 and PM2.5 concentrations in wintertime. The study has shown that the CAL3QHC model would make better predictions compared to other models for varied meteorology and traffic conditions. The detailed study reveals that the agreements between the measured and the modeled PM10 and PM2.5 concentrations have been reasonably good for CALINE3 and CAL3QHC models. Further detailed analysis shows that the CAL3QHC model performed well compared to the CALINE3. The monthly performance measures have also led to the similar results. These two models have also outperformed for a class of wind speed velocities except for low winds (<1 m s(-1)), for which, the M-GFLSM model has shown the tendency of better performance for PM10. Nevertheless, the CAL3QHC model has outperformed for both the particulate sizes and for all the wind classes, which therefore can be optional for air quality assessment at urban traffic intersections.

2010 August 1–2 Sympathetic Eruptions. II. Magnetic Topology of the MHD Background Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, Viacheslav S.; Mikić, Zoran; Török, Tibor

Using a potential field source-surface (PFSS) model, we recently analyzed the global topology of the background coronal magnetic field for a sequence of coronal mass ejections (CMEs) that occurred on 2010 August 1–2. Here we repeat this analysis for the background field reproduced by a magnetohydrodynamic (MHD) model that incorporates plasma thermodynamics. As for the PFSS model, we find that all three CME source regions contain a coronal hole (CH) that is separated from neighboring CHs by topologically very similar pseudo-streamer structures. However, the two models yield very different results for the size, shape, and flux of the CHs. Wemore » find that the helmet-streamer cusp line, which corresponds to a source-surface null line in the PFSS model, is structurally unstable and does not form in the MHD model. Our analysis indicates that, generally, in MHD configurations, this line instead consists of a multiple-null separator passing along the edge of disconnected-flux regions. Some of these regions are transient and may be the origin of the so-called streamer blobs. We show that the core topological structure of such blobs is a three-dimensional “plasmoid” consisting of two conjoined flux ropes of opposite handedness, which connect at a spiral null point of the magnetic field. Our analysis reveals that such plasmoids also appear in pseudo-streamers on much smaller scales. These new insights into the coronal magnetic topology provide some intriguing implications for solar energetic particle events and for the properties of the slow solar wind.« less

2010 August 1-2 Sympathetic Eruptions. II. Magnetic Topology of the MHD Background Field

NASA Astrophysics Data System (ADS)

Titov, Viacheslav S.; Mikić, Zoran; Török, Tibor; Linker, Jon A.; Panasenco, Olga

2017-08-01

Using a potential field source-surface (PFSS) model, we recently analyzed the global topology of the background coronal magnetic field for a sequence of coronal mass ejections (CMEs) that occurred on 2010 August 1-2. Here we repeat this analysis for the background field reproduced by a magnetohydrodynamic (MHD) model that incorporates plasma thermodynamics. As for the PFSS model, we find that all three CME source regions contain a coronal hole (CH) that is separated from neighboring CHs by topologically very similar pseudo-streamer structures. However, the two models yield very different results for the size, shape, and flux of the CHs. We find that the helmet-streamer cusp line, which corresponds to a source-surface null line in the PFSS model, is structurally unstable and does not form in the MHD model. Our analysis indicates that, generally, in MHD configurations, this line instead consists of a multiple-null separator passing along the edge of disconnected-flux regions. Some of these regions are transient and may be the origin of the so-called streamer blobs. We show that the core topological structure of such blobs is a three-dimensional “plasmoid” consisting of two conjoined flux ropes of opposite handedness, which connect at a spiral null point of the magnetic field. Our analysis reveals that such plasmoids also appear in pseudo-streamers on much smaller scales. These new insights into the coronal magnetic topology provide some intriguing implications for solar energetic particle events and for the properties of the slow solar wind.

Hydrocarbon Reservoir Identification in Volcanic Zone by using Magnetotelluric and Geochemistry Information

NASA Astrophysics Data System (ADS)

Firda, S. I.; Permadi, A. N.; Supriyanto; Suwardi, B. N.

2018-03-01

The resistivity of Magnetotelluric (MT) data show the resistivity mapping in the volcanic reservoir zone and the geochemistry information for confirm the reservoir and source rock formation. In this research, we used 132 data points divided with two line at exploration area. We used several steps to make the resistivity mapping. There are time series correction, crosspower correction, then inversion of Magnetotelluric (MT) data. Line-2 and line-3 show anomaly geological condition with Gabon fault. The geology structure from the resistivity mapping show the fault and the geological formation with the geological rock data mapping distribution. The geochemistry information show the maturity of source rock formation. According to core sample analysis information, we get the visual porosity for reservoir rock formation in several geological structure. Based on that, we make the geological modelling where the potential reservoir and the source rock around our interest area.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Fan W.; Contescu, Cristian I.; Gallego, Nidia C.

Laser ultrasonic line source methods have been used to study elastic anisotropy in nuclear graphites by measuring shear wave birefringence. Depending on the manufacturing processes used during production, nuclear graphites can exhibit various degrees of material anisotropy related to preferred crystallite orientation and to microcracking. In this paper, laser ultrasonic line source measurements of shear wave birefringence on NBG-25 have been performed to assess elastic anisotropy. Laser line sources allow specific polarizations for shear waves to be transmitted – the corresponding wavespeeds can be used to compute bulk, elastic moduli that serve to quantify anisotropy. These modulus values can bemore » interpreted using physical property models based on orientation distribution coefficients and microcrack-modified, single crystal moduli to represent the combined effects of crystallite orientation and microcracking on material anisotropy. Finally, ultrasonic results are compared to and contrasted with measurements of anisotropy based on the coefficient of thermal expansion to show the relationship of results from these techniques.« less

Radiative transfer of HCN: interpreting observations of hyperfine anomalies

NASA Astrophysics Data System (ADS)

Mullins, A. M.; Loughnane, R. M.; Redman, M. P.; Wiles, B.; Guegan, N.; Barrett, J.; Keto, E. R.

2016-07-01

Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components. The hyperfine splitting is particularly advantageous in interpreting the physical conditions of the emitting gas because with a second rotational transition, both gas density and temperature can be derived. For HCN however, the relative strengths of the hyperfine lines are anomalous. They appear in ratios which can vary significantly from source to source, and are inconsistent with local thermodynamic equilibrium (LTE). This is the HCN hyperfine anomaly, and it prevents the use of simple LTE models of HCN emission to derive reliable optical depths. In this paper, we demonstrate how to model HCN hyperfine line emission, and derive accurate line ratios, spectral line shapes and optical depths. We show that by carrying out radiative transfer calculations over each hyperfine level individually, as opposed to summing them over each rotational level, the anomalous hyperfine emission emerges naturally. To do this requires not only accurate radiative rates between hyperfine states, but also accurate collisional rates. We investigate the effects of different sets of hyperfine collisional rates, derived via the proportional method and through direct recoupling calculations. Through an extensive parameter sweep over typical low-mass star-forming conditions, we show the HCN line ratios to be highly variable to optical depth. We also reproduce an observed effect whereby the red-blue asymmetry of the hyperfine lines (an infall signature) switches sense within a single rotational transition.

Can the relativistic light-bending model explain X-ray spectral variations of Seyfert galaxies?

NASA Astrophysics Data System (ADS)

Mizumoto, Misaki; Moriyama, Kotaro; Ebisawa, Ken; Mineshige, Shin; Kawanaka, Norita; Tsujimoto, Masahiro

2018-04-01

Many Seyfert galaxies are known to exhibit Fe-K broad emission line features in their X-ray energy spectra. The observed lines have three distinct features: (1) the line profiles are skewed and show significant low-energy tails, (2) the Fe-K band has low variability, which produces a broad and deep dip in the root-mean-square (rms) spectra, and (3) photons in this band have time lags behind those in the adjacent energy bands with amplitudes of several Rg/c, where Rg is the gravitational radius. The "relativistic light-bending model" is proposed to explain these observed features, where a compact X-ray source ("lamp post") above an extreme Kerr black hole illuminates the innermost area of the accretion disc. In this paper, we critically examine the relativistic light-bending model by computing the rms spectra and the lag features using a ray-tracing technique, when a lamp post moves vertically on the black hole spin axis. As a result, we found that the observed deep rms dip requires that the iron is extremely overabundant (≳10 solar), whereas the observed lag amplitude is consistent with the normal iron abundance. Furthermore, disappearance of the lag in the high-flux state requires a source height as high as ˜40 Rg, which contradicts the relativistically broad emission line feature. Our simulations agree with the data that the reverberation feature moves to lower frequencies with larger source height; however, if this scenario is correct, the simulations predict the detection of a clear Fe-K lag at low frequencies, which is not constrained in the data. Therefore, we conclude that the relativistic light-bending model may not explain the characteristic Fe-K spectral variations in Seyfert galaxies.

Can the relativistic light-bending model explain X-ray spectral variations of Seyfert galaxies?

NASA Astrophysics Data System (ADS)

Mizumoto, Misaki; Moriyama, Kotaro; Ebisawa, Ken; Mineshige, Shin; Kawanaka, Norita; Tsujimoto, Masahiro

2018-06-01

Many Seyfert galaxies are known to exhibit Fe-K broad emission line features in their X-ray energy spectra. The observed lines have three distinct features: (1) the line profiles are skewed and show significant low-energy tails, (2) the Fe-K band has low variability, which produces a broad and deep dip in the root-mean-square (rms) spectra, and (3) photons in this band have time lags behind those in the adjacent energy bands with amplitudes of several Rg/c, where Rg is the gravitational radius. The "relativistic light-bending model" is proposed to explain these observed features, where a compact X-ray source ("lamp post") above an extreme Kerr black hole illuminates the innermost area of the accretion disc. In this paper, we critically examine the relativistic light-bending model by computing the rms spectra and the lag features using a ray-tracing technique, when a lamp post moves vertically on the black hole spin axis. As a result, we found that the observed deep rms dip requires that the iron is extremely overabundant (≳10 solar), whereas the observed lag amplitude is consistent with the normal iron abundance. Furthermore, disappearance of the lag in the high-flux state requires a source height as high as ˜40 Rg, which contradicts the relativistically broad emission line feature. Our simulations agree with the data that the reverberation feature moves to lower frequencies with larger source height; however, if this scenario is correct, the simulations predict the detection of a clear Fe-K lag at low frequencies, which is not constrained in the data. Therefore, we conclude that the relativistic light-bending model may not explain the characteristic Fe-K spectral variations in Seyfert galaxies.

GARLIC, A SHIELDING PROGRAM FOR GAMMA RADIATION FROM LINE- AND CYLINDER- SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roos, M.

1959-06-01

GARLlC is a program for computing the gamma ray flux or dose rate at a shielded isotropic point detector, due to a line source or the line equivalent of a cylindrical source. The source strength distribution along the line must be either uniform or an arbitrary part of the positive half-cycle of a cosine function The line source can be orierted arbitrarily with respect to the main shield and the detector, except that the detector must not be located on the line source or on its extensionThe main source is a homogeneous plane slab in which scattered radiation is accountedmore » for by multiplying each point element of the line source by a point source buildup factor inside the integral over the point elements. Between the main shield and the line source additional shields can be introduced, which are either plane slabs, parallel to the main shield, or cylindrical rings, coaxial with the line source. Scattered radiation in the additional shields can only be accounted for by constant build-up factors outside the integral. GARLlC-xyz is an extended version particularly suited for the frequently met problem of shielding a room containing a large number of line sources in diHerent positions. The program computes the angles and linear dimensions of a problem for GARLIC when the positions of the detector point and the end points of the line source are given as points in an arbitrary rectangular coordinate system. As an example the isodose curves in water are presented for a monoenergetic cosine-distributed line source at several source energies and for an operating fuel element of the Swedish reactor R3, (auth)« less

Non-Spherical Source-Surface Model of the Corona and Heliosphere for a Quadrupolar Main Field of the Sun

NASA Astrophysics Data System (ADS)

Schulz, M.

2008-05-01

Different methods of modeling the coronal and heliospheric magnetic field are conveniently visualized and intercompared by applying them to ideally axisymmetric field models. Thus, for example, a dipolar main B field with its moment parallel to the Sun's rotation axis leads to a flat heliospheric current sheet. More general solar main B fields (still axisymmetric about the solar rotation axis for simplicity) typically lead to cone-shaped current sheets beyond the source surface (and presumably also in MHD models). As in the dipolar case [Schulz et al., Solar Phys., 60, 83-104, 1978], such conical current sheets can be made realistically thin by taking the source surface to be non-spherical in a way that reflects the underlying structure of the Sun's main B field. A source surface that seems to work well in this respect [Schulz, Ann. Geophysicae, 15, 1379-1387, 1997] is a surface of constant F = (1/r)kB, where B is the scalar strength of the Sun's main magnetic field and k (~ 1.4) is a shape parameter. This construction tends to flatten the source surface in regions where B is relatively weak. Thus, for example, the source surface for a dipolar B field is shaped somewhat like a Rugby football, whereas the source surface for an axisymmetric quadrupolar B field is similarly elongated but somewhat flattened (as if stuffed into a pair of co-axial cones) at mid-latitudes. A linear combination of co-axial dipolar and quadrupolar B fields generates a somewhat apple-shaped source surface. If the region surrounded by the source surface is regarded as current-free, then the source surface itself should be (as nearly as possible) an equipotential surface for the corresponding magnetic scalar potential (expanded, for example, in spherical harmonics). More generally, the mean-square tangential component of the coronal magnetic field over the source surface should be minimized with respect to any adjustable parameters of the field model. The solar wind should then flow not quite radially, but rather in a straight line along the outward normal to the source surface, and the heliospheric B field should follow a corresponding generalization of Parker's spiral [Levine et al., Solar Phys., 77, 363-392, 1982]. In this work the above program is implemented for a Sun with an axisymmetric but purely quadrupolar main magnetic field. Two heliospheric current sheets emanate from circular neutral lines at mid-latitudes on the corresponding source surface. However, because the source surface is relatively flattened in regions where these neutral lines appear, the radial component of the heliospheric B field at r ~ 1 AU and beyond is much more nearly latitude-independent in absolute value than one would expect from a model based on a spherical source surface.

Molecular characterization of breast cancer cell lines through multiple omic approaches.

PubMed

Smith, Shari E; Mellor, Paul; Ward, Alison K; Kendall, Stephanie; McDonald, Megan; Vizeacoumar, Frederick S; Vizeacoumar, Franco J; Napper, Scott; Anderson, Deborah H

2017-06-05

Breast cancer cell lines are frequently used as model systems to study the cellular properties and biology of breast cancer. Our objective was to characterize a large, commonly employed panel of breast cancer cell lines obtained from the American Type Culture Collection (ATCC 30-4500 K) to enable researchers to make more informed decisions in selecting cell lines for specific studies. Information about these cell lines was obtained from a wide variety of sources. In addition, new information about cellular pathways that are activated within each cell line was generated. We determined key protein expression data using immunoblot analyses. In addition, two analyses on serum-starved cells were carried out to identify cellular proteins and pathways that are activated in these cells. These analyses were performed using a commercial PathScan array and a novel and more extensive phosphopeptide-based kinome analysis that queries 1290 phosphorylation events in major signaling pathways. Data about this panel of breast cancer cell lines was also accessed from several online sources, compiled and summarized for the following areas: molecular classification, mRNA expression, mutational status of key proteins and other possible cancer-associated mutations, and the tumorigenic and metastatic capacity in mouse xenograft models of breast cancer. The cell lines that were characterized included 10 estrogen receptor (ER)-positive, 12 human epidermal growth factor receptor 2 (HER2)-amplified and 18 triple negative breast cancer cell lines, in addition to 4 non-tumorigenic breast cell lines. Within each subtype, there was significant genetic heterogeneity that could impact both the selection of model cell lines and the interpretation of the results obtained. To capture the net activation of key signaling pathways as a result of these mutational combinations, profiled pathway activation status was examined. This provided further clarity for which cell lines were particularly deregulated in common or unique ways. These two new kinase or "Kin-OMIC" analyses add another dimension of important data about these frequently used breast cancer cell lines. This will assist researchers in selecting the most appropriate cell lines to use for breast cancer studies and provide context for the interpretation of the emerging results.

Line-source excited impulsive EM field response of thin plasmonic metal films

NASA Astrophysics Data System (ADS)

Štumpf, Martin; Vandenbosch, Guy A. E.

2013-08-01

In this paper, reflection against and transmission through thin plasmonic metal films, basic building blocks of many plasmonic devices, are analytically investigated directly in the time domain for an impulsive electric and magnetic line-source excitation. The electromagnetic properties of thin metallic films are modeled via the Drude model. The problem is formulated with the help of approximate thin-sheet boundary conditions and the analysis is carried out using the Cagniard-DeHoop technique. Closed-form space-time expressions are found and discussed. The obtained time-domain analytical expressions reveal the existence of the phenomenon of transient oscillatory surface effects along a plasmonic metal thin sheet. Illustrative numerical examples of transmitted/reflected pulsed fields are provided.

Line-source excitation of realistic conformal metasurface cloaks

NASA Astrophysics Data System (ADS)

Padooru, Yashwanth R.; Yakovlev, Alexander B.; Chen, Pai-Yen; Alù, Andrea

2012-11-01

Following our recently introduced analytical tools to model and design conformal mantle cloaks based on metasurfaces [Padooru et al., J. Appl. Phys. 112, 034907 (2012)], we investigate their performance and physical properties when excited by an electric line source placed in their close proximity. We consider metasurfaces formed by 2-D arrays of slotted (meshes and Jerusalem cross slots) and printed (patches and Jerusalem crosses) sub-wavelength elements. The electromagnetic scattering analysis is carried out using a rigorous analytical model, which utilizes the two-sided impedance boundary conditions at the interface of the sub-wavelength elements. It is shown that the homogenized grid-impedance expressions, originally derived for planar arrays of sub-wavelength elements and plane-wave excitation, may be successfully used to model and tailor the surface reactance of cylindrical conformal mantle cloaks illuminated by near-field sources. Our closed-form analytical results are in good agreement with full-wave numerical simulations, up to sub-wavelength distances from the metasurface, confirming that mantle cloaks may be very effective to suppress the scattering of moderately sized objects, independent of the type of excitation and point of observation. We also discuss the dual functionality of these metasurfaces to boost radiation efficiency and directivity from confined near-field sources.

A modeling framework for characterizing near-road air pollutant concentration at community scales

EPA Science Inventory

In this study, we combine information from transportation network, traffic emissions, and dispersion model to develop a framework to inform exposure estimates for traffic-related air pollutants (TRAPs) with a high spatial resolution. A Research LINE source dispersion model (R-LIN...

Testing and Analytical Modeling for Purging Process of a Cryogenic Line

NASA Technical Reports Server (NTRS)

Hedayat, A.; Mazurkivich, P. V.; Nelson, M. A.; Majumdar, A. K.

2013-01-01

The purging operations for cryogenic main propulsion systems of upper stage are usually carried out for the following cases: 1) Purging of the Fill/Drain line after completion of propellant loading. This operation allows the removal of residual propellant mass; and 2) Purging of the Feed/Drain line if the mission is scrubbed. The lines would be purged by connections to a ground high-pressure gas storage source. The flowrate of purge gas should be regulated such that the pressure in the line will not exceed the required maximum allowable value. Exceeding the maximum allowable pressure may lead to structural damage in the line. To gain confidence in analytical models of the purge process, a test series was conducted. The test article, a 20-cm incline line, was filled with liquid hydrogen and then purged with gaseous helium (GHe). The influences of GHe flowrates and initial temperatures were evaluated. The Generalized Fluid System Simulation Program, an in-house general-purpose computer program for flow network analysis, was utilized to model and simulate the testing. The test procedures, modeling descriptions, and the results will be presented in the final paper.

Testing and Analytical Modeling for Purging Process of a Cryogenic Line

NASA Technical Reports Server (NTRS)

Hedayat, A.; Mazurkivich, P. V.; Nelson, M. A.; Majumdar, A. K.

2015-01-01

The purging operations for cryogenic main propulsion systems of upper stage are usually carried out for the following cases: 1) Purging of the Fill/Drain line after completion of propellant loading. This operation allows the removal of residual propellant mass; and 2) Purging of the Feed/Drain line if the mission is scrubbed. The lines would be purged by connections to a ground high-pressure gas storage source. The flow-rate of purge gas should be regulated such that the pressure in the line will not exceed the required maximum allowable value. Exceeding the maximum allowable pressure may lead to structural damage in the line. To gain confidence in analytical models of the purge process, a test series was conducted. The test article, a 20-cm incline line, was filled with liquid hydrogen and then purged with gaseous helium (GHe). The influences of GHe flow-rates and initial temperatures were evaluated. The Generalized Fluid System Simulation Program, an in-house general-purpose computer program for flow network analysis, was utilized to model and simulate the testing. The test procedures, modeling descriptions, and the results will be presented in the final paper.

Optical Variability of Narrow-line and Broad-line Seyfert 1 Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rakshit, Suvendu; Stalin, C. S., E-mail: suvenduat@gmail.com

We studied the optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z < 0.8 to investigate any differences in their OV properties. Using archival optical V -band light curves from the Catalina Real Time Transient Survey that span 5–9 years and modeling them using damped random walk, we estimated the amplitude of variability. We found that NLSy1 galaxies as a class show lower amplitude of variability than their broad-line counterparts. In the sample of both NLSy1 and BLSy1 galaxies, radio-loud sources are found to have higher variability amplitude thanmore » radio-quiet sources. Considering only sources that are detected in the X-ray band, NLSy1 galaxies are less optically variable than BLSy1 galaxies. The amplitude of variability in the sample of both NLSy1 and BLSy1 galaxies is found to be anti-correlated with Fe ii strength but correlated with the width of the H β line. The well-known anti-correlation of variability–luminosity and the variability–Eddington ratio is present in our data. Among the radio-loud sample, variability amplitude is found to be correlated with radio-loudness and radio-power, suggesting that jets also play an important role in the OV in radio-loud objects, in addition to the Eddington ratio, which is the main driving factor of OV in radio-quiet sources.« less

Optical Variability of Narrow-line and Broad-line Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Rakshit, Suvendu; Stalin, C. S.

2017-06-01

We studied the optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z < 0.8 to investigate any differences in their OV properties. Using archival optical V-band light curves from the Catalina Real Time Transient Survey that span 5-9 years and modeling them using damped random walk, we estimated the amplitude of variability. We found that NLSy1 galaxies as a class show lower amplitude of variability than their broad-line counterparts. In the sample of both NLSy1 and BLSy1 galaxies, radio-loud sources are found to have higher variability amplitude than radio-quiet sources. Considering only sources that are detected in the X-ray band, NLSy1 galaxies are less optically variable than BLSy1 galaxies. The amplitude of variability in the sample of both NLSy1 and BLSy1 galaxies is found to be anti-correlated with Fe II strength but correlated with the width of the Hβ line. The well-known anti-correlation of variability-luminosity and the variability-Eddington ratio is present in our data. Among the radio-loud sample, variability amplitude is found to be correlated with radio-loudness and radio-power, suggesting that jets also play an important role in the OV in radio-loud objects, in addition to the Eddington ratio, which is the main driving factor of OV in radio-quiet sources.

Infrared coronal emission lines and the possibility of their maser emission in Seyfert nuclei

NASA Technical Reports Server (NTRS)

Greenhouse, Matthew A.; Feldman, Uri; Smith, Howard A.; Klapisch, Marcel; Bhatia, Anand K.; Bar-Shalom, Abi

1993-01-01

Energetic emitting regions have traditionally been studied via x-ray, UV and optical emission lines of highly ionized intermediate mass elements. Such lines are often referred to as 'coronal lines' since the ions, when produced by collisional ionization, reach maximum abundance at electron temperatures of approx. 10(exp 5) - 10(exp 6) K typical of the sun's upper atmosphere. However, optical and UV coronal lines are also observed in a wide variety of Galactic and extragalactic sources including the Galactic interstellar medium, nova shells, supernova remnants, galaxies and QSOs. Infrared coronal lines are providing a new window for observation of energetic emitting regions in heavily dust obscured sources such as infrared bright merging galaxies and Seyfert nuclei and new opportunities for model constraints on physical conditions in these sources. Unlike their UV and optical counterparts, infrared coronal lines can be primary coolants of collisionally ionized plasmas with 10(exp 4) less than T(sub e)(K) less than 10(exp 6) which produce little or no optical or shorter wavelength coronal line emission. In addition, they provide a means to probe heavily dust obscured emitting regions which are often inaccessible to optical or UV line studies. In this poster, we provide results from new model calculations to support upcoming Infrared Space Observatory (ISO) and current ground-based observing programs involving infrared coronal emission lines in AGN. We present a complete list of infrared (lambda greater than 1 micron) lines due to transitions within the ground configurations 2s(2)2p(k) and 3s(2)3p(k) (k = 1 to 5) or the first excited configurations 2s2p and 3s3p of highly ionized (x greater than or equal to 100 eV) astrophysically abundant (n(X)/n(H) greater than or equal to 10(exp -6)) elements. Included are approximately 74 lines in ions of O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, and Ni spanning a wavelength range of approximately 1 - 280 microns. We present new results from detailed balance calculations, new critical densities for collisional de-excitation, intrinsic photon rates, branching ratios, and excitation temperatures for the majority of the compiled transitions. The temperature and density parameter space for dominant cooling via infrared coronal lines is presented, and the relationship of infrared to optical coronal lines is discussed.

Discovery of the Red-Skewed K-alpha Iron Line in Cyg X-2 with Suzaku

NASA Technical Reports Server (NTRS)

Shaposhnikov, Nikolai; Titarchuk, Lev; Laurent, Philippe

2008-01-01

We report on the Suzaku observation of neutron star low-mass X-ray binary Cygnus X-2 which reveals strong iron K-alpha emission line. The line profile shows a prominent red wing extending down to 4 keV. This discovery increases the number of neutron star sources where red-skewed iron lines were observed and strongly suggests that this phenomenon is common not only in black holes but also in other types of compact objects. We examine the line profile by fitting it with the model which attributes its production to the relativistic effects due to disk reflection of X-ray radiation. We also apply an alternative model where the red wing is a result of down-scattering effect of the first order with respect to electron velocity in the wind outflow. Both models describe adequately the observed line profile. However, the X-ray variability in a state similar to that in the Suzaku observation which we establish by analysing RXTE observation favors the wind origin of the line formation.

The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. I. Observational Results for Holmberg II ULX

NASA Technical Reports Server (NTRS)

Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

2009-01-01

We presen the first Spitzer Infrared Spectrograph (IRS) observations of the [O IV] 25.89 um emission line detected from the ultraluminous X-ray source (ULX) in Holmberg II. This line is a well established signature of high excitation usually associated with AGN. Its detection suggests that the ULX has a strong impact on the surrounding gas. A Spitzer high resolution spectral map shows that the [O IV] is coincident with the X-ray position of the ULX. The ratios of the [O IV] to lower ionization lines are similar to those observed in AGN, suggesting that a strong UV and X-ray source is responsible for the, photoionization. The best XMM-Newton data is used to model the X-ray band which is then extrapolated into the UV. We perform infrared and ultraviolet photometry, and use its previously published optical and radio data to construct the full SED for the ULX and its companion. The preferred model to describe the SED includes an accretion disk which dominates the soft X-rays but contributes little at UV and optical wavelengths. The optical counterpart is consistent with a B supergiant as previously suggested in other studies. The bolometric luminosity of the ULX suggests the presence of an intermediate-mass black hole with mass >85 M for sub-Eddington accretion or, alternatively, a stellar-mass black hole that is accreting at super-Eddington rates. In a follow-up second paper we perform detailed photoionization modeling of the infrared lines in order to constrain the bolometric luminosity of the ULX.

Improving Energy Efficiency for the Vehicle Assembly Industry: A Discrete Event Simulation Approach

NASA Astrophysics Data System (ADS)

Oumer, Abduaziz; Mekbib Atnaw, Samson; Kie Cheng, Jack; Singh, Lakveer

2016-11-01

This paper presented a Discrete Event Simulation (DES) model for investigating and improving energy efficiency in vehicle assembly line. The car manufacturing industry is one of the highest energy consuming industries. Using Rockwell Arena DES package; a detailed model was constructed for an actual vehicle assembly plant. The sources of energy considered in this research are electricity and fuel; which are the two main types of energy sources used in a typical vehicle assembly plant. The model depicts the performance measurement for process- specific energy measures of painting, welding, and assembling processes. Sound energy efficiency model within this industry has two-fold advantage: reducing CO2 emission and cost reduction associated with fuel and electricity consumption. The paper starts with an overview of challenges in energy consumption within the facilities of automotive assembly line and highlights the parameters for energy efficiency. The results of the simulation model indicated improvements for energy saving objectives and reduced costs.

Mass loss from alpha Cyg /A2Ia/ derived from the profiles of low excitation Fe II lines

NASA Technical Reports Server (NTRS)

Hensberge, H.; De Loore, C.; Lamers, H. J. G. L. M.; Bruhweiler, F. C.

1982-01-01

The low-excitation Fe II lines in the spectral region 2000-3000 A are studied in the spectrum of alpha-Cyg. The profiles of the resonance lines are described by four representative parameters, and a preliminary model is derived from the dependence of these parameters on theoretical line strength, taking into account the influence of blending photospheric lines in an overall and qualitative way. At least 11% of all iron in the wind is once ionized, unless a non-thermal heating source enhances the fraction Fe(++) without destroying much Al(+). It is shown that the contribution of blending photospheric absorption lines to weaker P Cygni profiles has been previously largely underestimated. The mass loss rate corresponding to the model is derived, and is smaller by a factor of 500 than the one derived from the infrared excess by Barlow and Cohen (1977).

Improving the seismic small-scale modelling by comparison with numerical methods

NASA Astrophysics Data System (ADS)

Pageot, Damien; Leparoux, Donatienne; Le Feuvre, Mathieu; Durand, Olivier; Côte, Philippe; Capdeville, Yann

2017-10-01

The potential of experimental seismic modelling at reduced scale provides an intermediate step between numerical tests and geophysical campaigns on field sites. Recent technologies such as laser interferometers offer the opportunity to get data without any coupling effects. This kind of device is used in the Mesures Ultrasonores Sans Contact (MUSC) measurement bench for which an automated support system makes possible to generate multisource and multireceivers seismic data at laboratory scale. Experimental seismic modelling would become a great tool providing a value-added stage in the imaging process validation if (1) the experimental measurement chain is perfectly mastered, and thus if the experimental data are perfectly reproducible with a numerical tool, as well as if (2) the effective source is reproducible along the measurement setup. These aspects for a quantitative validation concerning devices with piezoelectrical sources and a laser interferometer have not been yet quantitatively studied in published studies. Thus, as a new stage for the experimental modelling approach, these two key issues are tackled in the proposed paper in order to precisely define the quality of the experimental small-scale data provided by the bench MUSC, which are available in the scientific community. These two steps of quantitative validation are dealt apart any imaging techniques in order to offer the opportunity to geophysicists who want to use such data (delivered as free data) of precisely knowing their quality before testing any imaging technique. First, in order to overcome the 2-D-3-D correction usually done in seismic processing when comparing 2-D numerical data with 3-D experimental measurement, we quantitatively refined the comparison between numerical and experimental data by generating accurate experimental line sources, avoiding the necessity of geometrical spreading correction for 3-D point-source data. The comparison with 2-D and 3-D numerical modelling is based on the Spectral Element Method. The approach shows the relevance of building a line source by sampling several source points, except the boundaries effects on later arrival times. Indeed, the experimental results highlight the amplitude feature and the delay equal to π/4 provided by a line source in the same manner than numerical data. In opposite, the 2-D corrections applied on 3-D data showed discrepancies which are higher on experimental data than on numerical ones due to the source wavelet shape and interferences between different arrivals. The experimental results from the approach proposed here show that discrepancies are avoided, especially for the reflected echoes. Concerning the second point aiming to assess the experimental reproducibility of the source, correlation coefficients of recording from a repeated source impact on a homogeneous model are calculated. The quality of the results, that is, higher than 0.98, allow to calculate a mean source wavelet by inversion of a mean data set. Results obtained on a more realistic model simulating clays on limestones, confirmed the reproducibility of the source impact.

Experimental validation study of an analytical model of discrete frequency sound propagation in closed-test-section wind tunnels

NASA Technical Reports Server (NTRS)

Mosher, Marianne

1990-01-01

The principal objective is to assess the adequacy of linear acoustic theory with an impedence wall boundary condition to model the detailed sound field of an acoustic source in a duct. Measurements and calculations are compared of a simple acoustic source in a rectangular concrete duct lined with foam on the walls and anechoic end terminations. Measurement of acoustic pressure for twelve wave numbers provides variation in frequency and absorption characteristics of the duct walls. Close to the source, where the interference of wall reflections is minimal, correlation is very good. Away from the source, correlation degrades, especially for the lower frequencies. Sensitivity studies show little effect on the predicted results for changes in impedance boundary condition values, source location, measurement location, temperature, and source model for variations spanning the expected measurement error.

Directivity analysis of meander-line-coil EMATs with a wholly analytical method.

PubMed

Xie, Yuedong; Liu, Zenghua; Yin, Liyuan; Wu, Jiande; Deng, Peng; Yin, Wuliang

2017-01-01

This paper presents the simulation and experimental study of the radiation pattern of a meander-line-coil EMAT. A wholly analytical method, which involves the coupling of two models: an analytical EM model and an analytical UT model, has been developed to build EMAT models and analyse the Rayleigh waves' beam directivity. For a specific sensor configuration, Lorentz forces are calculated using the EM analytical method, which is adapted from the classic Deeds and Dodd solution. The calculated Lorentz force density are imported to an analytical ultrasonic model as driven point sources, which produce the Rayleigh waves within a layered medium. The effect of the length of the meander-line-coil on the Rayleigh waves' beam directivity is analysed quantitatively and verified experimentally. Copyright © 2016 Elsevier B.V. All rights reserved.

Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koulouri, Alexandra, E-mail: koulouri@uni-muenster.de; Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT; Brookes, Mike

In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In thismore » paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field. - Highlights: • Vector tomography is used to reconstruct electric fields generated by dipole sources. • Inverse solutions are based on longitudinal and transverse line integral measurements. • Transverse line integral measurements are used as a sparsity constraint. • Numerical procedure to approximate the line integrals is described in detail. • Patterns of the studied electric fields are correctly estimated.« less

Development and Evaluation of Model Algorithms to Account for Chemical Transformation in the Nearroad Environment

EPA Science Inventory

We describe the development and evaluation of two new model algorithms for NOx chemistry in the R-LINE near-road dispersion model for traffic sources. With increased urbanization, there is increased mobility leading to higher amount of traffic related activity on a global scale. ...

Herschel - PACS Survey Of Protoplanetary Disks In Taurus - Auriga Observations Of [O I] And [C Ii], And Far-Infrared Continuum

NASA Technical Reports Server (NTRS)

Howard, Christian; Sandell, Goeran; Vacca, William D.; Duchene, Gaspard; Matthews, Geoffrey; Augereau, Jean-Charles; Barbado, David; Dent, William R. F.; Eiroa, Carlos; Grady, Carol;

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lugaz, N.; Shibata, K.; Downs, C.

We present a numerical investigation of the coronal evolution of a coronal mass ejection (CME) on 2005 August 22 using a three-dimensional thermodynamic magnetohydrodynamic model, the space weather modeling framework. The source region of the eruption was anemone active region (AR) 10798, which emerged inside a coronal hole. We validate our modeled corona by producing synthetic extreme-ultraviolet (EUV) images, which we compare to EIT images. We initiate the CME with an out-of-equilibrium flux rope with an orientation and chirality chosen in agreement with observations of an H{alpha} filament. During the eruption, one footpoint of the flux rope reconnects with streamermore » magnetic field lines and with open field lines from the adjacent coronal hole. It yields an eruption which has a mix of closed and open twisted field lines due to interchange reconnection and only one footpoint line-tied to the source region. Even with the large-scale reconnection, we find no evidence of strong rotation of the CME as it propagates. We study the CME deflection and find that the effect of the Lorentz force is a deflection of the CME by about 3{sup 0} R{sup -1}{sub sun} toward the east during the first 30 minutes of the propagation. We also produce coronagraphic and EUV images of the CME, which we compare with real images, identifying a dimming region associated with the reconnection process. We discuss the implication of our results for the arrival at Earth of CMEs originating from the limb and for models to explain the presence of open field lines in magnetic clouds.« less

Asymmetries of solar oscillation line profiles

NASA Technical Reports Server (NTRS)

Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.; Osaki, Y.; Pomerantz, M. A.

1993-01-01

Asymmetries of the power spectral line profiles of solar global p-modes are detected in full-disk intensity observations of the Ca II K Fraunhofer line. The asymmetry is a strong function of temporal frequency being strongest at the lowest frequencies observed and vanishing near the peak of the power distribution. The variation with spherical harmonic degree is small. The asymmetry is interpreted in terms of a model in which the solar oscillation cavity is compared to a Fabry-Perot interferometer with the source slightly outside the cavity. A phase difference between an outward direct wave and a corresponding inward wave that passes through the cavity gives rise to the asymmetry. The asymmetry is different in velocity and intensity observations. Neglecting the asymmetry when modeling the power spectrum can lead to systematic errors in the measurement of mode frequencies of as much as 10 exp -4 of the mode frequency. The present observations and interpretation locate the source of the oscillations to be approximately 60 km beneath the photosphere, the shallowest position suggested to date.

Extreme Variability in a Broad Absorption Line Quasar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stern, Daniel; Jun, Hyunsung D.; Graham, Matthew J.

CRTS J084133.15+200525.8 is an optically bright quasar at z = 2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V ∼ 17.3 between 2002 and 2008. Then, over the following five years, the source slowly brightened by approximately one magnitude, to V ∼ 16.2. Only ∼1 in 10,000 quasars show such extreme variability, as quantified by the extreme parameters derived for this quasar assuming a damped random walk model. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line quasar withmore » extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. We report the first definitive redshift for this source, based on the detection of broad H α in a Keck/MOSFIRE spectrum. Absorption systems separated by several 1000 km s{sup −1} in velocity show coordinated weakening in the depths of their troughs as the continuum flux increases. We interpret the broad absorption line variability to be due to changes in photoionization, rather than due to motion of material along our line of sight. This source highlights one sort of rare transition object that astronomy will now be finding through dedicated time-domain surveys.« less

Airborne observations of the Orion molecular hydrogen emission spectrum

NASA Technical Reports Server (NTRS)

Davis, D. S.; Larson, H. P.; Smith, H. A.

1982-01-01

The Orion near-infrared H2 emission spectrum was observed from an altitude of 12.5 km in order to measure line intensities free from interference by terrestrial H2O. For the peak source, the observations indicate that the differential extinction between 4126 and 4712 per cm is 0.59 + or -0.06 mag, and the relative line intensities are consistent with those expected from a homogeneous source in approximate LTE at 1540 + or -100 K. An anomalous ortho/para H2 abundance ratio of 3.5(+ or - 0.2):1 is found, and the estimated total luminosity in vibrationally excited H2 lines is 300 + or - 100 solar luminosities. Rough molecular abundance limits, based on the missing H2 Q(6) line and the good agreement between other line intensities and the LTE model, place the H2 region no deeper within OMC-1 than the IR cluster and no shallower than 50 percent of the depth to the cluster.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abercrombie, Robert K; Udoeyop, Akaninyene W

This work examines a scientometric model that tracks the emergence of an identified technology from initial discovery (via original scientific and conference literature), through critical discoveries (via original scientific, conference literature and patents), transitioning through Technology Readiness Levels (TRLs) and ultimately on to commercial application. During the period of innovation and technology transfer, the impact of scholarly works, patents and on-line web news sources are identified. As trends develop, currency of citations, collaboration indicators, and on-line news patterns are identified. The combinations of four distinct and separate searchable on-line networked sources (i.e., scholarly publications and citation, worldwide patents, news archives,more » and on-line mapping networks) are assembled to become one collective network (a dataset for analysis of relations). This established network becomes the basis from which to quickly analyze the temporal flow of activity (searchable events) for the example subject domain we investigated.« less

The 4 micron spectra of compact infrared sources

NASA Technical Reports Server (NTRS)

Hofmann, R.; Larson, H. P.; Fink, U.

1986-01-01

High resolution 5 arcsec spectra in the 4 micron region are presented of the central 5 arcsec of the compact near infrared sources K3-50, W51-IRS2 East, and G333.6-0.2. From measured Br-alpha/Pf-beta line ratios and previously published infrared and radio maps, it is concluded that standard recombination theory fails to explain our observations in at least two cases. It is demonstrated that the data are consistent with thermal excitation of the hydrogen lines in strong stellar winds. The Pf-beta Hu-epsilon line ratio, which is completely insensitive to differential extinction, confirms the need for the stellar wind model for the core of G333.6-0.2. From the (K III) line it is estimated that the potassium abundance in G333.6-0.2 is at least equal to the solar value, and possibly enhanced by a factor up to 10.

Scientometric methods for identifying emerging technologies

DOEpatents

Abercrombie, Robert K; Schlicher, Bob G; Sheldon, Frederick T

2015-11-03

Provided is a method of generating a scientometric model that tracks the emergence of an identified technology from initial discovery (via original scientific and conference literature), through critical discoveries (via original scientific, conference literature and patents), transitioning through Technology Readiness Levels (TRLs) and ultimately on to commercial application. During the period of innovation and technology transfer, the impact of scholarly works, patents and on-line web news sources are identified. As trends develop, currency of citations, collaboration indicators, and on-line news patterns are identified. The combinations of four distinct and separate searchable on-line networked sources (i.e., scholarly publications and citation, worldwide patents, news archives, and on-line mapping networks) are assembled to become one collective network (a dataset for analysis of relations). This established network becomes the basis from which to quickly analyze the temporal flow of activity (searchable events) for the example subject domain.

Using dynamic flux chambers to estimate the natural attenuation rates in the subsurface at petroleum contaminated sites.

PubMed

Verginelli, Iason; Pecoraro, Roberto; Baciocchi, Renato

2018-04-01

In this work, we introduce a screening method for the evaluation of the natural attenuation rates in the subsurface at sites contaminated by petroleum hydrocarbons. The method is based on the combination of the data obtained from standard source characterization with dynamic flux chambers measurements. The natural attenuation rates are calculated as difference between the flux of contaminants estimated with a non-reactive diffusive model starting from the concentrations of the contaminants detected in the source (soil and/or groundwater) and the effective emission rate of the contaminants measured using dynamic flux chambers installed at ground level. The reliability of this approach was tested in a contaminated site characterized by the presence of BTEX in soil and groundwater. Namely, the BTEX emission rates from the subsurface were measured in 4 seasonal campaigns using dynamic flux chambers installed in 14 sampling points. The comparison of measured fluxes with those predicted using a non-reactive diffusive model, starting from the source concentrations, showed that, in line with other recent studies, the modelling approach can overestimate the expected outdoor concentration of petroleum hydrocarbons even up to 4 orders of magnitude. On the other hand, by coupling the measured data with the fluxes estimated with the diffusive non-reactive model, it was possible to perform a mass balance to evaluate the natural attenuation loss rates of petroleum hydrocarbons during the migration from the source to ground level. Based on this comparison, the estimated BTEX loss rates in the test site were up to almost 0.5kg/year/m 2 . These rates are in line with the values reported in the recent literature for natural source zone depletion. In short, the method presented in this work can represent an easy-to-use and cost-effective option that can provide a further line of evidence of natural attenuation rates expected at contaminated sites. Copyright © 2017 Elsevier B.V. All rights reserved.

Coronal Physics and the Chandra Emission Line Project

NASA Technical Reports Server (NTRS)

Brickhouse, N. S.; Drake, J. J.

2000-01-01

With the launch of the Chandra X-ray Observatory, high resolution X-ray spectroscopy of cosmic sources has begun. Early, deep observations of three stellar coronal sources Capella, Procyon, and HR 1099 are providing not only invaluable calibration data, but also benchmarks for plasma spectral models. These models are needed to interpret data from stellar coronae, galaxies and clusters of galaxies, supernova, remnants and other astrophysical sources. They have been called into question in recent years as problems with understanding low resolution ASCA and moderate resolution Extreme Ultraviolet Explorer Satellite (EUVE) data have arisen. The Emission Line Project is a collaborative effort, to improve the models, with Phase I being the comparison of models with observed spectra of Capella, Procyon, and HR 1099. Goals of these comparisons are (1) to determine and verify accurate and robust diagnostics and (2) to identify and prioritize issues in fundamental spectroscopy which will require further theoretical and/or laboratory work. A critical issue in exploiting the coronal data for these purposes is to understand the extent, to which common simplifying assumptions (coronal equilibrium, negligible optical depth) apply. We will discuss recent, advances in our understanding of stellar coronae, in this context.

PHOTOIONIZATION MODELS OF THE INNER GASEOUS DISK OF THE HERBIG BE STAR BD+65 1637

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, P.; Sigut, T. A. A.; Landstreet, J. D., E-mail: ppatel54@uwo.ca

2016-01-20

We attempt to constrain the physical properties of the inner, gaseous disk of the Herbig Be star BD+65 1637 using non-LTE, circumstellar disk codes and observed spectra (3700–10500 Å) from the ESPaDOnS instrument on the Canada–France–Hawaii Telescope. The photoionizing radiation of the central star is assumed to be the sole source of input energy for the disk. We model optical and near-infrared emission lines that are thought to form in this region using standard techniques that have been successful in modeling the spectra of classical Be stars. By comparing synthetic line profiles of hydrogen, helium, iron, and calcium with themore » observed line profiles, we try to constrain the geometry, density structure, and kinematics of the gaseous disk. Reasonable matches have been found for all line profiles individually; however, no disk density model based on a single power law for the equatorial density was able to simultaneously fit all of the observed emission lines. Among the emission lines, the metal lines, especially the Ca ii IR triplet, seem to require higher disk densities than the other lines. Excluding the Ca ii lines, a model in which the equatorial disk density falls as 10{sup −10} (R{sub *}/R){sup 3} g cm{sup −3} seen at an inclination of 45° for a 50 R{sub *} disk provides reasonable matches to the overall line shapes and strengths. The Ca ii lines seem to require a shallower drop-off as 10{sup −10} (R{sub *}/R){sup 2} g cm{sup −3} to match their strength. More complex disk density models are likely required to refine the match to the BD+65 1637 spectrum.« less

Photoionization Models of the Inner Gaseous Disk of the Herbig Be Star BD+65 1637

NASA Astrophysics Data System (ADS)

Patel, P.; Sigut, T. A. A.; Landstreet, J. D.

2016-01-01

We attempt to constrain the physical properties of the inner, gaseous disk of the Herbig Be star BD+65 1637 using non-LTE, circumstellar disk codes and observed spectra (3700-10500 Å) from the ESPaDOnS instrument on the Canada-France-Hawaii Telescope. The photoionizing radiation of the central star is assumed to be the sole source of input energy for the disk. We model optical and near-infrared emission lines that are thought to form in this region using standard techniques that have been successful in modeling the spectra of classical Be stars. By comparing synthetic line profiles of hydrogen, helium, iron, and calcium with the observed line profiles, we try to constrain the geometry, density structure, and kinematics of the gaseous disk. Reasonable matches have been found for all line profiles individually; however, no disk density model based on a single power law for the equatorial density was able to simultaneously fit all of the observed emission lines. Among the emission lines, the metal lines, especially the Ca II IR triplet, seem to require higher disk densities than the other lines. Excluding the Ca II lines, a model in which the equatorial disk density falls as 10-10 (R*/R)3 g cm-3 seen at an inclination of 45° for a 50 R* disk provides reasonable matches to the overall line shapes and strengths. The Ca II lines seem to require a shallower drop-off as 10-10 (R*/R)2 g cm-3 to match their strength. More complex disk density models are likely required to refine the match to the BD+65 1637 spectrum.

A developmentally plastic adult mouse kidney cell line spontaneously generates multiple adult kidney structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Carol F., E-mail: carol-webb@omrf.org; Immunobiology and Cancer Research, Oklahoma Medical Research Foundation, Oklahoma City, OK; Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK

Despite exciting new possibilities for regenerative therapy posed by the ability to induce pluripotent stem cells, recapitulation of three-dimensional kidneys for repair or replacement has not been possible. ARID3a-deficient mouse tissues generated multipotent, developmentally plastic cells. Therefore, we assessed the adult mouse ARID3a−/− kidney cell line, KKPS5, which expresses renal progenitor surface markers as an alternative cell source for modeling kidney development. Remarkably, these cells spontaneously developed into multicellular nephron-like structures in vitro, and engrafted into immunocompromised medaka mesonephros, where they formed mouse nephron structures. These data implicate KKPS5 cells as a new model system for studying kidney development. - Highlights:more » • An ARID3a-deficient mouse kidney cell line expresses multiple progenitor markers. • This cell line spontaneously forms multiple nephron-like structures in vitro. • This cell line formed mouse kidney structures in immunocompromised medaka fish kidneys. • Our data identify a novel model system for studying kidney development.« less

Delineating sources of groundwater recharge in an arsenic-affected Holocene aquifer in Cambodia using stable isotope-based mixing models

NASA Astrophysics Data System (ADS)

Richards, Laura A.; Magnone, Daniel; Boyce, Adrian J.; Casanueva-Marenco, Maria J.; van Dongen, Bart E.; Ballentine, Christopher J.; Polya, David A.

2018-02-01

Chronic exposure to arsenic (As) through the consumption of contaminated groundwaters is a major threat to public health in South and Southeast Asia. The source of As-affected groundwaters is important to the fundamental understanding of the controls on As mobilization and subsequent transport throughout shallow aquifers. Using the stable isotopes of hydrogen and oxygen, the source of groundwater and the interactions between various water bodies were investigated in Cambodia's Kandal Province, an area which is heavily affected by As and typical of many circum-Himalayan shallow aquifers. Two-point mixing models based on δD and δ18O allowed the relative extent of evaporation of groundwater sources to be estimated and allowed various water bodies to be broadly distinguished within the aquifer system. Model limitations are discussed, including the spatial and temporal variation in end member compositions. The conservative tracer Cl/Br is used to further discriminate between groundwater bodies. The stable isotopic signatures of groundwaters containing high As and/or high dissolved organic carbon plot both near the local meteoric water line and near more evaporative lines. The varying degrees of evaporation of high As groundwater sources are indicative of differing recharge contributions (and thus indirectly inferred associated organic matter contributions). The presence of high As groundwaters with recharge derived from both local precipitation and relatively evaporated surface water sources, such as ponds or flooded wetlands, are consistent with (but do not provide direct evidence for) models of a potential dual role of surface-derived and sedimentary organic matter in As mobilization.

Outburst in Mira AB?

NASA Astrophysics Data System (ADS)

Karovska, Margarita

2003-09-01

The nearby system Mira AB composed of an aging AGB star (Mira A) and a WD companion (Mira B) offers a unique laboratory for studying wind accretion processes, a poorly understood phenomenon in many sources. Recent Chandra ACIS-S Obs.(70ks on 12/6/03; PI.M.Karovska) resolved for the first time the components (~0.6") in X-rays, and detected a new bright soft source (< 0.7 keV) in addition to the harder (1-4 keV) emission from Mira B. The new source is spatially and spectrally separated from Mira B and likely associated with Mira A. This is the first detection of X-rays from an AGB star. This source was not detected by ROSAT in 1993 or recently by XMM 8/03 (AAS/03,J.Kastner), and could be a transient phenomenon. Model fitting shows that the soft X-ray emission is likely several emission lines, rather then a continuum; with ACIS spectral resolution we cannot resolve or identify these lines. We propose a 40ks LETG+HRC-S obs. to identify the lines and determine the emission mechanism.

Validation of community models: 3. Tracing field lines in heliospheric models

NASA Astrophysics Data System (ADS)

MacNeice, Peter; Elliott, Brian; Acebal, Ariel

2011-10-01

Forecasting hazardous gradual solar energetic particle (SEP) bursts at Earth requires accurately modeling field line connections between Earth and the locations of coronal or interplanetary shocks that accelerate the particles. We test the accuracy of field lines reconstructed using four different models of the ambient coronal and inner heliospheric magnetic field, through which these shocks must propagate, including the coupled Wang-Sheeley-Arge (WSA)/ENLIL model. Evaluating the WSA/ENLIL model performance is important since it is the most sophisticated model currently available to space weather forecasters which can model interplanetary coronal mass ejections and, when coupled with particle acceleration and transport models, will provide a complete model for gradual SEP bursts. Previous studies using a simpler Archimedean spiral approach above 2.5 solar radii have reported poor performance. We test the accuracy of the model field lines connecting Earth to the Sun at the onset times of 15 impulsive SEP bursts, comparing the foot points of these field lines with the locations of surface events believed to be responsible for the SEP bursts. We find the WSA/ENLIL model performance is no better than the simplest spiral model, and the principal source of error is the model's inability to reproduce sufficient low-latitude open flux. This may be due to the model's use of static synoptic magnetograms, which fail to account for transient activity in the low corona, during which reconnection events believed to initiate the SEP acceleration may contribute short-lived open flux at low latitudes. Time-dependent coronal models incorporating these transient events may be needed to significantly improve Earth/Sun field line forecasting.

Modelling the line-of-sight contribution in substructure lensing

NASA Astrophysics Data System (ADS)

Despali, Giulia; Vegetti, Simona; White, Simon D. M.; Giocoli, Carlo; van den Bosch, Frank C.

2018-04-01

We investigate how Einstein rings and magnified arcs are affected by small-mass dark-matter haloes placed along the line of sight to gravitational lens systems. By comparing the gravitational signature of line-of-sight haloes with that of substructures within the lensing galaxy, we derive a mass-redshift relation that allows us to rescale the detection threshold (i.e. lowest detectable mass) for substructures to a detection threshold for line-of-sight haloes at any redshift. We then quantify the line-of-sight contribution to the total number density of low-mass objects that can be detected through strong gravitational lensing. Finally, we assess the degeneracy between substructures and line-of-sight haloes of different mass and redshift to provide a statistical interpretation of current and future detections, with the aim of distinguishing between cold dark matter and warm dark matter. We find that line-of-sight haloes statistically dominate with respect to substructures, by an amount that strongly depends on the source and lens redshifts, and on the chosen dark-matter model. Substructures represent about 30 percent of the total number of perturbers for low lens and source redshifts (as for the SLACS lenses), but less than 10 per cent for high-redshift systems. We also find that for data with high enough signal-to-noise ratio and angular resolution, the non-linear effects arising from a double-lens-plane configuration are such that one is able to observationally recover the line-of-sight halo redshift with an absolute error precision of 0.15 at the 68 per cent confidence level.

The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra

NASA Astrophysics Data System (ADS)

Gonçalves, A. C.; Serote Roos, M.

2004-01-01

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (\\cite{March96}) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources. Based on observations collected at the Multiple Mirror Telescope on Mt. Hopkins. Full Fig. 1 is only available in electronic form at http://www.edpsciences.org

Chern-Simons theory with Wilson lines and boundary in the BV-BFV formalism

NASA Astrophysics Data System (ADS)

Alekseev, Anton; Barmaz, Yves; Mnev, Pavel

2013-05-01

We consider the Chern-Simons theory with Wilson lines in 3D and in 1D in the BV-BFV formalism of Cattaneo-Mnev-Reshetikhin. In particular, we allow for Wilson lines to end on the boundary of the space-time manifold. In the toy model of 1D Chern-Simons theory, the quantized BFV boundary action coincides with the Kostant cubic Dirac operator which plays an important role in representation theory. In the case of 3D Chern-Simons theory, the boundary action turns out to be the odd (degree 1) version of the BF model with source terms for the B field at the points where the Wilson lines meet the boundary. The boundary space of states arising as the cohomology of the quantized BFV action coincides with the space of conformal blocks of the corresponding WZW model.

Evaluation of upwelling infrared radiance from earth's atmosphere

NASA Technical Reports Server (NTRS)

Gupta, S. K.; Tiwari, S. N.

1975-01-01

Basic equations for calculating the upwelling atmospheric radiation are presented which account for various sources of radiation coming out at the top of the atmosphere. The theoretical formulation of the transmittance models (line-by-line and quasi-random band model) and the computational procedures used for the evaluation of the transmittance and radiance are discussed in detail. By employing the Lorentz line-by-line and quasi-random computer programs, model calculations were made to determine the upwelling radiance and signal change in the wave number interval of CO fundamental band. These results are useful in determining the effects of different interfering molecules, water vapor profiles, ground temperatures, and ground emittances on the upwelling radiance and signal change. This information is of vital importance in establishing the feasibility of measuring the concentrations of pollutants in the atmosphere from a gas filter correlation instrument flown on an aircraft or mounted on a satellite.

ON THE IONIZATION OF LUMINOUS WMAP SOURCES IN THE GALAXY: CONSTRAINTS FROM He RECOMBINATION LINE OBSERVATIONS WITH THE GBT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roshi, D. Anish; Plunkett, Adele; Rosero, Viviana

2012-04-10

Murray and Raham used the Wilkinson Microwave Anisotropy Probe (WMAP) free-free foreground emission map to identify diffuse ionized regions (DIRs) in the Galaxy. It has been found that the 18 most luminous WMAP sources produce more than half of the total ionizing luminosity of the Galaxy. We observed radio recombination lines (RRLs) toward the luminous WMAP source G49.75-0.45 with the Green Bank Telescope near 1.4 GHz. Hydrogen RRL is detected toward the source but no helium line is detected, implying that n{sub He{sup +}}/n{sub H{sup +}}< 0.024. This limit puts severe constraint on the ionizing spectrum. The total ionizing luminositymore » of G49 (3.05 Multiplication-Sign 10{sup 51} s{sup -1}) is {approx}2.8 times the luminosity of all radio H II regions within this DIR and this is generally the case for other WMAP sources. Murray and Rahman propose that the additional ionization is due to massive clusters ({approx}7.5 Multiplication-Sign 10{sup 3} M{sub Sun} for G49) embedded in the WMAP sources. Such clusters should produce enough photons with energy {>=}24.6 eV to fully ionize helium in the DIR. Our observations rule out a simple model with G49 ionized by a massive cluster. We also considered 'leaky' H II region models for the ionization of the DIR, suggested by Lockman and Anantharamaiah, but these models also cannot explain our observations. We estimate that the helium ionizing photons need to be attenuated by {approx}>10 times to explain the observations. If selective absorption of He ionizing photons by dust is causing this additional attenuation, then the ratio of dust absorption cross sections for He and H ionizing photons should be {approx}>6.« less

AGN Space Telescope and Optical Reverberation Mapping Project. IV. Velocity-Delay Mapping of Broad Emission Lines in NGC 5548

NASA Astrophysics Data System (ADS)

Horne, Keith D.; Agn Storm Team

2015-01-01

Two-dimensional velocity-delay maps of AGN broad emission line regions can be recovered by modelling observations of reverberating emission-line profiles on the assumption that the line profile variations are driven by changes in ionising radiation from a compact source near the black hole. The observable light travel time delay resolves spatial structure on iso-delay paraboloids, while the doppler shift resolves kinematic structure along the observer's line-of-sight. Velocity-delay maps will be presented and briefly discussed for the Lyman alpha, CIV and Hbeta line profiles based on the HST and ground-based spectrophotometric monitoring of NGC 5548 during the 2014 AGN STORM campaign.

Iron K Lines from Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Kallman, T. R.; Meszaros, P.; Rees, M. J.

2003-01-01

We present models for reprocessing of an intense flux of X-rays and gamma rays expected in the vicinity of gamma ray burst sources. We consider the transfer and reprocessing of the energetic photons into observable features in the X-ray band, notably the K lines of iron. Our models are based on the assumption that the gas is sufficiently dense to allow the microphysical processes to be in a steady state, thus allowing efficient line emission with modest reprocessing mass and elemental abundances ranging from solar to moderately enriched. We show that the reprocessing is enhanced by down-Comptonization of photons whose energy would otherwise be too high to absorb on iron, and that pair production can have an effect on enhancing the line production. Both "distant" reprocessors such as supernova or wind remnants and "nearby" reprocessors such as outer stellar envelopes can reproduce the observed line fluxes with Fe abundances 30-100 times above solar, depending on the incidence angle. The high incidence angles required arise naturally only in nearby models, which for plausible values can reach Fe line to continuum ratios close to the reported values.

40 CFR Appendix I to Part 60 - Removable Label and Owner's Manual

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES (CONTINUED) Pt. 60, App. I Appendix I to Part... label): • Manufacturer name (upper left hand corner, • Model name/number (upper left hand corner, • The... equipped wood heaters the 3.0 inch line shall be labeled “0” on the left end of the line (centered below...

40 CFR Appendix I to Part 60 - Removable Label and Owner's Manual

Code of Federal Regulations, 2010 CFR

2010-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES (CONTINUED) Pt. 60, App. I Appendix I to Part... label): • Manufacturer name (upper left hand corner, • Model name/number (upper left hand corner, • The... equipped wood heaters the 3.0 inch line shall be labeled “0” on the left end of the line (centered below...

SPECTRAL LINE DE-CONFUSION IN AN INTENSITY MAPPING SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Yun-Ting; Bock, James; Bradford, C. Matt

2016-12-01

Spectral line intensity mapping (LIM) has been proposed as a promising tool to efficiently probe the cosmic reionization and the large-scale structure. Without detecting individual sources, LIM makes use of all available photons and measures the integrated light in the source confusion limit to efficiently map the three-dimensional matter distribution on large scales as traced by a given emission line. One particular challenge is the separation of desired signals from astrophysical continuum foregrounds and line interlopers. Here we present a technique to extract large-scale structure information traced by emission lines from different redshifts, embedded in a three-dimensional intensity mapping data cube.more » The line redshifts are distinguished by the anisotropic shape of the power spectra when projected onto a common coordinate frame. We consider the case where high-redshift [C ii] lines are confused with multiple low-redshift CO rotational lines. We present a semi-analytic model for [C ii] and CO line estimates based on the cosmic infrared background measurements, and show that with a modest instrumental noise level and survey geometry, the large-scale [C ii] and CO power spectrum amplitudes can be successfully extracted from a confusion-limited data set, without external information. We discuss the implications and limits of this technique for possible LIM experiments.« less

Signatures of Slow Solar Wind Streams from Active Regions in the Inner Corona

NASA Astrophysics Data System (ADS)

Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.; Berghmans, D.

2013-08-01

The identification of solar-wind sources is an important question in solar physics. The existing solar-wind models ( e.g., the Wang-Sheeley-Arge model) provide the approximate locations of the solar wind sources based on magnetic field extrapolations. It has been suggested recently that plasma outflows observed at the edges of active regions may be a source of the slow solar wind. To explore this we analyze an isolated active region (AR) adjacent to small coronal hole (CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer observations showed two compact outflow regions in the corona. Coronal rays were observed above the active-region coronal hole (ARCH) region on the eastern limb on 31 July by STEREO-A/EUVI and at the western limb on 7 August by CORONAS- Photon/TESIS telescopes. In both cases the coronal rays were co-aligned with open magnetic-field lines given by the potential field source surface model, which expanded into the streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind, and STEREO-A confirmed the identification of the ARCH as a source region of the slow solar wind. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, E. L.; Hammett, G. W.; Stoltzfus-Dueck, T.

Here, five-dimensional gyrokinetic continuum simulations of electrostatic plasma turbulence in a straight, open-field-line geometry have been performed using a full- discontinuous-Galerkin approach implemented in the Gkeyll code. While various simplifications have been used for now, such as long-wavelength approximations in the gyrokinetic Poisson equation and the Hamiltonian, these simulations include the basic elements of a fusion-device scrape-off layer: localised sources to model plasma outflow from the core, cross-field turbulent transport, parallel flow along magnetic field lines, and parallel losses at the limiter or divertor with sheath-model boundary conditions. The set of sheath-model boundary conditions used in the model allows currentsmore » to flow through the walls. In addition to details of the numerical approach, results from numerical simulations of turbulence in the Large Plasma Device, a linear device featuring straight magnetic field lines, are presented.« less

DeltaSA tool for source apportionment benchmarking, description and sensitivity analysis

NASA Astrophysics Data System (ADS)

Pernigotti, D.; Belis, C. A.

2018-05-01

DeltaSA is an R-package and a Java on-line tool developed at the EC-Joint Research Centre to assist and benchmark source apportionment applications. Its key functionalities support two critical tasks in this kind of studies: the assignment of a factor to a source in factor analytical models (source identification) and the model performance evaluation. The source identification is based on the similarity between a given factor and source chemical profiles from public databases. The model performance evaluation is based on statistical indicators used to compare model output with reference values generated in intercomparison exercises. The references values are calculated as the ensemble average of the results reported by participants that have passed a set of testing criteria based on chemical profiles and time series similarity. In this study, a sensitivity analysis of the model performance criteria is accomplished using the results of a synthetic dataset where "a priori" references are available. The consensus modulated standard deviation punc gives the best choice for the model performance evaluation when a conservative approach is adopted.

Analysis of carbon monoxide (CO) with Delhi Finite Line Source (DFLS) in MT Haryono Street, Medan City

NASA Astrophysics Data System (ADS)

Turmuzi, M.; Suryati, I.; Mashaly, E. T.; Batubara, F.

2018-02-01

One source to decrease urban air ambient quality is transportation sector. Important pollutants are released by gas emissions from vehicles are carbon monoxide (CO), hydrocarbons (HC), nitrogen dioxide (NO2), particulate matter and others. The presence of CO pollutants in the ambient air can be predicted by modeling air quality. This study aims to estimate CO concentration resulting from transportation activities using Delhi Finite Line Source (DFLS) model, comparing CO prediction using a DFLS model with CO observation in the field, and determine the suitability of the DFLS model application on the MT Haryono street in Medan City. Research was conducted for 3 days at two sample points with frequency twice daily. Based on research results, the range of CO concentration from observation between 22.903 μg/m3 - 27.484 μg/m3. CO observation is still below the ambient air quality standard. According to the DFLS calculations, the range of CO concentration between 1.499 μg/m3- 2.051 μg/m3. The calculation index of agreement (IOA) validation test obtained value of d = 0.22. The DFLS model is not suitable to be applied on MT Haryono street because many factors affected such as wind direction and wind velocity, ambient air temperature and humidity

Physical conditions of the interstellar medium in high-redshift submillimetre bright galaxies

NASA Astrophysics Data System (ADS)

Yang, Chentao

2017-12-01

The discovery of a population of high- redshift dust-obscured submillimeter galaxies (SMGs) from ground-based submm cameras has revolutionised our understanding of galaxy evolution and star formation in extreme conditions. They are the strongest starbursts in the Universe approaching the Eddington limit and are believed to be the progenitors of the most massive galaxies today. However, theoretical models of galaxy evolution have even been challenged by a large number of detections of high-redshift SMGs. A very few among them are gravitationally lensed by an intervening galaxy. Recent wide-area extragalactic surveys have discovered hundreds of such strongly lensed SMGs, opening new exciting opportunities for observing the interstellar medium in these exceptional objects. We have thus carefully selected a sample of strongly gravitational lensed SMGs based on the submillimeter flux limit from the Herschel-ATLAS sample. Using IRAM telescopes, we have built a rich H2O-line-detected sample of 16 SMGs. We found a close-to-linear tight correlation between the H2O line and total infrared luminosity. This indicates the importance of far-IR pumping to the excitation of the H2O lines. Using a far-IR pumping model, we have derived the physical properties of the H2O gas and the dust. We showed that H2O lines trace a warm dense gas that may be closely related to the active star formation. Along with the H2O lines, several H2O+ lines have also been detected in three of our SMGs. We also find a tight correlation between the luminosity of the lines of H2O and H2O+ from local ULIRGs to high-redshift SMGs. The flux ratio between H2O+ and H2O suggests that cosmic rays from strong star forming activities are possibly driving the related oxygen chemistry. Another important common molecular gas tracer is the CO line. We have observed multiple transitions of the CO lines in each of our SMGs with IRAM 30m telescope. By analysing the CO line profile, we discovered a significant differential lensing effect that might cause underestimation of the linewidth by a factor of 2. Using LVG modelling and fitting the multi-J CO fluxes via a Bayesian approach, we derived gas densities and temperature, and CO column density per unit velocity gradient. We then found a correlation between the gas thermal pressure and the star formation efficiency. We have also studied the global properties of the molecular gas and its relationship with star formation. We have derived the gas to dust mass ratio and the gas depletion time, they show no difference compared with other SMGs. With the detections of atomic carbon lines in our SMGs, we extended the local linear correlation between the CO and CI line luminosity. Finally, we compared the linewidths of the CO and H2O emission line, which agree very well with each other. This suggests that the emitting regions of these two molecules are likely to be co-spatially located. In order to understand the properties of molecular emission in high-redshift SMGs, and more generally, the structure and the dynamical properties of these galaxies, it is crucial to acquire high-resolution images. We thus observed two of our brightest sources with ALMA and NOEMA interferometers using their high spatial resolution configuration. These images have allowed us to reconstruct the intrinsic morphology of the sources. We compared the CO, H2O and dust emission. The cold dust emission has a smaller size compared with the CO and H2O gas, while the latter two are similar in size. By fitting the dynamical model to the CO data of the source, we have shown that the source can be modelled with a rotating disk. We derived the projected dynamical mass and the effective radius of those sources. With the future NOEMA and ALMA, we will be able to extend such kind of observations to a larger sample lensed SMGs and even to unlensed SMGs, to study various gas tracers, and to understand the physical conditions of the ISM and their relation to the star formation.

Contaminant dispersal in bounded turbulent shear flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, J.M.; Bernard, P.S.; Chiang, K.F.

The dispersion of smoke downstream of a line source at the wall and at y{sup +} = 30 in a turbulent boundary layer has been predicted with a non-local model of the scalar fluxes {bar u}c and {bar v}c. The predicted plume from the wall source has been compared to high Schmidt number experimental measurements using a combination of hot-wire anemometry to obtain velocity component data synchronously with concentration data obtained optically. The predicted plumes from the source at y{sup +} = 30 and at the wall also have been compared to a low Schmidt number direct numerical simulation. Nearmore » the source, the non-local flux models give considerably better predictions than models which account solely for mean gradient transport. At a sufficient distance downstream the gradient models gives reasonably good predictions.« less

Microlensing of an extended source by a power-law mass distribution

NASA Astrophysics Data System (ADS)

Congdon, Arthur B.; Keeton, Charles R.; Osmer, S. J.

2007-03-01

Microlensing promises to be a powerful tool for studying distant galaxies and quasars. As the data and models improve, there are systematic effects that need to be explored. Quasar continuum and broad-line regions may respond differently to microlensing due to their different sizes; to understand this effect, we study microlensing of finite sources by a mass function of stars. We find that microlensing is insensitive to the slope of the mass function but does depend on the mass range. For negative-parity images, diluting the stellar population with dark matter increases the magnification dispersion for small sources and decreases it for large sources. This implies that the quasar continuum and broad-line regions may experience very different microlensing in negative-parity lensed images. We confirm earlier conclusions that the surface brightness profile and geometry of the source have little effect on microlensing. Finally, we consider non-circular sources. We show that elliptical sources that are aligned with the direction of shear have larger magnification dispersions than sources with perpendicular alignment, an effect that becomes more prominent as the ellipticity increases. Elongated sources can lead to more rapid variability than circular sources, which raises the prospect of using microlensing to probe source shape.

The effect of intermediate-scale motions on line formation. [sawtooth and sine motions in solar atmosphere

NASA Technical Reports Server (NTRS)

Shine, R. A.

1975-01-01

The problem of LTE and non-LTE line formation in the presence of nonthermal velocity fields with geometric scales between the microscopic and macroscopic limits is investigated in the cases of periodic sinusoidal and sawtooth waves. For a fixed source function (the LTE case), it is shown that time-averaged line profiles progress smoothly from the microscopic to the macroscopic limits as the geometric scale of the motions increases, that the sinusoidal motions produce symmetric time-averaged profiles, and that the sawtooth motions cause a redshift. In several idealized non-LTE cases, it is found that intermediate-scale velocity fields can significantly increase the surface source functions and line-core intensities. Calculations are made for a two-level atom in an isothermal atmosphere for a range of velocity scales and non-LTE coupling parameters and also for a two-level atom and a four-level representation of Na I line formation in the Harvard-Smithsonian Reference Atmosphere (1971) solar model. It is found that intermediate-scale velocity fields in the solar atmosphere could explain the central intensities of the Na I D lines and other strong absorption lines without invoking previously suggested high electron densities.

On modeling the sound propagation through a lined duct with a modified Ingard-Myers boundary condition

NASA Astrophysics Data System (ADS)

Yang, Cheng; Fang, Yi; Zhao, Chao; Zhang, Xin

2018-06-01

A duct acoustics model is an essential component of an impedance eduction technique and its computation cost determines the impedance measurement efficiency. In this paper, a model is developed for the sound propagation through a lined duct carrying a uniform mean flow. In contrast to many existing models, the interface between the liner and the duct field is defined with a modified Ingard-Myers boundary condition that takes account of the effect of the boundary layer above the liner. A mode-matching method is used to couple the unlined and lined duct segments for the model development. For the lined duct segment, the eigenvalue problem resulted from the modified boundary condition is solved by an integration scheme which, on the one hand, allows the lined duct modes to be computed in an efficient manner, and on the other hand, orders the modes automatically. The duct acoustics model developed from the solved lined duct modes is shown to converge more rapidly than the one developed from the rigid-walled duct modes. Validation against the experiment data in the literature shows that the proposed model is able to predict more accurately the liner performance measured by the two-source method. This, however, cannot be made by a duct acoustics model associated with the conventional Ingard-Myers boundary condition. The proposed model has the potential to be integrated into an impedance eduction technique for more reliable liner measurement.

Carbon influx studies in the main chamber of ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Pütterich, T.; Dux, R.; Gafert, J.; Kallenbach, A.; Neu, R.; Pugno, R.; Yoon, S. W.; ASDEX Upgrade Team

2003-10-01

Carbon sources in the main chamber of ASDEX Upgrade, especially the 12 guard limiters at the low field side (LFS), were determined spectroscopically using recently installed lines of sight. Absolute photon fluxes were measured for spectral lines in the visible wavelength range referring to all spin systems of C+1 and C+2. A simple transport model for carbon enabled the simulation of the radial distribution of carbon radiation and the determination of the effective inverse photon efficiency, which was used for the evaluation of ion fluxes. The model also predicts the fraction of eroded particles that are transported out of the plasma before further ionization occurs. Comparison of the calculated losses with measurements showed good agreement in L-mode cases, whereas in H-mode cases the CIII/CII radiation ratio was too high by a factor 1.5. The contribution of each spin system to the ion flux was independently measured. For C+1 and C+2 the spin system distribution was found to be close to equilibrium. The line-of-sight-integrated photon fluxes were spatially separated for many lines of sight by Zeeman-analysis and differential measurements. This allowed us to determine the total influx from the high field side and LFS. Surprisingly, the carbon source at the inner heatshield was larger than the carbon influx from the limiter source at the LFS. This is very pronounced for the H-mode case investigated, where 60-80% of the carbon atoms emerge from the heatshield. This source is due to recycling or re-erosion of carbon, which probably originates from the limiters, because ap85% of the heatshield area consisted of tungsten coated tiles.

A Gemini view of the galaxy cluster RXC J1504-0248: insights on the nature of the central gaseous filaments

NASA Astrophysics Data System (ADS)

Soja, A. C.; Sodré, L., Jr.; Monteiro-Oliveira, R.; Cypriano, E. S.; Lima Neto, G. B.

2018-03-01

We revisit the galaxy cluster RXC J1504-0248, a remarkable example of a structure with a strong cool core in a near redshift (z = 0.216). We performed a combined analysis using photometric and spectroscopic data obtained at Gemini South Telescope. We estimated the cluster mass through gravitational lensing, obtaining M200 = 5.3 ± 0.4 × 1014h_{70}^{-1} M⊙ within R200 = 1.56 ± 0.04 h^{-1}_{70} Mpc, in agreement with a virial mass estimate. This cluster presents a prominent filamentary structure associated to its BCG, located mainly along its major axis and aligned with the X-ray emission. A combined study of three emission line diagnostic diagrams has shown that the filament emission falls in the so-called transition region of these diagrams. Consequently, several ionizing sources should be playing an meaningful role. We have argued that old stars, often invoked to explain LINER emission, should not be the major source of ionization. We have noticed that most of the filamentary emission has line ratios consistent with the shock excitation limits obtained from shock models. We also found that line fluxes are related to gas velocities (here estimated from line widths) by power-laws with slopes in the range expected from shock models. These models also show, however, that only ˜10% of Hα luminosity can be explained by shocks. We conclude that shocks probably associated to the cooling of the intracluster gas in a filamentary structure may indeed be contributing to the filament nebular emission, but can not be the major source of ionizing photons.

A Relation between the Mid-Infrared [Ne v] 14.3 Micrometers and [Ne III] 15.6 Micrometer Lines in Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Gorjian, V.; Cleary, K.; Werner, M. W.; Lawrence, C. R.

2007-01-01

We present a strong correlation between the [Ne v] 14.3 mm and [Ne III] 15.6 mm emission lines arising from the narrow-line regions (NLRs) of active galactic nuclei (AGNs), spanning 4 orders of magnitude in luminosity. The data are compiled primarily from Spitzer Space Telescope observations of nearby Seyfert galaxies (median z p 0.01) and 3C radio sources (median z p 0.52). This correlation is consistent with earlier studies in the optical/UV bands showing that line ratios arising in the NLRs are remarkably constant across AGNs. We also show that the correlation allows only a very narrow range in ionization parameter for simple photoionization models. The observed correlation will place tight constraints on alternative models, which predict constant line ratios over a broader range in ionization parameter.

X-ray emission from galaxies - The distribution of low-luminosity X-ray sources in the Galactic Centre region

NASA Astrophysics Data System (ADS)

Heard, Victoria; Warwick, Robert

2012-09-01

We report a study of the extended X-ray emission observed in the Galactic Centre (GC) region based on archival XMM-Newton data. The GC diffuse emission can be decomposed into three distinct components: the emission from low-luminosity point sources; the fluorescence of (and reflection from) dense molecular material; and soft (kT ~1 keV), diffuse thermal plasma emission most likely energised by supernova explosions. Here, we examine the emission due to unresolved point sources. We show that this source component accounts for the bulk of the 6.7-keV and 6.9-keV line emission. We fit the surface brightness distribution evident in these lines with an empirical 2-d model, which we then compare with a prediction derived from a 3-d mass model for the old stellar population in the GC region. We find that the X-ray surface brightness declines more rapidly with angular offset from Sgr A* than the mass-model prediction. One interpretation is that the X-ray luminosity per solar mass characterising the GC source population is increasing towards the GC. Alternatively, some refinement of the mass-distribution within the nuclear stellar disc may be required. The unresolved X-ray source population is most likely dominated by magnetic CVs. We use the X-ray observations to set constraints on the number density of such sources in the GC region. Our analysis does not support the premise that the GC is pervaded by very hot (~ 7.5 keV) thermal plasma, which is truly diffuse in nature.

A young bipolar outflow from IRAS15398-3359

NASA Astrophysics Data System (ADS)

Bjerkeli, Per; Jørgensen, Jes K.

2015-08-01

The Class 0 protostar IRAS 15398-3359 is located in the Lupus I cloud at a distance of 155 pc. The source is known to harbour a molecular outflow, but the region has not attracted much interest until recently. IRAS 15398 is known to show interesting chemical signatures and being one of the very nearby, young outflow sources makes it an excellent target for detailed studies of the gas kinematics of different species.We present observations of several molecular species, carried out with the Submillimeter Array and ALMA, towards the IRAS 15398 outflow. The analysis of CO emission show obvious signs of episodic mass ejections, with a dynamical time scale between the knots in the jet, of the order 100 years. This is consistent with recent ALMA results where luminosity outbursts are estimated to occur on similar time-scales. The physical properties of the outflow, such as mass, momentum, momentum rate, mechanical luminosity, kinetic energy and mass-loss rate are estimated at relatively low values. We argue that this source is of a very young age, possibly younger than ~1000 years. This is consistent with recent studies of the kinematics of the inner envelope/disk. The observed line profiles were compared to full 3D radiative transfer models of the source, constructed with the Line Modelling Engine (LIME). The observed line shapes can only be understood when considering several distinctly different physical components, viz. the outflow cavity, the infalling envelope and the surrounding cloud material. This allows us to put quantitative constraints on the kinematics of the material close to the central source.

Theoretical and measured electric field distributions within an annular phased array: consideration of source antennas.

PubMed

Zhang, Y; Joines, W T; Jirtle, R L; Samulski, T V

1993-08-01

The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory. This more detailed model yields better agreement with the measured field patterns, reducing the rms discrepancy by a factor of about 6 (from approximately 23 to 4%) in the central region of interest where the SEM is within 25% of the maximum. We conclude that accurate modeling of source current distributions is important for determining SEM distributions associated with such heating devices.

Development of a composite line source emission model for traffic interrupted microenvironments and its application in particle number emissions at a bus station

NASA Astrophysics Data System (ADS)

Wang, Lina; Jayaratne, Rohan; Heuff, Darlene; Morawska, Lidia

A composite line source emission (CLSE) model was developed to specifically quantify exposure levels and describe the spatial variability of vehicle emissions in traffic interrupted microenvironments. This model took into account the complexity of vehicle movements in the queue, as well as different emission rates relevant to various driving conditions (cruise, decelerate, idle and accelerate), and it utilised multi-representative segments to capture the accurate emission distribution for real vehicle flow. Hence, this model was able to quickly quantify the time spent in each segment within the considered zone, as well as the composition and position of the requisite segments based on the vehicle fleet information, which not only helped to quantify the enhanced emissions at critical locations, but it also helped to define the emission source distribution of the disrupted steady flow for further dispersion modelling. The model then was applied to estimate particle number emissions at a bi-directional bus station used by diesel and compressed natural gas fuelled buses. It was found that the acceleration distance was of critical importance when estimating particle number emission, since the highest emissions occurred in sections where most of the buses were accelerating and no significant increases were observed at locations where they idled. It was also shown that emissions at the front end of the platform were 43 times greater than at the rear of the platform. Although the CLSE model is intended to be applied in traffic management and transport analysis systems for the evaluation of exposure, as well as the simulation of vehicle emissions in traffic interrupted microenvironments, the bus station model can also be used for the input of initial source definitions in future dispersion models.

RLINE: Re-formulation of Plume Spread for Near-Surface Dispersion

EPA Science Inventory

Recent concerns about effects of automobile emissions on the health of people living close to roads have motivated an examination of models to estimate dispersion in the surface boundary layer. During the development of a new line source dispersion model, RLINE (Snyder et al., 20...

The influence of H2O line blanketing on the spectra of cool dwarf stars

NASA Technical Reports Server (NTRS)

Allard, F.; Hauschildt, P. H.; Miller, S.; Tennyson, J.

1994-01-01

We present our initial results of model atmosphere calculations for cool M dwarfs using an opacity sampling method and a new list of H2O lines. We obtain significantly improved fits to the infrared spectrum of the M dwarf VB10 when compared to earlier models. H2O is by far the dominant opacity source in cool stars. To illustrate this, we show the Rosseland mean of the total extinction under various assumptions. Our calculations demonstrate the importance of a good treatment of the water opacities in cool stars and the improvements possible by using up-to-date data for the water line absorption.

Atomic Data in X-Ray Astrophysics

NASA Technical Reports Server (NTRS)

Brickhouse, N. S.

2000-01-01

With the launches of the Chandra X-ray Observatory (CXO) and the X-ray Multimirror Mission (XMM) and the upcoming launch of the Japanese mission ASTRO-E, high resolution X-ray spectroscopy of cosmic sources has begun. Early, deep observations of three stellar coronal sources will provide not only invaluable calibration data, but will also give us benchmarks for the atomic data under collisional equilibrium conditions. Analysis of the Chandra X-ray Observatory data, and data from other telescopes taken simultaneously, for these stars is ongoing as part of the Emission Line Project. Goals of the Emission Line Project are: (1) to determine and verify accurate and robust diagnostics and (2) to identify and prioritize issues in fundamental spectroscopy which will require further theoretical and/or laboratory work. The Astrophysical Plasma Emission Database will be described in some detail, as it is introducing standardization and flexibility into X-ray spectral modeling. Spectral models of X-ray astrophysical plasmas can be generally classified as dominated by either collisional ionization or by X-ray photoionization. While the atomic data needs for spectral models under these two types of ionization are significantly different, there axe overlapping data needs, as I will describe. Early results from the Emission Line Project benchmarks are providing an invaluable starting place, but continuing work to improve the accuracy and completeness of atomic data is needed. Additionally, we consider the possibility that some sources will require that both collisional ionization and photoionization be taken into account, or that time-dependent ionization be considered. Thus plasma spectral models of general use need to be computed over a wide range of physical conditions.

Water in Massive protostellar objects: first detection of THz water maser and water inner abundance.

NASA Astrophysics Data System (ADS)

Herpin, Fabrice

2014-10-01

The formation massive stars is still not well understood. Despite numerous water line observations with Herschel telescope, over a broad range of energies, in most of the observed sources the WISH-KP (Water In Star-forming regions with Herschel, Co-PI: F. Herpin) observations were not able to trace the emission from the hot core. Moreover, water maser model predict that several THz water maser should be detectable in these objects. We aim to detect for the first time the THz maser lines o-H2O 8(2,7)- 7(3,4) at 1296.41106 GHz and p-H2O 7(2,6)- 6(3,3) at 1440.78167 GHz as predicted by the model. We propose two sources for a northern flight as first priority and two other sources for a possible southern flight. This will 1) constrain the maser theory, 2) constrain the physical conditions and water abundance in the inner layers of the prostellar environnement. In addition, we will use the p-H2O 3(3,1)- 4(0,4) thermal line at 1893.68651 GHz (L2 channel) in order to probe the physical conditions and water abundance in the inner layers of the prostellar objects where HIFI-Herschel has partially failed.

The complexity of the coronal line region in AGNs: Gas-jet interactions and outflows revealed by NIR spectroscopy

NASA Astrophysics Data System (ADS)

Rodríguez-Ardila, Alberto; Prieto, Almudena; Mazzalay, Ximena

2016-08-01

Apart from the classical broad line region (BLR) at small core distances, and the extended classical narrow-line region (NLR), a subset of active galactic nuclei (AGN) show, in their spectra, lines from very highly ionised atoms, known as Coronal lines (CLs). The precise nature and origin of these CLs remain uncertain. Advances on this matter include the determination of the size and morphology of the CLR by means of optical HST and ground-based AO imaging/spectroscopy in a few AGNs. The results indicate CLRs with sizes varying from compact (~30 pc) to extended (~200 pc) emission and aligned preferentially with the direction of the lower ionisation cones seen in these sources. In this talk, we present results of a pioneering work aimed at studying the CLR in the near-infrared region on a selected sample of nearby AGNs. The excellent angular resolution of the data allowed us to resolve and map the extension of the coronal line gas and compare it to that emitting low- and mid-ionization lines. In most cases, the very good match between the radio emission and the CLR suggest that at least part of the high-ionization gas is jet-driven. Results from photoionization models where the central engine is the only source of energy input strongly fail at reproducing the observed line ratios, mainly at distances larger than 60 pc from the centre. We discuss here other processes that should be at work to enhance this energetic emission and suggest that the presence of coronal lines in AGNs is an unambiguous signature of feedback processes in these sources.

The Properties and the Evolution of the Highly Ionized Gas in MR 2251-178

NASA Technical Reports Server (NTRS)

Kaspi, Shai; Netzer, hagai; Chelouche, Doron; George, Ian M.; Nandra, Kirpal; Turner, T. J.

2004-01-01

We present the first XMM-Newton observations of the radio-quiet quasar MR 2251-178 obtained in 2000 and 2002. The EPIC-pn spectra show a power-law continuum with a slope of Gamma = 1.6 at high energies absorbed by at least two warm absorbers (WAs) intrinsic to the source. The underlying continuum in the earlier observation shows a soft excess at low X-ray energies which can be modeled as an additional power-law with Gamma = 2.9. The spectra also show a weak narrow iron K alpha emission line. The high-resolution grating spectrum obtained in 2002 shows emission lines from N VI, O VII, O VIII, Ne IX, and Ne X, as well as absorption lines from the low-ionization ions of O III, O IV, and O V, and other confirmed and suspected weaker absorption lines. The O III - O V lines are consistent with the properties of the emission line gas observed as extended optical (O III) emission in this source. The signal-to-noise of the 2000 grating data is too low to detect any lines. We suggest a model for the high-resolution spectrum which consist of two or three warm-absorber (WA) components. The two-components model has a high-ionization WA with a column density of 10(exp 21.5)-10 (exp 21.8) sq cm and a low-ionization absorber with a column density of 10(exp 20.3) sq cm. In the three-components model we add a lower ionization component that produces the observed iron M-shell absorption lines. We investigate the spectral variations in MR 2251-178 over a period of 8.5 years using data from ASCA, BeppoSAX, and XMM-Newton. All X-ray observations can be fitted with the above two power laws and the two absorbers. The observed luminosity variations seems to correlate with variations in the soft X-ray continuum. The 8.5 year history of the source suggests a changing X-ray absorber due to material that enters and disappears from the line-of-sight on timescales of several months. We also present, for the first time, the entire FUSE spectrum of MR 2251-178. We detect emission from N III, C III, and O VI and at least 4 absorption systems in C III, H I, and O VI, one at -580 km/s and at least 3 others which are blended together and form a wide trough covering the velocity range of 0 to -500 km/s. The general characteristics of the UV and X-ray absorbers are consistent with an origin in the same gas.

The Properties and Evolution of the Highly Ionized Gas in MR 2251-178

NASA Astrophysics Data System (ADS)

Kaspi, Shai; Netzer, Hagai; Chelouche, Doron; George, Ian M.; Nandra, Kirpal; Turner, T. J.

2004-08-01

We present the first XMM-Newton observations of the radio-quiet quasar MR 2251-178 obtained in 2000 and 2002. The EPIC pn spectra show a power-law continuum with a slope of Γ=1.6 at high energies absorbed by at least two warm absorbers (WAs) intrinsic to the source. The underlying continuum in the earlier observation shows a ``soft excess'' at low X-ray energies, which can be modeled as an additional power law with Γ=2.9. The spectra also show a weak narrow iron Kα emission line. The high-resolution grating spectrum obtained in 2002 shows emission lines from N VI, O VII, O VIII, Ne IX, and Ne X, as well as absorption lines from the low-ionization ions of O III, O IV, and O V, and other confirmed and suspected weaker absorption lines. The O III-O V lines are consistent with the properties of the emission-line gas observed as extended optical [O III] emission in this source. The signal-to-noise ratio of the 2000 grating data is too low to detect any lines. We suggest a model for the high-resolution spectrum that consists of two or three WA components. The two-component model has a high-ionization WA with a column density of 1021.5-1021.8 cm-2 and a low-ionization absorber with a column density of 1020.3 cm-2. In the three-component model we add a lower ionization component that produces the observed iron M shell absorption lines. We investigate the spectral variations in MR 2251-178 over a period of 8.5 yr using data from ASCA, BeppoSAX, and XMM-Newton. All X-ray observations can be fitted with the above two power laws and the two absorbers. The observed luminosity variations seem to correlate with variations in the soft X-ray continuum. The 8.5 yr history of the source suggests a changing X-ray absorber due to material that enters and disappears from the line of sight on timescales of several months. We also present, for the first time, the entire Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of MR 2251-178. We detect emission from N III, C III, and O VI and at least four absorption systems in C III, H I, and O VI, one at -580 km s-1 and at least three others that are blended together and form a wide trough covering the velocity range of 0 to -500 km s-1. The general characteristics of the UV and X-ray absorbers are consistent with an origin in the same gas.

Toward Understanding the Fanaroff-Riley Dichotomy in Radio Source Morphology and Power

NASA Astrophysics Data System (ADS)

Baum, Stefi A.; Zirbel, Esther L.; O'Dea, Christopher P.

1995-09-01

In Paper I we presented the results of a study of the interrelationships between host galaxy magnitude, optical line luminosity, and radio luminosity in a large sample of Fanaroff-Riley classes 1 and 2 (FR 1 and FR 2) radio galaxies. We report several important differences between the FR 1 and FR 2 radio galaxies. At the same host galaxy magnitude or radio luminosity, the FR 2's produce substantially more optical line emission (by roughly an order of magnitude or more) than do FR 1's. Similarly, FR 2 sources produce orders of magnitude more line luminosity than do radio-quiet galaxies of the same optical magnitude, while FR 1 sources and radio-quiet galaxies of the same optical magnitude produce similar line luminosities. Combining these results with previous results from the literature, we conclude that while the emission-line gas in the FR 2's is indeed photoionized by a nuclear UV continuum source from the AGN, the emission-line gas in the FR 1's may be energized predominantly by processes associated with the host galaxy itself. The apparent lack of a strong UV continuum source from the central engine in FR 1 sources can be understood in two different ways. In the first scenario, FR l's are much more efficient at covering jet bulk kinetic energy into radio luminosity than FR 2's, such that an FR 1 has a much lower bolometric AGN luminosity (hence nuclear UV continuum source) than does an FR 2 of the same radio luminosity. We discuss the pros and cons of this model and conclude that the efficiency differences needed between FR 2 and FR 1 radio galaxies are quite large and may lead to difficulties with the interpretation since it would suggest that FR 2 radio source deposit very large amounts of kinetic energy into the ISM Intracluster Medium. However, this interpretation remains viable. Alternatively, it may be that the AGNs in FR 1 sources simply produce far less radiant UV energy than do those in FR 2 sources. That is, FR 1 sources may funnel a higher fraction of the total energy output from the AGNs into jet kinetic energy versus radiant energy than do FR 2 sources. If this interpretation is correct, then this suggests that there is a fundamental difference in the central engine and/or in the immediate "accretion region" around the engine in FR 1 and FR 2 radio galaxies. We note also the absence of FR 1 sources with nuclear broad line regions and suggest that the absence of the BLR is tied to the absence of the "isotropic" nuclear UV continuum source in FR 1 sources. We put forth the possibility that the FR 1/FR 2 dichotomy (i.e., the observed differences in the properties of low- and high-power radio sources) is due to qualitative differences in the structural properties of the central engines in these two types of sources. Following early work by Rees et al. (1982), we suggest the possibility that FR 1 sources are produced when the central engine is fed at a lower accretion rate, leading to the creation of a source in which the ratio of radiant to jet bulk kinetic energy is low, while FR 2 sources are produced when the central engine is fed at a higher accretion rate, causing the central engine to deposit a higher fraction of its energy in radiant energy. We further suggest the possibility that associated differences in the spin properties of the central black hole between FR 1 (lower spin) and FR 2 (higher spin) sources may be responsible for the different collimation properties and Mach numbers of the jets produced by these two types of radio-loud galaxies. This scenario, although currently clearly speculative, is nicely consistent with our current picture of the triggering, feeding, environments, and evolution of powerful radio galaxies. This model allows for evolution of these properties with time for example, the mass accretion rate and BH spin may decline with time causing an FR 2 radio source or quasar to evolve into a FR 1 radio source.

Low birth weight and air pollution in California: Which sources and components drive the risk?

PubMed

Laurent, Olivier; Hu, Jianlin; Li, Lianfa; Kleeman, Michael J; Bartell, Scott M; Cockburn, Myles; Escobedo, Loraine; Wu, Jun

2016-01-01

Intrauterine growth restriction has been associated with exposure to air pollution, but there is a need to clarify which sources and components are most likely responsible. This study investigated the associations between low birth weight (LBW, <2500g) in term born infants (≥37 gestational weeks) and air pollution by source and composition in California, over the period 2001-2008. Complementary exposure models were used: an empirical Bayesian kriging model for the interpolation of ambient pollutant measurements, a source-oriented chemical transport model (using California emission inventories) that estimated fine and ultrafine particulate matter (PM2.5 and PM0.1, respectively) mass concentrations (4km×4km) by source and composition, a line-source roadway dispersion model at fine resolution, and traffic index estimates. Birth weight was obtained from California birth certificate records. A case-cohort design was used. Five controls per term LBW case were randomly selected (without covariate matching or stratification) from among term births. The resulting datasets were analyzed by logistic regression with a random effect by hospital, using generalized additive mixed models adjusted for race/ethnicity, education, maternal age and household income. In total 72,632 singleton term LBW cases were included. Term LBW was positively and significantly associated with interpolated measurements of ozone but not total fine PM or nitrogen dioxide. No significant association was observed between term LBW and primary PM from all sources grouped together. A positive significant association was observed for secondary organic aerosols. Exposure to elemental carbon (EC), nitrates and ammonium were also positively and significantly associated with term LBW, but only for exposure during the third trimester of pregnancy. Significant positive associations were observed between term LBW risk and primary PM emitted by on-road gasoline and diesel or by commercial meat cooking sources. Primary PM from wood burning was inversely associated with term LBW. Significant positive associations were also observed between term LBW and ultrafine particle numbers modeled with the line-source roadway dispersion model, traffic density and proximity to roadways. This large study based on complementary exposure metrics suggests that not only primary pollution sources (traffic and commercial meat cooking) but also EC and secondary pollutants are risk factors for term LBW. Copyright © 2016 Elsevier Ltd. All rights reserved.

FOUR DUAL AGN CANDIDATES OBSERVED WITH THE VLBA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabányi, K. É.; Frey, S.; An, T.

According to hierarchical structure formation models, merging galaxies are expected to be seen in different stages of coalescence. However, there are currently no straightforward observational methods to either select or to confirm a large number of dual active galactic nucleus (AGN) candidates. Most attempts involve obtaining a better understanding of double-peaked narrow emission line sources, in order to distinguish the objects for which the emission lines originate from narrow-line kinematics or jet-driven outflows, from those which might harbor dual AGNs. We observed four such candidate sources with the Very Long Baseline Array (VLBA), at 1.5 GHz with a ∼10 masmore » angular resolution, for which the spectral profiles of AGN optical emission suggested the existence of dual AGNs. In SDSS J210449.13–000919.1 and SDSS J23044.82–093345.3 the radio structures are aligned with the optical emission features, thus the double-peaked emission lines might be the results of jet-driven outflows. In the third detected source SDSS J115523.74+150756.9, the radio structure is less extended and is oriented nearly perpendicular to the position angle derived from optical spectroscopy. The fourth source remained undetected with the VLBA, but it was imaged with the Very Large Array at arcsec resolution a few months before our observations, suggesting the existence of an extended radio structure. We did not detect two radio-emitting cores in any of the four sources, a convincing signature of duality.« less

Models of the Solar Atmospheric Response to Flare Heating

NASA Technical Reports Server (NTRS)

Allred, Joel

2011-01-01

I will present models of the solar atmospheric response to flare heating. The models solve the equations of non-LTE radiation hydrodynamics with an electron beam added as a flare energy source term. Radiative transfer is solved in detail for many important optically thick hydrogen and helium transitions and numerous optically thin EUV lines making the models ideally suited to study the emission that is produced during flares. I will pay special attention to understanding key EUV lines as well the mechanism for white light production. I will also present preliminary results of how the model solar atmosphere responds to Fletcher & Hudson type flare heating. I will compare this with the results from flare simulations using the standard thick target model.

Sensitivity of two dispersion models (AERMOD and ISCST3) to input parameters for a rural ground-level area source.

PubMed

Faulkner, William B; Shaw, Bryan W; Grosch, Tom

2008-10-01

As of December 2006, the American Meteorological Society/U.S. Environmental Protection Agency (EPA) Regulatory Model with Plume Rise Model Enhancements (AERMOD-PRIME; hereafter AERMOD) replaced the Industrial Source Complex Short Term Version 3 (ISCST3) as the EPA-preferred regulatory model. The change from ISCST3 to AERMOD will affect Prevention of Significant Deterioration (PSD) increment consumption as well as permit compliance in states where regulatory agencies limit property line concentrations using modeling analysis. Because of differences in model formulation and the treatment of terrain features, one cannot predict a priori whether ISCST3 or AERMOD will predict higher or lower pollutant concentrations downwind of a source. The objectives of this paper were to determine the sensitivity of AERMOD to various inputs and compare the highest downwind concentrations from a ground-level area source (GLAS) predicted by AERMOD to those predicted by ISCST3. Concentrations predicted using ISCST3 were sensitive to changes in wind speed, temperature, solar radiation (as it affects stability class), and mixing heights below 160 m. Surface roughness also affected downwind concentrations predicted by ISCST3. AERMOD was sensitive to changes in albedo, surface roughness, wind speed, temperature, and cloud cover. Bowen ratio did not affect the results from AERMOD. These results demonstrate AERMOD's sensitivity to small changes in wind speed and surface roughness. When AERMOD is used to determine property line concentrations, small changes in these variables may affect the distance within which concentration limits are exceeded by several hundred meters.

An object oriented implementation of the Yeadon human inertia model

PubMed Central

Dembia, Christopher; Moore, Jason K.; Hubbard, Mont

2015-01-01

We present an open source software implementation of a popular mathematical method developed by M.R. Yeadon for calculating the body and segment inertia parameters of a human body. The software is written in a high level open source language and provides three interfaces for manipulating the data and the model: a Python API, a command-line user interface, and a graphical user interface. Thus the software can fit into various data processing pipelines and requires only simple geometrical measures as input. PMID:25717365

An object oriented implementation of the Yeadon human inertia model.

PubMed

Dembia, Christopher; Moore, Jason K; Hubbard, Mont

2014-01-01

We present an open source software implementation of a popular mathematical method developed by M.R. Yeadon for calculating the body and segment inertia parameters of a human body. The software is written in a high level open source language and provides three interfaces for manipulating the data and the model: a Python API, a command-line user interface, and a graphical user interface. Thus the software can fit into various data processing pipelines and requires only simple geometrical measures as input.

Radiation absorbed dose to bladder walls from positron emitters in the bladder content.

PubMed

Powell, G F; Chen, C T

1987-01-01

A method to calculate absorbed doses at depths in the walls of a static spherical bladder from a positron emitter in the bladder content has been developed. The beta ray dose component is calculated for a spherical model by employing the solutions to the integration of Loevinger and Bochkarev point source functions over line segments and a line segment source array technique. The gamma ray dose is determined using the specific gamma ray constant. As an example, absorbed radiation doses to the bladder walls from F-18 in the bladder content are presented for static spherical bladder models having radii of 2.0 and 3.5 cm, respectively. Experiments with ultra-thin thermoluminescent dosimeters (TLD's) were performed to verify the results of the calculations. Good agreement between TLD measurements and calculations was obtained.

Rosetta3: An Object-Oriented Software Suite for the Simulation and Design of Macromolecules

PubMed Central

Leaver-Fay, Andrew; Tyka, Michael; Lewis, Steven M.; Lange, Oliver F.; Thompson, James; Jacak, Ron; Kaufman, Kristian; Renfrew, P. Douglas; Smith, Colin A.; Sheffler, Will; Davis, Ian W.; Cooper, Seth; Treuille, Adrien; Mandell, Daniel J.; Richter, Florian; Ban, Yih-En Andrew; Fleishman, Sarel J.; Corn, Jacob E.; Kim, David E.; Lyskov, Sergey; Berrondo, Monica; Mentzer, Stuart; Popović, Zoran; Havranek, James J.; Karanicolas, John; Das, Rhiju; Meiler, Jens; Kortemme, Tanja; Gray, Jeffrey J.; Kuhlman, Brian; Baker, David; Bradley, Philip

2013-01-01

We have recently completed a full re-architecturing of the Rosetta molecular modeling program, generalizing and expanding its existing functionality. The new architecture enables the rapid prototyping of novel protocols by providing easy to use interfaces to powerful tools for molecular modeling. The source code of this rearchitecturing has been released as Rosetta3 and is freely available for academic use. At the time of its release, it contained 470,000 lines of code. Counting currently unpublished protocols at the time of this writing, the source includes 1,285,000 lines. Its rapid growth is a testament to its ease of use. This document describes the requirements for our new architecture, justifies the design decisions, sketches out central classes, and highlights a few of the common tasks that the new software can perform. PMID:21187238

Development, Evaluation, and Application of a Primary Aerosol Model.

PubMed

Wang, I T; Chico, T; Huang, Y H; Farber, R J

1999-09-01

The Segmented-Plume Primary Aerosol Model (SPPAM) has been developed over the past several years. The earlier model development goals were simply to generalize the widely used Industrial Source Complex Short-Term (ISCST) model to simulate plume transport and dispersion under light wind conditions and to handle a large number of roadway or line sources. The goals have been expanded to include development of improved algorithm for effective plume transport velocity, more accurate and efficient line and area source dispersion algorithms, and recently, a more realistic and computationally efficient algorithm for plume depletion due to particle dry deposition. A performance evaluation of the SPPAM has been carried out using the 1983 PNL dual tracer experimental data. The results show the model predictions to be in good agreement with observations in both plume advection-dispersion and particulate matter (PM) depletion by dry deposition. For PM 2.5 impact analysis, the SPPAM has been applied to the Rubidoux area of California. Emission sources included in the modeling analysis are: paved road dust, diesel vehicular exhaust, gasoline vehicular exhaust, and tire wear particles from a large number of roadways in Rubidoux and surrounding areas. For the selected modeling periods, the predicted primary PM 2.5 to primary PM10 concentration ratios for the Rubidoux sampling station are in the range of 0.39-0.46. The organic fractions of the primary PM 2.5 impacts are estimated to be at least 34-41%. Detailed modeling results indicate that the relatively high organic fractions are primarily due to the proximity of heavily traveled roadways north of the sampling station. The predictions are influenced by a number of factors; principal among them are the receptor locations relative to major roadways, the volume and composition of traffic on these roadways, and the prevailing meteorological conditions.

Infrasound Studies at the USArray (Invited)

NASA Astrophysics Data System (ADS)

de Groot-Hedlin, C. D.

2013-12-01

Many surface and atmospheric sources, both natural and anthropogenic, have generated infrasound signals that have been recorded on USArray transportable array (TA) seismometers at ranges up to thousands of kilometers. Such sources, including surface explosions, large bolides, mining events, and a space shuttle, have contributed to an understanding of infrasound propagation. We show examples of several atmospheric sources recorded at the TA. We first used USArray data to investigate infrasound signals from the space shuttle 'Atlantis'. Inclement weather in Florida forced the shuttle to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allowed us to test infrasound propagation modeling capabilities through the atmosphere to hundreds of kilometers range from the shuttle's path. Shadow zones and arrival times were predicted by tracing rays launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. Both models predict alternating regions of high and low ensonification to the NW, in line with observations. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds. The models also predict increasing waveform complexity with increasing distance, in line with observations. Several hundreds of broadband seismic stations in the U.S. Pacific Northwest recorded acoustic to seismic coupled signals from a large meteor that entered the atmosphere above northeastern Oregon on 19 February 2008. The travel times of the first arriving energy are consistent with a terminal explosion source model, suggesting that the large size of the explosion masked any signals associated with a continuous line source along its supersonic trajectory. Infrasound was detected at distances over 500 km from the source. A finite-difference time-domain algorithm that allows for propagation through a windy, viscous medium was developed to model signals from this source. We compare synthetics that have been computed using a G2S-ECMWF atmospheric model to signals recorded along an azimuth of 210 degrees from the source. The results show that the timing and the range extent of the direct, stratospherically ducted and thermospherically ducted acoustic branches are accurately predicted. However, estimates of absorption obtained from standard attenuation models predict much greater attenuation for thermospheric returns at frequencies greater than 0.1 Hz than is observed. We conclude that either the standard absorption model for the thermospheric is incorrect, or that thermospheric returns undergo non-linear propagation at very high altitude. In the former case, a better understanding of atmospheric absorption at high altitudes is required; in the latter, non-linear propagation modeling methods are needed to model infrasound propagation at thermospheric altitudes. Finally, we show infrasound signals recorded at TA barometers, generated by a small asteroid that entered Earth's atmosphere at distances between 6000-10000 km from the TA.

An Overview of FlamMap Fire Modeling Capabilities

Treesearch

Mark A. Finney

2006-01-01

Computerized and manual systems for modeling wildland fire behavior have long been available (Rothermel 1983, Andrews 1986). These systems focus on one-dimensional behaviors and assume the fire geometry is a spreading line-fire (in contrast with point or area-source fires). Models included in these systems were developed to calculate fire spread rate (Rothermel 1972,...

3-D interactive visualisation tools for Hi spectral line imaging

NASA Astrophysics Data System (ADS)

van der Hulst, J. M.; Punzo, D.; Roerdink, J. B. T. M.

2017-06-01

Upcoming HI surveys will deliver such large datasets that automated processing using the full 3-D information to find and characterize HI objects is unavoidable. Full 3-D visualization is an essential tool for enabling qualitative and quantitative inspection and analysis of the 3-D data, which is often complex in nature. Here we present SlicerAstro, an open-source extension of 3DSlicer, a multi-platform open source software package for visualization and medical image processing, which we developed for the inspection and analysis of HI spectral line data. We describe its initial capabilities, including 3-D filtering, 3-D selection and comparative modelling.

Spectral analysis of IGR J01572-7259 during its 2016 outburst

NASA Astrophysics Data System (ADS)

La Palombara, N.; Esposito, P.; Mereghetti, S.; Pintore, F.; Sidoli, L.; Tiengo, A.

2018-03-01

We report on the results of the XMM-Newton observation of IGR J01572-7259 during its most recent outburst in 2016 May, the first since 2008. The source reached a flux f ˜ 10-10 erg cm-2 s-1, which allowed us to perform a detailed analysis of its timing and spectral properties. We obtained a pulse period Pspin = 11.58208(2) s. The pulse profile is double peaked and strongly energy dependent, as the second peak is prominent only at low energies and the pulsed fraction increases with energy. The main spectral component is a power-law model, but at low energies, we also detected a soft thermal component, which can be described with either a blackbody or a hot plasma model. Both the EPIC and RGS spectra show several emission lines, which can be identified with the transition lines of ionized N, O, Ne, and Fe and cannot be described with a thermal emission model. The phase-resolved spectral analysis showed that the flux of both the soft excess and the emission lines vary with the pulse phase: the soft excess disappears in the first pulse and becomes significant only in the second, where also the Fe line is stronger. This variability is difficult to explain with emission from a hot plasma, while the reprocessing of the primary X-ray emission at the inner edge of the accretion disc provides a reliable scenario. On the other hand, the narrow emission lines can be due to the presence of photoionized matter around the accreting source.

Derivation of the physical parameters for strong and weak flares from the Hα line

NASA Astrophysics Data System (ADS)

Semeida, M. A.; Rashed, M. G.

2016-06-01

The two flares of 19 and 30 July 1999 were observed in the Hα line using the multichannel flare spectrograph (MFS) at the Astronomical Institute in Ondřejov, Czech Republic. We use a modified cloud method to fit the Hα line profiles which avoids using the background profile. We obtain the four parameters of the two flares: the source function, the optical thickness at line center, the line-of-sight velocity and the Doppler width. The observed asymmetry profiles have been reproduced by the theoretical ones based on our model. A discussion is made about the results of strong and weak flares using the present method.

Experimentally enhanced model-based deconvolution of propagation-based phase-contrast data

NASA Astrophysics Data System (ADS)

Pichotka, M.; Palma, K.; Hasn, S.; Jakubek, J.; Vavrik, D.

2016-12-01

In recent years phase-contrast has become a much investigated modality in radiographic imaging. The radiographic setups employed in phase-contrast imaging are typically rather costly and complex, e.g. high performance Talbot-Laue interferometers operated at synchrotron light sources. In-line phase-contrast imaging states the most pedestrian approach towards phase-contrast enhancement. Utilizing small angle deflection within the imaged sample and the entailed interference of the deflected and un-deflected beam during spatial propagation, in-line phase-contrast imaging only requires a well collimated X-ray source with a high contrast & high resolution detector. Employing high magnification the above conditions are intrinsically fulfilled in cone-beam micro-tomography. As opposed of 2D imaging, where contrast enhancement is generally considered beneficial, in tomographic modalities the in-line phase-contrast effect can be quite a nuisance since it renders the inverse problem posed by tomographic reconstruction inconsistent, thus causing reconstruction artifacts. We present an experimentally enhanced model-based approach to disentangle absorption and in-line phase-contrast. The approach employs comparison of transmission data to a system model computed iteratively on-line. By comparison of the forward model to absorption data acquired in continuous rotation strong local deviations of the data residual are successively identified as likely candidates for in-line phase-contrast. By inducing minimal vibrations (few mrad) to the sample around the peaks of such deviations the transmission signal can be decomposed into a constant absorptive fraction and an oscillating signal caused by phase-contrast which again allows to generate separate maps for absorption and phase-contrast. The contributions of phase-contrast and the corresponding artifacts are subsequently removed from the tomographic dataset. In principle, if a 3D handling of the sample is available, this method also allows to track discontinuities throughout the volume and therefore states a powerful tool in 3D defectoscopy.

Microwave Assisted Helicon Plasmas

NASA Astrophysics Data System (ADS)

McKee, John; Caron, David; Jemiolo, Andrew; Scime, Earl

2017-10-01

The use of two (or more) rf sources at different frequencies is a common technique in the plasma processing industry to control ion energy characteristics separately from plasma generation. A similar approach is presented here with the focus on modifying the electron population in argon and helium plasmas. The plasma is generated by a helicon source at a frequency f0 = 13.56 MHz. Microwaves of frequency f1 = 2.45 GHz are then injected into the helicon source chamber perpendicular to the background magnetic field. The microwaves damp on the electrons via X-mode Electron Cyclotron Heating (ECH) at the upper hybrid resonance, providing additional energy input into the electrons. The effects of this secondary-source heating on electron density, temperature, and energy distribution function are examined and compared to helicon-only single source plasmas as well as numeric models suggesting that the heating is not evenly distributed. Optical Emission Spectroscopy (OES) is used to examine the impact of the energetic tail of the electron distribution on ion and neutral species via collisional excitation. Large enhancements of neutral spectral lines are observed in both Ar and He. While small enhancement of ion lines is seen in Ar, ion lines not normally present in He are observed during microwave injection. U.S. National Science Foundation Grant No. PHY-1360278.

Non-LTE model atmospheres for supersoft X-ray sources

NASA Astrophysics Data System (ADS)

Rauch, T.; Werner, K.

2010-02-01

In the last decade, X-ray observations of hot stellar objects became available with unprecedented resolution and S/N ratio. For an adequate interpretation, fully metal-line blanketed Non-LTE model-atmospheres are necessary. The Tübingen Non-LTE Model Atmosphere Package (TMAP) can calculate such model atmospheres at a high level of sophistication. Although TMAP is not especially designed for the calculation of spectral energy distributions (SEDs) at extreme photospheric parameters, it can be employed for the spectral analysis of burst spectra of novae like V4743 Sgr or line identifications in observations of neutron stars with low magnetic fields in low-mass X-ray binaries (LMXBs) like EXO 0748-676.

Hydrodynamical and Spectral Simulations of HMXB Winds

NASA Astrophysics Data System (ADS)

Mauche, Christopher W.; Liedahl, D. A.; Plewa, T.

2006-09-01

We describe the results of a research program to develop improved models of the X-ray spectra of cosmic sources such as X-ray binaries, CVs, and AGN in which UV line-driven mass flows are photoionized by an X-ray source. Work to date has focused on high-mass X-ray binaries (HMXBs) and on Vela X-1 in particular, for which there are high-quality Chandra HETG spectra in the archive. Our research program combines FLASH hydrodynamic calculations, XSTAR photoionization calculations, HULLAC atomic data, improved calculations of the line force multiplier, X-ray emission models appropriate to X-ray photoionized plasmas, and Monte Carlo radiation transport. We will present movies of the relevant physical quantities (density, temperature, ionization parameter, velocity) from a FLASH two-dimensional time-dependent simulation of Vela X-1, maps showing the emissivity distributions of the X-ray emission lines, and a preliminary comparison of the resulting synthetic spectra to the Chandra HETG spectra. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abercrombie, Robert K; Udoeyop, Akaninyene W; Schlicher, Bob G

This work examines a scientometric model that tracks the emergence of an identified technology from initial discovery (via original scientific and conference literature), through critical discoveries (via original scientific, conference literature and patents), transitioning through Technology Readiness Levels (TRLs) and ultimately on to commercial application. During the period of innovation and technology transfer, the impact of scholarly works, patents and on-line web news sources are identified. As trends develop, currency of citations, collaboration indicators, and on-line news patterns are identified. The combinations of four distinct and separate searchable on-line networked sources (i.e., scholarly publications and citation, patents, news archives, andmore » online mapping networks) are assembled to become one collective network (a dataset for analysis of relations). This established network becomes the basis from which to quickly analyze the temporal flow of activity (searchable events) for the example subject domain we investigated.« less

Modelling of the Saturnian Kilometric Radiation (SKR)

NASA Astrophysics Data System (ADS)

Cecconi, B.; Lamy, L.; Prangé, R.; Zarka, P.; Hess, S.; Clarke, J. T.; Nichols, J.

2008-12-01

The Saturnian Kilometric Radiation (SKR), discovered by the Voyager spacecraft in the 1980's, is observed quasi-continuously by Cassini since 2003. Study of 3 years of SKR observations by RPWS (Radio and Plasma Wave Science) revealed three recurrent features of SKR dynamic spectra : (i) discrete arcs, presumably caused by the anisotropy of the radio emission pattern combined to the observer's motion, (ii) an equatorial shadow zone around the planet (observed near perikrones) and (iii) signal extinctions at high northern latitudes. We model these features using the code PRES (Planetary Radio Emission Simulator) that assumes radio emissions to be generated via the Cyclotron Maser Instability for simulating observed dynamic spectra. We show that observed arc-like structures imply radio sources in partial (~90%) corotation, located on magnetic field lines of invariant latitude 70° to 75°, and emitting at oblique angle from the local magnetic field with a cone angle that varies with frequency. Then, based on the previously demonstrated conjugacy between UV and SKR sources, we successfully model the equatorial shadow zone as well as northern latitude SKR extinctions assuming time variable radio sources distributed along field lines with footprints along the daily UV oval measured from HST images.

Coronal Physics and the Chandra Emission Line Project

NASA Technical Reports Server (NTRS)

Brickhouse, Nancy

1999-01-01

With the launch of the Chandra X-ray Observatory, high resolution X-ray spectroscopy of cosmic sources has begun. Early, deep observations of three stellar coronal sources will provide not only invaluable calibration data, but will also give us benchmarks for plasma spectral modeling codes. These codes are to interpret data from stellar coronae, galaxies and clusters of galaxies. supernova remnants and other astrophysical sources, but they have been called into question in recent years as problems with understanding moderate resolution ASCA and EUVE data have arisen. The Emission Line Project is a collaborative effort to improve the models, with Phase 1 being the comparison of models with observed spectra of Capella, Procyon, and HR, 1099. Goals of these comparisons are (1) to determine and verify accurate and robust diagnostics and (2) to identify and prioritize issues in fundamental spectroscopy which will require further theoretical and/or laboratory work. A critical issue in exploiting the coronal data for these purposes is to understand the extent to which common simplifying assumptions (coronal equilibrium, time-independence, negligible optical depth) apply. We will discuss recent advances in our understanding of stellar coronae in this context.

Seismic and Infrasound Location

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arrowsmith, Stephen J.; Begnaud, Michael L.

2014-03-19

This presentation includes slides on Signal Propagation Through the Earth/Atmosphere Varies at Different Scales; 3D Seismic Models: RSTT; Ray Coverage (Pn); Source-Specific Station Corrections (SSSCs); RSTT Conclusions; SALSA3D (SAndia LoS Alamos) Global 3D Earth Model for Travel Time; Comparison of IDC SSSCs to RSTT Predictions; SALSA3D; Validation and Model Comparison; DSS Lines in the Siberian Platform; DSS Line CRA-4 Comparison; Travel Time Δak135; Travel Time Prediction Uncertainty; SALSA3D Conclusions; Infrasound Data Processing: An example event; Infrasound Data Processing: An example event; Infrasound Location; How does BISL work?; BISL: Application to the 2013 DPRK Test; and BISL: Ongoing Research.

Flexible Environmental Modeling with Python and Open - GIS

NASA Astrophysics Data System (ADS)

Pryet, Alexandre; Atteia, Olivier; Delottier, Hugo; Cousquer, Yohann

2015-04-01

Numerical modeling now represents a prominent task of environmental studies. During the last decades, numerous commercial programs have been made available to environmental modelers. These software applications offer user-friendly graphical user interfaces that allow an efficient management of many case studies. However, they suffer from a lack of flexibility and closed-source policies impede source code reviewing and enhancement for original studies. Advanced modeling studies require flexible tools capable of managing thousands of model runs for parameter optimization, uncertainty and sensitivity analysis. In addition, there is a growing need for the coupling of various numerical models associating, for instance, groundwater flow modeling to multi-species geochemical reactions. Researchers have produced hundreds of open-source powerful command line programs. However, there is a need for a flexible graphical user interface allowing an efficient processing of geospatial data that comes along any environmental study. Here, we present the advantages of using the free and open-source Qgis platform and the Python scripting language for conducting environmental modeling studies. The interactive graphical user interface is first used for the visualization and pre-processing of input geospatial datasets. Python scripting language is then employed for further input data processing, call to one or several models, and post-processing of model outputs. Model results are eventually sent back to the GIS program, processed and visualized. This approach combines the advantages of interactive graphical interfaces and the flexibility of Python scripting language for data processing and model calls. The numerous python modules available facilitate geospatial data processing and numerical analysis of model outputs. Once input data has been prepared with the graphical user interface, models may be run thousands of times from the command line with sequential or parallel calls. We illustrate this approach with several case studies in groundwater hydrology and geochemistry and provide links to several python libraries that facilitate pre- and post-processing operations.

X-ray line coincidence photopumping in a solar flare

DOE PAGES

Keenan, F. P.; Poppenhaeger, K.; Mathioudakis, M.; ...

2017-11-23

Line coincidence photopumping is a process where the electrons of an atomic or molecular species are radiatively excited through the absorption of line emission from another species at a coincident wavelength. There are many instances of line coincidence photopumping in astrophysical sources at optical and ultraviolet wavelengths, with the most famous example being Bowen fluorescence (pumping of O III 303.80 Å by He II), but none to our knowledge in X-rays. However, here we report on a scheme where a He-like line of Ne IX at 11.000 Å is photopumped by He-like Na X at 11.003 Å, which predicts significantmore » intensity enhancement in the Ne IX 82.76 Å transition under physical conditions found in solar flare plasmas. A comparison of our theoretical models with published X-ray observations of a solar flare obtained during a rocket flight provides evidence for line enhancement, with the measured degree of enhancement being consistent with that expected from theory, a truly surprising result. Observations of this enhancement during flares on stars other than the Sun would provide a powerful new diagnostic tool for determining the sizes of flare loops in these distant, spatially unresolved, astronomical sources.« less

X-ray line coincidence photopumping in a solar flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keenan, F. P.; Poppenhaeger, K.; Mathioudakis, M.

Line coincidence photopumping is a process where the electrons of an atomic or molecular species are radiatively excited through the absorption of line emission from another species at a coincident wavelength. There are many instances of line coincidence photopumping in astrophysical sources at optical and ultraviolet wavelengths, with the most famous example being Bowen fluorescence (pumping of O III 303.80 Å by He II), but none to our knowledge in X-rays. However, here we report on a scheme where a He-like line of Ne IX at 11.000 Å is photopumped by He-like Na X at 11.003 Å, which predicts significantmore » intensity enhancement in the Ne IX 82.76 Å transition under physical conditions found in solar flare plasmas. A comparison of our theoretical models with published X-ray observations of a solar flare obtained during a rocket flight provides evidence for line enhancement, with the measured degree of enhancement being consistent with that expected from theory, a truly surprising result. Observations of this enhancement during flares on stars other than the Sun would provide a powerful new diagnostic tool for determining the sizes of flare loops in these distant, spatially unresolved, astronomical sources.« less

X-ray line coincidence photopumping in a solar flare

NASA Astrophysics Data System (ADS)

Keenan, F. P.; Poppenhaeger, K.; Mathioudakis, M.; Rose, S. J.; Flowerdew, J.; Hynes, D.; Christian, D. J.; Nilsen, J.; Johnson, W. R.

2018-03-01

Line coincidence photopumping is a process where the electrons of an atomic or molecular species are radiatively excited through the absorption of line emission from another species at a coincident wavelength. There are many instances of line coincidence photopumping in astrophysical sources at optical and ultraviolet wavelengths, with the most famous example being Bowen fluorescence (pumping of O III 303.80 Å by He II), but none to our knowledge in X-rays. However, here we report on a scheme where a He-like line of Ne IX at 11.000 Å is photopumped by He-like Na X at 11.003 Å, which predicts significant intensity enhancement in the Ne IX 82.76 Å transition under physical conditions found in solar flare plasmas. A comparison of our theoretical models with published X-ray observations of a solar flare obtained during a rocket flight provides evidence for line enhancement, with the measured degree of enhancement being consistent with that expected from theory, a truly surprising result. Observations of this enhancement during flares on stars other than the Sun would provide a powerful new diagnostic tool for determining the sizes of flare loops in these distant, spatially unresolved, astronomical sources.

Movement of the projected pedicles relative to the projected vertebral body in a fourth lumbar vertebra during axial rotation.

PubMed

Coleman, Roger R; Thomas, I Walker

2004-01-01

One use of the anteroposterior lumbar radiograph is to determine axial (y-axis) rotation of the lumbar vertebrae. Rotation might be an element of interest to clinicians seeking to evaluate vertebral positioning. Correlate and quantify movements of the projected pedicles relative to the projected vertebral body during axial rotation and determine if vertebral asymmetry and changes in object film distance affect these movements. A three-dimensional computer model of the fourth and fifth lumbar vertebrae, a modeled radiograph source, and a modeled film were produced. The vertebral model was placed in various degrees of axial rotation at a number of different object film distances. Lines from the source were passed through the pedicles of the fourth lumbar vertebral model and additional lines erected tangent to the lateral body margins. These lines were extended to points of contact with the modeled film. The projected pedicles move relative to the projected vertebral body during y-axis rotation. Vertebral asymmetry and object film distances can also affect the distance of the projected pedicle relative to the projected lateral body margin. Axial rotation produces movement of the projected pedicles relative to the projected vertebral body. However, vertebral asymmetry and changes in object film distance also affect the position of the projected pedicles relative to the projected lateral body margin and might serve as confounders to the clinician seeking to analyze vertebral rotation through the use of the projected pedicles.

Ultraviolet line diagnostics of accretion disk winds in cataclysmic variables

NASA Technical Reports Server (NTRS)

Vitello, Peter; Shlosman, Isaac

1993-01-01

The IUE data base is used to analyze the UV line shapes of the cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating biconical winds from accretion disks. The wind model calculates the wind ionization structure self-consistently including photoionization from the disk and boundary layer and treats 3D line radiation transfer in the Sobolev approximation. It is found that winds from accretion disks provide a good fit for reasonable parameters to the observed UV lines which include the P Cygni profiles for low-inclination systems and pure emission at large inclination. Disk winds are preferable to spherical winds which originate on the white dwarf because they: (1) require a much lower ratio of mass-loss rate to accretion rate and are therefore more plausible energetically; (2) provide a natural source for a biconical distribution of mass outflow which produces strong scattering far above the disk leading to P Cygni profiles for low-inclination systems and pure line emission profiles at high inclination with the absence of eclipses in UV lines; and (3) produce rotation-broadened pure emission lines at high inclination.

UV line diagnostics of accretion disk winds in cataclysmic variables

NASA Technical Reports Server (NTRS)

Vitello, Peter; Shlosman, Isaac

1992-01-01

The IUE data base is used to analyze the UV line shapes of cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating bi-conical winds from accretion disks. The wind model calculates the wind ionization structure self-consistently including photoionization from the disk and boundary layer and treats 3-D line radiation transfer in the Sobolev approximation. It is found that winds from accretion disks provide a good fit for reasonable parameters to the observed UV lines which include the P Cygni profiles for low inclination systems and pure emission at large inclination. Disk winds are preferable to spherical winds which originate on the white dwarf because they (1) require a much lower ratio of mass loss rate to accretion rate and are therefore more plausible energetically, (2) provide a natural source for a bi-conical distribution of mass outflow which produces strong scattering far above the disk leading to P Cygni profiles for low inclination systems, and pure line emission profiles at high inclination with the absence of eclipses in UV lines, and (3) produce rotation broadened pure emission lines at high inclination.

Removal of power line interference of space bearing vibration signal based on the morphological filter and blind source separation

NASA Astrophysics Data System (ADS)

Dong, Shaojiang; Sun, Dihua; Xu, Xiangyang; Tang, Baoping

2017-06-01

Aiming at the problem that it is difficult to extract the feature information from the space bearing vibration signal because of different noise, for example the running trend information, high-frequency noise and especially the existence of lot of power line interference (50Hz) and its octave ingredients of the running space simulated equipment in the ground. This article proposed a combination method to eliminate them. Firstly, the EMD is used to remove the running trend item information of the signal, the running trend that affect the signal processing accuracy is eliminated. Then the morphological filter is used to eliminate high-frequency noise. Finally, the components and characteristics of the power line interference are researched, based on the characteristics of the interference, the revised blind source separation model is used to remove the power line interferences. Through analysis of simulation and practical application, results suggest that the proposed method can effectively eliminate those noise.

The ALMA-PILS survey: 3D modeling of the envelope, disks and dust filament of IRAS 16293-2422

NASA Astrophysics Data System (ADS)

Jacobsen, S. K.; Jørgensen, J. K.; van der Wiel, M. H. D.; Calcutt, H.; Bourke, T. L.; Brinch, C.; Coutens, A.; Drozdovskaya, M. N.; Kristensen, L. E.; Müller, H. S. P.; Wampfler, S. F.

2018-04-01

Context. The Class 0 protostellar binary IRAS 16293-2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows the study of its physical and chemical structure on solar system scales using high angular resolution observations. Such data reveal a complex morphology that cannot be accounted for in traditional, spherical 1D models of the envelope. Aims: The purpose of this paper is to study the environment of the two components of the binary through 3D radiative transfer modeling and to compare with data from the Atacama Large Millimeter/submillimeter Array. Such comparisons can be used to constrain the protoplanetary disk structures, the luminosities of the two components of the binary and the chemistry of simple species. Methods: We present 13CO, C17O and C18O J = 3-2 observations from the ALMA Protostellar Interferometric Line Survey (PILS), together with a qualitative study of the dust and gas density distribution of IRAS 16293-2422. A 3D dust and gas model including disks and a dust filament between the two protostars is constructed which qualitatively reproduces the dust continuum and gas line emission. Results: Radiative transfer modeling in our sampled parameter space suggests that, while the disk around source A could not be constrained, the disk around source B has to be vertically extended. This puffed-up structure can be obtained with both a protoplanetary disk model with an unexpectedly high scale-height and with the density solution from an infalling, rotating collapse. Combined constraints on our 3D model, from observed dust continuum and CO isotopologue emission between the sources, corroborate that source A should be at least six times more luminous than source B. We also demonstrate that the volume of high-temperature regions where complex organic molecules arise is sensitive to whether or not the total luminosity is in a single radiation source or distributed into two sources, affecting the interpretation of earlier chemical modeling efforts of the IRAS 16293-2422 hot corino which used a single-source approximation. Conclusions: Radiative transfer modeling of source A and B, with the density solution of an infalling, rotating collapse or a protoplanetary disk model, can match the constraints for the disk-like emission around source A and B from the observed dust continuum and CO isotopologue gas emission. If a protoplanetary disk model is used around source B, it has to have an unusually high scale-height in order to reach the dust continuum peak emission value, while fulfilling the other observational constraints. Our 3D model requires source A to be much more luminous than source B; LA 18 L⊙ and LB 3 L⊙.

Modeling of radiative properties of Sn plasmas for extreme-ultraviolet source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sasaki, Akira; Sunahara, Atsushi; Furukawa, Hiroyuki

Atomic processes in Sn plasmas are investigated for application to extreme-ultraviolet (EUV) light sources used in microlithography. We develop a full collisional radiative (CR) model of Sn plasmas based on calculated atomic data using Hebrew University Lawrence Livermore Atomic Code (HULLAC). Resonance and satellite lines from singly and multiply excited states of Sn ions, which contribute significantly to the EUV emission, are identified and included in the model through a systematic investigation of their effect on the emission spectra. The wavelengths of the 4d-4f+4p-4d transitions of Sn{sup 5+} to Sn{sup 13+} are investigated, because of their importance for determining themore » conversion efficiency of the EUV source, in conjunction with the effect of configuration interaction in the calculation of atomic structure. Calculated emission spectra are compared with those of charge exchange spectroscopy and of laser produced plasma EUV sources. The comparison is also carried out for the opacity of a radiatively heated Sn sample. A reasonable agreement is obtained between calculated and experimental EUV emission spectra observed under the typical condition of EUV sources with the ion density and ionization temperature of the plasma around 10{sup 18} cm{sup -3} and 20 eV, respectively, by applying a wavelength correction to the resonance and satellite lines. Finally, the spectral emissivity and opacity of Sn plasmas are calculated as a function of electron temperature and ion density. The results are useful for radiation hydrodynamics simulations for the optimization of EUV sources.« less

Using the in-line component for fixed-wing EM 1D inversion

NASA Astrophysics Data System (ADS)

Smiarowski, Adam

2015-09-01

Numerous authors have discussed the utility of multicomponent measurements. Generally speaking, for a vertical-oriented dipole source, the measured vertical component couples to horizontal planar bodies while the horizontal in-line component couples best to vertical planar targets. For layered-earth cases, helicopter EM systems have little or no in-line component response and as a result much of the in-line signal is due to receiver coil rotation and appears as noise. In contrast to this, the in-line component of a fixed-wing airborne electromagnetic (AEM) system with large transmitter-receiver offset can be substantial, exceeding the vertical component in conductive areas. This paper compares the in-line and vertical response of a fixed-wing airborne electromagnetic (AEM) system using a half-space model and calculates sensitivity functions. The a posteriori inversion model parameter uncertainty matrix is calculated for a bathymetry model (conductive layer over more resistive half-space) for two inversion cases; use of vertical component alone is compared to joint inversion of vertical and in-line components. The joint inversion is able to better resolve model parameters. An example is then provided using field data from a bathymetry survey to compare the joint inversion to vertical component only inversion. For each inversion set, the difference between the inverted water depth and ship-measured bathymetry is calculated. The result is in general agreement with that expected from the a posteriori inversion model parameter uncertainty calculation.

The Complex Soft X-ray Spectral Structure of MCG-6-30-15 and Mrk 766

NASA Astrophysics Data System (ADS)

Kahn, S. M.; Sako, M.; Behar, E.; Paerels, F.; Kinkhabwala, A.; Branduardi-Raymont, G.; Page, M. J.; Kaastra, J. S.; Brinkman, A. C.; den Herder, J. S.; Liedahl, D. A.

The interpretation of the soft X-ray spectra of the Seyfert 1 galaxies, MCG-6-30-15 and Mrk 766, has remained controversial since high resolution data were first obtained with the grating instruments on Chandra and XMM-Newton, roughly one year ago. In an initial paper, Branduardi-Raymont et al. (2001), we argued that the RGS spectra of these two sources are inconsistent with simple warm absorber models, as has been invoked for Seyfert 1s in the past, but instead suggest the additional presence of relativistically broadened disk line features associated with the Lyα transitions of carbon, nitrogen, and oxygen. This conclusion was subsequently questioned by Lee et al. (2001), who contended that the Chandra HETG spectrum of MCG-6-30-15 is indeed well-described by the conventional warm absorber model, if one allows for the presence of dust in the warm absorbing medium. Here we reexamine the original RGS spectra in light of the Lee et al. (2001) criticisms. We first show that the explicit model presented by Lee et al. (2001) for MCG-6-30-15 is incompatible with the RGS data on this source, even if we allow both the continuum parameters and all of the absorbing column densities to be free parameters. That model over-predicts the ion{O}{VII} absorption line equivalent widths, and yields significant systematic residuals to the fits, especially at longer wavelengths, beyond the band covered by the HETG. We next show that the column densities of the oxygen ions (ion{O}{IV} through ion{O}{VIII}) are very well-constrained by the absorption line structure in the RGS data, and that, contrary to the assertion by Lee et al. (2001), the derived values are much too low to provide any significant contribution (either from line or continuum absorption) to the observed discrete jump in the spectra near 17.5 Å. Further, we show that the RGS spectra are also incompatible with the dust model presented by Lee et al. (2001). Specifically, the derived upper limit on the neutral oxygen column density is nearly a factor of 35 lower than predicted by their model if the dust is in the form of simple iron oxides. If dust is indeed present in the warm absorber, it would have to be essentially in the form of pure iron to be compatible with the soft X-ray spectrum. In contrast, a model that includes the presence of relativistically broadened CNO Lyα lines, provides an excellent description of the data, correctly accounting for all of the discrete warm absorber lines plus the overall continuum shape for both sources. We suggest that these emission lines are produced via recombination in a photoionized layer on the surface of an irradiated accretion disk. The derived equivalent widths are roughly compatible with what we expect for this layer if one takes proper account of the modification to the disk structure due to the irradiation, and of continuum and line opacity in the ionized surface layer.

Huygen-Fresnel Diffraction Model H-Fdm for the Simulation of Ultrasonic Time-Of Diffraction Technique in 2d Geometries

NASA Astrophysics Data System (ADS)

Reddy, K. Sanjeeva; Krishnamurthy, C. V.; Balasubramaniam, Krishnan; Balasubramanian, T.

2010-02-01

This paper discusses the evaluation of diffracted signals from cracks in 2D based on a new Huygen-Fresnel Diffraction Model (H-FDM). The model employs the frequency-domain far-field displacement expressions derived by Miller & Pursey [1] in 2D for a line source located on the free surface of a semi-infinite elastic medium. At each frequency in the bandwidth of a pulsed excitation, the complex diffracted field is obtained by summing over the unblocked virtual sources located in the section containing a vertical crack. The time-domain diffracted signal is obtained using standard FFT procedures. The effect of beam refraction from a wedge-based finite transducer has been modeled by treating the finite transducer as an array of line sources. The model has been used for predicting diffracted signals in time-of-flight from the crack like defect. The model allows the evaluation of back wall signal amplitude and lateral wave amplitude as well. Experiments have been carried out on 10 mm thick aluminum sample with surface breaking crack of lengths 2 mm and 4 mm using shear probe shoe. The simulated A-Scan results for the aluminum sample with 2 mm and 4 mm surface breaking lengths compare very well in relative amplitudes and time of arrivals with experiments. The H-FDM model offers a tool to evaluate diffraction and related phenomena quantitatively with modest computational resources.

The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX

NASA Technical Reports Server (NTRS)

Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

2009-01-01

This is the second of two papers examining Spitzer Infrared Spectrograph (IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here we perform detailed photoionization modeling of they infrared lines. Our analysis suggests that the luminosity and morphology of the [O IV] 25.89 micron emission line is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter-bounded both in the line of sight direction and to the east, and probably radiation-bounded to the west. A bolometric luminosity in excess of 1040 erg per second would be needed to produce the measured [O IV] flux. We use modeling and previously published studies to conclude that shacks likely contribute very little, if at all, to the high excitation line fluxes observed in the Holmberg II ULX. Additionally, we find that the spectral type of the companion star has a surprisingly strong effect on they predicted strength of the [O IV] emission. This finding could explain the origin of [O IV] hi some starburst systems containing black hole binaries.

The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. 2; Evidence for High Luminosity in Holmberg II ULX

NASA Technical Reports Server (NTRS)

Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

2009-01-01

This is the second of two papers examining Spitzer Infrared Spectrograph (IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here we perform detailed photoionization modeling of the infrared lines. Our analysis suggests that the luminosity and morphology of the [O IV] 25.89 micron emission line is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter-bounded both in the line of sight direction and to the east, and probably radiation-bounded to the west. A bolometric luminosity in excess of 10(exp 40) erg/s would be needed to produce the measured [O IV] flux. We use modeling and previously published studies to conclude that shocks likely contribute very little, if at all, to the high-excitation line fluxes observed in the Holmberg II ULX. Additionally, we find that the spectral type of the companion star has a surprisingly strong effect on the predicted strength of the [O IV] emission. This finding could explain the origin of [O IV] in some starburst systems containing black hole binaries.

Hybrid Skyshine Calculations for Complex Neutron and Gamma-Ray Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shultis, J. Kenneth

2000-10-15

A two-step hybrid method is described for computationally efficient estimation of neutron and gamma-ray skyshine doses far from a shielded source. First, the energy and angular dependence of radiation escaping into the atmosphere from a source containment is determined by a detailed transport model such as MCNP. Then, an effective point source with this energy and angular dependence is used in the integral line-beam method to transport the radiation through the atmosphere up to 2500 m from the source. An example spent-fuel storage cask is analyzed with this hybrid method and compared to detailed MCNP skyshine calculations.

Comparison of optical properties of chromophoric dissolved organic matter (CDOM) in alpine lakes above or below the tree line: insights into sources of CDOM.

PubMed

Su, Yaling; Chen, Feizhou; Liu, Zhengwen

2015-05-01

Here we investigated absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) in 15 alpine lakes located below or above the tree line to determine its source and composition. The results indicate that the concentrations of CDOM in below-tree-line lakes are significantly higher than in above-tree-line lakes, as evidenced from the absorption coefficients of a250 and a365. The intensities of the protein-like and humic-like fluorescence in below-tree-line lakes are higher than in above-tree-line lakes as well. Three fluorescent components were identified using parallel factor analysis (PARAFAC) modelling. Component 1 is probably associated with biological degradation of terrestrial humic component. The terrestrial humic-like component 2 is only found in below-tree-line lakes. The protein-like or phenolic component 3 is dominant in above-tree-line lakes, which is probably more derived from autochthonous origin. In this study, (1) higher a250/a365 and S275-295 values indicate smaller molecular weights of CDOM in above-tree-line lakes than in below-tree-line lakes, and smaller molecular weights at the surface than at 2.0 m depth; (2) SUVA254 and FI255 results provide evidence of lower percent aromaticity of CDOM in above-tree-line lakes; and (3) FI310 and FI370 suggest a strong allochthonous origin at the surface in below-tree-line lakes, and more contribution from autochthonous biological and aquatic bacterial origin in above-tree-line lakes.

MOVES-Matrix and distributed computing for microscale line source dispersion analysis.

PubMed

Liu, Haobing; Xu, Xiaodan; Rodgers, Michael O; Xu, Yanzhi Ann; Guensler, Randall L

2017-07-01

MOVES and AERMOD are the U.S. Environmental Protection Agency's recommended models for use in project-level transportation conformity and hot-spot analysis. However, the structure and algorithms involved in running MOVES make analyses cumbersome and time-consuming. Likewise, the modeling setup process, including extensive data requirements and required input formats, in AERMOD lead to a high potential for analysis error in dispersion modeling. This study presents a distributed computing method for line source dispersion modeling that integrates MOVES-Matrix, a high-performance emission modeling tool, with the microscale dispersion models CALINE4 and AERMOD. MOVES-Matrix was prepared by iteratively running MOVES across all possible iterations of vehicle source-type, fuel, operating conditions, and environmental parameters to create a huge multi-dimensional emission rate lookup matrix. AERMOD and CALINE4 are connected with MOVES-Matrix in a distributed computing cluster using a series of Python scripts. This streamlined system built on MOVES-Matrix generates exactly the same emission rates and concentration results as using MOVES with AERMOD and CALINE4, but the approach is more than 200 times faster than using the MOVES graphical user interface. Because AERMOD requires detailed meteorological input, which is difficult to obtain, this study also recommends using CALINE4 as a screening tool for identifying the potential area that may exceed air quality standards before using AERMOD (and identifying areas that are exceedingly unlikely to exceed air quality standards). CALINE4 worst case method yields consistently higher concentration results than AERMOD for all comparisons in this paper, as expected given the nature of the meteorological data employed. The paper demonstrates a distributed computing method for line source dispersion modeling that integrates MOVES-Matrix with the CALINE4 and AERMOD. This streamlined system generates exactly the same emission rates and concentration results as traditional way to use MOVES with AERMOD and CALINE4, which are regulatory models approved by the U.S. EPA for conformity analysis, but the approach is more than 200 times faster than implementing the MOVES model. We highlighted the potentially significant benefit of using CALINE4 as screening tool for identifying potential area that may exceeds air quality standards before using AERMOD, which requires much more meteorology input than CALINE4.

Modelling of Cosmic Molecular Masers: Introduction to a Computation Cookbook

NASA Astrophysics Data System (ADS)

Sobolev, Andrej M.; Gray, Malcolm D.

2012-07-01

Numerical modeling of molecular masers is necessary in order to understand their nature and diagnostic capabilities. Model construction requires elaboration of a basic description which allows computation, that is a definition of the parameter space and basic physical relations. Usually, this requires additional thorough studies that can consist of the following stages/parts: relevant molecular spectroscopy and collisional rate coefficients; conditions in and around the masing region (that part of space where population inversion is realized); geometry and size of the masing region (including the question of whether maser spots are discrete clumps or line-of-sight correlations in a much bigger region) and propagation of maser radiation. Output of the maser computer modeling can have the following forms: exploration of parameter space (where do inversions appear in particular maser transitions and their combinations, which parameter values describe a `typical' source, and so on); modeling of individual sources (line flux ratios, spectra, images and their variability); analysis of the pumping mechanism; predictions (new maser transitions, correlations in variability of different maser transitions, and the like). Described schemes (constituents and hierarchy) of the model input and output are based mainly on the experience of the authors and make no claim to be dogmatic.

Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

NASA Astrophysics Data System (ADS)

Koulouri, Alexandra; Brookes, Mike; Rimpiläinen, Ville

2017-01-01

In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field.

Trail Creek II: Modeling Flow and E. Coli Concentrations in a Small Urban Stream using SWAT

NASA Astrophysics Data System (ADS)

Radcliffe, D. E.; Saintil, T.

2017-12-01

Pathogens are one of the leading causes of stream and river impairment in the State of Georgia. The common presence of fecal bacteria is driven by several factors including rapid population growth stressing pre-existing and ageing infrastructure, urbanization and poor planning, increase percent imperviousness, urban runoff, municipal discharges, sewage, pet/wildlife waste and leaky septic tanks. The Trail Creek watershed, located in Athens-Clarke County, Georgia covers about 33 km2. Stream segments within Trail Creek violate the GA standard due to high levels of fecal coliform bacteria. In this study, the Soil and Water Assessment Tool (SWAT) modeling software was used to predict E. coli bacteria concentrations during baseflow and stormflow. Census data from the county was used for human and animal population estimates and the Fecal Indicator Tool to generate the number of colony forming units of E. Coli for each source. The model was calibrated at a daily time step with one year of monitored streamflow and E. coli bacteria data using SWAT-CUP and the SUFI2 algorithm. To simulate leaking sewer lines, we added point sources in the five subbasins in the SWAT model with the greatest length of sewer line within 50 m of the stream. The flow in the point sources were set to 5% of the stream flow and the bacteria count set to that of raw sewage (30,000 cfu/100 mL). The calibrated model showed that the average load during 2003-2013 at the watershed outlet was 13 million cfu per month. Using the calibrated model, we simulated scenarios that assumed leaking sewers were repaired in one of the five subbasins with point sources. The reduction ranged from 10 to 46%, with the largest reduction in subbasin in the downtown area. Future modeling work will focus on the use of green infrastructure to address sources of bacteria.

A Quantum Band Model of the nu3 Fundamental of Methanol (CH3OH) and Its Application to Fluorcescence Spectra of Comets

NASA Technical Reports Server (NTRS)

Villanueva, Geronimo L.; DiSanti, M. A.; Mumma, M. J.; Xu, L.-H.

2012-01-01

Methanol (CH3OH) radiates efficiently at infrared wavelengths, dominating the C-H stretching region in comets, yet inadequate quantum-mechanical models have imposed limits on the practical use of its emission spectra. Accordingly, we constructed a new line-by-line model for the 3 fundamental band of methanol at 2844 / cm (3.52 micron) and applied it to interpret cometary fluorescence spectra. The new model permits accurate synthesis of line-by-line spectra for a wide range of rotational temperatures, ranging from 10 K to more than 400 K.We validated the model by comparing simulations of CH3OH fluorescent emission with measured spectra of three comets (C/2001 A2 LINEAR, C/2004 Q2 Machholz and 8P/Tuttle) acquired with high-resolution infrared spectrometers at high-altitude sites. The new model accurately describes the complex emission spectrum of the nu3 band, providing distinct rotational temperatures and production rates at greatly improved confidence levels compared with results derived from earlier fluorescence models. The new model reconciles production rates measured at infrared and radio wavelengths in C/2001 A2 (LINEAR). Methanol can now be quantified with unprecedented precision and accuracy in astrophysical sources through high-dispersion spectroscopy at infrared wavelengths

The theory and mathematical development of AIRPOL-4.

DOT National Transportation Integrated Search

1975-01-01

This is the first in a series of reports documenting the Virginia Department of Highways & Transportation line source model for predicting carbon monoxide concentrations within the microscale environments of highways. The purpose of this first report...

The great galactic centre mystery

NASA Technical Reports Server (NTRS)

Riegler, G. R.

1982-01-01

Gamma-ray observations of the center of the Galaxy show a varying positron-electron annihilation radiation emission, while at radio wavelengths a non-thermal compact source surrounded by ionized gas moving at high velocities can be seen. Line emission maps for atomic and ionized hydrogen and molecular gas suggest gas expulsion and a massive collapsed object. IR observations show that ionized gas in the central few parsecs of the Galactic center is concentrated in at least 14 small clouds. Charge-coupled device images show a pair of faint, very red sources within a few arc seconds of IRS 16 and the compact non-thermal radio source. The positron-electron annihilation line emission implies an annihilation rate of 10 to the 43rd per sec, compared with an observed luminosity at IR wavelengths of 10 to the 40 erg per sec. Some models are briefly discussed.

Consistent modelling of wind turbine noise propagation from source to receiver.

PubMed

Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong; Dag, Kaya O; Moriarty, Patrick

2017-11-01

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. The local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.

Consistent modelling of wind turbine noise propagation from source to receiver

DOE PAGES

Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong; ...

2017-11-28

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. Themore » local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.« less

Consistent modelling of wind turbine noise propagation from source to receiver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. Themore » local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.« less

The Strontium Filament within the Homunculus of Eta Carinae

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Hartman, H.; Zethson, T.; Johansson, S.; Ishibashi, K.; Davidson, K.; Fisher, Richard R. (Technical Monitor)

2001-01-01

During a series of HST/STIS observations of Eta Carinae and associated ejecta, we noticed a peculiar emission filament located a few arcseconds north of the central source. While bright in nebular standards, it is submerged in a sea of scattered starlight until moderately high dispersion, long-slit spectroscopy with the STIS (R- 8000) brings the emission lines out. The initial spectrum, centered on 6768A with the STIS G750M grating, led to identification of twenty lines from singly-Ionized species including [Sr II], [Fe II], [Ti II], [Ni II], [Mn II], and [Co II] (Zethson, etal., 2001, AJ 122,322). No Balmer emission is detected from this filament and the Fe II 2507,9 lines, known to be pumped by Lyman alpha radiation in other regions near the central source, are not detected. Followup observations have led to detection of hundreds more emission lines from iron group elements in neutral and singly-ionized states. Thus far all are excited by less than 10 eV. This peculiar nebular emission is thought to be due to very intense stellar radiation, stripped of uv flux shortward of Lyman alpha, bathing a neutral structure. We are systematically identifying the many lines (over 90% identified) and measuring line intensities that will then be modeled to determine excitation mechanisms, temperature and density. Two [Sr II] and two Sr II lines have now been measured. Bautista, etal. (in preparation) have modeled the strontium flux ratios and find that large radiation fluxes and/or high strontium abundances may account for the detected emission. These observations were supported by STIS GTO funding and GO funding through the STScI

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] Line and Dust Emission in 6

NASA Astrophysics Data System (ADS)

Aravena, M.; Decarli, R.; Walter, F.; Bouwens, R.; Oesch, P. A.; Carilli, C. L.; Bauer, F. E.; Da Cunha, E.; Daddi, E.; Gónzalez-López, J.; Ivison, R. J.; Riechers, D. A.; Smail, I.; Swinbank, A. M.; Weiss, A.; Anguita, T.; Bacon, R.; Bell, E.; Bertoldi, F.; Cortes, P.; Cox, P.; Hodge, J.; Ibar, E.; Inami, H.; Infante, L.; Karim, A.; Magnelli, B.; Ota, K.; Popping, G.; van der Werf, P.; Wagg, J.; Fudamoto, Y.

2016-12-01

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for [C II] line emission and reach a limiting luminosity of L [C II] ˜ (1.6-2.5) × 108 L ⊙. We identify 14 [C II] line emitting candidates in this redshift range with significances >4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S 1.2 mm = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M ⊙ yr-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L [C II] versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.

Point Source X-Ray Lithography System for Sub-0.15 Micron Design Rules

DTIC Science & Technology

1998-05-22

consist of a SAL developed stepper, an SRL developed Dense Plasma Focus , (DPF), X-Ray source, and a CXrL developed beam line. The system will be...existing machine that used spark gap switching, SRL has developed an all solid state driver and improved head electrode assembly for their dense plasma ... focus X-Ray source. Likewise, SAL has used their existing Model 4 stepper installed at CXrL as a design starting point, and has developed an advanced

Line shape parameters of the 22-GHz water line for accurate modeling in atmospheric applications

NASA Astrophysics Data System (ADS)

Koshelev, M. A.; Golubiatnikov, G. Yu.; Vilkov, I. N.; Tretyakov, M. Yu.

2018-01-01

The paper concerns refining parameters of one of the major atmospheric diagnostic lines of water vapor at 22 GHz. Two high resolution microwave spectrometers based on different principles of operation covering together the pressure range from a few milliTorr up to a few Torr were used. Special efforts were made to minimize possible sources of systematic measurement errors. Satisfactory self-consistency of the obtained data was achieved ensuring reliability of the obtained parameters. Collisional broadening and shifting parameters of the line in pure water vapor and in its mixture with air were determined at room temperature. Comparative analysis of the obtained parameters with previous data is given. The speed dependence effect impact on the line shape was evaluated.

Where do field lines go in the quiet magnetosphere?

NASA Technical Reports Server (NTRS)

Stern, David P.; Alekseev, Igor' I.

1988-01-01

The state of knowledge concerning the global pattern of geomagnetic field lines is reviewed. Sources of information on that pattern include (1) magnetic-field models, derived directly from magnetic data or indirectly from generally observed properties and from physics; (2) the tracing of magnetospheric features (e.g., polar cusps or the inner edge of the plasma sheet); (3) matching of magnetic flux; and (4) analysis of magnetic fields. Field-line structure inside about 8 earth radii is known fairly well, but beyond that, especially in the tail, the situation becomes rather uncertain and variable. Two particularly difficult problems are the linkage between open field lines and the interplanetary field and the field-line structure of the quiescent magnetosphere following periods of prolonged northward Bz.

Non-LTE line formation in a magnetic field. II. The influence of noncoherent scattering on line contours

DOE Office of Scientific and Technical Information (OSTI.GOV)

Domke, H.; Staude, J.

1973-08-01

Theoretical line contours calculated for fixed values of the line constants and a given model atmosphere show an increase of the stokes parameters Q, U, and V but a decrease of I if the portion of noncoherent scattering increases. These effects increase from the center of the solar disk to the limb. The action of scattering may be approximately simulated in LTE contours by increasing the gradient of the source function and fitting in this way theoretical contours to observed ones. There remains, however, the effect of V- reversal near the line core, which is caused by anomalous dispersion andmore » is abnormally increased by scattering. (auth)« less

Seyfert galaxy ultraviolet emission-line intensities and variability - A self-consistent photoionization analysis applied to broad-line-emitting gas in NGC 3783

NASA Technical Reports Server (NTRS)

Koratkar, Anuradha P.; Macalpine, Gordon M.

1992-01-01

Well-constrained photoionization models for the Seyfert I galaxy NGC 3783 are developed. Both cross-correlation analyses and line variability trends with varying ionizing radiation flux require a multicomponent picture. All the data for He II 1640 A, C IV 1549 A, and semiforbidden C III 1909 A can be reasonably well reproduced by two cloud components. One has a source-cloud distance of 24 lt-days, gas density around 3 x 10 exp 10/cu cm, ionization parameter range of 0.04-0.2, and cloud thickness such that about half of the carbon is doubly ionized and about half is triply ionized. The other component is located approximately 96 lt-days from the source, is shielded from the source by the inner cloud, has a density about 3 x 10 to the 9th/cu cm, and is characterized by an ionization parameter range of 0.001-0.03, The cloud thickness is such that about 45 percent carbon is doubly ionized and about 55 percent is singly ionized.

Theory and application of laser ultrasonic shear wave birefringence measurements to the determination of microstructure orientation in transversely isotropic, polycrystalline graphite materials

DOE PAGES

Zeng, Fan W.; Contescu, Cristian I.; Gallego, Nidia C.; ...

2016-12-18

Laser ultrasonic line source methods have been used to study elastic anisotropy in nuclear graphites by measuring shear wave birefringence. Depending on the manufacturing processes used during production, nuclear graphites can exhibit various degrees of material anisotropy related to preferred crystallite orientation and to microcracking. In this paper, laser ultrasonic line source measurements of shear wave birefringence on NBG-25 have been performed to assess elastic anisotropy. Laser line sources allow specific polarizations for shear waves to be transmitted – the corresponding wavespeeds can be used to compute bulk, elastic moduli that serve to quantify anisotropy. These modulus values can bemore » interpreted using physical property models based on orientation distribution coefficients and microcrack-modified, single crystal moduli to represent the combined effects of crystallite orientation and microcracking on material anisotropy. Finally, ultrasonic results are compared to and contrasted with measurements of anisotropy based on the coefficient of thermal expansion to show the relationship of results from these techniques.« less

Magnetic Topology of the Global MHD Configuration on 2010 August 1-2

NASA Astrophysics Data System (ADS)

Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J.; Panasenco, O.

2014-12-01

It appears that the global magnetic topology of the solar corona predetermines to a large extent the magnetic flux transfer during solar eruptions. We have recently analyzed the global topology for a source-surface model of the background magnetic field at the time of the 2010 August 1-2 sympathetic CMEs (Titov et al. 2012). Now we extend this analysis to a more accurate thermodynamic MHD model of the solar corona. As for the source-surface model, we find a similar triplet of pseudo-streamers in the source regions of the eruptions. The new study confirms that all these pseudo-streamers contain separatrix curtains that fan out from a basic magnetic null point, individual for each of the pseudo-streamers. In combination with the associated separatrix domes, these separatrix curtains fully isolate adjacent coronal holes of the like polarity from each other. However, the size and shape of the coronal holes, as well as their open magnetic fluxes and the fluxes in the lobes of the separatrix domes, are very different for the two models. The definition of the open separator field lines, where the (interchange) reconnection between open and closed magnetic flux takes place, is also modified, since the structurally unstable source-surface null lines do not exist anymore in the MHD model. In spite of all these differences, we reassert our earlier hypothesis that magnetic reconnection at these nulls and the associated separators likely plays a key role in coupling the successive eruptions observed by SDO and STEREO. The results obtained provide further validation of our recent simplified MHD model of sympathetic eruptions (Török et al. 2011). Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.

THE GAS/DUST RATIO OF CIRCUMSTELLAR DISKS: TESTING MODELS OF PLANETESIMAL FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horne, David; Gibb, Erika; Rettig, Terrence W.

2012-07-20

We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. {sup 12}CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig etmore » al.« less

The reawakening of the sleeping X-ray pulsar XTE J1946+274

NASA Astrophysics Data System (ADS)

Müller, S.; Kühnel, M.; Caballero, I.; Pottschmidt, K.; Fürst, F.; Kreykenbohm, I.; Sagredo, M.; Obst, M.; Wilms, J.; Ferrigno, C.; Rothschild, R. E.; Staubert, R.

2012-10-01

We report on a series of outbursts of the high-mass X-ray binary XTE J1946+274 in 2010/2011 observed with INTEGRAL, RXTE, and Swift. We discuss possible mechanisms resulting in the extraordinary outburst behavior of this source. The X-ray spectra can be described by standard phenomenological models, enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron Kα fluorescence line at 6.4 keV, which are variable in flux and pulse phase. We find possible evidence for a cyclotron resonance scattering feature at about 25 keV at the 93% level. The presence of a strong cyclotron line at 35 keV seen in data from the source's 1998 outburst that was confirmed by a reanalysis of these data can be excluded. This result indicates that the cyclotron line feature in XTE J1946+274 is variable between individual outbursts.

Solution of the wave equation for open surfaces involving a line integral over the edge. [for supersonic propeller noise prediction

NASA Technical Reports Server (NTRS)

Farassat, F.

1984-01-01

A simple mathematical model of a stationary source distribution for the supersonic-propeller noise-prediction formula of Farassat (1983) is developed to test the validity of the formula solutions. The conventional thickness source term is used in place of the Isom thickness formula; the relative importance of the line and surface integrals in the solutions is evaluated; and the numerical results are compared with those obtained with a conventional retarded-time solution in tables. Good agreement is obtained over elevation angles from 10 to 90 deg, and the line-integral contribution is found to be significant at all elevation angles and of the same order of magnitude as the surface-integral contribution at angles less than 30 deg. The amplitude-normalized directivity patterns for the four cases computed (x = 1.5 or 10; k = 5.0 or 50) are presented graphically.

MAST Propellant and Delivery System Design Methods

NASA Technical Reports Server (NTRS)

Nadeem, Uzair; Mc Cleskey, Carey M.

2015-01-01

A Mars Aerospace Taxi (MAST) concept and propellant storage and delivery case study is undergoing investigation by NASA's Element Design and Architectural Impact (EDAI) design and analysis forum. The MAST lander concept envisions landing with its ascent propellant storage tanks empty and supplying these reusable Mars landers with propellant that is generated and transferred while on the Mars surface. The report provides an overview of the data derived from modeling between different methods of propellant line routing (or "lining") and differentiate the resulting design and operations complexity of fluid and gaseous paths based on a given set of fluid sources and destinations. The EDAI team desires a rough-order-magnitude algorithm for estimating the lining characteristics (i.e., the plumbing mass and complexity) associated different numbers of vehicle propellant sources and destinations. This paper explored the feasibility of preparing a mathematically sound algorithm for this purpose, and offers a method for the EDAI team to implement.

The Reawakening of the Sleeping X-ray Pulsar XTE J1946+274

NASA Technical Reports Server (NTRS)

Mueller, Sebastian; Mueller, Sebastian; Kuechnel, Matthias; Fuerst, Felix; Kreykenbohm, Ingo; Sagredo, Macarena; Obst, Maria; Wilms, Joern; Caballero, Isabel; Potttschmidt, Katja;

Testing Envelope Models of Young Stellar Objects with Submillimeter Continuum and Molecular-Line Observations

NASA Astrophysics Data System (ADS)

Hogerheijde, Michiel R.; Sandell, Göran

2000-05-01

Theoretical models of star formation make predictions about the density and velocity structure of the envelopes surrounding isolated, low-mass young stars. This paper tests such models through high-quality submillimeter continuum imaging of four embedded young stellar objects in Taurus and previously obtained molecular-line data. Observations carried out with the Submillimeter Continuum Bolometer Array on the James Clerk Maxwell Telescope at 850 and 450 μm of L1489 IRS, L1535 IRS, L1527 IRS, and TMC 1 reveal ~2000 AU elongated structures embedded in extended envelopes. The density distribution in these envelopes is equally well fitted by a radial power-law of index p=1.0-2.0 or with a collapse model such as that of Shu. This inside-out collapse model predicts 13CO, C18O, HCO+, and H13CO+ line profiles that closely match observed spectra toward three of our four sources. This shows that the inside-out collapse model offers a good description of YSO envelopes, but also that reliable constraints on its parameters require independent measurements of the density and the velocity structure, e.g., through continuum and line observations. For the remaining source, L1489 IRS, we find that a model consisting of a 2000 AU radius, rotating, disklike structure better describes the data. Possibly, this source is in transition between the embedded class I and the optically revealed T Tauri phases. The spectral index of the dust emissivity decreases from β=1.5-2.0 in the extended envelope to 1.0+/-0.2 in the central peaks, indicating grain growth or high optical depth on small scales. The observations of L1527 IRS reveal warm (>~30 K) material outlining, and presumably heated by, its bipolar outflow. This material comprises <~0.2 Msolar, comparable to the amount of swept-up CO but only 10% of the total envelope mass. Two apparently starless cores are found at ~10,000 AU from L1489 IRS and L1535 IRS. They are cold, 10-15 K, contain 0.5-3.0 Msolar, and have flat density distributions characterized by a Gaussian of ~10,000 AU FWHM. The proximity of these cores shows that star formation in truly isolated cores is rare even in Taurus.

Open-source Software for Exoplanet Atmospheric Modeling

NASA Astrophysics Data System (ADS)

Cubillos, Patricio; Blecic, Jasmina; Harrington, Joseph

2018-01-01

I will present a suite of self-standing open-source tools to model and retrieve exoplanet spectra implemented for Python. These include: (1) a Bayesian-statistical package to run Levenberg-Marquardt optimization and Markov-chain Monte Carlo posterior sampling, (2) a package to compress line-transition data from HITRAN or Exomol without loss of information, (3) a package to compute partition functions for HITRAN molecules, (4) a package to compute collision-induced absorption, and (5) a package to produce radiative-transfer spectra of transit and eclipse exoplanet observations and atmospheric retrievals.

An ALMA Survey of CO Isotopologue Emission from Protoplanetary Disks in Chamaeleon I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long Feng; Herczeg, Gregory J.; Pascucci, Ilaria

The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-to-dust ratio. To investigate the utility of CO as an alternate probe of disk mass, we use ALMA to survey {sup 13}CO and C{sup 18}O J = 3–2 line emission from a sample of 93 protoplanetary disks around stars and brown dwarfs with masses from in the nearby Chamaeleon I star-forming region. We detect {sup 13}CO emission from 17 sources and C{sup 18}O from only one source.more » Gas masses for disks are then estimated by comparing the CO line luminosities to results from published disk models that include CO freeze-out and isotope-selective photodissociation. Under the assumption of a typical interstellar medium CO-to-H{sub 2} ratio of 10{sup −4}, the resulting gas masses are implausibly low, with an average gas mass of ∼0.05 M {sub Jup} as inferred from the average flux of stacked {sup 13}CO lines. The low gas masses and gas-to-dust ratios for Cha I disks are both consistent with similar results from disks in the Lupus star-forming region. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models. The conversion of CO flux to CO gas mass also suffers from uncertainties in disk structures, which could affect gas temperatures. CO emission lines will only be a good tracer of the disk mass when models for C and CO depletion are confirmed to be accurate.« less

An ALMA Survey of CO Isotopologue Emission from Protoplanetary Disks in Chamaeleon I

NASA Astrophysics Data System (ADS)

Long, Feng; Herczeg, Gregory J.; Pascucci, Ilaria; Drabek-Maunder, Emily; Mohanty, Subhanjoy; Testi, Leonardo; Apai, Daniel; Hendler, Nathan; Henning, Thomas; Manara, Carlo F.; Mulders, Gijs D.

2017-08-01

The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-to-dust ratio. To investigate the utility of CO as an alternate probe of disk mass, we use ALMA to survey 13CO and C18O J = 3–2 line emission from a sample of 93 protoplanetary disks around stars and brown dwarfs with masses from in the nearby Chamaeleon I star-forming region. We detect 13CO emission from 17 sources and C18O from only one source. Gas masses for disks are then estimated by comparing the CO line luminosities to results from published disk models that include CO freeze-out and isotope-selective photodissociation. Under the assumption of a typical interstellar medium CO-to-H2 ratio of 10‑4, the resulting gas masses are implausibly low, with an average gas mass of ∼0.05 M Jup as inferred from the average flux of stacked 13CO lines. The low gas masses and gas-to-dust ratios for Cha I disks are both consistent with similar results from disks in the Lupus star-forming region. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models. The conversion of CO flux to CO gas mass also suffers from uncertainties in disk structures, which could affect gas temperatures. CO emission lines will only be a good tracer of the disk mass when models for C and CO depletion are confirmed to be accurate.

A KEPLERIAN-LIKE DISK AROUND THE FORMING O-TYPE STAR AFGL 4176

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Katharine G.; Hoare, Melvin G.; Robitaille, Thomas P.

We present Atacama Large Millimeter/submillimeter Array line and continuum observations at 1.2 mm with ∼0.″3 resolution that uncover a Keplerian-like disk around the forming O-type star AFGL 4176. The continuum emission from the disk at 1.21 mm (source mm1) has a deconvolved size of 870 ± 110 AU × 330 ± 300 AU and arises from a structure ∼8 M{sub ⊙} in mass, calculated assuming a dust temperature of 190 K. The first-moment maps, pixel-to-pixel line modeling, assuming local thermodynamic equilibrium (LTE), and position–velocity diagrams of the CH{sub 3}CN J = 13–12 K-line emission all show a velocity gradient alongmore » the major axis of the source, coupled with an increase in velocity at small radii, consistent with Keplerian-like rotation. The LTE line modeling shows that where CH{sub 3}CN J = 13–12 is excited, the temperatures in the disk range from ∼70 to at least 300 K and that the H{sub 2} column density peaks at 2.8 × 10{sup 24} cm{sup −2}. In addition, we present Atacama Pathfinder Experiment {sup 12}CO observations that show a large-scale outflow from AFGL 4176 perpendicular to the major axis of mm1, supporting the disk interpretation. Finally, we present a radiative transfer model of a Keplerian disk surrounding an O7 star, with a disk mass and radius of 12 M{sub ⊙} and 2000 AU that reproduces the line and continuum data, further supporting our conclusion that our observations have uncovered a Keplerian-like disk around an O-type star.« less

Does the Sun Have a Full-Time Chromosphere?

NASA Astrophysics Data System (ADS)

Kalkofen, Wolfgang; Ulmschneider, Peter; Avrett, Eugene H.

1999-08-01

The successful modeling of the dynamics of H2v bright points in the nonmagnetic chromosphere by Carlsson & Stein gave as a by-product a part-time chromosphere lacking the persistent outward temperature increase of time-average empirical models, which is needed to explain observations of UV emission lines and continua. We discuss the failure of the dynamical model to account for most of the observed chromospheric emission, arguing that their model uses only about 1% of the acoustic energy supplied to the medium. Chromospheric heating requires an additional source of energy in the form of acoustic waves of short period (P<2 minutes), which form shocks and produce the persistent outward temperature increase that can account for the UV emission lines and continua.

Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR

NASA Astrophysics Data System (ADS)

Xu, Yanjun; Harrison, Fiona A.; García, Javier A.; Fabian, Andrew C.; Fürst, Felix; Gandhi, Poshak; Grefenstette, Brian W.; Madsen, Kristin K.; Miller, Jon M.; Parker, Michael L.; Tomsick, John A.; Walton, Dominic J.

2018-01-01

We report on a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently discovered bright black hole candidate MAXI J1535-571. NuSTAR observed the source on MJD 58003 (five days after the outburst was reported). The spectrum is characteristic of a black hole binary in the hard state. We observe clear disk reflection features, including a broad Fe Kα line and a Compton hump peaking around 30 keV. Detailed spectral modeling reveals a narrow Fe Kα line complex centered around 6.5 keV on top of the strong relativistically broadened Fe Kα line. The narrow component is consistent with distant reflection from moderately ionized material. The spectral continuum is well described by a combination of cool thermal disk photons and a Comptonized plasma with the electron temperature {{kT}}{{e}}=19.7+/- 0.4 keV. An adequate fit can be achieved for the disk reflection features with a self-consistent relativistic reflection model that assumes a lamp-post geometry for the coronal illuminating source. The spectral fitting measures a black hole spin a> 0.84, inner disk radius {R}{in}< 2.01 {r}{ISCO}, and a lamp-post height h={7.2}-2.0+0.8 {r}{{g}} (statistical errors, 90% confidence), indicating no significant disk truncation and a compact corona. Although the distance and mass of this source are not currently known, this suggests the source was likely in the brighter phases of the hard state during this NuSTAR observation.

New Methods For Interpretation Of Magnetic Gradient Tensor Data Using Eigenalysis And The Normalized Source Strength

NASA Astrophysics Data System (ADS)

Clark, D.

2012-12-01

In the future, acquisition of magnetic gradient tensor data is likely to become routine. New methods developed for analysis of magnetic gradient tensor data can also be applied to high quality conventional TMI surveys that have been processed using Fourier filtering techniques, or otherwise, to calculate magnetic vector and tensor components. This approach is, in fact, the only practical way at present to analyze vector component data, as measurements of vector components are seriously afflicted by motion noise, which is not as serious a problem for gradient components. In many circumstances, an optimal approach to extracting maximum information from magnetic surveys would be to combine analysis of measured gradient tensor data with vector components calculated from TMI measurements. New methods for inverting gradient tensor surveys to obtain source parameters have been developed for a number of elementary, but useful, models. These include point dipole (sphere), vertical line of dipoles (narrow vertical pipe), line of dipoles (horizontal cylinder), thin dipping sheet, horizontal line current and contact models. A key simplification is the use of eigenvalues and associated eigenvectors of the tensor. The normalized source strength (NSS), calculated from the eigenvalues, is a particularly useful rotational invariant that peaks directly over 3D compact sources, 2D compact sources, thin sheets and contacts, and is independent of magnetization direction for these sources (and only very weakly dependent on magnetization direction in general). In combination the NSS and its vector gradient enable estimation of the Euler structural index, thereby constraining source geometry, and determine source locations uniquely. NSS analysis can be extended to other useful models, such as vertical pipes, by calculating eigenvalues of the vertical derivative of the gradient tensor. Once source locations are determined, information of source magnetizations can be obtained by simple linear inversion of measured or calculated vector and/or tensor data. Inversions based on the vector gradient of the NSS over the Tallawang magnetite deposit in central New South Wales obtained good agreement between the inferred geometry of the tabular magnetite skarn body and drill hole intersections. Inverted magnetizations are consistent with magnetic property measurements on drill core samples from this deposit. Similarly, inversions of calculated tensor data over the Mount Leyshold gold-mineralized porphyry system in Queensland yield good estimates of the centroid location, total magnetic moment and magnetization direction of the magnetite-bearing potassic alteration zone that are consistent with geological and petrophysical information.

Carbon recombination lines as a diagnostic of photodissociation regions

NASA Technical Reports Server (NTRS)

Natta, A.; Walmsley, C. M.; Tielens, A. G. G. M.

1994-01-01

We have observed the C91 alpha radio recombination line toward the Orion H II region. This narrow (approximately 3-5 km per sec full width at half maximum (FWHM)) line is spatially very extended (approximately 8 arcmin or 1 pc). These charateristics compare well with the observed characteristics of the C II fine structure line at 158 microns. Thus, the C91 alpha line originates in the predominantly neutral photodissociation regions separating the H II region from the molecular cloud. We have developed theoretical models for the C II radio recombination lines from photodissociation regions. The results show that the I(C91 alpha)/I(C158) intensity ratio is a sensitive function of the temperature and density of the emitting gas. We have also extended theoretical models for photodissociation regions to include the C II recombination lines. Comparison with these models show that, in the central portion of the Orion region, the C91 alpha line originates in dense (10(exp 6) per cu cm), warm (500-1000 K) gas. Even at large projected distances (approximately 1 pc), the inferred density is still high (10(exp 5) per cu cm) and implies extremely high thermal pressures. As in the case of the (C II) 158 microns line, the large extent of the C91 alpha line shows that (FUV) photons can penetrate to large distances from the illuminating source. The decline of the intensity of the incident radiation field with distance from Theta(sup 1) C seems to be dominated by geometrical dilution, rather than dust extinction. Finally, we have used our models to calculate the intensity of the 9850 A recombination line of C II. The physical conditions inferred from this line are in good agreement with those determined from the radio recombination and the far-infrared fine-structure lines. We show that the ratio of the 9850 A to the C91 alpha lines is a very good probe of very high density clumps.

Load-Flow in Multiphase Distribution Networks: Existence, Uniqueness, Non-Singularity, and Linear Models

DOE PAGES

Bernstein, Andrey; Wang, Cong; Dall'Anese, Emiliano; ...

2018-01-01

This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for themore » non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.« less

Laboratory calibration of density-dependent lines in the extreme ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Lepson, J. K.; Beiersdorfer, P.; Gu, M. F.; Desai, P.; Bitter, M.; Roquemore, L.; Reinke, M. L.

2012-05-01

We have been making spectral measurements in the extreme ultraviolet (EUV) from different laboratory sources in order to investigate the electron density dependence of various astrophysically important emission lines and to test the atomic models underlying the diagnostic line ratios. The measurement are being performed at the Livermore EBIT-I electron beam ion trap, the National Spherical Torus Experiment (NSTX) at Princeton, and the Alcator C-Mod tokamak at the Massachusetts Institute of Technology, which together span an electron density of four orders of magnitude and which allow us to test the various models at high and low density limits. Here we present measurements of Fe XXII and Ar XIV, which include new data from an ultra high resolution (λ/Δλ >4000) spectrometer at the EBIT-I facility. We found good agreement between the measurements and modeling calculations for Fe XXII, but poorer agreement for Ar XIV.

Load-Flow in Multiphase Distribution Networks: Existence, Uniqueness, Non-Singularity, and Linear Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernstein, Andrey; Wang, Cong; Dall'Anese, Emiliano

This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for themore » non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.« less

On determining dose rate constants spectroscopically.

PubMed

Rodriguez, M; Rogers, D W O

2013-01-01

To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of (125)I and (103)Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated (125)I and (103)Pd sources. Spectra generated by 14 (125)I and 6 (103)Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm(3) voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the (125)I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for (103)Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ≤0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. The ratio of the intensity of the 31 keV line relative to that of the main peak in (125)I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The (103)Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are in much better agreement with the calculations using the NCRP Report 58 and NNDC(2000) initial spectra with average discrepancies of 0.9% and 1.7% for the (125)I and (103)Pd seeds, respectively. However, there are no differences in the calculated TG-43U1 brachytherapy parameters using either initial spectrum in both cases. Similarly, there were no differences outside the statistical uncertainties of 0.1% or 0.2%, in the average energy, air kerma/history, dose rate/history, and dose rate constant when calculated using either the full photon spectrum or the main-peaks-only spectrum. Our calculated dose rate constants based on using the calculated on-axis spectrum and a line or dual-point source model are in excellent agreement (0.5% on average) with the values of Chen and Nath, verifying the accuracy of their more approximate method of going from the spectrum to the dose rate constant. However, the dose rate constants based on full seed models differ by between +4.6% and -1.5% from those based on the line or dual-point source approximations. These results suggest that the main value of spectroscopic measurements is to verify full Monte Carlo models of the seeds by comparison to the calculated spectra.

Analytical performance study of solar blind non-line-of-sight ultraviolet short-range communication links.

PubMed

Xu, Zhengyuan; Ding, Haipeng; Sadler, Brian M; Chen, Gang

2008-08-15

Motivated by recent advances in solid-state incoherent ultraviolet sources and solar blind detectors, we study communication link performance over a range of less than 1 km with a bit error rate (BER) below 10(-3) in solar blind non-line-of-sight situation. The widely adopted yet complex single scattering channel model is significantly simplified by means of a closed-form expression for tractable analysis. Path loss is given as a function of transceiver geometry as well as atmospheric scattering and attenuation and is compared with experimental data for model validation. The BER performance of a shot-noise-limited receiver under this channel model is demonstrated.

Cloudy 94 and Applications to Quasar Emission Line Regions

NASA Technical Reports Server (NTRS)

Ferland, Gary J.

2000-01-01

This review discusses the most recent developments of the plasma simulation code Cloudy and its application to the, emission-line regions of quasars. The longterm goal is to develop the tools needed to determine the chemical composition of the emitting gas and the luminosity of the central engine for any emission line source. Emission lines and the underlying thermal continuum are formed in plasmas that are far from thermodynamic equilibrium. Their thermal and ionization states are the result of a balance of a vast set of microphysical processes. Once produced, radiation must, propagate out of the (usually) optically thick source. No analytic solutions are possible, and recourse to numerical simulations is necessary. I am developing the large-scale plasma simulation code Cloudy as an investigative tool for this work, much as an observer might build a spectrometer. This review describes the current version of Cloudy, version 94. It describes improvements made since the, release of the previous version, C90. The major recent, application has been the development of the "Locally Optimally-Emitting Cloud" (LOC) model of AGN emission line regions. Powerful selection effects, introduced by the atomic physics and line formation process, permit individual lines to form most efficiently only near certain selected parameters. These selection effects, together with the presence of gas with a wide range of conditions, are enough to reproduce the spectrum of a typical quasar with little dependence on details. The spectrum actually carries little information to the identity of the emitters. I view this as a major step forward since it provides a method to handle accidental details at the source, so that we can concentrate on essential information such as the luminosity or chemical composition of the quasar.

A correlation between hard gamma-ray sources and cosmic voids along the line of sight

DOE PAGES

Furniss, A.; Sutter, P. M.; Primack, J. R.; ...

2014-11-25

We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E > 100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as “VHE-like” sources) are distributed along underdense lines of sight at the 2.4σ level. There is a less suggestive correlation for the Fermi hard source population (1.7σ). A correlation between 10-500 GeV fluxmore » and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4σ and 2.6σ, calculated from the Pearson correlation coefficients of r = 0.57 and 0.47, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity τ(E, z) ~ 5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight.« less

Shocked molecular hydrogen in the bipolar outflow NGC 2071

NASA Technical Reports Server (NTRS)

Burton, Michael G.; Geballe, T. R.; Brand, P. W. J. L.

1989-01-01

Maps of the emission from the v = 1-0 S(1) line of molecular hydrogen in the bipolar outflow of NGC 2071 are presented. The line emission is shown to peak at six positions distributed irregularly along two lobes which are parallel to, but offset about 20 arcsec from, the lobes of the high-velocity CO-line emission. The energetics and composition of the high-velocity gas support a model in which the driving agent is a bipolar atomic wind which arises from the vicinity of the central IR sources and shocks the surrounding molecular cloud, evacuating a cavity within it.

Stan: A Probabilistic Programming Language for Bayesian Inference and Optimization

ERIC Educational Resources Information Center

Gelman, Andrew; Lee, Daniel; Guo, Jiqiang

2015-01-01

Stan is a free and open-source C++ program that performs Bayesian inference or optimization for arbitrary user-specified models and can be called from the command line, R, Python, Matlab, or Julia and has great promise for fitting large and complex statistical models in many areas of application. We discuss Stan from users' and developers'…

Study on induced radioactivity of China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Wu, Qing-Biao; Wang, Qing-Bin; Wu, Jing-Min; Ma, Zhong-Jian

2011-06-01

China Spallation Neutron Source (CSNS) is the first High Energy Intense Proton Accelerator planned to be constructed in China during the State Eleventh Five-Year Plan period, whose induced radioactivity is very important for occupational disease hazard assessment and environmental impact assessment. Adopting the FLUKA code, the authors have constructed a cylinder-tunnel geometric model and a line-source sampling physical model, deduced proper formulas to calculate air activation, and analyzed various issues with regard to the activation of different tunnel parts. The results show that the environmental impact resulting from induced activation is negligible, whereas the residual radiation in the tunnels has a great influence on maintenance personnel, so strict measures should be adopted.

Operational evaluation of the RLINE dispersion model for studies of traffic-related air pollutants

NASA Astrophysics Data System (ADS)

Milando, Chad W.; Batterman, Stuart A.

2018-06-01

Exposure to traffic-related air pollutants (TRAP) remains a key public health issue, and improved exposure measures are needed to support health impact and epidemiologic studies and inform regulatory responses. The recently developed Research LINE source model (RLINE), a Gaussian line source dispersion model, has been used in several epidemiologic studies of TRAP exposure, but evaluations of RLINE's performance in such applications have been limited. This study provides an operational evaluation of RLINE in which predictions of NOx, CO and PM2.5 are compared to observations at air quality monitoring stations located near high traffic roads in Detroit, MI. For CO and NOx, model performance was best at sites close to major roads, during downwind conditions, during weekdays, and during certain seasons. For PM2.5, the ability to discern local and particularly the traffic-related portion was limited, a result of high background levels, the sparseness of the monitoring network, and large uncertainties for certain processes (e.g., formation of secondary aerosols) and non-mobile sources (e.g., area, fugitive). Overall, RLINE's performance in near-road environments suggests its usefulness for estimating spatially- and temporally-resolved exposures. The study highlights considerations relevant to health impact and epidemiologic applications, including the importance of selecting appropriate pollutants, using appropriate monitoring approaches, considering prevailing wind directions during study design, and accounting for uncertainty.

Simulating Roll Clouds associated with Low-Level Convergence.

NASA Astrophysics Data System (ADS)

Prasad, A. A.; Sherwood, S. C.

2015-12-01

Convective initiation often takes place when features such as fronts and/or rolls collide, merge or otherwise meet. Rolls indicate boundary layer convergence and may initiate thunderstorms. These are often seen in satellite and radar imagery prior to the onset of deep convection. However, links between convergence driven rolls and convection are poor in global models. The poor representation of convection is the source of many model biases, especially over the Maritime Continent in the Tropics. We simulate low-level convergence lines over north-eastern Australia using the Weather Research and Forecasting (WRF) Model (version 3.7). The simulations are events from September-October 2002 driven by sea breeze circulations. Cloud lines associated with bore-waves that form along the low-level convergence lines are thoroughly investigated in this study with comparisons from satellite and surface observations. Initial simulations for a series of cloud lines observed on 4th October, 2002 over the Gulf of Carpentaria showed greater agreement in the timing and propagation of the disturbance and the low-level convergence, however the cloud lines or streets of roll clouds were not properly captured by the model. Results from a number of WRF simulations with different microphysics, cumulus and planetary boundary layer schemes, resolution and boundary conditions will also be discussed.

Constraining the geometry and kinematics of the quasar broad emission line region using gravitational microlensing. I. Models and simulations

NASA Astrophysics Data System (ADS)

Braibant, L.; Hutsemékers, D.; Sluse, D.; Goosmann, R.

2017-11-01

Recent studies have shown that line profile distortions are commonly observed in gravitationally lensed quasar spectra. Often attributed to microlensing differential magnification, line profile distortions can provide information on the geometry and kinematics of the broad emission line region (BLR) in quasars. We investigate the effect of gravitational microlensing on quasar broad emission line profiles and their underlying continuum, combining the emission from simple representative BLR models with generic microlensing magnification maps. Specifically, we considered Keplerian disk, polar, and equatorial wind BLR models of various sizes. The effect of microlensing has been quantified with four observables: μBLR, the total magnification of the broad emission line; μcont, the magnification of the underlying continuum; as well as red/blue, RBI and wings/core, WCI, indices that characterize the line profile distortions. The simulations showed that distortions of line profiles, such as those recently observed in lensed quasars, can indeed be reproduced and attributed to the differential effect of microlensing on spatially separated regions of the BLR. While the magnification of the emission line μBLR sets an upper limit on the BLR size and, similarly, the magnification of the continuum μcont sets an upper limit on the size of the continuum source, the line profile distortions mainly depend on the BLR geometry and kinematics. We thus built (WCI,RBI) diagrams that can serve as diagnostic diagrams to discriminate between the various BLR models on the basis of quantitative measurements. It appears that a strong microlensing effect puts important constraints on the size of the BLR and on its distance to the high-magnification caustic. In that case, BLR models with different geometries and kinematics are more prone to produce distinctive line profile distortions for a limited number of caustic configurations, which facilitates their discrimination. When the microlensing effect is weak, there is a larger overlap between the characteristics of the line profile distortions produced by the different models, and constraints can only be derived on a statistical basis.

STELLAR SURFACE MAGNETO-CONVECTION AS A SOURCE OF ASTROPHYSICAL NOISE. I. MULTI-COMPONENT PARAMETERIZATION OF ABSORPTION LINE PROFILES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cegla, H. M.; Shelyag, S.; Watson, C. A.

2013-02-15

We outline our techniques to characterize photospheric granulation as an astrophysical noise source. A four-component parameterization of granulation is developed that can be used to reconstruct stellar line asymmetries and radial velocity shifts due to photospheric convective motions. The four components are made up of absorption line profiles calculated for granules, magnetic intergranular lanes, non-magnetic intergranular lanes, and magnetic bright points at disk center. These components are constructed by averaging Fe I 6302 A magnetically sensitive absorption line profiles output from detailed radiative transport calculations of the solar photosphere. Each of the four categories adopted is based on magnetic fieldmore » and continuum intensity limits determined from examining three-dimensional magnetohydrodynamic simulations with an average magnetic flux of 200 G. Using these four-component line profiles we accurately reconstruct granulation profiles, produced from modeling 12 Multiplication-Sign 12 Mm{sup 2} areas on the solar surface, to within {approx} {+-}20 cm s{sup -1} on a {approx}100 m s{sup -1} granulation signal. We have also successfully reconstructed granulation profiles from a 50 G simulation using the parameterized line profiles from the 200 G average magnetic field simulation. This test demonstrates applicability of the characterization to a range of magnetic stellar activity levels.« less

MEASUREMENTS OF CO REDSHIFTS WITH Z-SPEC FOR LENSED SUBMILLIMETER GALAXIES DISCOVERED IN THE H-ATLAS SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupu, R. E.; Scott, K. S.; Aguirre, J. E.

2012-10-01

We present new observations from Z-Spec, a broadband 185-305 GHz spectrometer, of five submillimeter bright lensed sources selected from the Herschel-Astrophysical Terahertz Large Area Survey science demonstration phase catalog. We construct a redshift-finding algorithm using combinations of the signal to noise of all the lines falling in the Z-Spec bandpass to determine redshifts with high confidence, even in cases where the signal to noise in individual lines is low. We measure the dust continuum in all sources and secure CO redshifts for four out of five (z {approx} 1.5-3). In one source, SDP.17, we tentatively identify two independent redshifts andmore » a water line, confirmed at z = 2.308. Our sources have properties characteristic of dusty starburst galaxies, with magnification-corrected star formation rates of 10{sup 2-3} M{sub Sun} yr{sup -1}. Lower limits for the dust masses ({approx} a few 10{sup 8} M{sub Sun }) and spatial extents ({approx}1 kpc equivalent radius) are derived from the continuum spectral energy distributions, corresponding to dust temperatures between 54 and 69 K. In the local thermodynamic equilibrium (LTE) approximation, we derive relatively low CO excitation temperatures ({approx}< 100 K) and optical depths ({tau} {approx}< 1). Performing a non-LTE excitation analysis using RADEX, we find that the CO lines measured by Z-Spec (from J = 4 {yields} 3 to 10 {yields} 9, depending on the galaxy) localize the best solutions to either a high-temperature/low-density region or a low/temperature/high-density region near the LTE solution, with the optical depth varying accordingly. Observations of additional CO lines, CO(1-0) in particular, are needed to constrain the non-LTE models.« less

Ionized absorbers, ionized emitters, and the X-ray spectrum of active galactic nuclei

NASA Technical Reports Server (NTRS)

Netzer, Hagai

1993-01-01

Broad absorption features are common in the X-ray spectrum of low-luminosity AGNs. The features have been modeled by leaky neutral absorbers or by highly ionized gas that completely occult the continuum source. Such models are incomplete since they do not take into account all the physical processes in the gas. In particular, no previous model included the X-ray emission by the ionized absorbing gas and the reflection of the continuum source radiation. The present work discusses the emission, absorption, and reflection properties of photoionized gases with emphasis on conditions thought to prevail in AGNs. It shows that such gas is likely to produce intense X-ray line and continuum radiation and to reflect a sizable fraction of the nonstellar continuum at all energies. If such gas is indeed responsible for the observed X-ray absorption, then absorption edges are much weaker than commonly assumed, and some residual X-ray continuum is likely to be observed even if the line of sight is completely blocked. Moreover, X-ray emission features may show up in sources not showing X-ray absorption. This has immense consequences for medium-resolution X-ray missions, such as BBXRT and Astro-D, and for the planned high-resolution experiments on board XMM and AXAF.

Development of a Converter-Based Transmission Line Emulator with Three-Phase Short-Circuit Fault Emulation Capability

DOE PAGES

Zhang, Shuoting; Liu, Bo; Zheng, Sheng; ...

2018-01-01

A transmission line emulator has been developed to flexibly represent interconnected ac lines under normal operating conditions in a voltage source converter (VSC)-based power system emulation platform. As the most serious short-circuit fault condition, the three-phase short-circuit fault emulation is essential for power system studies. Here, this paper proposes a model to realize a three-phase short-circuit fault emulation at different locations along a single transmission line or one of several parallel-connected transmission lines. At the same time, a combination method is proposed to eliminate the undesired transients caused by the current reference step changes while switching between the fault statemore » and the normal state. Experiment results verify the developed transmission line three-phase short-circuit fault emulation capability.« less

Development of a Converter-Based Transmission Line Emulator with Three-Phase Short-Circuit Fault Emulation Capability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shuoting; Liu, Bo; Zheng, Sheng

A transmission line emulator has been developed to flexibly represent interconnected ac lines under normal operating conditions in a voltage source converter (VSC)-based power system emulation platform. As the most serious short-circuit fault condition, the three-phase short-circuit fault emulation is essential for power system studies. Here, this paper proposes a model to realize a three-phase short-circuit fault emulation at different locations along a single transmission line or one of several parallel-connected transmission lines. At the same time, a combination method is proposed to eliminate the undesired transients caused by the current reference step changes while switching between the fault statemore » and the normal state. Experiment results verify the developed transmission line three-phase short-circuit fault emulation capability.« less

XMM-Newton Proposal 03033401

NASA Astrophysics Data System (ADS)

Ghosh, Kajal

2004-10-01

We have detected a highly blueshifted (7.6 keV at the source frame) emission feature in the ASCA spectra of the unusual Narrow-line Seyfert 1 galaxy RX J0136.9-3510. At ASCA resolution it is impossible to tell if the feature is a single line or a combination of lines nor if the feature is due to He-like or H-like Fe. The line profile can tell us where the bulk of the emission origin- ates: A low velocity dispersion would favor a wind/outflow origin, while a hi- gher dispersion may allow for an ionized disk reflection origin. Strong absor- ption and resonant scattering could also produce blueshifted line. To acquire better resolution spectrum to constrain the origin of the line via detailed physical modeling, we propose 50 ks XMM-Newton observations of RXJ0136.9-3510.

Payload/orbiter contamination control assessment support

NASA Technical Reports Server (NTRS)

Rantanen, R. O.; Ress, E. B.

1975-01-01

The development and use is described of a basic contamination mathematical model of the shuttle orbiter which incorporates specific shuttle orbiter configurations and contamination sources. These configurations and sources were evaluated with respect to known shuttle orbiter operational surface characteristics and specific lines-of-sight which encompass the majority of viewing requirements for shuttle payloads. The results of these evaluations are presented as summary tables for each major source. In addition, contamination minimization studies were conducted and recommendations are made, where applicable, to support the shuttle orbiter design and operational planning for those sources which were identified to present a significant contamination threat.

Generation and characterization of rat liver stem cell lines and their engraftment in a rat model of liver failure

PubMed Central

Kuijk, Ewart W.; Rasmussen, Shauna; Blokzijl, Francis; Huch, Meritxell; Gehart, Helmuth; Toonen, Pim; Begthel, Harry; Clevers, Hans; Geurts, Aron M.; Cuppen, Edwin

2016-01-01

The rat is an important model for liver regeneration. However, there is no in vitro culture system that can capture the massive proliferation that can be observed after partial hepatectomy in rats. We here describe the generation of rat liver stem cell lines. Rat liver stem cells, which grow as cystic organoids, were characterized by high expression of the stem cell marker Lgr5, by the expression of liver progenitor and duct markers, and by low expression of hepatocyte markers, oval cell markers, and stellate cell markers. Prolonged cultures of rat liver organoids depended on high levels of WNT-signalling and the inhibition of BMP-signaling. Upon transplantation of clonal lines to a Fah−/− Il2rg−/− rat model of liver failure, the rat liver stem cells engrafted into the host liver where they differentiated into areas with FAH and Albumin positive hepatocytes. Rat liver stem cell lines hold potential as consistent reliable cell sources for pharmacological, toxicological or metabolic studies. In addition, rat liver stem cell lines may contribute to the development of regenerative medicine in liver disease. To our knowledge, the here described liver stem cell lines represent the first organoid culture system in the rat. PMID:26915950

Oxygen spectral line synthesis: 3D non-LTE with CO5BOLD hydrodynamical model atmospheres.

NASA Astrophysics Data System (ADS)

Prakapavičius, D.; Steffen, M.; Kučinskas, A.; Ludwig, H.-G.; Freytag, B.; Caffau, E.; Cayrel, R.

In this work we present first results of our current project aimed at combining the 3D hydrodynamical stellar atmosphere approach with non-LTE (NLTE) spectral line synthesis for a number of key chemical species. We carried out a full 3D-NLTE spectrum synthesis of the oxygen IR 777 nm triplet, using a modified and improved version of our NLTE3D package to calculate departure coefficients for the atomic levels of oxygen in a CO5BOLD 3D hydrodynamical solar model atmosphere. Spectral line synthesis was subsequently performed with the Linfor3D code. In agreement with previous studies, we find that the lines of the oxygen triplet produce deeper cores under NLTE conditions, due to the diminished line source function in the line forming region. This means that the solar oxygen IR 777 nm lines should be stronger in NLTE, leading to negative 3D NLTE-LTE abundance corrections. Qualitatively this result would support previous claims for a relatively low solar oxygen abundance. Finally, we outline several further steps that need to be taken in order to improve the physical realism and numerical accuracy of our current 3D-NLTE calculations.

The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines

NASA Technical Reports Server (NTRS)

Markowitz, Alex; Reeves, James N.; Miniutti, Giovanni; Serlemitsos, Peter; Kunieda, Hideyo; Taqoob, Tahir; Fabian, Andrew C.; Fukazawa, Yasushi; Mushotzky, Richard; Okajima, Takashi;

The red and green lines of atomic oxygen in the nightglow of Venus

NASA Technical Reports Server (NTRS)

Fox, J. L.

1990-01-01

O(1D) and O(1S), the excited states that give rise to the atomic oxygen red and green lines, are produced in the Venus nightglow in dissociative recombination of O2(+). The emissions should also be excited by precipitation of soft electrons, the suggested source of the 'auroral' emission features of atomic oxygen at 1304 and 1356 A, which have been reported from observations of the Pioneer Venus Orbiter Ultraviolet Spectrometer. No emisison at 6300 or 5577 A was detected, however, by the visible spectrophotometers on the Soviet spacecraft Veneras 9 and 10; upper limits have been placed on the intensities of these features. The constraints placed on models for the auroral production mechanism by the Venera upper limits by modeling the intensities of the red and green lines in the nightglow are evaluated, combining a model for the vibrational distribution of O2(+) on the nightside of Venus with rate coefficients recently computed by Guberman for production of O(1S) and O(1D) in dissociative recombination of O2(+) from different vibrational levels. The integrated overhead intensities are 1 - 2 R for the green line and about 46 R for the red line.

Combining harmonic generation and laser chirping to achieve high spectral density in Compton sources

DOE PAGES

Terzić, Balša; Reeves, Cody; Krafft, Geoffrey A.

2016-04-25

Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. Moreover, as a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results tomore » demonstrate that the laser chirping in Compton sources at high laser intensities: (i) enables the use of higher order harmonics, thereby reducing the required electron beam energies; and (ii) increases the photon yield in a small frequency band beyond that possible with the fundamental without chirping. We found that this combination of chirping and higher harmonics can lead to substantial savings in the design, construction and operational costs of the new Compton sources. This is of particular importance to the widely popular laser-plasma accelerator based Compton sources, as the improvement in their beam quality enters the regime where chirping is most effective.« less

QSO Broad Emission Line Asymmetries: Evidence of Gravitational Redshift?

NASA Astrophysics Data System (ADS)

Corbin, Michael R.

1995-07-01

The broad optical and ultraviolet emission lines of QSOs and active galactic nuclei (AGNs) display both redward and blueward asymmetries. This result is particularly well established for Hβ and C IV λ1549, and it has been found that Hβ becomes increasingly redward asymmetric with increasing soft X-ray luminosity. Two models for the origin of these asymmetries are investigated: (1) Anisotropic line emission from an ensemble of radially moving clouds, and (2) Two-component profiles consisting of a core of intermediate (˜1000-4000 km s-1) velocity width and a very broad (˜5000-20,000 km s-1) base, in which the asymmetries arise due to a velocity difference between the centroids of the components. The second model is motivated by the evidence that the traditional broad-line region is actually composed of an intermediate-line region (ILR) of optically thick clouds and a very broad line region (VBLR) of optically thin clouds lying closer to the central continuum source. Line profiles produced by model (1) are found to be inconsistent with those observed, being asymmetric mainly in their cores, whereas the asymmetries of actual profiles arise mainly from excess emission in their wings. By contrast, numerical fitting to actual Hβ and C IV λ1549 line profiles reveals that the majority can be accurately modeled by two components, either two Gaussians or the combination of a Gaussian base and a logarithmic core. The profile asymmetries in Hβ can be interpreted as arising from a shift of the base component over a range ˜6300 km s-1 relative to systemic velocity as defined by the position of the [O III] λ5007 line. A similar model appears to apply to C IV λ1549. The correlation between Hβ asymmetry and X-ray luminosity may thus be interpreted as a progressive red- shift of the VBLR velocity centroid relative to systemic velocity with increasing X-ray luminosity. This in turn suggests that the underlying effect is gravitational red shift, as soft X-ray emission arises from a region ˜ light-minutes in size and arguably traces the mass of the putative supermassive black hole. Depending on the size of the VBLR and the exact amount of its profile centroid shift, central masses in the range 109-10 Msun are implied for the objects displaying the strongest redward profile asymmetries, consistent with other estimates. The largest VBLR velocity dispersions measured from the two-component modeling are ˜20,000 km s-1, which also yields a virial mass ˜109 Msun for a VBLR size 0.1 pc. The gravitational redshift model does not explain the origin of the blueshift of the VBLR emission among low X-ray luminosity sources, however. This must be interpreted as arising from a competing effect such as electron scattering of line photons in the vicinity of the VBLR. On average, radio-loud objects have redward asymmetric broad-line profiles and stronger intermediate- and narrow-line emission than radio-quiet objects of comparable optical luminosity. Under the gravitational redshift model these differences may be interpreted as the result of black hole and host galaxy masses that are larger on average among the former class, consistent with the evidence that they are merger products.

An empirical model for calculation of the collimator contamination dose in therapeutic proton beams

NASA Astrophysics Data System (ADS)

Vidal, M.; De Marzi, L.; Szymanowski, H.; Guinement, L.; Nauraye, C.; Hierso, E.; Freud, N.; Ferrand, R.; François, P.; Sarrut, D.

2016-02-01

Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times.

A Three-phase Chemical Model of Hot Cores: The Formation of Glycine

NASA Astrophysics Data System (ADS)

Garrod, Robin T.

2013-03-01

A new chemical model is presented that simulates fully coupled gas-phase, grain-surface, and bulk-ice chemistry in hot cores. Glycine (NH2CH2COOH), the simplest amino acid, and related molecules such as glycinal, propionic acid, and propanal, are included in the chemical network. Glycine is found to form in moderate abundance within and upon dust-grain ices via three radical-addition mechanisms, with no single mechanism strongly dominant. Glycine production in the ice occurs over temperatures ~40-120 K. Peak gas-phase glycine fractional abundances lie in the range 8 × 10-11-8 × 10-9, occurring at ~200 K, the evaporation temperature of glycine. A gas-phase mechanism for glycine production is tested and found insignificant, even under optimal conditions. A new spectroscopic radiative-transfer model is used, allowing the translation and comparison of the chemical-model results with observations of specific sources. Comparison with the nearby hot-core source NGC 6334 IRS1 shows excellent agreement with integrated line intensities of observed species, including methyl formate. The results for glycine are consistent with the current lack of a detection of this molecule toward other sources; the high evaporation temperature of glycine renders the emission region extremely compact. Glycine detection with ALMA is predicted to be highly plausible, for bright, nearby sources with narrow emission lines. Photodissociation of water and subsequent hydrogen abstraction from organic molecules by OH, and NH2, are crucial to the buildup of complex organic species in the ice. The inclusion of alternative branches within the network of radical-addition reactions appears important to the abundances of hot-core molecules; less favorable branching ratios may remedy the anomalously high abundance of glycolaldehyde predicted by this and previous models.

Coverage Maximization Using Dynamic Taint Tracing

DTIC Science & Technology

2007-03-28

we do not have source code are handled, incompletely, via models of taint transfer. We use a little language to specify how taint transfers across a...n) 2.3.7 Implementation and Runtime Issues The taint graph instrumentation is a 2K line Ocaml module extending CIL and is supported by 5K lines of...modern scripting languages such as Ruby have taint modes that work similarly; however, all propagate taint at the variable rather than the byte level and

DISCOVERY OF RELATIVISTIC OUTFLOW IN THE SEYFERT GALAXY Ark 564

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, A.; Mathur, S.; Krongold, Y.

2013-07-20

We present Chandra High Energy Transmission Grating Spectra of the narrow-line Seyfert-1 galaxy Ark 564. The spectrum shows numerous absorption lines which are well modeled with low-velocity outflow components usually observed in Seyfert galaxies. There are, however, some residual absorption lines which are not accounted for by low-velocity outflows. Here, we present identifications of the strongest lines as K{alpha} transitions of O VII (two lines) and O VI at outflow velocities of {approx}0.1c. These lines are detected at 6.9{sigma}, 6.2{sigma}, and 4.7{sigma}, respectively, and cannot be due to chance statistical fluctuations. Photoionization models with ultra-high velocity components improve the spectralmore » fit significantly, providing further support for the presence of relativistic outflow in this source. Without knowing the location of the absorber, its mass and energy outflow rates cannot be well constrained; we find E-dot (outflow)/L{sub bol} lower limit of {>=}0.006% assuming a bi-conical wind geometry. This is the first time that absorption lines with ultra-high velocities are unambiguously detected in the soft X-ray band. The presence of outflows with relativistic velocities in active galactic nuclei (AGNs) with Seyfert-type luminosities is hard to understand and provides valuable constraints to models of AGN outflows. Radiation pressure is unlikely to be the driving mechanism for such outflows and magnetohydrodynamic may be involved.« less

Characterization of air pollutant concentrations, fleet emission factors, and dispersion near a North Carolina interstate freeway across two seasons

NASA Astrophysics Data System (ADS)

Saha, Provat K.; Khlystov, Andrey; Snyder, Michelle G.; Grieshop, Andrew P.

2018-03-01

We present field measurement data and modeling of multiple traffic-related air pollutants during two seasons at a site adjoining Interstate 40, near Durham, North Carolina. We analyze spatial-temporal and seasonal trends and fleet-average pollutant emission factors and use our data to evaluate a line source dispersion model. Month-long measurement campaigns were performed in summer 2015 and winter 2016. Data were collected at a fixed near-road site located within 10 m from the highway edge, an upwind background site and, under favorable meteorological conditions, along downwind perpendicular transects. Measurements included the size distribution, chemical composition, and volatility of submicron particles, black carbon (BC), nitrogen oxides (NOx), meteorological conditions and traffic activity data. Results show strong seasonal and diurnal differences in spatial distribution of traffic sourced pollutants. A strong signature of vehicle emissions was observed within 100-150 m from the highway edge with significantly higher concentrations during morning. Substantially higher concentrations and less-sharp near-road gradients were observed in winter for many species. Season-specific fleet-average fuel-based emission factors for NO, NOx, BC, and particle number (PN) were derived based on up- and down-wind roadside measurements. The campaign-average NOx and PN emission factors were 20% and 300% higher in winter than summer, respectively. These results suggest that the combined effect of higher emissions and their slower downwind dispersion in winter dictate the observed higher downwind concentrations and wider highway influence zone in winter for several species. Finally, measurements of traffic data, emission factors, and pollutant concentrations were integrated to evaluate a line source dispersion model (R-LINE). The dispersion model captured the general trends in the spatial and temporal patterns in near-road concentrations. However, there was a tendency for the model to under-predict concentrations near the road in the mornings and over-predict concentrations in the evenings.

Improved methods for the measurement and analysis of stellar magnetic fields

NASA Technical Reports Server (NTRS)

Saar, Steven H.

1988-01-01

The paper presents several improved methods for the measurement of magnetic fields on cool stars which take into account simple radiative transfer effects and the exact Zeeman patterns. Using these methods, high-resolution, low-noise data can be fitted with theoretical line profiles to determine the mean magnetic field strength in stellar active regions and a model-dependent fraction of the stellar surface (filling factor) covered by these regions. Random errors in the derived field strength and filling factor are parameterized in terms of signal-to-noise ratio, wavelength, spectral resolution, stellar rotation rate, and the magnetic parameters themselves. Weak line blends, if left uncorrected, can have significant systematic effects on the derived magnetic parameters, and thus several methods are developed to compensate partially for them. The magnetic parameters determined by previous methods likely have systematic errors because of such line blends and because of line saturation effects. Other sources of systematic error are explored in detail. These sources of error currently make it difficult to determine the magnetic parameters of individual stars to better than about + or - 20 percent.

Infrared Spectroscopy of Black Hole Candidates

NASA Technical Reports Server (NTRS)

Colgan, Sean W.; Cotera, A. S.; Maloney, P. R.; Hollenbach, D. J.; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

ISO LWS and SWS observations of the approx. solar mass black hole candidates 1E1740.7-2942 and GRS1758-258 are presented. For 1E1740.7-2942, it has been suggested that the luminosity is provided in whole or part by Bondi-Hoyle accretion from a surrounding black hole (Bally & Leventhal 1991, Nat, 353,234). Maloney et al. (1997, ApJ482, L41) have predicted that detectable far-infrared line emission from [0I] (63 microns), [CII] (158 microns), [SiII] (35 microns) and other lines will arise from black holes which are embedded in molecular clouds. No strong line emission associated with either 1E1740.7-2942 or GRS1758-258 was detected, implying either that 1) these sources are not embedded in dense molecular clouds, or 2) that their average X-ray luminosity over the past 100 years is significantly lower than its current value. The measured upper limits to the line fluxes are compared with the models of Maloney et al.to constrain the properties of the ISM in the vicinity of these X-ray sources.

Optical identification of radio-loud active galactic nuclei in the ROSAT-Green-Bank sample with SDSS spectroscopy

NASA Astrophysics Data System (ADS)

Wang, De-Liang; Wang, Jian-Guo; Dong, Xiao-Bo

2009-10-01

Results of extended and refined optical identification of 181 radio/X-ray sources in the RASS-Green Bank (RGB) catalog are presented (Brinkmann et al. 1997) which have been spectroscopically observed in the Sloan Digital Sky Survey (SDSS) DR5. The SDSS spectra of the optical counterparts are modeled in a careful and self-consistent way by incorporating the host galaxy's starlight. Optical emission line parameters are presented, which are derived accurately and reliably, along with the radio 1.4-5 GHz spectral indices estimated using (non-simultaneous) archival data. For 72 sources, the identifications are presented for the first time. It is confirmed that the majority of strong radio/X-ray emitters are radio-loud active galactic nuclei (AGNs), particularly blazars. Taking advantage of the high spectral quality and resolution and our refined spectral modeling, we are able to disentangle narrow line radio galaxies (NLRGs), as vaguely termed in most previous identification work, into Seyfert II galaxies and LINERs (low-ionization nuclear emission regions), based on the standard emission line diagnostics. The NLRGs in the RGB sample, mostly belonging to 'weak line radio galaxies', are found to have optical spectra consistent predominantly with LINERs, and only a small fraction with Seyfert II galaxies. A small number of LINERs have radio power as high as 1023 - 1026 W Hz-1 at 5 GHz, being among the strongest radio emitting LINERs known so far. Two sources are identified with radio-loud narrow line Seyfert 1 galaxies (NLS1s), a class of rare objects. The presence is also confirmed of flat-spectrum radio quasars whose radio-optical-X-ray effective spectral indices are similar to those of High-energy peaked BL Lacs (HBLs), as suggested by Padovani et al., although it is still a debate as to whether this is the case for their actual spectral energy distributions.

Far-infrared observations of a star-forming region in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

1984-01-01

A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

An interpretation of flare-induced and decayless coronal-loop oscillations as interference patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hindman, Bradley W.; Jain, Rekha, E-mail: hindman@solarz.colorado.edu

2014-04-01

We present an alternative model of coronal-loop oscillations, which considers that the waves are trapped in a two-dimensional waveguide formed by the entire arcade of field lines. This differs from the standard one-dimensional model which treats the waves as the resonant oscillations of just the visible bundle of field lines. Within the framework of our two-dimensional model, the two types of oscillations that have been observationally identified, flare-induced waves and 'decayless' oscillations, can both be attributed to MHD fast waves. The two components of the signal differ only because of the duration and spatial extent of the source that createsmore » them. The flare-induced waves are generated by strong localized sources of short duration, while the decayless background can be excited by a continuous, stochastic source. Further, the oscillatory signal arising from a localized, short-duration source can be interpreted as a pattern of interference fringes produced by waves that have traveled diverse routes of various pathlengths through the waveguide. The resulting amplitude of the fringes slowly decays in time with an inverse square root dependence. The details of the interference pattern depend on the shape of the arcade and the spatial variation of the Alfvén speed. The rapid decay of this wave component, which has previously been attributed to physical damping mechanisms that remove energy from resonant oscillations, occurs as a natural consequence of the interference process without the need for local dissipation.« less

Open source machine-learning algorithms for the prediction of optimal cancer drug therapies.

PubMed

Huang, Cai; Mezencev, Roman; McDonald, John F; Vannberg, Fredrik

2017-01-01

Precision medicine is a rapidly growing area of modern medical science and open source machine-learning codes promise to be a critical component for the successful development of standardized and automated analysis of patient data. One important goal of precision cancer medicine is the accurate prediction of optimal drug therapies from the genomic profiles of individual patient tumors. We introduce here an open source software platform that employs a highly versatile support vector machine (SVM) algorithm combined with a standard recursive feature elimination (RFE) approach to predict personalized drug responses from gene expression profiles. Drug specific models were built using gene expression and drug response data from the National Cancer Institute panel of 60 human cancer cell lines (NCI-60). The models are highly accurate in predicting the drug responsiveness of a variety of cancer cell lines including those comprising the recent NCI-DREAM Challenge. We demonstrate that predictive accuracy is optimized when the learning dataset utilizes all probe-set expression values from a diversity of cancer cell types without pre-filtering for genes generally considered to be "drivers" of cancer onset/progression. Application of our models to publically available ovarian cancer (OC) patient gene expression datasets generated predictions consistent with observed responses previously reported in the literature. By making our algorithm "open source", we hope to facilitate its testing in a variety of cancer types and contexts leading to community-driven improvements and refinements in subsequent applications.

The Müller-Lyer Illusion in a Computational Model of Biological Object Recognition

PubMed Central

Zeman, Astrid; Obst, Oliver; Brooks, Kevin R.; Rich, Anina N.

2013-01-01

Studying illusions provides insight into the way the brain processes information. The Müller-Lyer Illusion (MLI) is a classical geometrical illusion of size, in which perceived line length is decreased by arrowheads and increased by arrowtails. Many theories have been put forward to explain the MLI, such as misapplied size constancy scaling, the statistics of image-source relationships and the filtering properties of signal processing in primary visual areas. Artificial models of the ventral visual processing stream allow us to isolate factors hypothesised to cause the illusion and test how these affect classification performance. We trained a feed-forward feature hierarchical model, HMAX, to perform a dual category line length judgment task (short versus long) with over 90% accuracy. We then tested the system in its ability to judge relative line lengths for images in a control set versus images that induce the MLI in humans. Results from the computational model show an overall illusory effect similar to that experienced by human subjects. No natural images were used for training, implying that misapplied size constancy and image-source statistics are not necessary factors for generating the illusion. A post-hoc analysis of response weights within a representative trained network ruled out the possibility that the illusion is caused by a reliance on information at low spatial frequencies. Our results suggest that the MLI can be produced using only feed-forward, neurophysiological connections. PMID:23457510

The propagation of sound in tunnels

NASA Astrophysics Data System (ADS)

Li, Kai Ming; Iu, King Kwong

2002-11-01

The sound propagation in tunnels is addressed theoretically and experimentally. In many previous studies, the image source method is frequently used. However, these early theoretical models are somewhat inadequate because the effect of multiple reflections in long enclosures is often modeled by the incoherent summation of contributions from all image sources. Ignoring the phase effect, these numerical models are unlikely to be satisfactory for predicting the intricate interference patterns due to contributions from each image source. In the present paper, the interference effect is incorporated by summing the contributions from the image sources coherently. To develop a simple numerical model, tunnels are represented by long rectangular enclosures with either geometrically reflecting or impedance boundaries. Scale model experiments are conducted for the validation of the numerical model. In some of the scale model experiments, the enclosure walls are lined with a carpet for simulating the impedance boundary condition. Large-scale outdoor measurements have also been conducted in two tunnels designed originally for road traffic use. It has been shown that the proposed numerical model agrees reasonably well with experimental data. [Work supported by the Research Grants Council, The Industry Department, NAP Acoustics (Far East) Ltd., and The Hong Kong Polytechnic University.

Optical spectroscopy of X-ray sources in the Taurus molecular cloud: discovery of ten new pre-main sequence stars

NASA Astrophysics Data System (ADS)

Scelsi, L.; Sacco, G.; Affer, L.; Argiroffi, C.; Pillitteri, I.; Maggio, A.; Micela, G.

2008-11-01

Aims: We have analyzed optical spectra of 25 X-ray sources identified as potential new members of the Taurus molecular cloud (TMC), in order to confirm their membership in this star-forming region. Methods: Fifty-seven candidate members were previously selected among the X-ray sources in the XEST survey, having a 2MASS counterpart compatible with a pre-main sequence star based on color-magnitude and color-color diagrams. We obtained high-resolution optical spectra for 7 of these candidates with the SARG spectrograph at the TNG telescope, which were used to search for lithium absorption and to measure the Hα line and the radial and rotational velocities. Then, 18 low-resolution optical spectra obtained with the instrument DOLORES for other candidate members were used for spectral classification, for Hα measurements, and to assess membership together with IR color-color and color-magnitude diagrams and additional information from the X-ray data. Results: We found that 3 sources show lithium absorption, with equivalent widths (EWs) of 500 mÅ, broad spectral line profiles, indicating rotational velocities of 20{-}40 km s-1, radial velocities consistent with those for known members, and Hα emission. Two of them are classified as new weak-lined T Tauri stars, while the EW ( -9 Å) of the Hα line and its broad asymmetric profile clearly indicate that the third star (XEST-26-062) is a classical T Tauri star. Fourteen sources observed with DOLORES are M-type stars. Fifteen sources show Hα emission. Six of them have spectra that indicate surface gravity lower than in main sequence stars, and their de-reddened positions in IR color-magnitude diagrams are consistent with their derived spectral type and with pre-main sequence models at the distance of the TMC. The K-type star XEST-11-078 is confirmed as a new member on the basis of the strength of the Hα emission line. Overall, we confirm membership to the TMC for 10 out of 25 X-ray sources observed in the optical. Three sources remain uncertain. Based on data collected with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque del los Muchachos of the Instituto de Astrofìsica de Canarias.

Pumping of Class 2 methanol masers. 1: The 20 - 3-1E transition

NASA Astrophysics Data System (ADS)

Sobolev, A. M.; Deguchi, S.

1994-11-01

We present a large velocity gradient (LVG) model calculations which explain observed 20 - 3-1E line brightnesses in the strongest Class II methanol masers (MMII). The model explains the variations in spectral appearance of the different maser lines observed from the same source using single-dish facilities through differences in the sensitivities of the line intensities to the MMII physical parameters. In our model masers are pumped by emission of a nearby layer of hot dust with temperature greater than 150 K. The MMII are seen in projection on the H II region producing free-free radio continuum emission. It is shown that radiative excitations from rotational levels of the ground state to the levels of the 2nd and the 1st torsionally excited states both play important role in the pump. We found that the strong MMII (Tb greater than 1010K) should be beamed. The value of (CH3OH)/H2 in the strong MMII sources should exceed 7 x 10-7. Results suggest that the chemistry of the strong MMII was influenced by the shock wave passage. The strong MMII sources should have hydrogen number densities greater than 3 x 106/cu cm and gas temperatures less than 50 K. Thus, results of the present calculations indicate that MMII clumps were exposed to some fast and efficient cooling process. We suppose that local temperature variations can explain the observed absence of spatial coincidence between the MMII and OH maser spots. The MMII with Tb greater than or equal to 109 K can be produced in the sources with the optical depth equal in all directions. Like the strong MMII they should be dense nH greater than (106/cu cm - 3), methanol-abundant ((CH3OH)/H2) greater than 10-7 and relatively cold (T less than 75 K).

Comparing WSA coronal and solar wind model predictions driven by line-of-sight and vector HMI ADAPT maps

NASA Astrophysics Data System (ADS)

Arge, C. N.; Henney, C. J.; Shurkin, K.; Wallace, S.

2017-12-01

As the primary input to nearly all coronal models, reliable estimates of the global solar photospheric magnetic field distribution are critical for accurate modeling and understanding of solar and heliospheric magnetic fields. The Air Force Data Assimilative Photospheric flux Transport (ADAPT) model generates synchronic (i.e., globally instantaneous) maps by evolving observed solar magnetic flux using relatively well understood transport processes when measurements are not available and then updating modeled flux with new observations (available from both the Earth and the far-side of the Sun) using data assimilation methods that rigorously take into account model and observational uncertainties. ADAPT is capable of assimilating line-of-sight and vector magnetic field data from all observatory sources including the expected photospheric vector magnetograms from the Polarimetric and Helioseismic Imager (PHI) on the Solar Orbiter, as well as those generated using helioseismic methods. This paper compares Wang-Sheeley-Arge (WSA) coronal and solar wind modeling results at Earth and STEREO A & B using ADAPT input model maps derived from both line-of-site and vector SDO/HMI magnetograms that include methods for incorporating observations of a large, newly emerged (July 2010) far-side active region (AR11087).

Thermal-electric coupled-field finite element modeling and experimental testing of high-temperature ion sources for the production of radioactive ion beams

NASA Astrophysics Data System (ADS)

Manzolaro, M.; Meneghetti, G.; Andrighetto, A.; Vivian, G.; D'Agostini, F.

2016-02-01

In isotope separation on line facilities the target system and the related ion source are two of the most critical components. In the context of the selective production of exotic species (SPES) project, a 40 MeV 200 μA proton beam directly impinges a uranium carbide target, generating approximately 1013 fissions per second. The radioactive isotopes produced in this way are then directed to the ion source, where they can be ionized and finally accelerated to the subsequent areas of the facility. In this work both the surface ion source and the plasma ion source adopted for the SPES facility are presented and studied by means of numerical thermal-electric models. Then, numerical results are compared with temperature and electric potential difference measurements, and finally the main advantages of the proposed simulation approach are discussed.

Iron line emission from a high temperature plasma in Cas A

NASA Technical Reports Server (NTRS)

Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Rothschild, R. E.; Serlemitsos, P. J.; Swank, J. H.

1976-01-01

The X-ray spectrum of Cassiopeia A was observed for several days by the proportional counter experiment on board OSO-8. The high energy ( 5 keV) data are fit well by a thermal spectrum. A narrow iron line which is predicted by the thermal model is also observed. The low energy (2-5 keV) data show an excess over the high temperature component which is consistent with the presence of an additional low temperature thermal component. Iron abundance in the source relative to normal cosmic abundance is discussed, as in the relation of this observation to shock wave and multi-component thermal models for supernova remnants.

Solution of the comoving-frame equation of transfer in spherically symmetric flows. V - Multilevel atoms. [in early star atmospheres

NASA Technical Reports Server (NTRS)

Mihalas, D.; Kunasz, P. B.

1978-01-01

The coupled radiative transfer and statistical equilibrium equations for multilevel ionic structures in the atmospheres of early-type stars are solved. Both lines and continua are treated consistently; the treatment is applicable throughout a transonic wind, and allows for the presence of background continuum sources and sinks in the transfer. An equivalent-two-level-atoms approach provides the solution for the equations. Calculations for simplified He (+)-like model atoms in parameterized isothermal wind models indicate that subordinate line profiles are sensitive to the assumed mass-loss rate, and to the assumed structure of the velocity law in the atmospheres.

Next Generation Air Measurements for Fugitive, Area Source, and Fence Line Applications

EPA Science Inventory

Next generation air measurements (NGAM) is an EPA term for the advancing field of air pollutant sensor technologies, data integration concepts, and geospatial modeling strategies. Ranging from personal sensors to satellite remote sensing, NGAM systems may provide revolutionary n...

Computer Analysis of Air Pollution from Highways, Streets, and Complex Interchanges

DOT National Transportation Integrated Search

1974-03-01

A detailed computer analysis of air quality for a complex highway interchange was prepared, using an in-house version of the Environmental Protection Agency's Gaussian Highway Line Source Model. This analysis showed that the levels of air pollution n...

Comparison of Highly Resolved Model-Based Exposure ...

EPA Pesticide Factsheets

Human exposure to air pollution in many studies is represented by ambient concentrations from space-time kriging of observed values. Space-time kriging techniques based on a limited number of ambient monitors may fail to capture the concentration from local sources. Further, because people spend more time indoors, using ambient concentration to represent exposure may cause error. To quantify the associated exposure error, we computed a series of six different hourly-based exposure metrics at 16,095 Census blocks of three Counties in North Carolina for CO, NOx, PM2.5, and elemental carbon (EC) during 2012. These metrics include ambient background concentration from space-time ordinary kriging (STOK), ambient on-road concentration from the Research LINE source dispersion model (R-LINE), a hybrid concentration combining STOK and R-LINE, and their associated indoor concentrations from an indoor infiltration mass balance model. Using a hybrid-based indoor concentration as the standard, the comparison showed that outdoor STOK metrics yielded large error at both population (67% to 93%) and individual level (average bias between −10% to 95%). For pollutants with significant contribution from on-road emission (EC and NOx), the on-road based indoor metric performs the best at the population level (error less than 52%). At the individual level, however, the STOK-based indoor concentration performs the best (average bias below 30%). For PM2.5, due to the relatively low co

A Fractal Interpretation of Controlled-Source Helicopter Electromagnetic Survey Data: Seco Creek, Edwards Aquifer, TX

NASA Astrophysics Data System (ADS)

Decker, K. T.; Everett, M. E.

2009-12-01

The Edwards aquifer lies in the structurally complex Balcones fault zone and supplies water to the growing city of San Antonio. To ensure that future demands for water are met, the hydrological and geophysical properties of the aquifer must be well-understood. In most settings, fracture lengths and displacements occur in power-law distributions. Fracture distribution plays an important role in determining electrical and hydraulic current flowpaths. 1-D synthetic models of the controlled-source electromagnetic (CSEM) response for layered models with a fractured layer at depth described by the roughness parameter βV, such that 0≤βV<1, associated with the power-law length-scale dependence of electrical conductivity are developed. A value of βV = 0 represents homogeneous, continuous media, while a value of 0<βV<1 shows that roughness exists. The Seco Creek frequency-domain helicopter electromagnetic survey data set is analyzed by introducing the similarly defined roughness parameter βH to detect lateral roughness along survey lines. Fourier transforming the apparent resistivity as a function of position along flight line into wavenumber domain using a 256-point sliding window gives the power spectral density (PSD) plot for each line. The value of βH is the slope of the least squares regression for the PSD in each 256-point window. Changes in βH with distance along the flight line are plotted. Large values of βH are found near well-known large fractures and maps of βH produced by interpolating values of βH along survey lines suggest previously undetected structure at depth.

Drag Coefficient Comparisons Between Observed and Model Simulated Directional Wave Spectra Under Hurricane Conditions

DTIC Science & Technology

2016-04-19

of the ix flight segments ( white dots P1 to P6 shown in Fig. 3 ) to com- are the directional wave spectrum between the model and the RA measurement. At...September 14; and using constructed model spectra set C for (b) September 9, (d) September 12, and (f) September 14. The thick white line is the...model for hurri- cane conditions. The calibration factors (proportionality constants of the source functions) are determined from a comparison of modeled

Interstellar Scattering Towards the Galactic Center as Probed by OH/IR Stars

NASA Technical Reports Server (NTRS)

Vanlangevelde, Huib Jan; Frail, Dale A.; Cordes, James M.; Diamond, Philip J.

1992-01-01

Angular broadening measurements are reported of 20 OH/IR stars near the galactic center. This class of sources is known to have bright, intrinsically compact (less than or equal to 20 mas) maser components within their circumstellar shells. VLBA antennas and the VLA were used to perform a MKII spectral line VLBI experiment. The rapid drop in correlated flux with increasing baseline, especially for sources closest to the galactic center, is attributed to interstellar scattering. Angular diameters were measured for 13 of our sources. Lower limits were obtained for the remaining seven. With the data, together with additional data taken from the literature, the distribution was determined of interstellar scattering toward the galactic center. A region was found of pronounced scattering nearly centered on SgrA*. Two interpretations are considered for the enhanced scattering. One hypothesis is that the scattering is due to a clump of enhanced turbulence, such as those that lie along lines of sight to other known objects, that has no physical relationship to the galactic center. The other model considers the location of the enhanced scattering to arise in the galactic center itself. The physical implications of the models yield information on the nature of interstellar scattering.

RXTE Observations of the 1A 1118-61 in an Outburst, and the Discovery of a Cyclotron Line

NASA Technical Reports Server (NTRS)

Doroshenko, V.; Suchy, S.; Santangelo, A; Staubert, R.; Kreykenbohm, I.; Rothschild, R.; Pottschmidt, K.; Wilms, J.

2010-01-01

We present the analysis of RXTE monitoring data obtained during the January 2009 outburst of the hard X-ray transient IA 1118-61. Using these observations the broadband (3.5-120 keV) spectrum of the source was measured for the first time ever. We have found that the broadband continuum spectrum of the source is similar to other accreting pulsars and is well described by several conventionally used phenomenological models. We have discovered that regardless of the applied continuum model, a prominent broad absorption feature at approx. 55 keV is observed. We interpret this feature as a Cyclotron Resonance Scattering Feature (CRSF). The observed CRSF energy is one of the highest known and corresponds to a magnetic field of B approx. 4.8 x 10(exp 12) G in the scattering region. Furthermore, our data suggests an iron emission line presence, which was not reported previously for lA 1118-61 as well. Timing properties of the source, including a strong spin-up, were found to be similar to those observed by CGRO/BATSE during the previous outburst, however the broadband capabilities of RXTE reveal a more complicated energy dependency of the pulse-profile.

Radiometric observations of the 752.033-GHz rotational absorption line of H2O from a laboratory jet. [simulation of rocket plumes

NASA Technical Reports Server (NTRS)

Dionne, G. F.; Fitzgerald, J. F.; Chang, T.-S.; Fetterman, H. R.; Litvak, M. M.

1980-01-01

With the aid of a high-resolution two-stage heterodyne radiometer, spectral absorption measurements of the 752.033 GHz line of water vapor were carried out, using a blackbody continuum as a background radiation source for investigating the absorptive properties of the H2O content of high altitude rocket plumes. To simulate this physical situation in a laboratory environment, a small steam jet was operated within a large high-vacuum chamber, with the H2O jet plume traversing the radiometer line of sight. The experiments verified that this rotational line is optically thick, with excitation temperatures below 100 K, in the downstream part of the plume, as predicted by theoretical modelling.

chemalot and chemalot_knime: Command line programs as workflow tools for drug discovery.

PubMed

Lee, Man-Ling; Aliagas, Ignacio; Feng, Jianwen A; Gabriel, Thomas; O'Donnell, T J; Sellers, Benjamin D; Wiswedel, Bernd; Gobbi, Alberto

2017-06-12

Analyzing files containing chemical information is at the core of cheminformatics. Each analysis may require a unique workflow. This paper describes the chemalot and chemalot_knime open source packages. Chemalot is a set of command line programs with a wide range of functionalities for cheminformatics. The chemalot_knime package allows command line programs that read and write SD files from stdin and to stdout to be wrapped into KNIME nodes. The combination of chemalot and chemalot_knime not only facilitates the compilation and maintenance of sequences of command line programs but also allows KNIME workflows to take advantage of the compute power of a LINUX cluster. Use of the command line programs is demonstrated in three different workflow examples: (1) A workflow to create a data file with project-relevant data for structure-activity or property analysis and other type of investigations, (2) The creation of a quantitative structure-property-relationship model using the command line programs via KNIME nodes, and (3) The analysis of strain energy in small molecule ligand conformations from the Protein Data Bank database. The chemalot and chemalot_knime packages provide lightweight and powerful tools for many tasks in cheminformatics. They are easily integrated with other open source and commercial command line tools and can be combined to build new and even more powerful tools. The chemalot_knime package facilitates the generation and maintenance of user-defined command line workflows, taking advantage of the graphical design capabilities in KNIME. Graphical abstract Example KNIME workflow with chemalot nodes and the corresponding command line pipe.

A Non-linear Lifting Line Model for Design and Analysis of Trochoidal Propulsors

NASA Astrophysics Data System (ADS)

Roesler, Bernard; Epps, Brenden

2014-11-01

Flapping wing propulsors may increase the propulsive efficiency of large shipping vessels. A comparison of the design of a notional propulsor for a large shipping vessel with (a) a conventional ducted propeller versus (b) a flapping wing propulsor is presented. Calculations for flapping wing propulsors are performed using an open-source MATLAB software suite developed by the authors, CyROD, implementing an unsteady lifting-line model with free vortex wake roll-up to study the non-linear effects of foil-wake, and foil-foil interactions. Improvements to the traditional lifting line theory are made using further discretization of the wake vortex ring spacing near the trailing edge. Considerations of packaging options for a flapping wing propulsor on a large shipping vessel are presented, and compared with those for a conventional ducted propeller.

Acoustic radiation from lined, unflanged ducts: Acoustic source distribution program

NASA Technical Reports Server (NTRS)

Beckemeyer, R. J.; Sawdy, D. T.

1971-01-01

An acoustic radiation analysis was developed to predict the far-field characteristics of fan noise radiated from an acoustically lined unflanged duct. This analysis is comprised of three modular digital computer programs which together provide a capability of accounting for the impedance mismatch at the duct exit plane. Admissible duct configurations include circular or annular, with or without an extended centerbody. This variation in duct configurations provides a capability of modeling inlet and fan duct noise radiation. The computer programs are described in detail.

An outburst scenario for the X-ray spectral variability in 3C 111

NASA Astrophysics Data System (ADS)

Tombesi, F.; Reeves, J. N.; Reynolds, C. S.; García, J.; Lohfink, A.

2013-09-01

We present a combined Suzaku and Swift BAT broad-band E = 0.6-200 keV spectral analysis of three 3C 111 observations obtained in 2010. The data are well described with an absorbed power-law continuum and a weak (R ≃ 0.2) cold reflection component from distant material. We constrain the continuum cutoff at EC ≃ 150-200 keV, which is in accordance with X-ray Comptonization corona models and supports claims that the jet emission is only dominant at much higher energies. Fe XXVI Lyα emission and absorption lines are also present in the first and second observations, respectively. The modelling and interpretation of the emission line is complex and we explore three possibilities. If originating from ionized-disc reflection, this should be emitted at rin ≥ 50 rg or, in the lamp-post configuration, the illuminating source should be at a height of h ≥ 30 rg above the black hole. Alternatively, the line could be modelled with a hot collisionally ionized plasma with temperature kT = 22.0^{+6.1}_{-3.2} keV or a photoionized plasma with log ξ = 4.52^{+0.10}_{-0.16} erg s-1 cm and column density NH > 3 × 1023 cm-2. However, the first and second scenarios are less favoured on statistical and physical grounds, respectively. The blueshifted absorption line in the second observation can be modelled as an ultrafast outflow (UFO) with ionization parameter log ξ = 4.47^{+0.76}_{-0.04} erg s-1 cm, column density N_H = (5.3^{+1.8}_{-1.3})× 10^{22} cm-2 and outflow velocity vout = 0.104 ± 0.006c. Interestingly, the parameters of the photoionized emission model remarkably match those of the absorbing UFO, supporting the possibility that the same material could be responsible for both emission and absorption. We suggest an outburst scenario in which an accretion disc wind, initially lying out of the line of sight and observed in emission, then crosses our view to the source and it is observed in absorption as a mildly relativistic UFO.

The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer: Evidence of High Unbeamed Luminosity in Holmberg II ULX

NASA Technical Reports Server (NTRS)

Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

2008-01-01

We present the first Spitzer Infrared Spectrograph (IRS) observations of the [O IV] 25.89 micron emission line detected from the ultraluminous X-ray source (ULX) in Holmberg II. This line is a well established signature of high excitation, usually associated with AGN. Its detection suggests that the ULX has a strong impact on the surrounding gas. A Spitzer high resolution spectral map shows that the [O IV] is coincident with the X-ray position of the Holmberg II ULX. We find that the luminosity and the morphology of the line emission is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is radiation bounded both in the line of sight direction and to the west, and probably matter bounded to the east. Evidence for a massive black hole (BH) in this ULX is mounting. Detailed photoionization models favor an intermediate mass black hole of at least 85 Solar Mass as the ionization source for the [OIV] emission. We find that the spectral type of the companion star strongly affects the expected strength of the [O IV] emission. This finding could explain the origin of [O IV] in some starburst galaxies containing black hole binaries.

A quasi-static model of global atmospheric electricity. I - The lower atmosphere

NASA Technical Reports Server (NTRS)

Hays, P. B.; Roble, R. G.

1979-01-01

A quasi-steady model of global lower atmospheric electricity is presented. The model considers thunderstorms as dipole electric generators that can be randomly distributed in various regions and that are the only source of atmospheric electricity and includes the effects of orography and electrical coupling along geomagnetic field lines in the ionosphere and magnetosphere. The model is used to calculate the global distribution of electric potential and current for model conductivities and assumed spatial distributions of thunderstorms. Results indicate that large positive electric potentials are generated over thunderstorms and penetrate to ionospheric heights and into the conjugate hemisphere along magnetic field lines. The perturbation of the calculated electric potential and current distributions during solar flares and subsequent Forbush decreases is discussed, and future measurements of atmospheric electrical parameters and modifications of the model which would improve the agreement between calculations and measurements are suggested.

Effect of duct shape, Mach number, and lining construction on measured suppressor attenuation and comparison with theory

NASA Technical Reports Server (NTRS)

Olsen, W. A.; Krejsa, E. A.; Coats, J. W.

1972-01-01

Noise attenuation was measured for several types of cylindrical suppressors that use a duct lining composed of honeycomb cells covered with a perforated plate. The experimental technique used gave attenuation data that were repeatable and free of noise floors and other sources of error. The suppressor length, the effective acoustic diameter, suppressor shape and flow velocity were varied. The agreement among the attenuation data and two widely used analytical models was generally satisfactory. Changes were also made in the construction of the acoustic lining to measure their effect on attenuation. One of these produced a very broadband muffler.

Mass Loss from the Nuclei of Active Galaxies

NASA Technical Reports Server (NTRS)

Crenshaw, Michael; Kraemer, Steven B.; George, Ian M.

2003-01-01

Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The intrinsic UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show variable ionic column densities which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight . Detailed studies of the intrinsic absorbers. with the assistance of monitoring observations and photoionization models. provide constraints on their kinematics] physical conditions. and locations relative to the central continuum source. which range from the inner nucleus (approx.0.01 pc) to the galactic disk or halo (approx.10 kpc) . Dynamical models that make use of thermal winds. radiation pressure. and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints .

pyLIMA : The first open source microlensing modeling software

NASA Astrophysics Data System (ADS)

Bachelet, Etienne; Street, Rachel; Bozza, Valerio

2018-01-01

Microlensing is highly sensitive to planets beyond the snowline and distributed along the line of sight towards the Galactic Bulge. The WFIRST-AFTA mission should detect about 3000 of these planets and significantly improves our knowledge of planet formation and statistics, complementing results found by transit and radial velocity methods. However, the modeling of microlensing event is challenging on different aspects leading to a highly time consuming analysis. After a quick summarize of these different challenges, I will present pyLIMA, the first open source microlensing modeling software. The aimed goal of this software are to be flexible, powerful and user friendly. This presentation will focus on various case and early results.

Experimental study on distributed optical fiber-based approach monitoring saturation line in levee engineering

NASA Astrophysics Data System (ADS)

Su, Huaizhi; Li, Hao; Kang, Yeyuan; Wen, Zhiping

2018-02-01

Seepage is one of key factors which affect the levee engineering safety. The seepage danger without timely detection and rapid response may likely lead to severe accidents such as seepage failure, slope instability, and even levee break. More than 90 percent of levee break events are caused by the seepage. It is very important for seepage behavior identification to determine accurately saturation line in levee engineering. Furthermore, the location of saturation line has a major impact on slope stability in levee engineering. Considering the structure characteristics and service condition of levee engineering, the distributed optical fiber sensing technology is introduced to implement the real-time observation of saturation line in levee engineering. The distributed optical fiber temperature sensor system (DTS)-based monitoring principle of saturation line in levee engineering is investigated. An experimental platform, which consists of DTS, heating system, water-supply system, auxiliary analysis system and levee model, is designed and constructed. The monitoring experiment of saturation line in levee model is implemented on this platform. According to the experimental results, the numerical relationship between moisture content and thermal conductivity in porous medium is identified. A line heat source-based distributed optical fiber method obtaining the thermal conductivity in porous medium is developed. A DTS-based approach is proposed to monitor the saturation line in levee engineering. The embedment pattern of optical fiber for monitoring saturation line is presented.

Imaging Faults in Carbonate Reservoir using Full Waveform Inversion and Reverse Time Migration of Walkaway VSP Data

NASA Astrophysics Data System (ADS)

Takam Takougang, E. M.; Bouzidi, Y.

2016-12-01

Multi-offset Vertical Seismic Profile (walkaway VSP) data were collected in an oil field located in a shallow water environment dominated by carbonate rocks, offshore the United Arab Emirates. The purpose of the survey was to provide structural information of the reservoir, around and away from the borehole. Five parallel lines were collected using an air gun at 25 m shot interval and 4 m source depth. A typical recording tool with 20 receivers spaced every 15.1 m, and located in a deviated borehole with an angle varying between 0 and 24 degree from the vertical direction, was used to record the data. The recording tool was deployed at different depths for each line, from 521 m to 2742 m depth. Smaller offsets were used for shallow receivers and larger offsets for deeper receivers. The lines merged to form the input dataset for waveform tomography. The total length of the combined lines was 9 km, containing 1344 shots and 100 receivers in the borehole located half-way down. Acoustic full waveform inversion was applied in the frequency domain to derive a high resolution velocity model. The final velocity model derived after the inversion using the frequencies 5-40 Hz, showed good correlation with velocities estimated from vertical incidence VSP and sonic log, confirming the success of the inversion. The velocity model showed anomalous low values in areas that correlate with known location of hydrocarbon reservoir. Pre-stack depth Reverse time migration was then applied using the final velocity model from waveform inversion and the up-going wavefield from the input data. The final estimated source signature from waveform inversion was used as input source for reverse time migration. To save computational memory and time, every 3 shots were used during reverse time migration and the data were low-pass filtered to 30 Hz. Migration artifacts were attenuated using a second order derivative filter. The final migration image shows a good correlation with the waveform tomography velocity model, and highlights a complex network of faults in the reservoir, that could be useful in understanding fluid and hydrocarbon movements. This study shows that the combination of full waveform tomography and reverse time migration can provide high resolution images that can enhance interpretation and characterization of oil reservoirs.

LSDCat: Detection and cataloguing of emission-line sources in integral-field spectroscopy datacubes

NASA Astrophysics Data System (ADS)

Herenz, Edmund Christian; Wisotzki, Lutz

2017-06-01

We present a robust, efficient, and user-friendly algorithm for detecting faint emission-line sources in large integral-field spectroscopic datacubes together with the public release of the software package Line Source Detection and Cataloguing (LSDCat). LSDCat uses a three-dimensional matched filter approach, combined with thresholding in signal-to-noise, to build a catalogue of individual line detections. In a second pass, the detected lines are grouped into distinct objects, and positions, spatial extents, and fluxes of the detected lines are determined. LSDCat requires only a small number of input parameters, and we provide guidelines for choosing appropriate values. The software is coded in Python and capable of processing very large datacubes in a short time. We verify the implementation with a source insertion and recovery experiment utilising a real datacube taken with the MUSE instrument at the ESO Very Large Telescope. The LSDCat software is available for download at http://muse-vlt.eu/science/tools and via the Astrophysics Source Code Library at http://ascl.net/1612.002

Source Distributions of Substorm Ions Observed in the Near-Earth Magnetotail

NASA Technical Reports Server (NTRS)

Ashour-Abdalla, M.; El-Alaoui, M.; Peroomian, V.; Walker, R. J.; Raeder, J.; Frank, L. A.; Paterson, W. R.

1999-01-01

This study employs Geotail plasma observations and numerical modeling to determine sources of the ions observed in the near-Earth magnetotail near midnight during a substorm. The growth phase has the low-latitude boundary layer as its most important source of ions at Geotail, but during the expansion phase the plasma mantle is dominant. The mantle distribution shows evidence of two distinct entry mechanisms: entry through a high latitude reconnection region resulting in an accelerated component, and entry through open field lines traditionally identified with the mantle source. The two entry mechanisms are separated in time, with the high-latitude reconnection region disappearing prior to substorm onset.

The energetic ion signature of an O-type neutral line in the geomagnetic tail

NASA Technical Reports Server (NTRS)

Martin, R. F., Jr.; Johnson, D. F.; Speiser, T. W.

1991-01-01

An energetic ion signature is presented which has the potential for remote sensing of an O-type neutral line embedded in a current sheet. A source plasma with a tailward flowing Kappa distribution yields a strongly non-Kappa distribution after interacting with the neutral line: sharp jumps, or ridges, occur in the velocity space distribution function f(nu-perpendicular, nu-parallel) associated with both increases and decreases in f. The jumps occur when orbits are reversed in the x-direction: a reversal causing initially earthward particles (low probability in the source distribution) to be observed results in a decrease in f, while a reversal causing initially tailward particles to be observed produces an increase in f. The reversals, and hence the jumps, occur at approximately constant values of perpendicular velocity in both the positive nu parallel and negative nu parallel half planes. The results were obtained using single particle simulations in a fixed magnetic field model.

Tracking the complex absorption in NGC 2110 with two Suzaku observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard

2014-05-10

We present spectral analysis of two Suzaku observations of the Seyfert 2 galaxy, NGC 2110. This source has been known to show complex, variable absorption which we study in depth by analyzing these two observations set 7 yr apart and by comparing them to previously analyzed observations with the XMM-Newton and Chandra observatories. We find that there is a relatively stable, full-covering absorber with a column density of ∼3× 10{sup 22} cm{sup –2}, with an additional patchy absorber that is likely variable in both column density and covering fraction over timescales of years, consistent with clouds in a patchy torusmore » or in the broad line region. We model a soft emission line complex, likely arising from ionized plasma and consistent with previous studies. We find no evidence for reflection from an accretion disk in this source with contribution from neither relativistically broadened Fe Kα line emission, nor from a Compton reflection hump.« less

Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

NASA Astrophysics Data System (ADS)

Sanders, Ryan L.; Shapley, Alice E.; Zhang, Kai; Yan, Renbin

2017-12-01

Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of H II and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for H II regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the H II region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single H II regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.

SDSS-IV MaNGA: the impact of diffuse ionized gas on emission-line ratios, interpretation of diagnostic diagrams and gas metallicity measurements

NASA Astrophysics Data System (ADS)

Zhang, Kai; Yan, Renbin; Bundy, Kevin; Bershady, Matthew; Haffner, L. Matthew; Walterbos, René; Maiolino, Roberto; Tremonti, Christy; Thomas, Daniel; Drory, Niv; Jones, Amy; Belfiore, Francesco; Sánchez, Sebastian F.; Diamond-Stanic, Aleksandar M.; Bizyaev, Dmitry; Nitschelm, Christian; Andrews, Brett; Brinkmann, Jon; Brownstein, Joel R.; Cheung, Edmond; Li, Cheng; Law, David R.; Roman Lopes, Alexandre; Oravetz, Daniel; Pan, Kaike; Storchi Bergmann, Thaisa; Simmons, Audrey

2017-04-01

Diffuse ionized gas (DIG) is prevalent in star-forming galaxies. Using a sample of 365 nearly face-on star-forming galaxies observed by Mapping Nearby Galaxies at APO, we demonstrate how DIG in star-forming galaxies impacts the measurements of emission-line ratios, hence the interpretation of diagnostic diagrams and gas-phase metallicity measurements. At fixed metallicity, DIG-dominated low ΣHα regions display enhanced [S II]/Hα, [N II]/Hα, [O II]/Hβ and [O I]/Hα. The gradients in these line ratios are determined by metallicity gradients and ΣHα. In line ratio diagnostic diagrams, contamination by DIG moves H II regions towards composite or low-ionization nuclear emission-line region (LI(N)ER)-like regions. A harder ionizing spectrum is needed to explain DIG line ratios. Leaky H II region models can only shift line ratios slightly relative to H II region models, and thus fail to explain the composite/LI(N)ER line ratios displayed by DIG. Our result favours ionization by evolved stars as a major ionization source for DIG with LI(N)ER-like emission. DIG can significantly bias the measurement of gas metallicity and metallicity gradients derived using strong-line methods. Metallicities derived using N2O2 are optimal because they exhibit the smallest bias and error. Using O3N2, R23, N2 = [N II]/Hα and N2S2Hα to derive metallicities introduces bias in the derived metallicity gradients as large as the gradient itself. The strong-line method of Blanc et al. (IZI hereafter) cannot be applied to DIG to get an accurate metallicity because it currently contains only H II region models that fail to describe the DIG.

On the properties of dust and gas in the environs of V838 Monocerotis

NASA Astrophysics Data System (ADS)

Exter, K. M.; Cox, N. L. J.; Swinyard, B. M.; Matsuura, M.; Mayer, A.; De Beck, E.; Decin, L.

2016-12-01

Aims: We aim to probe the close and distant circumstellar environments of the stellar outburst object V838 Mon. Methods: Herschel far-infrared imaging and spectroscopy were taken at several epochs to probe the central point source and the extended environment of V838 Mon. PACS and SPIRE maps were used to obtain photometry of the dust immediately around V838 Mon, and in the surrounding infrared-bright region. These maps were fitted in 1d and 2d to measure the temperature, mass, and β of the two dust sources. PACS and SPIRE spectra were used to detect emission lines from the extended atmosphere of the star, which were then modelled to study the physical conditions in the emitting material. HIFI spectra were taken to measure the kinematics of the extended atmosphere but unfortunately yielded no detections. Results: Fitting of the far-infrared imaging of V838 Mon reveals 0.5-0.6 M⊙ of ≈19 K dust in the environs (≈2.7 pc) surrounding V838 Mon. The surface-integrated infrared flux (signifying the thermal light echo), and derived dust properties do not vary significantly between the different epochs. We measured the photometry of the point source. As the peak of the SED (Spectral Energy Distribution) lies outside the Herschel spectral range, it is only by incorporating data from other observatories and previous epochs that we can usefully fit the SED; with this we explicitly assume no evolution of the point source between the epochs. We find that warm dust with a temperature 300 K distributed over a radius of 150-200 AU. We fit the far-infrared lines of CO arising from the point source, from an extended environment around V838 Mon. Assuming a model of a spherical shell for this gas, we find that the CO appears to arise from two temperature zones: a cold zone (Tkin ≈ 18 K) that could be associated with the ISM or possibly with a cold layer in the outermost part of the shell, and a warm (Tkin ≈ 400 K) zone that is associated with the extended environment of V838 Mon within a region of radius of ≈210 AU. The SiO lines arise from a warm/hot zone. We did not fit the lines of H2O as they are far more dependent on the model assumed. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, Anca; Castillo, Christopher A.; Shields, Joseph C.

Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which transition objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at ≲10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in themore » line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The transition objects show a threefold increase in the incidence of broad Hα emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z ≈ 0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude.« less

Preliminary Results of the first European Source Apportionment intercomparison for Receptor and Chemical Transport Models

NASA Astrophysics Data System (ADS)

Belis, Claudio A.; Pernigotti, Denise; Pirovano, Guido

2017-04-01

Source Apportionment (SA) is the identification of ambient air pollution sources and the quantification of their contribution to pollution levels. This task can be accomplished using different approaches: chemical transport models and receptor models. Receptor models are derived from measurements and therefore are considered as a reference for primary sources urban background levels. Chemical transport model have better estimation of the secondary pollutants (inorganic) and are capable to provide gridded results with high time resolution. Assessing the performance of SA model results is essential to guarantee reliable information on source contributions to be used for the reporting to the Commission and in the development of pollution abatement strategies. This is the first intercomparison ever designed to test both receptor oriented models (or receptor models) and chemical transport models (or source oriented models) using a comprehensive method based on model quality indicators and pre-established criteria. The target pollutant of this exercise, organised in the frame of FAIRMODE WG 3, is PM10. Both receptor models and chemical transport models present good performances when evaluated against their respective references. Both types of models demonstrate quite satisfactory capabilities to estimate the yearly source contributions while the estimation of the source contributions at the daily level (time series) is more critical. Chemical transport models showed a tendency to underestimate the contribution of some single sources when compared to receptor models. For receptor models the most critical source category is industry. This is probably due to the variety of single sources with different characteristics that belong to this category. Dust is the most problematic source for Chemical Transport Models, likely due to the poor information about this kind of source in the emission inventories, particularly concerning road dust re-suspension, and consequently the little detail about the chemical components of this source used in the models. The sensitivity tests show that chemical transport models show better performances when displaying a detailed set of sources (14) than when using a simplified one (only 8). It was also observed that an enhanced vertical profiling can improve the estimation of specific sources, such as industry, under complex meteorological conditions and that an insufficient spatial resolution in urban areas can impact on the capabilities of models to estimate the contribution of diffuse primary sources (e.g. traffic). Both families of models identify traffic and biomass burning as the first and second most contributing categories, respectively, to elemental carbon. The results of this study demonstrate that the source apportionment assessment methodology developed by the JRC is applicable to any kind of SA model. The same methodology is implemented in the on-line DeltaSA tool to support source apportionment model evaluation (http://source-apportionment.jrc.ec.europa.eu/).

Selection of Phage Display Peptides Targeting Human Pluripotent Stem Cell-Derived Progenitor Cell Lines.

PubMed

Bignone, Paola A; Krupa, Rachel A; West, Michael D; Larocca, David

2016-01-01

The ability of human pluripotent stem cells (hPS) to both self-renew and differentiate into virtually any cell type makes them a promising source of cells for cell-based regenerative therapies. However, stem cell identity, purity, and scalability remain formidable challenges that need to be overcome for translation of pluripotent stem cell research into clinical applications. Directed differentiation from hPS cells is inefficient and residual contamination with pluripotent cells that have the potential to form tumors remains problematic. The derivation of scalable (self-renewing) embryonic progenitor stem cell lines offers a solution because they are well defined and clonally pure. Clonally pure progenitor stem cell lines also provide a means for identifying cell surface targeting reagents that are useful for identification, tracking, and repeated derivation of the corresponding progenitor stem cell types from additional hPS cell sources. Such stem cell targeting reagents can then be applied to the manufacture of genetically diverse banks of human embryonic progenitor cell lines for drug screening, disease modeling, and cell therapy. Here we present methods to identify human embryonic progenitor stem cell targeting peptides by selection of phage display libraries on clonal embryonic progenitor cell lines and demonstrate their use for targeting quantum dots (Qdots) for stem cell labeling.

Optimal pupil design for confocal microscopy

NASA Astrophysics Data System (ADS)

Patel, Yogesh G.; Rajadhyaksha, Milind; DiMarzio, Charles A.

2010-02-01

Confocal reflectance microscopy may enable screening and diagnosis of skin cancers noninvasively and in real-time, as an adjunct to biopsy and pathology. Current instruments are large, complex, and expensive. A simpler, confocal line-scanning microscope may accelerate the translation of confocal microscopy in clinical and surgical dermatology. A confocal reflectance microscope may use a beamsplitter, transmitting and detecting through the pupil, or a divided pupil, or theta configuration, with half used for transmission and half for detection. The divided pupil may offer better sectioning and contrast. We present a Fourier optics model and compare the on-axis irradiance of a confocal point-scanning microscope in both pupil configurations, optimizing the profile of a Gaussian beam in a circular or semicircular aperture. We repeat both calculations with a cylindrical lens which focuses the source to a line. The variable parameter is the fillfactor, h, the ratio of the 1/e2 diameter of the Gaussian beam to the diameter of the full aperture. The optimal values of h, for point scanning are 0.90 (full) and 0.66 for the half-aperture. For line-scanning, the fill-factors are 1.02 (full) and 0.52 (half). Additional parameters to consider are the optimal location of the point-source beam in the divided-pupil configuration, the optimal line width for the line-source, and the width of the aperture in the divided-pupil configuration. Additional figures of merit are field-of-view and sectioning. Use of optimal designs is critical in comparing the experimental performance of the different configurations.

SELFI: an object-based, Bayesian method for faint emission line source detection in MUSE deep field data cubes

NASA Astrophysics Data System (ADS)

Meillier, Céline; Chatelain, Florent; Michel, Olivier; Bacon, Roland; Piqueras, Laure; Bacher, Raphael; Ayasso, Hacheme

2016-04-01

We present SELFI, the Source Emission Line FInder, a new Bayesian method optimized for detection of faint galaxies in Multi Unit Spectroscopic Explorer (MUSE) deep fields. MUSE is the new panoramic integral field spectrograph at the Very Large Telescope (VLT) that has unique capabilities for spectroscopic investigation of the deep sky. It has provided data cubes with 324 million voxels over a single 1 arcmin2 field of view. To address the challenge of faint-galaxy detection in these large data cubes, we developed a new method that processes 3D data either for modeling or for estimation and extraction of source configurations. This object-based approach yields a natural sparse representation of the sources in massive data fields, such as MUSE data cubes. In the Bayesian framework, the parameters that describe the observed sources are considered random variables. The Bayesian model leads to a general and robust algorithm where the parameters are estimated in a fully data-driven way. This detection algorithm was applied to the MUSE observation of Hubble Deep Field-South. With 27 h total integration time, these observations provide a catalog of 189 sources of various categories and with secured redshift. The algorithm retrieved 91% of the galaxies with only 9% false detection. This method also allowed the discovery of three new Lyα emitters and one [OII] emitter, all without any Hubble Space Telescope counterpart. We analyzed the reasons for failure for some targets, and found that the most important limitation of the method is when faint sources are located in the vicinity of bright spatially resolved galaxies that cannot be approximated by the Sérsic elliptical profile. The software and its documentation are available on the MUSE science web service (muse-vlt.eu/science).

Solar Flare Termination Shock and Synthetic Emission Line Profiles of the Fe xxi 1354.08 Å Line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Lijia; Li, Gang; Reeves, Kathy

Solar flares are among the most energetic phenomena that occur in the solar system. In the standard solar flare model, a fast mode shock, often referred to as the flare termination shock (TS), can exist above the loop-top source of hard X-ray emissions. The existence of the TS has been recently related to spectral hardening of a flare’s hard X-ray spectra at energies >300 keV. Observations of the Fe xxi 1354.08 Å line during solar flares by the Interface Region Imaging Spectrograph ( IRIS ) spacecraft have found significant redshifts with >100 km s{sup −1}, which is consistent with amore » reconnection downflow. The ability to detect such a redshift with IRIS suggests that one may be able to use IRIS observations to identify flare TSs. Using a magnetohydrodynamic simulation to model magnetic reconnection of a solar flare and assuming the existence of a TS in the downflow of the reconnection plasma, we model the synthetic emission of the Fe xxi 1354.08 line in this work. We show that the existence of the TS in the solar flare may manifest itself in the Fe xxi 1354.08 Å line.« less

Photoionisation modelling of the broad line region

NASA Astrophysics Data System (ADS)

King, Anthea

2016-08-01

Two of the most fundamental questions regarding the broad line region (BLR) are "what is its structure?" and "how is it moving?" Baldwin et al. (1995) showed that by summing over an ensemble of clouds at differing densities and distances from the ionising source we can easily and naturally produce a spectrum similar to what is observed for AGN. This approach is called the `locally optimally emitting clouds' (LOC) model. This approach can also explain the well-observed stratification of emission lines in the BLR (e.g. Clavel et al. 1991, Peterson et al. 1991, Kollatschny et al. 2001) and `breathing' of BLR with changes in the continuum luminosity (Netzer & Mor 1990, Peterson et al. 2014) and is therefore a generally accepted model of the BLR. However, LOC predictions require some assumptions to be made about the distribution of the clouds within the BLR. By comparing photoionization predictions, for a distribution of cloud properties, with observed spectra we can infer something about the structure of the BLR and distribution of clouds. I use existing reverberation mapping data to constrain the structure of the BLR by observing how individual line strengths and ratios of different lines change in high and low luminosity states. I will present my initial constraints and discuss the challenges associated with the method.

A two-dimensional analytical model of vapor intrusion involving vertical heterogeneity.

PubMed

Yao, Yijun; Verginelli, Iason; Suuberg, Eric M

2017-05-01

In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz-Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.

An analysis of lamp irradiation in ellipsoidal mirror furnaces

NASA Astrophysics Data System (ADS)

Rivas, Damián; Vázquez-Espí, Carlos

2001-03-01

The irradiation generated by halogen lamps in ellipsoidal mirror furnaces is analyzed, in configurations suited to the study of the floating-zone technique for crystal growth in microgravity conditions. A line-source model for the lamp (instead of a point source) is developed, so that the longitudinal extent of the filament is taken into account. With this model the case of defocussed lamps can be handle analytically. In the model the lamp is formed by an aggregate of point-source elements, placed along the axis of the ellipsoid. For these point sources (which, in general, are defocussed) an irradiation model is formulated, within the approximation of geometrical optics. The irradiation profiles obtained (both on the lateral surface and on the inner base of the cylindrical sample) are analyzed. They present singularities related to the caustics formed by the family of reflected rays; these caustics are also analyzed. The lamp model is combined with a conduction-radiation model to study the temperature field in the sample. The effects of defocussing the lamp (common practice in crystal growth) are studied; advantages and also some drawbacks are pointed out. Comparison with experimental results is made.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, Leon H.; Hance, Richard D.; Kristalinski, Alexandr L.; Visser, Age T.

1996-01-01

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

1996-11-19

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

Economic evaluation in chronic pain: a systematic review and de novo flexible economic model.

PubMed

Sullivan, W; Hirst, M; Beard, S; Gladwell, D; Fagnani, F; López Bastida, J; Phillips, C; Dunlop, W C N

2016-07-01

There is unmet need in patients suffering from chronic pain, yet innovation may be impeded by the difficulty of justifying economic value in a field beset by data limitations and methodological variability. A systematic review was conducted to identify and summarise the key areas of variability and limitations in modelling approaches in the economic evaluation of treatments for chronic pain. The results of the literature review were then used to support the development of a fully flexible open-source economic model structure, designed to test structural and data assumptions and act as a reference for future modelling practice. The key model design themes identified from the systematic review included: time horizon; titration and stabilisation; number of treatment lines; choice/ordering of treatment; and the impact of parameter uncertainty (given reliance on expert opinion). Exploratory analyses using the model to compare a hypothetical novel therapy versus morphine as first-line treatments showed cost-effectiveness results to be sensitive to structural and data assumptions. Assumptions about the treatment pathway and choice of time horizon were key model drivers. Our results suggest structural model design and data assumptions may have driven previous cost-effectiveness results and ultimately decisions based on economic value. We therefore conclude that it is vital that future economic models in chronic pain are designed to be fully transparent and hope our open-source code is useful in order to aspire to a common approach to modelling pain that includes robust sensitivity analyses to test structural and parameter uncertainty.

Modeling of Aerosols in Post-Combustor Flow Path and Sampling System

NASA Technical Reports Server (NTRS)

Wey, Thomas; Liu, Nan-Suey

2006-01-01

The development and application of a multi-dimensional capability for modeling and simulation of aviation-sourced particle emissions and their precursors are elucidated. Current focus is on the role of the flow and thermal environments. The cases investigated include a film cooled turbine blade, the first-stage of a high-pressure turbine, the sampling probes, the sampling lines, and a pressure reduction chamber.

Digital Bedrock Compilation: A Geodatabase Covering Forest Service Lands in California

NASA Astrophysics Data System (ADS)

Elder, D.; de La Fuente, J. A.; Reichert, M.

2010-12-01

This digital database contains bedrock geologic mapping for Forest Service lands within California. This compilation began in 2004 and the first version was completed in 2005. Second publication of this geodatabase was completed in 2010 and filled major gaps in the southern Sierra Nevada and Modoc/Medicine Lake/Warner Mountains areas. This digital map database was compiled from previously published and unpublished geologic mapping, with source mapping and review from California Geological Survey, the U.S. Geological Survey and others. Much of the source data was itself compilation mapping. This geodatabase is huge, containing ~107,000 polygons and ~ 280,000 arcs. Mapping was compiled from more than one thousand individual sources and covers over 41,000,000 acres (~166,000 km2). It was compiled from source maps at various scales - from ~ 1:4,000 to 1:250,000 and represents the best available geologic mapping at largest scale possible. An estimated 70-80% of the source information was digitized from geologic mapping at 1:62,500 scale or better. Forest Service ACT2 Enterprise Team compiled the bedrock mapping and developed a geodatabase to store this information. This geodatabase supports feature classes for polygons (e.g, map units), lines (e.g., contacts, boundaries, faults and structural lines) and points (e.g., orientation data, structural symbology). Lookup tables provide detailed information for feature class items. Lookup/type tables contain legal values and hierarchical groupings for geologic ages and lithologies. Type tables link coded values with descriptions for line and point attributes, such as line type, line location and point type. This digital mapping is at the core of many quantitative analyses and derivative map products. Queries of the database are used to produce maps and to quantify rock types of interest. These include the following: (1) ultramafic rocks - where hazards from naturally occurring asbestos are high, (2) granitic rocks - increased erosion hazards, (3) limestone, chert, sedimentary rocks - paleontological resources (Potential Fossil Yield Classification maps), (4) calcareous rocks (cave resources, water chemistry), and (5) lava flows - lava tubes (more caves). Map unit groupings (e.g., belts, terranes, tectonic & geomorphic provinces) can also be derived from the geodatabase. Digital geologic mapping was used in ground water modeling to predict effects of tunneling through the San Bernardino Mountains. Bedrock mapping is used in models that characterize watershed sediment regimes and quantify anthropogenic influences. When combined with digital geomorphology mapping, this geodatabase helps to assess landslide hazards.

Diagnostics of the solar corona from comparison between Faraday rotation measurements and magnetohydrodynamic simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Chat, G.; Cohen, O.; Kasper, J. C.

Polarized natural radio sources passing behind the Sun experience Faraday rotation as a consequence of the electron density and magnetic field strength in coronal plasma. Since Faraday rotation is proportional to the product of the density and the component of the magnetic field along the line of sight of the observer, a model is required to interpret the observations and infer coronal structures. Faraday rotation observations have been compared with relatively ad hoc models of the corona. Here for the first time we compare these observations with magnetohydrodynamic (MHD) models of the solar corona driven by measurements of the photosphericmore » magnetic field. We use observations made with the NRAO Very Large Array of 34 polarized radio sources occulted by the solar corona between 5 and 14 solar radii. The measurements were made during 1997 May, and 2005 March and April. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona. We find that (1) using a synoptic map of the solar magnetic field just one Carrington rotation off produces poorer agreements, meaning that the outer corona changes in the course of one month, even in solar minimum; (2) global MHD models of the solar corona driven by photospheric magnetic field measurements are generally able to reproduce Faraday rotation observations; and (3) some sources show significant disagreement between the model and the observations, which appears to be a function of the proximity of the line of sight to the large-scale heliospheric current sheet.« less

Simulation gravity modeling to spacecraft-tracking data - Analysis and application

NASA Technical Reports Server (NTRS)

Phillips, R. J.; Sjogren, W. L.; Abbott, E. A.; Zisk, S. H.

1978-01-01

It is proposed that line-of-sight gravity measurements derived from spacecraft-tracking data can be used for quantitative subsurface density modeling by suitable orbit simulation procedures. Such an approach avoids complex dynamic reductions and is analogous to the modeling of conventional surface gravity data. This procedure utilizes the vector calculations of a given gravity model in a simplified trajectory integration program that simulates the line-of-sight gravity. Solutions from an orbit simulation inversion and a dynamic inversion on Doppler observables compare well (within 1% in mass and size), and the error sources in the simulation approximation are shown to be quite small. An application of this technique is made to lunar crater gravity anomalies by simulating the complete Bouguer correction to several large young lunar craters. It is shown that the craters all have negative Bouguer anomalies.

LIQUID: an-open source software for identifying lipids in LC-MS/MS-based lipidomics data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyle, Jennifer E.; Crowell, Kevin L.; Casey, Cameron P.

2017-01-31

We introduce an open-source software, LIQUID, for semi-automated processing and visualization of LC-MS/MS based lipidomics data. LIQUID provides users with the capability to process high throughput data and contains a customizable target library and scoring model per project needs. The graphical user interface provides visualization of multiple lines of spectral evidence for each lipid identification, allowing rapid examination of data for making confident identifications of lipid molecular species.

A new debris sensor based on dual excitation sources for online debris monitoring

NASA Astrophysics Data System (ADS)

Hong, Wei; Wang, Shaoping; Tomovic, Mileta M.; Liu, Haokuo; Wang, Xingjian

2015-09-01

Mechanical systems could be severely damaged by loose debris generated through wear processes between contact surfaces. Hence, debris detection is necessary for effective fault diagnosis, life prediction, and prevention of catastrophic failures. This paper presents a new in-line debris sensor for hydraulic systems based on dual excitation sources. The proposed sensor makes magnetic lines more concentrated while at the same time improving magnetic field uniformity. As a result the sensor has higher sensitivity and improved precision. This paper develops the sensor model, discusses sensor structural features, and introduces a measurement method for debris size identification. Finally, experimental verification is presented indicating that that the sensor can effectively detect 81 μm (cube) or larger particles in 12 mm outside diameter (OD) organic glass pipe.

Estimating oxygen distribution from vasculature in three-dimensional tumour tissue

PubMed Central

Kannan, Pavitra; Warren, Daniel R.; Markelc, Bostjan; Bates, Russell; Muschel, Ruth; Partridge, Mike

2016-01-01

Regions of tissue which are well oxygenated respond better to radiotherapy than hypoxic regions by up to a factor of three. If these volumes could be accurately estimated, then it might be possible to selectively boost dose to radio-resistant regions, a concept known as dose-painting. While imaging modalities such as 18F-fluoromisonidazole positron emission tomography (PET) allow identification of hypoxic regions, they are intrinsically limited by the physics of such systems to the millimetre domain, whereas tumour oxygenation is known to vary over a micrometre scale. Mathematical modelling of microscopic tumour oxygen distribution therefore has the potential to complement and enhance macroscopic information derived from PET. In this work, we develop a general method of estimating oxygen distribution in three dimensions from a source vessel map. The method is applied analytically to line sources and quasi-linear idealized line source maps, and also applied to full three-dimensional vessel distributions through a kernel method and compared with oxygen distribution in tumour sections. The model outlined is flexible and stable, and can readily be applied to estimating likely microscopic oxygen distribution from any source geometry. We also investigate the problem of reconstructing three-dimensional oxygen maps from histological and confocal two-dimensional sections, concluding that two-dimensional histological sections are generally inadequate representations of the three-dimensional oxygen distribution. PMID:26935806

Estimating oxygen distribution from vasculature in three-dimensional tumour tissue.

PubMed

Grimes, David Robert; Kannan, Pavitra; Warren, Daniel R; Markelc, Bostjan; Bates, Russell; Muschel, Ruth; Partridge, Mike

2016-03-01

Regions of tissue which are well oxygenated respond better to radiotherapy than hypoxic regions by up to a factor of three. If these volumes could be accurately estimated, then it might be possible to selectively boost dose to radio-resistant regions, a concept known as dose-painting. While imaging modalities such as 18F-fluoromisonidazole positron emission tomography (PET) allow identification of hypoxic regions, they are intrinsically limited by the physics of such systems to the millimetre domain, whereas tumour oxygenation is known to vary over a micrometre scale. Mathematical modelling of microscopic tumour oxygen distribution therefore has the potential to complement and enhance macroscopic information derived from PET. In this work, we develop a general method of estimating oxygen distribution in three dimensions from a source vessel map. The method is applied analytically to line sources and quasi-linear idealized line source maps, and also applied to full three-dimensional vessel distributions through a kernel method and compared with oxygen distribution in tumour sections. The model outlined is flexible and stable, and can readily be applied to estimating likely microscopic oxygen distribution from any source geometry. We also investigate the problem of reconstructing three-dimensional oxygen maps from histological and confocal two-dimensional sections, concluding that two-dimensional histological sections are generally inadequate representations of the three-dimensional oxygen distribution. © 2016 The Authors.

Numerical model a graphene component for the sensing of weak electromagnetic signals

NASA Astrophysics Data System (ADS)

Nasswettrova, A.; Fiala, P.; Nešpor, D.; Drexler, P.; Steinbauer, M.

2015-05-01

The paper discusses a numerical model and provides an analysis of a graphene coaxial line suitable for sub-micron sensors of magnetic fields. In relation to the presented concept, the target areas and disciplines include biology, medicine, prosthetics, and microscopic solutions for modern actuators or SMART elements. The proposed numerical model is based on an analysis of a periodic structure with high repeatability, and it exploits a graphene polymer having a basic dimension in nanometers. The model simulates the actual random motion in the structure as the source of spurious signals and considers the pulse propagation along the structure; furthermore, the model also examines whether and how the pulse will be distorted at the beginning of the line, given the various ending versions. The results of the analysis are necessary for further use of the designed sensing devices based on graphene structures.

Evidence for a temperature rise in the outer layers of alpha Lyrae, from Copernicus observations of Lyman-alpha

NASA Technical Reports Server (NTRS)

Praderie, F.; Simonneau, E.; Snow, T. P., Jr.

1975-01-01

Copernicus satellite observations of the Ly-alpha profiles in alpha Lyrae (Vega) are used to determine whether classical radiative-equilibrium LTE model atmospheres can fit the thermal structure in the outer layers of that star. Two plane-parallel LTE model photospheres of alpha Lyrae are considered: a line-blanketed radiative-equilibrium model with an effective temperature of 9650 K and log g of 4.05, and the same model with a temperature of 9500 K and log g of 4.0. The profiles of the Ly-alpha wings are computed, and it is found that classical LTE models are unable to predict either the observed violet wing or the red wing longwards of 1239 A, regardless of the line source function. It is concluded that the electron temperature must increase outwards over the surface value reached in radiative equilibrium.

Coronal Magnetism and Forward Solarsoft Idl Package

NASA Astrophysics Data System (ADS)

Gibson, S. E.

2014-12-01

The FORWARD suite of Solar Soft IDL codes is a community resource for model-data comparison, with a particular emphasis on analyzing coronal magnetic fields. FORWARD may be used both to synthesize a broad range of coronal observables, and to access and compare to existing data. FORWARD works with numerical model datacubes, interfaces with the web-served Predictive Science Inc MAS simulation datacubes and the Solar Soft IDL Potential Field Source Surface (PFSS) package, and also includes several analytic models (more can be added). It connects to the Virtual Solar Observatory and other web-served observations to download data in a format directly comparable to model predictions. It utilizes the CHIANTI database in modeling UV/EUV lines, and links to the CLE polarimetry synthesis code for forbidden coronal lines. FORWARD enables "forward-fitting" of specific observations, and helps to build intuition into how the physical properties of coronal magnetic structures translate to observable properties.

Real-Time Noise Removal for Line-Scanning Hyperspectral Devices Using a Minimum Noise Fraction-Based Approach

PubMed Central

Bjorgan, Asgeir; Randeberg, Lise Lyngsnes

2015-01-01

Processing line-by-line and in real-time can be convenient for some applications of line-scanning hyperspectral imaging technology. Some types of processing, like inverse modeling and spectral analysis, can be sensitive to noise. The MNF (minimum noise fraction) transform provides suitable denoising performance, but requires full image availability for the estimation of image and noise statistics. In this work, a modified algorithm is proposed. Incrementally-updated statistics enables the algorithm to denoise the image line-by-line. The denoising performance has been compared to conventional MNF and found to be equal. With a satisfying denoising performance and real-time implementation, the developed algorithm can denoise line-scanned hyperspectral images in real-time. The elimination of waiting time before denoised data are available is an important step towards real-time visualization of processed hyperspectral data. The source code can be found at http://www.github.com/ntnu-bioopt/mnf. This includes an implementation of conventional MNF denoising. PMID:25654717

High resolution crustal image of South California Continental Borderland: Reverse time imaging including multiples

NASA Astrophysics Data System (ADS)

Bian, A.; Gantela, C.

2014-12-01

Strong multiples were observed in marine seismic data of Los Angeles Regional Seismic Experiment (LARSE).It is crucial to eliminate these multiples in conventional ray-based or one-way wave-equation based depth image methods. As long as multiples contain information of target zone along travelling path, it's possible to use them as signal, to improve the illumination coverage thus enhance the image quality of structural boundaries. Reverse time migration including multiples is a two-way wave-equation based prestack depth image method that uses both primaries and multiples to map structural boundaries. Several factors, including source wavelet, velocity model, back ground noise, data acquisition geometry and preprocessing workflow may influence the quality of image. The source wavelet is estimated from direct arrival of marine seismic data. Migration velocity model is derived from integrated model building workflow, and the sharp velocity interfaces near sea bottom needs to be preserved in order to generate multiples in the forward and backward propagation steps. The strong amplitude, low frequency marine back ground noise needs to be removed before the final imaging process. High resolution reverse time image sections of LARSE Lines 1 and Line 2 show five interfaces: depth of sea-bottom, base of sedimentary basins, top of Catalina Schist, a deep layer and a possible pluton boundary. Catalina Schist shows highs in the San Clemente ridge, Emery Knoll, Catalina Ridge, under Catalina Basin on both the lines, and a minor high under Avalon Knoll. The high of anticlinal fold in Line 1 is under the north edge of Emery Knoll and under the San Clemente fault zone. An area devoid of any reflection features are interpreted as sides of an igneous plume.

Carbon monoxide line emission from photon dominated regions

NASA Astrophysics Data System (ADS)

Koester, B.; Stoerzer, H.; Stutzki, J.; Sternberg, A.

1994-04-01

We present a theoretical study of (12)CO and (13)CO rotational line emission from photon dominated regions (PDRs). We incorporate the effects of clumpy cloud structure by computing the physical structures of plane-parallel photo dominated PDRs with finite thickness which are illuminated by UV-radiation fields from either one or both sides. We examine the influence of the gas density (no (H) = 10 4/cu cm to 107/cu cm), the UV intensity (chi = 103 to 106 times the intensity of the average interstellar UV field), the cloud thickness (measured in units of the visual extinction (AV, 2 less than or = AV less than or = 10) and the Doppler width (1 km/s and 3 km/s) on the emergent CO line center brightness temperatures. We explicitly include the effects of the C-13 chemistry on the line intensities. The high brightness temperatures of the (13)CO J = 6 to 5 line observed in several sources can be explained as originating in high density PDRs (n(H) greater than or = 106/cu cm) which are illuminated from two sides and under the assumption that several PDR clumps lie along the line of sight. To model the observed low-J (12)CO and (13)CO line ratios the models require densities of close to 105/cu cm or higher. Due to chemical fractionation the isotopic line intensity ratios for (12)CI/(13)CI can be a factor 2 to 3 lower than the intrinsic isotopic C-12/C-13 ratio. The high-J (12)CO brightness temperatures that we find are in general agreement with earlier PDR models.

Tsunami Inundation Mapping for the Upper East Coast of the United States

NASA Astrophysics Data System (ADS)

Tehranirad, B.; Kirby, J. T., Jr.; Callahan, J. A.; Shi, F.; Banihashemi, S.; Grilli, S. T.; Grilli, A. R.; Tajalli Bakhsh, T. S.; O'Reilly, C.

2014-12-01

We describe the modeling of tsunami inundation for the Upper US East Coast (USEC) from Ocean City, MD up to Nantucket, MA. and the development of inundation maps for use in emergency management and hazard analysis. Seven tsunami sources were used as initial conditions in order to develop inundation maps based on a Probable Maximum Tsunami approach. Of the seven, two coseismic sources were used; the first being a large earthquake in the Puerto Rico Trench, in the well-known Caribbean Subduction Zone, and the second, an earthquake close to the Azores Gibraltar plate boundary known as the source of the biggest tsunami recorded in the North Atlantic Basin. In addition, four Submarine Mass Failure (SMF) sources located at different locations on the edge of the shelf break were simulated. Finally, the Cumbre Vieja Volcanic (CVV) collapse, located in the Canary Islands, was studied. For this presentation, we discuss modeling results for nearshore tsunami propagation and onshore inundation. A fully nonlinear Boussinesq model (FUNWAVE-TVD) is used to capture the characteristics of tsunami propagation, both nearshore and inland. In addition to the inundation line as the main result of this work, other tsunami quantities such as inundation depth and maximum velocities will be discussed for the whole USEC area. Moreover, a discussion of most vulnerable areas to a possible tsunami in the USEC will be provided. For example, during the inundation simulation process, it was observed that coastal environments with barrier islands are among the hot spots to be significantly impacted by a tsunami. As a result, areas like western Long Island, NY and Atlantic City, NJ are some of the locations that will get extremely affected in case of a tsunami occurrence in the Atlantic Ocean. Finally, the differences between various tsunami sources modeled here will be presented. Although inundation lines for different sources usually follow a similar pattern, there are clear distinctions between the inundation depth and other tsunami features in different areas. Figure below shows the inundation depth for surrounding area of the Ocean City, MD. Figure (a) and (b) are the envelope inundation depth for SMF and coseismic sources. Figure (C) shows the inundation depth for CVV source, which clearly has the largest magnitude amongst the sources studied for this work.

A soft X-ray map of the Perseus cluster of galaxies

NASA Technical Reports Server (NTRS)

Cash, W.; Malina, R. F.; Wolff, R. S.

1976-01-01

A 0.5-3-keV X-ray map of the Perseus cluster of galaxies is presented. The map shows a region of strong emission centered near NGC 1275 plus a highly elongated emission region which lies along the line of bright galaxies that dominates the core of the cluster. The data are compared with various models that include point and diffuse sources. One model which adequately represents the data is the superposition of a point source at NGC 1275 and an isothermal ellipsoid resulting from the bremsstrahlung emission of cluster gas. The ellipsoid has a major core radius of 20.5 arcmin and a minor core radius of 5.5 arcmin, consistent with the values obtained from galaxy counts. All acceptable models provide evidence for a compact source (less than 3 arcmin FWHM) at NGC 1275 containing about 25% of the total emission. Since the diffuse X-ray and radio components have radically different morphologies, it is unlikely that the emissions arise from a common source, as proposed in inverse-Compton models.

The broad-band X-ray spectral variability of Mrk 841

NASA Technical Reports Server (NTRS)

George, I. M.; Nandra, K.; Fabian, A. C.; Turner, T. J.; Done, C.; Day, C. S. R.

1993-01-01

A detailed spectral analysis of five X-ray observations of Mrk 841 with the EXOSAT, Ginga, and ROSAT satellites is reported. Variability is apparent in both the soft (0.1-1.0 keV) and medium (1-20 keV) energy bands. Above, 1 keV, the spectra are adequately modeled by a power law with a strong emission line of equivalent width 450 eV. The large equivalent width of the emission line indicates a strongly enhanced reflection component of the source compared with other Seyferts observed with Ginga. The implications of the results of the analysis for physical models of the emission regions in this and other X-ray bright Seyferts are briefly examined.

The Nustar Spectrum of Mrk 335: Extreme Relativistic Effects Within Two Gravitational Radii of the Event Horizon?

NASA Technical Reports Server (NTRS)

Parker, M. L.; Wilkins, D. R.; Fabian, A. C.; Grupe, D.; Dauser, T.; Matt, G.; Harrison, F. A.; Brenneman, L.; Boggs, S. E.; Christensen, F. E.;

IC 3639—a New Bona Fide Compton-Thick AGN Unveiled by NuSTAR

NASA Astrophysics Data System (ADS)

Boorman, Peter G.; Gandhi, P.; Alexander, D. M.; Annuar, A.; Ballantyne, D. R.; Bauer, F.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Hönig, S. F.; Koss, M.; LaMassa, S. M.; Masini, A.; Ricci, C.; Risaliti, G.; Stern, D.; Zhang, W. W.

2016-12-01

We analyze high-quality NuSTAR observations of the local (z = 0.011) Seyfert 2 active galactic nucleus (AGN) IC 3639, in conjunction with archival Suzaku and Chandra data. This provides the first broadband X-ray spectral analysis of the source, spanning nearly two decades in energy (0.5-30 keV). Previous X-ray observations of the source below 10 keV indicated strong reflection/obscuration on the basis of a pronounced iron fluorescence line at 6.4 keV. The hard X-ray energy coverage of NuSTAR, together with self-consistent toroidal reprocessing models, enables direct broadband constraints on the obscuring column density of the source. We find the source to be heavily Compton-thick (CTK) with an obscuring column in excess of 3.6× {10}24 cm-2, unconstrained at the upper end. We further find an intrinsic 2-10 keV luminosity of {{log}}10({L}2{--10{keV}} [{erg} {{{s}}}-1])={43.4}-1.1+0.6 to 90% confidence, almost 400 times the observed flux, and consistent with various multiwavelength diagnostics. Such a high ratio of intrinsic to observed flux, in addition to an Fe-Kα fluorescence line equivalent width exceeding 2 keV, is extreme among known bona fide CTK AGNs, which we suggest are both due to the high level of obscuration present around IC 3639. Our study demonstrates that broadband spectroscopic modeling with NuSTAR enables large corrections for obscuration to be carried out robustly and emphasizes the need for improved modeling of AGN tori showing intense iron fluorescence.

Modeling operational behavior of a disassembly line

NASA Astrophysics Data System (ADS)

Kizilkaya, Elif A.; Gupta, Surendra M.

2004-12-01

In this paper we present a dynamic kanban (pull) system specifically developed for disassembly lines. This type of kanban system is much more complex than the traditional kanban system used in assembly lines. For instance, unlike the assembly line where the external demand occurs only at the last station, the demands in the disassembly case also occur at any of the intermittent stations. The reason is that as a product moves on the disassembly line, various parts are disassembled at every station and accumulated at that station. Therefore, there are as many demand sources as there are number of parts. We consider a case example involving the end-of-life products. Based on the precedence relationships and other criteria such as hazardous properties of the parts, we balance the disassembly line. The results of the disassembly line-balancing problem (DLBP) are used as input to the proposed dynamic kanban system for disassembly line (DKSDL). We compare the performance of the DKSDL to the modified kanban system for disassembly line (MKSDL), which was previously introduced by the authors. We show, via simulation, that the DKSDL is far superior to MKSDL considered.

Evaluation and utilization of beam simulation codes for the SNS ion source and low energy beam transport developmenta)

NASA Astrophysics Data System (ADS)

Han, B. X.; Welton, R. F.; Stockli, M. P.; Luciano, N. P.; Carmichael, J. R.

2008-02-01

Beam simulation codes PBGUNS, SIMION, and LORENTZ-3D were evaluated by modeling the well-diagnosed SNS base line ion source and low energy beam transport (LEBT) system. Then, an investigation was conducted using these codes to assist our ion source and LEBT development effort which is directed at meeting the SNS operational and also the power-upgrade project goals. A high-efficiency H- extraction system as well as magnetic and electrostatic LEBT configurations capable of transporting up to 100mA is studied using these simulation tools.

An Analysis of Water Line Profiles in Star Formation Regions Observed by SWAS

NASA Technical Reports Server (NTRS)

Ashby, Matthew L. N.; Bergin, Edwin A.; Plume, Rene; Carpenter, John M.; Neufeld, David A.; Chin, Gordon; Erickson, Neal R.; Goldsmith, Paul F.; Harwit, Martin; Howe, J. E.

2000-01-01

We present spectral line profiles for the 557 GHz 1(sub 1,0) yields 1(sub 0,1) ground-state rotational transition of ortho-H2(16)O for 18 galactic star formation regions observed by SWAS. 2 Water is unambiguously detected in every source. The line profiles exhibit a wide variety of shapes, including single-peaked spectra and self-reversed profiles. We interpret these profiles using a Monte Carlo code to model the radiative transport. The observed variations in the line profiles can be explained by variations in the relative strengths of the bulk flow and small-scale turbulent motions within the clouds. Bulk flow (infall, outflow) must be present in some cloud cores, and in certain cases this bulk flow dominates the turbulent motions.

H2-,He-and CO2-line broadening coefficients and pressure shifts for the HITRAN database

NASA Astrophysics Data System (ADS)

Wilzewski, Jonas; Gordon, Iouli E.; Rothman, Laurence S.

2014-06-01

To increase the potential of the HITRAN database in astronomy, experimental and theoretical line broadening coefficients and line shifts of molecules of planetary interest broadened by H2,He,and CO2 have been assembled from available peer-reviewed sources. Since H2 and He are major constituents in the atmospheres of gas giants, and CO2 predominates in atmospheres of some rocky planets with volcanic activity, these spectroscopic data are important for studying planetary atmospheres. The collected data were used to create semi-empirical models for complete data sets from the microwave to the UV part of the spectrum of the studied molecules. The presented work will help identify the need for further investigations of broadening and shifting of spectral lines.

Radiative transfer of X-rays in the solar corona

NASA Technical Reports Server (NTRS)

Acton, L. W.

1978-01-01

The problem of resonance scattering of X-ray emission lines in the solar corona is investigated. For the resonance lines of some helium-like ions, significant optical depths are reached over distances small compared with the size of typical coronal features. A general integral equation for the transfer of resonance-line radiation under solar coronal conditions is derived. This expression is in a form useful for modeling the complex three-dimensional temperature and density structure of coronal active regions. The transfer equation is then cast in a form illustrating the terms which give rise to the attenuation or enhancement of the resonance-line intensity. The source function for helium-like oxygen (O VII) under coronal conditions is computed and discussed in terms of the relative importance of scattering.

A Comparison of Air Force Data Systems

DTIC Science & Technology

1993-08-01

a software cost model, SPQR . This model was chosen because it provides a straightforward means of modeling the enhancements as they V i VII-25 I would...estimated by SPQR (23,917) by $69 per hour for a total of $1,650,273. An additional 10 percent was added for generating or modifying the Middleware...equipment3 SLOC source lines of code SPO System Program Office SPQR System Product Quality Reporting SSC Standard Systems Center SSI system-to-system

THE CORES OF THE Fe K{alpha} LINES IN ACTIVE GALACTIC NUCLEI: AN EXTENDED CHANDRA HIGH ENERGY GRATING SAMPLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu, X. W.; Wang, J. X.; Yaqoob, T.

We extend the study of the core of the Fe K{alpha} emission line at {approx}6.4 keV in Seyfert galaxies reported by Yaqoob and Padmanabhan using a larger sample observed by the Chandra high-energy grating (HEG). The sample consists of 82 observations of 36 unique sources with z < 0.3. Whilst heavily obscured active galactic nuclei are excluded from the sample, these data offer some of the highest precision measurements of the peak energy of the Fe K{alpha} line, and the highest spectral resolution measurements of the width of the core of the line in unobscured and moderately obscured (N {submore » H} < 10{sup 23} cm{sup -2}) Seyfert galaxies to date. From an empirical and uniform analysis, we present measurements of the Fe K{alpha} line centroid energy, flux, equivalent width (EW), and intrinsic width (FWHM). The Fe K{alpha} line is detected in 33 sources, and its centroid energy is constrained in 32 sources. In 27 sources, the statistical quality of the data is good enough to yield measurements of the FWHM. We find that the distribution in the line centroid energy is strongly peaked around the value for neutral Fe, with over 80% of the observations giving values in the range 6.38-6.43 keV. Including statistical errors, 30 out of 32 sources ({approx}94%) have a line centroid energy in the range 6.35-6.47 keV. The mean EW, among the observations in which a non-zero lower limit could be measured, was 53 {+-} 3 eV. The mean FWHM from the subsample of 27 sources was 2060 {+-} 230 km s{sup -1}. The mean EW and FWHM are somewhat higher when multiple observations for a given source are averaged. From a comparison with the H{beta} optical emission-line widths (or, for one source, Br{alpha}), we find that there is no universal location of the Fe K{alpha} line-emitting region relative to the optical broad-line region (BLR). In general, a given source may have contributions to the Fe K{alpha} line flux from parsec-scale distances from the putative black hole, down to matter a factor {approx}2 closer to the black hole than the BLR. We confirm the presence of the X-ray Baldwin effect, an anti-correlation between the Fe K{alpha} line EW and X-ray continuum luminosity. The HEG data have enabled isolation of this effect to the narrow core of the Fe K{alpha} line.« less

Polar cap models of gamma-ray pulsars: Emision from single poles of nearly aligned rotators

NASA Technical Reports Server (NTRS)

Daugherty, Joseph K.; Harding, Alice K.

1994-01-01

We compare a new Monte Carlo simulation of polar cap models for gamma-ray pulsars with observations of sources detected above 10 MeV by the Compton Observatory (CGRO). We find that for models in which the inclination of the magnetic axis is comparable to the angular radius of the polar cap, the radiation from a single cap may exhibit a pusle with either a single broad peak as in PSR 1706-44 and PSR 1055-52, or a doubly peaked profile comparable to those observed from the Crab, Vela and Geminga pulsars. In general, double pulses are seen by observers whose line of sight penetrates into the cap interior and are due to enhanced emission near the rim. For cascades induced by culvature radiation, increased rim emission occurs even when electrons are accelerated over the entire cap, since electrons from the interior escape along magnetic field lines with less curvature and hence emit less radiation. However, we obtain better fits to the duty cycles of observed profiles if we make the empirical assumption that acceleration occurs only near the rim. In either case, the model energy spectra are consistent with most of the observed sources. The beaming factors expected from nearly aligned rotators, based on standard estimates for the cap radius, imply that their luminosities need not be as large as in the case of orthogonal rotators. However, small beam angles are also a difficutly with this model because they imply low detection probablities. In either case the polar cap radius is a critical factor, and in this context we point out that plasma loading of the field lines should make the caps larger than the usual estimates based on pure dipole fields.

HR Del REMNANT ANATOMY USING TWO-DIMENSIONAL SPECTRAL DATA AND THREE-DIMENSIONAL PHOTOIONIZATION SHELL MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moraes, Manoel; Diaz, Marcos

2009-12-15

The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in H{alpha}, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structuremore » seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10{sup -4} M {sub sun} is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.« less

The rank correlated FSK model for prediction of gas radiation in non-uniform media, and its relationship to the rank correlated SLW model

NASA Astrophysics Data System (ADS)

Solovjov, Vladimir P.; Webb, Brent W.; Andre, Frederic

2018-07-01

Following previous theoretical development based on the assumption of a rank correlated spectrum, the Rank Correlated Full Spectrum k-distribution (RC-FSK) method is proposed. The method proves advantageous in modeling radiation transfer in high temperature gases in non-uniform media in two important ways. First, and perhaps most importantly, the method requires no specification of a reference gas thermodynamic state. Second, the spectral construction of the RC-FSK model is simpler than original correlated FSK models, requiring only two cumulative k-distributions. Further, although not exhaustive, example problems presented here suggest that the method may also yield improved accuracy relative to prior methods, and may exhibit less sensitivity to the blackbody source temperature used in the model predictions. This paper outlines the theoretical development of the RC-FSK method, comparing the spectral construction with prior correlated spectrum FSK method formulations. Further the RC-FSK model's relationship to the Rank Correlated Spectral Line Weighted-sum-of-gray-gases (RC-SLW) model is defined. The work presents predictions using the Rank Correlated FSK method and previous FSK methods in three different example problems. Line-by-line benchmark predictions are used to assess the accuracy.

4 years of PM10 pollution in Poland - observations and modelling

NASA Astrophysics Data System (ADS)

Durka, Pawel; Struzewska, Joanna; Kaminski, Jacek W.

2017-04-01

Poor air quality is a health issue in Poland, especially during winter. In central and northern part of the country, the primary source is low-level domestic emissions. In larger cities and agglomerations traffic emissions are also an issue. Quantification of the contribution of transboundary pollution sources is still an open issue. Analyses of 60 episodes for the period 2013-2016 with high PM10 concentrations were carried out under a contract from the Chief Inspectorate of Environmental Protection in Poland. Analyses of synoptic conditions and calculation of back trajectories were undertaken. A tropospheric chemistry model GEM-AQ was run at 10km resolution to calculate contributions from surface, line and point sources. We will present trajectories for different types of episodes, maps with contributions for specific emission sources and transboundary pollution. Also, mean distribution of PM10 concentrations during episodes will be shown.

Absorption of solar radiation by O2 - Implications for O3 and lifetimes of N2O, CFCl3, and CF2Cl2

NASA Technical Reports Server (NTRS)

Minschwaner, K.; Salawitch, R. J.; Mcelroy, M. B.

1993-01-01

An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of O2 on transmission of UV radiation. The model is used to evaluate rates of photolysis for N2O, CFCl3, and CF2Cl2, and to infer global loss rates and instantaneous lifetimes appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission in the Schumann-Runge region is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxygen exceeds production by photolysis of O2 for altitudes above 40 km. The imbalance between production and loss is shown to be consistent with a source of odd oxygen proportional to the product of the mixing ratio and photolysis rate of ozone, which suggests that processes involving vibrationally excited O2 may play an important role in production of odd oxygen.

Capability of a Mobile Monitoring System to Provide Real-Time Data Broadcasting and Near Real-Time Source Attribution

NASA Astrophysics Data System (ADS)

Erickson, M.; Olaguer, J.; Wijesinghe, A.; Colvin, J.; Neish, B.; Williams, J.

2014-12-01

It is becoming increasingly important to understand the emissions and health effects of industrial facilities. Many areas have no or limited sustained monitoring capabilities, making it difficult to quantify the major pollution sources affecting human health, especially in fence line communities. Developments in real-time monitoring and micro-scale modeling offer unique ways to tackle these complex issues. This presentation will demonstrate the capability of coupling real-time observations with micro-scale modeling to provide real-time information and near real-time source attribution. The Houston Advanced Research Center constructed the Mobile Acquisition of Real-time Concentrations (MARC) laboratory. MARC consists of a Ford E-350 passenger van outfitted with a Proton Transfer Reaction Mass Spectrometer (PTR-MS) and meteorological equipment. This allows for the fast measurement of various VOCs important to air quality. The data recorded from the van is uploaded to an off-site database and the information is broadcast to a website in real-time. This provides for off-site monitoring of MARC's observations, which allows off-site personnel to provide immediate input to the MARC operators on how to best achieve project objectives. The information stored in the database can also be used to provide near real-time source attribution. An inverse model has been used to ascertain the amount, location, and timing of emissions based on MARC measurements in the vicinity of industrial sites. The inverse model is based on a 3D micro-scale Eulerian forward and adjoint air quality model known as the HARC model. The HARC model uses output from the Quick Urban and Industrial Complex (QUIC) wind model and requires a 3D digital model of the monitored facility based on lidar or industrial permit data. MARC is one of the instrument platforms deployed during the 2014 Benzene and other Toxics Exposure Study (BEE-TEX) in Houston, TX. The main goal of the study is to quantify and explain the origin of ambient exposure to hazardous air pollutants in an industrial fence line community near the Houston Ship Channel. Preliminary results derived from analysis of MARC observations during the BEE-TEX experiment will be presented.

Corona, Jet, and Relativistic Line Models for Suzaku/RXTE/Chandra-HETG Observations of the Cygnus X-1 Hard State

NASA Technical Reports Server (NTRS)

Nowak, Michael A.; Hanke, Manfred; Trowbridge, Sarah N.; Markoff, Sera B.; Wilms, Joern; Pottschmidt, Katja; Coppi, Paolo; Maitra, Dipankar; Davis, Jhn E.; Tramper, Frank

2009-01-01

Using Suzaku and the Rossi X-ray Timing Explorer (RXTE), we have conducted a series of four simultaneous observations of the galactic black hole candidate Cyg X-1 in what were historically faint and spectrally hard "low states". Additionally, all of these observations occurred near superior conjunction with our line of sight to the X-ray source passing through the dense phases of the "focused wind" from the mass donating secondary. One of our observations was also simultaneous with observations by the Chandra-High Energy Transmission Grating (HETG). These latter spectra are crucial for revealing the ionized absorption due to the secondary s focused wind. Such absorption is present and must be accounted for in all four spectra. These simultaneous data give an unprecedented view of the 0.8-300 keV spectrum of Cyg X-1, and hence bear upon both corona and X-ray emitting jet models of black hole hard states. Three models fit the spectra well: coronae with thermal or mixed thermal/non-thermal electron populations, and jets. All three models require a soft component that we fit with a low temperature disk spectrum with an inner radius of only a few tens of GM/c2. All three models also agree that the known spectral break at 10 keV is not solely due to the presence of reflection, but each gives a different underlying explanation for the augmentation of this break. Thus whereas all three models require that there is a relativistically broadened Fe line, the strength and inner radius of such a line is dependent upon the specific model, thus making premature line-based estimates of the black hole spin in the Cyg X-1 system. We look at the relativistic line in detail, accounting for the narrow Fe emission and ionized absorption detected by HETG. Although the specific relativistic parameters of the line are continuum-dependent, none of the broad line fits allow for an inner disk radius that is > 40 GM/c(sup 2).

Chandra ACIS-I particle background: an analytical model

NASA Astrophysics Data System (ADS)

Bartalucci, I.; Mazzotta, P.; Bourdin, H.; Vikhlinin, A.

2014-06-01

Aims: Imaging and spectroscopy of X-ray extended sources require a proper characterisation of a spatially unresolved background signal. This background includes sky and instrumental components, each of which are characterised by its proper spatial and spectral behaviour. While the X-ray sky background has been extensively studied in previous work, here we analyse and model the instrumental background of the ACIS-I detector on board the Chandra X-ray observatory in very faint mode. Methods: Caused by interaction of highly energetic particles with the detector, the ACIS-I instrumental background is spectrally characterised by the superimposition of several fluorescence emission lines onto a continuum. To isolate its flux from any sky component, we fitted an analytical model of the continuum to observations performed in very faint mode with the detector in the stowed position shielded from the sky, and gathered over the eight-year period starting in 2001. The remaining emission lines were fitted to blank-sky observations of the same period. We found 11 emission lines. Analysing the spatial variation of the amplitude, energy and width of these lines has further allowed us to infer that three lines of these are presumably due to an energy correction artefact produced in the frame store. Results: We provide an analytical model that predicts the instrumental background with a precision of 2% in the continuum and 5% in the lines. We use this model to measure the flux of the unresolved cosmic X-ray background in the Chandra deep field south. We obtain a flux of 10.2+0.5-0.4 × 10-13 erg cm-2 deg-2 s-1 for the [1-2] keV band and (3.8 ± 0.2) × 10-12 erg cm-2 deg-2 s-1 for the [2-8] keV band.

Development of an analytical-numerical model to predict radiant emission or absorption

NASA Technical Reports Server (NTRS)

Wallace, Tim L.

1994-01-01

The development of an analytical-numerical model to predict radiant emission or absorption is discussed. A voigt profile is assumed to predict the spectral qualities of a singlet atomic transition line for atomic species of interest to the OPAD program. The present state of this model is described in each progress report required under contract. Model and code development is guided by experimental data where available. When completed, the model will be used to provide estimates of specie erosion rates from spectral data collected from rocket exhaust plumes or other sources.

Atomic Data and Spectral Line Intensities for Be-like Ions

NASA Technical Reports Server (NTRS)

Bhatia, Anand; Landi, E.

2008-01-01

Atomic data and collision rates are needed to model the spectrum of optically thin astrophysical sources. Recent observations from solar instrumentation such as SOH0 and Hinode have revealed the presence of hosts of lines emitted by high-energy configurations from ions belonging to the Be-like to the 0-like isoelectronic sequences. Data for such configurations are often unavailable in the literature. We have started a program to calculate the atomic parameters and rates for the high-energy configurations of Be-like ions of the type ls2.21.nl' where n=3,4,5. We report on the results of this project and on the diagnostic application of the predicted spectral lines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Steven J.; Carlsten, Bruce E.

We will quickly go through the history of the non-linear transmission lines (NLTLs). We will describe how they work, how they are modeled and how they are designed. Note that the field of high power, NLTL microwave sources is still under development, so this is just a snap shot of their current state. Topics discussed are: (1) Introduction to solitons and the KdV equation; (2) The lumped element non-linear transmission line; (3) Solution of the KdV equation; (4) Non-linear transmission lines at microwave frequencies; (5) Numerical methods for NLTL analysis; (6) Unipolar versus bipolar input; (7) High power NLTL pioneers;more » (8) Resistive versus reactive load; (9) Non-lineaer dielectrics; and (10) Effect of losses.« less

A comprehensive approach to reactive power scheduling in restructured power systems

NASA Astrophysics Data System (ADS)

Shukla, Meera

Financial constraints, regulatory pressure, and need for more economical power transfers have increased the loading of interconnected transmission systems. As a consequence, power systems have been operated close to their maximum power transfer capability limits, making the system more vulnerable to voltage instability events. The problem of voltage collapse characterized by a severe local voltage depression is generally believed to be associated with inadequate VAr support at key buses. The goal of reactive power planning is to maintain a high level of voltage security, through installation of properly sized and located reactive sources and their optimal scheduling. In case of vertically-operated power systems, the reactive requirement of the system is normally satisfied by using all of its reactive sources. But in case of different scenarios of restructured power systems, one may consider a fixed amount of exchange of reactive power through tie lines. Reviewed literature suggests a need for optimal scheduling of reactive power generation for fixed inter area reactive power exchange. The present work proposed a novel approach for reactive power source placement and a novel approach for its scheduling. The VAr source placement technique was based on the property of system connectivity. This is followed by development of optimal reactive power dispatch formulation which facilitated fixed inter area tie line reactive power exchange. This formulation used a Line Flow-Based (LFB) model of power flow analysis. The formulation determined the generation schedule for fixed inter area tie line reactive power exchange. Different operating scenarios were studied to analyze the impact of VAr management approach for vertically operated and restructured power systems. The system loadability, losses, generation and the cost of generation were the performance measures to study the impact of VAr management strategy. The novel approach was demonstrated on IEEE 30 bus system.

A Survey of X-Ray Variability in Seyfert 1 Galaxies with XMM-Newton to study the soft excess and the broad Fe lines

NASA Astrophysics Data System (ADS)

Ponti, Gabriele

The nature of the soft excess and the presence of the broad Fe lines is still nowadays highly debated because the different absorption/emission models are degenerate. Spectral variability studies have the potential to break this degeneracy. I will present the results of a spectral variability RMS survey of the 36 brightest type 1 Seyfert galaxies observed by XMM-Newton for more than 30 ks. More than 80 as already measured, on longer timescales, with RXTE (Markowitz et al. 2004). About half of the sample show lower variability in the soft energy band, indicating that the emission from the soft excess is more stable than the one of the continuum. While the other sources show a soft excess that is as variable as the continuum. About half of the sample do not show an excess of variability where the warm absorber component imprints its stronger features, suggesting that for these sources the soft excess is not produced by a relativistic absorbing wind. In a few bright and well exposed sources it has been possible to measure an excess of variability at the energy of the broad component of the Fe K line, in agreement with the broad emission line interpretation. For the sources where more than one observation was available the stability of the shape of the RMS spectrum has been investigated. Moreover, it will be presented the results of the computation of the excess variance of all the radio quiet type 1 AGN of the XMM-Newton database. The relations between variability, black hole mass, accretion rate and luminosity are investigated and their scatter measured.

Finite element solution to passive scalar transport behind line sources under neutral and unstable stratification

NASA Astrophysics Data System (ADS)

Liu, Chun-Ho; Leung, Dennis Y. C.

2006-02-01

This study employed a direct numerical simulation (DNS) technique to contrast the plume behaviours and mixing of passive scalar emitted from line sources (aligned with the spanwise direction) in neutrally and unstably stratified open-channel flows. The DNS model was developed using the Galerkin finite element method (FEM) employing trilinear brick elements with equal-order interpolating polynomials that solved the momentum and continuity equations, together with conservation of energy and mass equations in incompressible flow. The second-order accurate fractional-step method was used to handle the implicit velocity-pressure coupling in incompressible flow. It also segregated the solution to the advection and diffusion terms, which were then integrated in time, respectively, by the explicit third-order accurate Runge-Kutta method and the implicit second-order accurate Crank-Nicolson method. The buoyancy term under unstable stratification was integrated in time explicitly by the first-order accurate Euler method. The DNS FEM model calculated the scalar-plume development and the mean plume path. In particular, it calculated the plume meandering in the wall-normal direction under unstable stratification that agreed well with the laboratory and field measurements, as well as previous modelling results available in literature.

FDTD Modeling of LEMP Propagation in the Earth-Ionosphere Waveguide With Emphasis on Realistic Representation of Lightning Source

NASA Astrophysics Data System (ADS)

Tran, Thang H.; Baba, Yoshihiro; Somu, Vijaya B.; Rakov, Vladimir A.

2017-12-01

The finite difference time domain (FDTD) method in the 2-D cylindrical coordinate system was used to compute the nearly full-frequency-bandwidth vertical electric field and azimuthal magnetic field waveforms produced on the ground surface by lightning return strokes. The lightning source was represented by the modified transmission-line model with linear current decay with height, which was implemented in the FDTD computations as an appropriate vertical phased-current-source array. The conductivity of atmosphere was assumed to increase exponentially with height, with different conductivity profiles being used for daytime and nighttime conditions. The fields were computed at distances ranging from 50 to 500 km. Sky waves (reflections from the ionosphere) were identified in computed waveforms and used for estimation of apparent ionospheric reflection heights. It was found that our model reproduces reasonably well the daytime electric field waveforms measured at different distances and simulated (using a more sophisticated propagation model) by Qin et al. (2017). Sensitivity of model predictions to changes in the parameters of atmospheric conductivity profile, as well as influences of the lightning source characteristics (current waveshape parameters, return-stroke speed, and channel length) and ground conductivity were examined.

Mapping the Solar Wind from its Source Region into the Outer Corona

NASA Technical Reports Server (NTRS)

Esser, Ruth

1998-01-01

Knowledge of the radial variation of the plasma conditions in the coronal source region of the solar wind is essential to exploring coronal heating and solar wind acceleration mechanisms. The goal of the present proposal is to determine as many plasma parameters in that region as possible by coordinating different observational techniques, such as Interplanetary Scintillation Observations, spectral line intensity observations, polarization brightness measurements and X-ray observations. The inferred plasma parameters are then used to constrain solar wind models.

Modeling Magnetospheric Sources

NASA Technical Reports Server (NTRS)

Walker, Raymond J.; Ashour-Abdalla, Maha; Ogino, Tatsuki; Peroomian, Vahe; Richard, Robert L.

2001-01-01

We have used global magnetohydrodynamic, simulations of the interaction between the solar wind and magnetosphere together with single particle trajectory calculations to investigate the sources of plasma entering the magnetosphere. In all of our calculations solar wind plasma primarily enters the magnetosphere when the field line on which it is convecting reconnects. When the interplanetary magnetic field has a northward component the reconnection is in the polar cusp region. In the simulations plasma in the low latitude boundary layer (LLBL) can be on either open or closed field lines. Open field lines occur when the high latitude reconnection occurs in only one cusp. In the MHD calculations the ionosphere does not contribute significantly to the LLBL for northward IMF. The particle trajectory calculations show that ions preferentially enter in the cusp region where they can be accelerated by non-adiabatic motion across the high latitude electric field. For southward IMF in the MHD simulations the plasma in the middle and inner magnetosphere comes from the inner (ionospheric) boundary of the simulation. Solar wind plasma on open field lines is confined to high latitudes and exits the tailward boundary of the simulation without reaching the plasma sheet. The LLBL is populated by both ionospheric and solar wind plasma. When the particle trajectories are included solar wind ions can enter the middle magnetosphere. We have used both the MHD simulations and the particle calculations to estimate source rates for the magnetosphere which are consistent with those inferred from observations.

Toward a Quantitative Comparison of Magnetic Field Extrapolations and Observed Coronal Loops

NASA Astrophysics Data System (ADS)

Warren, Harry P.; Crump, Nicholas A.; Ugarte-Urra, Ignacio; Sun, Xudong; Aschwanden, Markus J.; Wiegelmann, Thomas

2018-06-01

It is widely believed that loops observed in the solar atmosphere trace out magnetic field lines. However, the degree to which magnetic field extrapolations yield field lines that actually do follow loops has yet to be studied systematically. In this paper, we apply three different extrapolation techniques—a simple potential model, a nonlinear force-free (NLFF) model based on photospheric vector data, and an NLFF model based on forward fitting magnetic sources with vertical currents—to 15 active regions that span a wide range of magnetic conditions. We use a distance metric to assess how well each of these models is able to match field lines to the 12202 loops traced in coronal images. These distances are typically 1″–2″. We also compute the misalignment angle between each traced loop and the local magnetic field vector, and find values of 5°–12°. We find that the NLFF models generally outperform the potential extrapolation on these metrics, although the differences between the different extrapolations are relatively small. The methodology that we employ for this study suggests a number of ways that both the extrapolations and loop identification can be improved.

ATLOG Modeling of Aerial Cable from the November 2016 HERMES Electromagnetic Pulse Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

campione, salvatore; Warne, Larry K.; Yee, Benjamin Tong

2017-09-01

This report details the comparison of ATLOG modeling results for the response of a finite-length dissipative aerial conductor interacting with a conducting ground to a measurement taken November 2016 at the High-Energy Radiation Megavolt Electron Source (HERMES) facility. We use the ATLOG time-domain method based on transmission line theory. Good agreement is observed between simulations and experiments. Intentionally Left Blank

Tetrahedral node for Transmission-Line Modeling (TLM) applied to Bio-heat Transfer.

PubMed

Milan, Hugo F M; Gebremedhin, Kifle G

2016-12-01

Transmission-Line Modeling (TLM) is a numerical method used to solve complex and time-domain bio-heat transfer problems. In TLM, parallelepipeds are used to discretize three-dimensional problems. The drawback in using parallelepiped shapes is that instead of refining only the domain of interest, a large additional domain would also have to be refined, which results in increased computational time and memory space. In this paper, we developed a tetrahedral node for TLM applied to bio-heat transfer that does not have the drawback associated with the parallelepiped node. The model includes heat source, blood perfusion, boundary conditions and initial conditions. The boundary conditions could be adiabatic, temperature, heat flux, or convection. The predicted temperature and heat flux were compared against results from an analytical solution and the results agreed within 2% for a mesh size of 69,941 nodes and a time step of 5ms. The method was further validated against published results of maximum skin-surface temperature difference in a breast with and without tumor and the results agreed within 6%. The published results were obtained from a model that used parallelepiped TLM node. An open source software, TLMBHT, was written using the theory developed herein and is available for download free-of-charge. Copyright © 2016 Elsevier Ltd. All rights reserved.

Combining land use information and small stream sampling with PCR-based methods for better characterization of diffuse sources of human fecal pollution.

PubMed

Peed, Lindsay A; Nietch, Christopher T; Kelty, Catherine A; Meckes, Mark; Mooney, Thomas; Sivaganesan, Mano; Shanks, Orin C

2011-07-01

Diffuse sources of human fecal pollution allow for the direct discharge of waste into receiving waters with minimal or no treatment. Traditional culture-based methods are commonly used to characterize fecal pollution in ambient waters, however these methods do not discern between human and other animal sources of fecal pollution making it difficult to identify diffuse pollution sources. Human-associated quantitative real-time PCR (qPCR) methods in combination with low-order headwatershed sampling, precipitation information, and high-resolution geographic information system land use data can be useful for identifying diffuse source of human fecal pollution in receiving waters. To test this assertion, this study monitored nine headwatersheds over a two-year period potentially impacted by faulty septic systems and leaky sanitary sewer lines. Human fecal pollution was measured using three different human-associated qPCR methods and a positive significant correlation was seen between abundance of human-associated genetic markers and septic systems following wet weather events. In contrast, a negative correlation was observed with sanitary sewer line densities suggesting septic systems are the predominant diffuse source of human fecal pollution in the study area. These results demonstrate the advantages of combining water sampling, climate information, land-use computer-based modeling, and molecular biology disciplines to better characterize diffuse sources of human fecal pollution in environmental waters.

Simultaneous ASCA and EUVE Observations of Capella

NASA Astrophysics Data System (ADS)

Brickhouse, N. S.; Dupree, A. K.; Edgar, R. J.; Drake, S. A.; White, N. E.; Liedahl, D. A.; Singh, K. P.

1997-05-01

We present simultaneous observations taken in Mar 1996 of the bright stellar coronal source Capella (HD 34029) with the ASCA and EUVE satellites. Previous EUVE observations of Fe emission lines (Fe VIII --- XXIV, excluding XVII) revealed a narrow emission measure feature at 6 x 10(6) K, which has proven to be remarkably stable over several years (flux from Fe XVIII and XIX has not varied by more than 30%), while lines formed at higher temperatures have shown intensity variations up to factors of 4. Furthermore, extremely high signal-to-noise spectra obtained by summing all EUVE measurements show that the Fe/H abundance ratio is consistent with solar photospheric. (See Dupree et al. 1993, ApJ, 418, L41; Brickhouse, Raymond, & Smith 1995, ApJSupp, 97, 551; Brickhouse 1996, IAU Coll. 152, Astrophysics in the Extreme Ultraviolet, Bowyer & Malina, eds (Kluwer), 141.) Meanwhile, the ASCA data of Capella have proven notoriously difficult to analyze. The performance verification (PV) phase data suggested a somewhat subsolar Fe abundance, but models were in poor agreement with the data (chi (2red) ~ 6). (See Drake 1996, Conf. on Cosmic Abundances, U. Maryland). Since the emission lines observed by EUVE are formed at the same emitting temperatures as the X-ray spectrum (Capella is ``soft'' such that very little flux is observed above 2 keV), the emission measure distribution derived from EUVE lines should provide a direct prediction of the X-ray spectrum, with only the relative abundances of species other than Fe as free parameters. Like the PV data, the new ASCA spectrum is not well fit by any of the standard models. Applying the constraints imposed by EUVE does not make a major improvement in the fit --- multi-thermal, variable abundance models such as Raymond-Smith and MEKAL do not provide any acceptable fit (chi (2red) > 5). We discuss our efforts to understand the X-ray spectrum, including studies of the uncertainties in the atomic data and of the underlying assumptions of the source models.

On determining dose rate constants spectroscopically

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, M.; Rogers, D. W. O.

2013-01-15

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of {sup 125}I and {sup 103}Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated {sup 125}I and {sup 103}Pd sources. Methods: Spectra generated by 14 {sup 125}I and 6 {sup 103}Pd seedsmore » were calculated in vacuo at 10 cm from the source in a 2.7 Multiplication-Sign 2.7 Multiplication-Sign 0.05 cm{sup 3} voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the {sup 125}I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for {sup 103}Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were Less-Than-Or-Slanted-Equal-To 0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in {sup 125}I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The {sup 103}Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are in much better agreement with the calculations using the NCRP Report 58 and NNDC(2000) initial spectra with average discrepancies of 0.9% and 1.7% for the {sup 125}I and {sup 103}Pd seeds, respectively. However, there are no differences in the calculated TG-43U1 brachytherapy parameters using either initial spectrum in both cases. Similarly, there were no differences outside the statistical uncertainties of 0.1% or 0.2%, in the average energy, air kerma/history, dose rate/history, and dose rate constant when calculated using either the full photon spectrum or the main-peaks-only spectrum. Conclusions: Our calculated dose rate constants based on using the calculated on-axis spectrum and a line or dual-point source model are in excellent agreement (0.5% on average) with the values of Chen and Nath, verifying the accuracy of their more approximate method of going from the spectrum to the dose rate constant. However, the dose rate constants based on full seed models differ by between +4.6% and -1.5% from those based on the line or dual-point source approximations. These results suggest that the main value of spectroscopic measurements is to verify full Monte Carlo models of the seeds by comparison to the calculated spectra.« less

An Improved Statistical Point-source Foreground Model for the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Murray, S. G.; Trott, C. M.; Jordan, C. H.

2017-08-01

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.

Do Atoms Really "Emit" Absorption Lines?

ERIC Educational Resources Information Center

Brecher, Kenneth

1991-01-01

Presents three absorption line sources that enhance student understanding of the phenomena associated with the interaction of light with matter and help dispel the misconception that atoms "emit" absorption lines. Sources include neodymium, food coloring and other common household liquids, and fluorescent materials. (MDH)

Neon and [CII] 158 μm Emission Line Profiles in Dusty Starbursts and Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Samsonyan, A.; Weedman, D.; Lebouteiller, V.; Barry, D.; Sargsyan, L.

2017-07-01

Identifying and understanding the initial formation of massive galaxies and quasars in the early universe is a fundamental goal of observational cosmology. A rapidly developing capability for tracing luminosity sources to high redshifts is the observation of the [CII] 158 μm emission line at redshifts z > 4 using ground based submillimeter interferometers, with detections now having been made to z = 7. This has long been known as the strongest far-infrared line in most sources, often carrying about 1% of the total source luminosity, and is thought to be associated with star formation because it should arise within the photodissociation region (PDR) surrounding starbursts. The sample of 382 extragalactic sources has been analysed that have mid-infrared,high resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS) and also spectroscopy of the [CII] 158 μm line with the Herschel Photodetector Array Camera and Spectrometer (PACS). The emission line profiles of [NeII] 12.81μm , [NeIII] 15.55 μm , and [CII] 158 μm are studied, and intrinsic line widths are determined. All line profiles together with overlays comparing positions of PACS and IRS observations are made available in the Cornell Atlas of Spitzer IRS Sources (CASSIS). Sources are classified from AGN to starburst based on equivalent widths of the 6.2 μm polycyclic aromatic hydrocarbon feature. It is found that intrinsic line widths do not change among classification for [CII], with median widths of 207 km s-1 for AGN, 248 km s-1 for composites, and 233 km s-1 for starbursts. The [NeII] line widths also do not change with classification, but [NeIII] lines are progressively broader from starburst to AGN. A small number of objects with unusually broad lines or unusual redshift differences in any feature are identified.

OCD: The offshore and coastal dispersion model. Volume 1. User's guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiCristofaro, D.C.; Hanna, S.R.

1989-11-01

The Offshore and Coastal Dispersion (OCD) Model has been developed to simulate the effect of offshore emissions from point, area, or line sources on the air quality of coastal regions. The OCD model was adapted from the EPA guideline model MPTER (EPA, 1980). Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. This is a revised OCD model, the fourth version to date. The volume is the User's Guide which includes a Model overview, technical description, user's instructions, and notes on model evaluation and results.

First detection of a THz water maser in NGC 7538-IRS1 with SOFIA and new 22 GHz e-MERLIN maps

NASA Astrophysics Data System (ADS)

Herpin, F.; Baudry, A.; Richards, A. M. S.; Gray, M. D.; Schneider, N.; Menten, K. M.; Wyrowski, F.; Bontemps, S.; Simon, R.; Wiesemeyer, H.

2017-10-01

Context. The formation of massive stars (M> 10M⊙, L > 103L⊙) is still not well understood. Accumulating a large amount of mass infalling within a single entity in spite of radiation pressure is possible if, in addition to several other conditions, enough thermal energy is released. Despite numerous water line observations over a broad range of energies obtained with the Herschel Space Observatory, observations were not able to trace the emission from the hot core around the newly forming protostellar object in most of the sources. Aims: We wish to probe the physical conditions and water abundance in the inner layers of the host protostellar object NGC 7538-IRS1 using a highly excited H2O line. Water maser models predict that several THz water masers should be detectable in these objects. We therefore aim to detect the o-H2O 82,7-73,4 line in a star forming region for the first time. Model calculations have predicted this line to show maser action. Methods: We present SOFIA observations of the o-H2O 82,7-73,4 line at 1296.41106 GHz and a 616-523 22 GHz e-MERLIN map of the region (the very first 22 GHz images made after the e-MERLIN upgrade). In order to be able to constrain the nature of the emission - thermal or maser - we used near-simultaneous observations of the 22 GHz water maser performed with the Effelsberg radiotelescope and e-MERLIN. A thermal water model using the RATRAN radiative transfer code is presented based on HIFI pointed observations. Molecular water abundances are derived for the hot core. Results: The o-H2O 82,7-73,4 line is detected toward NGC 7538-IRS1 with one feature at the source velocity (-57.7 kms-1) and another one at -48.4 kms-1. We propose that the emission at the source velocity is consistent with thermal excitation and is excited in the innermost part of the IRS1a, in the closest circumstellar environment of the massive protostellar object. The other emission is very likely the first detection of a water THz maser line, pumped by shocks due to the IRS1b outflow, in a star-forming region. Assuming thermal excitation of the THz line, the water abundance in the hot core of NGC 7538-IRS1 is estimated to be 5.2 × 10-5 with respect to H2. The reduced spectra and maps (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A52

Observational studies of regions of massive star formation

NASA Astrophysics Data System (ADS)

Cooper, Heather Danielle Blythe

2013-03-01

Massive stars have a profound influence on their surroundings. However, relatively little is known about their formation. The study of massive star formation is hindered by a lack of observational evidence, primarily due to difficulties observing massive stars at early stages in their development. The Red MSX Source survey (RMS survey) is a valuable tool with which to address these issues. Near-infrared H- and K-band spectra were taken for 247 candidate massive young stellar objects (MYSOs), selected from the RMS survey. 195 (∼80%) of the targets are YSOs, of which 131 are massive YSOs (LBOL>5E3L⊙, M>8 M⊙). This is the largest spectroscopic study of massive YSOs to date. This study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties, with HI, H2 Fe II, and CO among the most commonly observed lines. Evidence for disks and outflows was frequently seen. Comparisons of Brγ and H2 emission with low mass YSOs suggest that the emission mechanism for these lines is the same for low-, intermediate-, and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs. It was found that the YSOs form an evolutionary sequence, based on their spectra, consistent with the existing theoretical models. Type I YSOs have strong H2 emission, no ionized lines, and are redder than the other two subtypes. As such, these are considered to be the youngest sources. The Type III sources are bluest, and therefore considered to be the oldest subtype. They have strong H I lines and fluorescent Fe II 1.6878 μm emission. They may also have weak H2 emission. Type III sources may even be beginning to form a mini-H II region. XSHOOTER data from 10 Herbig Be stars were analysed. The evidence suggests that winds and disks are common among Herbig stars, as they are among their main sequence classical Be star counterparts. Line broadening was seen in many of the sources, though it was not possible to identify whether this was due to Stark broadening or electron scattering. The observations and analysis presented in this thesis are an important step forward for the field of massive star formation. They also have the potential to be a starting block for future work.

Diamagnetic reduction in the magnetic field above a sunspot in the gamma-ray burst on July 14, 2000

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kichigin, G. N., E-mail: king@iszf.irk.ru; Miroshnichenko, L. I.; Sidorov, V. I.

2015-08-15

Earlier, the authors proposed a model for describing the motion of trapped ions accelerated to energies of 10–100 MeV/nucleon in an electric field of 0.01–0.1 V/cm with a nonzero magnetic-field-aligned component in coronal solar loops with a characteristic size of ∼100 000 km. The simulation results were used to interpret the properties of gamma-ray sources in a powerful solar burst that occurred on July 14, 2000. According to the proposed model, the gamma-ray source emitting lines with photon energies of 4.1–6.7 MeV was located above the sunspot and the source of the 2.223-MeV line coincided with the region of themore » observed drop-out of accelerated ions into dense layers of the solar atmosphere in the sunspot, where a short-term reduction in the photospheric magnetic field by about 100 G was simultaneously observed. An idea is stated and justified for the first time that the local reduction in the magnetic field in the sunspot is caused by the diamagnetic effect created by accelerated ions in the magnetic mirror of the coronal magnetic flux rope above the sunspot.« less

Diffusion from a line source

NASA Technical Reports Server (NTRS)

Burns, R. E.

1973-01-01

The problem with predicting pollutant diffusion from a line source of arbitrary geometry is treated. The concentration at the line source may be arbitrarily varied with time. Special attention is given to the meteorological inputs which act as boundary conditions for the problem, and a mixing layer of arbitrary depth is assumed. Numerical application of the derived theory indicates the combinations of meteorological parameters that may be expected to result in high pollution concentrations.

Learning Scene Categories from High Resolution Satellite Image for Aerial Video Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheriyadat, Anil M

2011-01-01

Automatic scene categorization can benefit various aerial video processing applications. This paper addresses the problem of predicting the scene category from aerial video frames using a prior model learned from satellite imagery. We show that local and global features in the form of line statistics and 2-D power spectrum parameters respectively can characterize the aerial scene well. The line feature statistics and spatial frequency parameters are useful cues to distinguish between different urban scene categories. We learn the scene prediction model from highresolution satellite imagery to test the model on the Columbus Surrogate Unmanned Aerial Vehicle (CSUAV) dataset ollected bymore » high-altitude wide area UAV sensor platform. e compare the proposed features with the popular Scale nvariant Feature Transform (SIFT) features. Our experimental results show that proposed approach outperforms te SIFT model when the training and testing are conducted n disparate data sources.« less

An Archival Chandra and XMM-Newton Survey of Type 2 Quasars

NASA Technical Reports Server (NTRS)

Jia, Jianjun; Ptak, Andrew Francis; Heckman, Timothy; Zakamska, Nadia L.

2013-01-01

In order to investigate obscuration in high-luminosity type 2 active galactic nuclei (AGNs), we analyzed Chandra and XMM-Newton archival observations for 71 type 2 quasars detected at 0.05 < z < 0.73, which were selected based on their [O III] lambda5007 emission lines. For 54 objects with good spectral fits, the observed hard X-ray luminosity ranges from 2 × 10(exp 41) to 5.3 × 10(exp 44) erg s(exp -1), with a median of 1.1 × 10(exp 43) erg s(exp -1). We find that the means of the column density and photon index of our sample are log N(sub H) = 22.9 cm(exp -2) and gamma = 1.87, respectively. From simulations using a more physically realistic model, we find that the absorbing column density estimates based on simple power-law models significantly underestimate the actual absorption in approximately half of the sources. Eleven sources show a prominent Fe K alpha emission line (EW>100 eV in the rest frame) and we detect this line in the other sources through a joint fit (spectral stacking). The correlation between the Fe K alpha and [O III] fluxes and the inverse correlation of the equivalent width of the Fe Ka line with the ratio of hard X-ray and [O III] fluxes is consistent with previous results for lower luminosity Seyfert 2 galaxies. We conclude that obscuration is the cause of the weak hard X-ray emission rather than intrinsically low X-ray luminosities. We find that about half of the population of optically selected type 2 quasars are likely to be Compton thick. We also find no evidence that the amount of X-ray obscuration depends on the AGN luminosity (over a range of more than three orders of magnitude in luminosity).

IRAS 22150+6109 - a young B-type star with a large disc

NASA Astrophysics Data System (ADS)

Zakhozhay, Olga V.; Miroshnichenko, Anatoly S.; Kuratov, Kenesken S.; Zakhozhay, Vladimir A.; Khokhlov, Serik A.; Zharikov, Sergey V.; Manset, Nadine

2018-06-01

We present the results of a spectroscopic analysis and spectral energy distribution (SED) modelling of the optical counterpart of the infrared source IRAS 22150+6109. The source was suggested to be a Herbig Be star located in the star-forming region L 1188. Absorption lines in the optical spectrum indicate a spectral type B3, while weak Balmer emission lines reflect the presence of a circumstellar gaseous disc. The star shows no excess radiation in the near-infrared spectral region and a strong excess in the far-infrared that we interpret as radiation from a large disc, the inner edge of which is located very far from the star (550 au) and does not attenuate its radiation. We conclude that IRAS 22150+6109 is an intermediate-mass star that is currently undergoing a short pre-main-sequence evolutionary stage.

Evaluation of the Antimicrobial Functions of N-halamine Dental Unit Waterline Tubing for One Year.

PubMed

Porteous, N; Dang, S; Schoolfield, J; Sun, Y

2016-03-01

The objective of this study was to test the biofilm-controlling properties of N-halamine antimicrobial dental unit waterline (DUWL) tubing (T) tubing, without recharging over one year, compared to a control line (C). A simulated clinical model was used to pump ultrapure water through T and C lines at a rate of 1.4 mL/min, five minutes on, 15 minutes off, eight hours/day, five days a week. Samples of source water, effluent from T and C, and from the stagnant water in the carboy (liquid container) after bench work was completed (S2), were collected aseptically, serially diluted, and cultured on R2A agar for seven days every six weeks. SEM images of the inside surfaces of detached tubing sections were also taken. The carboy was rinsed with a 1:10 dilution of sodium hypochlorite after six months. Means of log transformed CFU values obtained in triplicate were paired by T and C lines across months for comparison by paired Student's t-tests. An increase in effluent and carboy bacterial counts were noted after six months, but decreased after bleach rinse of the carboy. No significant difference (p > 0.25) between T and C lines were observed; similarly, T and carboy were not significantly different (p > 0.30). SEM images showed biofilm attachment on the inside surface of C after two months, but not on T. Organisms identified in the effluent reflected those in the source carboy. No biofilm attachment was detected on the N-halamine test line after 12 months, indicating its antimicrobial properties were retained. Further evaluation is recommended to determine the optimal recharge interval for N-halamine DUWL tubing when ultrapure source water is used.

Evaluation of the Antimicrobial Functions of N-halamine Dental Unit Waterline Tubing for One Year

PubMed Central

Porteous, N.; Dang, S.; Schoolfield, J.; Sun, Y.

2017-01-01

Objective The objective of this study was to test the biofilm-controlling properties of N-halamine antimicrobial dental unit waterline (DUWL) tubing (T) tubing, without recharging over one year, compared to a control line (C). Methods A simulated clinical model was used to pump ultrapure water through T and C lines at a rate of 1.4 mL/min, five minutes on, 15 minutes off, eight hours/day, five days a week. Samples of source water, effluent from T and C, and from the stagnant water in the carboy (liquid container) after bench work was completed (S2), were collected aseptically, serially diluted, and cultured on R2A agar for seven days every six weeks. SEM images of the inside surfaces of detached tubing sections were also taken. The carboy was rinsed with a 1:10 dilution of sodium hypochlorite after six months. Means of log transformed CFU values obtained in triplicate were paired by T and C lines across months for comparison by paired Student’s t-tests. Results An increase in effluent and carboy bacterial counts were noted after six months, but decreased after bleach rinse of the carboy. No significant difference (p > 0.25) between T and C lines were observed; similarly, T and carboy were not significantly different (p > 0.30). SEM images showed biofilm attachment on the inside surface of C after two months, but not on T. Organisms identified in the effluent reflected those in the source carboy. Conclusions No biofilm attachment was detected on the N-halamine test line after 12 months, indicating its antimicrobial properties were retained. Further evaluation is recommended to determine the optimal recharge interval for N-halamine DUWL tubing when ultrapure source water is used. PMID:28390212

Temperature Dependence of Wavelength Selectable Zero-Phonon Emission from Single Defects in Hexagonal Boron Nitride.

PubMed

Jungwirth, Nicholas R; Calderon, Brian; Ji, Yanxin; Spencer, Michael G; Flatté, Michael E; Fuchs, Gregory D

2016-10-12

We investigate the distribution and temperature-dependent optical properties of sharp, zero-phonon emission from defect-based single photon sources in multilayer hexagonal boron nitride (h-BN) flakes. We observe sharp emission lines from optically active defects distributed across an energy range that exceeds 500 meV. Spectrally resolved photon-correlation measurements verify single photon emission, even when multiple emission lines are simultaneously excited within the same h-BN flake. We also present a detailed study of the temperature-dependent line width, spectral energy shift, and intensity for two different zero-phonon lines centered at 575 and 682 nm, which reveals a nearly identical temperature dependence despite a large difference in transition energy. Our temperature-dependent results are well described by a lattice vibration model that considers piezoelectric coupling to in-plane phonons. Finally, polarization spectroscopy measurements suggest that whereas the 575 nm emission line is directly excited by 532 nm excitation, the 682 nm line is excited indirectly.

The Formation and Physical Origin of Highly Ionized Cooling Gas

NASA Astrophysics Data System (ADS)

Bordoloi, Rongmon; Wagner, Alexander Y.; Heckman, Timothy M.; Norman, Colin A.

2017-10-01

We present a simple model that explains the origin of warm, diffuse gas seen primarily as highly ionized absorption-line systems in the spectra of background sources. We predict the observed column densities of several highly ionized transitions such as O VI, O vii, Ne viii, N v, and Mg x, and we present a unified comparison of the model predictions with absorption lines seen in the Milky Way disk, Milky Way halo, starburst galaxies, the circumgalactic medium, and the intergalactic medium at low and high redshifts. We show that diffuse gas seen in such diverse environments can be simultaneously explained by a simple model of radiatively cooling gas. We show that most such absorption-line systems are consistent with being collisionally ionized, and we estimate the maximum-likelihood temperature of the gas in each observation. This model satisfactorily explains why O VI is regularly observed around star-forming low-z L* galaxies, and why N v is rarely seen around the same galaxies. We further present some consequences of this model in quantifying the dynamics of the cooling gas around galaxies and predict the shock velocities associated with such flows. A unique strength of this model is that while it has only one free (but physically well-constrained) parameter, it nevertheless successfully reproduces the available data on O VI absorbers in the interstellar, circumgalactic, intragroup, and intergalactic media, as well as the available data on other absorption lines from highly ionized species.

The Formation and Physical Origin of Highly Ionized Cooling Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bordoloi, Rongmon; Wagner, Alexander Y.; Heckman, Timothy M.

We present a simple model that explains the origin of warm, diffuse gas seen primarily as highly ionized absorption-line systems in the spectra of background sources. We predict the observed column densities of several highly ionized transitions such as O vi, O vii, Ne viii, N v, and Mg x, and we present a unified comparison of the model predictions with absorption lines seen in the Milky Way disk, Milky Way halo, starburst galaxies, the circumgalactic medium, and the intergalactic medium at low and high redshifts. We show that diffuse gas seen in such diverse environments can be simultaneously explainedmore » by a simple model of radiatively cooling gas. We show that most such absorption-line systems are consistent with being collisionally ionized, and we estimate the maximum-likelihood temperature of the gas in each observation. This model satisfactorily explains why O vi is regularly observed around star-forming low- z L* galaxies, and why N v is rarely seen around the same galaxies. We further present some consequences of this model in quantifying the dynamics of the cooling gas around galaxies and predict the shock velocities associated with such flows. A unique strength of this model is that while it has only one free (but physically well-constrained) parameter, it nevertheless successfully reproduces the available data on O vi absorbers in the interstellar, circumgalactic, intragroup, and intergalactic media, as well as the available data on other absorption lines from highly ionized species.« less

Charge exchange in galaxy clusters

NASA Astrophysics Data System (ADS)

Gu, Liyi; Mao, Junjie; de Plaa, Jelle; Raassen, A. J. J.; Shah, Chintan; Kaastra, Jelle S.

2018-03-01

Context. Though theoretically expected, the charge exchange emission from galaxy clusters has never been confidently detected. Accumulating hints were reported recently, including a rather marginal detection with the Hitomi data of the Perseus cluster. As previously suggested, a detection of charge exchange line emission from galaxy clusters would not only impact the interpretation of the newly discovered 3.5 keV line, but also open up a new research topic on the interaction between hot and cold matter in clusters. Aim. We aim to perform the most systematic search for the O VIII charge exchange line in cluster spectra using the RGS on board XMM-Newton. Methods: We introduce a sample of 21 clusters observed with the RGS. In order to search for O VIII charge exchange, the sample selection criterion is a >35σ detection of the O VIII Lyα line in the archival RGS spectra. The dominating thermal plasma emission is modeled and subtracted with a two-temperature thermal component, and the residuals are stacked for the line search. The systematic uncertainties in the fits are quantified by refitting the spectra with a varying continuum and line broadening. Results: By the residual stacking, we do find a hint of a line-like feature at 14.82 Å, the characteristic wavelength expected for oxygen charge exchange. This feature has a marginal significance of 2.8σ, and the average equivalent width is 2.5 × 10-4 keV. We further demonstrate that the putative feature can be barely affected by the systematic errors from continuum modeling and instrumental effects, or the atomic uncertainties of the neighboring thermal lines. Conclusions: Assuming a realistic temperature and abundance pattern, the physical model implied by the possible oxygen line agrees well with the theoretical model proposed previously to explain the reported 3.5 keV line. If the charge exchange source indeed exists, we expect that the oxygen abundance could have been overestimated by 8-22% in previous X-ray measurements that assumed pure thermal lines. These new RGS results bring us one step forward to understanding the charge exchange phenomenon in galaxy clusters.

Let's Go Off the Grid: Subsurface Flow Modeling With Analytic Elements

NASA Astrophysics Data System (ADS)

Bakker, M.

2017-12-01

Subsurface flow modeling with analytic elements has the major advantage that no grid or time stepping are needed. Analytic element formulations exist for steady state and transient flow in layered aquifers and unsaturated flow in the vadose zone. Analytic element models are vector-based and consist of points, lines and curves that represent specific features in the subsurface. Recent advances allow for the simulation of partially penetrating wells and multi-aquifer wells, including skin effect and wellbore storage, horizontal wells of poly-line shape including skin effect, sharp changes in subsurface properties, and surface water features with leaky beds. Input files for analytic element models are simple, short and readable, and can easily be generated from, for example, GIS databases. Future plans include the incorporation of analytic element in parts of grid-based models where additional detail is needed. This presentation will give an overview of advanced flow features that can be modeled, many of which are implemented in free and open-source software.

Building a risk-targeted regional seismic hazard model for South-East Asia

NASA Astrophysics Data System (ADS)

Woessner, J.; Nyst, M.; Seyhan, E.

2015-12-01

The last decade has tragically shown the social and economic vulnerability of countries in South-East Asia to earthquake hazard and risk. While many disaster mitigation programs and initiatives to improve societal earthquake resilience are under way with the focus on saving lives and livelihoods, the risk management sector is challenged to develop appropriate models to cope with the economic consequences and impact on the insurance business. We present the source model and ground motions model components suitable for a South-East Asia earthquake risk model covering Indonesia, Malaysia, the Philippines and Indochine countries. The source model builds upon refined modelling approaches to characterize 1) seismic activity from geologic and geodetic data on crustal faults and 2) along the interface of subduction zones and within the slabs and 3) earthquakes not occurring on mapped fault structures. We elaborate on building a self-consistent rate model for the hazardous crustal fault systems (e.g. Sumatra fault zone, Philippine fault zone) as well as the subduction zones, showcase some characteristics and sensitivities due to existing uncertainties in the rate and hazard space using a well selected suite of ground motion prediction equations. Finally, we analyze the source model by quantifying the contribution by source type (e.g., subduction zone, crustal fault) to typical risk metrics (e.g.,return period losses, average annual loss) and reviewing their relative impact on various lines of businesses.

High-Resolution X-Ray Spectroscopy of the Seyfert 2 Galaxy Circinus with Chandra

NASA Technical Reports Server (NTRS)

Sambruna, Rita M.; Netzer, Hagai; Kaspi, Shai; Brandt, W. N.; Chartas, G.; Garmire, G. P.; Nousek, John A.; Weaver, K. A.

2000-01-01

Results from a 60 ks Chandra High Energy Transmission Grating Spectrometer (HETGS) observation of the nearby Seyfert 2 Circinus are presented. The spectrum shows a wealth of emission lines at both soft and hard X-rays, including lines of Ne, Mg, Si, S, Ar, Ca, and Fe, and a prominent Fe K(alpha) line at 6.4 keV. We identify several of the He-like components and measure several of the Lyman lines of the N-like ions. The lines' profiles are unresolved at the limited signal-to-noise ratio of the data. Our analysis of the zeroth-order image in a companion paper constrains the size of the emission region to be 20-60 pc, suggesting that emission within this volume is almost entirely due to the reprocessing of the obscured central source. Here we show that a model containing two distinct components can reproduce almost all the observed properties of this gas. The ionized component can explain the observed intensities of the ionized species, assuming twice-solar composition and an N is proportional r(exp -1.5) density distribution. The neutral component is highly concentrated, well within the 0.8" point source, and is responsible for almost all of the observed K(alpha) (6.4 keV) emission. Circinus seems to be different than Mkn 3 in terms of its gas distribution.

Sensitivity of the 6300 A twilight airglow to neutral composition

NASA Technical Reports Server (NTRS)

Melendez-Alvira, D. J.; Torr, D. G.; Richards, P. G.; Swift, W. R.; Torr, M. R.; Baldridge, T.; Rassoul, H.

1995-01-01

The field line interhemispheric plasma (FLIP) model is used to study the 6300 A line intensity measured during three morning twilights from the McDonald Observatory in Texas. The Imaging Spectrometric Observatory (ISO) measured the 6300 A intensity during the winter of 1987 and the spring and summer of 1988. The FLIP model reproduces the measured intensity and its variation through the twilight well on each day using neutral densities from the MSIS-86 empirical model. This is in spite of the fact that different component sources dominate the integrated volume emission rate on each of the days analyzed. The sensitivity of the intensity to neutral composition is computed by varying the N2, O2, and O densities in the FLIP model and comparing to the intensity computed with the unmodified MSIS-86 densities. The ion densities change self-consistently. Thus the change in neutral composition also changes the electron density. The F2 peak height is unchanged in the model runs for a given day. The intensity changes near 100 deg SZA are comparable to within 10% when either (O2), (N2), or (O) is changed, regardless of which component source is dominant. There is strong sensitivity to changes in (N2) when dissociative recombination is dominant, virtually no change in the nighttime (SZA greater than or equal to 108 deg) intensity with (O2) doubled, and sensitivity of over 50% to doubling or halving (O) at night. When excitation by conjugate photoelectrons is the dominant nighttime component source, the relative intensity change with (O) doubled or halved is very small. This study shows the strong need for simultaneous measurements of electron density and of emissions proportional to photoelectron fluxes if the 6300 A twilight airglow is to be used to retrieve neutral densities.

The Radio to Gamma-ray SED of the Narrow-line Seyfert 1 1H0323+342

NASA Astrophysics Data System (ADS)

Ward, M.

2017-10-01

A sub-set of radio-loud narrow line Seyfert 1s, have been detected in gamma-rays by the Fermi Gamma-Ray satellite. Their gamma-ray emission is thought to arise from a relativistic jet. We have obtained new near-infrared spectra and used the profiles of the Paschen lines to estimate the mass of the black hole. Combining this with results from optical lines and X-ray timing analysis we arrive at a value of 2 x 10**E7 solar masses. From modelling the broad-band SED, we drive an Eddington ratio of 0.5, rising to 1.0 for a spinning black hole (a=0.8). Furthermore, we constrain the external photon field, and use a single-zone leptonic jet model to obtain a range of jet-parameters which are consistent with Compton up-scattering to produce the observed gamma-ray spectrum. This low-redshift very well studied AGN can potentially provide a useful laboratory to further our understanding of the jet/disc connection in extragalactic sources.

2D-model of oxygen emissions lines for Europa

NASA Astrophysics Data System (ADS)

Cessateur, Gaël; Barthelemy, Mathieu; Lilensten, Jean; Rubin, Martin; Maggiolo, Romain; De Keyser, Johan

2017-04-01

The Jovian moon Europa is an interesting case study as an archetype for icy satellites, and will be one of the primary targets of the ESA JUICE mission which should be launched in 2022. Hosting a thin neutral gas atmosphere mainly composed of O2 and H2O, Europa can be studied by its airglow and dayglow emissions. A 1D photochemistry model has first been developed to assess the impact of the solar UV flux on the visible emission, such as the red and green oxygen lines (Cessateur et al. 2016). For limb polar viewing, red line emissions can reach a few hundreds of Rayleigh close to the surface. The impact of the precipitating electrons has also been studied. The density and temperature of the electrons are first derived from the multifluid MHD model from Rubin et al. (2015). A 2D emission model has thus been developed to estimate the airglow emissions. When electrons are the major source of the visible emissions, the solar UV flux can be responsible for up to 15% of those emissions for some specific line of sight. Oxygen emission lines in the UV have also been considered, such as 130.5 and 135.6 nm. For the latter, we did estimate some significant line emissions reaching 700 Rayleigh for a polar limb viewing angle close to the surface. Oxygen emission lines are significant (higher than 10 R) for altitudes lower than 100 km for all lines, except for the red line emissions where emissions are still above 10 R up to 200 km from the surface. A sensitivity study has also been performed in order to assess the impact of the uncertainties relative to the dissociative-excitation cross sections. Cessateur G, Barthelemy M & Peinke I. Photochemistry-emission coupled model for Europa and Ganymede. J. Space Weather Space Clim., 6, A17, 2016 Rubin, M., et al. Self-consistent multifluid MHD simulations of Europa's exospheric interaction with Jupiter's magnetosphere, J. Geophys. Res. Space Physics, 120, 3503-3524, 2015

SU-E-T-102: Determination of Dose Distributions and Water-Equivalence of MAGIC-F Polymer Gel for 60Co and 192Ir Brachytherapy Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quevedo, A; Nicolucci, P

2014-06-01

Purpose: Analyse the water-equivalence of MAGIC-f polymer gel for {sup 60}Co and {sup 192}Ir clinical brachytherapy sources, through dose distributions simulated with PENELOPE Monte Carlo code. Methods: The real geometry of {sup 60} (BEBIG, modelo Co0.A86) and {sup 192}192Ir (Varian, model GammaMed Plus) clinical brachytherapy sources were modelled on PENELOPE Monte Carlo simulation code. The most probable emission lines of photons were used for both sources: 17 emission lines for {sup 192}Ir and 12 lines for {sup 60}. The dose distributions were obtained in a cubic water or gel homogeneous phantom (30 × 30 × 30 cm{sup 3}), with themore » source positioned in the middle of the phantom. In all cases the number of simulation showers remained constant at 10{sup 9} particles. A specific material for gel was constructed in PENELOPE using weight fraction components of MAGIC-f: wH = 0,1062, wC = 0,0751, wN = 0,0139, wO = 0,8021, wS = 2,58×10{sup −6} e wCu = 5,08 × 10{sup −6}. The voxel size in the dose distributions was 0.6 mm. Dose distribution maps on the longitudinal and radial direction through the centre of the source were used to analyse the water-equivalence of MAGIC-f. Results: For the {sup 60} source, the maximum diferences in relative doses obtained in the gel and water were 0,65% and 1,90%, for radial and longitudinal direction, respectively. For {sup 192}Ir, the maximum difereces in relative doses were 0,30% and 1,05%, for radial and longitudinal direction, respectively. The materials equivalence can also be verified through the effective atomic number and density of each material: Zef-MAGIC-f = 7,07 e .MAGIC-f = 1,060 g/cm{sup 3} and Zef-water = 7,22. Conclusion: The results showed that MAGIC-f is water equivalent, consequently being suitable to simulate soft tissue, for Cobalt and Iridium energies. Hence, gel can be used as a dosimeter in clinical applications. Further investigation to its use in a clinical protocol is needed.« less

XTE Proposal #20102--"SS 433's High Energy Spectrum"

NASA Technical Reports Server (NTRS)

Band, David L.; Blanco, P.; Rothschild, R.; Kawai, N.; Kotani, T.; Oka, T.; Wagner, R. M.; Hjellming, R.; Rupen, M.; Brinkmann, W.

1999-01-01

We observed the jet-producing compact binary system SS 433 with RXTE during three multiwavelength campaigns, the first in conjunction with ASCA observations, the second simultaneous with a VLA-VLBA-MERLIN campaign, and the third associated with a Nobeyama millimeter-band campaign. All these campaigns included optical observations. Occurring at different jet precession and binary phases, the observations also monitored the system during a radio flare. The data provide SS 433's X-ray spectrum over more than an energy decade, and track the spectral variations as the X-ray source was partially eclipsed. The continuum can be modeled as a power law with an exponential cutoff, which can be detected to approximately 50 keV. Strong line emission is evident in the 5-10 keV range which can be modeled as a broad line whose energy is precession independent and a narrow line whose energy does vary with jet precession phase; this line model is clearly an over simplification since the PCA does not have sufficient energy resolution to detect the lines ASCA observed. The eclipses are deeper at high energy and at jet precession phases when the jets are more inclined towards and away from us. A large radio flare occurred between two sets of X-ray monitoring observations; an X-ray observation at the peak of the flare found a softer spectrum with a flux approximately 1/3 that of the quiescent level.

Weighted current sheets supported in normal and inverse configurations - A model for prominence observations

NASA Technical Reports Server (NTRS)

Demoulin, P.; Forbes, T. G.

1992-01-01

A technique which incorporates both photospheric and prominence magnetic field observations is used to analyze the magnetic support of solar prominences in two dimensions. The prominence is modeled by a mass-loaded current sheet which is supported against gravity by magnetic fields from a bipolar source in the photosphere and a massless line current in the corona. It is found that prominence support can be achieved in three different kinds of configurations: an arcade topology with a normal polarity; a helical topology with a normal polarity; and a helical topology with an inverse polarity. In all cases the important parameter is the variation of the horizontal component of the prominence field with height. Adding a line current external to the prominence eliminates the nonsupport problem which plagues virtually all previous prominence models with inverse polarity.

Nanoscale shift of the intensity distribution of dipole radiation.

PubMed

Shu, Jie; Li, Xin; Arnoldus, Henk F

2009-02-01

The energy flow lines (field lines of the Poynting vector) for radiation emitted by a dipole are in general curves, rather than straight lines. For a linear dipole the field lines are straight, but when the dipole moment of a source rotates, the field lines wind numerous times around an axis, which is perpendicular to the plane of rotation, before asymptotically approaching a straight line. We consider an elliptical dipole moment, representing the most general state of oscillation, and this includes the linear dipole as a special case. Due to the spiraling near the source, for the case of a rotating dipole moment, the field lines in the far field are displaced with respect to the outward radial direction, and this leads to a shift of the intensity distribution of the radiation in the far field. This shift is shown to be independent of the distance to the source and, although of nanoscale dimension, should be experimentally observable.

Heat Flow Contours and Well Data Around the Milford FORGE Site

DOE Data Explorer

Joe Moore

2016-03-09

This submission contains a shapefile of heat flow contour lines around the FORGE site located in Milford, Utah. The model was interpolated from data points in the Milford_wells shapefile. This heat flow model was interpolated from 66 data points using the kriging method in Geostatistical Analyst tool of ArcGIS. The resulting model was smoothed 100%. The well dataset contains 59 wells from various sources, with lat/long coordinates, temperature, quality, basement depth, and heat flow. This data was used to make models of the specific characteristics.

Seeing Through the Clouds: AGN Geometry with the Swift BAT Sample

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Urry, M.; Schawinski, K.; Koss, M. J.; Winter, L. M.; Elitzur, M.; Wilkin, W. H.

2011-01-01

We investigate the intrinsic structure of the clouds surrounding AGN which give rise to their X-ray and optical emission properties. Using a complete sample of Swift BAT AGN selected in hard X-rays (14-195 keV), which is unbiased with respect to obscuration and extinction, we compute the reddening in the broad line region along the line of sight to the nucleus of each source using Balmer decrement from the ratio of the broad components of H-alpha/H-beta. We compare reddening from dust in the broad line clouds to the hydrogen column density (NH) obtained from their X-ray spectra. The distribution of the gas-to-dust ratios over many lines of sight allow us to test models of AGN structure and probe the immediate environment of the accreting supermassive black holes.

The global reach of the 26 December 2004 Sumatra tsunami.

PubMed

Titov, Vasily; Rabinovich, Alexander B; Mofjeld, Harold O; Thomson, Richard E; González, Frank I

2005-09-23

Numerical model simulations, combined with tide-gauge and satellite altimetry data, reveal that wave amplitudes, directionality, and global propagation patterns of the 26 December 2004 Sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid-ocean ridge topographic waveguides.

The Application of Function Points to Predict Source Lines of Code for Software Development

DTIC Science & Technology

1992-09-01

there are some disadvantages. Software estimating tools are expensive. A single tool may cost more than $15,000 due to the high market value of the...term and Lang variables simultaneously onlN added marginal improvements over models with these terms included singularly. Using all the available

The stellar wind velocity function for red supergiants determined in eclipsing binaries

NASA Technical Reports Server (NTRS)

Ahmad, Imad A.; Stencel, Robert E.

1988-01-01

The potential for direct measurement of the acceleration of stellar winds from the supergiant component of Zeta Aurigae-type binary stars is discussed. The aberration angle of the interaction shock cone centered on the hot star provides a measure of the velocity of the cool star wind at the orbit of the secondary. This is confirmed by direct observations of stellar wind (P Cygni) line profile variations. This velocity is generally smaller than the final (terminal) velocity of the wind, deduced from the P Cygni line profiles. The contrast between these results and previously published supergiant wind models is discussed. The implication on the physics of energy source dissipation predicted in the theoretical models is considered.

NICER observations of MAXI J1820+070 suggest a rapidly-brightening black hole X-ray binary in the hard state

NASA Astrophysics Data System (ADS)

Uttley, P.; Gendreau, K.; Markwardt, C.; Strohmayer, T. E.; Bult, P.; Arzoumanian, Z.; Pottschmidt, K.; Ray, P. S.; Remillard, R.; Pasham, D.; Steiner, J.; Neilsen, J.; Homan, J.; Miller, J. M.; Iwakiri, W.; Fabian, A. C.

2018-03-01

NICER observed the new X-ray transient MAXI J1820+070 (ATel #11399, #11400, #11403, #11404, #11406, #11418, #11420, #11421) on multiple occasions from 2018 March 12 to 14. & nbsp;During this time the source brightened rapidly, from a total NICER mean count rate of 880 count/s on March 12 to 2800 count/s by March 14 17:00 & nbsp;UTC, corresponding to a change in 2-10 keV modelled flux (see below) from 1.9E-9 to 5E-9 erg cm-2 s-1. & nbsp; The broadband X-ray spectrum is absorbed by a low column density (fitting the model given below, we obtain 1.5E21 cm-2), in keeping with the low Galactic column in the direction of the source (ATel #11418; Dickey & Lockman, 1990, ARAA, 28, 215; Kalberla et al. 2005, A &A, 440, 775) and consists of a hard power-law component with weak reflection features (broad iron line and narrow 6.4 keV line core) and an additional soft X-ray component.

Strain broadening of the 1042-nm zero phonon line of the NV- center in diamond: A promising spectroscopic tool for defect tomography

NASA Astrophysics Data System (ADS)

Biktagirov, T. B.; Smirnov, A. N.; Davydov, V. Yu.; Doherty, M. W.; Alkauskas, A.; Gibson, B. C.; Soltamov, V. A.

2017-08-01

The negatively charged nitrogen-vacancy (NV-) center in diamond is a promising candidate for many quantum applications. Here, we examine the splitting and broadening of the center's infrared (IR) zero-phonon line (ZPL). We develop a model for these effects that accounts for the strain induced by photodependent microscopic distributions of defects. We apply this model to interpret observed variations of the IR ZPL shape with temperature and photoexcitation conditions. We identify an anomalous temperature-dependent broadening mechanism and that defects other than the substitutional nitrogen center significantly contribute to strain broadening. The former conclusion suggests the presence of a strong Jahn-Teller effect in the center's singlet levels and the latter indicates that major sources of broadening are yet to be identified. These conclusions have important implications for the understanding of the center and the engineering of diamond quantum devices. Finally, we propose that, once the major sources of broadening are identified, the IR ZPL has the potential to be a sensitive spectroscopic tool for probing microscopic strain fields and performing defect tomography.

Application of the Approximate Bayesian Computation methods in the stochastic estimation of atmospheric contamination parameters for mobile sources

NASA Astrophysics Data System (ADS)

Kopka, Piotr; Wawrzynczak, Anna; Borysiewicz, Mieczyslaw

2016-11-01

In this paper the Bayesian methodology, known as Approximate Bayesian Computation (ABC), is applied to the problem of the atmospheric contamination source identification. The algorithm input data are on-line arriving concentrations of the released substance registered by the distributed sensors network. This paper presents the Sequential ABC algorithm in detail and tests its efficiency in estimation of probabilistic distributions of atmospheric release parameters of a mobile contamination source. The developed algorithms are tested using the data from Over-Land Atmospheric Diffusion (OLAD) field tracer experiment. The paper demonstrates estimation of seven parameters characterizing the contamination source, i.e.: contamination source starting position (x,y), the direction of the motion of the source (d), its velocity (v), release rate (q), start time of release (ts) and its duration (td). The online-arriving new concentrations dynamically update the probability distributions of search parameters. The atmospheric dispersion Second-order Closure Integrated PUFF (SCIPUFF) Model is used as the forward model to predict the concentrations at the sensors locations.

An Outburst Scenario for the X-ray Spectral Variability in 3C 111

NASA Technical Reports Server (NTRS)

Tombesi, Francesco; Reeves, J. N.; Reynolds, Christopher S.; Garcia, J.; Lohfink, A.

2013-01-01

We present a combined Suzaku and Swift BAT broad-band E=0.6-200 keV spectral analysis of three 3C 111 observations obtained in 2010. The data are well described with an absorbed power-law continuum and a weak (R approximately equal to 0.2) cold reflection component from distant material. We constrain the continuum cutoff at E(sub C) approximately equal to 150- 200 keV, which is in accordance with X-ray Comptonization corona models and supports claims that the jet emission is only dominant at much higher energies. Fe XXVI Ly alpha emission and absorption lines are also present in the first and second observations, respectively. The modelling and interpretation of the emission line is complex and we explore three possibilities. If originating from ionized disc reflection, this should be emitted at r(sub in) greater than or equal to 50 r(sub g) or, in the lamp-post configuration, the illuminating source should be at a height of h greater than or equal to 30 r(sub g) over the black hole. Alternatively, the line could be modeled with a hot collisionally ionized plasma with temperature kT = 22.0(sup +6.1)(sub -3.2) keV or a photo-ionized plasma with logXi=4.52(sup +0.10)(sub -0.16) erg per second cm, and column density N(sub H) greater than 3×10(sup 23) per square centimeter. However, the first and second scenarios are less favored on statistical and physical grounds, respectively. The blue-shifted absorption line in the second observation can be modelled as an ultra-fast outflow (UFO) with ionization parameter logXi=4.47(sup +0.76) (sub -0.04) erg per second cm, column density NH=(5.3(sup +1.8)(sub -1.3))×10(sup 22) per square centimeter and outflow velocity v(sub out) = 0.104+/-0.006c. Interestingly, the parameters of the photoionized emission model remarkably match those of the absorbing UFO, supporting the possibility that the same material could be responsible for both emission and absorption. We suggest an outburst scenario in which an accretion disc wind, initially lying out of the line of sight and observed in emission, then crosses our view to the source and it is observed in absorption as a mildly-relativistic UFO.

The unusual N IV] -emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z = 5.56

NASA Astrophysics Data System (ADS)

Vanzella, E.; Grazian, A.; Hayes, M.; Pentericci, L.; Schaerer, D.; Dickinson, M.; Cristiani, S.; Giavalisco, M.; Verhamme, A.; Nonino, M.; Rosati, P.

2010-04-01

Aims: We investigate the nature of the source GDS J033218.92-275302.7 at redshift ~5.56. Methods: The spectral energy distribution of the source is well-sampled by 16 bands photometry from UV-optical (HST and VLT), near infrared, near infrared (VLT) to mid-infrared (Spitzer). The detection of a signal in the mid-infrared Spitzer/IRAC bands 5.8, 8.0 μm - where the nebular emission contribution is less effective - suggests that there is a Balmer break, the signature of an underlying stellar population formed at earlier epochs. The high-quality VLT/FORS2 spectrum shows a clear Lyα emission line, together with semi-forbidden N iv] 1483.3-1486.5 also in emission. These lines imply a young stellar population. In particular, the N iv] 1483.3-1486.5 feature (if the source is not hosting an AGN) is a signature of massive and hot stars with an associated nebular emission. Conversely, it may be a signature of an AGN. The observed SED and the Lyα emission line profile were modeled carefully to investigate the internal properties of the source. Results: From the SED-fitting with a single and a double stellar population and from the Lyα modeling, it turns out that the source seems to have an evolved component with a stellar mass of ~5 × 1010 M⊙ and age ~0.4 Gyr, and a young component with an age of ~0.01 Gyr and star formation rate in the range of 30-200 M⊙ yr-1. The limits on the effective radius derived from the ACS/z850 and VLT/Ks bands indicate that this galaxy is denser than the local ones with similar mass. A relatively high nebular gas column density is favored from the Lyα line modeling (NHI ⪆ 1021 cm-2). A vigorous outflow (~ 450 km s-1) has been measured from the optical spectrum, consistent with the Lyα modeling. From ACS observations it turns out that the region emitting Lyα photons is spatially compact and has a similar effective radius (~0.1 kpc physical) estimated at the ~1400 Å rest-frame wavelength, whose emission is dominated by the stellar continuum and/or AGN. The gas is blown out from the central region, but, given the mass of the galaxy, it is uncertain whether it will pollute the IGM to large distances. We argue that a burst of star formation in a dense gas environment is active (possibly containing hot and massive stars and/or a low luminosity AGN), superimposed on an already formed fraction of stellar mass. Based on observations made at the European Southern Observatory, Paranal, Chile (ESO program 170.A-0788 The Great Observatories Origins Deep Survey: ESO Public Observations of the SIRTF Legacy/HST Treasury/Chandra Deep Field South).

SP Response to a Line Source Infiltration for Characterizing the Vadose Zone: Forward Modeling and Inversion

NASA Astrophysics Data System (ADS)

Sailhac, P.

2004-05-01

Field estimation of soil water flux has direct application for water resource management. Standard hydrologic methods like tensiometry or TDR are often difficult to apply because of the heterogeneity of the subsurface, and non invasive tools like ERT, NMR or GPR are limited to the estimation of the water content. Electrical Streaming Potential (SP) monitoring can provide a cost-effective tool to help estimate the nature of the hydraulic transfers (infiltration or evaporation) in the vadose zone. Indeed this technique has improved during the last decade and has been shown to be a useful tool for quantitative groundwater flow characterization (see the poster of Marquis et al. for a review). We now account for our latest development on the possibility of using SP for estimating hydraulic parameters of unsaturated soils from in situ SP measurements during infiltration experiments. The proposed method consists in SP profiling perpendicularly to a line source of steady-state infiltration. Analytic expressions for the forward modeling show a sensitivity to six parameters: the electrokinetic coupling parameter at saturation CS, the soil sorptive number α , the ratio of the constant source strength to the hydraulic conductivity at saturation q/KS, the soil effective water saturation prior to the infiltration experiment Se0, Mualem parameter m, and Archie law exponent n. In applications, all these parameters could be constrained by inverting electrokinetic data obtained during a series of infiltration experiments with varying source strength q.

Simulating wind and marine hydrokinetic turbines with actuator lines in RANS and LES

NASA Astrophysics Data System (ADS)

Bachant, Peter; Wosnik, Martin

2015-11-01

As wind and marine hydrokinetic (MHK) turbine designs mature, focus is shifting towards improving turbine array layouts for maximizing overall power output, i.e., minimizing wake interference for axial-flow or horizontal-axis turbines, or taking advantage of constructive wake interaction for cross-flow or vertical-axis turbines. Towards this goal, an actuator line model (ALM) was developed to provide a computationally feasible method for simulating full turbine arrays inside Navier-Stokes models. The ALM predicts turbine loading with the blade element method combined with sub-models for dynamic stall and flow curvature. The open-source software is written as an extension library for the OpenFOAM CFD package, which allows the ALM body force to be applied to their standard RANS and LES solvers. Turbine forcing is also applied to volume of fluid (VOF) models, e.g., for predicting free surface effects on submerged MHK devices. An additional sub-model is considered for injecting turbulence model scalar quantities based on actuator line element loading. Results are presented for the simulation of performance and wake dynamics of axial- and cross-flow turbines and compared with moderate Reynolds number experiments and body-fitted mesh, blade-resolving CFD. Work supported by NSF-CBET grant 1150797.

IC 3639 - A New Bona Fide Compton-Thick AGN Unveiled By NuSTAR

NASA Technical Reports Server (NTRS)

Boorman, Peter G.; Gandhi, P.; Alexander, D. M.; Annuar, A.; Ballantyne, D. R.; Bauer, F.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.;

The Orion Fingers: H2 Temperatures and Excitation in an Explosive Outflow

NASA Astrophysics Data System (ADS)

Youngblood, Allison; France, Kevin; Ginsburg, Adam; Hoadley, Keri; Bally, John

2018-04-01

We measure H2 temperatures and column densities across the Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) explosive outflow from a set of 13 near-infrared (IR) H2 rovibrational emission lines observed with the TripleSpec spectrograph on Apache Point Observatory’s 3.5 m telescope. We find that most of the region is well characterized by a single temperature (∼2000–2500 K), which may be influenced by the limited range of upper-energy levels (6000–20,000 K) probed by our data set. The H2 column density maps indicate that warm H2 comprises 10‑5–10‑3 of the total H2 column density near the center of the outflow. Combining column density measurements for co-spatial H2 and CO at T = 2500 K, we measure a CO/H2 fractional abundance of 2 × 10‑3 and discuss possible reasons why this value is in excess of the canonical 10‑4 value, including dust attenuation, incorrect assumptions on co-spatiality of the H2 and CO emission, and chemical processing in an extreme environment. We model the radiative transfer of H2 in this region with ultraviolet (UV) pumping models to look for signatures of H2 fluorescence from H I Lyα pumping. Dissociative (J-type) shocks and nebular emission from the foreground Orion H II region are considered as possible Lyα sources. From our radiative transfer models, we predict that signatures of Lyα pumping should be detectable in near-IR line ratios given a sufficiently strong source, but such a source is not present in the BN/KL outflow. The data are consistent with shocks as the H2 heating source.

The 2.5-dimensional equivalent sources method for directly exposed and shielded urban canyons.

PubMed

Hornikx, Maarten; Forssén, Jens

2007-11-01

When a domain in outdoor acoustics is invariant in one direction, an inverse Fourier transform can be used to transform solutions of the two-dimensional Helmholtz equation to a solution of the three-dimensional Helmholtz equation for arbitrary source and observer positions, thereby reducing the computational costs. This previously published approach [D. Duhamel, J. Sound Vib. 197, 547-571 (1996)] is called a 2.5-dimensional method and has here been extended to the urban geometry of parallel canyons, thereby using the equivalent sources method to generate the two-dimensional solutions. No atmospheric effects are considered. To keep the error arising from the transform small, two-dimensional solutions with a very fine frequency resolution are necessary due to the multiple reflections in the canyons. Using the transform, the solution for an incoherent line source can be obtained much more efficiently than by using the three-dimensional solution. It is shown that the use of a coherent line source for shielded urban canyon observer positions leads mostly to an overprediction of levels and can yield erroneous results for noise abatement schemes. Moreover, the importance of multiple facade reflections in shielded urban areas is emphasized by vehicle pass-by calculations, where cases with absorptive and diffusive surfaces have been modeled.

Thermo-hydraulics of the Peruvian accretionary complex at 12°S

USGS Publications Warehouse

Kukowski, Nina; Pecher, Ingo

1999-01-01

The models were constrained by the thermal gradient obtained from the depth of bottomsimulating reflectors (BSRs) at the lower slope and some conventional measurements. We foundthat significant frictional heating is required to explain the observed strong landward increase ofheat flux. This is consistent with results from sandbox modelling which predict strong basalfriction at this margin. A significantly higher heat source is needed to match the observed thermalgradient in the southern line.

Relationship Between the Electromagnetic Wave Energy Coupled by Overhead Lines and the Radiation Source Current Explored in the Laboratory

NASA Astrophysics Data System (ADS)

Li, Xiangchao; Wan, Zhicheng

2018-04-01

In order to solve the damage and interference problems to the electronic devices, which are induced by overvoltage excited by the coupling process between lightning electromagnetic wave and overhead lines, the lightning channel is set to be equivalent to a radiant wire antenna. Based on the integration model of lightning return stroke channel, transmission line, and ground, we take advantage of the derived formula gotten from the transmission line model. By combing the theoretical and experimental methods, we conduct a comparative analysis on the coupling process between natural/simulated lightning and overhead line. Besides, we also calculate the amplitude and energy of overvoltage, which is caused by the coupling process between lightning electromagnetic wave and overhead lines. Upon these experimental results, we can draw several conclusions as follows: when the amplitude of the lightning current in the channel is between 5 kA and 41 kA, it takes on an excellent linear relation between the amplitude of overvoltage and the magnitude of the lightning current, the relation between coupling energy and magnitude of the lightning current takes on an exponential trend. When lightning wave transmits on the transmission lines, the high-order mode will be excited. Through analysis on the high-order mode's characteristics, we find that the theoretical analysis is consistent with the experimental results, which has a certain reference value to the protection on overhead lines.

Tapping the grapevine: a closer look at word-of-mouth as a recruitment source.

PubMed

Van Hoye, Greet; Lievens, Filip

2009-03-01

To advance knowledge of word-of-mouth as a company-independent recruitment source, this study draws on conceptualizations of word-of-mouth in the marketing literature. The sample consisted of 612 potential applicants targeted by the Belgian Defense. Consistent with the recipient-source framework, time spent receiving positive word-of-mouth was determined by the traits of the recipient (extraversion and conscientiousness), the characteristics of the source (perceived expertise), and their mutual relationship (tie strength). Only conscientiousness and source expertise were determinants of receiving negative word-of-mouth. In line with the accessibility-diagnosticity model, receiving positive employment information through word-of-mouth early in the recruitment process was positively associated with perceptual (organizational attractiveness) and behavioral outcomes (actual application decisions), beyond potential applicants' exposure to other recruitment sources. (c) 2009 APA, all rights reserved.

TIME STRUCTURE OF GAMMA-RAY SIGNALS GENERATED IN LINE-OF-SIGHT INTERACTIONS OF COSMIC RAYS FROM DISTANT BLAZARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prosekin, Anton; Aharonian, Felix; Essey, Warren

2012-10-01

Blazars are expected to produce both gamma rays and cosmic rays. Therefore, observed high-energy gamma rays from distant blazars may contain a significant contribution from secondary gamma rays produced along the line of sight by the interactions of cosmic-ray protons with background photons. Unlike the standard models of blazars that consider only the primary photons emitted at the source, models that include the cosmic-ray contribution predict that even {approx}10 TeV photons should be detectable from distant objects with redshifts as high as z {>=} 0.1. Secondary photons contribute to signals of point sources only if the intergalactic magnetic fields aremore » very small, B {approx}< 10{sup -14} G, and their detection can be used to set upper bounds on magnetic fields along the line of sight. Secondary gamma rays have distinct spectral and temporal features. We explore the temporal properties of such signals using a semi-analytical formalism and detailed numerical simulations, which account for all the relevant processes, including magnetic deflections. In particular, we elucidate the interplay of time delays coming from the proton deflections and from the electromagnetic cascade, and we find that, at multi-TeV energies, secondary gamma rays can show variability on timescales of years for B {approx} 10{sup -15} G.« less

Line plus arc source trajectories and their R-line coverage for long-object cone-beam imaging with a C-arm system

NASA Astrophysics Data System (ADS)

Yu, Zhicong; Wunderlich, Adam; Dennerlein, Frank; Lauritsch, Günter; Noo, Frédéric

2011-06-01

Cone-beam imaging with C-arm systems has become a valuable tool in interventional radiology. Currently, a simple circular trajectory is used, but future applications should use more sophisticated source trajectories, not only to avoid cone-beam artifacts but also to allow extended volume imaging. One attractive strategy to achieve these two goals is to use a source trajectory that consists of two parallel circular arcs connected by a line segment, possibly with repetition. In this work, we address the question of R-line coverage for such a trajectory. More specifically, we examine to what extent R-lines for such a trajectory cover a central cylindrical region of interest (ROI). An R-line is a line segment connecting any two points on the source trajectory. Knowledge of R-line coverage is crucial because a general theory for theoretically exact and stable image reconstruction from axially truncated data is only known for the points in the scanned object that lie on R-lines. Our analysis starts by examining the R-line coverage for the elemental trajectories consisting of (i) two parallel circular arcs and (ii) a circular arc connected orthogonally to a line segment. Next, we utilize our understanding of the R-lines for the aforementioned elemental trajectories to determine the R-line coverage for the trajectory consisting of two parallel circular arcs connected by a tightly fit line segment. For this trajectory, we find that the R-line coverage is insufficient to completely cover any central ROI. Because extension of the line segment beyond the circular arcs helps to increase the R-line coverage, we subsequently propose a trajectory composed of two parallel circular arcs connected by an extended line. We show that the R-lines for this trajectory can fully cover a central ROI if the line extension is long enough. Our presentation includes a formula for the minimum line extension needed to achieve full R-line coverage of an ROI with a specified size, and also includes a preliminary study on the required detector size, showing that the R-lines added by the line extension are not constraining.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murray, S. G.; Trott, C. M.; Jordan, C. H.

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions formore » the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.« less

Phase 3 experiments of the JAERI/USDOE collaborative program on fusion blanket neutronics. Volume 1: Experiment

NASA Astrophysics Data System (ADS)

Oyama, Yukio; Konno, Chikara; Ikeda, Yujiro; Maekawa, Fujio; Kosako, Kazuaki; Nakamura, Tomoo; Maekawa, Hiroshi; Youssef, Mahmoud Z.; Kumar, Anil; Abdou, Mohamed A.

1994-02-01

A pseudo-line source has been realized by using an accelerator based D-T point neutron source. The pseudo-line source is obtained by time averaging of continuously moving point source or by superposition of finely distributed point sources. The line source is utilized for fusion blanket neutronics experiments with an annular geometry so as to simulate a part of a tokamak reactor. The source neutron characteristics were measured for two operational modes for the line source, continuous and step-wide modes, with the activation foil and the NE213 detectors, respectively. In order to give a source condition for a successive calculational analysis on the annular blanket experiment, the neutron source characteristics was calculated by a Monte Carlo code. The reliability of the Monte Carlo calculation was confirmed by comparison with the measured source characteristics. The shape of the annular blanket system was a rectangular with an inner cavity. The annular blanket was consist of 15 mm-thick first wall (SS304) and 406 mm-thick breeder zone with Li2O at inside and Li2CO3 at outside. The line source was produced at the center of the inner cavity by moving the annular blanket system in the span of 2 m. Three annular blanket configurations were examined; the reference blanket, the blanket covered with 25 mm thick graphite armor and the armor-blanket with a large opening. The neutronics parameters of tritium production rate, neutron spectrum and activation reaction rate were measured with specially developed techniques such as multi-detector data acquisition system, spectrum weighting function method and ramp controlled high voltage system. The present experiment provides unique data for a higher step of benchmark to test a reliability of neutronics design calculation for a realistic tokamak reactor.

No Compton Reflection In a Chandra/RXTE Observation of Mkn 509: Implications for the Fe-K Line Emission From Accreting X-Ray Sources

NASA Technical Reports Server (NTRS)

Yaqoob, Tahir; Padmanabhan, Urmila; Kraemer, Steven B.; Crenshaw, D. Michael; Mckernan, Barry; George, Ian M.; Turner, T. Jane; White, Nicholas E. (Technical Monitor)

2002-01-01

We report the results of simultaneous Chandra and RXTE observations of the Seyfert 1 galaxy Mkn 509. We deconvolve the broad and narrow Fe-K emission-line components for which we measure rest-frame equivalent widths of 119+/-18 eV and 57+/-13 eV respectively. The broad line has a FWHM of 57,600((sup 14,400)(sub -21,000)) km/s and the narrow line is unresolved, with an upper limit on the FWHM of 4,940 km/s. Both components must originate in cool matter since we measure rest-frame center energies of 6.36((sup +0.13)(sub -0.12)) keV and 6.42+/-0.01 keV for the broad and narrow line respectively. This rules out He-like and H-like Fe for the origin of both the broad and narrow lines. If, as is widely accepted, the broad Fe-K line originates in Thomson-thick matter (such as an accretion disk), then one expects to observe spectral curvature above approximately 10 keV, (commensurate with the observed broad line), characteristic of the Compton-reflection continuum. However our data sets very stringent limits on deviations of the observed continuum from a power law. Light travel-time delays cannot be invoked to explain anomalies in the relative strengths of the broad Ferry line and Compton-reflection continuum since they are supposed to originate in the same physical location. We are forced to conclude that both the broad and narrow Fe-K lines had to originate in Thomson-thin matter during our observation. This result, for a single observation of just one source, means that our understanding of Fe K line emission and Compton reflection from accreting X-ray sources in general needs to be re-examined. For example, if an irradiated accretion disk existed in Mkn 509 at the time of the observations, the lack of spectral curvature above approximately 10 keV suggests two possibilities. Either the disk was Thomson-thick and highly ionized, having negligible Fe-K line emission and photoelectric absorption or the disk was Thomson-thin producing some or all of the broad Fe-K line emission. In the former case, the broad Fe-K line had to have produced in a Thomson-thin region elsewhere. In both cases the predicted spectral curvature above approximately 10 keV is negligible. An additional implication of our results is that any putative obscuring torus in the system, required by unification models of active galaxies, must also be Thomson-thin. The same applies to the optical broad line region (BLR) if it has a substantial covering factor.

Space-charge compensation measurements in electron cyclotron resonance ion source low energy beam transport lines with a retarding field analyzer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winklehner, D.; Leitner, D., E-mail: leitnerd@nscl.msu.edu; Cole, D.

2014-02-15

In this paper we describe the first systematic measurement of beam neutralization (space charge compensation) in the ECR low energy transport line with a retarding field analyzer, which can be used to measure the potential of the beam. Expected trends for the space charge compensation levels such as increase with residual gas pressure, beam current, and beam density could be observed. However, the overall levels of neutralization are consistently low (<60%). The results and the processes involved for neutralizing ion beams are discussed for conditions typical for ECR injector beam lines. The results are compared to a simple theoretical beammore » plasma model as well as simulations.« less

Constraints on the explosion mechanism and progenitors of Type Ia supernovae

NASA Astrophysics Data System (ADS)

Dessart, Luc; Blondin, Stéphane; Hillier, D. John; Khokhlov, Alexei

2014-06-01

Observations of SN 2011fe at early times reveal an evolution analogous to a fireball model of constant colour. In contrast, our unmixed delayed detonations of Chandrasekhar-mass white dwarfs (DDC series) exhibit a faster brightening concomitant with a shift in colour to the blue. In this paper, we study the origin of these discrepancies. We find that strong chemical mixing largely resolves the photometric mismatch at early times, but it leads to an enhanced line broadening that contrasts, for example, with the markedly narrow Si II 6355 Å line of SN 2011fe. We also explore an alternative configuration with pulsational-delayed detonations (PDDEL model series). Because of the pulsation, PDDEL models retain more unburnt carbon, have little mass at high velocity, and have a much hotter outer ejecta after the explosion. The pulsation does not influence the inner ejecta, so PDDEL and DDC models exhibit similar radiative properties beyond maximum. However, at early times, PDDEL models show bluer optical colours and a higher luminosity, even for weak mixing. Their early-time radiation is derived primarily from the initial shock-deposited energy in the outer ejecta rather than radioactive-decay heating. Furthermore, PDDEL models show short-lived C II lines, reminiscent of SN 2013dy. They typically exhibit lines that are weaker, narrower, and of near-constant width, reminiscent of SN 2011fe. In addition to multidimensional effects, varying configurations for such `pulsations' offer a source of spectral diversity amongst Type Ia supernovae (SNe Ia). PDDEL and DDC models also provide one explanation for low- and high-velocity-gradient SNe Ia.

Modelling the Time Dependence of Frequency Content of Long-period Volcanic Earthquakes

NASA Astrophysics Data System (ADS)

Jousset, P.; Neuberg, J. W.

2001-12-01

Broad-band seismic networks provide a powerfull tool for the observation and analysis of volcanic earthquakes. The amplitude spectrogram allows us to follow the frequency content of these signals with time. Observed amplitude spectrograms of long-period volcanic earthquakes display distinct spectral lines sometimes varying by several Hertz over time spans of minutes to hours. We first present several examples associated with various phases of volcanic activity at Soufrière Hills volcano, Montserrat. Then, we present and discuss two mechanisms to explain such frequency changes in the spectrograms: (i) change of physical properties within the magma and, (ii) change in the triggering frequency of repeated sources within the conduit. We use 2D and 3D finite-difference modelling methods to compute the propagation of seismic waves in simplified volcanic structures: (i) we model the gliding spectral lines by introducing continuously changing magma properties during the wavefield computation; (ii) we explore the resulting pressure distribution within the conduit and its potential role in triggering further events. We obtain constraints on both amplitude and time-scales for changes of magma properties that are required to model gliding lines in amplitude spectrograms.

SDSS J211852.96-073227.5: a new γ-ray flaring narrow-line Seyfert 1 galaxy

NASA Astrophysics Data System (ADS)

Yang, Hui; Yuan, Weimin; Yao, Su; Li, Ye; Zhang, Jin; Zhou, Hongyan; Komossa, S.; Liu, He-Yang; Jin, Chichuan

2018-07-01

We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J211852.96-073227.5 (hereinafter J2118-0732). The galaxy, at a redshift of 0.26, is associated with a radio source of flat/inverted spectrum at high radio frequencies. The analysis of its optical spectrum obtained in the Sloan Digital Sky Survey (SDSS) revealed a small linewidth of the broad component of the Hβ line (full width at half-maximum = 1585 km s-1), making it a radio-loud NLS1 galaxy - an intriguing class of active galactic nuclei with exceptional multiwavelength properties. A new γ-ray source centred at J2118-0732 was sporadically detected during 2009-2013 in form of flares by the Fermi-LAT. Our XMM-Newton observations revealed a flat X-ray spectrum described by a simple power law, and a flux variation by a factor of ˜2.5 in five months. The source also shows intraday variability in the infrared band. Its broad-band spectral energy distribution can be modelled by emission from a simple one-zone leptonic jet model, and the flux drop from infrared to X-rays in five months can be explained by changes of the jet parameters, though the exact values may be subject to relatively large uncertainties. With the NLS1-blazar composite nucleus, the clear detection of the host galaxy, and the synchronous variations in the multiwavelength fluxes, J2118-0732 provides a new perspective on the formation and evolution of relativistic jets under the regime of relatively small black hole masses and high accretion rates.

SDSS J211852.96-073227.5: a new γ-ray flaring narrow-line Seyfert 1 galaxy

NASA Astrophysics Data System (ADS)

Yang, Hui; Yuan, Weimin; Yao, Su; Li, Ye; Zhang, Jin; Zhou, Hongyan; Komossa, S.; Liu, He-Yang; Jin, Chichuan

2018-04-01

We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J211852.96-073227.5 (hereafter J2118-0732). The galaxy, at a redshift of 0.26, is associated with a radio source of flat/inverted spectrum at high radio frequencies. The analysis of its optical spectrum obtained in the Sloan Digital Sky Survey revealed a small linewidth of the broad component of the Hβ line (FWHM = 1585 km s-1), making it a radio-loud NLS1 galaxy - an intriguing class of active galactic nuclei with exceptional multi-wavelength properties. A new γ-ray source centred at J2118-0732 was sporadically detected during 2009-2013 in form of flares by the Fermi-LAT. Our XMM-Newton observations revealed a flat X-ray spectrum described by a simple power law, and a flux variation by a factor of ˜2.5 in 5 months. The source also shows intraday variability in the infrared band. Its broad-band spectral energy distribution can be modelled by emission from a simple one-zone leptonic jet model, and the flux drop from infrared to X-rays in five months can be explained by changes of the jet parameters, though the exact values may be subject to relatively large uncertainties. With the NLS1-blazar composite nucleus, the clear detection of the host galaxy and the synchronous variations in the multi-wavelength fluxes, J2118-0732 provides a new perspective on the formation and evolution of relativistic jets under the regime of relatively small black hole masses and high accretion rates.

Maize aflatoxin accumulation segregates with early maturing selections from an S2 breeding cross population.

PubMed

Henry, W Brien

2013-01-15

Maize breeders continue to seek new sources of aflatoxin resistance, but most lines identified as resistance sources are late maturing. The vast difference in flowering time makes it hard to cross these lines with proprietary commercial lines that mature much earlier and often subjects the reproductive phase of these resistant lines to the hottest and driest portion of the summer, making silking, pollination and grain fill challenging. Two hundred crosses from the GEM Project were screened for aflatoxin accumulation at Mississippi State in 2008, and a subset of these lines were screened again in 2009. The breeding cross UR13085:S99g99u was identified as a potential source of aflatoxin resistance, and maturity-based selections were made from an S2 breeding population from this same germplasm source: UR13085:S99g99u-B-B. The earliest maturing selections performed poorly for aflatoxin accumulation, but later maturing selections were identified with favorable levels of aflatoxin accumulation. These selections, while designated as "late" within this study, matured earlier than most aflatoxin resistant lines presently available to breeders. Two selections from this study, designated S5_L7 and S5_L8, are potential sources of aflatoxin resistance and will be advanced for line development and additional aflatoxin screening over more site years and environments.

33 CFR 183.410 - Ignition protection.

Code of Federal Regulations, 2010 CFR

2010-07-01

... both vertically and horizontally the distance of the open space between the fuel source and the... sources, such as engines, and valves, connections, or other fittings in vent lines, fill lines... component is isolated from a gasoline fuel source if: (1) A bulkhead that meets the requirements of...

Comparison of a Rat Primary Cell-Based Blood-Brain Barrier Model With Epithelial and Brain Endothelial Cell Lines: Gene Expression and Drug Transport.

PubMed

Veszelka, Szilvia; Tóth, András; Walter, Fruzsina R; Tóth, Andrea E; Gróf, Ilona; Mészáros, Mária; Bocsik, Alexandra; Hellinger, Éva; Vastag, Monika; Rákhely, Gábor; Deli, Mária A

2018-01-01

Cell culture-based blood-brain barrier (BBB) models are useful tools for screening of CNS drug candidates. Cell sources for BBB models include primary brain endothelial cells or immortalized brain endothelial cell lines. Despite their well-known differences, epithelial cell lines are also used as surrogate models for testing neuropharmaceuticals. The aim of the present study was to compare the expression of selected BBB related genes including tight junction proteins, solute carriers (SLC), ABC transporters, metabolic enzymes and to describe the paracellular properties of nine different culture models. To establish a primary BBB model rat brain capillary endothelial cells were co-cultured with rat pericytes and astrocytes (EPA). As other BBB and surrogate models four brain endothelial cells lines, rat GP8 and RBE4 cells, and human hCMEC/D3 cells with or without lithium treatment (D3 and D3L), and four epithelial cell lines, native human intestinal Caco-2 and high P-glycoprotein expressing vinblastine-selected VB-Caco-2 cells, native MDCK and MDR1 transfected MDCK canine kidney cells were used. To test transporter functionality, the permeability of 12 molecules, glucopyranose, valproate, baclofen, gabapentin, probenecid, salicylate, rosuvastatin, pravastatin, atorvastatin, tacrine, donepezil, was also measured in the EPA and epithelial models. Among the junctional protein genes, the expression level of occludin was high in all models except the GP8 and RBE4 cells, and each model expressed a unique claudin pattern. Major BBB efflux (P-glycoprotein or ABCB1) and influx transporters (GLUT-1, LAT-1) were present in all models at mRNA levels. The transcript of BCRP (ABCG2) was not expressed in MDCK, GP8 and RBE4 cells. The absence of gene expression of important BBB efflux and influx transporters BCRP, MRP6, -9, MCT6, -8, PHT2, OATPs in one or both types of epithelial models suggests that Caco-2 or MDCK models are not suitable to test drug candidates which are substrates of these transporters. Brain endothelial cell lines GP8, RBE4, D3 and D3L did not form a restrictive paracellular barrier necessary for screening small molecular weight pharmacons. Therefore, among the tested culture models, the primary cell-based EPA model is suitable for the functional analysis of the BBB.

Outburst of GX304-1 Monitored with INTEGRAL: Positive Correlation Between the Cyclotron Line Energy and Flux

NASA Technical Reports Server (NTRS)

Klochkov, D.; Doroshenko, V.; Santangelo, A.; Staubert, R.; Ferrigno, C.; Kretschmar, P.; Caballero, I.; Wilms, J.; Kreykenbohm, I.; Pottschmidt, I.;

Spectral lines and characteristic of temporal variations in photoionized plasmas induced with laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-11-01

Spectral lines for Kr/Ne/H2 photoionized plasma in the ultraviolet and visible (UV/Vis) wavelength ranges have been created using a laser-produced plasma (LPP) EUV source. The source is based on a double-stream gas puff target irradiated with a commercial Nd:YAG laser. The laser pulses were focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Spectral lines from photoionization in neutral Kr/Ne/H2 and up to few charged states were observed. The intense emission lines were associated with the Kr transition lines. Experimental and theoretical investigations on intensity variations for some ionic lines are presented. A decrease in the intensity with the delay time between the laser pulse and the spectrum acquisition was revealed. Electron temperature and electron density in the photoionized plasma have been estimated from the characteristic emission lines. Temperature was obtained using Boltzmann plot method, assuming that the population density of atoms and ions are considered in a local thermodynamic equilibrium (LTE). Electron density was calculated from the Stark broadening profile. The temporal evaluation of the plasma and the way of optimizing the radiation intensity of LPP EUV sources is discussed.

A Hybrid Approach for Efficient Modeling of Medium-Frequency Propagation in Coal Mines

PubMed Central

Brocker, Donovan E.; Sieber, Peter E.; Waynert, Joseph A.; Li, Jingcheng; Werner, Pingjuan L.; Werner, Douglas H.

2015-01-01

An efficient procedure for modeling medium frequency (MF) communications in coal mines is introduced. In particular, a hybrid approach is formulated and demonstrated utilizing ideal transmission line equations to model MF propagation in combination with full-wave sections used for accurate simulation of local antenna-line coupling and other near-field effects. This work confirms that the hybrid method accurately models signal propagation from a source to a load for various system geometries and material compositions, while significantly reducing computation time. With such dramatic improvement to solution times, it becomes feasible to perform large-scale optimizations with the primary motivation of improving communications in coal mines both for daily operations and emergency response. Furthermore, it is demonstrated that the hybrid approach is suitable for modeling and optimizing large communication networks in coal mines that may otherwise be intractable to simulate using traditional full-wave techniques such as moment methods or finite-element analysis. PMID:26478686

Graded meshes in bio-thermal problems with transmission-line modeling method.

PubMed

Milan, Hugo F M; Carvalho, Carlos A T; Maia, Alex S C; Gebremedhin, Kifle G

2014-10-01

In this study, the transmission-line modeling (TLM) applied to bio-thermal problems was improved by incorporating several novel computational techniques, which include application of graded meshes which resulted in 9 times faster in computational time and uses only a fraction (16%) of the computational resources used by regular meshes in analyzing heat flow through heterogeneous media. Graded meshes, unlike regular meshes, allow heat sources to be modeled in all segments of the mesh. A new boundary condition that considers thermal properties and thus resulting in a more realistic modeling of complex problems is introduced. Also, a new way of calculating an error parameter is introduced. The calculated temperatures between nodes were compared against the results obtained from the literature and agreed within less than 1% difference. It is reasonable, therefore, to conclude that the improved TLM model described herein has great potential in heat transfer of biological systems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of the TFTR neutral beam injection system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prichard, Jr., B. A.

1977-01-01

The TFTR Neutral Beam Lines are designed to inject 20 MW of 120 keV neutral deuterium atoms into the plasma. This is accomplished using 12 sources, 65 amperes each, mounted in 4 beam lines. The 120 kV sources and a prototype beam line are being developed. The implementation of these beam lines has required the development of several associated pieces of hardware. 200 kV switch tubes for the power supplies are being developed for modulation and regulation of the accelerating supplies. A 90 cm metallic seal gate valve capable of sealing against atmosphere in either direction is being developed formore » separating the torus and beam line vacuum systems. A 70 x 80 cm fast shutter valve is also being developed to limit tritium migration from the torus into the beam line. Internal to the beam line a calorimeter, ion dump and deflection magnet have been designed to handle three beams, and optical diagnostics utilizing the doppler broadening and doppler shift of light emitted from the accelerated beam are being developed. The control and monitoring of the 12 sources will be done via the TFTR computer control system (CICADA) as will other parts of the machine, and software is being developed to condition and operate the sources automatically. The prototype beam line is scheduled to begin operation in the fall of 1978 and all four production beam lines on TFTR in 1982.« less

A new X-ray spectral observation of NGC 1068

NASA Technical Reports Server (NTRS)

Marshall, F. E.; Netzer, H.; Arnaud, K. A.; Boldt, E. A.; Holt, S. S.; Jahoda, K. M.; Kelley, R.; Mushotzky, R. F.; Petre, R.; Serlemitsos, P. J.

1993-01-01

A new X-ray observation of NGC 1068, in which improved spectral resolution (R is approximately equal to 40) and broad energy range provide important new constraints on models for this galaxy, is reported. The observed X-ray continuum of NGC 1068 from 0.3 to 10 keV is well fitted as the sum of two power-law spectra with no evidence for absorption intrinsic to the source. Strong Fe K emission lines with a total equivalent width of 2700 eV were detected due to iron less ionized than Fe XX and to iron more ionized than Fe XXIII. No evidence was seen for lines due to the recombination of highly ionized oxygen with an upper limit for the O Ly-alpha emission line of 40 eV. The discovery of multiple Fe K and Fe L emission lines indicates a broad range of ionization states for this gas. The X-ray emission from the two components is modeled for various geometries using a photoionization code that calculates the temperature and ionization state of the gas. Typical model parameters are a total Compton depth of a few percent, an inner boundary of the hot component of about 1 pc, and an inner boundary of the warm component of about 20 pc.

Radiative transfer calculations of the diffuse ionized gas in disc galaxies with cosmic ray feedback

NASA Astrophysics Data System (ADS)

Vandenbroucke, Bert; Wood, Kenneth; Girichidis, Philipp; Hill, Alex S.; Peters, Thomas

2018-05-01

The large vertical scale heights of the diffuse ionized gas (DIG) in disc galaxies are challenging to model, as hydrodynamical models including only thermal feedback seem to be unable to support gas at these heights. In this paper, we use a three-dimensional Monte Carlo radiation transfer code to post-process disc simulations of the Simulating the Life-Cycle of Molecular Clouds project that include feedback by cosmic rays. We show that the more extended discs in simulations including cosmic ray feedback naturally lead to larger scale heights for the DIG which are more in line with observed scale heights. We also show that including a fiducial cosmic ray heating term in our model can help to increase the temperature as a function of disc scale height, but fails to reproduce observed DIG nitrogen and sulphur forbidden line intensities. We show that, to reproduce these line emissions, we require a heating mechanism that affects gas over a larger density range than is achieved by cosmic ray heating, which can be achieved by fine tuning the total luminosity of ionizing sources to get an appropriate ionizing spectrum as a function of scale height. This result sheds a new light on the relation between forbidden line emissions and temperature profiles for realistic DIG gas distributions.

Solar Flare Termination shock and the Synthetic Fe XXI 1354.08 Å line

NASA Astrophysics Data System (ADS)

Guo, L.; Li, G.; Reeves, K.; Raymond, J. C.

2017-12-01

Solar flares are one of the most energetic phenomena occurred in the solar system. In the standard solar flare model, a fast mode shock, which is often referred to as the flare termination shock (TS), can exist above the loop-top source of hard X-ray emissions. The existence of the termination shock has been recently related to spectral hardening of flare hard X-ray spectrum at energies > 300 keV. Observations of the Fe XXI 1354.08 Å line during solar flares by the IRIS spacecraft have found significant redshift with >100 km/s, which is consistent with a reconnection downflow. The ability to identify such a redshift by IRIS is made possible by IRIS's high time resolution, high spatial resolution, high sensitivity and cadence spectral observations. The ability to identify such a redshift by IRIS suggests that one may be able to use IRIS observations to identify flare termination shocks. Using a MHD simulation to model magnetic reconnection of a solar flare and assuming the existence of a TS in the downflow of the reconnection plasma, we model the synthetic emission of the Fe XXI 1354.08 Å line in this work. We show that the existence of the TS in the solar flare may manifest itself from the Fe XXI 1354.08 Å line.

Evidence for ultra-fast outflows in radio-quiet AGNs. I. Detection and statistical incidence of Fe K-shell absorption lines

NASA Astrophysics Data System (ADS)

Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Yaqoob, T.; Braito, V.; Dadina, M.

2010-10-01

Context. Blue-shifted Fe K absorption lines have been detected in recent years between 7 and 10 keV in the X-ray spectra of several radio-quiet AGNs. The derived blue-shifted velocities of the lines can often reach mildly relativistic values, up to 0.2-0.4c. These findings are important because they suggest the presence of a previously unknown massive and highly ionized absorbing material outflowing from their nuclei, possibly connected with accretion disk winds/outflows. Aims: The scope of the present work is to statistically quantify the parameters and incidence of the blue-shifted Fe K absorption lines through a uniform analysis on a large sample of radio-quiet AGNs. This allows us to assess their global detection significance and to overcome any possible publication bias. Methods: We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. A simple uniform model composed by an absorbed power-law plus Gaussian emission and absorption lines provided a good fit for all the data sets. We derived the absorption lines parameters and calculated their detailed detection significance making use of the classical F-test and extensive Monte Carlo simulations. Results: We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies higher than 7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3 × 10-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability <10-7. We identify the lines as Fe XXV and Fe XXVI K-shell resonant absorption. They are systematically blue-shifted, with a velocity distribution ranging from zero up to ~0.3c, with a peak and mean value at ~0.1c. We detect variability of the lines on both EWs and blue-shifted velocities among different XMM-Newton observations even on time-scales as short as a few days, possibly suggesting somewhat compact absorbers. Moreover, we find no significant correlation between the cosmological red-shifts of the sources and the lines blue-shifted velocities, ruling out any systematic contamination by local absorption. If we define ultra-fast outflows (UFOs) those highly ionized absorbers with outflow velocities higher than 104 km s-1, then the majority of the lines are consistent with being associated to UFOs and the fraction of objects with detected UFOs in the whole sample is at least ~35%. This fraction is similar for type 1 and type 2 sources. The global covering fraction of the absorbers is consequently estimated to be in the range C ˜ 0.4-0.6, thereby implying large opening angles. Conclusions: From our systematic X-ray spectral analysis on a large sample of radio-quiet AGNs we have been able to clearly assess the global veracity of the blue-shifted Fe K absorption lines at E > 7 keV and to overcome their publication bias. These lines indicate that UFOs are a rather common phenomenon observable in the central regions of these sources and they are probably the direct signature of AGN accretion disk winds/ejecta. The detailed photo-ionization modeling of these absorbers is presented in a companion paper. Appendices are only available in electronic form at http://www.aanda.org

Ion source and injection line for high intensity medical cyclotron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, XianLu, E-mail: jiaxl@ciae.ac.cn; Guan, Fengping; Yao, Hongjuan

2014-02-15

A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). An injection system based on the external H− ion source was used on CYCIAE-14 so as to provide high intensity beam, while most positron emission tomography cyclotrons adopt internal ion source. A beam intensity of 100 μA/14 MeV was extracted from the cyclotron with a small multi-cusp H− ion source (CIAE-CH-I type) and a short injection line, which the H− ion source of 3 mA/25 keV H− beam with emittance of 0.3π mm mrad and the injection line of with only 1.2 m from themore » extraction of ion source to the medial plane of the cyclotron. To increase the extracted beam intensity of the cyclotron, a new ion source (CIAE-CH-II type) of 9.1 mA was used, with maximum of 500 μA was achieved from the cyclotron. The design and test results of the ion source and injection line optimized for high intensity acceleration will be given in this paper.« less

Putting FLEXPART to REST: The Provision of Atmospheric Transport Modeling Services

NASA Astrophysics Data System (ADS)

Morton, Don; Arnold, Dèlia

2015-04-01

We are developing a RESTful set of modeling services for the FLEXPART modeling system. FLEXPART (FLEXible PARTicle dispersion model) is a Lagrangian transport and dispersion model used by a growing international community. It has been used to simulate and forecast the atmospheric transport of wildfire smoke, volcanic ash and radionuclides and may be run in backwards mode to provide information for the determination of emission sources such as nuclear emissions and greenhouse gases. This open source software is distributed in source code form, and has several compiler and library dependencies that users need to address. Although well-documented, getting it compiled, set up, running, and post-processed is often tedious, making it difficult for the inexperienced or casual user. Well-designed modeling services lower the entry barrier for scientists to perform simulations, allowing them to create and execute their models from a variety of devices and programming environments. This world of Service Oriented Architectures (SOA) has progressed to a REpresentational State Transfer (REST) paradigm, in which the pervasive and mature HTTP environment is used as a foundation for providing access to model services. With such an approach, sound software engineering practises are adhered to in order to deploy service modules exhibiting very loose coupling with the clients. In short, services are accessed and controlled through the formation of properly-constructed Uniform Resource Identifiers (URI's), processed in an HTTP environment. In this way, any client or combination of clients - whether a bash script, Python program, web GUI, or even Unix command line - that can interact with an HTTP server, can run the modeling environment. This loose coupling allows for the deployment of a variety of front ends, all accessing a common modeling backend system. Furthermore, it is generally accepted in the cloud computing community that RESTful approaches constitute a sound approach towards successful deployment of services. Through the design of a RESTful, cloud-based modeling system, we provide the ubiquitous access to FLEXPART that allows scientists to focus on modeling processes instead of tedious computational details. In this work, we describe the modeling services environment, and provide examples of access via command-line, Python programs, and web GUI interfaces.

ROSAT HRI and ASCA Observations of the Spiral Galaxy NGC 6946 and its Northeast Complex of Luminous Supernova Remnants

NASA Technical Reports Server (NTRS)

Schlegel, E.; Swank, Jean (Technical Monitor)

2001-01-01

Analysis of 80 ks ASCA (Advanced Satellite for Cosmology and Astrophysics) and 60 ks ROSAT HRI (High Resolution Image) observations of the face-on spiral galaxy NGC 6946 are presented. The ASCA image is the first observation of this galaxy above approximately 2 keV. Diffuse emission may be present in the inner approximately 4' extending to energies above approximately 2-3 keV. In the HRI data, 14 pointlike sources are detected, the brightest two being a source very close to the nucleus and a source to the northeast that corresponds to a luminous complex of interacting supernova remnants (SNRs). We detect a point source that lies approximately 30" west of the SNR complex but with a luminosity -1115 of the SNR complex. None of the point sources show evidence of strong variability; weak variability would escape our detection. The ASCA spectrum of the SNR complex shows evidence for an emission line at approximately 0.9 keV that could be either Ne IX at approximately 0.915 keV or a blend of ion stages of Fe L-shell emission if the continuum is fitted with a power law. However, a two-component, Raymond-Smith thermal spectrum with no lines gives an equally valid continuum fit and may be more physically plausible given the observed spectrum below 3 keV. Adopting this latter model, we derive a density for the SNR complex of 10-35 cm(exp -3), consistent with estimates inferred from optical emission-line ratios. The complex's extraordinary X-ray luminosity may be related more to the high density of the surrounding medium than to a small but intense interaction region where two of the complex's SNRs are apparently colliding.

A Dust-scattering Halo of 4U 1630–47 Observed with Chandra and Swift: New Constraints on the Source Distance

NASA Astrophysics Data System (ADS)

Kalemci, E.; Maccarone, T. J.; Tomsick, J. A.

2018-06-01

We have observed the Galactic black hole transient 4U 1630‑47 during the decay of its 2016 outburst with Chandra and Swift to investigate the properties of the dust-scattering halo created by the source. The scattering halo shows a structure that includes a bright ring between 80″ and 240″ surrounding the source, and a continuous distribution beyond 250″. An analysis of the 12CO J = 1–0 map and spectrum in the line of sight to the source indicates that a molecular cloud with a radial velocity of ‑79 km s‑1 (denoted MC ‑79) is the main scattering body that creates the bright ring. We found additional clouds in the line of sight, calculated their kinematic distances, and resolved the well known “near” and “far” distance ambiguity for most of the clouds. At the favored far-distance estimate of MC ‑79, the modeling of the surface brightness profile results in a distance to 4U 1630‑47 of 11.5 ± 0.3 kpc. If MC ‑79 is at the near distance, then 4U 1630‑47 is at 4.7 ± 0.3 kpc. Future Chandra, Swift, and submillimeter radio observations not only can resolve this ambiguity, but also would provide information regarding properties of dust and the distribution of all molecular clouds along the line of sight. Using the results of this study we also discuss the nature of this source and the reasons for the observation of an anomalously low soft state during the 2010 decay.

IGARSS 89: Canadian Symposium on Remote Sensing (12th) (Symposium Canadien sur la Teledetection): Quantitative Remote Sensing: An Economic Tool for the Nineties Held in Vancouver, Canada on 10-14 July 1989. Volume 2. Tuesday, July 11

DTIC Science & Technology

1989-07-14

blunder-free DEMs, the manual verification group of Ground Control Points (GCPs); (ii) and editing stage is still needed. the orbit and attitude of... control the influence (weight) of the sources and model the that each information class only had one subclass! To set non -Gaussian data. When the...clear line of infinitesimally close laminae sliding parallel to a shear line of shear; a quasi -brittle inner regime and a non -linear viscous outer

High-resolution X-ray spectroscopy of M87 with the Einstein observatory - The detection of an O VIII emission line

NASA Technical Reports Server (NTRS)

Canizares, C. R.; Clark, G. W.; Markert, T. H.; Berg, C.; Smedira, M.; Bardas, D.; Schnopper, H.; Kalata, K.

1979-01-01

The paper deals with high-resolution X-ray spectroscopy performed to study the extended source surrounding the giant elliptical galaxy, M87, in the Virgo cluster. From observations carried out with a focal plane crystal spectrometer, L-alpha emission was detected from hydrogenic oxygen (O VIII). Upper limits could be set on lines from intermediate ionization states of iron. The presence of a quantity of cooler matter surrounding M87 was revealed, which has important implications for cluster models and favors a radiatively controlled accretion mechanism.

Minimal Model of Prey Localization through the Lateral-Line System

NASA Astrophysics Data System (ADS)

Franosch, Jan-Moritz P.; Sobotka, Marion C.; Elepfandt, Andreas; van Hemmen, J. Leo

2003-10-01

The clawed frog Xenopus is an aquatic predator catching prey at night by detecting water movements caused by its prey. We present a general method, a “minimal model” based on a minimum-variance estimator, to explain prey detection through the frog's many lateral-line organs, even in case several of them are defunct. We show how waveform reconstruction allows Xenopus' neuronal system to determine both the direction and the character of the prey and even to distinguish two simultaneous wave sources. The results can be applied to many aquatic amphibians, fish, or reptiles such as crocodilians.

A Physically based Model of the Ionizing Radiation from Active Galaxies for Photoionization Modeling

NASA Astrophysics Data System (ADS)

Thomas, A. D.; Groves, B. A.; Sutherland, R. S.; Dopita, M. A.; Kewley, L. J.; Jin, C.

2016-12-01

We present a simplified model of active galactic nucleus (AGN) continuum emission designed for photoionization modeling. The new model oxaf reproduces the diversity of spectral shapes that arise in physically based models. We identify and explain degeneracies in the effects of AGN parameters on model spectral shapes, with a focus on the complete degeneracy between the black hole mass and AGN luminosity. Our reparametrized model oxaf removes these degeneracies and accepts three parameters that directly describe the output spectral shape: the energy of the peak of the accretion disk emission {E}{peak}, the photon power-law index of the non-thermal emission Γ, and the proportion of the total flux that is emitted in the non-thermal component {p}{NT}. The parameter {E}{peak} is presented as a function of the black hole mass, AGN luminosity, and “coronal radius” of the optxagnf model upon which oxaf is based. We show that the soft X-ray excess does not significantly affect photoionization modeling predictions of strong emission lines in Seyfert narrow-line regions. Despite its simplicity, oxaf accounts for opacity effects where the accretion disk is ionized because it inherits the “color correction” of optxagnf. We use a grid of mappings photoionization models with oxaf ionizing spectra to demonstrate how predicted emission-line ratios on standard optical diagnostic diagrams are sensitive to each of the three oxaf parameters. The oxaf code is publicly available in the Astrophysics Source Code Library.

40 CFR 98.80 - Definition of the source category.

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.80 Definition of the source category. The cement production source category consists of each kiln and each in-line kiln/raw mill at any portland cement manufacturing facility including alkali bypasses, and includes kilns and in-line kiln/raw...

40 CFR 98.80 - Definition of the source category.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.80 Definition of the source category. The cement production source category consists of each kiln and each in-line kiln/raw mill at any portland cement manufacturing facility including alkali bypasses, and includes kilns and in-line kiln/raw...

40 CFR 98.80 - Definition of the source category.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.80 Definition of the source category. The cement production source category consists of each kiln and each in-line kiln/raw mill at any portland cement manufacturing facility including alkali bypasses, and includes kilns and in-line kiln/raw...

Observations of a high-excitation transition of SO in galactic H II regions

NASA Astrophysics Data System (ADS)

Watt, G. D.; Millar, T. J.; White, G. J.; Harten, R. H.

1986-02-01

High-excitation observations of the 56-45 transition of SO at 251 GHz have been made. The central four arcminutes of the Orion-KL region have been mapped and a survey of 6 other galactic sources has been performed. Detailed chemical kinetic models have been utilised to investigate the chemistry of sulphur in view of recent estimates of sulphur depletion and the possibility of a gas phase carbon to oxygen ratio greater than 1. The authors find a link between the SO/SO2 and C/O ratios and that their data are consistent with the high C I abundance detected in the Orion ridge component. In the plateau source the enhanced abundances of SO and SO2 may be caused by a molecular outflow from an oxygen-rich star. In addition a previously undetected methanol line and an unidentified line appear in the Orion data.

The infrared spectrum of M8 E - Evidence for circumstellar CO

NASA Technical Reports Server (NTRS)

Larson, H. P.; Fink, U.; Hofmann, R.

1986-01-01

High-resolution spectroscopic observations of the compact infrared source M8 E are reported in the region from 3 to 5 microns. Very prominent CO absorption lines are observed in the v = 1-0 band at 4.7 microns. The velocity width and rotational temperature suggest that this CO absorption occurs in a highly excited region. The high background continuum flux level and the prominent appearance of the CO features suggest that the CO line-forming region must be in front of the dust emission region. A blister model for M8 E, which places most of the dust continuum emission behind the source, satisfies this requirement. According to this picture, the observed circumstellar CO spectrum shows a high rotational temperature and a large velocity dispersion because of the combined effects of the strong stellar wind and possible shock heating near the dust zone as the wind encounters the ambient molecular cloud.

Mapping the Solar Wind from its Source Region into the Outer Corona

NASA Technical Reports Server (NTRS)

Esser, Ruth

1997-01-01

Knowledge of the radial variation of the plasma conditions in the coronal source region of the solar wind is essential to exploring coronal heating and solar wind acceleration mechanisms. The goal of the proposal was to determine as many plasma parameters in the solar wind acceleration region and beyond as possible by coordinating different observational techniques, such as Interplanetary Scintillation Observations, spectral line intensity observations, polarization brightness measurements and X-ray observations. The inferred plasma parameters were then used to constrain solar wind models.

Sky distribution of artificial sources in the galactic belt of advanced cosmic life.

PubMed

Heidmann, J

1994-12-01

In line with the concept of the galactic belt of advanced life, we evaluate the sky distribution of detectable artificial sources, using a simple astrophysical model. The best region to search is the median band of the Milky Way in the Vulpecula-Cygnus region, together with a narrower one in Carina. Although this work was done in view of a proposal to send a SETI probe at a gravitational focus of the Sun, we recommend these sky regions particularly for the searches of the sky survey type.

Modelling supernova line profile asymmetries to determine ejecta dust masses: SN 1987A from days 714 to 3604

NASA Astrophysics Data System (ADS)

Bevan, Antonia; Barlow, M. J.

2016-02-01

The late-time optical and near-IR line profiles of many core-collapse supernovae exhibit a red-blue asymmetry as a result of greater extinction by internal dust of radiation emitted from the receding parts of the supernova ejecta. We present here a new code, DAMOCLES, that models the effects of dust on the line profiles of core-collapse supernovae in order to determine newly formed dust masses. We find that late-time dust-affected line profiles may exhibit an extended red scattering wing (as noted by Lucy et al. 1989) and that they need not be flux-biased towards the blue, although the profile peak will always be blueshifted. We have collated optical spectra of SN 1987A from a variety of archival sources and have modelled the Hα line from days 714 to 3604 and the [O I] 6300,6363 Å doublet between days 714 and 1478. Our line profile fits rule out day 714 dust masses >3 × 10-3 M⊙ for all grain types apart from pure magnesium silicates, for which no more than 0.07 M⊙ can be accommodated. Large grain radii ( ≥ 0.6 μm) are generally required to fit the line profiles even at the earlier epochs. We find that a large dust mass (≥0.1 M⊙) had formed by day 3604 and infer that the majority of the present dust mass must have formed after this epoch. Our findings agree with recent estimates from spectral energy distribution fits for the dust mass evolution of SN 1987A and support the inference that the majority of SN 1987A's dust formed many years after the initial explosion.

A SUZAKU OBSERVATION OF MCG -2-58-22: CONSTRAINING THE GEOMETRY OF THE CIRCUMNUCLEAR MATERIAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu

2011-05-01

We have analyzed a long-look Suzaku observation of the active galactic nucleus MCG -2-58-22, a type 1.5 Seyfert with very little X-ray absorption in the line of sight and prominent features arising from reflection off circumnuclear material: the Fe line and Compton reflection hump. We place tight constraints on the power-law photon index ({Gamma} = 1.80 {+-} 0.02), the Compton reflection strength (R = 0.69 {+-} 0.05), and the Fe K emission line energy centroid and width (E = 6.40 {+-} 0.02 keV, v{sub FWHM} < 7100 km s{sup -1}). We find no significant evidence either for emission from stronglymore » ionized Fe, or for a strong, relativistically broadened Fe line, indicating that perhaps there is no radiatively efficient accretion disk very close in to the central black hole. In addition, we test a new self-consistent physical model from Murphy and Yaqoob, the 'MYTORUS' model, consisting of a donut-shaped torus of material surrounding the central illuminating source and producing both the Compton hump and the Fe K line emission. From the application of this model we find that the observed spectrum is consistent with a Compton-thick torus of material (column density N{sub H} = 3.6{sup +1.3}{sub -0.8} x 10{sup 24} cm{sup -2}) lying outside of the line of sight to the nucleus, leaving it bare of X-ray absorption in excess of the Galactic column. We calculate that this material is sufficient to produce all of the Fe line flux without the need for any flux contribution from additional Compton-thin circumnuclear material.« less

Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results

NASA Technical Reports Server (NTRS)

Hughes, Christopher E.; Jeracki, Robert J.; Woodward, Richard P.; Miller, Christopher J.

2005-01-01

The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.

Development and evaluation of the R-LINE model algorithms to account for chemical transformation in the near-road environment

EPA Science Inventory

With increased urbanization, there is increased mobility leading to higher amount of traffic-related activity on a global scale. Most NOx from combustion sources (about 90–95%) are emitted as NO, which is then readily converted to NO2 in the ambient air, while the remainder...

75 FR 47190 - Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model EMB-135...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-05

... kind. EMBRAER also states that the rod breakage has not been shown to cause leakage of APU oil in the gearbox, or leakage of the fuel lines in the compartment. EMBRAER states both ignition sources and... detector becomes inoperative. EMBRAER also states that in the event of fire detection failure, [[Page 47191...

Boundary Layer Model for Air Pollutant Concentrations Due to Highway Traffic

ERIC Educational Resources Information Center

Ragland, Kenneth W.; Peirce, J. Jeffrey

1975-01-01

A numerical solution of the three-dimensional steady-state diffusion equation for a finite width line source is presented. The wind speed and eddy diffusivity as a function of height above the roadway are obtained. Normalized ground level and elevated concentrations near a highway are obtained for winds perpendicular, parallel, and at 45 degrees.…

The Gravity Wave Response Above Deep Convection in a Squall Line Simulation

NASA Technical Reports Server (NTRS)

Alexander, M. J.; Holton, J. R.; Durran, D. R.

1995-01-01

High-frequency gravity waves generated by convective storms likely play an important role in the general circulation of the middle atmosphere. Yet little is known about waves from this source. This work utilizes a fully compressible, nonlinear, numerical, two-dimensional simulation of a midlatitude squall line to study vertically propagating waves generated by deep convection. The model includes a deep stratosphere layer with high enough resolution to characterize the wave motions at these altitudes. A spectral analysis of the stratospheric waves provides an understanding of the necessary characteristics of the spectrum for future studies of their effects on the middle atmosphere in realistic mean wind scenarios. The wave spectrum also displays specific characteristics that point to the physical mechanisms within the storm responsible for their forcing. Understanding these forcing mechanisms and the properties of the storm and atmosphere that control them are crucial first steps toward developing a parameterization of waves from this source. The simulation also provides a description of some observable signatures of convectively generated waves, which may promote observational verification of these results and help tie any such observations to their convective source.

Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight

DOE Office of Scientific and Technical Information (OSTI.GOV)

Busti, V.C.; Clarkson, C.; Holanda, R.F.L., E-mail: vinicius.busti@uct.ac.za, E-mail: holanda@uepb.edu.br, E-mail: chris.clarkson@uct.ac.za

2013-11-01

Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales — which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbationmore » theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the inferred density parameters, but also introduces a bias in the posterior value.« less

Sonar Imaging of Elastic Fluid-Filled Cylindrical Shells.

NASA Astrophysics Data System (ADS)

Dodd, Stirling Scott

1995-01-01

Previously a method of describing spherical acoustic waves in cylindrical coordinates was applied to the problem of point source scattering by an elastic infinite fluid -filled cylindrical shell (S. Dodd and C. Loeffler, J. Acoust. Soc. Am. 97, 3284(A) (1995)). This method is applied to numerically model monostatic oblique incidence scattering from a truncated cylinder by a narrow-beam high-frequency imaging sonar. The narrow beam solution results from integrating the point source solution over the spatial extent of a line source and line receiver. The cylinder truncation is treated by the method of images, and assumes that the reflection coefficient at the truncation is unity. The scattering form functions, calculated using this method, are applied as filters to a narrow bandwidth, high ka pulse to find the time domain scattering response. The time domain pulses are further processed and displayed in the form of a sonar image. These images compare favorably to experimentally obtained images (G. Kaduchak and C. Loeffler, J. Acoust. Soc. Am. 97, 3289(A) (1995)). The impact of the s_{ rm o} and a_{rm o} Lamb waves is vividly apparent in the images.

How effectively do horizontal and vertical response strategies of long-finned pilot whales reduce sound exposure from naval sonar?

PubMed

Wensveen, Paul J; von Benda-Beckmann, Alexander M; Ainslie, Michael A; Lam, Frans-Peter A; Kvadsheim, Petter H; Tyack, Peter L; Miller, Patrick J O

2015-05-01

The behaviour of a marine mammal near a noise source can modulate the sound exposure it receives. We demonstrate that two long-finned pilot whales both surfaced in synchrony with consecutive arrivals of multiple sonar pulses. We then assess the effect of surfacing and other behavioural response strategies on the received cumulative sound exposure levels and maximum sound pressure levels (SPLs) by modelling realistic spatiotemporal interactions of a pilot whale with an approaching source. Under the propagation conditions of our model, some response strategies observed in the wild were effective in reducing received levels (e.g. movement perpendicular to the source's line of approach), but others were not (e.g. switching from deep to shallow diving; synchronous surfacing after maximum SPLs). Our study exemplifies how simulations of source-whale interactions guided by detailed observational data can improve our understanding about motivations behind behaviour responses observed in the wild (e.g., reducing sound exposure, prey movement). Copyright © 2015 Elsevier Ltd. All rights reserved.

Zebrafish hair cell mechanics and physiology through the lens of noise-induced hair cell death

NASA Astrophysics Data System (ADS)

Coffin, Allison B.; Xu, Jie; Uribe, Phillip M.

2018-05-01

Hair cells are exquisitely sensitive to auditory stimuli, but also to damage from a variety of sources including noise trauma and ototoxic drugs. Mammals cannot regenerate cochlear hair cells, while non-mammalian vertebrates exhibit robust regenerative capacity. Our research group uses the lateral line system of larval zebrafish to explore the mechanisms underlying hair cell damage, identify protective therapies, and determine molecular drivers of innate regeneration. The lateral line system contains externally located sensory organs called neuromasts, each composed of ˜8-20 hair cells. Lateral line hair cells are homologous to vertebrate inner ear hair cells and share similar susceptibility to ototoxic damage. In the last decade, the lateral line has emerged as a powerful model system for understanding hair cell death mechanisms and for identifying novel protective compounds. Here we demonstrate that the lateral line is a tractable model for noise-induced hair cell death. We have developed a novel noise damage system capable of inducing over 50% loss of lateral line hair cells, with hair cell death occurring in a dose- and time-dependent manner. Cell death is greatest 72 hours post-exposure. However, early signs of hair cell damage, including changes in membrane integrity and reduced mechanotransduction, are apparent within hours of noise exposure. These features, early signs of damage followed by delayed hair cell death, are consistent with mammalian data, suggesting that noise acts similarly on zebrafish and mammalian hair cells. In our future work we will use our new model system to investigate noise damage events in real time, and to develop protective therapies for future translational research.

Spectral features of tidal disruption candidates and alternative origins for such transient flares

NASA Astrophysics Data System (ADS)

Saxton, Curtis J.; Perets, Hagai B.; Baskin, Alexei

2018-03-01

UV and optically selected candidates for stellar tidal disruption events (TDEs) often exhibit broad spectral features (He II emission, H α emission, or absorption lines) on a blackbody-like continuum (104 K≲ T≲ 105 K). The lines presumably emit from TDE debris or circumnuclear clouds photoionized by the flare. Line velocities however are much lower than expected from a stellar disruption by supermassive black hole (SMBH), and are somewhat faster than expected for the broad line region (BLR) clouds of a persistently active galactic nucleus (AGN). The distinctive spectral states are not strongly related to observed luminosity and velocity, nor to SMBH mass estimates. We use exhaustive photoionization modelling to map the domain of fluxes and cloud properties that yield (e.g.) an He-overbright state where a large He II(4686 Å)/H α line ratio creates an illusion of helium enrichment. Although observed line ratios occur in a plausible minority of cases, AGN-like illumination cannot reproduce the observed equivalent widths. We therefore propose to explain these properties by a light-echo photoionization model: the initial flash of a hot blackbody (detonation) excites BLR clouds, which are then seen superimposed on continuum from a later, expanded, cooled stage of the luminous source. The implied cloud mass is substellar, which may be inconsistent with a TDE. Given these and other inconsistencies with TDE models (e.g. host-galaxies distribution) we suggest to also consider alternative origins for these nuclear flares, which we briefly discuss (e.g. nuclear supernovae and starved/subluminous AGNs).